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<div class="title">webm_crypto_helpers.cc</div> </div>
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<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">// Copyright 2014 The Chromium Authors. All rights reserved.</span></div>
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<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment">// Use of this source code is governed by a BSD-style license that can be</span></div>
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<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment">// found in the LICENSE file.</span></div>
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<div class="line"><a name="l00004"></a><span class="lineno"> 4</span> </div>
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<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="preprocessor">#include "packager/media/formats/webm/webm_crypto_helpers.h"</span></div>
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<div class="line"><a name="l00006"></a><span class="lineno"> 6</span> </div>
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<div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="preprocessor">#include "packager/base/logging.h"</span></div>
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<div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="preprocessor">#include "packager/base/sys_byteorder.h"</span></div>
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<div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="preprocessor">#include "packager/media/base/buffer_reader.h"</span></div>
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<div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="preprocessor">#include "packager/media/formats/webm/webm_constants.h"</span></div>
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<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> </div>
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<div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="keyword">namespace </span>shaka {</div>
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<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="keyword">namespace </span>media {</div>
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<div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="keyword">namespace </span>{</div>
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<div class="line"><a name="l00015"></a><span class="lineno"> 15</span> </div>
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<div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="comment">// Generates a 16 byte CTR counter block. The CTR counter block format is a</span></div>
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<div class="line"><a name="l00017"></a><span class="lineno"> 17</span> <span class="comment">// CTR IV appended with a CTR block counter. |iv| is an 8 byte CTR IV.</span></div>
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<div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="comment">// |iv_size| is the size of |iv| in btyes. Returns a string of</span></div>
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<div class="line"><a name="l00019"></a><span class="lineno"> 19</span> <span class="comment">// kDecryptionKeySize bytes.</span></div>
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<div class="line"><a name="l00020"></a><span class="lineno"> 20</span> std::vector<uint8_t> GenerateWebMCounterBlock(<span class="keyword">const</span> uint8_t* iv, <span class="keywordtype">int</span> iv_size) {</div>
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<div class="line"><a name="l00021"></a><span class="lineno"> 21</span>  std::vector<uint8_t> counter_block(iv, iv + iv_size);</div>
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<div class="line"><a name="l00022"></a><span class="lineno"> 22</span>  counter_block.insert(counter_block.end(),</div>
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<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>  <a class="code" href="../../de/d49/classshaka_1_1media_1_1DecryptConfig.html#afa140203b87d3e46d5fd94b231734f53">DecryptConfig::kDecryptionKeySize</a> - iv_size, 0);</div>
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<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>  <span class="keywordflow">return</span> counter_block;</div>
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<div class="line"><a name="l00025"></a><span class="lineno"> 25</span> }</div>
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<div class="line"><a name="l00026"></a><span class="lineno"> 26</span> </div>
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<div class="line"><a name="l00027"></a><span class="lineno"> 27</span> } <span class="comment">// namespace anonymous</span></div>
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<div class="line"><a name="l00028"></a><span class="lineno"> 28</span> </div>
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<div class="line"><a name="l00029"></a><span class="lineno"> 29</span> <span class="comment">// TODO(tinskip): Add unit test for this function.</span></div>
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<div class="line"><a name="l00030"></a><span class="lineno"> 30</span> <span class="keywordtype">bool</span> WebMCreateDecryptConfig(<span class="keyword">const</span> uint8_t* data,</div>
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<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  <span class="keywordtype">int</span> data_size,</div>
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<div class="line"><a name="l00032"></a><span class="lineno"> 32</span>  <span class="keyword">const</span> uint8_t* key_id,</div>
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<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>  <span class="keywordtype">size_t</span> key_id_size,</div>
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<div class="line"><a name="l00034"></a><span class="lineno"> 34</span>  std::unique_ptr<DecryptConfig>* decrypt_config,</div>
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<div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  <span class="keywordtype">int</span>* data_offset) {</div>
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<div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="keywordtype">int</span> header_size = kWebMSignalByteSize;</div>
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<div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  <span class="keywordflow">if</span> (data_size < header_size) {</div>
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<div class="line"><a name="l00038"></a><span class="lineno"> 38</span>  DVLOG(1) << <span class="stringliteral">"Empty WebM sample."</span>;</div>
