diff -r 000000000000 -r 6474c204b198 content/media/wave/WaveReader.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/media/wave/WaveReader.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,685 @@
+/* -*- 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 "nsError.h"
+#include "AbstractMediaDecoder.h"
+#include "MediaResource.h"
+#include "WaveReader.h"
+#include "mozilla/dom/TimeRanges.h"
+#include "MediaDecoderStateMachine.h"
+#include "VideoUtils.h"
+#include "nsISeekableStream.h"
+
+#include <stdint.h>
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Endian.h"
+#include <algorithm>
+
+namespace mozilla {
+
+// Un-comment to enable logging of seek bisections.
+//#define SEEK_LOGGING
+
+#ifdef PR_LOGGING
+extern PRLogModuleInfo* gMediaDecoderLog;
+#define LOG(type, msg) PR_LOG(gMediaDecoderLog, type, msg)
+#ifdef SEEK_LOGGING
+#define SEEK_LOG(type, msg) PR_LOG(gMediaDecoderLog, type, msg)
+#else
+#define SEEK_LOG(type, msg)
+#endif
+#else
+#define LOG(type, msg)
+#define SEEK_LOG(type, msg)
+#endif
+
+struct waveIdToName {
+  uint32_t id;
+  nsCString name;
+};
+
+
+// Magic values that identify RIFF chunks we're interested in.
+static const uint32_t RIFF_CHUNK_MAGIC = 0x52494646;
+static const uint32_t WAVE_CHUNK_MAGIC = 0x57415645;
+static const uint32_t FRMT_CHUNK_MAGIC = 0x666d7420;
+static const uint32_t DATA_CHUNK_MAGIC = 0x64617461;
+static const uint32_t LIST_CHUNK_MAGIC = 0x4c495354;
+
+// Size of chunk header.  4 byte chunk header type and 4 byte size field.
+static const uint16_t CHUNK_HEADER_SIZE = 8;
+
+// Size of RIFF header.  RIFF chunk and 4 byte RIFF type.
+static const uint16_t RIFF_INITIAL_SIZE = CHUNK_HEADER_SIZE + 4;
+
+// Size of required part of format chunk.  Actual format chunks may be
+// extended (for non-PCM encodings), but we skip any extended data.
+static const uint16_t WAVE_FORMAT_CHUNK_SIZE = 16;
+
+// PCM encoding type from format chunk.  Linear PCM is the only encoding
+// supported by AudioStream.
+static const uint16_t WAVE_FORMAT_ENCODING_PCM = 1;
+
+// We reject files with more than this number of channels if we're decoding for
+// playback.
+static const uint8_t MAX_CHANNELS = 2;
+
+namespace {
+  uint32_t
+  ReadUint32BE(const char** aBuffer)
+  {
+    uint32_t result = BigEndian::readUint32(*aBuffer);
+    *aBuffer += sizeof(uint32_t);
+    return result;
+  }
+
+  uint32_t
+  ReadUint32LE(const char** aBuffer)
+  {
+    uint32_t result = LittleEndian::readUint32(*aBuffer);
+    *aBuffer += sizeof(uint32_t);
+    return result;
+  }
+
+  uint16_t
+  ReadUint16LE(const char** aBuffer)
+  {
+    uint16_t result = LittleEndian::readUint16(*aBuffer);
+    *aBuffer += sizeof(uint16_t);
+    return result;
+  }
+
+  int16_t
+  ReadInt16LE(const char** aBuffer)
+  {
+    uint16_t result = LittleEndian::readInt16(*aBuffer);
+    *aBuffer += sizeof(int16_t);
+    return result;
+  }
+
+  uint8_t
+  ReadUint8(const char** aBuffer)
+  {
+    uint8_t result = uint8_t((*aBuffer)[0]);
+    *aBuffer += sizeof(uint8_t);
+    return result;
+  }
+}
+
+WaveReader::WaveReader(AbstractMediaDecoder* aDecoder)
+  : MediaDecoderReader(aDecoder)
+{
+  MOZ_COUNT_CTOR(WaveReader);
+}
+
+WaveReader::~WaveReader()
+{
+  MOZ_COUNT_DTOR(WaveReader);
+}
+
+nsresult WaveReader::Init(MediaDecoderReader* aCloneDonor)
+{
+  return NS_OK;
+}
+
+nsresult WaveReader::ReadMetadata(MediaInfo* aInfo,
+                                  MetadataTags** aTags)
+{
