vfs: expand support for NCA reading

src/core/file_sys/fssystem/fs_i_storage.h

@@ -0,0 +1,58 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/overflow.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+class IStorage : public VfsFile {
+public:
+    virtual std::string GetName() const override {
+        return {};
+    }
+
+    virtual VirtualDir GetContainingDirectory() const override {
+        return {};
+    }
+
+    virtual bool IsWritable() const override {
+        return true;
+    }
+
+    virtual bool IsReadable() const override {
+        return true;
+    }
+
+    virtual bool Resize(size_t size) override {
+        return false;
+    }
+
+    virtual bool Rename(std::string_view name) override {
+        return false;
+    }
+
+    static inline Result CheckAccessRange(s64 offset, s64 size, s64 total_size) {
+        R_UNLESS(offset >= 0, ResultInvalidOffset);
+        R_UNLESS(size >= 0, ResultInvalidSize);
+        R_UNLESS(Common::WrappingAdd(offset, size) >= offset, ResultOutOfRange);
+        R_UNLESS(offset + size <= total_size, ResultOutOfRange);
+        R_SUCCEED();
+    }
+};
+
+class IReadOnlyStorage : public IStorage {
+public:
+    virtual bool IsWritable() const override {
+        return false;
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        return 0;
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fs_types.h

@@ -0,0 +1,46 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+
+namespace FileSys {
+
+struct Int64 {
+    u32 low;
+    u32 high;
+
+    constexpr void Set(s64 v) {
+        this->low = static_cast<u32>((v & static_cast<u64>(0x00000000FFFFFFFFULL)) >> 0);
+        this->high = static_cast<u32>((v & static_cast<u64>(0xFFFFFFFF00000000ULL)) >> 32);
+    }
+
+    constexpr s64 Get() const {
+        return (static_cast<s64>(this->high) << 32) | (static_cast<s64>(this->low));
+    }
+
+    constexpr Int64& operator=(s64 v) {
+        this->Set(v);
+        return *this;
+    }
+
+    constexpr operator s64() const {
+        return this->Get();
+    }
+};
+
+struct HashSalt {
+    static constexpr size_t Size = 32;
+
+    std::array<u8, Size> value;
+};
+static_assert(std::is_trivial_v<HashSalt>);
+static_assert(sizeof(HashSalt) == HashSalt::Size);
+
+constexpr inline size_t IntegrityMinLayerCount = 2;
+constexpr inline size_t IntegrityMaxLayerCount = 7;
+constexpr inline size_t IntegrityLayerCountSave = 5;
+constexpr inline size_t IntegrityLayerCountSaveDataMeta = 4;
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_aes_ctr_counter_extended_storage.cpp

@@ -0,0 +1,252 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_aes_ctr_counter_extended_storage.h"
+#include "core/file_sys/fssystem/fssystem_aes_ctr_storage.h"
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+#include "core/file_sys/vfs_offset.h"
+
+namespace FileSys {
+
+namespace {
+
+class SoftwareDecryptor final : public AesCtrCounterExtendedStorage::IDecryptor {
+public:
+    virtual void Decrypt(
+        u8* buf, size_t buf_size, const std::array<u8, AesCtrCounterExtendedStorage::KeySize>& key,
+        const std::array<u8, AesCtrCounterExtendedStorage::IvSize>& iv) override final;
+};
+
+} // namespace
+
+Result AesCtrCounterExtendedStorage::CreateSoftwareDecryptor(std::unique_ptr<IDecryptor>* out) {
+    std::unique_ptr<IDecryptor> decryptor = std::make_unique<SoftwareDecryptor>();
+    R_UNLESS(decryptor != nullptr, ResultAllocationMemoryFailedInAesCtrCounterExtendedStorageA);
+    *out = std::move(decryptor);
+    R_SUCCEED();
+}
+
+Result AesCtrCounterExtendedStorage::Initialize(const void* key, size_t key_size, u32 secure_value,
+                                                VirtualFile data_storage,
+                                                VirtualFile table_storage) {
+    // Read and verify the bucket tree header.
+    BucketTree::Header header;
+    table_storage->ReadObject(std::addressof(header), 0);
+    R_TRY(header.Verify());
+
+    // Determine extents.
+    const auto node_storage_size = QueryNodeStorageSize(header.entry_count);
+    const auto entry_storage_size = QueryEntryStorageSize(header.entry_count);
+    const auto node_storage_offset = QueryHeaderStorageSize();
+    const auto entry_storage_offset = node_storage_offset + node_storage_size;
+
+    // Create a software decryptor.
+    std::unique_ptr<IDecryptor> sw_decryptor;
+    R_TRY(CreateSoftwareDecryptor(std::addressof(sw_decryptor)));
+
+    // Initialize.
+    R_RETURN(this->Initialize(
+        key, key_size, secure_value, 0, data_storage,
+        std::make_shared<OffsetVfsFile>(table_storage, node_storage_size, node_storage_offset),
+        std::make_shared<OffsetVfsFile>(table_storage, entry_storage_size, entry_storage_offset),
+        header.entry_count, std::move(sw_decryptor)));
+}
+
+Result AesCtrCounterExtendedStorage::Initialize(const void* key, size_t key_size, u32 secure_value,
+                                                s64 counter_offset, VirtualFile data_storage,
+                                                VirtualFile node_storage, VirtualFile entry_storage,
+                                                s32 entry_count,
+                                                std::unique_ptr<IDecryptor>&& decryptor) {
+    // Validate preconditions.
+    ASSERT(key != nullptr);
+    ASSERT(key_size == KeySize);
+    ASSERT(counter_offset >= 0);
+    ASSERT(decryptor != nullptr);
+
+    // Initialize the bucket tree table.
+    if (entry_count > 0) {
+        R_TRY(
+            m_table.Initialize(node_storage, entry_storage, NodeSize, sizeof(Entry), entry_count));
+    } else {
+        m_table.Initialize(NodeSize, 0);
+    }
+
+    // Set members.
+    m_data_storage = data_storage;
+    std::memcpy(m_key.data(), key, key_size);
+    m_secure_value = secure_value;
+    m_counter_offset = counter_offset;
+    m_decryptor = std::move(decryptor);
+
+    R_SUCCEED();
+}
+
+void AesCtrCounterExtendedStorage::Finalize() {
+    if (this->IsInitialized()) {
+        m_table.Finalize();
+        m_data_storage = VirtualFile();
+    }
+}
+
+Result AesCtrCounterExtendedStorage::GetEntryList(Entry* out_entries, s32* out_entry_count,
+                                                  s32 entry_count, s64 offset, s64 size) {
+    // Validate pre-conditions.
+    ASSERT(offset >= 0);
+    ASSERT(size >= 0);
+    ASSERT(this->IsInitialized());
+
+    // Clear the out count.
+    R_UNLESS(out_entry_count != nullptr, ResultNullptrArgument);
+    *out_entry_count = 0;
+
+    // Succeed if there's no range.
+    R_SUCCEED_IF(size == 0);
+
+    // If we have an output array, we need it to be non-null.
+    R_UNLESS(out_entries != nullptr || entry_count == 0, ResultNullptrArgument);
+
+    // Check that our range is valid.
+    BucketTree::Offsets table_offsets;
+    R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+    R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    R_TRY(m_table.Find(std::addressof(visitor), offset));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetOffset();
+        R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                 ResultInvalidAesCtrCounterExtendedEntryOffset);
+    }
+
+    // Prepare to loop over entries.
+    const auto end_offset = offset + static_cast<s64>(size);
+    s32 count = 0;
+
+    auto cur_entry = *visitor.Get<Entry>();
+    while (cur_entry.GetOffset() < end_offset) {
+        // Try to write the entry to the out list
+        if (entry_count != 0) {
+            if (count >= entry_count) {
+                break;
+            }
+            std::memcpy(out_entries + count, std::addressof(cur_entry), sizeof(Entry));
+        }
+
+        count++;
+
+        // Advance.
+        if (visitor.CanMoveNext()) {
+            R_TRY(visitor.MoveNext());
+            cur_entry = *visitor.Get<Entry>();
+        } else {
+            break;
+        }
+    }
+
+    // Write the output count.
+    *out_entry_count = count;
+    R_SUCCEED();
+}
+
+size_t AesCtrCounterExtendedStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Validate preconditions.
+    ASSERT(offset >= 0);
+    ASSERT(this->IsInitialized());
+
+    // Allow zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+    ASSERT(Common::IsAligned(offset, BlockSize));
+    ASSERT(Common::IsAligned(size, BlockSize));
+
+    BucketTree::Offsets table_offsets;
+    ASSERT(R_SUCCEEDED(m_table.GetOffsets(std::addressof(table_offsets))));
+
+    ASSERT(table_offsets.IsInclude(offset, size));
+
+    // Read the data.
+    m_data_storage->Read(buffer, size, offset);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    ASSERT(R_SUCCEEDED(m_table.Find(std::addressof(visitor), offset)));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetOffset();
+        ASSERT(Common::IsAligned(entry_offset, BlockSize));
+        ASSERT(0 <= entry_offset && table_offsets.IsInclude(entry_offset));
+    }
+
+    // Prepare to read in chunks.
+    u8* cur_data = static_cast<u8*>(buffer);
+    auto cur_offset = offset;
+    const auto end_offset = offset + static_cast<s64>(size);
+
+    while (cur_offset < end_offset) {
+        // Get the current entry.
+        const auto cur_entry = *visitor.Get<Entry>();
+
+        // Get and validate the entry's offset.
+        const auto cur_entry_offset = cur_entry.GetOffset();
+        ASSERT(static_cast<size_t>(cur_entry_offset) <= cur_offset);
+
+        // Get and validate the next entry offset.
+        s64 next_entry_offset;
+        if (visitor.CanMoveNext()) {
+            ASSERT(R_SUCCEEDED(visitor.MoveNext()));
+            next_entry_offset = visitor.Get<Entry>()->GetOffset();
+            ASSERT(table_offsets.IsInclude(next_entry_offset));
+        } else {
+            next_entry_offset = table_offsets.end_offset;
+        }
+        ASSERT(Common::IsAligned(next_entry_offset, BlockSize));
+        ASSERT(cur_offset < static_cast<size_t>(next_entry_offset));
+
+        // Get the offset of the entry in the data we read.
+        const auto data_offset = cur_offset - cur_entry_offset;
+        const auto data_size = (next_entry_offset - cur_entry_offset) - data_offset;
+        ASSERT(data_size > 0);
+
+        // Determine how much is left.
+        const auto remaining_size = end_offset - cur_offset;
+        const auto cur_size = static_cast<size_t>(std::min(remaining_size, data_size));
+        ASSERT(cur_size <= size);
+
+        // If necessary, perform decryption.
+        if (cur_entry.encryption_value == Entry::Encryption::Encrypted) {
+            // Make the CTR for the data we're decrypting.
+            const auto counter_offset = m_counter_offset + cur_entry_offset + data_offset;
+            NcaAesCtrUpperIv upper_iv = {
+                .part = {.generation = static_cast<u32>(cur_entry.generation),
+                         .secure_value = m_secure_value}};
+
+            std::array<u8, IvSize> iv;
+            AesCtrStorage::MakeIv(iv.data(), IvSize, upper_iv.value, counter_offset);
+
+            // Decrypt.
+            m_decryptor->Decrypt(cur_data, cur_size, m_key, iv);
+        }
+
+        // Advance.
+        cur_data += cur_size;
+        cur_offset += cur_size;
+    }
+
+    return size;
+}
+
+void SoftwareDecryptor::Decrypt(u8* buf, size_t buf_size,
+                                const std::array<u8, AesCtrCounterExtendedStorage::KeySize>& key,
+                                const std::array<u8, AesCtrCounterExtendedStorage::IvSize>& iv) {
+    Core::Crypto::AESCipher<Core::Crypto::Key128, AesCtrCounterExtendedStorage::KeySize> cipher(
+        key, Core::Crypto::Mode::CTR);
+    cipher.SetIV(iv);
+    cipher.Transcode(buf, buf_size, buf, Core::Crypto::Op::Decrypt);
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_aes_ctr_counter_extended_storage.h

@@ -0,0 +1,114 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+
+#include "common/literals.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+class AesCtrCounterExtendedStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(AesCtrCounterExtendedStorage);
+    YUZU_NON_MOVEABLE(AesCtrCounterExtendedStorage);
+
+public:
+    static constexpr size_t BlockSize = 0x10;
+    static constexpr size_t KeySize = 0x10;
+    static constexpr size_t IvSize = 0x10;
+    static constexpr size_t NodeSize = 16_KiB;
+
+    class IDecryptor {
+    public:
+        virtual ~IDecryptor() {}
+        virtual void Decrypt(u8* buf, size_t buf_size, const std::array<u8, KeySize>& key,
+                             const std::array<u8, IvSize>& iv) = 0;
+    };
+
+    struct Entry {
+        enum class Encryption : u8 {
+            Encrypted = 0,
+            NotEncrypted = 1,
+        };
+
+        std::array<u8, sizeof(s64)> offset;
+        Encryption encryption_value;
+        std::array<u8, 3> reserved;
+        s32 generation;
+
+        void SetOffset(s64 value) {
+            std::memcpy(this->offset.data(), std::addressof(value), sizeof(s64));
+        }
+
+        s64 GetOffset() const {
+            s64 value;
+            std::memcpy(std::addressof(value), this->offset.data(), sizeof(s64));
+            return value;
+        }
+    };
+    static_assert(sizeof(Entry) == 0x10);
+    static_assert(alignof(Entry) == 4);
+    static_assert(std::is_trivial_v<Entry>);
+
+public:
+    static constexpr s64 QueryHeaderStorageSize() {
+        return BucketTree::QueryHeaderStorageSize();
+    }
+
+    static constexpr s64 QueryNodeStorageSize(s32 entry_count) {
+        return BucketTree::QueryNodeStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(s32 entry_count) {
+        return BucketTree::QueryEntryStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static Result CreateSoftwareDecryptor(std::unique_ptr<IDecryptor>* out);
+
+private:
+    mutable BucketTree m_table;
+    VirtualFile m_data_storage;
+    std::array<u8, KeySize> m_key;
+    u32 m_secure_value;
+    s64 m_counter_offset;
+    std::unique_ptr<IDecryptor> m_decryptor;
+
+public:
+    AesCtrCounterExtendedStorage()
+        : m_table(), m_data_storage(), m_secure_value(), m_counter_offset(), m_decryptor() {}
+    virtual ~AesCtrCounterExtendedStorage() {
+        this->Finalize();
+    }
+
+    Result Initialize(const void* key, size_t key_size, u32 secure_value, s64 counter_offset,
+                      VirtualFile data_storage, VirtualFile node_storage, VirtualFile entry_storage,
+                      s32 entry_count, std::unique_ptr<IDecryptor>&& decryptor);
+    void Finalize();
+
+    bool IsInitialized() const {
+        return m_table.IsInitialized();
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+
+    virtual size_t GetSize() const override {
+        BucketTree::Offsets offsets;
+        ASSERT(R_SUCCEEDED(m_table.GetOffsets(std::addressof(offsets))));
+
+        return offsets.end_offset;
+    }
+
+    Result GetEntryList(Entry* out_entries, s32* out_entry_count, s32 entry_count, s64 offset,
+                        s64 size);
+
+private:
+    Result Initialize(const void* key, size_t key_size, u32 secure_value, VirtualFile data_storage,
+                      VirtualFile table_storage);
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_aes_ctr_storage.cpp

@@ -0,0 +1,129 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "common/swap.h"
+#include "core/file_sys/fssystem/fssystem_aes_ctr_storage.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+#include "core/file_sys/fssystem/fssystem_utility.h"
+
+namespace FileSys {
+
+void AesCtrStorage::MakeIv(void* dst, size_t dst_size, u64 upper, s64 offset) {
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size == IvSize);
+    ASSERT(offset >= 0);
+
+    const uintptr_t out_addr = reinterpret_cast<uintptr_t>(dst);
+
+    *reinterpret_cast<u64_be*>(out_addr + 0) = upper;
+    *reinterpret_cast<s64_be*>(out_addr + sizeof(u64)) = static_cast<s64>(offset / BlockSize);
+}
+
+AesCtrStorage::AesCtrStorage(VirtualFile base, const void* key, size_t key_size, const void* iv,
+                             size_t iv_size)
+    : m_base_storage(std::move(base)) {
+    ASSERT(m_base_storage != nullptr);
+    ASSERT(key != nullptr);
+    ASSERT(iv != nullptr);
+    ASSERT(key_size == KeySize);
+    ASSERT(iv_size == IvSize);
+
+    std::memcpy(m_key.data(), key, KeySize);
+    std::memcpy(m_iv.data(), iv, IvSize);
+
+    m_cipher.emplace(m_key, Core::Crypto::Mode::CTR);
+}
+
+size_t AesCtrStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Allow zero-size reads.
+    if (size == 0) {
+        return size;
+    }
+
+    // Ensure buffer is valid.
+    ASSERT(buffer != nullptr);
+
+    // We can only read at block aligned offsets.
+    ASSERT(Common::IsAligned(offset, BlockSize));
+    ASSERT(Common::IsAligned(size, BlockSize));
+
+    // Read the data.
+    m_base_storage->Read(buffer, size, offset);
+
+    // Setup the counter.
+    std::array<u8, IvSize> ctr;
+    std::memcpy(ctr.data(), m_iv.data(), IvSize);
+    AddCounter(ctr.data(), IvSize, offset / BlockSize);
+
+    // Decrypt.
+    m_cipher->SetIV(ctr);
+    m_cipher->Transcode(buffer, size, buffer, Core::Crypto::Op::Decrypt);
+
+    return size;
+}
+
+size_t AesCtrStorage::Write(const u8* buffer, size_t size, size_t offset) {
+    // Allow zero-size writes.
+    if (size == 0) {
+        return size;
+    }
+
+    // Ensure buffer is valid.
+    ASSERT(buffer != nullptr);
+
+    // We can only write at block aligned offsets.
+    ASSERT(Common::IsAligned(offset, BlockSize));
+    ASSERT(Common::IsAligned(size, BlockSize));
+
+    // Get a pooled buffer.
+    PooledBuffer pooled_buffer;
+    const bool use_work_buffer = true;
+    if (use_work_buffer) {
+        pooled_buffer.Allocate(size, BlockSize);
+    }
+
+    // Setup the counter.
+    std::array<u8, IvSize> ctr;
+    std::memcpy(ctr.data(), m_iv.data(), IvSize);
+    AddCounter(ctr.data(), IvSize, offset / BlockSize);
+
+    // Loop until all data is written.
+    size_t remaining = size;
+    s64 cur_offset = 0;
+    while (remaining > 0) {
+        // Determine data we're writing and where.
+        const size_t write_size =
+            use_work_buffer ? std::min(pooled_buffer.GetSize(), remaining) : remaining;
+
+        void* write_buf;
+        if (use_work_buffer) {
+            write_buf = pooled_buffer.GetBuffer();
+        } else {
+            write_buf = const_cast<u8*>(buffer);
+        }
+
+        // Encrypt the data.
+        m_cipher->SetIV(ctr);
+        m_cipher->Transcode(buffer, write_size, reinterpret_cast<u8*>(write_buf),
+                            Core::Crypto::Op::Encrypt);
+
+        // Write the encrypted data.
+        m_base_storage->Write(reinterpret_cast<u8*>(write_buf), write_size, offset + cur_offset);
+
+        // Advance.
+        cur_offset += write_size;
+        remaining -= write_size;
+        if (remaining > 0) {
+            AddCounter(ctr.data(), IvSize, write_size / BlockSize);
+        }
+    }
+
+    return size;
+}
+
+size_t AesCtrStorage::GetSize() const {
+    return m_base_storage->GetSize();
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_aes_ctr_storage.h

@@ -0,0 +1,43 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+
+#include "core/crypto/aes_util.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+class AesCtrStorage : public IStorage {
+    YUZU_NON_COPYABLE(AesCtrStorage);
+    YUZU_NON_MOVEABLE(AesCtrStorage);
+
+public:
+    static constexpr size_t BlockSize = 0x10;
+    static constexpr size_t KeySize = 0x10;
+    static constexpr size_t IvSize = 0x10;
+
+private:
+    VirtualFile m_base_storage;
+    std::array<u8, KeySize> m_key;
+    std::array<u8, IvSize> m_iv;
+    mutable std::optional<Core::Crypto::AESCipher<Core::Crypto::Key128>> m_cipher;
+
+public:
+    static void MakeIv(void* dst, size_t dst_size, u64 upper, s64 offset);
+
+public:
+    AesCtrStorage(VirtualFile base, const void* key, size_t key_size, const void* iv,
+                  size_t iv_size);
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override;
+    virtual size_t GetSize() const override;
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_aes_xts_storage.cpp

@@ -0,0 +1,112 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "common/swap.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_aes_xts_storage.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+#include "core/file_sys/fssystem/fssystem_utility.h"
+
+namespace FileSys {
+
+void AesXtsStorage::MakeAesXtsIv(void* dst, size_t dst_size, s64 offset, size_t block_size) {
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size == IvSize);
+    ASSERT(offset >= 0);
+
+    const uintptr_t out_addr = reinterpret_cast<uintptr_t>(dst);
+
+    *reinterpret_cast<s64_be*>(out_addr + sizeof(s64)) = offset / block_size;
+}
+
+AesXtsStorage::AesXtsStorage(VirtualFile base, const void* key1, const void* key2, size_t key_size,
+                             const void* iv, size_t iv_size, size_t block_size)
+    : m_base_storage(std::move(base)), m_block_size(block_size), m_mutex() {
+    ASSERT(m_base_storage != nullptr);
+    ASSERT(key1 != nullptr);
+    ASSERT(key2 != nullptr);
+    ASSERT(iv != nullptr);
+    ASSERT(key_size == KeySize);
+    ASSERT(iv_size == IvSize);
+    ASSERT(Common::IsAligned(m_block_size, AesBlockSize));
+
+    std::memcpy(m_key.data() + 0, key1, KeySize);
+    std::memcpy(m_key.data() + 0x10, key2, KeySize);
+    std::memcpy(m_iv.data(), iv, IvSize);
+
+    m_cipher.emplace(m_key, Core::Crypto::Mode::XTS);
+}
+
+size_t AesXtsStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Allow zero-size reads.
+    if (size == 0) {
+        return size;
+    }
+
+    // Ensure buffer is valid.
+    ASSERT(buffer != nullptr);
+
+    // We can only read at block aligned offsets.
+    ASSERT(Common::IsAligned(offset, AesBlockSize));
+    ASSERT(Common::IsAligned(size, AesBlockSize));
+
+    // Read the data.
+    m_base_storage->Read(buffer, size, offset);
+
+    // Setup the counter.
+    std::array<u8, IvSize> ctr;
+    std::memcpy(ctr.data(), m_iv.data(), IvSize);
+    AddCounter(ctr.data(), IvSize, offset / m_block_size);
+
+    // Handle any unaligned data before the start.
+    size_t processed_size = 0;
+    if ((offset % m_block_size) != 0) {
+        // Determine the size of the pre-data read.
+        const size_t skip_size =
+            static_cast<size_t>(offset - Common::AlignDown(offset, m_block_size));
+        const size_t data_size = std::min(size, m_block_size - skip_size);
+
+        // Decrypt into a pooled buffer.
+        {
+            PooledBuffer tmp_buf(m_block_size, m_block_size);
+            ASSERT(tmp_buf.GetSize() >= m_block_size);
+
+            std::memset(tmp_buf.GetBuffer(), 0, skip_size);
+            std::memcpy(tmp_buf.GetBuffer() + skip_size, buffer, data_size);
+
+            m_cipher->SetIV(ctr);
+            m_cipher->Transcode(tmp_buf.GetBuffer(), m_block_size, tmp_buf.GetBuffer(),
+                                Core::Crypto::Op::Decrypt);
+
+            std::memcpy(buffer, tmp_buf.GetBuffer() + skip_size, data_size);
+        }
+
+        AddCounter(ctr.data(), IvSize, 1);
+        processed_size += data_size;
+        ASSERT(processed_size == std::min(size, m_block_size - skip_size));
+    }
+
+    // Decrypt aligned chunks.
+    char* cur = reinterpret_cast<char*>(buffer) + processed_size;
+    size_t remaining = size - processed_size;
+    while (remaining > 0) {
+        const size_t cur_size = std::min(m_block_size, remaining);
+
+        m_cipher->SetIV(ctr);
+        m_cipher->Transcode(cur, cur_size, cur, Core::Crypto::Op::Decrypt);
+
+        remaining -= cur_size;
+        cur += cur_size;
+
+        AddCounter(ctr.data(), IvSize, 1);
+    }
+
+    return size;
+}
+
+size_t AesXtsStorage::GetSize() const {
+    return m_base_storage->GetSize();
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_aes_xts_storage.h

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+
+#include "core/crypto/aes_util.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class AesXtsStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(AesXtsStorage);
+    YUZU_NON_MOVEABLE(AesXtsStorage);
+
+public:
+    static constexpr size_t AesBlockSize = 0x10;
+    static constexpr size_t KeySize = 0x20;
+    static constexpr size_t IvSize = 0x10;
+
+private:
+    VirtualFile m_base_storage;
+    std::array<u8, KeySize> m_key;
+    std::array<u8, IvSize> m_iv;
+    const size_t m_block_size;
+    std::mutex m_mutex;
+    mutable std::optional<Core::Crypto::AESCipher<Core::Crypto::Key256>> m_cipher;
+
+public:
+    static void MakeAesXtsIv(void* dst, size_t dst_size, s64 offset, size_t block_size);
+
+public:
+    AesXtsStorage(VirtualFile base, const void* key1, const void* key2, size_t key_size,
+                  const void* iv, size_t iv_size, size_t block_size);
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t GetSize() const override;
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_alignment_matching_storage.h

