fune/dom/media/ogg/OggDemuxer.cpp

/* -*- 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 "OggDemuxer.h"
#include "OggRLBox.h"
#include "MediaDataDemuxer.h"
#include "OggCodecState.h"
#include "XiphExtradata.h"
#include "mozilla/AbstractThread.h"
#include "mozilla/Atomics.h"
#include "mozilla/PodOperations.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/SchedulerGroup.h"
#include "mozilla/SharedThreadPool.h"
#include "mozilla/Telemetry.h"
#include "mozilla/TimeStamp.h"
#include "nsAutoRef.h"
#include "nsError.h"

#include <algorithm>

extern mozilla::LazyLogModule gMediaDemuxerLog;
#define OGG_DEBUG(arg, ...)                                           \
  DDMOZ_LOG(gMediaDemuxerLog, mozilla::LogLevel::Debug, "::%s: " arg, \
            __func__, ##__VA_ARGS__)

// Un-comment to enable logging of seek bisections.
// #define SEEK_LOGGING
#ifdef SEEK_LOGGING
#  define SEEK_LOG(type, msg) MOZ_LOG(gMediaDemuxerLog, type, msg)
#else
#  define SEEK_LOG(type, msg)
#endif

#define CopyAndVerifyOrFail(t, cond, failed) \
  (t).copy_and_verify([&](auto val) {        \
    if (!(cond)) {                           \
      *(failed) = true;                      \
    }                                        \
    return val;                              \
  })

namespace mozilla {

using media::TimeInterval;
using media::TimeIntervals;
using media::TimeUnit;

// The number of microseconds of "fuzz" we use in a bisection search over
// HTTP. When we're seeking with fuzz, we'll stop the search if a bisection
// lands between the seek target and OGG_SEEK_FUZZ_USECS microseconds before the
// seek target.  This is becaue it's usually quicker to just keep downloading
// from an exisiting connection than to do another bisection inside that
// small range, which would open a new HTTP connetion.
static const uint32_t OGG_SEEK_FUZZ_USECS = 500000;

// The number of microseconds of "pre-roll" we use for Opus streams.
// The specification recommends 80 ms.
static const TimeUnit OGG_SEEK_OPUS_PREROLL = TimeUnit::FromMicroseconds(80000);

static Atomic<uint32_t> sStreamSourceID(0u);

OggDemuxer::nsAutoOggSyncState::nsAutoOggSyncState(rlbox_sandbox_ogg* aSandbox)
    : mSandbox(aSandbox) {
  if (mSandbox) {
    tainted_ogg<ogg_sync_state*> state =
        mSandbox->malloc_in_sandbox<ogg_sync_state>();
    MOZ_RELEASE_ASSERT(state != nullptr);
    mState = state.to_opaque();
    sandbox_invoke(*mSandbox, ogg_sync_init, mState);
  }
}
OggDemuxer::nsAutoOggSyncState::~nsAutoOggSyncState() {
  if (mSandbox) {
    sandbox_invoke(*mSandbox, ogg_sync_clear, mState);
    mSandbox->free_in_sandbox(rlbox::from_opaque(mState));
    tainted_ogg<ogg_sync_state*> null = nullptr;
    mState = null.to_opaque();
  }
}

/* static */
rlbox_sandbox_ogg* OggDemuxer::CreateSandbox() {
  rlbox_sandbox_ogg* sandbox = new rlbox_sandbox_ogg();
#ifdef MOZ_WASM_SANDBOXING_OGG
  bool success = sandbox->create_sandbox(false /* infallible */);
#else
  bool success = sandbox->create_sandbox();
#endif
  if (!success) {
    delete sandbox;
    sandbox = nullptr;
  }
  return sandbox;
}

void OggDemuxer::SandboxDestroy::operator()(rlbox_sandbox_ogg* sandbox) {
  if (sandbox) {
    sandbox->destroy_sandbox();
    delete sandbox;
  }
}

// Return the corresponding category in aKind based on the following specs.
// (https://www.whatwg.org/specs/web-apps/current-
// work/multipage/embedded-content.html#dom-audiotrack-kind) &
// (http://wiki.xiph.org/SkeletonHeaders)
const nsString OggDemuxer::GetKind(const nsCString& aRole) {
  if (aRole.Find("audio/main") != -1 || aRole.Find("video/main") != -1) {
    return u"main"_ns;
  } else if (aRole.Find("audio/alternate") != -1 ||
             aRole.Find("video/alternate") != -1) {
    return u"alternative"_ns;
  } else if (aRole.Find("audio/audiodesc") != -1) {
    return u"descriptions"_ns;
  } else if (aRole.Find("audio/described") != -1) {
    return u"main-desc"_ns;
  } else if (aRole.Find("audio/dub") != -1) {
    return u"translation"_ns;
  } else if (aRole.Find("audio/commentary") != -1) {
    return u"commentary"_ns;
  } else if (aRole.Find("video/sign") != -1) {
    return u"sign"_ns;
  } else if (aRole.Find("video/captioned") != -1) {
    return u"captions"_ns;
  } else if (aRole.Find("video/subtitled") != -1) {
    return u"subtitles"_ns;
  }
  return u""_ns;
}

void OggDemuxer::InitTrack(MessageField* aMsgInfo, TrackInfo* aInfo,
                           bool aEnable) {
  MOZ_ASSERT(aMsgInfo);
  MOZ_ASSERT(aInfo);

  nsCString* sName = aMsgInfo->mValuesStore.Get(eName);
  nsCString* sRole = aMsgInfo->mValuesStore.Get(eRole);
  nsCString* sTitle = aMsgInfo->mValuesStore.Get(eTitle);
  nsCString* sLanguage = aMsgInfo->mValuesStore.Get(eLanguage);
  aInfo->Init(sName ? NS_ConvertUTF8toUTF16(*sName) : EmptyString(),
              sRole ? GetKind(*sRole) : u""_ns,
              sTitle ? NS_ConvertUTF8toUTF16(*sTitle) : EmptyString(),
              sLanguage ? NS_ConvertUTF8toUTF16(*sLanguage) : EmptyString(),
              aEnable);
}

OggDemuxer::OggDemuxer(MediaResource* aResource)
    : mSandbox(CreateSandbox()),
      mTheoraState(nullptr),
      mVorbisState(nullptr),
      mOpusState(nullptr),
      mFlacState(nullptr),
      mOpusEnabled(MediaDecoder::IsOpusEnabled()),
      mSkeletonState(nullptr),
      mAudioOggState(aResource, mSandbox.get()),
      mVideoOggState(aResource, mSandbox.get()),
      mIsChained(false),
      mTimedMetadataEvent(nullptr),
      mOnSeekableEvent(nullptr) {
  MOZ_COUNT_CTOR(OggDemuxer);
  // aResource is referenced through inner m{Audio,Video}OffState members.
  DDLINKCHILD("resource", aResource);
}

OggDemuxer::~OggDemuxer() {
  MOZ_COUNT_DTOR(OggDemuxer);
  Reset(TrackInfo::kAudioTrack);
  Reset(TrackInfo::kVideoTrack);
}

void OggDemuxer::SetChainingEvents(TimedMetadataEventProducer* aMetadataEvent,
                                   MediaEventProducer<void>* aOnSeekableEvent) {
  mTimedMetadataEvent = aMetadataEvent;
  mOnSeekableEvent = aOnSeekableEvent;
}

bool OggDemuxer::HasAudio() const {
  return mVorbisState || mOpusState || mFlacState;
}

bool OggDemuxer::HasVideo() const { return mTheoraState; }

bool OggDemuxer::HaveStartTime() const { return mStartTime.isSome(); }

int64_t OggDemuxer::StartTime() const { return mStartTime.refOr(0); }

bool OggDemuxer::HaveStartTime(TrackInfo::TrackType aType) {
  return OggState(aType).mStartTime.isSome();
}

int64_t OggDemuxer::StartTime(TrackInfo::TrackType aType) {
  return OggState(aType).mStartTime.refOr(TimeUnit::Zero()).ToMicroseconds();
}