+  NS_ASSERTION(mDecoder->OnDecodeThread(), "Should be on decode thread.");
+
+  bool loaded = LoadRIFFChunk();
+  if (!loaded) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsAutoPtr<dom::HTMLMediaElement::MetadataTags> tags;
+
+  bool loadAllChunks = LoadAllChunks(tags);
+  if (!loadAllChunks) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mInfo.mAudio.mHasAudio = true;
+  mInfo.mAudio.mRate = mSampleRate;
+  mInfo.mAudio.mChannels = mChannels;
+
+  *aInfo = mInfo;
+
+  *aTags = tags.forget();
+
+  ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
+
+  mDecoder->SetMediaDuration(
+    static_cast<int64_t>(BytesToTime(GetDataLength()) * USECS_PER_S));
+
+  return NS_OK;
+}
+
+template <typename T> T UnsignedByteToAudioSample(uint8_t aValue);
+template <typename T> T SignedShortToAudioSample(int16_t aValue);
+
+template <> inline float
+UnsignedByteToAudioSample<float>(uint8_t aValue)
+{
+  return aValue * (2.0f / UINT8_MAX) - 1.0f;
+}
+template <> inline int16_t
+UnsignedByteToAudioSample<int16_t>(uint8_t aValue)
+{
+  return int16_t(aValue * UINT16_MAX / UINT8_MAX + INT16_MIN);
+}
+
+template <> inline float
+SignedShortToAudioSample<float>(int16_t aValue)
+{
+  return AudioSampleToFloat(aValue);
+}
+template <> inline int16_t
+SignedShortToAudioSample<int16_t>(int16_t aValue)
+{
+  return aValue;
+}
+
+bool WaveReader::DecodeAudioData()
+{
+  NS_ASSERTION(mDecoder->OnDecodeThread(), "Should be on decode thread.");
+
+  int64_t pos = GetPosition() - mWavePCMOffset;
+  int64_t len = GetDataLength();
+  int64_t remaining = len - pos;
+  NS_ASSERTION(remaining >= 0, "Current wave position is greater than wave file length");
+
+  static const int64_t BLOCK_SIZE = 4096;
+  int64_t readSize = std::min(BLOCK_SIZE, remaining);
+  int64_t frames = readSize / mFrameSize;
+
+  static_assert(uint64_t(BLOCK_SIZE) < UINT_MAX /
+                sizeof(AudioDataValue) / MAX_CHANNELS,
+                "bufferSize calculation could overflow.");
+  const size_t bufferSize = static_cast<size_t>(frames * mChannels);
+  nsAutoArrayPtr<AudioDataValue> sampleBuffer(new AudioDataValue[bufferSize]);
+
+  static_assert(uint64_t(BLOCK_SIZE) < UINT_MAX / sizeof(char),
+                "BLOCK_SIZE too large for enumerator.");
+  nsAutoArrayPtr<char> dataBuffer(new char[static_cast<size_t>(readSize)]);
+
+  if (!ReadAll(dataBuffer, readSize)) {
+    return false;
+  }
+
+  // convert data to samples
+  const char* d = dataBuffer.get();
+  AudioDataValue* s = sampleBuffer.get();
+  for (int i = 0; i < frames; ++i) {
+    for (unsigned int j = 0; j < mChannels; ++j) {
+      if (mSampleFormat == FORMAT_U8) {
+        uint8_t v =  ReadUint8(&d);
+        *s++ = UnsignedByteToAudioSample<AudioDataValue>(v);
+      } else if (mSampleFormat == FORMAT_S16) {
+        int16_t v =  ReadInt16LE(&d);
+        *s++ = SignedShortToAudioSample<AudioDataValue>(v);
+      }
+    }
+  }
+
+  double posTime = BytesToTime(pos);
+  double readSizeTime = BytesToTime(readSize);
+  NS_ASSERTION(posTime <= INT64_MAX / USECS_PER_S, "posTime overflow");
+  NS_ASSERTION(readSizeTime <= INT64_MAX / USECS_PER_S, "readSizeTime overflow");
+  NS_ASSERTION(frames < INT32_MAX, "frames overflow");
+
+  mAudioQueue.Push(new AudioData(pos,
+                                 static_cast<int64_t>(posTime * USECS_PER_S),
+                                 static_cast<int64_t>(readSizeTime * USECS_PER_S),
+                                 static_cast<int32_t>(frames),