@@ -0,0 +1,146 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/alignment.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_alignment_matching_storage_impl.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+template <size_t DataAlign_, size_t BufferAlign_>
+class AlignmentMatchingStorage : public IStorage {
+    YUZU_NON_COPYABLE(AlignmentMatchingStorage);
+    YUZU_NON_MOVEABLE(AlignmentMatchingStorage);
+
+public:
+    static constexpr size_t DataAlign = DataAlign_;
+    static constexpr size_t BufferAlign = BufferAlign_;
+
+    static constexpr size_t DataAlignMax = 0x200;
+    static_assert(DataAlign <= DataAlignMax);
+    static_assert(Common::IsPowerOfTwo(DataAlign));
+    static_assert(Common::IsPowerOfTwo(BufferAlign));
+
+private:
+    VirtualFile m_base_storage;
+    s64 m_base_storage_size;
+
+public:
+    explicit AlignmentMatchingStorage(VirtualFile bs) : m_base_storage(std::move(bs)) {}
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Allocate a work buffer on stack.
+        alignas(DataAlignMax) char work_buf[DataAlign];
+
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        return AlignmentMatchingStorageImpl::Read(m_base_storage, work_buf, sizeof(work_buf),
+                                                  DataAlign, BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        // Allocate a work buffer on stack.
+        alignas(DataAlignMax) char work_buf[DataAlign];
+
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        return AlignmentMatchingStorageImpl::Write(m_base_storage, work_buf, sizeof(work_buf),
+                                                   DataAlign, BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t GetSize() const override {
+        return m_base_storage->GetSize();
+    }
+};
+
+template <size_t BufferAlign_>
+class AlignmentMatchingStoragePooledBuffer : public IStorage {
+    YUZU_NON_COPYABLE(AlignmentMatchingStoragePooledBuffer);
+    YUZU_NON_MOVEABLE(AlignmentMatchingStoragePooledBuffer);
+
+public:
+    static constexpr size_t BufferAlign = BufferAlign_;
+
+    static_assert(Common::IsPowerOfTwo(BufferAlign));
+
+private:
+    VirtualFile m_base_storage;
+    s64 m_base_storage_size;
+    size_t m_data_align;
+
+public:
+    explicit AlignmentMatchingStoragePooledBuffer(VirtualFile bs, size_t da)
+        : m_base_storage(std::move(bs)), m_data_align(da) {
+        ASSERT(Common::IsPowerOfTwo(da));
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        // Allocate a pooled buffer.
+        PooledBuffer pooled_buffer;
+        pooled_buffer.AllocateParticularlyLarge(m_data_align, m_data_align);
+
+        return AlignmentMatchingStorageImpl::Read(m_base_storage, pooled_buffer.GetBuffer(),
+                                                  pooled_buffer.GetSize(), m_data_align,
+                                                  BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        // Allocate a pooled buffer.
+        PooledBuffer pooled_buffer;
+        pooled_buffer.AllocateParticularlyLarge(m_data_align, m_data_align);
+
+        return AlignmentMatchingStorageImpl::Write(m_base_storage, pooled_buffer.GetBuffer(),
+                                                   pooled_buffer.GetSize(), m_data_align,
+                                                   BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t GetSize() const override {
+        return m_base_storage->GetSize();
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_alignment_matching_storage_impl.cpp

@@ -0,0 +1,204 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fssystem_alignment_matching_storage_impl.h"
+
+namespace FileSys {
+
+namespace {
+
+template <typename T>
+constexpr size_t GetRoundDownDifference(T x, size_t align) {
+    return static_cast<size_t>(x - Common::AlignDown(x, align));
+}
+
+template <typename T>
+constexpr size_t GetRoundUpDifference(T x, size_t align) {
+    return static_cast<size_t>(Common::AlignUp(x, align) - x);
+}
+
+template <typename T>
+size_t GetRoundUpDifference(T* x, size_t align) {
+    return GetRoundUpDifference(reinterpret_cast<uintptr_t>(x), align);
+}
+
+} // namespace
+
+size_t AlignmentMatchingStorageImpl::Read(VirtualFile base_storage, char* work_buf,
+                                          size_t work_buf_size, size_t data_alignment,
+                                          size_t buffer_alignment, s64 offset, u8* buffer,
+                                          size_t size) {
+    // Check preconditions.
+    ASSERT(work_buf_size >= data_alignment);
+
+    // Succeed if zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Determine extents.
+    u8* aligned_core_buffer;
+    s64 core_offset;
+    size_t core_size;
+    size_t buffer_gap;
+    size_t offset_gap;
+    s64 covered_offset;
+
+    const size_t offset_round_up_difference = GetRoundUpDifference(offset, data_alignment);
+    if (Common::IsAligned(reinterpret_cast<uintptr_t>(buffer) + offset_round_up_difference,
+                          buffer_alignment)) {
+        aligned_core_buffer = buffer + offset_round_up_difference;
+
+        core_offset = Common::AlignUp(offset, data_alignment);
+        core_size = (size < offset_round_up_difference)
+                        ? 0
+                        : Common::AlignDown(size - offset_round_up_difference, data_alignment);
+        buffer_gap = 0;
+        offset_gap = 0;
+
+        covered_offset = core_size > 0 ? core_offset : offset;
+    } else {
+        const size_t buffer_round_up_difference = GetRoundUpDifference(buffer, buffer_alignment);
+
+        aligned_core_buffer = buffer + buffer_round_up_difference;
+
+        core_offset = Common::AlignDown(offset, data_alignment);
+        core_size = (size < buffer_round_up_difference)
+                        ? 0
+                        : Common::AlignDown(size - buffer_round_up_difference, data_alignment);
+        buffer_gap = buffer_round_up_difference;
+        offset_gap = GetRoundDownDifference(offset, data_alignment);
+
+        covered_offset = offset;
+    }
+
+    // Read the core portion.
+    if (core_size > 0) {
+        base_storage->Read(aligned_core_buffer, core_size, core_offset);
+
+        if (offset_gap != 0 || buffer_gap != 0) {
+            std::memmove(aligned_core_buffer - buffer_gap, aligned_core_buffer + offset_gap,
+                         core_size - offset_gap);
+            core_size -= offset_gap;
+        }
+    }
+
+    // Handle the head portion.
+    if (offset < covered_offset) {
+        const s64 head_offset = Common::AlignDown(offset, data_alignment);
+        const size_t head_size = static_cast<size_t>(covered_offset - offset);
+
+        ASSERT(GetRoundDownDifference(offset, data_alignment) + head_size <= work_buf_size);
+
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, head_offset);
+        std::memcpy(buffer, work_buf + GetRoundDownDifference(offset, data_alignment), head_size);
+    }
+
+    // Handle the tail portion.
+    s64 tail_offset = covered_offset + core_size;
+    size_t remaining_tail_size = static_cast<size_t>((offset + size) - tail_offset);
+    while (remaining_tail_size > 0) {
+        const auto aligned_tail_offset = Common::AlignDown(tail_offset, data_alignment);
+        const auto cur_size =
+            std::min(static_cast<size_t>(aligned_tail_offset + data_alignment - tail_offset),
+                     remaining_tail_size);
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, aligned_tail_offset);
+
+        ASSERT((tail_offset - offset) + cur_size <= size);
+        ASSERT((tail_offset - aligned_tail_offset) + cur_size <= data_alignment);
+        std::memcpy(reinterpret_cast<char*>(buffer) + (tail_offset - offset),
+                    work_buf + (tail_offset - aligned_tail_offset), cur_size);
+
+        remaining_tail_size -= cur_size;
+        tail_offset += cur_size;
+    }
+
+    return size;
+}
+
+size_t AlignmentMatchingStorageImpl::Write(VirtualFile base_storage, char* work_buf,
+                                           size_t work_buf_size, size_t data_alignment,
+                                           size_t buffer_alignment, s64 offset, const u8* buffer,
+                                           size_t size) {
+    // Check preconditions.
+    ASSERT(work_buf_size >= data_alignment);
+
+    // Succeed if zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Determine extents.
+    const u8* aligned_core_buffer;
+    s64 core_offset;
+    size_t core_size;
+    s64 covered_offset;
+
+    const size_t offset_round_up_difference = GetRoundUpDifference(offset, data_alignment);
+    if (Common::IsAligned(reinterpret_cast<uintptr_t>(buffer) + offset_round_up_difference,
+                          buffer_alignment)) {
+        aligned_core_buffer = buffer + offset_round_up_difference;
+
+        core_offset = Common::AlignUp(offset, data_alignment);
+        core_size = (size < offset_round_up_difference)
+                        ? 0
+                        : Common::AlignDown(size - offset_round_up_difference, data_alignment);
+
+        covered_offset = core_size > 0 ? core_offset : offset;
+    } else {
+        aligned_core_buffer = nullptr;
+
+        core_offset = Common::AlignDown(offset, data_alignment);
+        core_size = 0;
+
+        covered_offset = offset;
+    }
+
+    // Write the core portion.
+    if (core_size > 0) {
+        base_storage->Write(aligned_core_buffer, core_size, core_offset);
+    }
+
+    // Handle the head portion.
+    if (offset < covered_offset) {
+        const s64 head_offset = Common::AlignDown(offset, data_alignment);
+        const size_t head_size = static_cast<size_t>(covered_offset - offset);
+
+        ASSERT((offset - head_offset) + head_size <= data_alignment);
+
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, head_offset);
+        std::memcpy(work_buf + (offset - head_offset), buffer, head_size);
+        base_storage->Write(reinterpret_cast<u8*>(work_buf), data_alignment, head_offset);
+    }
+
+    // Handle the tail portion.
+    s64 tail_offset = covered_offset + core_size;
+    size_t remaining_tail_size = static_cast<size_t>((offset + size) - tail_offset);
+    while (remaining_tail_size > 0) {
+        ASSERT(static_cast<size_t>(tail_offset - offset) < size);
+
+        const auto aligned_tail_offset = Common::AlignDown(tail_offset, data_alignment);
+        const auto cur_size =
+            std::min(static_cast<size_t>(aligned_tail_offset + data_alignment - tail_offset),
+                     remaining_tail_size);
+
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, aligned_tail_offset);
+        std::memcpy(work_buf + GetRoundDownDifference(tail_offset, data_alignment),
+                    buffer + (tail_offset - offset), cur_size);
+        base_storage->Write(reinterpret_cast<u8*>(work_buf), data_alignment, aligned_tail_offset);
+
+        remaining_tail_size -= cur_size;
+        tail_offset += cur_size;
+    }
+
+    return size;
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_alignment_matching_storage_impl.h

@@ -0,0 +1,21 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class AlignmentMatchingStorageImpl {
+public:
+    static size_t Read(VirtualFile base_storage, char* work_buf, size_t work_buf_size,
+                       size_t data_alignment, size_t buffer_alignment, s64 offset, u8* buffer,
+                       size_t size);
+    static size_t Write(VirtualFile base_storage, char* work_buf, size_t work_buf_size,
+                        size_t data_alignment, size_t buffer_alignment, s64 offset,
+                        const u8* buffer, size_t size);
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_bucket_tree.cpp

@@ -0,0 +1,598 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree_utils.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+namespace {
+
+using Node = impl::BucketTreeNode<const s64*>;
+static_assert(sizeof(Node) == sizeof(BucketTree::NodeHeader));
+static_assert(std::is_trivial_v<Node>);
+
+constexpr inline s32 NodeHeaderSize = sizeof(BucketTree::NodeHeader);
+
+class StorageNode {
+private:
+    class Offset {
+    public:
+        using difference_type = s64;
+
+    private:
+        s64 m_offset;
+        s32 m_stride;
+
+    public:
+        constexpr Offset(s64 offset, s32 stride) : m_offset(offset), m_stride(stride) {}
+
+        constexpr Offset& operator++() {
+            m_offset += m_stride;
+            return *this;
+        }
+        constexpr Offset operator++(int) {
+            Offset ret(*this);
+            m_offset += m_stride;
+            return ret;
+        }
+
+        constexpr Offset& operator--() {
+            m_offset -= m_stride;
+            return *this;
+        }
+        constexpr Offset operator--(int) {
+            Offset ret(*this);
+            m_offset -= m_stride;
+            return ret;
+        }
+
+        constexpr difference_type operator-(const Offset& rhs) const {
+            return (m_offset - rhs.m_offset) / m_stride;
+        }
+
+        constexpr Offset operator+(difference_type ofs) const {
+            return Offset(m_offset + ofs * m_stride, m_stride);
+        }
+        constexpr Offset operator-(difference_type ofs) const {
+            return Offset(m_offset - ofs * m_stride, m_stride);
+        }
+
+        constexpr Offset& operator+=(difference_type ofs) {
+            m_offset += ofs * m_stride;
+            return *this;
+        }
+        constexpr Offset& operator-=(difference_type ofs) {
+            m_offset -= ofs * m_stride;
+            return *this;
+        }
+
+        constexpr bool operator==(const Offset& rhs) const {
+            return m_offset == rhs.m_offset;
+        }
+        constexpr bool operator!=(const Offset& rhs) const {
+            return m_offset != rhs.m_offset;
+        }
+
+        constexpr s64 Get() const {
+            return m_offset;
+        }
+    };
+
+private:
+    const Offset m_start;
+    const s32 m_count;
+    s32 m_index;
+
+public:
+    StorageNode(size_t size, s32 count)
+        : m_start(NodeHeaderSize, static_cast<s32>(size)), m_count(count), m_index(-1) {}
+    StorageNode(s64 ofs, size_t size, s32 count)
+        : m_start(NodeHeaderSize + ofs, static_cast<s32>(size)), m_count(count), m_index(-1) {}
+
+    s32 GetIndex() const {
+        return m_index;
+    }
+
+    void Find(const char* buffer, s64 virtual_address) {
+        s32 end = m_count;
+        auto pos = m_start;
+
+        while (end > 0) {
+            auto half = end / 2;
+            auto mid = pos + half;
+
+            s64 offset = 0;
+            std::memcpy(std::addressof(offset), buffer + mid.Get(), sizeof(s64));
+
+            if (offset <= virtual_address) {
+                pos = mid + 1;
+                end -= half + 1;
+            } else {
+                end = half;
+            }
+        }
+
+        m_index = static_cast<s32>(pos - m_start) - 1;
+    }
+
+    Result Find(VirtualFile storage, s64 virtual_address) {
+        s32 end = m_count;
+        auto pos = m_start;
+
+        while (end > 0) {
+            auto half = end / 2;
+            auto mid = pos + half;
+
+            s64 offset = 0;
+            storage->ReadObject(std::addressof(offset), mid.Get());
+
+            if (offset <= virtual_address) {
+                pos = mid + 1;
+                end -= half + 1;
+            } else {
+                end = half;
+            }
+        }
+
+        m_index = static_cast<s32>(pos - m_start) - 1;
+        R_SUCCEED();
+    }
+};
+
+} // namespace
+
+void BucketTree::Header::Format(s32 entry_count_) {
+    ASSERT(entry_count_ >= 0);
+
+    this->magic = Magic;
+    this->version = Version;
+    this->entry_count = entry_count_;
+    this->reserved = 0;
+}
+
+Result BucketTree::Header::Verify() const {
+    R_UNLESS(this->magic == Magic, ResultInvalidBucketTreeSignature);
+    R_UNLESS(this->entry_count >= 0, ResultInvalidBucketTreeEntryCount);
+    R_UNLESS(this->version <= Version, ResultUnsupportedVersion);
+    R_SUCCEED();
+}
+
+Result BucketTree::NodeHeader::Verify(s32 node_index, size_t node_size, size_t entry_size) const {
+    R_UNLESS(this->index == node_index, ResultInvalidBucketTreeNodeIndex);
+    R_UNLESS(entry_size != 0 && node_size >= entry_size + NodeHeaderSize, ResultInvalidSize);
+
+    const size_t max_entry_count = (node_size - NodeHeaderSize) / entry_size;
+    R_UNLESS(this->count > 0 && static_cast<size_t>(this->count) <= max_entry_count,
+             ResultInvalidBucketTreeNodeEntryCount);
+    R_UNLESS(this->offset >= 0, ResultInvalidBucketTreeNodeOffset);
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Initialize(VirtualFile node_storage, VirtualFile entry_storage, size_t node_size,
+                              size_t entry_size, s32 entry_count) {
+    // Validate preconditions.
+    ASSERT(entry_size >= sizeof(s64));
+    ASSERT(node_size >= entry_size + sizeof(NodeHeader));
+    ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+    ASSERT(Common::IsPowerOfTwo(node_size));
+    ASSERT(!this->IsInitialized());
+
+    // Ensure valid entry count.
+    R_UNLESS(entry_count > 0, ResultInvalidArgument);
+
+    // Allocate node.
+    R_UNLESS(m_node_l1.Allocate(node_size), ResultBufferAllocationFailed);
+    ON_RESULT_FAILURE {
+        m_node_l1.Free(node_size);
+    };
+
+    // Read node.
+    node_storage->Read(reinterpret_cast<u8*>(m_node_l1.Get()), node_size);
+
+    // Verify node.
+    R_TRY(m_node_l1->Verify(0, node_size, sizeof(s64)));
+
+    // Validate offsets.
+    const auto offset_count = GetOffsetCount(node_size);
+    const auto entry_set_count = GetEntrySetCount(node_size, entry_size, entry_count);
+    const auto* const node = m_node_l1.Get<Node>();
+
+    s64 start_offset;
+    if (offset_count < entry_set_count && node->GetCount() < offset_count) {
+        start_offset = *node->GetEnd();
+    } else {
+        start_offset = *node->GetBegin();
+    }
+    const auto end_offset = node->GetEndOffset();
+
+    R_UNLESS(0 <= start_offset && start_offset <= node->GetBeginOffset(),
+             ResultInvalidBucketTreeEntryOffset);
+    R_UNLESS(start_offset < end_offset, ResultInvalidBucketTreeEntryOffset);
+
+    // Set member variables.
+    m_node_storage = node_storage;
+    m_entry_storage = entry_storage;
+    m_node_size = node_size;
+    m_entry_size = entry_size;
+    m_entry_count = entry_count;
+    m_offset_count = offset_count;
+    m_entry_set_count = entry_set_count;
+
+    m_offset_cache.offsets.start_offset = start_offset;
+    m_offset_cache.offsets.end_offset = end_offset;
+    m_offset_cache.is_initialized = true;
+
+    // Cancel guard.
+    R_SUCCEED();
+}
+
+void BucketTree::Initialize(size_t node_size, s64 end_offset) {
+    ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+    ASSERT(Common::IsPowerOfTwo(node_size));
+    ASSERT(end_offset > 0);
+    ASSERT(!this->IsInitialized());
+
+    m_node_size = node_size;
+
+    m_offset_cache.offsets.start_offset = 0;
+    m_offset_cache.offsets.end_offset = end_offset;
+    m_offset_cache.is_initialized = true;
+}
+
+void BucketTree::Finalize() {
+    if (this->IsInitialized()) {
+        m_node_storage = VirtualFile();
+        m_entry_storage = VirtualFile();
+        m_node_l1.Free(m_node_size);
+        m_node_size = 0;
+        m_entry_size = 0;
+        m_entry_count = 0;
+        m_offset_count = 0;
+        m_entry_set_count = 0;
+
+        m_offset_cache.offsets.start_offset = 0;
+        m_offset_cache.offsets.end_offset = 0;
+        m_offset_cache.is_initialized = false;
+    }
+}
+
+Result BucketTree::Find(Visitor* visitor, s64 virtual_address) {
+    ASSERT(visitor != nullptr);
+    ASSERT(this->IsInitialized());
+
+    R_UNLESS(virtual_address >= 0, ResultInvalidOffset);
+    R_UNLESS(!this->IsEmpty(), ResultOutOfRange);
+
+    BucketTree::Offsets offsets;
+    R_TRY(this->GetOffsets(std::addressof(offsets)));
+
+    R_TRY(visitor->Initialize(this, offsets));
+
+    R_RETURN(visitor->Find(virtual_address));
+}
+
+Result BucketTree::InvalidateCache() {
+    // Reset our offsets.
+    m_offset_cache.is_initialized = false;
+
+    R_SUCCEED();
+}
+
+Result BucketTree::EnsureOffsetCache() {
+    // If we already have an offset cache, we're good.
+    R_SUCCEED_IF(m_offset_cache.is_initialized);
+
+    // Acquire exclusive right to edit the offset cache.
+    std::scoped_lock lk(m_offset_cache.mutex);
+
+    // Check again, to be sure.
+    R_SUCCEED_IF(m_offset_cache.is_initialized);
+
+    // Read/verify L1.
+    m_node_storage->Read(reinterpret_cast<u8*>(m_node_l1.Get()), m_node_size);
+    R_TRY(m_node_l1->Verify(0, m_node_size, sizeof(s64)));
+
+    // Get the node.
+    auto* const node = m_node_l1.Get<Node>();
+
+    s64 start_offset;
+    if (m_offset_count < m_entry_set_count && node->GetCount() < m_offset_count) {
+        start_offset = *node->GetEnd();
+    } else {
+        start_offset = *node->GetBegin();
+    }
+    const auto end_offset = node->GetEndOffset();
+
+    R_UNLESS(0 <= start_offset && start_offset <= node->GetBeginOffset(),
+             ResultInvalidBucketTreeEntryOffset);
+    R_UNLESS(start_offset < end_offset, ResultInvalidBucketTreeEntryOffset);
+
+    m_offset_cache.offsets.start_offset = start_offset;
+    m_offset_cache.offsets.end_offset = end_offset;
+    m_offset_cache.is_initialized = true;
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::Initialize(const BucketTree* tree, const BucketTree::Offsets& offsets) {
+    ASSERT(tree != nullptr);
+    ASSERT(m_tree == nullptr || m_tree == tree);
+
+    if (m_entry == nullptr) {
+        m_entry = ::operator new(tree->m_entry_size);
+        R_UNLESS(m_entry != nullptr, ResultBufferAllocationFailed);
+
+        m_tree = tree;
+        m_offsets = offsets;
+    }
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::MoveNext() {
+    R_UNLESS(this->IsValid(), ResultOutOfRange);
+
+    // Invalidate our index, and read the header for the next index.
+    auto entry_index = m_entry_index + 1;
+    if (entry_index == m_entry_set.info.count) {
+        const auto entry_set_index = m_entry_set.info.index + 1;
+        R_UNLESS(entry_set_index < m_entry_set_count, ResultOutOfRange);
+
+        m_entry_index = -1;
+
+        const auto end = m_entry_set.info.end;
+
+        const auto entry_set_size = m_tree->m_node_size;
+        const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+
+        m_tree->m_entry_storage->ReadObject(std::addressof(m_entry_set), entry_set_offset);
+        R_TRY(m_entry_set.header.Verify(entry_set_index, entry_set_size, m_tree->m_entry_size));
+
+        R_UNLESS(m_entry_set.info.start == end && m_entry_set.info.start < m_entry_set.info.end,
+                 ResultInvalidBucketTreeEntrySetOffset);
+
+        entry_index = 0;
+    } else {
+        m_entry_index = 1;
+    }
+
+    // Read the new entry.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_offset = impl::GetBucketTreeEntryOffset(
+        m_entry_set.info.index, m_tree->m_node_size, entry_size, entry_index);
+    m_tree->m_entry_storage->Read(reinterpret_cast<u8*>(m_entry), entry_size, entry_offset);
+
+    // Note that we changed index.
+    m_entry_index = entry_index;
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::MovePrevious() {
+    R_UNLESS(this->IsValid(), ResultOutOfRange);
+
+    // Invalidate our index, and read the header for the previous index.
+    auto entry_index = m_entry_index;
+    if (entry_index == 0) {
+        R_UNLESS(m_entry_set.info.index > 0, ResultOutOfRange);
+
+        m_entry_index = -1;
+
+        const auto start = m_entry_set.info.start;
+
+        const auto entry_set_size = m_tree->m_node_size;
+        const auto entry_set_index = m_entry_set.info.index - 1;
+        const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+
+        m_tree->m_entry_storage->ReadObject(std::addressof(m_entry_set), entry_set_offset);
+        R_TRY(m_entry_set.header.Verify(entry_set_index, entry_set_size, m_tree->m_entry_size));
+
+        R_UNLESS(m_entry_set.info.end == start && m_entry_set.info.start < m_entry_set.info.end,
+                 ResultInvalidBucketTreeEntrySetOffset);
+
+        entry_index = m_entry_set.info.count;
+    } else {
+        m_entry_index = -1;
+    }
+
+    --entry_index;
+
+    // Read the new entry.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_offset = impl::GetBucketTreeEntryOffset(
+        m_entry_set.info.index, m_tree->m_node_size, entry_size, entry_index);
+    m_tree->m_entry_storage->Read(reinterpret_cast<u8*>(m_entry), entry_size, entry_offset);
+
+    // Note that we changed index.
+    m_entry_index = entry_index;
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::Find(s64 virtual_address) {
+    ASSERT(m_tree != nullptr);
+
+    // Get the node.
+    const auto* const node = m_tree->m_node_l1.Get<Node>();
+    R_UNLESS(virtual_address < node->GetEndOffset(), ResultOutOfRange);
+
+    // Get the entry set index.
+    s32 entry_set_index = -1;
+    if (m_tree->IsExistOffsetL2OnL1() && virtual_address < node->GetBeginOffset()) {
+        const auto start = node->GetEnd();
+        const auto end = node->GetBegin() + m_tree->m_offset_count;
+
+        auto pos = std::upper_bound(start, end, virtual_address);
+        R_UNLESS(start < pos, ResultOutOfRange);
+        --pos;
+
+        entry_set_index = static_cast<s32>(pos - start);
+    } else {
+        const auto start = node->GetBegin();
+        const auto end = node->GetEnd();
+
+        auto pos = std::upper_bound(start, end, virtual_address);
+        R_UNLESS(start < pos, ResultOutOfRange);
+        --pos;
+
+        if (m_tree->IsExistL2()) {
+            const auto node_index = static_cast<s32>(pos - start);
+            R_UNLESS(0 <= node_index && node_index < m_tree->m_offset_count,
+                     ResultInvalidBucketTreeNodeOffset);
+
+            R_TRY(this->FindEntrySet(std::addressof(entry_set_index), virtual_address, node_index));
+        } else {
+            entry_set_index = static_cast<s32>(pos - start);
+        }
+    }
+
+    // Validate the entry set index.
+    R_UNLESS(0 <= entry_set_index && entry_set_index < m_tree->m_entry_set_count,
+             ResultInvalidBucketTreeNodeOffset);
+
+    // Find the entry.
+    R_TRY(this->FindEntry(virtual_address, entry_set_index));
+
+    // Set count.
+    m_entry_set_count = m_tree->m_entry_set_count;
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntrySet(s32* out_index, s64 virtual_address, s32 node_index) {
+    const auto node_size = m_tree->m_node_size;
+
+    PooledBuffer pool(node_size, 1);
+    if (node_size <= pool.GetSize()) {
+        R_RETURN(
+            this->FindEntrySetWithBuffer(out_index, virtual_address, node_index, pool.GetBuffer()));
+    } else {
+        pool.Deallocate();
+        R_RETURN(this->FindEntrySetWithoutBuffer(out_index, virtual_address, node_index));
+    }
+}
+
+Result BucketTree::Visitor::FindEntrySetWithBuffer(s32* out_index, s64 virtual_address,
+                                                   s32 node_index, char* buffer) {
+    // Calculate node extents.
+    const auto node_size = m_tree->m_node_size;
+    const auto node_offset = (node_index + 1) * static_cast<s64>(node_size);
+    VirtualFile storage = m_tree->m_node_storage;
+
+    // Read the node.
+    storage->Read(reinterpret_cast<u8*>(buffer), node_size, node_offset);
+
+    // Validate the header.
+    NodeHeader header;
+    std::memcpy(std::addressof(header), buffer, NodeHeaderSize);
+    R_TRY(header.Verify(node_index, node_size, sizeof(s64)));
+
+    // Create the node, and find.
+    StorageNode node(sizeof(s64), header.count);
+    node.Find(buffer, virtual_address);
+    R_UNLESS(node.GetIndex() >= 0, ResultInvalidBucketTreeVirtualOffset);
+
+    // Return the index.
+    *out_index = static_cast<s32>(m_tree->GetEntrySetIndex(header.index, node.GetIndex()));
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntrySetWithoutBuffer(s32* out_index, s64 virtual_address,
+                                                      s32 node_index) {
+    // Calculate node extents.
+    const auto node_size = m_tree->m_node_size;
+    const auto node_offset = (node_index + 1) * static_cast<s64>(node_size);
+    VirtualFile storage = m_tree->m_node_storage;
+
+    // Read and validate the header.
+    NodeHeader header;
+    storage->ReadObject(std::addressof(header), node_offset);
+    R_TRY(header.Verify(node_index, node_size, sizeof(s64)));
+
+    // Create the node, and find.
+    StorageNode node(node_offset, sizeof(s64), header.count);
+    R_TRY(node.Find(storage, virtual_address));
+    R_UNLESS(node.GetIndex() >= 0, ResultOutOfRange);
+
+    // Return the index.
+    *out_index = static_cast<s32>(m_tree->GetEntrySetIndex(header.index, node.GetIndex()));
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntry(s64 virtual_address, s32 entry_set_index) {
+    const auto entry_set_size = m_tree->m_node_size;
+
+    PooledBuffer pool(entry_set_size, 1);
+    if (entry_set_size <= pool.GetSize()) {
+        R_RETURN(this->FindEntryWithBuffer(virtual_address, entry_set_index, pool.GetBuffer()));
+    } else {
+        pool.Deallocate();
+        R_RETURN(this->FindEntryWithoutBuffer(virtual_address, entry_set_index));
+    }
+}
+
+Result BucketTree::Visitor::FindEntryWithBuffer(s64 virtual_address, s32 entry_set_index,
+                                                char* buffer) {
+    // Calculate entry set extents.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_set_size = m_tree->m_node_size;
+    const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+    VirtualFile storage = m_tree->m_entry_storage;
+
+    // Read the entry set.
+    storage->Read(reinterpret_cast<u8*>(buffer), entry_set_size, entry_set_offset);
+
+    // Validate the entry_set.
+    EntrySetHeader entry_set;
+    std::memcpy(std::addressof(entry_set), buffer, sizeof(EntrySetHeader));
+    R_TRY(entry_set.header.Verify(entry_set_index, entry_set_size, entry_size));
+
+    // Create the node, and find.
+    StorageNode node(entry_size, entry_set.info.count);
+    node.Find(buffer, virtual_address);
+    R_UNLESS(node.GetIndex() >= 0, ResultOutOfRange);
+
+    // Copy the data into entry.
+    const auto entry_index = node.GetIndex();
+    const auto entry_offset = impl::GetBucketTreeEntryOffset(0, entry_size, entry_index);
+    std::memcpy(m_entry, buffer + entry_offset, entry_size);
+
+    // Set our entry set/index.
+    m_entry_set = entry_set;
+    m_entry_index = entry_index;
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntryWithoutBuffer(s64 virtual_address, s32 entry_set_index) {
+    // Calculate entry set extents.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_set_size = m_tree->m_node_size;
+    const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+    VirtualFile storage = m_tree->m_entry_storage;
+
+    // Read and validate the entry_set.
+    EntrySetHeader entry_set;
+    storage->ReadObject(std::addressof(entry_set), entry_set_offset);
+    R_TRY(entry_set.header.Verify(entry_set_index, entry_set_size, entry_size));
+
+    // Create the node, and find.
+    StorageNode node(entry_set_offset, entry_size, entry_set.info.count);
+    R_TRY(node.Find(storage, virtual_address));
+    R_UNLESS(node.GetIndex() >= 0, ResultOutOfRange);
+
+    // Copy the data into entry.
+    const auto entry_index = node.GetIndex();
+    const auto entry_offset =
+        impl::GetBucketTreeEntryOffset(entry_set_offset, entry_size, entry_index);
+    storage->Read(reinterpret_cast<u8*>(m_entry), entry_size, entry_offset);
+
+    // Set our entry set/index.
+    m_entry_set = entry_set;
+    m_entry_index = entry_index;
+
+    R_SUCCEED();
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_bucket_tree.h

