src/dawn/native/d3d12/TextureCopySplitter.h

// Copyright 2017 The Dawn & Tint Authors
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#ifndef SRC_DAWN_NATIVE_D3D12_TEXTURECOPYSPLITTER_H_
#define SRC_DAWN_NATIVE_D3D12_TEXTURECOPYSPLITTER_H_

#include <array>

#include "dawn/native/dawn_platform.h"

namespace dawn::native {

struct TexelBlockInfo;

}  // namespace dawn::native

namespace dawn::native::d3d12 {

struct TextureCopySubresource {
    static constexpr unsigned int kMaxTextureCopyRegions = 4;

    struct CopyInfo {
        uint64_t alignedOffset = 0;
        Origin3D textureOffset;
        Origin3D bufferOffset;
        Extent3D bufferSize;

        Extent3D copySize;
    };

    CopyInfo* AddCopy();

    uint32_t count = 0;
    std::array<CopyInfo, kMaxTextureCopyRegions> copies;
};

struct TextureCopySplits {
    static constexpr uint32_t kMaxTextureCopySubresources = 2;

    std::array<TextureCopySubresource, kMaxTextureCopySubresources> copySubresources;
};

// This function is shared by 2D and 3D texture copy splitter. But it only knows how to handle
// 2D non-arrayed textures correctly, and just forwards "copySize.depthOrArrayLayers". See
// details in Compute{2D|3D}TextureCopySplits about how we generate copy regions for 2D array
// and 3D textures based on this function.
// The resulting copies triggered by API like CopyTextureRegion are equivalent to the copy
// regions defines by the arguments of TextureCopySubresource returned by this function and its
// counterparts. These arguments should strictly conform to particular invariants. Otherwise,
// D3D12 driver may report validation errors when we call CopyTextureRegion. Some important
// invariants are listed below. For more details
// of these invariants, see src/dawn/tests/unittests/d3d12/CopySplitTests.cpp.
//   - Inside each copy region: 1) its buffer offset plus copy size should be less than its
//     buffer size, 2) its buffer offset on y-axis should be less than copy format's
//     blockInfo.height, 3) its buffer offset on z-axis should be 0.
//   - Each copy region has an offset (aka alignedOffset) aligned to
//     D3D12_TEXTURE_DATA_PLACEMENT_ALIGNMENT
//   - The buffer footprint of each copy region should be entirely within the copied buffer,
//     which means that the last "texel" of the buffer footprint doesn't go past the end of
//     the buffer even though the last "texel" might not be copied.
//   - If there are multiple copy regions, each copy region should not overlap with the others.
//   - Copy region(s) combined should exactly be equivalent to the texture region to be copied.
//   - Every pixel accessed by every copy region should not be out of the bound of the copied
//     texture and buffer.
TextureCopySubresource Compute2DTextureCopySubresource(Origin3D origin,
                                                       Extent3D copySize,
                                                       const TexelBlockInfo& blockInfo,
                                                       uint64_t offset,
                                                       uint32_t bytesPerRow);

TextureCopySplits Compute2DTextureCopySplits(Origin3D origin,
                                             Extent3D copySize,
                                             const TexelBlockInfo& blockInfo,
                                             uint64_t offset,
                                             uint32_t bytesPerRow,
                                             uint32_t rowsPerImage);

TextureCopySubresource Compute3DTextureCopySplits(Origin3D origin,
                                                  Extent3D copySize,
                                                  const TexelBlockInfo& blockInfo,
                                                  uint64_t offset,
                                                  uint32_t bytesPerRow,
                                                  uint32_t rowsPerImage);
}  // namespace dawn::native::d3d12

#endif  // SRC_DAWN_NATIVE_D3D12_TEXTURECOPYSPLITTER_H_