+                                 sampleBuffer.forget(),
+                                 mChannels));
+
+  return true;
+}
+
+bool WaveReader::DecodeVideoFrame(bool &aKeyframeSkip,
+                                      int64_t aTimeThreshold)
+{
+  NS_ASSERTION(mDecoder->OnDecodeThread(), "Should be on decode thread.");
+
+  return false;
+}
+
+nsresult WaveReader::Seek(int64_t aTarget, int64_t aStartTime, int64_t aEndTime, int64_t aCurrentTime)
+{
+  NS_ASSERTION(mDecoder->OnDecodeThread(), "Should be on decode thread.");
+  LOG(PR_LOG_DEBUG, ("%p About to seek to %lld", mDecoder, aTarget));
+  if (NS_FAILED(ResetDecode())) {
+    return NS_ERROR_FAILURE;
+  }
+  double d = BytesToTime(GetDataLength());
+  NS_ASSERTION(d < INT64_MAX / USECS_PER_S, "Duration overflow"); 
+  int64_t duration = static_cast<int64_t>(d * USECS_PER_S);
+  double seekTime = std::min(aTarget, duration) / static_cast<double>(USECS_PER_S);
+  int64_t position = RoundDownToFrame(static_cast<int64_t>(TimeToBytes(seekTime)));
+  NS_ASSERTION(INT64_MAX - mWavePCMOffset > position, "Integer overflow during wave seek");
+  position += mWavePCMOffset;
+  return mDecoder->GetResource()->Seek(nsISeekableStream::NS_SEEK_SET, position);
+}
+
+static double RoundToUsecs(double aSeconds) {
+  return floor(aSeconds * USECS_PER_S) / USECS_PER_S;
+}
+
+nsresult WaveReader::GetBuffered(dom::TimeRanges* aBuffered, int64_t aStartTime)
+{
+  if (!mInfo.HasAudio()) {
+    return NS_OK;
+  }
+  int64_t startOffset = mDecoder->GetResource()->GetNextCachedData(mWavePCMOffset);
+  while (startOffset >= 0) {
+    int64_t endOffset = mDecoder->GetResource()->GetCachedDataEnd(startOffset);
+    // Bytes [startOffset..endOffset] are cached.
+    NS_ASSERTION(startOffset >= mWavePCMOffset, "Integer underflow in GetBuffered");
+    NS_ASSERTION(endOffset >= mWavePCMOffset, "Integer underflow in GetBuffered");
+
+    // We need to round the buffered ranges' times to microseconds so that they
+    // have the same precision as the currentTime and duration attribute on 
+    // the media element.
+    aBuffered->Add(RoundToUsecs(BytesToTime(startOffset - mWavePCMOffset)),
+                   RoundToUsecs(BytesToTime(endOffset - mWavePCMOffset)));
+    startOffset = mDecoder->GetResource()->GetNextCachedData(endOffset);
+  }
+  return NS_OK;
+}
+
+bool
+WaveReader::ReadAll(char* aBuf, int64_t aSize, int64_t* aBytesRead)
+{
+  uint32_t got = 0;
+  if (aBytesRead) {
+    *aBytesRead = 0;
+  }
+  do {
+    uint32_t read = 0;
+    if (NS_FAILED(mDecoder->GetResource()->Read(aBuf + got, uint32_t(aSize - got), &read))) {
+      NS_WARNING("Resource read failed");
+      return false;
+    }
+    if (read == 0) {
+      return false;
+    }
+    got += read;
+    if (aBytesRead) {
+      *aBytesRead = got;
+    }
+  } while (got != aSize);
+  return true;
+}
+
+bool
+WaveReader::LoadRIFFChunk()
+{
+  char riffHeader[RIFF_INITIAL_SIZE];
+  const char* p = riffHeader;
+
+  NS_ABORT_IF_FALSE(mDecoder->GetResource()->Tell() == 0,
+                    "LoadRIFFChunk called when resource in invalid state");
+
+  if (!ReadAll(riffHeader, sizeof(riffHeader))) {
+    return false;
+  }
+
+  static_assert(sizeof(uint32_t) * 3 <= RIFF_INITIAL_SIZE,
+                "Reads would overflow riffHeader buffer.");
+  if (ReadUint32BE(&p) != RIFF_CHUNK_MAGIC) {
+    NS_WARNING("resource data not in RIFF format");
+    return false;
+  }
+
+  // Skip over RIFF size field.