RefPtr<OggDemuxer::InitPromise> OggDemuxer::Init() {
  if (!mSandbox) {
    return InitPromise::CreateAndReject(NS_ERROR_OUT_OF_MEMORY, __func__);
  }
  const char RLBOX_OGG_RETURN_CODE_SAFE[] =
      "Return codes only control whether to early exit. Incorrect return codes "
      "will not lead to memory safety issues in the renderer.";

  int ret = sandbox_invoke(*mSandbox, ogg_sync_init,
                           OggSyncState(TrackInfo::kAudioTrack))
                .unverified_safe_because(RLBOX_OGG_RETURN_CODE_SAFE);
  if (ret != 0) {
    return InitPromise::CreateAndReject(NS_ERROR_OUT_OF_MEMORY, __func__);
  }
  ret = sandbox_invoke(*mSandbox, ogg_sync_init,
                       OggSyncState(TrackInfo::kVideoTrack))
            .unverified_safe_because(RLBOX_OGG_RETURN_CODE_SAFE);
  if (ret != 0) {
    return InitPromise::CreateAndReject(NS_ERROR_OUT_OF_MEMORY, __func__);
  }
  if (ReadMetadata() != NS_OK) {
    return InitPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_METADATA_ERR,
                                        __func__);
  }

  if (!GetNumberTracks(TrackInfo::kAudioTrack) &&
      !GetNumberTracks(TrackInfo::kVideoTrack)) {
    return InitPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_METADATA_ERR,
                                        __func__);
  }

  return InitPromise::CreateAndResolve(NS_OK, __func__);
}

OggCodecState* OggDemuxer::GetTrackCodecState(
    TrackInfo::TrackType aType) const {
  switch (aType) {
    case TrackInfo::kAudioTrack:
      if (mVorbisState) {
        return mVorbisState;
      } else if (mOpusState) {
        return mOpusState;
      } else {
        return mFlacState;
      }
    case TrackInfo::kVideoTrack:
      return mTheoraState;
    default:
      return 0;
  }
}

TrackInfo::TrackType OggDemuxer::GetCodecStateType(
    OggCodecState* aState) const {
  switch (aState->GetType()) {
    case OggCodecState::TYPE_THEORA:
      return TrackInfo::kVideoTrack;
    case OggCodecState::TYPE_OPUS:
    case OggCodecState::TYPE_VORBIS:
    case OggCodecState::TYPE_FLAC:
      return TrackInfo::kAudioTrack;
    default:
      return TrackInfo::kUndefinedTrack;
  }
}

uint32_t OggDemuxer::GetNumberTracks(TrackInfo::TrackType aType) const {
  switch (aType) {
    case TrackInfo::kAudioTrack:
      return HasAudio() ? 1 : 0;
    case TrackInfo::kVideoTrack:
      return HasVideo() ? 1 : 0;
    default:
      return 0;
  }
}

UniquePtr<TrackInfo> OggDemuxer::GetTrackInfo(TrackInfo::TrackType aType,
                                              size_t aTrackNumber) const {
  switch (aType) {
    case TrackInfo::kAudioTrack:
      return mInfo.mAudio.Clone();
    case TrackInfo::kVideoTrack:
      return mInfo.mVideo.Clone();
    default:
      return nullptr;
  }
}

already_AddRefed<MediaTrackDemuxer> OggDemuxer::GetTrackDemuxer(
    TrackInfo::TrackType aType, uint32_t aTrackNumber) {
  if (GetNumberTracks(aType) <= aTrackNumber) {
    return nullptr;
  }
  RefPtr<OggTrackDemuxer> e = new OggTrackDemuxer(this, aType, aTrackNumber);
  DDLINKCHILD("track demuxer", e.get());
  mDemuxers.AppendElement(e);

  return e.forget();
}

nsresult OggDemuxer::Reset(TrackInfo::TrackType aType) {
  // Discard any previously buffered packets/pages.
  if (mSandbox) {
    sandbox_invoke(*mSandbox, ogg_sync_reset, OggSyncState(aType));
  }
  OggCodecState* trackState = GetTrackCodecState(aType);
  if (trackState) {
    return trackState->Reset();
  }
  OggState(aType).mNeedKeyframe = true;
  return NS_OK;
}

bool OggDemuxer::ReadHeaders(TrackInfo::TrackType aType,
                             OggCodecState* aState) {
  while (!aState->DoneReadingHeaders()) {
    DemuxUntilPacketAvailable(aType, aState);
    OggPacketPtr packet = aState->PacketOut();
    if (!packet) {
      OGG_DEBUG("Ran out of header packets early; deactivating stream %" PRIu32,
                aState->mSerial);
      aState->Deactivate();
      return false;
    }

    // Local OggCodecState needs to decode headers in order to process
    // packet granulepos -> time mappings, etc.
    if (!aState->DecodeHeader(std::move(packet))) {
      OGG_DEBUG(
          "Failed to decode ogg header packet; deactivating stream %" PRIu32,
          aState->mSerial);
      aState->Deactivate();
      return false;
    }
  }

  return aState->Init();
}

void OggDemuxer::BuildSerialList(nsTArray<uint32_t>& aTracks) {
  // Obtaining seek index information for currently active bitstreams.
  if (HasVideo()) {
    aTracks.AppendElement(mTheoraState->mSerial);
  }
  if (HasAudio()) {
    if (mVorbisState) {
      aTracks.AppendElement(mVorbisState->mSerial);
    } else if (mOpusState) {
      aTracks.AppendElement(mOpusState->mSerial);
    }
  }
}

void OggDemuxer::SetupTarget(OggCodecState** aSavedState,
                             OggCodecState* aNewState) {
  if (*aSavedState) {
    (*aSavedState)->Reset();
  }

  if (aNewState->GetInfo()->GetAsAudioInfo()) {
    mInfo.mAudio = *aNewState->GetInfo()->GetAsAudioInfo();
  } else {
    mInfo.mVideo = *aNewState->GetInfo()->GetAsVideoInfo();
  }
  *aSavedState = aNewState;
}

void OggDemuxer::SetupTargetSkeleton() {
  // Setup skeleton related information after mVorbisState & mTheroState
  // being set (if they exist).
  if (mSkeletonState) {
    if (!HasAudio() && !HasVideo()) {
      // We have a skeleton track, but no audio or video, may as well disable
      // the skeleton, we can't do anything useful with this media.
      OGG_DEBUG("Deactivating skeleton stream %" PRIu32,
                mSkeletonState->mSerial);
      mSkeletonState->Deactivate();
    } else if (ReadHeaders(TrackInfo::kAudioTrack, mSkeletonState) &&
               mSkeletonState->HasIndex()) {
      // We don't particularly care about which track we are currently using
      // as both MediaResource points to the same content.
      // Extract the duration info out of the index, so we don't need to seek to
      // the end of resource to get it.
      nsTArray<uint32_t> tracks;
      BuildSerialList(tracks);
      int64_t duration = 0;
      if (NS_SUCCEEDED(mSkeletonState->GetDuration(tracks, duration))) {
        OGG_DEBUG("Got duration from Skeleton index %" PRId64, duration);
        mInfo.mMetadataDuration.emplace(TimeUnit::FromMicroseconds(duration));
      }
    }
  }
}

void OggDemuxer::SetupMediaTracksInfo(const nsTArray<uint32_t>& aSerials) {
  // For each serial number
  // 1. Retrieve a codecState from mCodecStore by this serial number.
  // 2. Retrieve a message field from mMsgFieldStore by this serial number.
  // 3. For now, skip if the serial number refers to a non-primary bitstream.
  // 4. Setup track and other audio/video related information per different
  // types.
  for (size_t i = 0; i < aSerials.Length(); i++) {
    uint32_t serial = aSerials[i];
    OggCodecState* codecState = mCodecStore.Get(serial);

    MessageField* msgInfo = nullptr;
    if (mSkeletonState) {
      mSkeletonState->mMsgFieldStore.Get(serial, &msgInfo);
    }

    OggCodecState* primeState = nullptr;
    switch (codecState->GetType()) {
      case OggCodecState::TYPE_THEORA:
        primeState = mTheoraState;
        break;
      case OggCodecState::TYPE_VORBIS:
        primeState = mVorbisState;
        break;
      case OggCodecState::TYPE_OPUS:
        primeState = mOpusState;
        break;
      case OggCodecState::TYPE_FLAC:
        primeState = mFlacState;
        break;
      default:
        break;
    }
    if (primeState && primeState == codecState) {
      bool isAudio = primeState->GetInfo()->GetAsAudioInfo();
      if (msgInfo) {
        InitTrack(
            msgInfo,
            isAudio ? static_cast<TrackInfo*>(&mInfo.mAudio) : &mInfo.mVideo,
            true);
      }
      FillTags(isAudio ? static_cast<TrackInfo*>(&mInfo.mAudio) : &mInfo.mVideo,
               primeState->GetTags());
    }
  }
}

void OggDemuxer::FillTags(TrackInfo* aInfo, UniquePtr<MetadataTags>&& aTags) {
  if (!aTags) {
    return;
  }
  UniquePtr<MetadataTags> tags(std::move(aTags));
  for (const auto& entry : *tags) {
    aInfo->mTags.AppendElement(MetadataTag(entry.GetKey(), entry.GetData()));
  }
}

nsresult OggDemuxer::ReadMetadata() {
  OGG_DEBUG("OggDemuxer::ReadMetadata called!");

  // We read packets until all bitstreams have read all their header packets.
  // We record the offset of the first non-header page so that we know
  // what page to seek to when seeking to the media start.