@@ -0,0 +1,417 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <mutex>
+
+#include "common/alignment.h"
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/literals.h"
+
+#include "core/file_sys/vfs.h"
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+class BucketTree {
+    YUZU_NON_COPYABLE(BucketTree);
+    YUZU_NON_MOVEABLE(BucketTree);
+
+public:
+    static constexpr u32 Magic = Common::MakeMagic('B', 'K', 'T', 'R');
+    static constexpr u32 Version = 1;
+
+    static constexpr size_t NodeSizeMin = 1_KiB;
+    static constexpr size_t NodeSizeMax = 512_KiB;
+
+public:
+    class Visitor;
+
+    struct Header {
+        u32 magic;
+        u32 version;
+        s32 entry_count;
+        s32 reserved;
+
+        void Format(s32 entry_count);
+        Result Verify() const;
+    };
+    static_assert(std::is_trivial_v<Header>);
+    static_assert(sizeof(Header) == 0x10);
+
+    struct NodeHeader {
+        s32 index;
+        s32 count;
+        s64 offset;
+
+        Result Verify(s32 node_index, size_t node_size, size_t entry_size) const;
+    };
+    static_assert(std::is_trivial_v<NodeHeader>);
+    static_assert(sizeof(NodeHeader) == 0x10);
+
+    struct Offsets {
+        s64 start_offset;
+        s64 end_offset;
+
+        constexpr bool IsInclude(s64 offset) const {
+            return this->start_offset <= offset && offset < this->end_offset;
+        }
+
+        constexpr bool IsInclude(s64 offset, s64 size) const {
+            return size > 0 && this->start_offset <= offset && size <= (this->end_offset - offset);
+        }
+    };
+    static_assert(std::is_trivial_v<Offsets>);
+    static_assert(sizeof(Offsets) == 0x10);
+
+    struct OffsetCache {
+        Offsets offsets;
+        std::mutex mutex;
+        bool is_initialized;
+
+        OffsetCache() : offsets{-1, -1}, mutex(), is_initialized(false) {}
+    };
+
+    class ContinuousReadingInfo {
+    private:
+        size_t m_read_size;
+        s32 m_skip_count;
+        bool m_done;
+
+    public:
+        constexpr ContinuousReadingInfo() : m_read_size(), m_skip_count(), m_done() {}
+
+        constexpr void Reset() {
+            m_read_size = 0;
+            m_skip_count = 0;
+            m_done = false;
+        }
+
+        constexpr void SetSkipCount(s32 count) {
+            ASSERT(count >= 0);
+            m_skip_count = count;
+        }
+        constexpr s32 GetSkipCount() const {
+            return m_skip_count;
+        }
+        constexpr bool CheckNeedScan() {
+            return (--m_skip_count) <= 0;
+        }
+
+        constexpr void Done() {
+            m_read_size = 0;
+            m_done = true;
+        }
+        constexpr bool IsDone() const {
+            return m_done;
+        }
+
+        constexpr void SetReadSize(size_t size) {
+            m_read_size = size;
+        }
+        constexpr size_t GetReadSize() const {
+            return m_read_size;
+        }
+        constexpr bool CanDo() const {
+            return m_read_size > 0;
+        }
+    };
+
+private:
+    class NodeBuffer {
+        YUZU_NON_COPYABLE(NodeBuffer);
+
+    private:
+        void* m_header;
+
+    public:
+        NodeBuffer() : m_header() {}
+
+        ~NodeBuffer() {
+            ASSERT(m_header == nullptr);
+        }
+
+        NodeBuffer(NodeBuffer&& rhs) : m_header(rhs.m_header) {
+            rhs.m_header = nullptr;
+        }
+
+        NodeBuffer& operator=(NodeBuffer&& rhs) {
+            if (this != std::addressof(rhs)) {
+                ASSERT(m_header == nullptr);
+
+                m_header = rhs.m_header;
+
+                rhs.m_header = nullptr;
+            }
+            return *this;
+        }
+
+        bool Allocate(size_t node_size) {
+            ASSERT(m_header == nullptr);
+
+            m_header = ::operator new(node_size, std::align_val_t{sizeof(s64)});
+
+            // ASSERT(Common::IsAligned(m_header, sizeof(s64)));
+
+            return m_header != nullptr;
+        }
+
+        void Free(size_t node_size) {
+            if (m_header) {
+                ::operator delete(m_header, std::align_val_t{sizeof(s64)});
+                m_header = nullptr;
+            }
+        }
+
+        void FillZero(size_t node_size) const {
+            if (m_header) {
+                std::memset(m_header, 0, node_size);
+            }
+        }
+
+        NodeHeader* Get() const {
+            return reinterpret_cast<NodeHeader*>(m_header);
+        }
+
+        NodeHeader* operator->() const {
+            return this->Get();
+        }
+
+        template <typename T>
+        T* Get() const {
+            static_assert(std::is_trivial_v<T>);
+            static_assert(sizeof(T) == sizeof(NodeHeader));
+            return reinterpret_cast<T*>(m_header);
+        }
+    };
+
+private:
+    static constexpr s32 GetEntryCount(size_t node_size, size_t entry_size) {
+        return static_cast<s32>((node_size - sizeof(NodeHeader)) / entry_size);
+    }
+
+    static constexpr s32 GetOffsetCount(size_t node_size) {
+        return static_cast<s32>((node_size - sizeof(NodeHeader)) / sizeof(s64));
+    }
+
+    static constexpr s32 GetEntrySetCount(size_t node_size, size_t entry_size, s32 entry_count) {
+        const s32 entry_count_per_node = GetEntryCount(node_size, entry_size);
+        return Common::DivideUp(entry_count, entry_count_per_node);
+    }
+
+    static constexpr s32 GetNodeL2Count(size_t node_size, size_t entry_size, s32 entry_count) {
+        const s32 offset_count_per_node = GetOffsetCount(node_size);
+        const s32 entry_set_count = GetEntrySetCount(node_size, entry_size, entry_count);
+
+        if (entry_set_count <= offset_count_per_node) {
+            return 0;
+        }
+
+        const s32 node_l2_count = Common::DivideUp(entry_set_count, offset_count_per_node);
+        ASSERT(node_l2_count <= offset_count_per_node);
+
+        return Common::DivideUp(entry_set_count - (offset_count_per_node - (node_l2_count - 1)),
+                                offset_count_per_node);
+    }
+
+public:
+    static constexpr s64 QueryHeaderStorageSize() {
+        return sizeof(Header);
+    }
+
+    static constexpr s64 QueryNodeStorageSize(size_t node_size, size_t entry_size,
+                                              s32 entry_count) {
+        ASSERT(entry_size >= sizeof(s64));
+        ASSERT(node_size >= entry_size + sizeof(NodeHeader));
+        ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+        ASSERT(Common::IsPowerOfTwo(node_size));
+        ASSERT(entry_count >= 0);
+
+        if (entry_count <= 0) {
+            return 0;
+        }
+        return (1 + GetNodeL2Count(node_size, entry_size, entry_count)) *
+               static_cast<s64>(node_size);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(size_t node_size, size_t entry_size,
+                                               s32 entry_count) {
+        ASSERT(entry_size >= sizeof(s64));
+        ASSERT(node_size >= entry_size + sizeof(NodeHeader));
+        ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+        ASSERT(Common::IsPowerOfTwo(node_size));
+        ASSERT(entry_count >= 0);
+
+        if (entry_count <= 0) {
+            return 0;
+        }
+        return GetEntrySetCount(node_size, entry_size, entry_count) * static_cast<s64>(node_size);
+    }
+
+private:
+    mutable VirtualFile m_node_storage;
+    mutable VirtualFile m_entry_storage;
+    NodeBuffer m_node_l1;
+    size_t m_node_size;
+    size_t m_entry_size;
+    s32 m_entry_count;
+    s32 m_offset_count;
+    s32 m_entry_set_count;
+    OffsetCache m_offset_cache;
+
+public:
+    BucketTree()
+        : m_node_storage(), m_entry_storage(), m_node_l1(), m_node_size(), m_entry_size(),
+          m_entry_count(), m_offset_count(), m_entry_set_count(), m_offset_cache() {}
+    ~BucketTree() {
+        this->Finalize();
+    }
+
+    Result Initialize(VirtualFile node_storage, VirtualFile entry_storage, size_t node_size,
+                      size_t entry_size, s32 entry_count);
+    void Initialize(size_t node_size, s64 end_offset);
+    void Finalize();
+
+    bool IsInitialized() const {
+        return m_node_size > 0;
+    }
+    bool IsEmpty() const {
+        return m_entry_size == 0;
+    }
+
+    Result Find(Visitor* visitor, s64 virtual_address);
+    Result InvalidateCache();
+
+    s32 GetEntryCount() const {
+        return m_entry_count;
+    }
+
+    Result GetOffsets(Offsets* out) {
+        // Ensure we have an offset cache.
+        R_TRY(this->EnsureOffsetCache());
+
+        // Set the output.
+        *out = m_offset_cache.offsets;
+        R_SUCCEED();
+    }
+
+private:
+    template <typename EntryType>
+    struct ContinuousReadingParam {
+        s64 offset;
+        size_t size;
+        NodeHeader entry_set;
+        s32 entry_index;
+        Offsets offsets;
+        EntryType entry;
+    };
+
+private:
+    template <typename EntryType>
+    Result ScanContinuousReading(ContinuousReadingInfo* out_info,
+                                 const ContinuousReadingParam<EntryType>& param) const;
+
+    bool IsExistL2() const {
+        return m_offset_count < m_entry_set_count;
+    }
+    bool IsExistOffsetL2OnL1() const {
+        return this->IsExistL2() && m_node_l1->count < m_offset_count;
+    }
+
+    s64 GetEntrySetIndex(s32 node_index, s32 offset_index) const {
+        return (m_offset_count - m_node_l1->count) + (m_offset_count * node_index) + offset_index;
+    }
+
+    Result EnsureOffsetCache();
+};
+
+class BucketTree::Visitor {
+    YUZU_NON_COPYABLE(Visitor);
+    YUZU_NON_MOVEABLE(Visitor);
+
+private:
+    friend class BucketTree;
+
+    union EntrySetHeader {
+        NodeHeader header;
+        struct Info {
+            s32 index;
+            s32 count;
+            s64 end;
+            s64 start;
+        } info;
+        static_assert(std::is_trivial_v<Info>);
+    };
+    static_assert(std::is_trivial_v<EntrySetHeader>);
+
+private:
+    const BucketTree* m_tree;
+    BucketTree::Offsets m_offsets;
+    void* m_entry;
+    s32 m_entry_index;
+    s32 m_entry_set_count;
+    EntrySetHeader m_entry_set;
+
+public:
+    constexpr Visitor()
+        : m_tree(), m_entry(), m_entry_index(-1), m_entry_set_count(), m_entry_set{} {}
+    ~Visitor() {
+        if (m_entry != nullptr) {
+            ::operator delete(m_entry, m_tree->m_entry_size);
+            m_tree = nullptr;
+            m_entry = nullptr;
+        }
+    }
+
+    bool IsValid() const {
+        return m_entry_index >= 0;
+    }
+    bool CanMoveNext() const {
+        return this->IsValid() && (m_entry_index + 1 < m_entry_set.info.count ||
+                                   m_entry_set.info.index + 1 < m_entry_set_count);
+    }
+    bool CanMovePrevious() const {
+        return this->IsValid() && (m_entry_index > 0 || m_entry_set.info.index > 0);
+    }
+
+    Result MoveNext();
+    Result MovePrevious();
+
+    template <typename EntryType>
+    Result ScanContinuousReading(ContinuousReadingInfo* out_info, s64 offset, size_t size) const;
+
+    const void* Get() const {
+        ASSERT(this->IsValid());
+        return m_entry;
+    }
+
+    template <typename T>
+    const T* Get() const {
+        ASSERT(this->IsValid());
+        return reinterpret_cast<const T*>(m_entry);
+    }
+
+    const BucketTree* GetTree() const {
+        return m_tree;
+    }
+
+private:
+    Result Initialize(const BucketTree* tree, const BucketTree::Offsets& offsets);
+
+    Result Find(s64 virtual_address);
+
+    Result FindEntrySet(s32* out_index, s64 virtual_address, s32 node_index);
+    Result FindEntrySetWithBuffer(s32* out_index, s64 virtual_address, s32 node_index,
+                                  char* buffer);
+    Result FindEntrySetWithoutBuffer(s32* out_index, s64 virtual_address, s32 node_index);
+
+    Result FindEntry(s64 virtual_address, s32 entry_set_index);
+    Result FindEntryWithBuffer(s64 virtual_address, s32 entry_set_index, char* buffer);
+    Result FindEntryWithoutBuffer(s64 virtual_address, s32 entry_set_index);
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_bucket_tree_template_impl.h

@@ -0,0 +1,170 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree_utils.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+template <typename EntryType>
+Result BucketTree::ScanContinuousReading(ContinuousReadingInfo* out_info,
+                                         const ContinuousReadingParam<EntryType>& param) const {
+    static_assert(std::is_trivial_v<ContinuousReadingParam<EntryType>>);
+
+    // Validate our preconditions.
+    ASSERT(this->IsInitialized());
+    ASSERT(out_info != nullptr);
+    ASSERT(m_entry_size == sizeof(EntryType));
+
+    // Reset the output.
+    out_info->Reset();
+
+    // If there's nothing to read, we're done.
+    R_SUCCEED_IF(param.size == 0);
+
+    // If we're reading a fragment, we're done.
+    R_SUCCEED_IF(param.entry.IsFragment());
+
+    // Validate the first entry.
+    auto entry = param.entry;
+    auto cur_offset = param.offset;
+    R_UNLESS(entry.GetVirtualOffset() <= cur_offset, ResultOutOfRange);
+
+    // Create a pooled buffer for our scan.
+    PooledBuffer pool(m_node_size, 1);
+    char* buffer = nullptr;
+
+    s64 entry_storage_size = m_entry_storage->GetSize();
+
+    // Read the node.
+    if (m_node_size <= pool.GetSize()) {
+        buffer = pool.GetBuffer();
+        const auto ofs = param.entry_set.index * static_cast<s64>(m_node_size);
+        R_UNLESS(m_node_size + ofs <= static_cast<size_t>(entry_storage_size),
+                 ResultInvalidBucketTreeNodeEntryCount);
+
+        m_entry_storage->Read(reinterpret_cast<u8*>(buffer), m_node_size, ofs);
+    }
+
+    // Calculate extents.
+    const auto end_offset = cur_offset + static_cast<s64>(param.size);
+    s64 phys_offset = entry.GetPhysicalOffset();
+
+    // Start merge tracking.
+    s64 merge_size = 0;
+    s64 readable_size = 0;
+    bool merged = false;
+
+    // Iterate.
+    auto entry_index = param.entry_index;
+    for (const auto entry_count = param.entry_set.count; entry_index < entry_count; ++entry_index) {
+        // If we're past the end, we're done.
+        if (end_offset <= cur_offset) {
+            break;
+        }
+
+        // Validate the entry offset.
+        const auto entry_offset = entry.GetVirtualOffset();
+        R_UNLESS(entry_offset <= cur_offset, ResultInvalidIndirectEntryOffset);
+
+        // Get the next entry.
+        EntryType next_entry = {};
+        s64 next_entry_offset;
+
+        if (entry_index + 1 < entry_count) {
+            if (buffer != nullptr) {
+                const auto ofs = impl::GetBucketTreeEntryOffset(0, m_entry_size, entry_index + 1);
+                std::memcpy(std::addressof(next_entry), buffer + ofs, m_entry_size);
+            } else {
+                const auto ofs = impl::GetBucketTreeEntryOffset(param.entry_set.index, m_node_size,
+                                                                m_entry_size, entry_index + 1);
+                m_entry_storage->ReadObject(std::addressof(next_entry), ofs);
+            }
+
+            next_entry_offset = next_entry.GetVirtualOffset();
+            R_UNLESS(param.offsets.IsInclude(next_entry_offset), ResultInvalidIndirectEntryOffset);
+        } else {
+            next_entry_offset = param.entry_set.offset;
+        }
+
+        // Validate the next entry offset.
+        R_UNLESS(cur_offset < next_entry_offset, ResultInvalidIndirectEntryOffset);
+
+        // Determine the much data there is.
+        const auto data_size = next_entry_offset - cur_offset;
+        ASSERT(data_size > 0);
+
+        // Determine how much data we should read.
+        const auto remaining_size = end_offset - cur_offset;
+        const size_t read_size = static_cast<size_t>(std::min(data_size, remaining_size));
+        ASSERT(read_size <= param.size);
+
+        // Update our merge tracking.
+        if (entry.IsFragment()) {
+            // If we can't merge, stop looping.
+            if (EntryType::FragmentSizeMax <= read_size || remaining_size <= data_size) {
+                break;
+            }
+
+            // Otherwise, add the current size to the merge size.
+            merge_size += read_size;
+        } else {
+            //  If we can't merge, stop looping.
+            if (phys_offset != entry.GetPhysicalOffset()) {
+                break;
+            }
+
+            // Add the size to the readable amount.
+            readable_size += merge_size + read_size;
+            ASSERT(readable_size <= static_cast<s64>(param.size));
+
+            // Update whether we've merged.
+            merged |= merge_size > 0;
+            merge_size = 0;
+        }
+
+        // Advance.
+        cur_offset += read_size;
+        ASSERT(cur_offset <= end_offset);
+
+        phys_offset += next_entry_offset - entry_offset;
+        entry = next_entry;
+    }
+
+    // If we merged, set our readable size.
+    if (merged) {
+        out_info->SetReadSize(static_cast<size_t>(readable_size));
+    }
+    out_info->SetSkipCount(entry_index - param.entry_index);
+
+    R_SUCCEED();
+}
+
+template <typename EntryType>
+Result BucketTree::Visitor::ScanContinuousReading(ContinuousReadingInfo* out_info, s64 offset,
+                                                  size_t size) const {
+    static_assert(std::is_trivial_v<EntryType>);
+    ASSERT(this->IsValid());
+
+    // Create our parameters.
+    ContinuousReadingParam<EntryType> param = {
+        .offset = offset,
+        .size = size,
+        .entry_set = m_entry_set.header,
+        .entry_index = m_entry_index,
+        .offsets{},
+        .entry{},
+    };
+    std::memcpy(std::addressof(param.offsets), std::addressof(m_offsets),
+                sizeof(BucketTree::Offsets));
+    std::memcpy(std::addressof(param.entry), m_entry, sizeof(EntryType));
+
+    // Scan.
+    R_RETURN(m_tree->ScanContinuousReading<EntryType>(out_info, param));
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_bucket_tree_utils.h

