common/host_memory: Add interface and Windows implementation

src/common/host_memory.h

@@ -0,0 +1,62 @@
+// Copyright 2019 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include "common/common_types.h"
+
+namespace Common {
+
+/**
+ * A low level linear memory buffer, which supports multiple mappings
+ * Its purpose is to rebuild a given sparse memory layout, including mirrors.
+ */
+class HostMemory {
+public:
+    explicit HostMemory(size_t backing_size, size_t virtual_size);
+    ~HostMemory();
+
+    /**
+     * Copy constructors. They shall return a copy of the buffer without the mappings.
+     * TODO: Implement them with COW if needed.
+     */
+    HostMemory(const HostMemory& other) = delete;
+    HostMemory& operator=(const HostMemory& other) = delete;
+
+    /**
+     * Move constructors. They will move the buffer and the mappings to the new object.
+     */
+    HostMemory(HostMemory&& other) noexcept;
+    HostMemory& operator=(HostMemory&& other) noexcept;
+
+    void Map(size_t virtual_offset, size_t host_offset, size_t length);
+
+    void Unmap(size_t virtual_offset, size_t length);
+
+    void Protect(size_t virtual_offset, size_t length, bool read, bool write);
+
+    [[nodiscard]] u8* BackingBasePointer() noexcept {
+        return backing_base;
+    }
+    [[nodiscard]] const u8* BackingBasePointer() const noexcept {
+        return backing_base;
+    }
+
+    [[nodiscard]] u8* VirtualBasePointer() noexcept {
+        return virtual_base;
+    }
+    [[nodiscard]] const u8* VirtualBasePointer() const noexcept {
+        return virtual_base;
+    }
+
+private:
+    // Low level handler for the platform dependent memory routines
+    class Impl;
+    std::unique_ptr<Impl> impl;
+    u8* backing_base{};
+    u8* virtual_base{};
+};
+
+} // namespace Common