Rewrite host GPU abstraction

- Don't have to repeat the same thing for 4 renderers.
 - Add native Metal renderer.

src/util/d3d11_stream_buffer.h

@@ -0,0 +1,46 @@
+// SPDX-FileCopyrightText: 2019-2023 Connor McLaughlin <stenzek@gmail.com>
+// SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
+
+#pragma once
+
+#include "common/types.h"
+#include "common/windows_headers.h"
+
+#include <d3d11_1.h>
+#include <wrl/client.h>
+
+class D3D11StreamBuffer
+{
+public:
+  template<typename T>
+  using ComPtr = Microsoft::WRL::ComPtr<T>;
+
+  D3D11StreamBuffer();
+  D3D11StreamBuffer(ComPtr<ID3D11Buffer> buffer);
+  ~D3D11StreamBuffer();
+
+  ALWAYS_INLINE ID3D11Buffer* GetD3DBuffer() const { return m_buffer.Get(); }
+  ALWAYS_INLINE ID3D11Buffer* const* GetD3DBufferArray() const { return m_buffer.GetAddressOf(); }
+  ALWAYS_INLINE u32 GetSize() const { return m_size; }
+  ALWAYS_INLINE u32 GetPosition() const { return m_position; }
+
+  bool Create(ID3D11Device* device, D3D11_BIND_FLAG bind_flags, u32 size);
+  void Destroy();
+
+  struct MappingResult
+  {
+    void* pointer;
+    u32 buffer_offset;
+    u32 index_aligned; // offset / alignment, suitable for base vertex
+    u32 space_aligned; // remaining space / alignment
+  };
+
+  MappingResult Map(ID3D11DeviceContext1* context, u32 alignment, u32 min_size);
+  void Unmap(ID3D11DeviceContext1* context, u32 used_size);
+
+private:
+  ComPtr<ID3D11Buffer> m_buffer;
+  u32 m_size;
+  u32 m_position;
+  bool m_use_map_no_overwrite = false;
+};