1 files changed, 175 insertions, 0 deletions
diff --git a/media/formats/webm/cluster_builder.cc b/media/formats/webm/cluster_builder.cc
new file mode 100644
index 0000000..ec95616
--- /dev/null
+++ b/media/formats/webm/cluster_builder.cc
@@ -0,0 +1,175 @@
+// Copyright 2014 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/formats/webm/cluster_builder.h"
+
+#include "base/logging.h"
+#include "media/base/data_buffer.h"
+
+namespace media {
+
+static const uint8 kClusterHeader[] = {
+  0x1F, 0x43, 0xB6, 0x75,  // CLUSTER ID
+  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // cluster(size = 0)
+  0xE7,  // Timecode ID
+  0x88,  // timecode(size=8)
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // timecode value
+};
+
+static const uint8 kSimpleBlockHeader[] = {
+  0xA3,  // SimpleBlock ID
+  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // SimpleBlock(size = 0)
+};
+
+static const uint8 kBlockGroupHeader[] = {
+  0xA0,  // BlockGroup ID
+  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // BlockGroup(size = 0)
+  0x9B,  // BlockDuration ID
+  0x88,  // BlockDuration(size = 8)
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // duration
+  0xA1,  // Block ID
+  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // Block(size = 0)
+};
+
+enum {
+  kClusterSizeOffset = 4,
+  kClusterTimecodeOffset = 14,
+
+  kSimpleBlockSizeOffset = 1,
+
+  kBlockGroupSizeOffset = 1,
+  kBlockGroupDurationOffset = 11,
+  kBlockGroupBlockSizeOffset = 20,
+
+  kInitialBufferSize = 32768,
+};
+
+Cluster::Cluster(scoped_ptr<uint8[]> data, int size)
+    : data_(data.Pass()), size_(size) {}
+Cluster::~Cluster() {}
+
+ClusterBuilder::ClusterBuilder() { Reset(); }
+ClusterBuilder::~ClusterBuilder() {}
+
+void ClusterBuilder::SetClusterTimecode(int64 cluster_timecode) {
+  DCHECK_EQ(cluster_timecode_, -1);
+
+  cluster_timecode_ = cluster_timecode;
+
+  // Write the timecode into the header.
+  uint8* buf = buffer_.get() + kClusterTimecodeOffset;
+  for (int i = 7; i >= 0; --i) {
+    buf[i] = cluster_timecode & 0xff;
+    cluster_timecode >>= 8;
+  }
+}
+
+void ClusterBuilder::AddSimpleBlock(int track_num, int64 timecode, int flags,
+                                    const uint8* data, int size) {
+  int block_size = size + 4;
+  int bytes_needed = sizeof(kSimpleBlockHeader) + block_size;
+  if (bytes_needed > (buffer_size_ - bytes_used_))
+    ExtendBuffer(bytes_needed);
+
+  uint8* buf = buffer_.get() + bytes_used_;
+  int block_offset = bytes_used_;
+  memcpy(buf, kSimpleBlockHeader, sizeof(kSimpleBlockHeader));
+  UpdateUInt64(block_offset + kSimpleBlockSizeOffset, block_size);
+  buf += sizeof(kSimpleBlockHeader);
+
+  WriteBlock(buf, track_num, timecode, flags, data, size);
+
+  bytes_used_ += bytes_needed;
+}
+
+void ClusterBuilder::AddBlockGroup(int track_num, int64 timecode, int duration,
+                                   int flags, const uint8* data, int size) {
+  int block_size = size + 4;
+  int bytes_needed = sizeof(kBlockGroupHeader) + block_size;
+  int block_group_size = bytes_needed - 9;
+
+  if (bytes_needed > (buffer_size_ - bytes_used_))
+    ExtendBuffer(bytes_needed);
+
+  uint8* buf = buffer_.get() + bytes_used_;
+  int block_group_offset = bytes_used_;
+  memcpy(buf, kBlockGroupHeader, sizeof(kBlockGroupHeader));
+  UpdateUInt64(block_group_offset + kBlockGroupSizeOffset, block_group_size);
+  UpdateUInt64(block_group_offset + kBlockGroupDurationOffset, duration);
+  UpdateUInt64(block_group_offset + kBlockGroupBlockSizeOffset, block_size);
+  buf += sizeof(kBlockGroupHeader);
+
+  // Make sure the 4 most-significant bits are 0.
+  // http://www.matroska.org/technical/specs/index.html#block_structure
+  flags &= 0x0f;
+
+  WriteBlock(buf, track_num, timecode, flags, data, size);
+
+  bytes_used_ += bytes_needed;
+}
+
+void ClusterBuilder::WriteBlock(uint8* buf, int track_num, int64 timecode,
+                                int flags, const uint8* data, int size) {
+  DCHECK_GE(track_num, 0);
+  DCHECK_LE(track_num, 126);
+  DCHECK_GE(flags, 0);
+  DCHECK_LE(flags, 0xff);
+  DCHECK(data);
+  DCHECK_GT(size, 0);
+  DCHECK_NE(cluster_timecode_, -1);
+
+  int64 timecode_delta = timecode - cluster_timecode_;
+  DCHECK_GE(timecode_delta, -32768);
+  DCHECK_LE(timecode_delta, 32767);
+
+  buf[0] = 0x80 | (track_num & 0x7F);
+  buf[1] = (timecode_delta >> 8) & 0xff;
+  buf[2] = timecode_delta & 0xff;
+  buf[3] = flags & 0xff;
+  memcpy(buf + 4, data, size);
+}
+
+scoped_ptr<Cluster> ClusterBuilder::Finish() {
+  DCHECK_NE(cluster_timecode_, -1);
+
+  UpdateUInt64(kClusterSizeOffset, bytes_used_ - (kClusterSizeOffset + 8));
+
+  scoped_ptr<Cluster> ret(new Cluster(buffer_.Pass(), bytes_used_));
+  Reset();
+  return ret.Pass();
+}
+
+void ClusterBuilder::Reset() {
+  buffer_size_ = kInitialBufferSize;
+  buffer_.reset(new uint8[buffer_size_]);
+  memcpy(buffer_.get(), kClusterHeader, sizeof(kClusterHeader));
+  bytes_used_ = sizeof(kClusterHeader);
+  cluster_timecode_ = -1;
+}
+
+void ClusterBuilder::ExtendBuffer(int bytes_needed) {
+  int new_buffer_size = 2 * buffer_size_;
+
+  while ((new_buffer_size - bytes_used_) < bytes_needed)
+    new_buffer_size *= 2;
+
+  scoped_ptr<uint8[]> new_buffer(new uint8[new_buffer_size]);
+
+  memcpy(new_buffer.get(), buffer_.get(), bytes_used_);
+  buffer_.reset(new_buffer.release());
+  buffer_size_ = new_buffer_size;
+}
+
+void ClusterBuilder::UpdateUInt64(int offset, int64 value) {
+  DCHECK_LE(offset + 7, buffer_size_);
+  uint8* buf = buffer_.get() + offset;
+
+  // Fill the last 7 bytes of size field in big-endian order.
+  for (int i = 7; i > 0; i--) {
+    buf[i] = value & 0xff;
+    value >>= 8;
+  }
+}
+
+}  // namespace media