1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/webm/WebMBufferedParser.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,218 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim:set ts=2 sw=2 sts=2 et cindent: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +#if !defined(WebMBufferedParser_h_)
1.10 +#define WebMBufferedParser_h_
1.11 +
1.12 +#include "nsISupportsImpl.h"
1.13 +#include "nsTArray.h"
1.14 +#include "mozilla/ReentrantMonitor.h"
1.15 +
1.16 +namespace mozilla {
1.17 +
1.18 +namespace dom {
1.19 +class TimeRanges;
1.20 +}
1.21 +
1.22 +// Stores a stream byte offset and the scaled timecode of the block at
1.23 +// that offset. The timecode must be scaled by the stream's timecode
1.24 +// scale before use.
1.25 +struct WebMTimeDataOffset
1.26 +{
1.27 + WebMTimeDataOffset(int64_t aOffset, uint64_t aTimecode)
1.28 + : mOffset(aOffset), mTimecode(aTimecode)
1.29 + {}
1.30 +
1.31 + bool operator==(int64_t aOffset) const {
1.32 + return mOffset == aOffset;
1.33 + }
1.34 +
1.35 + bool operator<(int64_t aOffset) const {
1.36 + return mOffset < aOffset;
1.37 + }
1.38 +
1.39 + int64_t mOffset;
1.40 + uint64_t mTimecode;
1.41 +};
1.42 +
1.43 +// A simple WebM parser that produces data offset to timecode pairs as it
1.44 +// consumes blocks. A new parser is created for each distinct range of data
1.45 +// received and begins parsing from the first WebM cluster within that
1.46 +// range. Old parsers are destroyed when their range merges with a later
1.47 +// parser or an already parsed range. The parser may start at any position
1.48 +// within the stream.
1.49 +struct WebMBufferedParser
1.50 +{
1.51 + WebMBufferedParser(int64_t aOffset)
1.52 + : mStartOffset(aOffset), mCurrentOffset(aOffset), mState(CLUSTER_SYNC), mClusterIDPos(0)
1.53 + {}
1.54 +
1.55 + // Steps the parser through aLength bytes of data. Always consumes
1.56 + // aLength bytes. Updates mCurrentOffset before returning. Acquires
1.57 + // aReentrantMonitor before using aMapping.
1.58 + void Append(const unsigned char* aBuffer, uint32_t aLength,
1.59 + nsTArray<WebMTimeDataOffset>& aMapping,
1.60 + ReentrantMonitor& aReentrantMonitor);
1.61 +
1.62 + bool operator==(int64_t aOffset) const {
1.63 + return mCurrentOffset == aOffset;
1.64 + }
1.65 +
1.66 + bool operator<(int64_t aOffset) const {
1.67 + return mCurrentOffset < aOffset;
1.68 + }
1.69 +
1.70 + // The offset at which this parser started parsing. Used to merge
1.71 + // adjacent parsers, in which case the later parser adopts the earlier
1.72 + // parser's mStartOffset.
1.73 + int64_t mStartOffset;
1.74 +
1.75 + // Current offset with the stream. Updated in chunks as Append() consumes
1.76 + // data.
1.77 + int64_t mCurrentOffset;
1.78 +
1.79 +private:
1.80 + enum State {
1.81 + // Parser start state. Scans forward searching for stream sync by
1.82 + // matching CLUSTER_ID with the curernt byte. The match state is stored
1.83 + // in mClusterIDPos. Once this reaches sizeof(CLUSTER_ID), stream may
1.84 + // have sync. The parser then advances to read the cluster size and
1.85 + // timecode.
1.86 + CLUSTER_SYNC,
1.87 +
1.88 + /*
1.89 + The the parser states below assume that CLUSTER_SYNC has found a valid
1.90 + sync point within the data. If parsing fails in these states, the
1.91 + parser returns to CLUSTER_SYNC to find a new sync point.
1.92 + */
1.93 +
1.94 + // Read the first byte of a variable length integer. The first byte
1.95 + // encodes both the variable integer's length and part of the value.
1.96 + // The value read so far is stored in mVInt and the length is stored in
1.97 + // mVIntLength. The number of bytes left to read is stored in
1.98 + // mVIntLeft.
1.99 + READ_VINT,
1.100 +
1.101 + // Reads the remaining mVIntLeft bytes into mVInt.
1.102 + READ_VINT_REST,
1.103 +
1.104 + // Check that the next element is TIMECODE_ID. The cluster timecode is
1.105 + // required to be the first element in a cluster. Advances to READ_VINT
1.106 + // to read the timecode's length into mVInt.
1.107 + TIMECODE_SYNC,
1.108 +
1.109 + // mVInt holds the length of the variable length unsigned integer
1.110 + // containing the cluster timecode. Read mVInt bytes into
1.111 + // mClusterTimecode.
