Add Common Encryption support to BMFF, including subsample decryption.

media/mp4/cenc.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/mp4/cenc.h"
 
+#include <string.h>

[xhwang, 2012/06/27 19:37:43]

Use C++ headers? #include <cstring> 

[strobe_, 2012/07/13 00:47:07]

Done.

+
 #include "media/mp4/box_reader.h"
 #include "media/mp4/rcheck.h"
 
 namespace media {
 namespace mp4 {
 
 FrameCENCInfo::FrameCENCInfo() {}
 FrameCENCInfo::~FrameCENCInfo() {}
 
 bool FrameCENCInfo::Parse(int iv_size, BufferReader* reader) {
   const int kEntrySize = 6;
-
   // Mandated by CENC spec
   RCHECK(iv_size == 8 || iv_size == 16);
-  iv.resize(iv_size);
+
+  memset(iv, 0, sizeof(iv));
+  for (int i = 0; i < iv_size; i++)
+    RCHECK(reader->Read1(&iv[i]));
+
+  if (!reader->HasBytes(1)) return true;
 
   uint16 subsample_count;
-  RCHECK(reader->ReadVec(&iv, iv_size) &&
-         reader->Read2(&subsample_count) &&
+  RCHECK(reader->Read2(&subsample_count) &&
          reader->HasBytes(subsample_count * kEntrySize));
+
   subsamples.resize(subsample_count);
-
   for (int i = 0; i < subsample_count; i++) {
-    RCHECK(reader->Read2(&subsamples[i].clear_size) &&
-           reader->Read4(&subsamples[i].encrypted_size));
+    uint16 clear_bytes;
+    uint32 cypher_bytes;
+    RCHECK(reader->Read2(&clear_bytes) &&
+           reader->Read4(&cypher_bytes));
+    subsamples[i].clear_bytes = clear_bytes;
+    subsamples[i].cypher_bytes = cypher_bytes;

[ddorwin, 2012/07/03 21:03:47]

This doesn't cause a possible overflow warning? (uint to int)

[strobe_, 2012/07/13 00:47:07]

Surprisingly, no. I'm more than happy to use uint32/int64/uint64; I used int
here to comply with the style guide.

[ddorwin, 2012/07/17 01:14:21]

I think if you're dealing with data and it can really be unsigned 32 bits, it's
okay to use uint32. They just don't want you adding more unsigned values.

[strobe_, 2012/07/19 02:43:34]

Done.

   }
   return true;
 }
 
-size_t FrameCENCInfo::GetTotalSize() const {
+size_t FrameCENCInfo::GetTotalSizeOfSubsamples() const {
   size_t size = 0;
   for (size_t i = 0; i < subsamples.size(); i++) {
-    size += subsamples[i].clear_size + subsamples[i].encrypted_size;
+    size += subsamples[i].clear_bytes + subsamples[i].cypher_bytes;
   }
   return size;
 }
 
 }  // namespace mp4
 }  // namespace media