text: /*
   *  Copyright (c) 2017 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.
   */
  
  #include <algorithm>
  
  #include "media/base/fakertp.h"
  #include "rtc_base/gunit.h"
  
  void CompareHeaderExtensions(const char* packet1, size_t packet1_size,
      const char* packet2, size_t packet2_size,
      const std::vector<int> encrypted_headers, bool expect_equal) {
    // Sanity check: packets must be large enough to contain the RTP header and
    // extensions header.
    RTC_CHECK_GE(packet1_size, 12 + 4);
    RTC_CHECK_GE(packet2_size, 12 + 4);
    // RTP extension headers are the same.
    EXPECT_EQ(0, memcmp(packet1 + 12, packet2 + 12, 4));
    // Check for one-byte header extensions.
    EXPECT_EQ('\xBE', packet1[12]);
    EXPECT_EQ('\xDE', packet1[13]);
    // Determine position and size of extension headers.
    size_t extension_words = packet1[14] << 8 | packet1[15];
    const char* extension_data1 = packet1 + 12 + 4;
    const char* extension_end1 = extension_data1 + extension_words * 4;
    const char* extension_data2 = packet2 + 12 + 4;
    // Sanity check: packets must be large enough to contain the RTP header
    // extensions.
    RTC_CHECK_GE(packet1_size, 12 + 4 + extension_words * 4);
    RTC_CHECK_GE(packet2_size, 12 + 4 + extension_words * 4);
    while (extension_data1 < extension_end1) {
      uint8_t id = (*extension_data1 & 0xf0) >> 4;
      uint8_t len = (*extension_data1 & 0x0f) +1;
      extension_data1++;
      extension_data2++;
      EXPECT_LE(extension_data1, extension_end1);
      if (id == 15) {
        // Finished parsing.
        break;
      }
  
      // The header extension doesn't get encrypted if the id is not in the
      // list of header extensions to encrypt.
      if (expect_equal ||
          std::find(encrypted_headers.begin(), encrypted_headers.end(), id)
              == encrypted_headers.end()) {
        EXPECT_EQ(0, memcmp(extension_data1, extension_data2, len));
      } else {
        EXPECT_NE(0, memcmp(extension_data1, extension_data2, len));
      }
  
      extension_data1 += len;
      extension_data2 += len;
      // Skip padding.
      while (extension_data1 < extension_end1 && *extension_data1 == 0) {
        extension_data1++;
        extension_data2++;
      }
    }
  }
  