  // @FIXME we have to read all the header packets on all the streams
  // and THEN we can run SetupTarget*
  // @fixme fixme

  TrackInfo::TrackType tracks[2] = {TrackInfo::kAudioTrack,
                                    TrackInfo::kVideoTrack};

  nsTArray<OggCodecState*> bitstreams;
  nsTArray<uint32_t> serials;

  for (uint32_t i = 0; i < ArrayLength(tracks); i++) {
    tainted_ogg<ogg_page*> page = mSandbox->malloc_in_sandbox<ogg_page>();
    if (!page) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
    auto clean_page = MakeScopeExit([&] { mSandbox->free_in_sandbox(page); });

    bool readAllBOS = false;
    while (!readAllBOS) {
      if (!ReadOggPage(tracks[i], page.to_opaque())) {
        // Some kind of error...
        OGG_DEBUG("OggDemuxer::ReadOggPage failed? leaving ReadMetadata...");
        return NS_ERROR_FAILURE;
      }

      uint32_t serial = static_cast<uint32_t>(
          sandbox_invoke(*mSandbox, ogg_page_serialno, page)
              .unverified_safe_because(RLBOX_OGG_PAGE_SERIAL_REASON));

      if (!sandbox_invoke(*mSandbox, ogg_page_bos, page)
               .unverified_safe_because(
                   "If this value is incorrect, it would mean not all "
                   "bitstreams are read. This does not affect the memory "
                   "safety of the renderer.")) {
        // We've encountered a non Beginning Of Stream page. No more BOS pages
        // can follow in this Ogg segment, so there will be no other bitstreams
        // in the Ogg (unless it's invalid).
        readAllBOS = true;
      } else if (!mCodecStore.Contains(serial)) {
        // We've not encountered a stream with this serial number before. Create
        // an OggCodecState to demux it, and map that to the OggCodecState
        // in mCodecStates.
        OggCodecState* const codecState = mCodecStore.Add(
            serial,
            OggCodecState::Create(mSandbox.get(), page.to_opaque(), serial));
        bitstreams.AppendElement(codecState);
        serials.AppendElement(serial);
      }
      if (NS_FAILED(DemuxOggPage(tracks[i], page.to_opaque()))) {
        return NS_ERROR_FAILURE;
      }
    }
  }

  // We've read all BOS pages, so we know the streams contained in the media.
  // 1. Find the first encountered Theora/Vorbis/Opus bitstream, and configure
  //    it as the target A/V bitstream.
  // 2. Deactivate the rest of bitstreams for now, until we have MediaInfo
  //    support multiple track infos.
  for (uint32_t i = 0; i < bitstreams.Length(); ++i) {
    OggCodecState* s = bitstreams[i];
    if (s) {
      if (s->GetType() == OggCodecState::TYPE_THEORA &&
          ReadHeaders(TrackInfo::kVideoTrack, s)) {
        if (!mTheoraState) {
          SetupTarget(&mTheoraState, s);
        } else {
          s->Deactivate();
        }
      } else if (s->GetType() == OggCodecState::TYPE_VORBIS &&
                 ReadHeaders(TrackInfo::kAudioTrack, s)) {
        if (!mVorbisState) {
          SetupTarget(&mVorbisState, s);
        } else {
          s->Deactivate();
        }
      } else if (s->GetType() == OggCodecState::TYPE_OPUS &&
                 ReadHeaders(TrackInfo::kAudioTrack, s)) {
        if (mOpusEnabled) {
          if (!mOpusState) {
            SetupTarget(&mOpusState, s);
          } else {
            s->Deactivate();
          }
        } else {
          NS_WARNING(
              "Opus decoding disabled."
              " See media.opus.enabled in about:config");
        }
      } else if (s->GetType() == OggCodecState::TYPE_FLAC &&
                 ReadHeaders(TrackInfo::kAudioTrack, s)) {
        if (!mFlacState) {
          SetupTarget(&mFlacState, s);
        } else {
          s->Deactivate();
        }
      } else if (s->GetType() == OggCodecState::TYPE_SKELETON &&
                 !mSkeletonState) {
        mSkeletonState = static_cast<SkeletonState*>(s);
      } else {
        // Deactivate any non-primary bitstreams.
        s->Deactivate();
      }
    }
  }

  SetupTargetSkeleton();
  SetupMediaTracksInfo(serials);

  if (HasAudio() || HasVideo()) {
    int64_t startTime = -1;
    FindStartTime(startTime);
    if (startTime >= 0) {
      OGG_DEBUG("Detected stream start time %" PRId64, startTime);
      mStartTime.emplace(startTime);
    }

    if (mInfo.mMetadataDuration.isNothing() &&
        Resource(TrackInfo::kAudioTrack)->GetLength() >= 0) {
      // We didn't get a duration from the index or a Content-Duration header.
      // Seek to the end of file to find the end time.
      int64_t length = Resource(TrackInfo::kAudioTrack)->GetLength();

      MOZ_ASSERT(length > 0, "Must have a content length to get end time");

      int64_t endTime = RangeEndTime(TrackInfo::kAudioTrack, length);

      if (endTime != -1) {
        mInfo.mUnadjustedMetadataEndTime.emplace(
            TimeUnit::FromMicroseconds(endTime));
        mInfo.mMetadataDuration.emplace(
            TimeUnit::FromMicroseconds(endTime - mStartTime.refOr(0)));
        OGG_DEBUG("Got Ogg duration from seeking to end %" PRId64, endTime);
      }
    }
    if (mInfo.mMetadataDuration.isNothing()) {
      mInfo.mMetadataDuration.emplace(TimeUnit::FromInfinity());
    }
    if (HasAudio()) {
      mInfo.mAudio.mDuration = mInfo.mMetadataDuration.ref();
    }
    if (HasVideo()) {
      mInfo.mVideo.mDuration = mInfo.mMetadataDuration.ref();
    }
  } else {
    OGG_DEBUG("no audio or video tracks");
    return NS_ERROR_FAILURE;
  }

  OGG_DEBUG("success?!");
  return NS_OK;
}

void OggDemuxer::SetChained() {
  {
    if (mIsChained) {
      return;
    }
    mIsChained = true;
  }
  if (mOnSeekableEvent) {
    mOnSeekableEvent->Notify();
  }
}

bool OggDemuxer::ReadOggChain(const media::TimeUnit& aLastEndTime) {
  bool chained = false;
  OpusState* newOpusState = nullptr;
  VorbisState* newVorbisState = nullptr;
  FlacState* newFlacState = nullptr;
  UniquePtr<MetadataTags> tags;

  if (HasVideo() || HasSkeleton() || !HasAudio()) {
    return false;
  }

  tainted_ogg<ogg_page*> page = mSandbox->malloc_in_sandbox<ogg_page>();
  if (!page) {
    return false;
  }
  auto clean_page = MakeScopeExit([&] { mSandbox->free_in_sandbox(page); });
  if (!ReadOggPage(TrackInfo::kAudioTrack, page.to_opaque()) ||
      !sandbox_invoke(*mSandbox, ogg_page_bos, page)
           .unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON)) {
    // Chaining is only supported for audio only ogg files.
    return false;
  }

  uint32_t serial = static_cast<uint32_t>(
      sandbox_invoke(*mSandbox, ogg_page_serialno, page)
          .unverified_safe_because(
              "We are reading a new page with a serial number for the first "
              "time and will check if we have seen it before prior to use."));
  if (mCodecStore.Contains(serial)) {
    return false;
  }

  UniquePtr<OggCodecState> codecState(
      OggCodecState::Create(mSandbox.get(), page.to_opaque(), serial));
  if (!codecState) {
    return false;
  }

  if (mVorbisState && (codecState->GetType() == OggCodecState::TYPE_VORBIS)) {
    newVorbisState = static_cast<VorbisState*>(codecState.get());
  } else if (mOpusState &&
             (codecState->GetType() == OggCodecState::TYPE_OPUS)) {
    newOpusState = static_cast<OpusState*>(codecState.get());
  } else if (mFlacState &&
             (codecState->GetType() == OggCodecState::TYPE_FLAC)) {
    newFlacState = static_cast<FlacState*>(codecState.get());
  } else {
    return false;
  }