@@ -0,0 +1,110 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+
+namespace FileSys::impl {
+
+class SafeValue {
+public:
+    static s64 GetInt64(const void* ptr) {
+        s64 value;
+        std::memcpy(std::addressof(value), ptr, sizeof(s64));
+        return value;
+    }
+
+    static s64 GetInt64(const s64* ptr) {
+        return GetInt64(static_cast<const void*>(ptr));
+    }
+
+    static s64 GetInt64(const s64& v) {
+        return GetInt64(std::addressof(v));
+    }
+
+    static void SetInt64(void* dst, const void* src) {
+        std::memcpy(dst, src, sizeof(s64));
+    }
+
+    static void SetInt64(void* dst, const s64* src) {
+        return SetInt64(dst, static_cast<const void*>(src));
+    }
+
+    static void SetInt64(void* dst, const s64& v) {
+        return SetInt64(dst, std::addressof(v));
+    }
+};
+
+template <typename IteratorType>
+struct BucketTreeNode {
+    using Header = BucketTree::NodeHeader;
+
+    Header header;
+
+    s32 GetCount() const {
+        return this->header.count;
+    }
+
+    void* GetArray() {
+        return std::addressof(this->header) + 1;
+    }
+    template <typename T>
+    T* GetArray() {
+        return reinterpret_cast<T*>(this->GetArray());
+    }
+    const void* GetArray() const {
+        return std::addressof(this->header) + 1;
+    }
+    template <typename T>
+    const T* GetArray() const {
+        return reinterpret_cast<const T*>(this->GetArray());
+    }
+
+    s64 GetBeginOffset() const {
+        return *this->GetArray<s64>();
+    }
+    s64 GetEndOffset() const {
+        return this->header.offset;
+    }
+
+    IteratorType GetBegin() {
+        return IteratorType(this->GetArray<s64>());
+    }
+    IteratorType GetEnd() {
+        return IteratorType(this->GetArray<s64>()) + this->header.count;
+    }
+    IteratorType GetBegin() const {
+        return IteratorType(this->GetArray<s64>());
+    }
+    IteratorType GetEnd() const {
+        return IteratorType(this->GetArray<s64>()) + this->header.count;
+    }
+
+    IteratorType GetBegin(size_t entry_size) {
+        return IteratorType(this->GetArray(), entry_size);
+    }
+    IteratorType GetEnd(size_t entry_size) {
+        return IteratorType(this->GetArray(), entry_size) + this->header.count;
+    }
+    IteratorType GetBegin(size_t entry_size) const {
+        return IteratorType(this->GetArray(), entry_size);
+    }
+    IteratorType GetEnd(size_t entry_size) const {
+        return IteratorType(this->GetArray(), entry_size) + this->header.count;
+    }
+};
+
+constexpr inline s64 GetBucketTreeEntryOffset(s64 entry_set_offset, size_t entry_size,
+                                              s32 entry_index) {
+    return entry_set_offset + sizeof(BucketTree::NodeHeader) +
+           entry_index * static_cast<s64>(entry_size);
+}
+
+constexpr inline s64 GetBucketTreeEntryOffset(s32 entry_set_index, size_t node_size,
+                                              size_t entry_size, s32 entry_index) {
+    return GetBucketTreeEntryOffset(entry_set_index * static_cast<s64>(node_size), entry_size,
+                                    entry_index);
+}
+
+} // namespace FileSys::impl

src/core/file_sys/fssystem/fssystem_compressed_storage.h

@@ -0,0 +1,960 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/literals.h"
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_compression_common.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+class CompressedStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(CompressedStorage);
+    YUZU_NON_MOVEABLE(CompressedStorage);
+
+public:
+    static constexpr size_t NodeSize = 16_KiB;
+
+    struct Entry {
+        s64 virt_offset;
+        s64 phys_offset;
+        CompressionType compression_type;
+        s32 phys_size;
+
+        s64 GetPhysicalSize() const {
+            return this->phys_size;
+        }
+    };
+    static_assert(std::is_trivial_v<Entry>);
+    static_assert(sizeof(Entry) == 0x18);
+
+public:
+    static constexpr s64 QueryNodeStorageSize(s32 entry_count) {
+        return BucketTree::QueryNodeStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(s32 entry_count) {
+        return BucketTree::QueryEntryStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+private:
+    class CompressedStorageCore {
+        YUZU_NON_COPYABLE(CompressedStorageCore);
+        YUZU_NON_MOVEABLE(CompressedStorageCore);
+
+    private:
+        size_t m_block_size_max;
+        size_t m_continuous_reading_size_max;
+        BucketTree m_table;
+        VirtualFile m_data_storage;
+        GetDecompressorFunction m_get_decompressor_function;
+
+    public:
+        CompressedStorageCore() : m_table(), m_data_storage() {}
+
+        ~CompressedStorageCore() {
+            this->Finalize();
+        }
+
+    public:
+        Result Initialize(VirtualFile data_storage, VirtualFile node_storage,
+                          VirtualFile entry_storage, s32 bktr_entry_count, size_t block_size_max,
+                          size_t continuous_reading_size_max,
+                          GetDecompressorFunction get_decompressor) {
+            // Check pre-conditions.
+            ASSERT(0 < block_size_max);
+            ASSERT(block_size_max <= continuous_reading_size_max);
+            ASSERT(get_decompressor != nullptr);
+
+            // Initialize our entry table.
+            R_TRY(m_table.Initialize(node_storage, entry_storage, NodeSize, sizeof(Entry),
+                                     bktr_entry_count));
+
+            // Set our other fields.
+            m_block_size_max = block_size_max;
+            m_continuous_reading_size_max = continuous_reading_size_max;
+            m_data_storage = data_storage;
+            m_get_decompressor_function = get_decompressor;
+
+            R_SUCCEED();
+        }
+
+        void Finalize() {
+            if (this->IsInitialized()) {
+                m_table.Finalize();
+                m_data_storage = VirtualFile();
+            }
+        }
+
+        VirtualFile GetDataStorage() {
+            return m_data_storage;
+        }
+
+        Result GetDataStorageSize(s64* out) {
+            // Check pre-conditions.
+            ASSERT(out != nullptr);
+
+            // Get size.
+            *out = m_data_storage->GetSize();
+
+            R_SUCCEED();
+        }
+
+        BucketTree& GetEntryTable() {
+            return m_table;
+        }
+
+        Result GetEntryList(Entry* out_entries, s32* out_read_count, s32 max_entry_count,
+                            s64 offset, s64 size) {
+            // Check pre-conditions.
+            ASSERT(offset >= 0);
+            ASSERT(size >= 0);
+            ASSERT(this->IsInitialized());
+
+            // Check that we can output the count.
+            R_UNLESS(out_read_count != nullptr, ResultNullptrArgument);
+
+            // Check that we have anything to read at all.
+            R_SUCCEED_IF(size == 0);
+
+            // Check that either we have a buffer, or this is to determine how many we need.
+            if (max_entry_count != 0) {
+                R_UNLESS(out_entries != nullptr, ResultNullptrArgument);
+            }
+
+            // Get the table offsets.
+            BucketTree::Offsets table_offsets;
+            R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+            // Validate arguments.
+            R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+            // Find the offset in our tree.
+            BucketTree::Visitor visitor;
+            R_TRY(m_table.Find(std::addressof(visitor), offset));
+            {
+                const auto entry_offset = visitor.Get<Entry>()->virt_offset;
+                R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                         ResultUnexpectedInCompressedStorageA);
+            }
+
+            // Get the entries.
+            const auto end_offset = offset + size;
+            s32 read_count = 0;
+            while (visitor.Get<Entry>()->virt_offset < end_offset) {
+                // If we should be setting the output, do so.
+                if (max_entry_count != 0) {
+                    // Ensure we only read as many entries as we can.
+                    if (read_count >= max_entry_count) {
+                        break;
+                    }
+
+                    // Set the current output entry.
+                    out_entries[read_count] = *visitor.Get<Entry>();
+                }
+
+                // Increase the read count.
+                ++read_count;
+
+                // If we're at the end, we're done.
+                if (!visitor.CanMoveNext()) {
+                    break;
+                }
+
+                // Move to the next entry.
+                R_TRY(visitor.MoveNext());
+            }
+
+            // Set the output read count.
+            *out_read_count = read_count;
+            R_SUCCEED();
+        }
+
+        Result GetSize(s64* out) {
+            // Check pre-conditions.
+            ASSERT(out != nullptr);
+
+            // Get our table offsets.
+            BucketTree::Offsets offsets;
+            R_TRY(m_table.GetOffsets(std::addressof(offsets)));
+
+            // Set the output.
+            *out = offsets.end_offset;
+            R_SUCCEED();
+        }
+
+        Result OperatePerEntry(s64 offset, s64 size, auto f) {
+            // Check pre-conditions.
+            ASSERT(offset >= 0);
+            ASSERT(size >= 0);
+            ASSERT(this->IsInitialized());
+
+            // Succeed if there's nothing to operate on.
+            R_SUCCEED_IF(size == 0);
+
+            // Get the table offsets.
+            BucketTree::Offsets table_offsets;
+            R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+            // Validate arguments.
+            R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+            // Find the offset in our tree.
+            BucketTree::Visitor visitor;
+            R_TRY(m_table.Find(std::addressof(visitor), offset));
+            {
+                const auto entry_offset = visitor.Get<Entry>()->virt_offset;
+                R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                         ResultUnexpectedInCompressedStorageA);
+            }
+
+            // Prepare to operate in chunks.
+            auto cur_offset = offset;
+            const auto end_offset = offset + static_cast<s64>(size);
+
+            while (cur_offset < end_offset) {
+                // Get the current entry.
+                const auto cur_entry = *visitor.Get<Entry>();
+
+                // Get and validate the entry's offset.
+                const auto cur_entry_offset = cur_entry.virt_offset;
+                R_UNLESS(cur_entry_offset <= cur_offset, ResultUnexpectedInCompressedStorageA);
+
+                // Get and validate the next entry offset.
+                s64 next_entry_offset;
+                if (visitor.CanMoveNext()) {
+                    R_TRY(visitor.MoveNext());
+                    next_entry_offset = visitor.Get<Entry>()->virt_offset;
+                    R_UNLESS(table_offsets.IsInclude(next_entry_offset),
+                             ResultUnexpectedInCompressedStorageA);
+                } else {
+                    next_entry_offset = table_offsets.end_offset;
+                }
+                R_UNLESS(cur_offset < next_entry_offset, ResultUnexpectedInCompressedStorageA);
+
+                // Get the offset of the entry in the data we read.
+                const auto data_offset = cur_offset - cur_entry_offset;
+                const auto data_size = (next_entry_offset - cur_entry_offset);
+                ASSERT(data_size > 0);
+
+                // Determine how much is left.
+                const auto remaining_size = end_offset - cur_offset;
+                const auto cur_size = std::min<s64>(remaining_size, data_size - data_offset);
+                ASSERT(cur_size <= size);
+
+                // Get the data storage size.
+                s64 storage_size = m_data_storage->GetSize();
+
+                // Check that our read remains naively physically in bounds.
+                R_UNLESS(0 <= cur_entry.phys_offset && cur_entry.phys_offset <= storage_size,
+                         ResultUnexpectedInCompressedStorageC);
+
+                // If we have any compression, verify that we remain physically in bounds.
+                if (cur_entry.compression_type != CompressionType::None) {
+                    R_UNLESS(cur_entry.phys_offset + cur_entry.GetPhysicalSize() <= storage_size,
+                             ResultUnexpectedInCompressedStorageC);
+                }
+
+                // Check that block alignment requirements are met.
+                if (CompressionTypeUtility::IsBlockAlignmentRequired(cur_entry.compression_type)) {
+                    R_UNLESS(Common::IsAligned(cur_entry.phys_offset, CompressionBlockAlignment),
+                             ResultUnexpectedInCompressedStorageA);
+                }
+
+                // Invoke the operator.
+                bool is_continuous = true;
+                R_TRY(
+                    f(std::addressof(is_continuous), cur_entry, data_size, data_offset, cur_size));
+
+                // If not continuous, we're done.
+                if (!is_continuous) {
+                    break;
+                }
+
+                // Advance.
+                cur_offset += cur_size;
+            }
+
+            R_SUCCEED();
+        }
+
+    public:
+        using ReadImplFunction = std::function<Result(void*, size_t)>;
+        using ReadFunction = std::function<Result(size_t, const ReadImplFunction&)>;
+
+    public:
+        Result Read(s64 offset, s64 size, const ReadFunction& read_func) {
+            // Check pre-conditions.
+            ASSERT(offset >= 0);
+            ASSERT(this->IsInitialized());
+
+            // Succeed immediately, if we hvae nothing to read.
+            R_SUCCEED_IF(size == 0);
+
+            // Declare read lambda.
+            constexpr int EntriesCountMax = 0x80;
+            struct Entries {
+                CompressionType compression_type;
+                u32 gap_from_prev;
+                u32 physical_size;
+                u32 virtual_size;
+            };
+            Entries entries[EntriesCountMax];
+            s32 entry_count = 0;
+            Entry prev_entry = {
+                .virt_offset = -1,
+            };
+            bool will_allocate_pooled_buffer = false;
+            s64 required_access_physical_offset = 0;
+            s64 required_access_physical_size = 0;
+
+            auto PerformRequiredRead = [&]() -> Result {
+                // If there are no entries, we have nothing to do.
+                R_SUCCEED_IF(entry_count == 0);
+
+                // Get the remaining size in a convenient form.
+                const size_t total_required_size =
+                    static_cast<size_t>(required_access_physical_size);
+
+                // Perform the read based on whether we need to allocate a buffer.
+                if (will_allocate_pooled_buffer) {
+                    // Allocate a pooled buffer.
+                    PooledBuffer pooled_buffer;
+                    if (pooled_buffer.GetAllocatableSizeMax() >= total_required_size) {
+                        pooled_buffer.Allocate(total_required_size, m_block_size_max);
+                    } else {
+                        pooled_buffer.AllocateParticularlyLarge(
+                            std::min<size_t>(
+                                total_required_size,
+                                PooledBuffer::GetAllocatableParticularlyLargeSizeMax()),
+                            m_block_size_max);
+                    }
+
+                    // Read each of the entries.
+                    for (s32 entry_idx = 0; entry_idx < entry_count; ++entry_idx) {
+                        // Determine the current read size.
+                        bool will_use_pooled_buffer = false;
+                        const size_t cur_read_size = [&]() -> size_t {
+                            if (const size_t target_entry_size =
+                                    static_cast<size_t>(entries[entry_idx].physical_size) +
+                                    static_cast<size_t>(entries[entry_idx].gap_from_prev);
+                                target_entry_size <= pooled_buffer.GetSize()) {
+                                // We'll be using the pooled buffer.
+                                will_use_pooled_buffer = true;
+
+                                // Determine how much we can read.
+                                const size_t max_size = std::min<size_t>(
+                                    required_access_physical_size, pooled_buffer.GetSize());
+
+                                size_t read_size = 0;
+                                for (auto n = entry_idx; n < entry_count; ++n) {
+                                    const size_t cur_entry_size =
+                                        static_cast<size_t>(entries[n].physical_size) +
+                                        static_cast<size_t>(entries[n].gap_from_prev);
+                                    if (read_size + cur_entry_size > max_size) {
+                                        break;
+                                    }
+
+                                    read_size += cur_entry_size;
+                                }
+
+                                return read_size;
+                            } else {
+                                // If we don't fit, we must be uncompressed.
+                                ASSERT(entries[entry_idx].compression_type ==
+                                       CompressionType::None);
+
+                                // We can perform the whole of an uncompressed read directly.
+                                return entries[entry_idx].virtual_size;
+                            }
+                        }();
+
+                        // Perform the read based on whether or not we'll use the pooled buffer.
+                        if (will_use_pooled_buffer) {
+                            // Read the compressed data into the pooled buffer.
+                            auto* const buffer = pooled_buffer.GetBuffer();
+                            m_data_storage->Read(reinterpret_cast<u8*>(buffer), cur_read_size,
+                                                 required_access_physical_offset);
+
+                            // Decompress the data.
+                            size_t buffer_offset;
+                            for (buffer_offset = 0;
+                                 entry_idx < entry_count &&
+                                 ((static_cast<size_t>(entries[entry_idx].physical_size) +
+                                   static_cast<size_t>(entries[entry_idx].gap_from_prev)) == 0 ||
+                                  buffer_offset < cur_read_size);
+                                 buffer_offset += entries[entry_idx++].physical_size) {
+                                // Advance by the relevant gap.
+                                buffer_offset += entries[entry_idx].gap_from_prev;
+
+                                const auto compression_type = entries[entry_idx].compression_type;
+                                switch (compression_type) {
+                                case CompressionType::None: {
+                                    // Check that we can remain within bounds.
+                                    ASSERT(buffer_offset + entries[entry_idx].virtual_size <=
+                                           cur_read_size);
+
+                                    // Perform no decompression.
+                                    R_TRY(read_func(
+                                        entries[entry_idx].virtual_size,
+                                        [&](void* dst, size_t dst_size) -> Result {
+                                            // Check that the size is valid.
+                                            ASSERT(dst_size == entries[entry_idx].virtual_size);
+
+                                            // We have no compression, so just copy the data
+                                            // out.
+                                            std::memcpy(dst, buffer + buffer_offset,
+                                                        entries[entry_idx].virtual_size);
+                                            R_SUCCEED();
+                                        }));
+
+                                    break;
+                                }
+                                case CompressionType::Zeros: {
+                                    // Check that we can remain within bounds.
+                                    ASSERT(buffer_offset <= cur_read_size);
+
+                                    // Zero the memory.
+                                    R_TRY(read_func(
+                                        entries[entry_idx].virtual_size,
+                                        [&](void* dst, size_t dst_size) -> Result {
+                                            // Check that the size is valid.
+                                            ASSERT(dst_size == entries[entry_idx].virtual_size);
+
+                                            // The data is zeroes, so zero the buffer.
+                                            std::memset(dst, 0, entries[entry_idx].virtual_size);
+                                            R_SUCCEED();
+                                        }));
+
+                                    break;
+                                }
+                                default: {
+                                    // Check that we can remain within bounds.
+                                    ASSERT(buffer_offset + entries[entry_idx].physical_size <=
+                                           cur_read_size);
+
+                                    // Get the decompressor.
+                                    const auto decompressor =
+                                        this->GetDecompressor(compression_type);
+                                    R_UNLESS(decompressor != nullptr,
+                                             ResultUnexpectedInCompressedStorageB);
+
+                                    // Decompress the data.
+                                    R_TRY(read_func(entries[entry_idx].virtual_size,
+                                                    [&](void* dst, size_t dst_size) -> Result {
+                                                        // Check that the size is valid.
+                                                        ASSERT(dst_size ==
+                                                               entries[entry_idx].virtual_size);
+
+                                                        // Perform the decompression.
+                                                        R_RETURN(decompressor(
+                                                            dst, entries[entry_idx].virtual_size,
+                                                            buffer + buffer_offset,
+                                                            entries[entry_idx].physical_size));
+                                                    }));
+
+                                    break;
+                                }
+                                }
+                            }
+
+                            // Check that we processed the correct amount of data.
+                            ASSERT(buffer_offset == cur_read_size);
+                        } else {
+                            // Account for the gap from the previous entry.
+                            required_access_physical_offset += entries[entry_idx].gap_from_prev;
+                            required_access_physical_size -= entries[entry_idx].gap_from_prev;
+
+                            // We don't need the buffer (as the data is uncompressed), so just
+                            // execute the read.
+                            R_TRY(
+                                read_func(cur_read_size, [&](void* dst, size_t dst_size) -> Result {
+                                    // Check that the size is valid.
+                                    ASSERT(dst_size == cur_read_size);
+
+                                    // Perform the read.
+                                    m_data_storage->Read(reinterpret_cast<u8*>(dst), cur_read_size,
+                                                         required_access_physical_offset);
+
+                                    R_SUCCEED();
+                                }));
+                        }
+
+                        // Advance on.
+                        required_access_physical_offset += cur_read_size;
+                        required_access_physical_size -= cur_read_size;
+                    }
+
+                    // Verify that we have nothing remaining to read.
+                    ASSERT(required_access_physical_size == 0);
+
+                    R_SUCCEED();
+                } else {
+                    // We don't need a buffer, so just execute the read.
+                    R_TRY(read_func(total_required_size, [&](void* dst, size_t dst_size) -> Result {
+                        // Check that the size is valid.
+                        ASSERT(dst_size == total_required_size);
+
+                        // Perform the read.
+                        m_data_storage->Read(reinterpret_cast<u8*>(dst), total_required_size,
+                                             required_access_physical_offset);
+
+                        R_SUCCEED();
+                    }));
+                }
+
+                R_SUCCEED();
+            };
+
+            R_TRY(this->OperatePerEntry(
+                offset, size,
+                [&](bool* out_continuous, const Entry& entry, s64 virtual_data_size,
+                    s64 data_offset, s64 read_size) -> Result {
+                    // Determine the physical extents.
+                    s64 physical_offset, physical_size;
+                    if (CompressionTypeUtility::IsRandomAccessible(entry.compression_type)) {
+                        physical_offset = entry.phys_offset + data_offset;
+                        physical_size = read_size;
+                    } else {
+                        physical_offset = entry.phys_offset;
+                        physical_size = entry.GetPhysicalSize();
+                    }
+
+                    // If we have a pending data storage operation, perform it if we have to.
+                    const s64 required_access_physical_end =
+                        required_access_physical_offset + required_access_physical_size;
+                    if (required_access_physical_size > 0) {
+                        const bool required_by_gap =
+                            !(required_access_physical_end <= physical_offset &&
+                              physical_offset <= Common::AlignUp(required_access_physical_end,
+                                                                 CompressionBlockAlignment));
+                        const bool required_by_continuous_size =
+                            ((physical_size + physical_offset) - required_access_physical_end) +
+                                required_access_physical_size >
+                            static_cast<s64>(m_continuous_reading_size_max);
+                        const bool required_by_entry_count = entry_count == EntriesCountMax;
+                        if (required_by_gap || required_by_continuous_size ||
+                            required_by_entry_count) {
+                            // Check that our planned access is sane.
+                            ASSERT(!will_allocate_pooled_buffer ||
+                                   required_access_physical_size <=
+                                       static_cast<s64>(m_continuous_reading_size_max));
+
+                            // Perform the required read.
+                            const Result rc = PerformRequiredRead();
+                            if (R_FAILED(rc)) {
+                                R_THROW(rc);
+                            }
+
+                            // Reset our requirements.
+                            prev_entry.virt_offset = -1;
+                            required_access_physical_size = 0;
+                            entry_count = 0;
+                            will_allocate_pooled_buffer = false;
+                        }
+                    }
+
+                    // Sanity check that we're within bounds on entries.
+                    ASSERT(entry_count < EntriesCountMax);
+
+                    // Determine if a buffer allocation is needed.
+                    if (entry.compression_type != CompressionType::None ||
+                        (prev_entry.virt_offset >= 0 &&
+                         entry.virt_offset - prev_entry.virt_offset !=
+                             entry.phys_offset - prev_entry.phys_offset)) {
+                        will_allocate_pooled_buffer = true;
+                    }
+
+                    // If we need to access the data storage, update our required access parameters.
+                    if (CompressionTypeUtility::IsDataStorageAccessRequired(
+                            entry.compression_type)) {
+                        // If the data is compressed, ensure the access is sane.
+                        if (entry.compression_type != CompressionType::None) {
+                            R_UNLESS(data_offset == 0, ResultInvalidOffset);
+                            R_UNLESS(virtual_data_size == read_size, ResultInvalidSize);
+                            R_UNLESS(entry.GetPhysicalSize() <= static_cast<s64>(m_block_size_max),
+                                     ResultUnexpectedInCompressedStorageD);
+                        }
+
+                        // Update the required access parameters.
+                        s64 gap_from_prev;
+                        if (required_access_physical_size > 0) {
+                            gap_from_prev = physical_offset - required_access_physical_end;
+                        } else {
+                            gap_from_prev = 0;
+                            required_access_physical_offset = physical_offset;
+                        }
+                        required_access_physical_size += physical_size + gap_from_prev;
+
+                        // Create an entry. to access the data storage.
+                        entries[entry_count++] = {
+                            .compression_type = entry.compression_type,
+                            .gap_from_prev = static_cast<u32>(gap_from_prev),
+                            .physical_size = static_cast<u32>(physical_size),
+                            .virtual_size = static_cast<u32>(read_size),
+                        };
+                    } else {
+                        // Verify that we're allowed to be operating on the non-data-storage-access
+                        // type.
+                        R_UNLESS(entry.compression_type == CompressionType::Zeros,
+                                 ResultUnexpectedInCompressedStorageB);
+
+                        // If we have entries, create a fake entry for the zero region.
+                        if (entry_count != 0) {
+                            // We need to have a physical size.
+                            R_UNLESS(entry.GetPhysicalSize() != 0,
+                                     ResultUnexpectedInCompressedStorageD);
+
+                            // Create a fake entry.
+                            entries[entry_count++] = {
+                                .compression_type = CompressionType::Zeros,
+                                .gap_from_prev = 0,
+                                .physical_size = 0,
+                                .virtual_size = static_cast<u32>(read_size),
+                            };
+                        } else {
+                            // We have no entries, we we can just perform the read.
+                            const Result rc =
+                                read_func(static_cast<size_t>(read_size),
+                                          [&](void* dst, size_t dst_size) -> Result {
+                                              // Check the space we should zero is correct.
+                                              ASSERT(dst_size == static_cast<size_t>(read_size));
+
+                                              // Zero the memory.
+                                              std::memset(dst, 0, read_size);
+                                              R_SUCCEED();
+                                          });
+                            if (R_FAILED(rc)) {
+                                R_THROW(rc);
+                            }
+                        }
+                    }
+
+                    // Set the previous entry.
+                    prev_entry = entry;
+
+                    // We're continuous.
+                    *out_continuous = true;
+                    R_SUCCEED();
+                }));
+
+            // If we still have a pending access, perform it.
+            if (required_access_physical_size != 0) {
+                R_TRY(PerformRequiredRead());
+            }
+
+            R_SUCCEED();
+        }
+
+    private:
+        DecompressorFunction GetDecompressor(CompressionType type) const {
+            // Check that we can get a decompressor for the type.
+            if (CompressionTypeUtility::IsUnknownType(type)) {
+                return nullptr;
+            }
+
+            // Get the decompressor.
+            return m_get_decompressor_function(type);
+        }
+
+        bool IsInitialized() const {
+            return m_table.IsInitialized();
+        }
+    };
+
+    class CacheManager {
+        YUZU_NON_COPYABLE(CacheManager);
+        YUZU_NON_MOVEABLE(CacheManager);
+
+    private:
+        struct AccessRange {
+            s64 virtual_offset;
+            s64 virtual_size;
+            u32 physical_size;
+            bool is_block_alignment_required;
+
+            s64 GetEndVirtualOffset() const {
+                return this->virtual_offset + this->virtual_size;
+            }
+        };
+        static_assert(std::is_trivial_v<AccessRange>);
+
+    private:
+        s64 m_storage_size = 0;
+
+    public:
+        CacheManager() = default;
+
+    public:
+        Result Initialize(s64 storage_size, size_t cache_size_0, size_t cache_size_1,
+                          size_t max_cache_entries) {
+            // Set our fields.
+            m_storage_size = storage_size;
+
+            R_SUCCEED();
+        }
+
+        Result Read(CompressedStorageCore& core, s64 offset, void* buffer, size_t size) {
+            // If we have nothing to read, succeed.
+            R_SUCCEED_IF(size == 0);
+
+            // Check that we have a buffer to read into.
+            R_UNLESS(buffer != nullptr, ResultNullptrArgument);
+
+            // Check that the read is in bounds.
+            R_UNLESS(offset <= m_storage_size, ResultInvalidOffset);
+
+            // Determine how much we can read.
+            const size_t read_size = std::min<size_t>(size, m_storage_size - offset);
+
+            // Create head/tail ranges.
+            AccessRange head_range = {};
+            AccessRange tail_range = {};
+            bool is_tail_set = false;
+
+            // Operate to determine the head range.
+            R_TRY(core.OperatePerEntry(
+                offset, 1,
+                [&](bool* out_continuous, const Entry& entry, s64 virtual_data_size,
+                    s64 data_offset, s64 data_read_size) -> Result {
+                    // Set the head range.
+                    head_range = {
+                        .virtual_offset = entry.virt_offset,
+                        .virtual_size = virtual_data_size,
+                        .physical_size = static_cast<u32>(entry.phys_size),
+                        .is_block_alignment_required =
+                            CompressionTypeUtility::IsBlockAlignmentRequired(
+                                entry.compression_type),
+                    };
+
+                    // If required, set the tail range.
+                    if (static_cast<s64>(offset + read_size) <=
+                        entry.virt_offset + virtual_data_size) {
+                        tail_range = {
+                            .virtual_offset = entry.virt_offset,
+                            .virtual_size = virtual_data_size,
+                            .physical_size = static_cast<u32>(entry.phys_size),
+                            .is_block_alignment_required =
+                                CompressionTypeUtility::IsBlockAlignmentRequired(
+                                    entry.compression_type),
+                        };
+                        is_tail_set = true;
+                    }
+
+                    // We only want to determine the head range, so we're not continuous.
+                    *out_continuous = false;
+                    R_SUCCEED();
+                }));
+
+            // If necessary, determine the tail range.
+            if (!is_tail_set) {
+                R_TRY(core.OperatePerEntry(
+                    offset + read_size - 1, 1,
+                    [&](bool* out_continuous, const Entry& entry, s64 virtual_data_size,
+                        s64 data_offset, s64 data_read_size) -> Result {
+                        // Set the tail range.
+                        tail_range = {
+                            .virtual_offset = entry.virt_offset,
+                            .virtual_size = virtual_data_size,
+                            .physical_size = static_cast<u32>(entry.phys_size),
+                            .is_block_alignment_required =
+                                CompressionTypeUtility::IsBlockAlignmentRequired(
+                                    entry.compression_type),
+                        };
+
+                        // We only want to determine the tail range, so we're not continuous.
+                        *out_continuous = false;
+                        R_SUCCEED();
+                    }));
+            }
+
+            // Begin performing the accesses.
+            s64 cur_offset = offset;
+            size_t cur_size = read_size;
+            char* cur_dst = static_cast<char*>(buffer);
+
+            // Determine our alignment.
+            const bool head_unaligned = head_range.is_block_alignment_required &&
+                                        (cur_offset != head_range.virtual_offset ||
+                                         static_cast<s64>(cur_size) < head_range.virtual_size);
+            const bool tail_unaligned = [&]() -> bool {
+                if (tail_range.is_block_alignment_required) {
+                    if (static_cast<s64>(cur_size + cur_offset) ==
+                        tail_range.GetEndVirtualOffset()) {
+                        return false;
+                    } else if (!head_unaligned) {
+                        return true;
+                    } else {
+                        return head_range.GetEndVirtualOffset() <
+                               static_cast<s64>(cur_size + cur_offset);
+                    }
+                } else {
+                    return false;
+                }
+            }();
+
+            // Determine start/end offsets.
+            const s64 start_offset =
+                head_range.is_block_alignment_required ? head_range.virtual_offset : cur_offset;
+            const s64 end_offset = tail_range.is_block_alignment_required
+                                       ? tail_range.GetEndVirtualOffset()
+                                       : cur_offset + cur_size;
+
+            // Perform the read.
+            bool is_burst_reading = false;
+            R_TRY(core.Read(
+                start_offset, end_offset - start_offset,
+                [&](size_t size_buffer_required,
+                    const CompressedStorageCore::ReadImplFunction& read_impl) -> Result {
+                    // Determine whether we're burst reading.
+                    const AccessRange* unaligned_range = nullptr;
+                    if (!is_burst_reading) {
+                        // Check whether we're using head, tail, or none as unaligned.
+                        if (head_unaligned && head_range.virtual_offset <= cur_offset &&
+                            cur_offset < head_range.GetEndVirtualOffset()) {
+                            unaligned_range = std::addressof(head_range);
+                        } else if (tail_unaligned && tail_range.virtual_offset <= cur_offset &&
+                                   cur_offset < tail_range.GetEndVirtualOffset()) {
+                            unaligned_range = std::addressof(tail_range);
+                        } else {
+                            is_burst_reading = true;
+                        }
+                    }
+                    ASSERT((is_burst_reading ^ (unaligned_range != nullptr)));
+
+                    // Perform reading by burst, or not.
+                    if (is_burst_reading) {
+                        // Check that the access is valid for burst reading.
+                        ASSERT(size_buffer_required <= cur_size);
+
+                        // Perform the read.
+                        Result rc = read_impl(cur_dst, size_buffer_required);
+                        if (R_FAILED(rc)) {
+                            R_THROW(rc);
+                        }
+
+                        // Advance.
+                        cur_dst += size_buffer_required;
+                        cur_offset += size_buffer_required;
+                        cur_size -= size_buffer_required;
+
+                        // Determine whether we're going to continue burst reading.
+                        const s64 offset_aligned =
+                            tail_unaligned ? tail_range.virtual_offset : end_offset;
+                        ASSERT(cur_offset <= offset_aligned);
+
+                        if (offset_aligned <= cur_offset) {
+                            is_burst_reading = false;
+                        }
+                    } else {
+                        // We're not burst reading, so we have some unaligned range.
+                        ASSERT(unaligned_range != nullptr);
+
+                        // Check that the size is correct.
+                        ASSERT(size_buffer_required ==
+                               static_cast<size_t>(unaligned_range->virtual_size));
+
+                        // Get a pooled buffer for our read.
+                        PooledBuffer pooled_buffer;
+                        pooled_buffer.Allocate(size_buffer_required, size_buffer_required);
+
+                        // Perform read.
+                        Result rc = read_impl(pooled_buffer.GetBuffer(), size_buffer_required);
+                        if (R_FAILED(rc)) {
+                            R_THROW(rc);
+                        }
+
+                        // Copy the data we read to the destination.
+                        const size_t skip_size = cur_offset - unaligned_range->virtual_offset;
+                        const size_t copy_size = std::min<size_t>(
+                            cur_size, unaligned_range->GetEndVirtualOffset() - cur_offset);
+
+                        std::memcpy(cur_dst, pooled_buffer.GetBuffer() + skip_size, copy_size);
+
+                        // Advance.
+                        cur_dst += copy_size;
+                        cur_offset += copy_size;
+                        cur_size -= copy_size;
+                    }
+
+                    R_SUCCEED();
+                }));
+
+            R_SUCCEED();
+        }
+    };
+
+private:
+    mutable CompressedStorageCore m_core;
+    mutable CacheManager m_cache_manager;
+
+public:
+    CompressedStorage() = default;
+    virtual ~CompressedStorage() {
+        this->Finalize();
+    }
+
+    Result Initialize(VirtualFile data_storage, VirtualFile node_storage, VirtualFile entry_storage,
+                      s32 bktr_entry_count, size_t block_size_max,
+                      size_t continuous_reading_size_max, GetDecompressorFunction get_decompressor,
+                      size_t cache_size_0, size_t cache_size_1, s32 max_cache_entries) {
+        // Initialize our core.
+        R_TRY(m_core.Initialize(data_storage, node_storage, entry_storage, bktr_entry_count,
+                                block_size_max, continuous_reading_size_max, get_decompressor));
+
+        // Get our core size.
+        s64 core_size = 0;
+        R_TRY(m_core.GetSize(std::addressof(core_size)));
+
+        // Initialize our cache manager.
+        R_TRY(m_cache_manager.Initialize(core_size, cache_size_0, cache_size_1, max_cache_entries));
+
+        R_SUCCEED();
+    }
+
+    void Finalize() {
+        m_core.Finalize();
+    }
+
+    VirtualFile GetDataStorage() {
+        return m_core.GetDataStorage();
+    }
+
+    Result GetDataStorageSize(s64* out) {
+        R_RETURN(m_core.GetDataStorageSize(out));
+    }
+
+    Result GetEntryList(Entry* out_entries, s32* out_read_count, s32 max_entry_count, s64 offset,
+                        s64 size) {
+        R_RETURN(m_core.GetEntryList(out_entries, out_read_count, max_entry_count, offset, size));
+    }
+
+    BucketTree& GetEntryTable() {
+        return m_core.GetEntryTable();
+    }
+
+public:
+    virtual size_t GetSize() const override {
+        s64 ret{};
+        m_core.GetSize(&ret);
+        return ret;
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        if (R_SUCCEEDED(m_cache_manager.Read(m_core, offset, buffer, size))) {
+            return size;
+        } else {
+            return 0;
+        }
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_compression_common.h