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<div class="line"><a name="l00039"></a><span class="lineno"> 39</span>  <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
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<div class="line"><a name="l00040"></a><span class="lineno"> 40</span>  }</div>
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<div class="line"><a name="l00041"></a><span class="lineno"> 41</span>  uint8_t signal_byte = data[0];</div>
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<div class="line"><a name="l00042"></a><span class="lineno"> 42</span> </div>
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<div class="line"><a name="l00043"></a><span class="lineno"> 43</span>  <span class="keywordflow">if</span> (signal_byte & kWebMEncryptedSignal) {</div>
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<div class="line"><a name="l00044"></a><span class="lineno"> 44</span>  <span class="comment">// Encrypted sample.</span></div>
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<div class="line"><a name="l00045"></a><span class="lineno"> 45</span>  header_size += kWebMIvSize;</div>
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<div class="line"><a name="l00046"></a><span class="lineno"> 46</span>  <span class="keywordflow">if</span> (data_size < header_size) {</div>
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<div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  DVLOG(1) << <span class="stringliteral">"Encrypted WebM sample too small to hold IV: "</span> << data_size;</div>
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<div class="line"><a name="l00048"></a><span class="lineno"> 48</span>  <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
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<div class="line"><a name="l00049"></a><span class="lineno"> 49</span>  }</div>
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<div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  std::vector<SubsampleEntry> subsamples;</div>
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<div class="line"><a name="l00051"></a><span class="lineno"> 51</span>  <span class="keywordflow">if</span> (signal_byte & kWebMPartitionedSignal) {</div>
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<div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  <span class="comment">// Encrypted sample with subsamples / partitioning.</span></div>
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<div class="line"><a name="l00053"></a><span class="lineno"> 53</span>  header_size += kWebMNumPartitionsSize;</div>
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<div class="line"><a name="l00054"></a><span class="lineno"> 54</span>  <span class="keywordflow">if</span> (data_size < header_size) {</div>
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<div class="line"><a name="l00055"></a><span class="lineno"> 55</span>  DVLOG(1)</div>
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<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  << <span class="stringliteral">"Encrypted WebM sample too small to hold number of partitions: "</span></div>
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<div class="line"><a name="l00057"></a><span class="lineno"> 57</span>  << data_size;</div>
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<div class="line"><a name="l00058"></a><span class="lineno"> 58</span>  <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
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<div class="line"><a name="l00059"></a><span class="lineno"> 59</span>  }</div>
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<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>  uint8_t num_partitions = data[kWebMSignalByteSize + kWebMIvSize];</div>
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<div class="line"><a name="l00061"></a><span class="lineno"> 61</span>  BufferReader offsets_buffer(data + header_size, data_size - header_size);</div>
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<div class="line"><a name="l00062"></a><span class="lineno"> 62</span>  header_size += num_partitions * kWebMPartitionOffsetSize;</div>
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<div class="line"><a name="l00063"></a><span class="lineno"> 63</span>  uint32_t subsample_offset = 0;</div>
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<div class="line"><a name="l00064"></a><span class="lineno"> 64</span>  <span class="keywordtype">bool</span> encrypted_subsample = <span class="keyword">false</span>;</div>
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<div class="line"><a name="l00065"></a><span class="lineno"> 65</span>  uint16_t clear_size = 0;</div>
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<div class="line"><a name="l00066"></a><span class="lineno"> 66</span>  uint32_t encrypted_size = 0;</div>
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<div class="line"><a name="l00067"></a><span class="lineno"> 67</span>  <span class="keywordflow">for</span> (uint8_t partition_idx = 0; partition_idx < num_partitions;</div>
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<div class="line"><a name="l00068"></a><span class="lineno"> 68</span>  ++partition_idx) {</div>
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<div class="line"><a name="l00069"></a><span class="lineno"> 69</span>  uint32_t partition_offset;</div>
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<div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  <span class="keywordflow">if</span> (!offsets_buffer.Read4(&partition_offset)) {</div>
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<div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  DVLOG(1)</div>
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<div class="line"><a name="l00072"></a><span class="lineno"> 72</span>  << <span class="stringliteral">"Encrypted WebM sample too small to hold partition offsets: "</span></div>
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<div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  << data_size;</div>
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<div class="line"><a name="l00074"></a><span class="lineno"> 74</span>  <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
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<div class="line"><a name="l00075"></a><span class="lineno"> 75</span>  }</div>
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<div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  <span class="keywordflow">if</span> (partition_offset < subsample_offset) {</div>
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<div class="line"><a name="l00077"></a><span class="lineno"> 77</span>  DVLOG(1) << <span class="stringliteral">"Partition offsets out of order."</span>;</div>