  OggCodecState* state;

  mCodecStore.Add(serial, std::move(codecState));
  state = mCodecStore.Get(serial);

  NS_ENSURE_TRUE(state != nullptr, false);

  if (NS_FAILED(state->PageIn(page.to_opaque()))) {
    return false;
  }

  MessageField* msgInfo = nullptr;
  if (mSkeletonState) {
    mSkeletonState->mMsgFieldStore.Get(serial, &msgInfo);
  }

  if ((newVorbisState && ReadHeaders(TrackInfo::kAudioTrack, newVorbisState)) &&
      (mVorbisState->GetInfo()->GetAsAudioInfo()->mRate ==
       newVorbisState->GetInfo()->GetAsAudioInfo()->mRate) &&
      (mVorbisState->GetInfo()->GetAsAudioInfo()->mChannels ==
       newVorbisState->GetInfo()->GetAsAudioInfo()->mChannels)) {
    SetupTarget(&mVorbisState, newVorbisState);
    OGG_DEBUG("New vorbis ogg link, serial=%d\n", mVorbisState->mSerial);

    if (msgInfo) {
      InitTrack(msgInfo, &mInfo.mAudio, true);
    }

    chained = true;
    tags = newVorbisState->GetTags();
  }

  if ((newOpusState && ReadHeaders(TrackInfo::kAudioTrack, newOpusState)) &&
      (mOpusState->GetInfo()->GetAsAudioInfo()->mRate ==
       newOpusState->GetInfo()->GetAsAudioInfo()->mRate) &&
      (mOpusState->GetInfo()->GetAsAudioInfo()->mChannels ==
       newOpusState->GetInfo()->GetAsAudioInfo()->mChannels)) {
    SetupTarget(&mOpusState, newOpusState);

    if (msgInfo) {
      InitTrack(msgInfo, &mInfo.mAudio, true);
    }

    chained = true;
    tags = newOpusState->GetTags();
  }

  if ((newFlacState && ReadHeaders(TrackInfo::kAudioTrack, newFlacState)) &&
      (mFlacState->GetInfo()->GetAsAudioInfo()->mRate ==
       newFlacState->GetInfo()->GetAsAudioInfo()->mRate) &&
      (mFlacState->GetInfo()->GetAsAudioInfo()->mChannels ==
       newFlacState->GetInfo()->GetAsAudioInfo()->mChannels)) {
    SetupTarget(&mFlacState, newFlacState);
    OGG_DEBUG("New flac ogg link, serial=%d\n", mFlacState->mSerial);

    if (msgInfo) {
      InitTrack(msgInfo, &mInfo.mAudio, true);
    }

    chained = true;
    tags = newFlacState->GetTags();
  }

  if (chained) {
    SetChained();
    mInfo.mMediaSeekable = false;
    mDecodedAudioDuration += aLastEndTime;
    if (mTimedMetadataEvent) {
      mTimedMetadataEvent->Notify(
          TimedMetadata(mDecodedAudioDuration, std::move(tags),
                        UniquePtr<MediaInfo>(new MediaInfo(mInfo))));
    }
    // Setup a new TrackInfo so that the MediaFormatReader will flush the
    // current decoder.
    mSharedAudioTrackInfo =
        new TrackInfoSharedPtr(mInfo.mAudio, ++sStreamSourceID);
    return true;
  }

  return false;
}

OggDemuxer::OggStateContext& OggDemuxer::OggState(TrackInfo::TrackType aType) {
  if (aType == TrackInfo::kVideoTrack) {
    return mVideoOggState;
  }
  return mAudioOggState;
}

tainted_opaque_ogg<ogg_sync_state*> OggDemuxer::OggSyncState(
    TrackInfo::TrackType aType) {
  return OggState(aType).mOggState.mState;
}

MediaResourceIndex* OggDemuxer::Resource(TrackInfo::TrackType aType) {
  return &OggState(aType).mResource;
}

MediaResourceIndex* OggDemuxer::CommonResource() {
  return &mAudioOggState.mResource;
}

bool OggDemuxer::ReadOggPage(TrackInfo::TrackType aType,
                             tainted_opaque_ogg<ogg_page*> aPage) {
  int ret = 0;
  while ((ret = sandbox_invoke(*mSandbox, ogg_sync_pageseek,
                               OggSyncState(aType), aPage)
                    .unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON)) <=
         0) {
    if (ret < 0) {
      // Lost page sync, have to skip up to next page.
      continue;
    }
    // Returns a buffer that can be written too
    // with the given size. This buffer is stored
    // in the ogg synchronisation structure.
    const uint32_t MIN_BUFFER_SIZE = 4096;
    tainted_ogg<char*> buffer_tainted = sandbox_invoke(
        *mSandbox, ogg_sync_buffer, OggSyncState(aType), MIN_BUFFER_SIZE);
    MOZ_ASSERT(buffer_tainted != nullptr, "ogg_sync_buffer failed");

    // Read from the resource into the buffer
    uint32_t bytesRead = 0;

    char* buffer = buffer_tainted.copy_and_verify_buffer_address(
        [](uintptr_t val) { return reinterpret_cast<char*>(val); },
        MIN_BUFFER_SIZE);

    nsresult rv = Resource(aType)->Read(buffer, MIN_BUFFER_SIZE, &bytesRead);
    if (NS_FAILED(rv) || !bytesRead) {
      // End of file or error.
      return false;
    }

    // Update the synchronisation layer with the number
    // of bytes written to the buffer
    ret = sandbox_invoke(*mSandbox, ogg_sync_wrote, OggSyncState(aType),
                         bytesRead)
              .unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON);
    NS_ENSURE_TRUE(ret == 0, false);
  }

  return true;
}

nsresult OggDemuxer::DemuxOggPage(TrackInfo::TrackType aType,
                                  tainted_opaque_ogg<ogg_page*> aPage) {
  tainted_ogg<int> serial = sandbox_invoke(*mSandbox, ogg_page_serialno, aPage);
  OggCodecState* codecState = mCodecStore.Get(static_cast<uint32_t>(
      serial.unverified_safe_because(RLBOX_OGG_PAGE_SERIAL_REASON)));
  if (codecState == nullptr) {
    OGG_DEBUG("encountered packet for unrecognized codecState");
    return NS_ERROR_FAILURE;
  }
  if (GetCodecStateType(codecState) != aType &&
      codecState->GetType() != OggCodecState::TYPE_SKELETON) {
    // Not a page we're interested in.
    return NS_OK;
  }
  if (NS_FAILED(codecState->PageIn(aPage))) {
    OGG_DEBUG("codecState->PageIn failed");
    return NS_ERROR_FAILURE;
  }
  return NS_OK;
}

bool OggDemuxer::IsSeekable() const {
  if (mIsChained) {
    return false;
  }
  return true;
}

UniquePtr<EncryptionInfo> OggDemuxer::GetCrypto() { return nullptr; }

ogg_packet* OggDemuxer::GetNextPacket(TrackInfo::TrackType aType) {
  OggCodecState* state = GetTrackCodecState(aType);
  ogg_packet* packet = nullptr;
  OggStateContext& context = OggState(aType);

  while (true) {
    if (packet) {
      Unused << state->PacketOut();
    }
    DemuxUntilPacketAvailable(aType, state);

    packet = state->PacketPeek();
    if (!packet) {
      break;
    }
    if (state->IsHeader(packet)) {
      continue;
    }
    if (context.mNeedKeyframe && !state->IsKeyframe(packet)) {
      continue;
    }
    context.mNeedKeyframe = false;
    break;
  }

  return packet;
}

void OggDemuxer::DemuxUntilPacketAvailable(TrackInfo::TrackType aType,
                                           OggCodecState* aState) {
  while (!aState->IsPacketReady()) {
    OGG_DEBUG("no packet yet, reading some more");
    tainted_ogg<ogg_page*> page = mSandbox->malloc_in_sandbox<ogg_page>();
    MOZ_RELEASE_ASSERT(page != nullptr);
    auto clean_page = MakeScopeExit([&] { mSandbox->free_in_sandbox(page); });
    if (!ReadOggPage(aType, page.to_opaque())) {
      OGG_DEBUG("no more pages to read in resource?");
      return;
    }
    DemuxOggPage(aType, page.to_opaque());
  }
}

TimeIntervals OggDemuxer::GetBuffered(TrackInfo::TrackType aType) {
  if (!HaveStartTime(aType)) {
    return TimeIntervals();
  }
  if (mIsChained) {
    return TimeIntervals::Invalid();
  }
  TimeIntervals buffered;
  // HasAudio and HasVideo are not used here as they take a lock and cause
  // a deadlock. Accessing mInfo doesn't require a lock - it doesn't change
  // after metadata is read.
  if (!mInfo.HasValidMedia()) {
    // No need to search through the file if there are no audio or video tracks
    return buffered;
  }

