cc/gapir/post_buffer.h

/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * 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 GAPIR_POSTBUFFER_H
#define GAPIR_POSTBUFFER_H

#include <cstdint>
#include <functional>
#include <memory>

namespace gapir {

// PostBuffer provides a delayed-send buffer for pushing data to the server.
// This serves as an optimisation to batch many small postbacks into fewer, larger batches.
class PostBuffer {
public:
    typedef std::function<bool(const void*, uint32_t)> PostBufferCallback;

    // Constructs a PostBuffer with the specified maximum capacity and function to invoke when
    // the PostBuffer wants to flush the buffer to the server.
    PostBuffer(uint32_t desiredCapacity, PostBufferCallback callback);
    ~PostBuffer();

    // Push data to the buffer. If the buffer does not have enough space to buffer the data, then
    // the contents of the PushBuffer will be flushed.
    bool push(const void* address, uint32_t count);

    // Forcefully flush the PostBuffer. If the PostBuffer is empty then calling this function does
    // nothing.
    bool flush();

private:
    // The PostBuffer's internal buffer.
    const std::unique_ptr<uint8_t[]> mBuffer;

    // The maximum capacity of the internal buffer.
    const uint32_t mCapacity;

    // The flush callback function.
    const PostBufferCallback mCallback;

    // The offset in mBuffer for the next write.
    uint32_t mOffset;
};

}  // namespace gapir

#endif // GAPIR_POSTBUFFER_H