diff -r 000000000000 -r 6474c204b198 content/media/webm/WebMBufferedParser.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/media/webm/WebMBufferedParser.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,282 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsAlgorithm.h"
+#include "WebMBufferedParser.h"
+#include "mozilla/dom/TimeRanges.h"
+#include "nsThreadUtils.h"
+#include <algorithm>
+
+namespace mozilla {
+
+static uint32_t
+VIntLength(unsigned char aFirstByte, uint32_t* aMask)
+{
+  uint32_t count = 1;
+  uint32_t mask = 1 << 7;
+  while (count < 8) {
+    if ((aFirstByte & mask) != 0) {
+      break;
+    }
+    mask >>= 1;
+    count += 1;
+  }
+  if (aMask) {
+    *aMask = mask;
+  }
+  NS_ASSERTION(count >= 1 && count <= 8, "Insane VInt length.");
+  return count;
+}
+
+void WebMBufferedParser::Append(const unsigned char* aBuffer, uint32_t aLength,
+                                  nsTArray<WebMTimeDataOffset>& 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 WebMTimeDataOffset entries.
+        {
+          ReentrantMonitorAutoEnter mon(aReentrantMonitor);
+          uint32_t idx = aMapping.IndexOfFirstElementGt(mBlockOffset);
+          if (idx == 0 || !(aMapping[idx-1] == mBlockOffset)) {
+            WebMTimeDataOffset 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 = std::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;
+}
+
+bool WebMBufferedState::CalculateBufferedForRange(int64_t aStartOffset, int64_t aEndOffset,
+                                                    uint64_t* aStartTime, uint64_t* aEndTime)
+{
+  ReentrantMonitorAutoEnter mon(mReentrantMonitor);
+
+  // Find the first WebMTimeDataOffset at or after aStartOffset.
+  uint32_t start = mTimeMapping.IndexOfFirstElementGt(aStartOffset-1);
+  if (start == mTimeMapping.Length()) {
+    return false;
+  }
+
+  // Find the first WebMTimeDataOffset at or before aEndOffset.
+  uint32_t end = mTimeMapping.IndexOfFirstElementGt(aEndOffset-1);
+  if (end > 0) {
+    end -= 1;
+  }
+
+  // Range is empty.
+  if (end <= start) {
+    return false;
+  }
+
+  NS_ASSERTION(mTimeMapping[start].mOffset >= aStartOffset &&
+               mTimeMapping[end].mOffset <= aEndOffset,
+               "Computed time range must lie within data range.");
+  if (start > 0) {
+    NS_ASSERTION(mTimeMapping[start - 1].mOffset <= aStartOffset,
+                 "Must have found least WebMTimeDataOffset for start");
+  }
+  if (end < mTimeMapping.Length() - 1) {
+    NS_ASSERTION(mTimeMapping[end + 1].mOffset >= aEndOffset,
+                 "Must have found greatest WebMTimeDataOffset for end");
+  }
+
+  // The timestamp of the first media sample, in ns. We must subtract this
+  // from the ranges' start and end timestamps, so that those timestamps are
+  // normalized in the range [0,duration].
+
+  *aStartTime = mTimeMapping[start].mTimecode;
+  *aEndTime = mTimeMapping[end].mTimecode;
+  return true;
+}
+
+bool WebMBufferedState::GetOffsetForTime(uint64_t aTime, int64_t* aOffset)
+{
+  ReentrantMonitorAutoEnter mon(mReentrantMonitor);
+  WebMTimeDataOffset result(0,0);
+
+  for (uint32_t i = 0; i < mTimeMapping.Length(); ++i) {
+    WebMTimeDataOffset o = mTimeMapping[i];
+    if (o.mTimecode < aTime && o.mTimecode > result.mTimecode) {
+      result = o;
+    }
+  }
+
+  *aOffset = result.mOffset;
+  return true;
+}
+
+void WebMBufferedState::NotifyDataArrived(const char* aBuffer, uint32_t aLength, int64_t aOffset)
+{
+  NS_ASSERTION(NS_IsMainThread(), "Should be on main thread.");
+  uint32_t idx = mRangeParsers.IndexOfFirstElementGt(aOffset - 1);
+  if (idx == 0 || !(mRangeParsers[idx-1] == aOffset)) {
+    // If the incoming data overlaps an already parsed range, adjust the
+    // buffer so that we only reparse the new data.  It's also possible to
+    // have an overlap where the end of the incoming data is within an
+    // already parsed range, but we don't bother handling that other than by
+    // avoiding storing duplicate timecodes when the parser runs.
+    if (idx != mRangeParsers.Length() && mRangeParsers[idx].mStartOffset <= aOffset) {
+      // Complete overlap, skip parsing.
+      if (aOffset + aLength <= mRangeParsers[idx].mCurrentOffset) {
+        return;
+      }
+
+      // Partial overlap, adjust the buffer to parse only the new data.
+      int64_t adjust = mRangeParsers[idx].mCurrentOffset - aOffset;
+      NS_ASSERTION(adjust >= 0, "Overlap detection bug.");
+      aBuffer += adjust;
+      aLength -= uint32_t(adjust);
+    } else {
+      mRangeParsers.InsertElementAt(idx, WebMBufferedParser(aOffset));
+    }
+  }
+
+  mRangeParsers[idx].Append(reinterpret_cast<const unsigned char*>(aBuffer),
+                            aLength,
+                            mTimeMapping,
+                            mReentrantMonitor);
+
+  // Merge parsers with overlapping regions and clean up the remnants.
+  uint32_t i = 0;
+  while (i + 1 < mRangeParsers.Length()) {
+    if (mRangeParsers[i].mCurrentOffset >= mRangeParsers[i + 1].mStartOffset) {
+      mRangeParsers[i + 1].mStartOffset = mRangeParsers[i].mStartOffset;
+      mRangeParsers.RemoveElementAt(i);
+    } else {
+      i += 1;
+    }
+  }
+}
+
+} // namespace mozilla
+