  AutoPinned<MediaResource> resource(Resource(aType)->GetResource());
  MediaByteRangeSet ranges;
  nsresult res = resource->GetCachedRanges(ranges);
  NS_ENSURE_SUCCESS(res, TimeIntervals::Invalid());

  const char time_interval_reason[] =
      "Even if this computation is incorrect due to the reliance on tainted "
      "values, only the search for the time interval or the time interval "
      "returned will be affected. However this will not result in a memory "
      "safety vulnerabilty in the Firefox renderer.";

  // Traverse across the buffered byte ranges, determining the time ranges
  // they contain. MediaResource::GetNextCachedData(offset) returns -1 when
  // offset is after the end of the media resource, or there's no more cached
  // data after the offset. This loop will run until we've checked every
  // buffered range in the media, in increasing order of offset.
  nsAutoOggSyncState sync(mSandbox.get());
  for (uint32_t index = 0; index < ranges.Length(); index++) {
    // Ensure the offsets are after the header pages.
    int64_t startOffset = ranges[index].mStart;
    int64_t endOffset = ranges[index].mEnd;

    // Because the granulepos time is actually the end time of the page,
    // we special-case (startOffset == 0) so that the first
    // buffered range always appears to be buffered from the media start
    // time, rather than from the end-time of the first page.
    int64_t startTime = (startOffset == 0) ? StartTime() : -1;

    // Find the start time of the range. Read pages until we find one with a
    // granulepos which we can convert into a timestamp to use as the time of
    // the start of the buffered range.
    sandbox_invoke(*mSandbox, ogg_sync_reset, sync.mState);
    tainted_ogg<ogg_page*> page = mSandbox->malloc_in_sandbox<ogg_page>();
    if (!page) {
      return TimeIntervals::Invalid();
    }
    auto clean_page = MakeScopeExit([&] { mSandbox->free_in_sandbox(page); });

    while (startTime == -1) {
      int32_t discard;
      PageSyncResult pageSyncResult =
          PageSync(mSandbox.get(), Resource(aType), sync.mState, true,
                   startOffset, endOffset, page, discard);
      if (pageSyncResult == PAGE_SYNC_ERROR) {
        return TimeIntervals::Invalid();
      } else if (pageSyncResult == PAGE_SYNC_END_OF_RANGE) {
        // Hit the end of range without reading a page, give up trying to
        // find a start time for this buffered range, skip onto the next one.
        break;
      }

      int64_t granulepos = sandbox_invoke(*mSandbox, ogg_page_granulepos, page)
                               .unverified_safe_because(time_interval_reason);
      if (granulepos == -1) {
        // Page doesn't have an end time, advance to the next page
        // until we find one.

        bool failedPageLenVerify = false;
        // Page length should be under 64Kb according to
        // https://xiph.org/ogg/doc/libogg/ogg_page.html
        long pageLength =
            CopyAndVerifyOrFail(page->header_len + page->body_len,
                                val <= 64 * 1024, &failedPageLenVerify);
        if (failedPageLenVerify) {
          return TimeIntervals::Invalid();
        }

        startOffset += pageLength;
        continue;
      }

      tainted_ogg<uint32_t> serial = rlbox::sandbox_static_cast<uint32_t>(
          sandbox_invoke(*mSandbox, ogg_page_serialno, page));
      if (aType == TrackInfo::kAudioTrack && mVorbisState &&
          (serial == mVorbisState->mSerial)
              .unverified_safe_because(time_interval_reason)) {
        startTime = mVorbisState->Time(granulepos);
        MOZ_ASSERT(startTime > 0, "Must have positive start time");
      } else if (aType == TrackInfo::kAudioTrack && mOpusState &&
                 (serial == mOpusState->mSerial)
                     .unverified_safe_because(time_interval_reason)) {
        startTime = mOpusState->Time(granulepos);
        MOZ_ASSERT(startTime > 0, "Must have positive start time");
      } else if (aType == TrackInfo::kAudioTrack && mFlacState &&
                 (serial == mFlacState->mSerial)
                     .unverified_safe_because(time_interval_reason)) {
        startTime = mFlacState->Time(granulepos);
        MOZ_ASSERT(startTime > 0, "Must have positive start time");
      } else if (aType == TrackInfo::kVideoTrack && mTheoraState &&
                 (serial == mTheoraState->mSerial)
                     .unverified_safe_because(time_interval_reason)) {
        startTime = mTheoraState->Time(granulepos);
        MOZ_ASSERT(startTime > 0, "Must have positive start time");
      } else if (mCodecStore.Contains(
                     serial.unverified_safe_because(time_interval_reason))) {
        // Stream is not the theora or vorbis stream we're playing,
        // but is one that we have header data for.

        bool failedPageLenVerify = false;
        // Page length should be under 64Kb according to
        // https://xiph.org/ogg/doc/libogg/ogg_page.html
        long pageLength =
            CopyAndVerifyOrFail(page->header_len + page->body_len,
                                val <= 64 * 1024, &failedPageLenVerify);
        if (failedPageLenVerify) {
          return TimeIntervals::Invalid();
        }

        startOffset += pageLength;
        continue;
      } else {
        // Page is for a stream we don't know about (possibly a chained
        // ogg), return OK to abort the finding any further ranges. This
        // prevents us searching through the rest of the media when we
        // may not be able to extract timestamps from it.
        SetChained();
        return buffered;
      }
    }

    if (startTime != -1) {
      // We were able to find a start time for that range, see if we can
      // find an end time.
      int64_t endTime = RangeEndTime(aType, startOffset, endOffset, true);
      if (endTime > startTime) {
        buffered +=
            TimeInterval(TimeUnit::FromMicroseconds(startTime - StartTime()),
                         TimeUnit::FromMicroseconds(endTime - StartTime()));
      }
    }
  }

  return buffered;
}

void OggDemuxer::FindStartTime(int64_t& aOutStartTime) {
  // Extract the start times of the bitstreams in order to calculate
  // the duration.
  int64_t videoStartTime = INT64_MAX;
  int64_t audioStartTime = INT64_MAX;

  if (HasVideo()) {
    FindStartTime(TrackInfo::kVideoTrack, videoStartTime);
    if (videoStartTime != INT64_MAX) {
      OGG_DEBUG("OggDemuxer::FindStartTime() video=%" PRId64, videoStartTime);
      mVideoOggState.mStartTime =
          Some(TimeUnit::FromMicroseconds(videoStartTime));
    }
  }
  if (HasAudio()) {
    FindStartTime(TrackInfo::kAudioTrack, audioStartTime);
    if (audioStartTime != INT64_MAX) {
      OGG_DEBUG("OggDemuxer::FindStartTime() audio=%" PRId64, audioStartTime);
      mAudioOggState.mStartTime =
          Some(TimeUnit::FromMicroseconds(audioStartTime));
    }
  }

  int64_t startTime = std::min(videoStartTime, audioStartTime);
  if (startTime != INT64_MAX) {
    aOutStartTime = startTime;
  }
}

void OggDemuxer::FindStartTime(TrackInfo::TrackType aType,
                               int64_t& aOutStartTime) {
  int64_t startTime = INT64_MAX;

  OggCodecState* state = GetTrackCodecState(aType);
  ogg_packet* pkt = GetNextPacket(aType);
  if (pkt) {
    startTime = state->PacketStartTime(pkt);
  }

  if (startTime != INT64_MAX) {
    aOutStartTime = startTime;
  }
}

nsresult OggDemuxer::SeekInternal(TrackInfo::TrackType aType,
                                  const TimeUnit& aTarget) {
  int64_t target = aTarget.ToMicroseconds();
  OGG_DEBUG("About to seek to %" PRId64, target);
  nsresult res;
  int64_t adjustedTarget = target;
  int64_t startTime = StartTime(aType);
  int64_t endTime = mInfo.mMetadataDuration->ToMicroseconds() + startTime;
  if (aType == TrackInfo::kAudioTrack && mOpusState) {
    adjustedTarget =
        std::max(startTime, target - OGG_SEEK_OPUS_PREROLL.ToMicroseconds());
  }

  if (!HaveStartTime(aType) || adjustedTarget == startTime) {
    // We've seeked to the media start or we can't seek.
    // Just seek to the offset of the first content page.
    res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, 0);
    NS_ENSURE_SUCCESS(res, res);

    res = Reset(aType);
    NS_ENSURE_SUCCESS(res, res);
  } else {
    // TODO: This may seek back unnecessarily far in the video, but we don't
    // have a way of asking Skeleton to seek to a different target for each
    // stream yet. Using adjustedTarget here is at least correct, if slow.
    IndexedSeekResult sres = SeekToKeyframeUsingIndex(aType, adjustedTarget);
    NS_ENSURE_TRUE(sres != SEEK_FATAL_ERROR, NS_ERROR_FAILURE);
    if (sres == SEEK_INDEX_FAIL) {
      // No index or other non-fatal index-related failure. Try to seek
      // using a bisection search. Determine the already downloaded data
      // in the media cache, so we can try to seek in the cached data first.
      AutoTArray<SeekRange, 16> ranges;
      res = GetSeekRanges(aType, ranges);
      NS_ENSURE_SUCCESS(res, res);