@@ -0,0 +1,43 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+enum class CompressionType : u8 {
+    None = 0,
+    Zeros = 1,
+    Two = 2,
+    Lz4 = 3,
+    Unknown = 4,
+};
+
+using DecompressorFunction = Result (*)(void*, size_t, const void*, size_t);
+using GetDecompressorFunction = DecompressorFunction (*)(CompressionType);
+
+constexpr s64 CompressionBlockAlignment = 0x10;
+
+namespace CompressionTypeUtility {
+
+constexpr bool IsBlockAlignmentRequired(CompressionType type) {
+    return type != CompressionType::None && type != CompressionType::Zeros;
+}
+
+constexpr bool IsDataStorageAccessRequired(CompressionType type) {
+    return type != CompressionType::Zeros;
+}
+
+constexpr bool IsRandomAccessible(CompressionType type) {
+    return type == CompressionType::None;
+}
+
+constexpr bool IsUnknownType(CompressionType type) {
+    return type >= CompressionType::Unknown;
+}
+
+} // namespace CompressionTypeUtility
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_compression_configuration.cpp

@@ -0,0 +1,36 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/lz4_compression.h"
+#include "core/file_sys/fssystem/fssystem_compression_configuration.h"
+
+namespace FileSys {
+
+namespace {
+
+Result DecompressLz4(void* dst, size_t dst_size, const void* src, size_t src_size) {
+    auto result = Common::Compression::DecompressLZ4(dst, dst_size, src, src_size);
+    R_UNLESS(static_cast<size_t>(result) == dst_size, ResultUnexpectedInCompressedStorageC);
+    R_SUCCEED();
+}
+
+constexpr DecompressorFunction GetNcaDecompressorFunction(CompressionType type) {
+    switch (type) {
+    case CompressionType::Lz4:
+        return DecompressLz4;
+    default:
+        return nullptr;
+    }
+}
+
+constexpr NcaCompressionConfiguration g_nca_compression_configuration{
+    .get_decompressor = GetNcaDecompressorFunction,
+};
+
+} // namespace
+
+const NcaCompressionConfiguration* GetNcaCompressionConfiguration() {
+    return std::addressof(g_nca_compression_configuration);
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_compression_configuration.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_nca_file_system_driver.h"
+
+namespace FileSys {
+
+const NcaCompressionConfiguration* GetNcaCompressionConfiguration();
+
+}

src/core/file_sys/fssystem/fssystem_crypto_configuration.cpp

@@ -0,0 +1,57 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/crypto/aes_util.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/fssystem/fssystem_crypto_configuration.h"
+
+namespace FileSys {
+
+namespace {
+
+void GenerateKey(void* dst_key, size_t dst_key_size, const void* src_key, size_t src_key_size,
+                 s32 key_type) {
+    if (key_type == static_cast<s32>(KeyType::ZeroKey)) {
+        std::memset(dst_key, 0, dst_key_size);
+        return;
+    }
+
+    if (key_type == static_cast<s32>(KeyType::InvalidKey) ||
+        key_type < static_cast<s32>(KeyType::ZeroKey) ||
+        key_type >= static_cast<s32>(KeyType::NcaExternalKey)) {
+        std::memset(dst_key, 0xFF, dst_key_size);
+        return;
+    }
+
+    const auto& instance = Core::Crypto::KeyManager::Instance();
+
+    if (key_type == static_cast<s32>(KeyType::NcaHeaderKey1) ||
+        key_type == static_cast<s32>(KeyType::NcaHeaderKey2)) {
+        const s32 key_index = static_cast<s32>(KeyType::NcaHeaderKey2) == key_type;
+        const auto key = instance.GetKey(Core::Crypto::S256KeyType::Header);
+        std::memcpy(dst_key, key.data() + key_index * 0x10, std::min(dst_key_size, key.size() / 2));
+        return;
+    }
+
+    const s32 key_generation =
+        std::max(key_type / NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount, 1) - 1;
+    const s32 key_index = key_type % NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount;
+
+    Core::Crypto::AESCipher<Core::Crypto::Key128> cipher(
+        instance.GetKey(Core::Crypto::S128KeyType::KeyArea, key_generation, key_index),
+        Core::Crypto::Mode::ECB);
+    cipher.Transcode(reinterpret_cast<const u8*>(src_key), src_key_size,
+                     reinterpret_cast<u8*>(dst_key), Core::Crypto::Op::Decrypt);
+}
+
+} // namespace
+
+const NcaCryptoConfiguration& GetCryptoConfiguration() {
+    static const NcaCryptoConfiguration configuration = {
+        .generate_key = GenerateKey,
+    };
+
+    return configuration;
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_crypto_configuration.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_nca_file_system_driver.h"
+
+namespace FileSys {
+
+const NcaCryptoConfiguration& GetCryptoConfiguration();
+
+}

src/core/file_sys/fssystem/fssystem_hierarchical_integrity_verification_storage.cpp

@@ -0,0 +1,132 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_hierarchical_integrity_verification_storage.h"
+#include "core/file_sys/vfs_offset.h"
+
+namespace FileSys {
+
+HierarchicalIntegrityVerificationStorage::HierarchicalIntegrityVerificationStorage()
+    : m_data_size(-1) {
+    for (size_t i = 0; i < MaxLayers - 1; i++) {
+        m_verify_storages[i] = std::make_shared<IntegrityVerificationStorage>();
+    }
+}
+
+Result HierarchicalIntegrityVerificationStorage::Initialize(
+    const HierarchicalIntegrityVerificationInformation& info,
+    HierarchicalStorageInformation storage, int max_data_cache_entries, int max_hash_cache_entries,
+    s8 buffer_level) {
+    using AlignedStorage = AlignmentMatchingStoragePooledBuffer<1>;
+
+    // Validate preconditions.
+    ASSERT(IntegrityMinLayerCount <= info.max_layers && info.max_layers <= IntegrityMaxLayerCount);
+
+    // Set member variables.
+    m_max_layers = info.max_layers;
+
+    // Initialize the top level verification storage.
+    m_verify_storages[0]->Initialize(storage[HierarchicalStorageInformation::MasterStorage],
+                                     storage[HierarchicalStorageInformation::Layer1Storage],
+                                     static_cast<s64>(1) << info.info[0].block_order, HashSize,
+                                     false);
+
+    // Ensure we don't leak state if further initialization goes wrong.
+    ON_RESULT_FAILURE {
+        m_verify_storages[0]->Finalize();
+        m_data_size = -1;
+    };
+
+    // Initialize the top level buffer storage.
+    m_buffer_storages[0] = std::make_shared<AlignedStorage>(
+        m_verify_storages[0], static_cast<s64>(1) << info.info[0].block_order);
+    R_UNLESS(m_buffer_storages[0] != nullptr, ResultAllocationMemoryFailedAllocateShared);
+
+    // Prepare to initialize the level storages.
+    s32 level = 0;
+
+    // Ensure we don't leak state if further initialization goes wrong.
+    ON_RESULT_FAILURE_2 {
+        m_verify_storages[level + 1]->Finalize();
+        for (; level > 0; --level) {
+            m_buffer_storages[level].reset();
+            m_verify_storages[level]->Finalize();
+        }
+    };
+
+    // Initialize the level storages.
+    for (; level < m_max_layers - 3; ++level) {
+        // Initialize the verification storage.
+        auto buffer_storage =
+            std::make_shared<OffsetVfsFile>(m_buffer_storages[level], info.info[level].size, 0);
+        m_verify_storages[level + 1]->Initialize(
+            std::move(buffer_storage), storage[level + 2],
+            static_cast<s64>(1) << info.info[level + 1].block_order,
+            static_cast<s64>(1) << info.info[level].block_order, false);
+
+        // Initialize the buffer storage.
+        m_buffer_storages[level + 1] = std::make_shared<AlignedStorage>(
+            m_verify_storages[level + 1], static_cast<s64>(1) << info.info[level + 1].block_order);
+        R_UNLESS(m_buffer_storages[level + 1] != nullptr,
+                 ResultAllocationMemoryFailedAllocateShared);
+    }
+
+    // Initialize the final level storage.
+    {
+        // Initialize the verification storage.
+        auto buffer_storage =
+            std::make_shared<OffsetVfsFile>(m_buffer_storages[level], info.info[level].size, 0);
+        m_verify_storages[level + 1]->Initialize(
+            std::move(buffer_storage), storage[level + 2],
+            static_cast<s64>(1) << info.info[level + 1].block_order,
+            static_cast<s64>(1) << info.info[level].block_order, true);
+
+        // Initialize the buffer storage.
+        m_buffer_storages[level + 1] = std::make_shared<AlignedStorage>(
+            m_verify_storages[level + 1], static_cast<s64>(1) << info.info[level + 1].block_order);
+        R_UNLESS(m_buffer_storages[level + 1] != nullptr,
+                 ResultAllocationMemoryFailedAllocateShared);
+    }
+
+    // Set the data size.
+    m_data_size = info.info[level + 1].size;
+
+    // We succeeded.
+    R_SUCCEED();
+}
+
+void HierarchicalIntegrityVerificationStorage::Finalize() {
+    if (m_data_size >= 0) {
+        m_data_size = 0;
+
+        for (s32 level = m_max_layers - 2; level >= 0; --level) {
+            m_buffer_storages[level].reset();
+            m_verify_storages[level]->Finalize();
+        }
+
+        m_data_size = -1;
+    }
+}
+
+size_t HierarchicalIntegrityVerificationStorage::Read(u8* buffer, size_t size,
+                                                      size_t offset) const {
+    // Validate preconditions.
+    ASSERT(m_data_size >= 0);
+
+    // Succeed if zero-size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Read the data.
+    return m_buffer_storages[m_max_layers - 2]->Read(buffer, size, offset);
+}
+
+size_t HierarchicalIntegrityVerificationStorage::GetSize() const {
+    return m_data_size;
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_hierarchical_integrity_verification_storage.h

@@ -0,0 +1,164 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fs_types.h"
+#include "core/file_sys/fssystem/fssystem_alignment_matching_storage.h"
+#include "core/file_sys/fssystem/fssystem_integrity_verification_storage.h"
+#include "core/file_sys/vfs_offset.h"
+
+namespace FileSys {
+
+struct HierarchicalIntegrityVerificationLevelInformation {
+    Int64 offset;
+    Int64 size;
+    s32 block_order;
+    std::array<u8, 4> reserved;
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationLevelInformation>);
+static_assert(sizeof(HierarchicalIntegrityVerificationLevelInformation) == 0x18);
+static_assert(alignof(HierarchicalIntegrityVerificationLevelInformation) == 0x4);
+
+struct HierarchicalIntegrityVerificationInformation {
+    u32 max_layers;
+    HierarchicalIntegrityVerificationLevelInformation info[IntegrityMaxLayerCount - 1];
+    HashSalt seed;
+
+    s64 GetLayeredHashSize() const {
+        return this->info[this->max_layers - 2].offset;
+    }
+
+    s64 GetDataOffset() const {
+        return this->info[this->max_layers - 2].offset;
+    }
+
+    s64 GetDataSize() const {
+        return this->info[this->max_layers - 2].size;
+    }
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationInformation>);
+
+struct HierarchicalIntegrityVerificationMetaInformation {
+    u32 magic;
+    u32 version;
+    u32 master_hash_size;
+    HierarchicalIntegrityVerificationInformation level_hash_info;
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationMetaInformation>);
+
+struct HierarchicalIntegrityVerificationSizeSet {
+    s64 control_size;
+    s64 master_hash_size;
+    s64 layered_hash_sizes[IntegrityMaxLayerCount - 2];
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationSizeSet>);
+
+class HierarchicalIntegrityVerificationStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(HierarchicalIntegrityVerificationStorage);
+    YUZU_NON_MOVEABLE(HierarchicalIntegrityVerificationStorage);
+
+private:
+    friend struct HierarchicalIntegrityVerificationMetaInformation;
+
+protected:
+    static constexpr s64 HashSize = 256 / 8;
+    static constexpr size_t MaxLayers = IntegrityMaxLayerCount;
+
+public:
+    using GenerateRandomFunction = void (*)(void* dst, size_t size);
+
+    class HierarchicalStorageInformation {
+    public:
+        enum {
+            MasterStorage = 0,
+            Layer1Storage = 1,
+            Layer2Storage = 2,
+            Layer3Storage = 3,
+            Layer4Storage = 4,
+            Layer5Storage = 5,
+            DataStorage = 6,
+        };
+
+    private:
+        VirtualFile m_storages[DataStorage + 1];
+
+    public:
+        void SetMasterHashStorage(VirtualFile s) {
+            m_storages[MasterStorage] = s;
+        }
+        void SetLayer1HashStorage(VirtualFile s) {
+            m_storages[Layer1Storage] = s;
+        }
+        void SetLayer2HashStorage(VirtualFile s) {
+            m_storages[Layer2Storage] = s;
+        }
+        void SetLayer3HashStorage(VirtualFile s) {
+            m_storages[Layer3Storage] = s;
+        }
+        void SetLayer4HashStorage(VirtualFile s) {
+            m_storages[Layer4Storage] = s;
+        }
+        void SetLayer5HashStorage(VirtualFile s) {
+            m_storages[Layer5Storage] = s;
+        }
+        void SetDataStorage(VirtualFile s) {
+            m_storages[DataStorage] = s;
+        }
+
+        VirtualFile& operator[](s32 index) {
+            ASSERT(MasterStorage <= index && index <= DataStorage);
+            return m_storages[index];
+        }
+    };
+
+private:
+    static GenerateRandomFunction s_generate_random;
+
+    static void SetGenerateRandomFunction(GenerateRandomFunction func) {
+        s_generate_random = func;
+    }
+
+private:
+    std::shared_ptr<IntegrityVerificationStorage> m_verify_storages[MaxLayers - 1];
+    std::shared_ptr<AlignmentMatchingStoragePooledBuffer<1>> m_buffer_storages[MaxLayers - 1];
+    s64 m_data_size;
+    s32 m_max_layers;
+
+public:
+    HierarchicalIntegrityVerificationStorage();
+    virtual ~HierarchicalIntegrityVerificationStorage() override {
+        this->Finalize();
+    }
+
+    Result Initialize(const HierarchicalIntegrityVerificationInformation& info,
+                      HierarchicalStorageInformation storage, int max_data_cache_entries,
+                      int max_hash_cache_entries, s8 buffer_level);
+    void Finalize();
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t GetSize() const override;
+
+    bool IsInitialized() const {
+        return m_data_size >= 0;
+    }
+
+    s64 GetL1HashVerificationBlockSize() const {
+        return m_verify_storages[m_max_layers - 2]->GetBlockSize();
+    }
+
+    VirtualFile GetL1HashStorage() {
+        return std::make_shared<OffsetVfsFile>(
+            m_buffer_storages[m_max_layers - 3],
+            Common::DivideUp(m_data_size, this->GetL1HashVerificationBlockSize()), 0);
+    }
+
+public:
+    static constexpr s8 GetDefaultDataCacheBufferLevel(u32 max_layers) {
+        return static_cast<s8>(16 + max_layers - 2);
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_hierarchical_sha256_storage.cpp

@@ -0,0 +1,103 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "common/scope_exit.h"
+#include "core/file_sys/fssystem/fssystem_hierarchical_sha256_storage.h"
+
+namespace FileSys {
+
+namespace {
+
+s32 Log2(s32 value) {
+    ASSERT(value > 0);
+    ASSERT(Common::IsPowerOfTwo(value));
+
+    s32 log = 0;
+    while ((value >>= 1) > 0) {
+        ++log;
+    }
+    return log;
+}
+
+} // namespace
+
+Result HierarchicalSha256Storage::Initialize(VirtualFile* base_storages, s32 layer_count,
+                                             size_t htbs, void* hash_buf, size_t hash_buf_size) {
+    // Validate preconditions.
+    ASSERT(layer_count == LayerCount);
+    ASSERT(Common::IsPowerOfTwo(htbs));
+    ASSERT(hash_buf != nullptr);
+
+    // Set size tracking members.
+    m_hash_target_block_size = static_cast<s32>(htbs);
+    m_log_size_ratio = Log2(m_hash_target_block_size / HashSize);
+
+    // Get the base storage size.
+    m_base_storage_size = base_storages[2]->GetSize();
+    {
+        auto size_guard = SCOPE_GUARD({ m_base_storage_size = 0; });
+        R_UNLESS(m_base_storage_size <= static_cast<s64>(HashSize)
+                                            << m_log_size_ratio << m_log_size_ratio,
+                 ResultHierarchicalSha256BaseStorageTooLarge);
+        size_guard.Cancel();
+    }
+
+    // Set hash buffer tracking members.
+    m_base_storage = base_storages[2];
+    m_hash_buffer = static_cast<char*>(hash_buf);
+    m_hash_buffer_size = hash_buf_size;
+
+    // Read the master hash.
+    std::array<u8, HashSize> master_hash{};
+    base_storages[0]->ReadObject(std::addressof(master_hash));
+
+    // Read and validate the data being hashed.
+    s64 hash_storage_size = base_storages[1]->GetSize();
+    ASSERT(Common::IsAligned(hash_storage_size, HashSize));
+    ASSERT(hash_storage_size <= m_hash_target_block_size);
+    ASSERT(hash_storage_size <= static_cast<s64>(m_hash_buffer_size));
+
+    base_storages[1]->Read(reinterpret_cast<u8*>(m_hash_buffer),
+                           static_cast<size_t>(hash_storage_size), 0);
+
+    R_SUCCEED();
+}
+
+size_t HierarchicalSha256Storage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Succeed if zero-size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate that we have a buffer to read into.
+    ASSERT(buffer != nullptr);
+
+    // Validate preconditions.
+    ASSERT(Common::IsAligned(offset, m_hash_target_block_size));
+    ASSERT(Common::IsAligned(size, m_hash_target_block_size));
+
+    // Read the data.
+    const size_t reduced_size = static_cast<size_t>(
+        std::min<s64>(m_base_storage_size,
+                      Common::AlignUp(offset + size, m_hash_target_block_size)) -
+        offset);
+    m_base_storage->Read(buffer, reduced_size, offset);
+
+    // Setup tracking variables.
+    auto cur_offset = offset;
+    auto remaining_size = reduced_size;
+    while (remaining_size > 0) {
+        const auto cur_size =
+            static_cast<size_t>(std::min<s64>(m_hash_target_block_size, remaining_size));
+        ASSERT(static_cast<size_t>(cur_offset >> m_log_size_ratio) < m_hash_buffer_size);
+
+        // Advance.
+        cur_offset += cur_size;
+        remaining_size -= cur_size;
+    }
+
+    return size;
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_hierarchical_sha256_storage.h

@@ -0,0 +1,44 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <mutex>
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+class HierarchicalSha256Storage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(HierarchicalSha256Storage);
+    YUZU_NON_MOVEABLE(HierarchicalSha256Storage);
+
+public:
+    static constexpr s32 LayerCount = 3;
+    static constexpr size_t HashSize = 256 / 8;
+
+private:
+    VirtualFile m_base_storage;
+    s64 m_base_storage_size;
+    char* m_hash_buffer;
+    size_t m_hash_buffer_size;
+    s32 m_hash_target_block_size;
+    s32 m_log_size_ratio;
+    std::mutex m_mutex;
+
+public:
+    HierarchicalSha256Storage() : m_mutex() {}
+
+    Result Initialize(VirtualFile* base_storages, s32 layer_count, size_t htbs, void* hash_buf,
+                      size_t hash_buf_size);
+
+    virtual size_t GetSize() const override {
+        return m_base_storage->GetSize();
+    }
+
+    virtual size_t Read(u8* buffer, size_t length, size_t offset) const override;
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_indirect_storage.cpp

