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 SDK_OBJC_FRAMEWORK_CLASSES_VIDEOTOOLBOX_NALU_REWRITER_H_
  #define SDK_OBJC_FRAMEWORK_CLASSES_VIDEOTOOLBOX_NALU_REWRITER_H_
  
  #include "modules/video_coding/codecs/h264/include/h264.h"
  
  #include <CoreMedia/CoreMedia.h>
  #include <vector>
  
  #include "common_video/h264/h264_common.h"
  #include "modules/include/module_common_types.h"
  #include "rtc_base/buffer.h"
  
  using webrtc::H264::NaluIndex;
  
  namespace webrtc {
  
  // Converts a sample buffer emitted from the VideoToolbox encoder into a buffer
  // suitable for RTP. The sample buffer is in avcc format whereas the rtp buffer
  // needs to be in Annex B format. Data is written directly to |annexb_buffer|
  // and a new RTPFragmentationHeader is returned in |out_header|.
  bool H264CMSampleBufferToAnnexBBuffer(
      CMSampleBufferRef avcc_sample_buffer,
      bool is_keyframe,
      rtc::Buffer* annexb_buffer,
      std::unique_ptr<RTPFragmentationHeader> *out_header);
  
  // Converts a buffer received from RTP into a sample buffer suitable for the
  // VideoToolbox decoder. The RTP buffer is in annex b format whereas the sample
  // buffer is in avcc format.
  // If |is_keyframe| is true then |video_format| is ignored since the format will
  // be read from the buffer. Otherwise |video_format| must be provided.
  // Caller is responsible for releasing the created sample buffer.
  bool H264AnnexBBufferToCMSampleBuffer(const uint8_t* annexb_buffer,
                                        size_t annexb_buffer_size,
                                        CMVideoFormatDescriptionRef video_format,
                                        CMSampleBufferRef* out_sample_buffer);
  
  // Returns a video format description created from the sps/pps information in
  // the Annex B buffer. If there is no such information, nullptr is returned.
  // The caller is responsible for releasing the description.
  CMVideoFormatDescriptionRef CreateVideoFormatDescription(
      const uint8_t* annexb_buffer,
      size_t annexb_buffer_size);
  
  // Helper class for reading NALUs from an RTP Annex B buffer.
  class AnnexBBufferReader final {
   public:
    AnnexBBufferReader(const uint8_t* annexb_buffer, size_t length);
    ~AnnexBBufferReader() {}
    AnnexBBufferReader(const AnnexBBufferReader& other) = delete;
    void operator=(const AnnexBBufferReader& other) = delete;
  
    // Returns a pointer to the beginning of the next NALU slice without the
    // header bytes and its length. Returns false if no more slices remain.
    bool ReadNalu(const uint8_t** out_nalu, size_t* out_length);
  
    // Returns the number of unread NALU bytes, including the size of the header.
    // If the buffer has no remaining NALUs this will return zero.
    size_t BytesRemaining() const;
  
    // Reset the reader to start reading from the first NALU
    void SeekToStart();
  
    // Seek to the next position that holds a NALU of the desired type,
    // or the end if no such NALU is found.
    // Return true if a NALU of the desired type is found, false if we
    // reached the end instead
    bool SeekToNextNaluOfType(H264::NaluType type);
  
   private:
    // Returns the the next offset that contains NALU data.
    size_t FindNextNaluHeader(const uint8_t* start,
                              size_t length,
                              size_t offset) const;
  
    const uint8_t* const start_;
    std::vector<NaluIndex> offsets_;
    std::vector<NaluIndex>::iterator offset_;
    const size_t length_;
  };
  
  // Helper class for writing NALUs using avcc format into a buffer.
  class AvccBufferWriter final {
   public:
    AvccBufferWriter(uint8_t* const avcc_buffer, size_t length);
    ~AvccBufferWriter() {}
    AvccBufferWriter(const AvccBufferWriter& other) = delete;
    void operator=(const AvccBufferWriter& other) = delete;
  
    // Writes the data slice into the buffer. Returns false if there isn't
    // enough space left.
    bool WriteNalu(const uint8_t* data, size_t data_size);
  
    // Returns the unused bytes in the buffer.
    size_t BytesRemaining() const;
  
   private:
    uint8_t* const start_;
    size_t offset_;
    const size_t length_;
  };
  
  }  // namespace webrtc
  
  #endif  // SDK_OBJC_FRAMEWORK_CLASSES_VIDEOTOOLBOX_NALU_REWRITER_H_
  