common: Extract UUID to its own class

Since the Mii database uses UUIDs very similar to the Accounts database, it makes no sense to not share code between them.

src/common/uuid.cpp

@@ -0,0 +1,33 @@
+// Copyright 2018 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <random>
+
+#include <fmt/format.h>
+
+#include "common/uuid.h"
+
+namespace Common {
+
+UUID UUID::Generate() {
+    std::random_device device;
+    std::mt19937 gen(device());
+    std::uniform_int_distribution<u64> distribution(1, std::numeric_limits<u64>::max());
+    return UUID{distribution(gen), distribution(gen)};
+}
+
+std::string UUID::Format() const {
+    return fmt::format("0x{:016X}{:016X}", uuid[1], uuid[0]);
+}
+
+std::string UUID::FormatSwitch() const {
+    std::array<u8, 16> s{};
+    std::memcpy(s.data(), uuid.data(), sizeof(u128));
+    return fmt::format("{:02x}{:02x}{:02x}{:02x}-{:02x}{:02x}-{:02x}{:02x}-{:02x}{:02x}-{:02x}{"
+                       ":02x}{:02x}{:02x}{:02x}{:02x}",
+                       s[0], s[1], s[2], s[3], s[4], s[5], s[6], s[7], s[8], s[9], s[10], s[11],
+                       s[12], s[13], s[14], s[15]);
+}
+
+} // namespace Common