text: /*
   *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #ifndef COMMON_VIDEO_INCLUDE_I420_BUFFER_POOL_H_
  #define COMMON_VIDEO_INCLUDE_I420_BUFFER_POOL_H_
  
  #include <stddef.h>
  
  #include <list>
  
  #include "api/scoped_refptr.h"
  #include "api/video/i420_buffer.h"
  #include "rtc_base/race_checker.h"
  #include "rtc_base/ref_counted_object.h"
  
  namespace webrtc {
  
  // Simple buffer pool to avoid unnecessary allocations of I420Buffer objects.
  // The pool manages the memory of the I420Buffer returned from CreateBuffer.
  // When the I420Buffer is destructed, the memory is returned to the pool for use
  // by subsequent calls to CreateBuffer. If the resolution passed to CreateBuffer
  // changes, old buffers will be purged from the pool.
  // Note that CreateBuffer will crash if more than kMaxNumberOfFramesBeforeCrash
  // are created. This is to prevent memory leaks where frames are not returned.
  class I420BufferPool {
   public:
    I420BufferPool();
    explicit I420BufferPool(bool zero_initialize);
    I420BufferPool(bool zero_initialze, size_t max_number_of_buffers);
    ~I420BufferPool();
  
    // Returns a buffer from the pool. If no suitable buffer exist in the pool
    // and there are less than |max_number_of_buffers| pending, a buffer is
    // created. Returns null otherwise.
    rtc::scoped_refptr<I420Buffer> CreateBuffer(int width, int height);
  
    // Returns a buffer from the pool with the explicitly specified stride.
    rtc::scoped_refptr<I420Buffer> CreateBuffer(int width,
                                                int height,
                                                int stride_y,
                                                int stride_u,
                                                int stride_v);
  
    // Changes the max amount of buffers in the pool to the new value.
    // Returns true if change was successful and false if the amount of already
    // allocated buffers is bigger than new value.
    bool Resize(size_t max_number_of_buffers);
  
    // Clears buffers_ and detaches the thread checker so that it can be reused
    // later from another thread.
    void Release();
  
   private:
    // Explicitly use a RefCountedObject to get access to HasOneRef,
    // needed by the pool to check exclusive access.
    using PooledI420Buffer = rtc::RefCountedObject<I420Buffer>;
  
    rtc::RaceChecker race_checker_;
    std::list<rtc::scoped_refptr<PooledI420Buffer>> buffers_;
    // If true, newly allocated buffers are zero-initialized. Note that recycled
    // buffers are not zero'd before reuse. This is required of buffers used by
    // FFmpeg according to http://crbug.com/390941, which only requires it for the
    // initial allocation (as shown by FFmpeg's own buffer allocation code). It
    // has to do with "Use-of-uninitialized-value" on "Linux_msan_chrome".
    const bool zero_initialize_;
    // Max number of buffers this pool can have pending.
    size_t max_number_of_buffers_;
  };
  
  }  // namespace webrtc
  
  #endif  // COMMON_VIDEO_INCLUDE_I420_BUFFER_POOL_H_
  