Common: Add UniqueBuffer and SharedBuffer templates.

Source/Core/Common/Buffer.h

@@ -0,0 +1,66 @@
+// Copyright 2025 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <memory>
+
+// UniqueBuffer<T> and SharedBuffer<T> are a lighter alternative to std::vector<T>.
+// The main benefit is that elements are not value-initialized like in vector.
+// That can be quite a bit of unecessary overhead when allocating a large buffer.
+
+namespace Common
+{
+
+namespace detail
+{
+template <auto MakeFunc, typename T>
+class BufferBase final
+{
+public:
+  using PtrType = decltype(MakeFunc(1));
+
+  using value_type = T;
+  using size_type = std::size_t;
+
+  BufferBase() {}
+  BufferBase(size_type size) : m_ptr{MakeFunc(size)}, m_size{size} {}
+
+  void swap(BufferBase& other)
+  {
+    std::swap(m_ptr, other.m_ptr);
+    std::swap(m_size, other.m_size);
+  }
+
+  size_type size() const { return m_size; }
+  bool empty() const { return m_size == 0; }
+
+  T* get() { return m_ptr.get(); }
+  const T* get() const { return m_ptr.get(); }
+
+  T* data() { return m_ptr.get(); }
+  const T* data() const { return m_ptr.get(); }
+
+  T* begin() { return m_ptr.get(); }
+  T* end() { return m_ptr.get() + m_size; }
+
+  const T* begin() const { return m_ptr.get(); }
+  const T* end() const { return m_ptr.get() + m_size; }
+
+  T& operator[](size_type index) { return m_ptr[index]; }
+  const T& operator[](size_type index) const { return m_ptr[index]; }
+
+private:
+  PtrType m_ptr;
+  size_type m_size = 0;
+};
+}  // namespace detail
+
+template <typename T>
+using UniqueBuffer = detail::BufferBase<std::make_unique_for_overwrite<T[]>, T>;
+
+// TODO: std::make_shared_for_overwrite requires GCC 12.1+
+// template <typename T>
+// using SharedBuffer = detail::BufferBase<std::make_shared_for_overwrite<T[]>, T>;
+
+}  // namespace Common

Source/Core/Common/CMakeLists.txt

@@ -18,6 +18,7 @@ add_library(common
   BitSet.h
   BitUtils.h
   BlockingLoop.h
+  Buffer.h
   ChunkFile.h
   CodeBlock.h
   ColorUtil.cpp

Source/Core/DolphinLib.props

@@ -26,6 +26,7 @@
     <ClInclude Include="Common\BitSet.h" />
     <ClInclude Include="Common\BitUtils.h" />
     <ClInclude Include="Common\BlockingLoop.h" />
+    <ClInclude Include="Common\Buffer.h" />
     <ClInclude Include="Common\ChunkFile.h" />
     <ClInclude Include="Common\CodeBlock.h" />
     <ClInclude Include="Common\ColorUtil.h" />