      // Figure out if the seek target lies in a buffered range.
      SeekRange r =
          SelectSeekRange(aType, ranges, target, startTime, endTime, true);

      if (!r.IsNull()) {
        // We know the buffered range in which the seek target lies, do a
        // bisection search in that buffered range.
        res = SeekInBufferedRange(aType, target, adjustedTarget, startTime,
                                  endTime, ranges, r);
        NS_ENSURE_SUCCESS(res, res);
      } else {
        // The target doesn't lie in a buffered range. Perform a bisection
        // search over the whole media, using the known buffered ranges to
        // reduce the search space.
        res = SeekInUnbuffered(aType, target, startTime, endTime, ranges);
        NS_ENSURE_SUCCESS(res, res);
      }
    }
  }

  // Demux forwards until we find the first keyframe prior the target.
  // there may be non-keyframes in the page before the keyframe.
  // Additionally, we may have seeked to the first page referenced by the
  // page index which may be quite far off the target.
  // When doing fastSeek we display the first frame after the seek, so
  // we need to advance the decode to the keyframe otherwise we'll get
  // visual artifacts in the first frame output after the seek.
  OggCodecState* state = GetTrackCodecState(aType);
  OggPacketQueue tempPackets;
  bool foundKeyframe = false;
  while (true) {
    DemuxUntilPacketAvailable(aType, state);
    ogg_packet* packet = state->PacketPeek();
    if (packet == nullptr) {
      OGG_DEBUG("End of stream reached before keyframe found in indexed seek");
      break;
    }
    int64_t startTstamp = state->PacketStartTime(packet);
    if (foundKeyframe && startTstamp > adjustedTarget) {
      break;
    }
    if (state->IsKeyframe(packet)) {
      OGG_DEBUG("keyframe found after seeking at %" PRId64, startTstamp);
      tempPackets.Erase();
      foundKeyframe = true;
    }
    if (foundKeyframe && startTstamp == adjustedTarget) {
      break;
    }
    if (foundKeyframe) {
      tempPackets.Append(state->PacketOut());
    } else {
      // Discard video packets before the first keyframe.
      Unused << state->PacketOut();
    }
  }
  // Re-add all packet into the codec state in order.
  state->PushFront(std::move(tempPackets));

  return NS_OK;
}

OggDemuxer::IndexedSeekResult OggDemuxer::RollbackIndexedSeek(
    TrackInfo::TrackType aType, int64_t aOffset) {
  if (mSkeletonState) {
    mSkeletonState->Deactivate();
  }
  nsresult res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, aOffset);
  NS_ENSURE_SUCCESS(res, SEEK_FATAL_ERROR);
  return SEEK_INDEX_FAIL;
}

OggDemuxer::IndexedSeekResult OggDemuxer::SeekToKeyframeUsingIndex(
    TrackInfo::TrackType aType, int64_t aTarget) {
  if (!HasSkeleton() || !mSkeletonState->HasIndex()) {
    return SEEK_INDEX_FAIL;
  }
  // We have an index from the Skeleton track, try to use it to seek.
  AutoTArray<uint32_t, 2> tracks;
  BuildSerialList(tracks);
  SkeletonState::nsSeekTarget keyframe;
  if (NS_FAILED(mSkeletonState->IndexedSeekTarget(aTarget, tracks, keyframe))) {
    // Could not locate a keypoint for the target in the index.
    return SEEK_INDEX_FAIL;
  }

  // Remember original resource read cursor position so we can rollback on
  // failure.
  int64_t tell = Resource(aType)->Tell();

  // Seek to the keypoint returned by the index.
  if (keyframe.mKeyPoint.mOffset > Resource(aType)->GetLength() ||
      keyframe.mKeyPoint.mOffset < 0) {
    // Index must be invalid.
    return RollbackIndexedSeek(aType, tell);
  }
  OGG_DEBUG("Seeking using index to keyframe at offset %" PRId64 "\n",
            keyframe.mKeyPoint.mOffset);
  nsresult res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET,
                                       keyframe.mKeyPoint.mOffset);
  NS_ENSURE_SUCCESS(res, SEEK_FATAL_ERROR);

  // We've moved the read set, so reset decode.
  res = Reset(aType);
  NS_ENSURE_SUCCESS(res, SEEK_FATAL_ERROR);

  // Check that the page the index thinks is exactly here is actually exactly
  // here. If not, the index is invalid.
  tainted_ogg<ogg_page*> page = mSandbox->malloc_in_sandbox<ogg_page>();
  if (!page) {
    return SEEK_INDEX_FAIL;
  }
  auto clean_page = MakeScopeExit([&] { mSandbox->free_in_sandbox(page); });
  int skippedBytes = 0;
  PageSyncResult syncres =
      PageSync(mSandbox.get(), Resource(aType), OggSyncState(aType), false,
               keyframe.mKeyPoint.mOffset, Resource(aType)->GetLength(), page,
               skippedBytes);
  NS_ENSURE_TRUE(syncres != PAGE_SYNC_ERROR, SEEK_FATAL_ERROR);
  if (syncres != PAGE_SYNC_OK || skippedBytes != 0) {
    OGG_DEBUG(
        "Indexed-seek failure: Ogg Skeleton Index is invalid "
        "or sync error after seek");
    return RollbackIndexedSeek(aType, tell);
  }
  uint32_t serial = static_cast<uint32_t>(
      sandbox_invoke(*mSandbox, ogg_page_serialno, page)
          .unverified_safe_because(
              "Serial is only used to locate the correct page. If the serial "
              "is incorrect the the renderer would just fail to seek with an "
              "error code. This would not lead to any memory safety bugs."));
  if (serial != keyframe.mSerial) {
    // Serialno of page at offset isn't what the index told us to expect.
    // Assume the index is invalid.
    return RollbackIndexedSeek(aType, tell);
  }
  OggCodecState* codecState = mCodecStore.Get(serial);
  if (codecState && codecState->mActive &&
      sandbox_invoke(*mSandbox, ogg_stream_pagein, codecState->mState, page)
              .unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) != 0) {
    // Couldn't insert page into the ogg resource, or somehow the resource
    // is no longer active.
    return RollbackIndexedSeek(aType, tell);
  }
  return SEEK_OK;
}

// Reads a page from the media resource.
OggDemuxer::PageSyncResult OggDemuxer::PageSync(
    rlbox_sandbox_ogg* aSandbox, MediaResourceIndex* aResource,
    tainted_opaque_ogg<ogg_sync_state*> aState, bool aCachedDataOnly,
    int64_t aOffset, int64_t aEndOffset, tainted_ogg<ogg_page*> aPage,
    int& aSkippedBytes) {
  aSkippedBytes = 0;
  // Sync to the next page.
  tainted_ogg<int> ret = 0;
  uint32_t bytesRead = 0;
  int64_t readHead = aOffset;
  while (ret.unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) <= 0) {
    tainted_ogg<long> seek_ret =
        sandbox_invoke(*aSandbox, ogg_sync_pageseek, aState, aPage);

    // We aren't really verifying the value of seek_ret below.
    // We are merely ensuring that it won't overflow an integer.
    // However we are assigning the value to ret which is marked tainted, so
    // this is fine.
    bool failedVerify = false;
    CheckedInt<int> checker;
    ret = CopyAndVerifyOrFail(
        seek_ret, (static_cast<void>(checker = val), checker.isValid()),
        &failedVerify);
    if (failedVerify) {
      return PAGE_SYNC_ERROR;
    }

    if (ret.unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) == 0) {
      const int page_step_val = PAGE_STEP;
      tainted_ogg<char*> buffer_tainted =
          sandbox_invoke(*aSandbox, ogg_sync_buffer, aState, page_step_val);
      MOZ_ASSERT(buffer_tainted != nullptr, "Must have a buffer");

