src/dawn/native/ScratchBuffer.h

// Copyright 2021 The Dawn & Tint Authors
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#ifndef SRC_DAWN_NATIVE_SCRATCHBUFFER_H_
#define SRC_DAWN_NATIVE_SCRATCHBUFFER_H_

#include <cstdint>

#include "dawn/common/Ref.h"
#include "dawn/native/Buffer.h"
#include "partition_alloc/pointers/raw_ptr.h"

namespace dawn::native {

class DeviceBase;

// A ScratchBuffer is a lazily allocated and lazily grown GPU buffer for intermittent use by
// commands in the GPU queue. Note that scratch buffers are not zero-initialized, so users must
// be careful not to exposed uninitialized bytes to client shaders.
class ScratchBuffer {
  public:
    // Note that this object does not retain a reference to `device`, so `device` MUST outlive
    // this object.
    ScratchBuffer(DeviceBase* device, wgpu::BufferUsage usage);
    ~ScratchBuffer();

    // Resets this ScratchBuffer, guaranteeing that the next EnsureCapacity call allocates a
    // fresh buffer.
    void Reset();

    // Ensures that this ScratchBuffer is backed by a buffer on `device` with at least
    // `capacity` bytes of storage.
    MaybeError EnsureCapacity(uint64_t capacity);

    BufferBase* GetBuffer() const;

  private:
    const raw_ptr<DeviceBase> mDevice;
    const wgpu::BufferUsage mUsage;
    Ref<BufferBase> mBuffer;
};

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_SCRATCHBUFFER_H_