+  p += sizeof(uint32_t);
+
+  if (ReadUint32BE(&p) != WAVE_CHUNK_MAGIC) {
+    NS_WARNING("Expected WAVE chunk");
+    return false;
+  }
+
+  return true;
+}
+
+bool
+WaveReader::LoadFormatChunk(uint32_t aChunkSize)
+{
+  uint32_t rate, channels, frameSize, sampleFormat;
+  char waveFormat[WAVE_FORMAT_CHUNK_SIZE];
+  const char* p = waveFormat;
+
+  // RIFF chunks are always word (two byte) aligned.
+  NS_ABORT_IF_FALSE(mDecoder->GetResource()->Tell() % 2 == 0,
+                    "LoadFormatChunk called with unaligned resource");
+
+  if (!ReadAll(waveFormat, sizeof(waveFormat))) {
+    return false;
+  }
+
+  static_assert(sizeof(uint16_t) +
+                sizeof(uint16_t) +
+                sizeof(uint32_t) +
+                4 +
+                sizeof(uint16_t) +
+                sizeof(uint16_t) <= sizeof(waveFormat),
+                "Reads would overflow waveFormat buffer.");
+  if (ReadUint16LE(&p) != WAVE_FORMAT_ENCODING_PCM) {
+    NS_WARNING("WAVE is not uncompressed PCM, compressed encodings are not supported");
+    return false;
+  }
+
+  channels = ReadUint16LE(&p);
+  rate = ReadUint32LE(&p);
+
+  // Skip over average bytes per second field.
+  p += 4;
+
+  frameSize = ReadUint16LE(&p);
+
+  sampleFormat = ReadUint16LE(&p);
+
+  // PCM encoded WAVEs are not expected to have an extended "format" chunk,
+  // but I have found WAVEs that have a extended "format" chunk with an
+  // extension size of 0 bytes.  Be polite and handle this rather than
+  // considering the file invalid.  This code skips any extension of the
+  // "format" chunk.
+  if (aChunkSize > WAVE_FORMAT_CHUNK_SIZE) {
+    char extLength[2];
+    const char* p = extLength;
+
+    if (!ReadAll(extLength, sizeof(extLength))) {
+      return false;
+    }
+
+    static_assert(sizeof(uint16_t) <= sizeof(extLength),
+                  "Reads would overflow extLength buffer.");
+    uint16_t extra = ReadUint16LE(&p);
+    if (aChunkSize - (WAVE_FORMAT_CHUNK_SIZE + 2) != extra) {
+      NS_WARNING("Invalid extended format chunk size");
+      return false;
+    }
+    extra += extra % 2;
+
+    if (extra > 0) {
+      static_assert(UINT16_MAX + (UINT16_MAX % 2) < UINT_MAX / sizeof(char),
+                    "chunkExtension array too large for iterator.");
+      nsAutoArrayPtr<char> chunkExtension(new char[extra]);
+      if (!ReadAll(chunkExtension.get(), extra)) {
+        return false;
+      }
+    }
+  }
+
+  // RIFF chunks are always word (two byte) aligned.
+  NS_ABORT_IF_FALSE(mDecoder->GetResource()->Tell() % 2 == 0,
+                    "LoadFormatChunk left resource unaligned");
+
+  // Make sure metadata is fairly sane.  The rate check is fairly arbitrary,
+  // but the channels check is intentionally limited to mono or stereo
+  // when the media is intended for direct playback because that's what the
+  // audio backend currently supports.
+  unsigned int actualFrameSize = (sampleFormat == 8 ? 1 : 2) * channels;
+  if (rate < 100 || rate > 96000 ||
+      (((channels < 1 || channels > MAX_CHANNELS) ||
+       (frameSize != 1 && frameSize != 2 && frameSize != 4)) &&
+       !mIgnoreAudioOutputFormat) ||
+       (sampleFormat != 8 && sampleFormat != 16) ||
+      frameSize != actualFrameSize) {
+    NS_WARNING("Invalid WAVE metadata");
+    return false;
+  }
+
+  ReentrantMonitorAutoEnter monitor(mDecoder->GetReentrantMonitor());
+  mSampleRate = rate;
+  mChannels = channels;
+  mFrameSize = frameSize;
+  if (sampleFormat == 8) {
+    mSampleFormat = FORMAT_U8;
+  } else {
+    mSampleFormat = FORMAT_S16;
+  }
+  return true;
+}
+
+bool
+WaveReader::FindDataOffset(uint32_t aChunkSize)
+{
+  // RIFF chunks are always word (two byte) aligned.