@@ -0,0 +1,120 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_indirect_storage.h"
+
+namespace FileSys {
+
+Result IndirectStorage::Initialize(VirtualFile table_storage) {
+    // Read and verify the bucket tree header.
+    BucketTree::Header header;
+    table_storage->ReadObject(std::addressof(header));
+    R_TRY(header.Verify());
+
+    // Determine extents.
+    const auto node_storage_size = QueryNodeStorageSize(header.entry_count);
+    const auto entry_storage_size = QueryEntryStorageSize(header.entry_count);
+    const auto node_storage_offset = QueryHeaderStorageSize();
+    const auto entry_storage_offset = node_storage_offset + node_storage_size;
+
+    // Initialize.
+    R_RETURN(this->Initialize(
+        std::make_shared<OffsetVfsFile>(table_storage, node_storage_size, node_storage_offset),
+        std::make_shared<OffsetVfsFile>(table_storage, entry_storage_size, entry_storage_offset),
+        header.entry_count));
+}
+
+void IndirectStorage::Finalize() {
+    if (this->IsInitialized()) {
+        m_table.Finalize();
+        for (auto i = 0; i < StorageCount; i++) {
+            m_data_storage[i] = VirtualFile();
+        }
+    }
+}
+
+Result IndirectStorage::GetEntryList(Entry* out_entries, s32* out_entry_count, s32 entry_count,
+                                     s64 offset, s64 size) {
+    // Validate pre-conditions.
+    ASSERT(offset >= 0);
+    ASSERT(size >= 0);
+    ASSERT(this->IsInitialized());
+
+    // Clear the out count.
+    R_UNLESS(out_entry_count != nullptr, ResultNullptrArgument);
+    *out_entry_count = 0;
+
+    // Succeed if there's no range.
+    R_SUCCEED_IF(size == 0);
+
+    // If we have an output array, we need it to be non-null.
+    R_UNLESS(out_entries != nullptr || entry_count == 0, ResultNullptrArgument);
+
+    // Check that our range is valid.
+    BucketTree::Offsets table_offsets;
+    R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+    R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    R_TRY(m_table.Find(std::addressof(visitor), offset));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetVirtualOffset();
+        R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                 ResultInvalidIndirectEntryOffset);
+    }
+
+    // Prepare to loop over entries.
+    const auto end_offset = offset + static_cast<s64>(size);
+    s32 count = 0;
+
+    auto cur_entry = *visitor.Get<Entry>();
+    while (cur_entry.GetVirtualOffset() < end_offset) {
+        // Try to write the entry to the out list
+        if (entry_count != 0) {
+            if (count >= entry_count) {
+                break;
+            }
+            std::memcpy(out_entries + count, std::addressof(cur_entry), sizeof(Entry));
+        }
+
+        count++;
+
+        // Advance.
+        if (visitor.CanMoveNext()) {
+            R_TRY(visitor.MoveNext());
+            cur_entry = *visitor.Get<Entry>();
+        } else {
+            break;
+        }
+    }
+
+    // Write the output count.
+    *out_entry_count = count;
+    R_SUCCEED();
+}
+
+size_t IndirectStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Validate pre-conditions.
+    ASSERT(offset >= 0);
+    ASSERT(this->IsInitialized());
+    ASSERT(buffer != nullptr);
+
+    // Succeed if there's nothing to read.
+    if (size == 0) {
+        return 0;
+    }
+
+    const_cast<IndirectStorage*>(this)->OperatePerEntry<true, true>(
+        offset, size,
+        [=](VirtualFile storage, s64 data_offset, s64 cur_offset, s64 cur_size) -> Result {
+            storage->Read(reinterpret_cast<u8*>(buffer) + (cur_offset - offset),
+                          static_cast<size_t>(cur_size), data_offset);
+            R_SUCCEED();
+        });
+
+    return size;
+}
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_indirect_storage.h

@@ -0,0 +1,294 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree_template_impl.h"
+#include "core/file_sys/vfs.h"
+#include "core/file_sys/vfs_offset.h"
+
+namespace FileSys {
+
+class IndirectStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(IndirectStorage);
+    YUZU_NON_MOVEABLE(IndirectStorage);
+
+public:
+    static constexpr s32 StorageCount = 2;
+    static constexpr size_t NodeSize = 16_KiB;
+
+    struct Entry {
+        u8 virt_offset[sizeof(s64)];
+        u8 phys_offset[sizeof(s64)];
+        s32 storage_index;
+
+        void SetVirtualOffset(const s64& ofs) {
+            std::memcpy(this->virt_offset, std::addressof(ofs), sizeof(s64));
+        }
+
+        s64 GetVirtualOffset() const {
+            s64 offset;
+            std::memcpy(std::addressof(offset), this->virt_offset, sizeof(s64));
+            return offset;
+        }
+
+        void SetPhysicalOffset(const s64& ofs) {
+            std::memcpy(this->phys_offset, std::addressof(ofs), sizeof(s64));
+        }
+
+        s64 GetPhysicalOffset() const {
+            s64 offset;
+            std::memcpy(std::addressof(offset), this->phys_offset, sizeof(s64));
+            return offset;
+        }
+    };
+    static_assert(std::is_trivial_v<Entry>);
+    static_assert(sizeof(Entry) == 0x14);
+
+    struct EntryData {
+        s64 virt_offset;
+        s64 phys_offset;
+        s32 storage_index;
+
+        void Set(const Entry& entry) {
+            this->virt_offset = entry.GetVirtualOffset();
+            this->phys_offset = entry.GetPhysicalOffset();
+            this->storage_index = entry.storage_index;
+        }
+    };
+    static_assert(std::is_trivial_v<EntryData>);
+
+private:
+    struct ContinuousReadingEntry {
+        static constexpr size_t FragmentSizeMax = 4_KiB;
+
+        IndirectStorage::Entry entry;
+
+        s64 GetVirtualOffset() const {
+            return this->entry.GetVirtualOffset();
+        }
+
+        s64 GetPhysicalOffset() const {
+            return this->entry.GetPhysicalOffset();
+        }
+
+        bool IsFragment() const {
+            return this->entry.storage_index != 0;
+        }
+    };
+    static_assert(std::is_trivial_v<ContinuousReadingEntry>);
+
+public:
+    static constexpr s64 QueryHeaderStorageSize() {
+        return BucketTree::QueryHeaderStorageSize();
+    }
+
+    static constexpr s64 QueryNodeStorageSize(s32 entry_count) {
+        return BucketTree::QueryNodeStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(s32 entry_count) {
+        return BucketTree::QueryEntryStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+private:
+    mutable BucketTree m_table;
+    std::array<VirtualFile, StorageCount> m_data_storage;
+
+public:
+    IndirectStorage() : m_table(), m_data_storage() {}
+    virtual ~IndirectStorage() {
+        this->Finalize();
+    }
+
+    Result Initialize(VirtualFile table_storage);
+    void Finalize();
+
+    bool IsInitialized() const {
+        return m_table.IsInitialized();
+    }
+
+    Result Initialize(VirtualFile node_storage, VirtualFile entry_storage, s32 entry_count) {
+        R_RETURN(
+            m_table.Initialize(node_storage, entry_storage, NodeSize, sizeof(Entry), entry_count));
+    }
+
+    void SetStorage(s32 idx, VirtualFile storage) {
+        ASSERT(0 <= idx && idx < StorageCount);
+        m_data_storage[idx] = storage;
+    }
+
+    template <typename T>
+    void SetStorage(s32 idx, T storage, s64 offset, s64 size) {
+        ASSERT(0 <= idx && idx < StorageCount);
+        m_data_storage[idx] = std::make_shared<OffsetVfsFile>(storage, size, offset);
+    }
+
+    Result GetEntryList(Entry* out_entries, s32* out_entry_count, s32 entry_count, s64 offset,
+                        s64 size);
+
+    virtual size_t GetSize() const override {
+        BucketTree::Offsets offsets;
+        m_table.GetOffsets(std::addressof(offsets));
+
+        return offsets.end_offset;
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+
+protected:
+    BucketTree& GetEntryTable() {
+        return m_table;
+    }
+
+    VirtualFile& GetDataStorage(s32 index) {
+        ASSERT(0 <= index && index < StorageCount);
+        return m_data_storage[index];
+    }
+
+    template <bool ContinuousCheck, bool RangeCheck, typename F>
+    Result OperatePerEntry(s64 offset, s64 size, F func);
+};
+
+template <bool ContinuousCheck, bool RangeCheck, typename F>
+Result IndirectStorage::OperatePerEntry(s64 offset, s64 size, F func) {
+    // Validate preconditions.
+    ASSERT(offset >= 0);
+    ASSERT(size >= 0);
+    ASSERT(this->IsInitialized());
+
+    // Succeed if there's nothing to operate on.
+    R_SUCCEED_IF(size == 0);
+
+    // Get the table offsets.
+    BucketTree::Offsets table_offsets;
+    R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+    // Validate arguments.
+    R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    R_TRY(m_table.Find(std::addressof(visitor), offset));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetVirtualOffset();
+        R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                 ResultInvalidIndirectEntryOffset);
+    }
+
+    // Prepare to operate in chunks.
+    auto cur_offset = offset;
+    const auto end_offset = offset + static_cast<s64>(size);
+    BucketTree::ContinuousReadingInfo cr_info;
+
+    while (cur_offset < end_offset) {
+        // Get the current entry.
+        const auto cur_entry = *visitor.Get<Entry>();
+
+        // Get and validate the entry's offset.
+        const auto cur_entry_offset = cur_entry.GetVirtualOffset();
+        R_UNLESS(cur_entry_offset <= cur_offset, ResultInvalidIndirectEntryOffset);
+
+        // Validate the storage index.
+        R_UNLESS(0 <= cur_entry.storage_index && cur_entry.storage_index < StorageCount,
+                 ResultInvalidIndirectEntryStorageIndex);
+
+        // If we need to check the continuous info, do so.
+        if constexpr (ContinuousCheck) {
+            // Scan, if we need to.
+            if (cr_info.CheckNeedScan()) {
+                R_TRY(visitor.ScanContinuousReading<ContinuousReadingEntry>(
+                    std::addressof(cr_info), cur_offset,
+                    static_cast<size_t>(end_offset - cur_offset)));
+            }
+
+            // Process a base storage entry.
+            if (cr_info.CanDo()) {
+                // Ensure that we can process.
+                R_UNLESS(cur_entry.storage_index == 0, ResultInvalidIndirectEntryStorageIndex);
+
+                // Ensure that we remain within range.
+                const auto data_offset = cur_offset - cur_entry_offset;
+                const auto cur_entry_phys_offset = cur_entry.GetPhysicalOffset();
+                const auto cur_size = static_cast<s64>(cr_info.GetReadSize());
+
+                // If we should, verify the range.
+                if constexpr (RangeCheck) {
+                    // Get the current data storage's size.
+                    s64 cur_data_storage_size = m_data_storage[0]->GetSize();
+
+                    R_UNLESS(0 <= cur_entry_phys_offset &&
+                                 cur_entry_phys_offset <= cur_data_storage_size,
+                             ResultInvalidIndirectEntryOffset);
+                    R_UNLESS(cur_entry_phys_offset + data_offset + cur_size <=
+                                 cur_data_storage_size,
+                             ResultInvalidIndirectStorageSize);
+                }
+
+                // Operate.
+                R_TRY(func(m_data_storage[0], cur_entry_phys_offset + data_offset, cur_offset,
+                           cur_size));
+
+                // Mark as done.
+                cr_info.Done();
+            }
+        }
+
+        // Get and validate the next entry offset.
+        s64 next_entry_offset;
+        if (visitor.CanMoveNext()) {
+            R_TRY(visitor.MoveNext());
+            next_entry_offset = visitor.Get<Entry>()->GetVirtualOffset();
+            R_UNLESS(table_offsets.IsInclude(next_entry_offset), ResultInvalidIndirectEntryOffset);
+        } else {
+            next_entry_offset = table_offsets.end_offset;
+        }
+        R_UNLESS(cur_offset < next_entry_offset, ResultInvalidIndirectEntryOffset);
+
+        // Get the offset of the entry in the data we read.
+        const auto data_offset = cur_offset - cur_entry_offset;
+        const auto data_size = (next_entry_offset - cur_entry_offset);
+        ASSERT(data_size > 0);
+
+        // Determine how much is left.
+        const auto remaining_size = end_offset - cur_offset;
+        const auto cur_size = std::min<s64>(remaining_size, data_size - data_offset);
+        ASSERT(cur_size <= size);
+
+        // Operate, if we need to.
+        bool needs_operate;
+        if constexpr (!ContinuousCheck) {
+            needs_operate = true;
+        } else {
+            needs_operate = !cr_info.IsDone() || cur_entry.storage_index != 0;
+        }
+
+        if (needs_operate) {
+            const auto cur_entry_phys_offset = cur_entry.GetPhysicalOffset();
+
+            if constexpr (RangeCheck) {
+                // Get the current data storage's size.
+                s64 cur_data_storage_size = m_data_storage[cur_entry.storage_index]->GetSize();
+
+                // Ensure that we remain within range.
+                R_UNLESS(0 <= cur_entry_phys_offset &&
+                             cur_entry_phys_offset <= cur_data_storage_size,
+                         ResultIndirectStorageCorrupted);
+                R_UNLESS(cur_entry_phys_offset + data_offset + cur_size <= cur_data_storage_size,
+                         ResultIndirectStorageCorrupted);
+            }
+
+            R_TRY(func(m_data_storage[cur_entry.storage_index], cur_entry_phys_offset + data_offset,
+                       cur_offset, cur_size));
+        }
+
+        cur_offset += cur_size;
+    }
+
+    R_SUCCEED();
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_integrity_romfs_storage.cpp

@@ -0,0 +1,30 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_integrity_romfs_storage.h"
+
+namespace FileSys {
+
+Result IntegrityRomFsStorage::Initialize(
+    HierarchicalIntegrityVerificationInformation level_hash_info, Hash master_hash,
+    HierarchicalIntegrityVerificationStorage::HierarchicalStorageInformation storage_info,
+    int max_data_cache_entries, int max_hash_cache_entries, s8 buffer_level) {
+    // Set master hash.
+    m_master_hash = master_hash;
+    m_master_hash_storage = std::make_shared<ArrayVfsFile<sizeof(Hash)>>(m_master_hash.value);
+    R_UNLESS(m_master_hash_storage != nullptr,
+             ResultAllocationMemoryFailedInIntegrityRomFsStorageA);
+
+    // Set the master hash storage.
+    storage_info[0] = m_master_hash_storage;
+
+    // Initialize our integrity storage.
+    R_RETURN(m_integrity_storage.Initialize(level_hash_info, storage_info, max_data_cache_entries,
+                                            max_hash_cache_entries, buffer_level));
+}
+
+void IntegrityRomFsStorage::Finalize() {
+    m_integrity_storage.Finalize();
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_integrity_romfs_storage.h

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_hierarchical_integrity_verification_storage.h"
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+#include "core/file_sys/vfs_vector.h"
+
+namespace FileSys {
+
+constexpr inline size_t IntegrityLayerCountRomFs = 7;
+constexpr inline size_t IntegrityHashLayerBlockSize = 16_KiB;
+
+class IntegrityRomFsStorage : public IReadOnlyStorage {
+private:
+    HierarchicalIntegrityVerificationStorage m_integrity_storage;
+    Hash m_master_hash;
+    std::shared_ptr<ArrayVfsFile<sizeof(Hash)>> m_master_hash_storage;
+
+public:
+    IntegrityRomFsStorage() {}
+    virtual ~IntegrityRomFsStorage() override {
+        this->Finalize();
+    }
+
+    Result Initialize(
+        HierarchicalIntegrityVerificationInformation level_hash_info, Hash master_hash,
+        HierarchicalIntegrityVerificationStorage::HierarchicalStorageInformation storage_info,
+        int max_data_cache_entries, int max_hash_cache_entries, s8 buffer_level);
+    void Finalize();
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        return m_integrity_storage.Read(buffer, size, offset);
+    }
+
+    virtual size_t GetSize() const override {
+        return m_integrity_storage.GetSize();
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_integrity_verification_storage.cpp

@@ -0,0 +1,95 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fssystem_integrity_verification_storage.h"
+
+namespace FileSys {
+
+constexpr inline u32 ILog2(u32 val) {
+    ASSERT(val > 0);
+    return ((sizeof(u32) * 8) - 1 - std::countl_zero<u32>(val));
+}
+
+void IntegrityVerificationStorage::Initialize(VirtualFile hs, VirtualFile ds, s64 verif_block_size,
+                                              s64 upper_layer_verif_block_size, bool is_real_data) {
+    // Validate preconditions.
+    ASSERT(verif_block_size >= HashSize);
+
+    // Set storages.
+    m_hash_storage = hs;
+    m_data_storage = ds;
+
+    // Set verification block sizes.
+    m_verification_block_size = verif_block_size;
+    m_verification_block_order = ILog2(static_cast<u32>(verif_block_size));
+    ASSERT(m_verification_block_size == 1ll << m_verification_block_order);
+
+    // Set upper layer block sizes.
+    upper_layer_verif_block_size = std::max(upper_layer_verif_block_size, HashSize);
+    m_upper_layer_verification_block_size = upper_layer_verif_block_size;
+    m_upper_layer_verification_block_order = ILog2(static_cast<u32>(upper_layer_verif_block_size));
+    ASSERT(m_upper_layer_verification_block_size == 1ll << m_upper_layer_verification_block_order);
+
+    // Validate sizes.
+    {
+        s64 hash_size = m_hash_storage->GetSize();
+        s64 data_size = m_data_storage->GetSize();
+        ASSERT(((hash_size / HashSize) * m_verification_block_size) >= data_size);
+    }
+
+    // Set data.
+    m_is_real_data = is_real_data;
+}
+
+void IntegrityVerificationStorage::Finalize() {
+    m_hash_storage = VirtualFile();
+    m_data_storage = VirtualFile();
+}
+
+size_t IntegrityVerificationStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Validate preconditions.
+    ASSERT(Common::IsAligned(offset, static_cast<size_t>(m_verification_block_size)));
+    ASSERT(Common::IsAligned(size, static_cast<size_t>(m_verification_block_size)));
+
+    // Succeed if zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Validate the offset.
+    s64 data_size = m_data_storage->GetSize();
+    ASSERT(offset <= static_cast<size_t>(data_size));
+
+    // Validate the access range.
+    ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(
+        offset, size, Common::AlignUp(data_size, static_cast<size_t>(m_verification_block_size)))));
+
+    // Determine the read extents.
+    size_t read_size = size;
+    if (static_cast<s64>(offset + read_size) > data_size) {
+        // Determine the padding sizes.
+        s64 padding_offset = data_size - offset;
+        size_t padding_size = static_cast<size_t>(
+            m_verification_block_size - (padding_offset & (m_verification_block_size - 1)));
+        ASSERT(static_cast<s64>(padding_size) < m_verification_block_size);
+
+        // Clear the padding.
+        std::memset(static_cast<u8*>(buffer) + padding_offset, 0, padding_size);
+
+        // Set the new in-bounds size.
+        read_size = static_cast<size_t>(data_size - offset);
+    }
+
+    // Perform the read.
+    return m_data_storage->Read(buffer, read_size, offset);
+}
+
+size_t IntegrityVerificationStorage::GetSize() const {
+    return m_data_storage->GetSize();
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_integrity_verification_storage.h

@@ -0,0 +1,65 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fs_types.h"
+
+namespace FileSys {
+
+class IntegrityVerificationStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(IntegrityVerificationStorage);
+    YUZU_NON_MOVEABLE(IntegrityVerificationStorage);
+
+public:
+    static constexpr s64 HashSize = 256 / 8;
+
+    struct BlockHash {
+        u8 hash[HashSize];
+    };
+    static_assert(std::is_trivial_v<BlockHash>);
+
+private:
+    VirtualFile m_hash_storage;
+    VirtualFile m_data_storage;
+    s64 m_verification_block_size;
+    s64 m_verification_block_order;
+    s64 m_upper_layer_verification_block_size;
+    s64 m_upper_layer_verification_block_order;
+    bool m_is_real_data;
+
+public:
+    IntegrityVerificationStorage()
+        : m_verification_block_size(0), m_verification_block_order(0),
+          m_upper_layer_verification_block_size(0), m_upper_layer_verification_block_order(0) {}
+    virtual ~IntegrityVerificationStorage() override {
+        this->Finalize();
+    }
+
+    void Initialize(VirtualFile hs, VirtualFile ds, s64 verif_block_size,
+                    s64 upper_layer_verif_block_size, bool is_real_data);
+    void Finalize();
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t GetSize() const override;
+
+    s64 GetBlockSize() const {
+        return m_verification_block_size;
+    }
+
+private:
+    static void SetValidationBit(BlockHash* hash) {
+        ASSERT(hash != nullptr);
+        hash->hash[HashSize - 1] |= 0x80;
+    }
+
+    static bool IsValidationBit(const BlockHash* hash) {
+        ASSERT(hash != nullptr);
+        return (hash->hash[HashSize - 1] & 0x80) != 0;
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_memory_resource_buffer_hold_storage.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class MemoryResourceBufferHoldStorage : public IStorage {
+    YUZU_NON_COPYABLE(MemoryResourceBufferHoldStorage);
+    YUZU_NON_MOVEABLE(MemoryResourceBufferHoldStorage);
+
+private:
+    VirtualFile m_storage;
+    void* m_buffer;
+    size_t m_buffer_size;
+
+public:
+    MemoryResourceBufferHoldStorage(VirtualFile storage, size_t buffer_size)
+        : m_storage(std::move(storage)), m_buffer(::operator new(buffer_size)),
+          m_buffer_size(buffer_size) {}
+
+    virtual ~MemoryResourceBufferHoldStorage() {
+        // If we have a buffer, deallocate it.
+        if (m_buffer != nullptr) {
+            ::operator delete(m_buffer);
+        }
+    }
+
+    bool IsValid() const {
+        return m_buffer != nullptr;
+    }
+    void* GetBuffer() const {
+        return m_buffer;
+    }
+
+public:
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Check pre-conditions.
+        ASSERT(m_storage != nullptr);
+
+        return m_storage->Read(buffer, size, offset);
+    }
+
+    virtual size_t GetSize() const override {
+        // Check pre-conditions.
+        ASSERT(m_storage != nullptr);
+
+        return m_storage->GetSize();
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        // Check pre-conditions.
+        ASSERT(m_storage != nullptr);
+
+        return m_storage->Write(buffer, size, offset);
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_nca_file_system_driver.h

