DirectXTK/Src/ConstantBuffer.h

//--------------------------------------------------------------------------------------
// File: ConstantBuffer.h
//
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
//
// http://go.microsoft.com/fwlink/?LinkId=248929
//--------------------------------------------------------------------------------------

#pragma once

#include "DirectXHelpers.h"
#include "GraphicsMemory.h"
#include "PlatformHelpers.h"


namespace DirectX
{
    // Strongly typed wrapper around a D3D constant buffer.
    template<typename T>
    class ConstantBuffer
    {
    public:
        // Constructor.
        ConstantBuffer() = default;
        explicit ConstantBuffer(_In_ ID3D11Device* device)
        {
            Create(device);
        }

        ConstantBuffer(ConstantBuffer const&) = delete;
        ConstantBuffer& operator= (ConstantBuffer const&) = delete;

    #if defined(_XBOX_ONE) && defined(_TITLE)
        void Create(_In_ ID3D11Device* device)
        {
            D3D11_BUFFER_DESC desc = {};

            desc.ByteWidth = sizeof(T);
            desc.Usage = D3D11_USAGE_DEFAULT;
            desc.BindFlags = D3D11_BIND_CONSTANT_BUFFER;
            desc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;

            Microsoft::WRL::ComPtr<ID3D11DeviceX> deviceX;
            ThrowIfFailed(device->QueryInterface(IID_GRAPHICS_PPV_ARGS(deviceX.GetAddressOf())));

            ThrowIfFailed(deviceX->CreatePlacementBuffer(&desc, nullptr, mConstantBuffer.ReleaseAndGetAddressOf()));

            SetDebugObjectName(mConstantBuffer.Get(), L"DirectXTK");
        }


        // Writes new data into the constant buffer.
        void SetData(_In_ ID3D11DeviceContext* deviceContext, T const& value, void** grfxMemory)
        {
            assert(grfxMemory != nullptr);

            void* ptr = GraphicsMemory::Get().Allocate(deviceContext, sizeof(T), 64);
            assert(ptr != nullptr);

            *(T*)ptr = value;

            *grfxMemory = ptr;
        }
    #else
        void Create(_In_ ID3D11Device* device)
        {
            D3D11_BUFFER_DESC desc = {};

            desc.ByteWidth = sizeof(T);
            desc.Usage = D3D11_USAGE_DYNAMIC;
            desc.BindFlags = D3D11_BIND_CONSTANT_BUFFER;
            desc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;

            ThrowIfFailed(
                device->CreateBuffer(&desc, nullptr, mConstantBuffer.ReleaseAndGetAddressOf())
            );

            SetDebugObjectName(mConstantBuffer.Get(), "DirectXTK");
        }


        // Writes new data into the constant buffer.
        void SetData(_In_ ID3D11DeviceContext* deviceContext, T const& value)
        {
            assert(mConstantBuffer);

            D3D11_MAPPED_SUBRESOURCE mappedResource;

            ThrowIfFailed(
                deviceContext->Map(mConstantBuffer.Get(), 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource)
            );

            *static_cast<T*>(mappedResource.pData) = value;

            deviceContext->Unmap(mConstantBuffer.Get(), 0);
        }
    #endif

    // Looks up the underlying D3D constant buffer.
        ID3D11Buffer* GetBuffer()
        {
            return mConstantBuffer.Get();
        }


    private:
        // The underlying D3D object.
        Microsoft::WRL::ComPtr<ID3D11Buffer> mConstantBuffer;
    };
}