+  NS_ABORT_IF_FALSE(mDecoder->GetResource()->Tell() % 2 == 0,
+                    "FindDataOffset called with unaligned resource");
+
+  int64_t offset = mDecoder->GetResource()->Tell();
+  if (offset <= 0 || offset > UINT32_MAX) {
+    NS_WARNING("PCM data offset out of range");
+    return false;
+  }
+
+  ReentrantMonitorAutoEnter monitor(mDecoder->GetReentrantMonitor());
+  mWaveLength = aChunkSize;
+  mWavePCMOffset = uint32_t(offset);
+  return true;
+}
+
+double
+WaveReader::BytesToTime(int64_t aBytes) const
+{
+  NS_ABORT_IF_FALSE(aBytes >= 0, "Must be >= 0");
+  return float(aBytes) / mSampleRate / mFrameSize;
+}
+
+int64_t
+WaveReader::TimeToBytes(double aTime) const
+{
+  NS_ABORT_IF_FALSE(aTime >= 0.0f, "Must be >= 0");
+  return RoundDownToFrame(int64_t(aTime * mSampleRate * mFrameSize));
+}
+
+int64_t
+WaveReader::RoundDownToFrame(int64_t aBytes) const
+{
+  NS_ABORT_IF_FALSE(aBytes >= 0, "Must be >= 0");
+  return aBytes - (aBytes % mFrameSize);
+}
+
+int64_t
+WaveReader::GetDataLength()
+{
+  int64_t length = mWaveLength;
+  // If the decoder has a valid content length, and it's shorter than the
+  // expected length of the PCM data, calculate the playback duration from
+  // the content length rather than the expected PCM data length.
+  int64_t streamLength = mDecoder->GetResource()->GetLength();
+  if (streamLength >= 0) {
+    int64_t dataLength = std::max<int64_t>(0, streamLength - mWavePCMOffset);
+    length = std::min(dataLength, length);
+  }
+  return length;
+}
+
+int64_t
+WaveReader::GetPosition()
+{
+  return mDecoder->GetResource()->Tell();
+}
+
+bool
+WaveReader::GetNextChunk(uint32_t* aChunk, uint32_t* aChunkSize)
+{
+  NS_ABORT_IF_FALSE(aChunk, "Must have aChunk");
+  NS_ABORT_IF_FALSE(aChunkSize, "Must have aChunkSize");
+  NS_ABORT_IF_FALSE(mDecoder->GetResource()->Tell() % 2 == 0,
+                    "GetNextChunk called with unaligned resource");
+
+  char chunkHeader[CHUNK_HEADER_SIZE];
+  const char* p = chunkHeader;
+
+  if (!ReadAll(chunkHeader, sizeof(chunkHeader))) {
+    return false;
+  }
+
+  static_assert(sizeof(uint32_t) * 2 <= CHUNK_HEADER_SIZE,
+                "Reads would overflow chunkHeader buffer.");
+  *aChunk = ReadUint32BE(&p);
+  *aChunkSize = ReadUint32LE(&p);
+
+  return true;
+}
+
+bool
+WaveReader::LoadListChunk(uint32_t aChunkSize,
+                          nsAutoPtr<dom::HTMLMediaElement::MetadataTags> &aTags)
+{
+  // List chunks are always word (two byte) aligned.
+  NS_ABORT_IF_FALSE(mDecoder->GetResource()->Tell() % 2 == 0,
+                    "LoadListChunk called with unaligned resource");
+
+  static const unsigned int MAX_CHUNK_SIZE = 1 << 16;
+  static_assert(uint64_t(MAX_CHUNK_SIZE) < UINT_MAX / sizeof(char),
+                "MAX_CHUNK_SIZE too large for enumerator.");
+
+  if (aChunkSize > MAX_CHUNK_SIZE) {
+    return false;
+  }
+
+  nsAutoArrayPtr<char> chunk(new char[aChunkSize]);
+  if (!ReadAll(chunk.get(), aChunkSize)) {
+    return false;
+  }
+
+  static const uint32_t INFO_LIST_MAGIC = 0x494e464f;
+  const char *p = chunk.get();
+  if (ReadUint32BE(&p) != INFO_LIST_MAGIC) {
+    return false;
+  }
+
+  const waveIdToName ID_TO_NAME[] = {
+    { 0x49415254, NS_LITERAL_CSTRING("artist") },   // IART
+    { 0x49434d54, NS_LITERAL_CSTRING("comments") }, // ICMT
+    { 0x49474e52, NS_LITERAL_CSTRING("genre") },    // IGNR
+    { 0x494e414d, NS_LITERAL_CSTRING("name") },     // INAM
+  };
+
+  const char* const end = chunk.get() + aChunkSize;
+
+  aTags = new dom::HTMLMediaElement::MetadataTags;
+
+  while (p + 8 < end) {
+    uint32_t id = ReadUint32BE(&p);
+    // Uppercase tag id, inspired by GStreamer's Wave parser.