@@ -0,0 +1,360 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_compression_common.h"
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+class CompressedStorage;
+class AesCtrCounterExtendedStorage;
+class IndirectStorage;
+class SparseStorage;
+
+struct NcaCryptoConfiguration;
+
+using KeyGenerationFunction = void (*)(void* dst_key, size_t dst_key_size, const void* src_key,
+                                       size_t src_key_size, s32 key_type);
+using VerifySign1Function = bool (*)(const void* sig, size_t sig_size, const void* data,
+                                     size_t data_size, u8 generation);
+
+struct NcaCryptoConfiguration {
+    static constexpr size_t Rsa2048KeyModulusSize = 2048 / 8;
+    static constexpr size_t Rsa2048KeyPublicExponentSize = 3;
+    static constexpr size_t Rsa2048KeyPrivateExponentSize = Rsa2048KeyModulusSize;
+
+    static constexpr size_t Aes128KeySize = 128 / 8;
+
+    static constexpr size_t Header1SignatureKeyGenerationMax = 1;
+
+    static constexpr s32 KeyAreaEncryptionKeyIndexCount = 3;
+    static constexpr s32 HeaderEncryptionKeyCount = 2;
+
+    static constexpr u8 KeyAreaEncryptionKeyIndexZeroKey = 0xFF;
+
+    static constexpr size_t KeyGenerationMax = 32;
+
+    const u8* header_1_sign_key_moduli[Header1SignatureKeyGenerationMax + 1];
+    u8 header_1_sign_key_public_exponent[Rsa2048KeyPublicExponentSize];
+    u8 key_area_encryption_key_source[KeyAreaEncryptionKeyIndexCount][Aes128KeySize];
+    u8 header_encryption_key_source[Aes128KeySize];
+    u8 header_encrypted_encryption_keys[HeaderEncryptionKeyCount][Aes128KeySize];
+    KeyGenerationFunction generate_key;
+    VerifySign1Function verify_sign1;
+    bool is_plaintext_header_available;
+    bool is_available_sw_key;
+};
+static_assert(std::is_trivial_v<NcaCryptoConfiguration>);
+
+struct NcaCompressionConfiguration {
+    GetDecompressorFunction get_decompressor;
+};
+static_assert(std::is_trivial_v<NcaCompressionConfiguration>);
+
+constexpr inline s32 KeyAreaEncryptionKeyCount =
+    NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount *
+    NcaCryptoConfiguration::KeyGenerationMax;
+
+enum class KeyType : s32 {
+    ZeroKey = -2,
+    InvalidKey = -1,
+    NcaHeaderKey1 = KeyAreaEncryptionKeyCount + 0,
+    NcaHeaderKey2 = KeyAreaEncryptionKeyCount + 1,
+    NcaExternalKey = KeyAreaEncryptionKeyCount + 2,
+    SaveDataDeviceUniqueMac = KeyAreaEncryptionKeyCount + 3,
+    SaveDataSeedUniqueMac = KeyAreaEncryptionKeyCount + 4,
+    SaveDataTransferMac = KeyAreaEncryptionKeyCount + 5,
+};
+
+constexpr inline bool IsInvalidKeyTypeValue(s32 key_type) {
+    return key_type < 0;
+}
+
+constexpr inline s32 GetKeyTypeValue(u8 key_index, u8 key_generation) {
+    if (key_index == NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexZeroKey) {
+        return static_cast<s32>(KeyType::ZeroKey);
+    }
+
+    if (key_index >= NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount) {
+        return static_cast<s32>(KeyType::InvalidKey);
+    }
+
+    return NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount * key_generation + key_index;
+}
+
+class NcaReader {
+    YUZU_NON_COPYABLE(NcaReader);
+    YUZU_NON_MOVEABLE(NcaReader);
+
+private:
+    NcaHeader m_header;
+    u8 m_decryption_keys[NcaHeader::DecryptionKey_Count][NcaCryptoConfiguration::Aes128KeySize];
+    VirtualFile m_body_storage;
+    VirtualFile m_header_storage;
+    u8 m_external_decryption_key[NcaCryptoConfiguration::Aes128KeySize];
+    bool m_is_software_aes_prioritized;
+    bool m_is_available_sw_key;
+    NcaHeader::EncryptionType m_header_encryption_type;
+    bool m_is_header_sign1_signature_valid;
+    GetDecompressorFunction m_get_decompressor;
+
+public:
+    NcaReader();
+    ~NcaReader();
+
+    Result Initialize(VirtualFile base_storage, const NcaCryptoConfiguration& crypto_cfg,
+                      const NcaCompressionConfiguration& compression_cfg);
+
+    VirtualFile GetSharedBodyStorage();
+    u32 GetMagic() const;
+    NcaHeader::DistributionType GetDistributionType() const;
+    NcaHeader::ContentType GetContentType() const;
+    u8 GetHeaderSign1KeyGeneration() const;
+    u8 GetKeyGeneration() const;
+    u8 GetKeyIndex() const;
+    u64 GetContentSize() const;
+    u64 GetProgramId() const;
+    u32 GetContentIndex() const;
+    u32 GetSdkAddonVersion() const;
+    void GetRightsId(u8* dst, size_t dst_size) const;
+    bool HasFsInfo(s32 index) const;
+    s32 GetFsCount() const;
+    const Hash& GetFsHeaderHash(s32 index) const;
+    void GetFsHeaderHash(Hash* dst, s32 index) const;
+    void GetFsInfo(NcaHeader::FsInfo* dst, s32 index) const;
+    u64 GetFsOffset(s32 index) const;
+    u64 GetFsEndOffset(s32 index) const;
+    u64 GetFsSize(s32 index) const;
+    void GetEncryptedKey(void* dst, size_t size) const;
+    const void* GetDecryptionKey(s32 index) const;
+    bool HasValidInternalKey() const;
+    bool HasInternalDecryptionKeyForAesHw() const;
+    bool IsSoftwareAesPrioritized() const;
+    void PrioritizeSoftwareAes();
+    bool IsAvailableSwKey() const;
+    bool HasExternalDecryptionKey() const;
+    const void* GetExternalDecryptionKey() const;
+    void SetExternalDecryptionKey(const void* src, size_t size);
+    void GetRawData(void* dst, size_t dst_size) const;
+    NcaHeader::EncryptionType GetEncryptionType() const;
+    Result ReadHeader(NcaFsHeader* dst, s32 index) const;
+
+    GetDecompressorFunction GetDecompressor() const;
+
+    bool GetHeaderSign1Valid() const;
+
+    void GetHeaderSign2(void* dst, size_t size) const;
+};
+
+class NcaFsHeaderReader {
+    YUZU_NON_COPYABLE(NcaFsHeaderReader);
+    YUZU_NON_MOVEABLE(NcaFsHeaderReader);
+
+private:
+    NcaFsHeader m_data;
+    s32 m_fs_index;
+
+public:
+    NcaFsHeaderReader() : m_fs_index(-1) {
+        std::memset(std::addressof(m_data), 0, sizeof(m_data));
+    }
+
+    Result Initialize(const NcaReader& reader, s32 index);
+    bool IsInitialized() const {
+        return m_fs_index >= 0;
+    }
+
+    void GetRawData(void* dst, size_t dst_size) const;
+
+    NcaFsHeader::HashData& GetHashData();
+    const NcaFsHeader::HashData& GetHashData() const;
+    u16 GetVersion() const;
+    s32 GetFsIndex() const;
+    NcaFsHeader::FsType GetFsType() const;
+    NcaFsHeader::HashType GetHashType() const;
+    NcaFsHeader::EncryptionType GetEncryptionType() const;
+    NcaPatchInfo& GetPatchInfo();
+    const NcaPatchInfo& GetPatchInfo() const;
+    const NcaAesCtrUpperIv GetAesCtrUpperIv() const;
+
+    bool IsSkipLayerHashEncryption() const;
+    Result GetHashTargetOffset(s64* out) const;
+
+    bool ExistsSparseLayer() const;
+    NcaSparseInfo& GetSparseInfo();
+    const NcaSparseInfo& GetSparseInfo() const;
+
+    bool ExistsCompressionLayer() const;
+    NcaCompressionInfo& GetCompressionInfo();
+    const NcaCompressionInfo& GetCompressionInfo() const;
+
+    bool ExistsPatchMetaHashLayer() const;
+    NcaMetaDataHashDataInfo& GetPatchMetaDataHashDataInfo();
+    const NcaMetaDataHashDataInfo& GetPatchMetaDataHashDataInfo() const;
+    NcaFsHeader::MetaDataHashType GetPatchMetaHashType() const;
+
+    bool ExistsSparseMetaHashLayer() const;
+    NcaMetaDataHashDataInfo& GetSparseMetaDataHashDataInfo();
+    const NcaMetaDataHashDataInfo& GetSparseMetaDataHashDataInfo() const;
+    NcaFsHeader::MetaDataHashType GetSparseMetaHashType() const;
+};
+
+class NcaFileSystemDriver {
+    YUZU_NON_COPYABLE(NcaFileSystemDriver);
+    YUZU_NON_MOVEABLE(NcaFileSystemDriver);
+
+public:
+    struct StorageContext {
+        bool open_raw_storage;
+        VirtualFile body_substorage;
+        std::shared_ptr<SparseStorage> current_sparse_storage;
+        VirtualFile sparse_storage_meta_storage;
+        std::shared_ptr<SparseStorage> original_sparse_storage;
+        void* external_current_sparse_storage;
+        void* external_original_sparse_storage;
+        VirtualFile aes_ctr_ex_storage_meta_storage;
+        VirtualFile aes_ctr_ex_storage_data_storage;
+        std::shared_ptr<AesCtrCounterExtendedStorage> aes_ctr_ex_storage;
+        VirtualFile indirect_storage_meta_storage;
+        std::shared_ptr<IndirectStorage> indirect_storage;
+        VirtualFile fs_data_storage;
+        VirtualFile compressed_storage_meta_storage;
+        std::shared_ptr<CompressedStorage> compressed_storage;
+
+        VirtualFile patch_layer_info_storage;
+        VirtualFile sparse_layer_info_storage;
+
+        VirtualFile external_original_storage;
+    };
+
+private:
+    enum class AlignmentStorageRequirement {
+        CacheBlockSize = 0,
+        None = 1,
+    };
+
+private:
+    std::shared_ptr<NcaReader> m_original_reader;
+    std::shared_ptr<NcaReader> m_reader;
+
+public:
+    static Result SetupFsHeaderReader(NcaFsHeaderReader* out, const NcaReader& reader,
+                                      s32 fs_index);
+
+public:
+    NcaFileSystemDriver(std::shared_ptr<NcaReader> reader) : m_original_reader(), m_reader(reader) {
+        ASSERT(m_reader != nullptr);
+    }
+
+    NcaFileSystemDriver(std::shared_ptr<NcaReader> original_reader,
+                        std::shared_ptr<NcaReader> reader)
+        : m_original_reader(original_reader), m_reader(reader) {
+        ASSERT(m_reader != nullptr);
+    }
+
+    Result OpenStorageWithContext(VirtualFile* out, NcaFsHeaderReader* out_header_reader,
+                                  s32 fs_index, StorageContext* ctx);
+
+    Result OpenStorage(VirtualFile* out, NcaFsHeaderReader* out_header_reader, s32 fs_index) {
+        // Create a storage context.
+        StorageContext ctx{};
+
+        // Open the storage.
+        R_RETURN(OpenStorageWithContext(out, out_header_reader, fs_index, std::addressof(ctx)));
+    }
+
+public:
+    Result CreateStorageByRawStorage(VirtualFile* out, const NcaFsHeaderReader* header_reader,
+                                     VirtualFile raw_storage, StorageContext* ctx);
+
+private:
+    Result OpenStorageImpl(VirtualFile* out, NcaFsHeaderReader* out_header_reader, s32 fs_index,
+                           StorageContext* ctx);
+
+    Result OpenIndirectableStorageAsOriginal(VirtualFile* out,
+                                             const NcaFsHeaderReader* header_reader,
+                                             StorageContext* ctx);
+
+    Result CreateBodySubStorage(VirtualFile* out, s64 offset, s64 size);
+
+    Result CreateAesCtrStorage(VirtualFile* out, VirtualFile base_storage, s64 offset,
+                               const NcaAesCtrUpperIv& upper_iv,
+                               AlignmentStorageRequirement alignment_storage_requirement);
+    Result CreateAesXtsStorage(VirtualFile* out, VirtualFile base_storage, s64 offset);
+
+    Result CreateSparseStorageMetaStorage(VirtualFile* out, VirtualFile base_storage, s64 offset,
+                                          const NcaAesCtrUpperIv& upper_iv,
+                                          const NcaSparseInfo& sparse_info);
+    Result CreateSparseStorageCore(std::shared_ptr<SparseStorage>* out, VirtualFile base_storage,
+                                   s64 base_size, VirtualFile meta_storage,
+                                   const NcaSparseInfo& sparse_info, bool external_info);
+    Result CreateSparseStorage(VirtualFile* out, s64* out_fs_data_offset,
+                               std::shared_ptr<SparseStorage>* out_sparse_storage,
+                               VirtualFile* out_meta_storage, s32 index,
+                               const NcaAesCtrUpperIv& upper_iv, const NcaSparseInfo& sparse_info);
+
+    Result CreateSparseStorageMetaStorageWithVerification(
+        VirtualFile* out, VirtualFile* out_verification, VirtualFile base_storage, s64 offset,
+        const NcaAesCtrUpperIv& upper_iv, const NcaSparseInfo& sparse_info,
+        const NcaMetaDataHashDataInfo& meta_data_hash_data_info);
+    Result CreateSparseStorageWithVerification(
+        VirtualFile* out, s64* out_fs_data_offset,
+        std::shared_ptr<SparseStorage>* out_sparse_storage, VirtualFile* out_meta_storage,
+        VirtualFile* out_verification, s32 index, const NcaAesCtrUpperIv& upper_iv,
+        const NcaSparseInfo& sparse_info, const NcaMetaDataHashDataInfo& meta_data_hash_data_info,
+        NcaFsHeader::MetaDataHashType meta_data_hash_type);
+
+    Result CreateAesCtrExStorageMetaStorage(VirtualFile* out, VirtualFile base_storage, s64 offset,
+                                            NcaFsHeader::EncryptionType encryption_type,
+                                            const NcaAesCtrUpperIv& upper_iv,
+                                            const NcaPatchInfo& patch_info);
+    Result CreateAesCtrExStorage(VirtualFile* out,
+                                 std::shared_ptr<AesCtrCounterExtendedStorage>* out_ext,
+                                 VirtualFile base_storage, VirtualFile meta_storage,
+                                 s64 counter_offset, const NcaAesCtrUpperIv& upper_iv,
+                                 const NcaPatchInfo& patch_info);
+
+    Result CreateIndirectStorageMetaStorage(VirtualFile* out, VirtualFile base_storage,
+                                            const NcaPatchInfo& patch_info);
+    Result CreateIndirectStorage(VirtualFile* out, std::shared_ptr<IndirectStorage>* out_ind,
+                                 VirtualFile base_storage, VirtualFile original_data_storage,
+                                 VirtualFile meta_storage, const NcaPatchInfo& patch_info);
+
+    Result CreatePatchMetaStorage(VirtualFile* out_aes_ctr_ex_meta, VirtualFile* out_indirect_meta,
+                                  VirtualFile* out_verification, VirtualFile base_storage,
+                                  s64 offset, const NcaAesCtrUpperIv& upper_iv,
+                                  const NcaPatchInfo& patch_info,
+                                  const NcaMetaDataHashDataInfo& meta_data_hash_data_info);
+
+    Result CreateSha256Storage(VirtualFile* out, VirtualFile base_storage,
+                               const NcaFsHeader::HashData::HierarchicalSha256Data& sha256_data);
+
+    Result CreateIntegrityVerificationStorage(
+        VirtualFile* out, VirtualFile base_storage,
+        const NcaFsHeader::HashData::IntegrityMetaInfo& meta_info);
+    Result CreateIntegrityVerificationStorageForMeta(
+        VirtualFile* out, VirtualFile* out_verification, VirtualFile base_storage, s64 offset,
+        const NcaMetaDataHashDataInfo& meta_data_hash_data_info);
+    Result CreateIntegrityVerificationStorageImpl(
+        VirtualFile* out, VirtualFile base_storage,
+        const NcaFsHeader::HashData::IntegrityMetaInfo& meta_info, s64 layer_info_offset,
+        int max_data_cache_entries, int max_hash_cache_entries, s8 buffer_level);
+
+    Result CreateRegionSwitchStorage(VirtualFile* out, const NcaFsHeaderReader* header_reader,
+                                     VirtualFile inside_storage, VirtualFile outside_storage);
+
+    Result CreateCompressedStorage(VirtualFile* out, std::shared_ptr<CompressedStorage>* out_cmp,
+                                   VirtualFile* out_meta, VirtualFile base_storage,
+                                   const NcaCompressionInfo& compression_info);
+
+public:
+    Result CreateCompressedStorage(VirtualFile* out, std::shared_ptr<CompressedStorage>* out_cmp,
+                                   VirtualFile* out_meta, VirtualFile base_storage,
+                                   const NcaCompressionInfo& compression_info,
+                                   GetDecompressorFunction get_decompressor);
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_nca_header.cpp

@@ -0,0 +1,20 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+
+namespace FileSys {
+
+u8 NcaHeader::GetProperKeyGeneration() const {
+    return std::max(this->key_generation, this->key_generation_2);
+}
+
+bool NcaPatchInfo::HasIndirectTable() const {
+    return this->indirect_size != 0;
+}
+
+bool NcaPatchInfo::HasAesCtrExTable() const {
+    return this->aes_ctr_ex_size != 0;
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_nca_header.h

@@ -0,0 +1,338 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/literals.h"
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_types.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+struct Hash {
+    static constexpr std::size_t Size = 256 / 8;
+    std::array<u8, Size> value;
+};
+static_assert(sizeof(Hash) == Hash::Size);
+static_assert(std::is_trivial_v<Hash>);
+
+using NcaDigest = Hash;
+
+struct NcaHeader {
+    enum class ContentType : u8 {
+        Program = 0,
+        Meta = 1,
+        Control = 2,
+        Manual = 3,
+        Data = 4,
+        PublicData = 5,
+
+        Start = Program,
+        End = PublicData,
+    };
+
+    enum class DistributionType : u8 {
+        Download = 0,
+        GameCard = 1,
+
+        Start = Download,
+        End = GameCard,
+    };
+
+    enum class EncryptionType : u8 {
+        Auto = 0,
+        None = 1,
+    };
+
+    enum DecryptionKey {
+        DecryptionKey_AesXts = 0,
+        DecryptionKey_AesXts1 = DecryptionKey_AesXts,
+        DecryptionKey_AesXts2 = 1,
+        DecryptionKey_AesCtr = 2,
+        DecryptionKey_AesCtrEx = 3,
+        DecryptionKey_AesCtrHw = 4,
+        DecryptionKey_Count,
+    };
+
+    struct FsInfo {
+        u32 start_sector;
+        u32 end_sector;
+        u32 hash_sectors;
+        u32 reserved;
+    };
+    static_assert(sizeof(FsInfo) == 0x10);
+    static_assert(std::is_trivial_v<FsInfo>);
+
+    static constexpr u32 Magic0 = Common::MakeMagic('N', 'C', 'A', '0');
+    static constexpr u32 Magic1 = Common::MakeMagic('N', 'C', 'A', '1');
+    static constexpr u32 Magic2 = Common::MakeMagic('N', 'C', 'A', '2');
+    static constexpr u32 Magic3 = Common::MakeMagic('N', 'C', 'A', '3');
+
+    static constexpr u32 Magic = Magic3;
+
+    static constexpr std::size_t Size = 1_KiB;
+    static constexpr s32 FsCountMax = 4;
+    static constexpr std::size_t HeaderSignCount = 2;
+    static constexpr std::size_t HeaderSignSize = 0x100;
+    static constexpr std::size_t EncryptedKeyAreaSize = 0x100;
+    static constexpr std::size_t SectorSize = 0x200;
+    static constexpr std::size_t SectorShift = 9;
+    static constexpr std::size_t RightsIdSize = 0x10;
+    static constexpr std::size_t XtsBlockSize = 0x200;
+    static constexpr std::size_t CtrBlockSize = 0x10;
+
+    static_assert(SectorSize == (1 << SectorShift));
+
+    // Data members.
+    std::array<u8, HeaderSignSize> header_sign_1;
+    std::array<u8, HeaderSignSize> header_sign_2;
+    u32 magic;
+    DistributionType distribution_type;
+    ContentType content_type;
+    u8 key_generation;
+    u8 key_index;
+    u64 content_size;
+    u64 program_id;
+    u32 content_index;
+    u32 sdk_addon_version;
+    u8 key_generation_2;
+    u8 header1_signature_key_generation;
+    std::array<u8, 2> reserved_222;
+    std::array<u32, 3> reserved_224;
+    std::array<u8, RightsIdSize> rights_id;
+    std::array<FsInfo, FsCountMax> fs_info;
+    std::array<Hash, FsCountMax> fs_header_hash;
+    std::array<u8, EncryptedKeyAreaSize> encrypted_key_area;
+
+    static constexpr u64 SectorToByte(u32 sector) {
+        return static_cast<u64>(sector) << SectorShift;
+    }
+
+    static constexpr u32 ByteToSector(u64 byte) {
+        return static_cast<u32>(byte >> SectorShift);
+    }
+
+    u8 GetProperKeyGeneration() const;
+};
+static_assert(sizeof(NcaHeader) == NcaHeader::Size);
+static_assert(std::is_trivial_v<NcaHeader>);
+
+struct NcaBucketInfo {
+    static constexpr size_t HeaderSize = 0x10;
+    Int64 offset;
+    Int64 size;
+    std::array<u8, HeaderSize> header;
+};
+static_assert(std::is_trivial_v<NcaBucketInfo>);
+
+struct NcaPatchInfo {
+    static constexpr size_t Size = 0x40;
+    static constexpr size_t Offset = 0x100;
+
+    Int64 indirect_offset;
+    Int64 indirect_size;
+    std::array<u8, NcaBucketInfo::HeaderSize> indirect_header;
+    Int64 aes_ctr_ex_offset;
+    Int64 aes_ctr_ex_size;
+    std::array<u8, NcaBucketInfo::HeaderSize> aes_ctr_ex_header;
+
+    bool HasIndirectTable() const;
+    bool HasAesCtrExTable() const;
+};
+static_assert(std::is_trivial_v<NcaPatchInfo>);
+
+union NcaAesCtrUpperIv {
+    u64 value;
+    struct {
+        u32 generation;
+        u32 secure_value;
+    } part;
+};
+static_assert(std::is_trivial_v<NcaAesCtrUpperIv>);
+
+struct NcaSparseInfo {
+    NcaBucketInfo bucket;
+    Int64 physical_offset;
+    u16 generation;
+    std::array<u8, 6> reserved;
+
+    s64 GetPhysicalSize() const {
+        return this->bucket.offset + this->bucket.size;
+    }
+
+    u32 GetGeneration() const {
+        return static_cast<u32>(this->generation) << 16;
+    }
+
+    const NcaAesCtrUpperIv MakeAesCtrUpperIv(NcaAesCtrUpperIv upper_iv) const {
+        NcaAesCtrUpperIv sparse_upper_iv = upper_iv;
+        sparse_upper_iv.part.generation = this->GetGeneration();
+        return sparse_upper_iv;
+    }
+};
+static_assert(std::is_trivial_v<NcaSparseInfo>);
+
+struct NcaCompressionInfo {
+    NcaBucketInfo bucket;
+    std::array<u8, 8> resreved;
+};
+static_assert(std::is_trivial_v<NcaCompressionInfo>);
+
+struct NcaMetaDataHashDataInfo {
+    Int64 offset;
+    Int64 size;
+    Hash hash;
+};
+static_assert(std::is_trivial_v<NcaMetaDataHashDataInfo>);
+
+struct NcaFsHeader {
+    static constexpr size_t Size = 0x200;
+    static constexpr size_t HashDataOffset = 0x8;
+
+    struct Region {
+        Int64 offset;
+        Int64 size;
+    };
+    static_assert(std::is_trivial_v<Region>);
+
+    enum class FsType : u8 {
+        RomFs = 0,
+        PartitionFs = 1,
+    };
+
+    enum class EncryptionType : u8 {
+        Auto = 0,
+        None = 1,
+        AesXts = 2,
+        AesCtr = 3,
+        AesCtrEx = 4,
+        AesCtrSkipLayerHash = 5,
+        AesCtrExSkipLayerHash = 6,
+    };
+
+    enum class HashType : u8 {
+        Auto = 0,
+        None = 1,
+        HierarchicalSha256Hash = 2,
+        HierarchicalIntegrityHash = 3,
+        AutoSha3 = 4,
+        HierarchicalSha3256Hash = 5,
+        HierarchicalIntegritySha3Hash = 6,
+    };
+
+    enum class MetaDataHashType : u8 {
+        None = 0,
+        HierarchicalIntegrity = 1,
+    };
+
+    union HashData {
+        struct HierarchicalSha256Data {
+            static constexpr size_t HashLayerCountMax = 5;
+            static const size_t MasterHashOffset;
+
+            Hash fs_data_master_hash;
+            s32 hash_block_size;
+            s32 hash_layer_count;
+            std::array<Region, HashLayerCountMax> hash_layer_region;
+        } hierarchical_sha256_data;
+        static_assert(std::is_trivial_v<HierarchicalSha256Data>);
+
+        struct IntegrityMetaInfo {
+            static const size_t MasterHashOffset;
+
+            u32 magic;
+            u32 version;
+            u32 master_hash_size;
+
+            struct LevelHashInfo {
+                u32 max_layers;
+
+                struct HierarchicalIntegrityVerificationLevelInformation {
+                    static constexpr size_t IntegrityMaxLayerCount = 7;
+                    Int64 offset;
+                    Int64 size;
+                    s32 block_order;
+                    std::array<u8, 4> reserved;
+                };
+                std::array<
+                    HierarchicalIntegrityVerificationLevelInformation,
+                    HierarchicalIntegrityVerificationLevelInformation::IntegrityMaxLayerCount - 1>
+                    info;
+
+                struct SignatureSalt {
+                    static constexpr size_t Size = 0x20;
+                    std::array<u8, Size> value;
+                };
+                SignatureSalt seed;
+            } level_hash_info;
+
+            Hash master_hash;
+        } integrity_meta_info;
+        static_assert(std::is_trivial_v<IntegrityMetaInfo>);
+
+        std::array<u8, NcaPatchInfo::Offset - HashDataOffset> padding;
+    };
+
+    u16 version;
+    FsType fs_type;
+    HashType hash_type;
+    EncryptionType encryption_type;
+    MetaDataHashType meta_data_hash_type;
+    std::array<u8, 2> reserved;
+    HashData hash_data;
+    NcaPatchInfo patch_info;
+    NcaAesCtrUpperIv aes_ctr_upper_iv;
+    NcaSparseInfo sparse_info;
+    NcaCompressionInfo compression_info;
+    NcaMetaDataHashDataInfo meta_data_hash_data_info;
+    std::array<u8, 0x30> pad;
+
+    bool IsSkipLayerHashEncryption() const {
+        return this->encryption_type == EncryptionType::AesCtrSkipLayerHash ||
+               this->encryption_type == EncryptionType::AesCtrExSkipLayerHash;
+    }
+
+    Result GetHashTargetOffset(s64* out) const {
+        switch (this->hash_type) {
+        case HashType::HierarchicalIntegrityHash:
+        case HashType::HierarchicalIntegritySha3Hash:
+            *out = this->hash_data.integrity_meta_info.level_hash_info
+                       .info[this->hash_data.integrity_meta_info.level_hash_info.max_layers - 2]
+                       .offset;
+            R_SUCCEED();
+        case HashType::HierarchicalSha256Hash:
+        case HashType::HierarchicalSha3256Hash:
+            *out =
+                this->hash_data.hierarchical_sha256_data
+                    .hash_layer_region[this->hash_data.hierarchical_sha256_data.hash_layer_count -
+                                       1]
+                    .offset;
+            R_SUCCEED();
+        default:
+            R_THROW(ResultInvalidNcaFsHeader);
+        }
+    }
+};
+static_assert(sizeof(NcaFsHeader) == NcaFsHeader::Size);
+static_assert(std::is_trivial_v<NcaFsHeader>);
+static_assert(offsetof(NcaFsHeader, patch_info) == NcaPatchInfo::Offset);
+
+inline constexpr const size_t NcaFsHeader::HashData::HierarchicalSha256Data::MasterHashOffset =
+    offsetof(NcaFsHeader, hash_data.hierarchical_sha256_data.fs_data_master_hash);
+inline constexpr const size_t NcaFsHeader::HashData::IntegrityMetaInfo::MasterHashOffset =
+    offsetof(NcaFsHeader, hash_data.integrity_meta_info.master_hash);
+
+struct NcaMetaDataHashData {
+    s64 layer_info_offset;
+    NcaFsHeader::HashData::IntegrityMetaInfo integrity_meta_info;
+};
+static_assert(sizeof(NcaMetaDataHashData) ==
+              sizeof(NcaFsHeader::HashData::IntegrityMetaInfo) + sizeof(s64));
+static_assert(std::is_trivial_v<NcaMetaDataHashData>);
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_nca_reader.cpp