      // Read from the file into the buffer
      int64_t bytesToRead =
          std::min(static_cast<int64_t>(PAGE_STEP), aEndOffset - readHead);
      MOZ_ASSERT(bytesToRead <= UINT32_MAX, "bytesToRead range check");
      if (bytesToRead <= 0) {
        return PAGE_SYNC_END_OF_RANGE;
      }
      char* buffer = buffer_tainted.copy_and_verify_buffer_address(
          [](uintptr_t val) { return reinterpret_cast<char*>(val); },
          static_cast<size_t>(bytesToRead));

      nsresult rv = NS_OK;
      if (aCachedDataOnly) {
        rv = aResource->GetResource()->ReadFromCache(
            buffer, readHead, static_cast<uint32_t>(bytesToRead));
        NS_ENSURE_SUCCESS(rv, PAGE_SYNC_ERROR);
        bytesRead = static_cast<uint32_t>(bytesToRead);
      } else {
        rv = aResource->Seek(nsISeekableStream::NS_SEEK_SET, readHead);
        NS_ENSURE_SUCCESS(rv, PAGE_SYNC_ERROR);
        rv = aResource->Read(buffer, static_cast<uint32_t>(bytesToRead),
                             &bytesRead);
        NS_ENSURE_SUCCESS(rv, PAGE_SYNC_ERROR);
      }
      if (bytesRead == 0 && NS_SUCCEEDED(rv)) {
        // End of file.
        return PAGE_SYNC_END_OF_RANGE;
      }
      readHead += bytesRead;

      // Update the synchronisation layer with the number
      // of bytes written to the buffer
      ret = sandbox_invoke(*aSandbox, ogg_sync_wrote, aState, bytesRead);
      NS_ENSURE_TRUE(
          ret.unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) == 0,
          PAGE_SYNC_ERROR);
      continue;
    }

    if (ret.unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) < 0) {
      MOZ_ASSERT(aSkippedBytes >= 0, "Offset >= 0");
      bool failedSkippedBytesVerify = false;
      ret.copy_and_verify([&](int val) {
        int64_t result = static_cast<int64_t>(aSkippedBytes) - val;
        if (result > std::numeric_limits<int>::max() ||
            result > (aEndOffset - aOffset) || result < 0) {
          failedSkippedBytesVerify = true;
        } else {
          aSkippedBytes = result;
        }
      });
      if (failedSkippedBytesVerify) {
        return PAGE_SYNC_ERROR;
      }
      continue;
    }
  }

  return PAGE_SYNC_OK;
}

// OggTrackDemuxer
OggTrackDemuxer::OggTrackDemuxer(OggDemuxer* aParent,
                                 TrackInfo::TrackType aType,
                                 uint32_t aTrackNumber)
    : mParent(aParent), mType(aType) {
  mInfo = mParent->GetTrackInfo(aType, aTrackNumber);
  MOZ_ASSERT(mInfo);
}

OggTrackDemuxer::~OggTrackDemuxer() = default;

UniquePtr<TrackInfo> OggTrackDemuxer::GetInfo() const { return mInfo->Clone(); }

RefPtr<OggTrackDemuxer::SeekPromise> OggTrackDemuxer::Seek(
    const TimeUnit& aTime) {
  // Seeks to aTime. Upon success, SeekPromise will be resolved with the
  // actual time seeked to. Typically the random access point time
  mQueuedSample = nullptr;
  TimeUnit seekTime = aTime;
  if (mParent->SeekInternal(mType, aTime) == NS_OK) {
    RefPtr<MediaRawData> sample(NextSample());

    // Check what time we actually seeked to.
    if (sample != nullptr) {
      seekTime = sample->mTime;
      OGG_DEBUG("%p seeked to time %" PRId64, this, seekTime.ToMicroseconds());
    }
    mQueuedSample = sample;

    return SeekPromise::CreateAndResolve(seekTime, __func__);
  } else {
    return SeekPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_DEMUXER_ERR,
                                        __func__);
  }
}

RefPtr<MediaRawData> OggTrackDemuxer::NextSample() {
  if (mQueuedSample) {
    RefPtr<MediaRawData> nextSample = mQueuedSample;
    mQueuedSample = nullptr;
    if (mType == TrackInfo::kAudioTrack) {
      nextSample->mTrackInfo = mParent->mSharedAudioTrackInfo;
    }
    return nextSample;
  }
  ogg_packet* packet = mParent->GetNextPacket(mType);
  if (!packet) {
    return nullptr;
  }
  // Check the eos state in case we need to look for chained streams.
  bool eos = packet->e_o_s;
  OggCodecState* state = mParent->GetTrackCodecState(mType);
  RefPtr<MediaRawData> data = state->PacketOutAsMediaRawData();
  // ogg allows 'nil' packets, that are EOS and of size 0.
  if (!data || (data->mEOS && data->Size() == 0)) {
    return nullptr;
  }
  if (mType == TrackInfo::kAudioTrack) {
    data->mTrackInfo = mParent->mSharedAudioTrackInfo;
  }
  // mDecodedAudioDuration gets adjusted during ReadOggChain().
  TimeUnit totalDuration = mParent->mDecodedAudioDuration;
  if (eos) {
    // We've encountered an end of bitstream packet; check for a chained
    // bitstream following this one.
    // This will also update mSharedAudioTrackInfo.
    mParent->ReadOggChain(data->GetEndTime());
  }
  data->mOffset = mParent->Resource(mType)->Tell();
  // We adjust the start time of the sample to account for the potential ogg
  // chaining.
  data->mTime += totalDuration;
  if (!data->mTime.IsValid()) {
    return nullptr;
  }

  return data;
}

RefPtr<OggTrackDemuxer::SamplesPromise> OggTrackDemuxer::GetSamples(
    int32_t aNumSamples) {
  RefPtr<SamplesHolder> samples = new SamplesHolder;
  if (!aNumSamples) {
    return SamplesPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_DEMUXER_ERR,
                                           __func__);
  }

  while (aNumSamples) {
    RefPtr<MediaRawData> sample(NextSample());
    if (!sample) {
      break;
    }
    if (!sample->HasValidTime()) {
      return SamplesPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_DEMUXER_ERR,
                                             __func__);
    }
    samples->AppendSample(sample);
    aNumSamples--;
  }

  if (samples->GetSamples().IsEmpty()) {
    return SamplesPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_END_OF_STREAM,
                                           __func__);
  } else {
    return SamplesPromise::CreateAndResolve(samples, __func__);
  }
}

void OggTrackDemuxer::Reset() {
  mParent->Reset(mType);
  mQueuedSample = nullptr;
}

RefPtr<OggTrackDemuxer::SkipAccessPointPromise>
OggTrackDemuxer::SkipToNextRandomAccessPoint(const TimeUnit& aTimeThreshold) {
  uint32_t parsed = 0;
  bool found = false;
  RefPtr<MediaRawData> sample;

  OGG_DEBUG("TimeThreshold: %f", aTimeThreshold.ToSeconds());
  while (!found && (sample = NextSample())) {
    parsed++;
    if (sample->mKeyframe && sample->mTime >= aTimeThreshold) {
      found = true;
      mQueuedSample = sample;
    }
  }
  if (found) {
    OGG_DEBUG("next sample: %f (parsed: %d)", sample->mTime.ToSeconds(),
              parsed);
    return SkipAccessPointPromise::CreateAndResolve(parsed, __func__);
  } else {
    SkipFailureHolder failure(NS_ERROR_DOM_MEDIA_END_OF_STREAM, parsed);
    return SkipAccessPointPromise::CreateAndReject(std::move(failure),
                                                   __func__);
  }
}

