void nsWebMBufferedParser::Append(const unsigned char* aBuffer, uint32_t aLength,
nsTArray<nsWebMTimeDataOffset>& aMapping,
ReentrantMonitor& aReentrantMonitor)
{
static const unsigned char CLUSTER_ID[] = { 0x1f, 0x43, 0xb6, 0x75 };
static const unsigned char TIMECODE_ID = 0xe7;
static const unsigned char BLOCKGROUP_ID = 0xa0;
static const unsigned char BLOCK_ID = 0xa1;
static const unsigned char SIMPLEBLOCK_ID = 0xa3;
const unsigned char* p = aBuffer;
// Parse each byte in aBuffer one-by-one, producing timecodes and updating
// aMapping as we go. Parser pauses at end of stream (which may be at any
// point within the parse) and resumes parsing the next time Append is
// called with new data.
while (p < aBuffer + aLength) {
switch (mState) {
case CLUSTER_SYNC:
if (*p++ == CLUSTER_ID[mClusterIDPos]) {
mClusterIDPos += 1;
} else {
mClusterIDPos = 0;
}
// Cluster ID found, it's likely this is a valid sync point. If this
// is a spurious match, the later parse steps will encounter an error
// and return to CLUSTER_SYNC.
if (mClusterIDPos == sizeof(CLUSTER_ID)) {
mClusterIDPos = 0;
mState = READ_VINT;
mNextState = TIMECODE_SYNC;
}
break;
case READ_VINT: {
unsigned char c = *p++;
uint32_t mask;
mVIntLength = VIntLength(c, &mask);
mVIntLeft = mVIntLength - 1;
mVInt = c & ~mask;
mState = READ_VINT_REST;
break;
}
case READ_VINT_REST:
if (mVIntLeft) {
mVInt <<= 8;
mVInt |= *p++;
mVIntLeft -= 1;
} else {
mState = mNextState;
}
break;
case TIMECODE_SYNC:
if (*p++ != TIMECODE_ID) {
p -= 1;
mState = CLUSTER_SYNC;
break;
}
mClusterTimecode = 0;
mState = READ_VINT;
mNextState = READ_CLUSTER_TIMECODE;
break;
case READ_CLUSTER_TIMECODE:
if (mVInt) {
mClusterTimecode <<= 8;
mClusterTimecode |= *p++;
mVInt -= 1;
} else {
mState = ANY_BLOCK_SYNC;
}
break;
case ANY_BLOCK_SYNC: {
unsigned char c = *p++;
if (c == BLOCKGROUP_ID) {
mState = READ_VINT;
mNextState = ANY_BLOCK_SYNC;
} else if (c == SIMPLEBLOCK_ID || c == BLOCK_ID) {
mBlockOffset = mCurrentOffset + (p - aBuffer) - 1;
mState = READ_VINT;
mNextState = READ_BLOCK;
} else {
uint32_t length = VIntLength(c, nullptr);
if (length == 4) {
p -= 1;
mState = CLUSTER_SYNC;
} else {
mState = READ_VINT;
mNextState = SKIP_ELEMENT;
}
}
break;
}
case READ_BLOCK:
mBlockSize = mVInt;
mBlockTimecode = 0;
mBlockTimecodeLength = 2;
mState = READ_VINT;
mNextState = READ_BLOCK_TIMECODE;
break;
case READ_BLOCK_TIMECODE:
if (mBlockTimecodeLength) {
mBlockTimecode <<= 8;
mBlockTimecode |= *p++;
mBlockTimecodeLength -= 1;
} else {
// It's possible we've parsed this data before, so avoid inserting
// duplicate nsWebMTimeDataOffset entries.
{
ReentrantMonitorAutoEnter mon(aReentrantMonitor);
uint32_t idx;
if (!aMapping.GreatestIndexLtEq(mBlockOffset, idx)) {
nsWebMTimeDataOffset entry(mBlockOffset, mClusterTimecode + mBlockTimecode);
aMapping.InsertElementAt(idx, entry);
}
}
// Skip rest of block header and the block's payload.
mBlockSize -= mVIntLength;
mBlockSize -= 2;
mSkipBytes = uint32_t(mBlockSize);
mState = SKIP_DATA;
mNextState = ANY_BLOCK_SYNC;
}
break;
case SKIP_DATA:
if (mSkipBytes) {
uint32_t left = aLength - (p - aBuffer);
left = NS_MIN(left, mSkipBytes);
p += left;
mSkipBytes -= left;
} else {
mState = mNextState;
}
break;
case SKIP_ELEMENT:
mSkipBytes = uint32_t(mVInt);
mState = SKIP_DATA;
mNextState = ANY_BLOCK_SYNC;
break;
}
}
NS_ASSERTION(p == aBuffer + aLength, "Must have parsed to end of data.");
mCurrentOffset += aLength;
}
