src/dawn_native/ScratchBuffer.h

// Copyright 2021 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef DAWNNATIVE_SCRATCHBUFFER_H_
#define DAWNNATIVE_SCRATCHBUFFER_H_

#include "common/RefCounted.h"
#include "dawn_native/Buffer.h"

#include <cstdint>

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

}  // namespace dawn_native

#endif  // DAWNNATIVE_SCRATCHBUFFER_H_