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<div class="line"><a name="l00078"></a><span class="lineno"> 78</span>  <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
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<div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  }</div>
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<div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  <span class="keywordflow">if</span> (encrypted_subsample) {</div>
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<div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  encrypted_size = partition_offset - subsample_offset;</div>
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<div class="line"><a name="l00082"></a><span class="lineno"> 82</span>  subsamples.push_back(SubsampleEntry(clear_size, encrypted_size));</div>
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<div class="line"><a name="l00083"></a><span class="lineno"> 83</span>  } <span class="keywordflow">else</span> {</div>
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<div class="line"><a name="l00084"></a><span class="lineno"> 84</span>  clear_size = partition_offset - subsample_offset;</div>
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<div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  <span class="keywordflow">if</span> (partition_idx == (num_partitions - 1)) {</div>
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<div class="line"><a name="l00086"></a><span class="lineno"> 86</span>  encrypted_size = data_size - header_size - subsample_offset - clear_size;</div>
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<div class="line"><a name="l00087"></a><span class="lineno"> 87</span>  subsamples.push_back(SubsampleEntry(clear_size, encrypted_size));</div>
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<div class="line"><a name="l00088"></a><span class="lineno"> 88</span>  }</div>
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<div class="line"><a name="l00089"></a><span class="lineno"> 89</span>  }</div>
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<div class="line"><a name="l00090"></a><span class="lineno"> 90</span>  subsample_offset = partition_offset;</div>
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<div class="line"><a name="l00091"></a><span class="lineno"> 91</span>  encrypted_subsample = !encrypted_subsample;</div>
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<div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  }</div>
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<div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  <span class="keywordflow">if</span> (!(num_partitions % 2)) {</div>
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<div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  <span class="comment">// Even number of partitions. Add one last all-clear subsample.</span></div>
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<div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  clear_size = data_size - header_size - subsample_offset;</div>
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<div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  encrypted_size = 0;</div>
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<div class="line"><a name="l00097"></a><span class="lineno"> 97</span>  subsamples.push_back(SubsampleEntry(clear_size, encrypted_size));</div>
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<div class="line"><a name="l00098"></a><span class="lineno"> 98</span>  }</div>
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<div class="line"><a name="l00099"></a><span class="lineno"> 99</span>  }</div>
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<div class="line"><a name="l00100"></a><span class="lineno"> 100</span>  decrypt_config->reset(<span class="keyword">new</span> DecryptConfig(</div>
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<div class="line"><a name="l00101"></a><span class="lineno"> 101</span>  std::vector<uint8_t>(key_id, key_id + key_id_size),</div>
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<div class="line"><a name="l00102"></a><span class="lineno"> 102</span>  GenerateWebMCounterBlock(data + kWebMSignalByteSize, kWebMIvSize),</div>
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<div class="line"><a name="l00103"></a><span class="lineno"> 103</span>  subsamples));</div>
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<div class="line"><a name="l00104"></a><span class="lineno"> 104</span>  } <span class="keywordflow">else</span> {</div>
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<div class="line"><a name="l00105"></a><span class="lineno"> 105</span>  <span class="comment">// Clear sample.</span></div>
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<div class="line"><a name="l00106"></a><span class="lineno"> 106</span>  decrypt_config->reset();</div>
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<div class="line"><a name="l00107"></a><span class="lineno"> 107</span>  }</div>
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<div class="line"><a name="l00108"></a><span class="lineno"> 108</span> </div>
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<div class="line"><a name="l00109"></a><span class="lineno"> 109</span>  *data_offset = header_size;</div>
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<div class="line"><a name="l00110"></a><span class="lineno"> 110</span>  <span class="keywordflow">return</span> <span class="keyword">true</span>;</div>
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<div class="line"><a name="l00111"></a><span class="lineno"> 111</span> }</div>
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<div class="line"><a name="l00112"></a><span class="lineno"> 112</span> </div>
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<div class="line"><a name="l00113"></a><span class="lineno"> 113</span> } <span class="comment">// namespace media</span></div>
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<div class="line"><a name="l00114"></a><span class="lineno"> 114</span> } <span class="comment">// namespace shaka</span></div>
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<div class="ttc" id="classshaka_1_1media_1_1DecryptConfig_html_afa140203b87d3e46d5fd94b231734f53"><div class="ttname"><a href="../../de/d49/classshaka_1_1media_1_1DecryptConfig.html#afa140203b87d3e46d5fd94b231734f53">shaka::media::DecryptConfig::kDecryptionKeySize</a></div><div class="ttdeci">static const size_t kDecryptionKeySize</div><div class="ttdoc">Keys are always 128 bits. </div><div class="ttdef"><b>Definition:</b> <a href="../../df/dad/decrypt__config_8h_source.html#l00043">decrypt_config.h:43</a></div></div>
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