src/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 <cstring>

#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);

  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->Read2(&subsample_count) &&
         reader->HasBytes(subsample_count * kEntrySize));

  subsamples.resize(subsample_count);
  for (int i = 0; i < subsample_count; i++) {
    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;
  }
  return true;
}

bool FrameCENCInfo::GetTotalSizeOfSubsamples(size_t* total_size) const {
  size_t size = 0;
  for (size_t i = 0; i < subsamples.size(); i++) {
    size += subsamples[i].clear_bytes;
    RCHECK(size >= subsamples[i].clear_bytes);  // overflow
    size += subsamples[i].cypher_bytes;
    RCHECK(size >= subsamples[i].cypher_bytes);  // overflow
  }
  *total_size = size;
  return true;
}

}  // namespace mp4
}  // namespace media