1.112 + READ_CLUSTER_TIMECODE,
1.113 +
1.114 + // Skips elements with a cluster until BLOCKGROUP_ID or SIMPLEBLOCK_ID
1.115 + // is found. If BLOCKGROUP_ID is found, the parser returns to
1.116 + // ANY_BLOCK_ID searching for a BLOCK_ID. Once a block or simpleblock
1.117 + // is found, the current data offset is stored in mBlockOffset. If the
1.118 + // current byte is the beginning of a four byte variant integer, it
1.119 + // indicates the parser has reached a top-level element ID and the
1.120 + // parser returns to CLUSTER_SYNC.
1.121 + ANY_BLOCK_SYNC,
1.122 +
1.123 + // Start reading a block. Blocks and simpleblocks are parsed the same
1.124 + // way as the initial layouts are identical. mBlockSize is initialized
1.125 + // from mVInt (holding the element size), and mBlockTimecode(Length) is
1.126 + // initialized for parsing.
1.127 + READ_BLOCK,
1.128 +
1.129 + // Reads mBlockTimecodeLength bytes of data into mBlockTimecode. When
1.130 + // mBlockTimecodeLength reaches 0, the timecode has been read. The sum
1.131 + // of mClusterTimecode and mBlockTimecode is stored as a pair with
1.132 + // mBlockOffset into the offset-to-time map.
1.133 + READ_BLOCK_TIMECODE,
1.134 +
1.135 + // Skip mSkipBytes of data before resuming parse at mNextState.
1.136 + SKIP_DATA,
1.137 +
1.138 + // Skip the content of an element. mVInt holds the element length.
1.139 + SKIP_ELEMENT
1.140 + };
1.141 +
1.142 + // Current state machine action.
1.143 + State mState;
1.144 +
1.145 + // Next state machine action. SKIP_DATA and READ_VINT_REST advance to
1.146 + // mNextState when the current action completes.
1.147 + State mNextState;
1.148 +
1.149 + // Match position within CLUSTER_ID. Used to find sync within arbitrary
1.150 + // data.
1.151 + uint32_t mClusterIDPos;
1.152 +
1.153 + // Variable length integer read from data.
1.154 + uint64_t mVInt;
1.155 +
1.156 + // Encoding length of mVInt. This is the total number of bytes used to
1.157 + // encoding mVInt's value.
1.158 + uint32_t mVIntLength;
1.159 +
1.160 + // Number of bytes of mVInt left to read. mVInt is complete once this
1.161 + // reaches 0.
1.162 + uint32_t mVIntLeft;
1.163 +
1.164 + // Size of the block currently being parsed. Any unused data within the
1.165 + // block is skipped once the block timecode has been parsed.
1.166 + uint64_t mBlockSize;
1.167 +
1.168 + // Cluster-level timecode.
1.169 + uint64_t mClusterTimecode;
1.170 +
1.171 + // Start offset of the block currently being parsed. Used as the byte
1.172 + // offset for the offset-to-time mapping once the block timecode has been
1.173 + // parsed.
1.174 + int64_t mBlockOffset;
1.175 +
1.176 + // Block-level timecode. This is summed with mClusterTimecode to produce
1.177 + // an absolute timecode for the offset-to-time mapping.
1.178 + int16_t mBlockTimecode;
1.179 +
1.180 + // Number of bytes of mBlockTimecode left to read.
1.181 + uint32_t mBlockTimecodeLength;
1.182 +
1.183 + // Count of bytes left to skip before resuming parse at mNextState.
1.184 + // Mostly used to skip block payload data after reading a block timecode.
1.185 + uint32_t mSkipBytes;
1.186 +};
1.187 +
1.188 +class WebMBufferedState MOZ_FINAL
1.189 +{
1.190 + NS_INLINE_DECL_REFCOUNTING(WebMBufferedState)
1.191 +
1.192 +public:
1.193 + WebMBufferedState() : mReentrantMonitor("WebMBufferedState") {
1.194 + MOZ_COUNT_CTOR(WebMBufferedState);
1.195 + }
1.196 +
1.197 + void NotifyDataArrived(const char* aBuffer, uint32_t aLength, int64_t aOffset);
1.198 + bool CalculateBufferedForRange(int64_t aStartOffset, int64_t aEndOffset,
1.199 + uint64_t* aStartTime, uint64_t* aEndTime);
1.200 + bool GetOffsetForTime(uint64_t aTime, int64_t* aOffset);
1.201 +
1.202 +private:
1.203 + // Private destructor, to discourage deletion outside of Release():
1.204 + ~WebMBufferedState() {
1.205 + MOZ_COUNT_DTOR(WebMBufferedState);
1.206 + }
1.207 +
1.208 + // Synchronizes access to the mTimeMapping array.
1.209 + ReentrantMonitor mReentrantMonitor;
1.210 +
1.211 + // Sorted (by offset) map of data offsets to timecodes. Populated
1.212 + // on the main thread as data is received and parsed by WebMBufferedParsers.
1.213 + nsTArray<WebMTimeDataOffset> mTimeMapping;
1.214 +
1.215 + // Sorted (by offset) live parser instances. Main thread only.
1.216 + nsTArray<WebMBufferedParser> mRangeParsers;
1.217 +};
1.218 +
1.219 +} // namespace mozilla
1.220 +
1.221 +#endif
