Support HLS MPEG2 TS with SAMPLE-AES encryption.

media/base/bit_reader.cc

Index: media/base/bit_reader.cc
diff --git a/media/base/bit_reader.cc b/media/base/bit_reader.cc
index 83ca40e315bdba854f385816019a8c28c114f82f..4e27af3f87785c175c7d5a12e0cbcda9b99bbe7c 100644
--- a/media/base/bit_reader.cc
+++ b/media/base/bit_reader.cc
@@ -17,6 +17,18 @@ BitReader::BitReader(const uint8_t* data, int size)
 
 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);