Support HLS MPEG2 TS with SAMPLE-AES encryption.

media/base/bit_reader.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/bit_reader.h"
 
 namespace media {
 
 BitReader::BitReader(const uint8_t* data, int size)
     : initial_size_(size),
       data_(data),
       bytes_left_(size),
       bit_reader_core_(this) {
   DCHECK(data != NULL);
   DCHECK_GE(size, 0);
 }
 
 BitReader::~BitReader() {}
 
+bool BitReader::ReadString(int num_bits, std::string* str) {

[ddorwin, 2016/04/12 00:40:47]

Why not just pass in num_bytes?

[dougsteed, 2016/05/08 23:18:44]

All the other public functions are in terms of bits, and the class itself is
called "BitReader" so I thought that would be more consistent.

+  int num_bytes = num_bits / 8;
+  DCHECK_EQ(num_bits % 8, 0);

[ddorwin, 2016/04/12 00:40:47]

Move the DCHECKs up to first line - they are checking an input assumption. Then
separate with an empty line.

[dougsteed, 2016/05/08 23:18:43]

Done.

+  DCHECK(str);
+  str->resize(num_bytes);
+  char* ptr = &str->front();

[ddorwin, 2016/04/12 00:40:47]

Then add a note to .h that the num_ value must be at least one byte.

[ddorwin, 2016/04/12 00:40:47]

Calling front() on an empty string has undefined behavior. We should at least
DCHECK_GT(num_bytes, 0);

[dougsteed, 2016/05/08 23:18:43]

Done.

+  while (num_bytes--)

[ddorwin, 2016/04/12 00:40:47]

With the nesting, it's probably best to add braces for this one.

[dougsteed, 2016/05/08 23:18:43]

Done.

+    if (!ReadBits(8, ptr++))

[ddorwin, 2016/04/12 00:40:47]

Should we note in the .h that this does not guarantee the string is valid?

[dougsteed, 2016/05/08 23:18:43]

Done.

+      return false;
+  return true;
+}
+
 int BitReader::GetBytes(int max_nbytes, const uint8_t** out) {
   DCHECK_GE(max_nbytes, 0);
   DCHECK(out);
 
   int nbytes = max_nbytes;
   if (nbytes > bytes_left_)
     nbytes = bytes_left_;
 
   *out = data_;
   data_ += nbytes;
   bytes_left_ -= nbytes;
   return nbytes;
 }
 
 }  // namespace media