@@ -0,0 +1,542 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_aes_xts_storage.h"
+#include "core/file_sys/fssystem/fssystem_nca_file_system_driver.h"
+#include "core/file_sys/vfs_offset.h"
+
+namespace FileSys {
+
+namespace {
+
+constexpr inline u32 SdkAddonVersionMin = 0x000B0000;
+constexpr inline size_t Aes128KeySize = 0x10;
+constexpr const std::array<u8, Aes128KeySize> ZeroKey{};
+
+constexpr Result CheckNcaMagic(u32 magic) {
+    // Verify the magic is not a deprecated one.
+    R_UNLESS(magic != NcaHeader::Magic0, ResultUnsupportedSdkVersion);
+    R_UNLESS(magic != NcaHeader::Magic1, ResultUnsupportedSdkVersion);
+    R_UNLESS(magic != NcaHeader::Magic2, ResultUnsupportedSdkVersion);
+
+    // Verify the magic is the current one.
+    R_UNLESS(magic == NcaHeader::Magic3, ResultInvalidNcaSignature);
+
+    R_SUCCEED();
+}
+
+} // namespace
+
+NcaReader::NcaReader()
+    : m_body_storage(), m_header_storage(), m_is_software_aes_prioritized(false),
+      m_is_available_sw_key(false), m_header_encryption_type(NcaHeader::EncryptionType::Auto),
+      m_get_decompressor() {
+    std::memset(std::addressof(m_header), 0, sizeof(m_header));
+    std::memset(std::addressof(m_decryption_keys), 0, sizeof(m_decryption_keys));
+    std::memset(std::addressof(m_external_decryption_key), 0, sizeof(m_external_decryption_key));
+}
+
+NcaReader::~NcaReader() {}
+
+Result NcaReader::Initialize(VirtualFile base_storage, const NcaCryptoConfiguration& crypto_cfg,
+                             const NcaCompressionConfiguration& compression_cfg) {
+    // Validate preconditions.
+    ASSERT(base_storage != nullptr);
+    ASSERT(m_body_storage == nullptr);
+
+    // Create the work header storage storage.
+    VirtualFile work_header_storage;
+
+    // We need to be able to generate keys.
+    R_UNLESS(crypto_cfg.generate_key != nullptr, ResultInvalidArgument);
+
+    // Generate keys for header.
+    using AesXtsStorageForNcaHeader = AesXtsStorage;
+
+    constexpr const s32 HeaderKeyTypeValues[NcaCryptoConfiguration::HeaderEncryptionKeyCount] = {
+        static_cast<s32>(KeyType::NcaHeaderKey1),
+        static_cast<s32>(KeyType::NcaHeaderKey2),
+    };
+
+    u8 header_decryption_keys[NcaCryptoConfiguration::HeaderEncryptionKeyCount]
+                             [NcaCryptoConfiguration::Aes128KeySize];
+    for (size_t i = 0; i < NcaCryptoConfiguration::HeaderEncryptionKeyCount; i++) {
+        crypto_cfg.generate_key(header_decryption_keys[i], AesXtsStorageForNcaHeader::KeySize,
+                                crypto_cfg.header_encrypted_encryption_keys[i],
+                                AesXtsStorageForNcaHeader::KeySize, HeaderKeyTypeValues[i]);
+    }
+
+    // Create the header storage.
+    const u8 header_iv[AesXtsStorageForNcaHeader::IvSize] = {};
+    work_header_storage = std::make_unique<AesXtsStorageForNcaHeader>(
+        base_storage, header_decryption_keys[0], header_decryption_keys[1],
+        AesXtsStorageForNcaHeader::KeySize, header_iv, AesXtsStorageForNcaHeader::IvSize,
+        NcaHeader::XtsBlockSize);
+
+    // Check that we successfully created the storage.
+    R_UNLESS(work_header_storage != nullptr, ResultAllocationMemoryFailedInNcaReaderA);
+
+    // Read the header.
+    work_header_storage->ReadObject(std::addressof(m_header), 0);
+
+    // Validate the magic.
+    if (const Result magic_result = CheckNcaMagic(m_header.magic); R_FAILED(magic_result)) {
+        // Try to use a plaintext header.
+        base_storage->ReadObject(std::addressof(m_header), 0);
+        R_UNLESS(R_SUCCEEDED(CheckNcaMagic(m_header.magic)), magic_result);
+
+        // Configure to use the plaintext header.
+        auto base_storage_size = base_storage->GetSize();
+        work_header_storage = std::make_shared<OffsetVfsFile>(base_storage, base_storage_size, 0);
+        R_UNLESS(work_header_storage != nullptr, ResultAllocationMemoryFailedInNcaReaderA);
+
+        // Set encryption type as plaintext.
+        m_header_encryption_type = NcaHeader::EncryptionType::None;
+    }
+
+    // Validate the fixed key signature.
+    if (m_header.header1_signature_key_generation >
+        NcaCryptoConfiguration::Header1SignatureKeyGenerationMax) {
+        LOG_CRITICAL(Frontend,
+                     "NcaCryptoConfiguration::Header1SignatureKeyGenerationMax = {}, "
+                     "m_header.header1_signature_key_generation = {}",
+                     NcaCryptoConfiguration::Header1SignatureKeyGenerationMax,
+                     m_header.header1_signature_key_generation);
+    }
+
+    R_UNLESS(m_header.header1_signature_key_generation <=
+                 NcaCryptoConfiguration::Header1SignatureKeyGenerationMax,
+             ResultInvalidNcaHeader1SignatureKeyGeneration);
+
+    // Verify the header sign1.
+    if (crypto_cfg.verify_sign1 != nullptr) {
+        const u8* sig = m_header.header_sign_1.data();
+        const size_t sig_size = NcaHeader::HeaderSignSize;
+        const u8* msg =
+            static_cast<const u8*>(static_cast<const void*>(std::addressof(m_header.magic)));
+        const size_t msg_size =
+            NcaHeader::Size - NcaHeader::HeaderSignSize * NcaHeader::HeaderSignCount;
+
+        m_is_header_sign1_signature_valid = crypto_cfg.verify_sign1(
+            sig, sig_size, msg, msg_size, m_header.header1_signature_key_generation);
+
+        if (!m_is_header_sign1_signature_valid) {
+            LOG_WARNING(Common_Filesystem, "Invalid NCA header sign1");
+        }
+    }
+
+    // Validate the sdk version.
+    R_UNLESS(m_header.sdk_addon_version >= SdkAddonVersionMin, ResultUnsupportedSdkVersion);
+
+    // Validate the key index.
+    R_UNLESS(m_header.key_index < NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount ||
+                 m_header.key_index == NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexZeroKey,
+             ResultInvalidNcaKeyIndex);
+
+    // Check if we have a rights id.
+    constexpr const std::array<u8, NcaHeader::RightsIdSize> ZeroRightsId{};
+    if (std::memcmp(ZeroRightsId.data(), m_header.rights_id.data(), NcaHeader::RightsIdSize) == 0) {
+        // If we don't, then we don't have an external key, so we need to generate decryption keys.
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesCtr], Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesCtr * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesXts1], Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesXts1 * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesXts2], Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesXts2 * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesCtrEx], Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesCtrEx * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+
+        // Copy the hardware speed emulation key.
+        std::memcpy(m_decryption_keys[NcaHeader::DecryptionKey_AesCtrHw],
+                    m_header.encrypted_key_area.data() +
+                        NcaHeader::DecryptionKey_AesCtrHw * Aes128KeySize,
+                    Aes128KeySize);
+    }
+
+    // Clear the external decryption key.
+    std::memset(m_external_decryption_key, 0, sizeof(m_external_decryption_key));
+
+    // Set software key availability.
+    m_is_available_sw_key = crypto_cfg.is_available_sw_key;
+
+    // Set our decompressor function getter.
+    m_get_decompressor = compression_cfg.get_decompressor;
+
+    // Set our storages.
+    m_header_storage = std::move(work_header_storage);
+    m_body_storage = std::move(base_storage);
+
+    R_SUCCEED();
+}
+
+VirtualFile NcaReader::GetSharedBodyStorage() {
+    ASSERT(m_body_storage != nullptr);
+    return m_body_storage;
+}
+
+u32 NcaReader::GetMagic() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.magic;
+}
+
+NcaHeader::DistributionType NcaReader::GetDistributionType() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.distribution_type;
+}
+
+NcaHeader::ContentType NcaReader::GetContentType() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.content_type;
+}
+
+u8 NcaReader::GetHeaderSign1KeyGeneration() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.header1_signature_key_generation;
+}
+
+u8 NcaReader::GetKeyGeneration() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.GetProperKeyGeneration();
+}
+
+u8 NcaReader::GetKeyIndex() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.key_index;
+}
+
+u64 NcaReader::GetContentSize() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.content_size;
+}
+
+u64 NcaReader::GetProgramId() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.program_id;
+}
+
+u32 NcaReader::GetContentIndex() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.content_index;
+}
+
+u32 NcaReader::GetSdkAddonVersion() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.sdk_addon_version;
+}
+
+void NcaReader::GetRightsId(u8* dst, size_t dst_size) const {
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size >= NcaHeader::RightsIdSize);
+
+    std::memcpy(dst, m_header.rights_id.data(), NcaHeader::RightsIdSize);
+}
+
+bool NcaReader::HasFsInfo(s32 index) const {
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return m_header.fs_info[index].start_sector != 0 || m_header.fs_info[index].end_sector != 0;
+}
+
+s32 NcaReader::GetFsCount() const {
+    ASSERT(m_body_storage != nullptr);
+    for (s32 i = 0; i < NcaHeader::FsCountMax; i++) {
+        if (!this->HasFsInfo(i)) {
+            return i;
+        }
+    }
+    return NcaHeader::FsCountMax;
+}
+
+const Hash& NcaReader::GetFsHeaderHash(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return m_header.fs_header_hash[index];
+}
+
+void NcaReader::GetFsHeaderHash(Hash* dst, s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    ASSERT(dst != nullptr);
+    std::memcpy(dst, std::addressof(m_header.fs_header_hash[index]), sizeof(*dst));
+}
+
+void NcaReader::GetFsInfo(NcaHeader::FsInfo* dst, s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    ASSERT(dst != nullptr);
+    std::memcpy(dst, std::addressof(m_header.fs_info[index]), sizeof(*dst));
+}
+
+u64 NcaReader::GetFsOffset(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return NcaHeader::SectorToByte(m_header.fs_info[index].start_sector);
+}
+
+u64 NcaReader::GetFsEndOffset(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return NcaHeader::SectorToByte(m_header.fs_info[index].end_sector);
+}
+
+u64 NcaReader::GetFsSize(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return NcaHeader::SectorToByte(m_header.fs_info[index].end_sector -
+                                   m_header.fs_info[index].start_sector);
+}
+
+void NcaReader::GetEncryptedKey(void* dst, size_t size) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(dst != nullptr);
+    ASSERT(size >= NcaHeader::EncryptedKeyAreaSize);
+
+    std::memcpy(dst, m_header.encrypted_key_area.data(), NcaHeader::EncryptedKeyAreaSize);
+}
+
+const void* NcaReader::GetDecryptionKey(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::DecryptionKey_Count);
+    return m_decryption_keys[index];
+}
+
+bool NcaReader::HasValidInternalKey() const {
+    for (s32 i = 0; i < NcaHeader::DecryptionKey_Count; i++) {
+        if (std::memcmp(ZeroKey.data(), m_header.encrypted_key_area.data() + i * Aes128KeySize,
+                        Aes128KeySize) != 0) {
+            return true;
+        }
+    }
+    return false;
+}
+
+bool NcaReader::HasInternalDecryptionKeyForAesHw() const {
+    return std::memcmp(ZeroKey.data(), this->GetDecryptionKey(NcaHeader::DecryptionKey_AesCtrHw),
+                       Aes128KeySize) != 0;
+}
+
+bool NcaReader::IsSoftwareAesPrioritized() const {
+    return m_is_software_aes_prioritized;
+}
+
+void NcaReader::PrioritizeSoftwareAes() {
+    m_is_software_aes_prioritized = true;
+}
+
+bool NcaReader::IsAvailableSwKey() const {
+    return m_is_available_sw_key;
+}
+
+bool NcaReader::HasExternalDecryptionKey() const {
+    return std::memcmp(ZeroKey.data(), this->GetExternalDecryptionKey(), Aes128KeySize) != 0;
+}
+
+const void* NcaReader::GetExternalDecryptionKey() const {
+    return m_external_decryption_key;
+}
+
+void NcaReader::SetExternalDecryptionKey(const void* src, size_t size) {
+    ASSERT(src != nullptr);
+    ASSERT(size == sizeof(m_external_decryption_key));
+
+    std::memcpy(m_external_decryption_key, src, sizeof(m_external_decryption_key));
+}
+
+void NcaReader::GetRawData(void* dst, size_t dst_size) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size >= sizeof(NcaHeader));
+
+    std::memcpy(dst, std::addressof(m_header), sizeof(NcaHeader));
+}
+
+GetDecompressorFunction NcaReader::GetDecompressor() const {
+    ASSERT(m_get_decompressor != nullptr);
+    return m_get_decompressor;
+}
+
+NcaHeader::EncryptionType NcaReader::GetEncryptionType() const {
+    return m_header_encryption_type;
+}
+
+Result NcaReader::ReadHeader(NcaFsHeader* dst, s32 index) const {
+    ASSERT(dst != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+
+    const s64 offset = sizeof(NcaHeader) + sizeof(NcaFsHeader) * index;
+    m_header_storage->ReadObject(dst, offset);
+
+    R_SUCCEED();
+}
+
+bool NcaReader::GetHeaderSign1Valid() const {
+    return m_is_header_sign1_signature_valid;
+}
+
+void NcaReader::GetHeaderSign2(void* dst, size_t size) const {
+    ASSERT(dst != nullptr);
+    ASSERT(size == NcaHeader::HeaderSignSize);
+
+    std::memcpy(dst, m_header.header_sign_2.data(), size);
+}
+
+Result NcaFsHeaderReader::Initialize(const NcaReader& reader, s32 index) {
+    // Reset ourselves to uninitialized.
+    m_fs_index = -1;
+
+    // Read the header.
+    R_TRY(reader.ReadHeader(std::addressof(m_data), index));
+
+    // Set our index.
+    m_fs_index = index;
+    R_SUCCEED();
+}
+
+void NcaFsHeaderReader::GetRawData(void* dst, size_t dst_size) const {
+    ASSERT(this->IsInitialized());
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size >= sizeof(NcaFsHeader));
+
+    std::memcpy(dst, std::addressof(m_data), sizeof(NcaFsHeader));
+}
+
+NcaFsHeader::HashData& NcaFsHeaderReader::GetHashData() {
+    ASSERT(this->IsInitialized());
+    return m_data.hash_data;
+}
+
+const NcaFsHeader::HashData& NcaFsHeaderReader::GetHashData() const {
+    ASSERT(this->IsInitialized());
+    return m_data.hash_data;
+}
+
+u16 NcaFsHeaderReader::GetVersion() const {
+    ASSERT(this->IsInitialized());
+    return m_data.version;
+}
+
+s32 NcaFsHeaderReader::GetFsIndex() const {
+    ASSERT(this->IsInitialized());
+    return m_fs_index;
+}
+
+NcaFsHeader::FsType NcaFsHeaderReader::GetFsType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.fs_type;
+}
+
+NcaFsHeader::HashType NcaFsHeaderReader::GetHashType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.hash_type;
+}
+
+NcaFsHeader::EncryptionType NcaFsHeaderReader::GetEncryptionType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.encryption_type;
+}
+
+NcaPatchInfo& NcaFsHeaderReader::GetPatchInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.patch_info;
+}
+
+const NcaPatchInfo& NcaFsHeaderReader::GetPatchInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.patch_info;
+}
+
+const NcaAesCtrUpperIv NcaFsHeaderReader::GetAesCtrUpperIv() const {
+    ASSERT(this->IsInitialized());
+    return m_data.aes_ctr_upper_iv;
+}
+
+bool NcaFsHeaderReader::IsSkipLayerHashEncryption() const {
+    ASSERT(this->IsInitialized());
+    return m_data.IsSkipLayerHashEncryption();
+}
+
+Result NcaFsHeaderReader::GetHashTargetOffset(s64* out) const {
+    ASSERT(out != nullptr);
+    ASSERT(this->IsInitialized());
+
+    R_RETURN(m_data.GetHashTargetOffset(out));
+}
+
+bool NcaFsHeaderReader::ExistsSparseLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.sparse_info.generation != 0;
+}
+
+NcaSparseInfo& NcaFsHeaderReader::GetSparseInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.sparse_info;
+}
+
+const NcaSparseInfo& NcaFsHeaderReader::GetSparseInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.sparse_info;
+}
+
+bool NcaFsHeaderReader::ExistsCompressionLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.compression_info.bucket.offset != 0 && m_data.compression_info.bucket.size != 0;
+}
+
+NcaCompressionInfo& NcaFsHeaderReader::GetCompressionInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.compression_info;
+}
+
+const NcaCompressionInfo& NcaFsHeaderReader::GetCompressionInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.compression_info;
+}
+
+bool NcaFsHeaderReader::ExistsPatchMetaHashLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info.size != 0 && this->GetPatchInfo().HasIndirectTable();
+}
+
+NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetPatchMetaDataHashDataInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+const NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetPatchMetaDataHashDataInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+NcaFsHeader::MetaDataHashType NcaFsHeaderReader::GetPatchMetaHashType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_type;
+}
+
+bool NcaFsHeaderReader::ExistsSparseMetaHashLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info.size != 0 && this->ExistsSparseLayer();
+}
+
+NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetSparseMetaDataHashDataInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+const NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetSparseMetaDataHashDataInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+NcaFsHeader::MetaDataHashType NcaFsHeaderReader::GetSparseMetaHashType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_type;
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_pooled_buffer.cpp

@@ -0,0 +1,61 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+namespace {
+
+constexpr size_t HeapBlockSize = BufferPoolAlignment;
+static_assert(HeapBlockSize == 4_KiB);
+
+// A heap block is 4KiB. An order is a power of two.
+// This gives blocks of the order 32KiB, 512KiB, 4MiB.
+constexpr s32 HeapOrderMax = 7;
+constexpr s32 HeapOrderMaxForLarge = HeapOrderMax + 3;
+
+constexpr size_t HeapAllocatableSizeMax = HeapBlockSize * (static_cast<size_t>(1) << HeapOrderMax);
+constexpr size_t HeapAllocatableSizeMaxForLarge =
+    HeapBlockSize * (static_cast<size_t>(1) << HeapOrderMaxForLarge);
+
+} // namespace
+
+size_t PooledBuffer::GetAllocatableSizeMaxCore(bool large) {
+    return large ? HeapAllocatableSizeMaxForLarge : HeapAllocatableSizeMax;
+}
+
+void PooledBuffer::AllocateCore(size_t ideal_size, size_t required_size, bool large) {
+    // Ensure preconditions.
+    ASSERT(m_buffer == nullptr);
+
+    // Check that we can allocate this size.
+    ASSERT(required_size <= GetAllocatableSizeMaxCore(large));
+
+    const size_t target_size =
+        std::min(std::max(ideal_size, required_size), GetAllocatableSizeMaxCore(large));
+
+    // Dummy implementation for allocate.
+    if (target_size > 0) {
+        m_buffer =
+            reinterpret_cast<char*>(::operator new(target_size, std::align_val_t{HeapBlockSize}));
+        m_size = target_size;
+
+        // Ensure postconditions.
+        ASSERT(m_buffer != nullptr);
+    }
+}
+
+void PooledBuffer::Shrink(size_t ideal_size) {
+    ASSERT(ideal_size <= GetAllocatableSizeMaxCore(true));
+
+    // Shrinking to zero means that we have no buffer.
+    if (ideal_size == 0) {
+        ::operator delete(m_buffer, std::align_val_t{HeapBlockSize});
+        m_buffer = nullptr;
+        m_size = ideal_size;
+    }
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_pooled_buffer.h

@@ -0,0 +1,96 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/literals.h"
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+constexpr inline size_t BufferPoolAlignment = 4_KiB;
+constexpr inline size_t BufferPoolWorkSize = 320;
+
+class PooledBuffer {
+    YUZU_NON_COPYABLE(PooledBuffer);
+
+private:
+    char* m_buffer;
+    size_t m_size;
+
+private:
+    static size_t GetAllocatableSizeMaxCore(bool large);
+
+public:
+    static size_t GetAllocatableSizeMax() {
+        return GetAllocatableSizeMaxCore(false);
+    }
+    static size_t GetAllocatableParticularlyLargeSizeMax() {
+        return GetAllocatableSizeMaxCore(true);
+    }
+
+private:
+    void Swap(PooledBuffer& rhs) {
+        std::swap(m_buffer, rhs.m_buffer);
+        std::swap(m_size, rhs.m_size);
+    }
+
+public:
+    // Constructor/Destructor.
+    constexpr PooledBuffer() : m_buffer(), m_size() {}
+
+    PooledBuffer(size_t ideal_size, size_t required_size) : m_buffer(), m_size() {
+        this->Allocate(ideal_size, required_size);
+    }
+
+    ~PooledBuffer() {
+        this->Deallocate();
+    }
+
+    // Move and assignment.
+    explicit PooledBuffer(PooledBuffer&& rhs) : m_buffer(rhs.m_buffer), m_size(rhs.m_size) {
+        rhs.m_buffer = nullptr;
+        rhs.m_size = 0;
+    }
+
+    PooledBuffer& operator=(PooledBuffer&& rhs) {
+        PooledBuffer(std::move(rhs)).Swap(*this);
+        return *this;
+    }
+
+    // Allocation API.
+    void Allocate(size_t ideal_size, size_t required_size) {
+        return this->AllocateCore(ideal_size, required_size, false);
+    }
+
+    void AllocateParticularlyLarge(size_t ideal_size, size_t required_size) {
+        return this->AllocateCore(ideal_size, required_size, true);
+    }
+
+    void Shrink(size_t ideal_size);
+
+    void Deallocate() {
+        // Shrink the buffer to empty.
+        this->Shrink(0);
+        ASSERT(m_buffer == nullptr);
+    }
+
+    char* GetBuffer() const {
+        ASSERT(m_buffer != nullptr);
+        return m_buffer;
+    }
+
+    size_t GetSize() const {
+        ASSERT(m_buffer != nullptr);
+        return m_size;
+    }
+
+private:
+    void AllocateCore(size_t ideal_size, size_t required_size, bool large);
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_sparse_storage.cpp

@@ -0,0 +1,40 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_sparse_storage.h"
+
+namespace FileSys {
+
+size_t SparseStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Validate preconditions.
+    ASSERT(offset >= 0);
+    ASSERT(this->IsInitialized());
+    ASSERT(buffer != nullptr);
+
+    // Allow zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    SparseStorage* self = const_cast<SparseStorage*>(this);
+
+    if (self->GetEntryTable().IsEmpty()) {
+        BucketTree::Offsets table_offsets;
+        ASSERT(R_SUCCEEDED(self->GetEntryTable().GetOffsets(std::addressof(table_offsets))));
+        ASSERT(table_offsets.IsInclude(offset, size));
+
+        std::memset(buffer, 0, size);
+    } else {
+        self->OperatePerEntry<false, true>(
+            offset, size,
+            [=](VirtualFile storage, s64 data_offset, s64 cur_offset, s64 cur_size) -> Result {
+                storage->Read(reinterpret_cast<u8*>(buffer) + (cur_offset - offset),
+                              static_cast<size_t>(cur_size), data_offset);
+                R_SUCCEED();
+            });
+    }
+
+    return size;
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_sparse_storage.h

@@ -0,0 +1,73 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_indirect_storage.h"
+
+namespace FileSys {
+
+class SparseStorage : public IndirectStorage {
+    YUZU_NON_COPYABLE(SparseStorage);
+    YUZU_NON_MOVEABLE(SparseStorage);
+
+private:
+    class ZeroStorage : public IReadOnlyStorage {
+    public:
+        ZeroStorage() {}
+        virtual ~ZeroStorage() {}
+
+        virtual size_t GetSize() const override {
+            return std::numeric_limits<size_t>::max();
+        }
+
+        virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+            ASSERT(offset >= 0);
+            ASSERT(buffer != nullptr || size == 0);
+
+            if (size > 0) {
+                std::memset(buffer, 0, size);
+            }
+
+            return size;
+        }
+    };
+
+private:
+    VirtualFile m_zero_storage;
+
+public:
+    SparseStorage() : IndirectStorage(), m_zero_storage(std::make_shared<ZeroStorage>()) {}
+    virtual ~SparseStorage() {}
+
+    using IndirectStorage::Initialize;
+
+    void Initialize(s64 end_offset) {
+        this->GetEntryTable().Initialize(NodeSize, end_offset);
+        this->SetZeroStorage();
+    }
+
+    void SetDataStorage(VirtualFile storage) {
+        ASSERT(this->IsInitialized());
+
+        this->SetStorage(0, storage);
+        this->SetZeroStorage();
+    }
+
+    template <typename T>
+    void SetDataStorage(T storage, s64 offset, s64 size) {
+        ASSERT(this->IsInitialized());
+
+        this->SetStorage(0, storage, offset, size);
+        this->SetZeroStorage();
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+
+private:
+    void SetZeroStorage() {
+        return this->SetStorage(1, m_zero_storage, 0, std::numeric_limits<s64>::max());
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_switch_storage.h

@@ -0,0 +1,80 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class RegionSwitchStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(RegionSwitchStorage);
+    YUZU_NON_MOVEABLE(RegionSwitchStorage);
+
+public:
+    struct Region {
+        s64 offset;
+        s64 size;
+    };
+
+private:
+    VirtualFile m_inside_region_storage;
+    VirtualFile m_outside_region_storage;
+    Region m_region;
+
+public:
+    RegionSwitchStorage(VirtualFile&& i, VirtualFile&& o, Region r)
+        : m_inside_region_storage(std::move(i)), m_outside_region_storage(std::move(o)),
+          m_region(r) {}
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Process until we're done.
+        size_t processed = 0;
+        while (processed < size) {
+            // Process on the appropriate storage.
+            s64 cur_size = 0;
+            if (this->CheckRegions(std::addressof(cur_size), offset + processed,
+                                   size - processed)) {
+                m_inside_region_storage->Read(buffer + processed, cur_size, offset + processed);
+            } else {
+                m_outside_region_storage->Read(buffer + processed, cur_size, offset + processed);
+            }
+
+            // Advance.
+            processed += cur_size;
+        }
+
+        return size;
+    }
+
+    virtual size_t GetSize() const override {
+        return m_inside_region_storage->GetSize();
+    }
+
+private:
+    bool CheckRegions(s64* out_current_size, s64 offset, s64 size) const {
+        // Check if our region contains the access.
+        if (m_region.offset <= offset) {
+            if (offset < m_region.offset + m_region.size) {
+                if (m_region.offset + m_region.size <= offset + size) {
+                    *out_current_size = m_region.offset + m_region.size - offset;
+                } else {
+                    *out_current_size = size;
+                }
+                return true;
+            } else {
+                *out_current_size = size;
+                return false;
+            }
+        } else {
+            if (m_region.offset <= offset + size) {
+                *out_current_size = m_region.offset - offset;
+            } else {
+                *out_current_size = size;
+            }
+            return false;
+        }
+    }
+};
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_utility.cpp

@@ -0,0 +1,24 @@
+#include "core/file_sys/fssystem/fssystem_utility.h"
+
+namespace FileSys {
+
+void AddCounter(void* counter_, size_t counter_size, u64 value) {
+    u8* counter = static_cast<u8*>(counter_);
+    u64 remaining = value;
+    u8 carry = 0;
+
+    for (size_t i = 0; i < counter_size; i++) {
+        auto sum = counter[counter_size - 1 - i] + (remaining & 0xFF) + carry;
+        carry = static_cast<u8>(sum >> (sizeof(u8) * 8));
+        auto sum8 = static_cast<u8>(sum & 0xFF);
+
+        counter[counter_size - 1 - i] = sum8;
+
+        remaining >>= (sizeof(u8) * 8);
+        if (carry == 0 && remaining == 0) {
+            break;
+        }
+    }
+}
+
+} // namespace FileSys

src/core/file_sys/fssystem/fssystem_utility.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+
+namespace FileSys {
+
+void AddCounter(void* counter, size_t counter_size, u64 value);
+
+}