common: Add VirtualBuffer class, to abstract memory virtualization.

src/common/virtual_buffer.h

@@ -0,0 +1,58 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/common_funcs.h"
+
+namespace Common {
+
+void* AllocateMemoryPages(std::size_t size);
+void FreeMemoryPages(void* base, std::size_t size);
+
+template <typename T>
+class VirtualBuffer final : NonCopyable {
+public:
+    constexpr VirtualBuffer() = default;
+    explicit VirtualBuffer(std::size_t count) : alloc_size{count * sizeof(T)} {
+        base_ptr = reinterpret_cast<T*>(AllocateMemoryPages(alloc_size));
+    }
+
+    ~VirtualBuffer() {
+        FreeMemoryPages(base_ptr, alloc_size);
+    }
+
+    void resize(std::size_t count) {
+        FreeMemoryPages(base_ptr, alloc_size);
+
+        alloc_size = count * sizeof(T);
+        base_ptr = reinterpret_cast<T*>(AllocateMemoryPages(alloc_size));
+    }
+
+    constexpr const T& operator[](std::size_t index) const {
+        return base_ptr[index];
+    }
+
+    constexpr T& operator[](std::size_t index) {
+        return base_ptr[index];
+    }
+
+    constexpr T* data() {
+        return base_ptr;
+    }
+
+    constexpr const T* data() const {
+        return base_ptr;
+    }
+
+    constexpr std::size_t size() const {
+        return alloc_size / sizeof(T);
+    }
+
+private:
+    std::size_t alloc_size{};
+    T* base_ptr{};
+};
+
+} // namespace Common