+    id &= 0xDFDFDFDF;
+
+    uint32_t length = ReadUint32LE(&p);
+
+    // Subchunk shall not exceed parent chunk.
+    if (p + length > end) {
+      break;
+    }
+
+    // Wrap the string, adjusting length to account for optional
+    // null termination in the chunk.
+    nsCString val(p, length);
+    if (length > 0 && val[length - 1] == '\0') {
+      val.SetLength(length - 1);
+    }
+
+    // Chunks in List::INFO are always word (two byte) aligned. So round up if
+    // necessary.
+    length += length % 2;
+    p += length;
+
+    if (!IsUTF8(val)) {
+      continue;
+    }
+
+    for (size_t i = 0; i < mozilla::ArrayLength(ID_TO_NAME); ++i) {
+      if (id == ID_TO_NAME[i].id) {
+        aTags->Put(ID_TO_NAME[i].name, val);
+        break;
+      }
+    }
+  }
+
+  return true;
+}
+
+bool
+WaveReader::LoadAllChunks(nsAutoPtr<dom::HTMLMediaElement::MetadataTags> &aTags)
+{
+  // Chunks are always word (two byte) aligned.
+  NS_ABORT_IF_FALSE(mDecoder->GetResource()->Tell() % 2 == 0,
+                    "LoadAllChunks called with unaligned resource");
+
+  bool loadFormatChunk = false;
+  bool findDataOffset = false;
+
+  for (;;) {
+    static const unsigned int CHUNK_HEADER_SIZE = 8;
+    char chunkHeader[CHUNK_HEADER_SIZE];
+    const char* p = chunkHeader;
+
+    if (!ReadAll(chunkHeader, sizeof(chunkHeader))) {
+      return false;
+    }
+
+    static_assert(sizeof(uint32_t) * 2 <= CHUNK_HEADER_SIZE,
+                  "Reads would overflow chunkHeader buffer.");
+
+    uint32_t magic = ReadUint32BE(&p);
+    uint32_t chunkSize = ReadUint32LE(&p);
+    int64_t chunkStart = GetPosition();
+
+    switch (magic) {
+      case FRMT_CHUNK_MAGIC:
+        loadFormatChunk = LoadFormatChunk(chunkSize);
+        if (!loadFormatChunk) {
+          return false;
+        }
+        break;
+
+      case LIST_CHUNK_MAGIC:
+        if (!aTags) {
+          LoadListChunk(chunkSize, aTags);
+        }
+        break;
+
+      case DATA_CHUNK_MAGIC:
+        findDataOffset = FindDataOffset(chunkSize);
+        return loadFormatChunk && findDataOffset;
+
+      default:
+        break;
+    }
+
+    // RIFF chunks are two-byte aligned, so round up if necessary.
+    chunkSize += chunkSize % 2;
+
+    // Move forward to next chunk
+    CheckedInt64 forward = CheckedInt64(chunkStart) + chunkSize - GetPosition();
+
+    if (!forward.isValid() || forward.value() < 0) {
+      return false;
+    }
+
+    static const int64_t MAX_CHUNK_SIZE = 1 << 16;
+    static_assert(uint64_t(MAX_CHUNK_SIZE) < UINT_MAX / sizeof(char),
+                  "MAX_CHUNK_SIZE too large for enumerator.");
+    nsAutoArrayPtr<char> chunk(new char[MAX_CHUNK_SIZE]);
+    while (forward.value() > 0) {
+      int64_t size = std::min(forward.value(), MAX_CHUNK_SIZE);
+      if (!ReadAll(chunk.get(), size)) {
+        return false;
+      }
+      forward -= size;
+    }
+  }
+
+  return false;
+}
+
+} // namespace mozilla