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/BlockInfo.h"
#include "dawn/native/d3d12/UtilsD3D12.h"
#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 {
        // The 512-byte aligned offset into buffer
        uint64_t alignedOffset = 0;
        // Offset into texture
        BlockOrigin3D textureOffset;
        // Offset into buffer
        BlockOrigin3D bufferOffset;
        // width,height,depth of the texture linearly laid out in the buffer
        BlockExtent3D bufferSize;
        // width,height,depth to copy
        BlockExtent3D 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 (when relaxedRowAndPitchOffset=false).
// But it only knows how to handle 2D non-arrayed textures correctly, and just forwards
// "copySize.depthOrArrayLayers". See details in Compute2DTextureCopySplits and
// Compute3DTextureCopySubresource 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 defined 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(BlockOrigin3D origin,
                                                       BlockExtent3D copySize,
                                                       const TypedTexelBlockInfo& blockInfo,
                                                       uint64_t offset,
                                                       BlockCount blocksPerRow,
                                                       bool relaxedRowAndPitchOffset);

// Use this for aligned (non-relaxed) 2D copies with multiple layers.
TextureCopySplits Compute2DTextureCopySplits(BlockOrigin3D origin,
                                             BlockExtent3D copySize,
                                             const TypedTexelBlockInfo& blockInfo,
                                             uint64_t offset,
                                             BlockCount blocksPerRow,
                                             BlockCount rowsPerImage);

TextureCopySubresource Compute3DTextureCopySubresource(BlockOrigin3D origin,
                                                       BlockExtent3D copySize,
                                                       const TypedTexelBlockInfo& blockInfo,
                                                       uint64_t offset,
                                                       BlockCount blocksPerRow,
                                                       BlockCount rowsPerImage,
                                                       bool relaxedRowAndPitchOffset);
}  // namespace dawn::native::d3d12

#endif  // SRC_DAWN_NATIVE_D3D12_TEXTURECOPYSPLITTER_H_