TimeIntervals OggTrackDemuxer::GetBuffered() {
  return mParent->GetBuffered(mType);
}

void OggTrackDemuxer::BreakCycles() { mParent = nullptr; }

// Returns an ogg page's checksum.
tainted_opaque_ogg<ogg_uint32_t> OggDemuxer::GetPageChecksum(
    tainted_opaque_ogg<ogg_page*> aPage) {
  tainted_ogg<ogg_page*> page = rlbox::from_opaque(aPage);

  const char hint_reason[] =
      "Early bail out of checksum. Even if this is wrong, the renderer's "
      "security is not compromised.";
  if (page == nullptr ||
      (page->header == nullptr).unverified_safe_because(hint_reason) ||
      (page->header_len < 25).unverified_safe_because(hint_reason)) {
    tainted_ogg<ogg_uint32_t> ret = 0;
    return ret.to_opaque();
  }

  const int CHECKSUM_BYTES_LENGTH = 4;
  const unsigned char* p =
      (page->header + 22u)
          .copy_and_verify_buffer_address(
              [](uintptr_t val) {
                return reinterpret_cast<const unsigned char*>(val);
              },
              CHECKSUM_BYTES_LENGTH);
  uint32_t c =
      static_cast<uint32_t>(p[0] + (p[1] << 8) + (p[2] << 16) + (p[3] << 24));
  tainted_ogg<uint32_t> ret = c;
  return ret.to_opaque();
}

int64_t OggDemuxer::RangeStartTime(TrackInfo::TrackType aType,
                                   int64_t aOffset) {
  int64_t position = Resource(aType)->Tell();
  nsresult res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, aOffset);
  NS_ENSURE_SUCCESS(res, 0);
  int64_t startTime = 0;
  FindStartTime(aType, startTime);
  res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, position);
  NS_ENSURE_SUCCESS(res, -1);
  return startTime;
}

struct nsDemuxerAutoOggSyncState {
  explicit nsDemuxerAutoOggSyncState(rlbox_sandbox_ogg& aSandbox)
      : mSandbox(aSandbox) {
    mState = mSandbox.malloc_in_sandbox<ogg_sync_state>();
    MOZ_RELEASE_ASSERT(mState != nullptr);
    sandbox_invoke(mSandbox, ogg_sync_init, mState);
  }
  ~nsDemuxerAutoOggSyncState() {
    sandbox_invoke(mSandbox, ogg_sync_clear, mState);
    mSandbox.free_in_sandbox(mState);
  }
  rlbox_sandbox_ogg& mSandbox;
  tainted_ogg<ogg_sync_state*> mState;
};

int64_t OggDemuxer::RangeEndTime(TrackInfo::TrackType aType,
                                 int64_t aEndOffset) {
  int64_t position = Resource(aType)->Tell();
  int64_t endTime = RangeEndTime(aType, 0, aEndOffset, false);
  nsresult res =
      Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, position);
  NS_ENSURE_SUCCESS(res, -1);
  return endTime;
}

int64_t OggDemuxer::RangeEndTime(TrackInfo::TrackType aType,
                                 int64_t aStartOffset, int64_t aEndOffset,
                                 bool aCachedDataOnly) {
  nsDemuxerAutoOggSyncState sync(*mSandbox);

  // We need to find the last page which ends before aEndOffset that
  // has a granulepos that we can convert to a timestamp. We do this by
  // backing off from aEndOffset until we encounter a page on which we can
  // interpret the granulepos. If while backing off we encounter a page which
  // we've previously encountered before, we'll either backoff again if we
  // haven't found an end time yet, or return the last end time found.
  const int step = 5000;
  const int maxOggPageSize = 65306;
  int64_t readStartOffset = aEndOffset;
  int64_t readLimitOffset = aEndOffset;
  int64_t readHead = aEndOffset;
  int64_t endTime = -1;
  uint32_t checksumAfterSeek = 0;
  uint32_t prevChecksumAfterSeek = 0;
  bool mustBackOff = false;
  tainted_ogg<ogg_page*> page = mSandbox->malloc_in_sandbox<ogg_page>();
  if (!page) {
    return -1;
  }
  auto clean_page = MakeScopeExit([&] { mSandbox->free_in_sandbox(page); });
  while (true) {
    tainted_ogg<long> seek_ret =
        sandbox_invoke(*mSandbox, ogg_sync_pageseek, sync.mState, page);

    // We aren't really verifying the value of seek_ret below.
    // We are merely ensuring that it won't overflow an integer.
    // However we are assigning the value to ret which is marked tainted, so
    // this is fine.
    bool failedVerify = false;
    CheckedInt<int> checker;
    tainted_ogg<int> ret = CopyAndVerifyOrFail(
        seek_ret, (static_cast<void>(checker = val), checker.isValid()),
        &failedVerify);
    if (failedVerify) {
      return -1;
    }

    if (ret.unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) == 0) {
      // We need more data if we've not encountered a page we've seen before,
      // or we've read to the end of file.
      if (mustBackOff || readHead == aEndOffset || readHead == aStartOffset) {
        if (endTime != -1 || readStartOffset == 0) {
          // We have encountered a page before, or we're at the end of file.
          break;
        }
        mustBackOff = false;
        prevChecksumAfterSeek = checksumAfterSeek;
        checksumAfterSeek = 0;
        sandbox_invoke(*mSandbox, ogg_sync_reset, sync.mState);
        readStartOffset =
            std::max(static_cast<int64_t>(0), readStartOffset - step);
        // There's no point reading more than the maximum size of
        // an Ogg page into data we've previously scanned. Any data
        // between readLimitOffset and aEndOffset must be garbage
        // and we can ignore it thereafter.
        readLimitOffset =
            std::min(readLimitOffset, readStartOffset + maxOggPageSize);
        readHead = std::max(aStartOffset, readStartOffset);
      }

      int64_t limit =
          std::min(static_cast<int64_t>(UINT32_MAX), aEndOffset - readHead);
      limit = std::max(static_cast<int64_t>(0), limit);
      limit = std::min(limit, static_cast<int64_t>(step));
      uint32_t bytesToRead = static_cast<uint32_t>(limit);
      uint32_t bytesRead = 0;
      tainted_ogg<char*> buffer_tainted =
          sandbox_invoke(*mSandbox, ogg_sync_buffer, sync.mState, bytesToRead);
      char* buffer = buffer_tainted.copy_and_verify_buffer_address(
          [](uintptr_t val) { return reinterpret_cast<char*>(val); },
          bytesToRead);
      MOZ_ASSERT(buffer, "Must have buffer");
      nsresult res;
      if (aCachedDataOnly) {
        res = Resource(aType)->GetResource()->ReadFromCache(buffer, readHead,
                                                            bytesToRead);
        NS_ENSURE_SUCCESS(res, -1);
        bytesRead = bytesToRead;
      } else {
        MOZ_ASSERT(readHead < aEndOffset,
                   "resource pos must be before range end");
        res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, readHead);
        NS_ENSURE_SUCCESS(res, -1);
        res = Resource(aType)->Read(buffer, bytesToRead, &bytesRead);
        NS_ENSURE_SUCCESS(res, -1);
      }
      readHead += bytesRead;
      if (readHead > readLimitOffset) {
        mustBackOff = true;
      }

      // Update the synchronisation layer with the number
      // of bytes written to the buffer
      ret = sandbox_invoke(*mSandbox, ogg_sync_wrote, sync.mState, bytesRead);
      bool failedWroteVerify = false;
      int wrote_success =
          CopyAndVerifyOrFail(ret, val == 0 || val == -1, &failedWroteVerify);
      if (failedWroteVerify) {
        return -1;
      }

      if (wrote_success != 0) {
        endTime = -1;
        break;
      }
      continue;
    }

    if (ret.unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) < 0 ||
        sandbox_invoke(*mSandbox, ogg_page_granulepos, page)
                .unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON) < 0) {
      continue;
    }

    tainted_ogg<uint32_t> checksum_tainted =
        rlbox::from_opaque(GetPageChecksum(page.to_opaque()));
    uint32_t checksum = checksum_tainted.unverified_safe_because(
        "checksum is only being used as a hint as part of search for end time. "
        "Incorrect values will not affect the memory safety of the renderer.");
    if (checksumAfterSeek == 0) {
      // This is the first page we've decoded after a backoff/seek. Remember
      // the page checksum. If we backoff further and encounter this page
      // again, we'll know that we won't find a page with an end time after
      // this one, so we'll know to back off again.
      checksumAfterSeek = checksum;
    }
    if (checksum == prevChecksumAfterSeek) {
      // This page has the same checksum as the first page we encountered
      // after the last backoff/seek. Since we've already scanned after this
      // page and failed to find an end time, we may as well backoff again and
      // try to find an end time from an earlier page.
      mustBackOff = true;
      continue;
    }

    int64_t granulepos =
        sandbox_invoke(*mSandbox, ogg_page_granulepos, page)
            .unverified_safe_because(
                "If this is incorrect it may lead to incorrect seeking "
                "behavior in the stream, however will not affect the memory "
                "safety of the Firefox renderer.");
    uint32_t serial = static_cast<uint32_t>(
        sandbox_invoke(*mSandbox, ogg_page_serialno, page)
            .unverified_safe_because(RLBOX_OGG_PAGE_SERIAL_REASON));

    OggCodecState* codecState = nullptr;
    codecState = mCodecStore.Get(serial);
    if (!codecState) {
      // This page is from a bitstream which we haven't encountered yet.
      // It's probably from a new "link" in a "chained" ogg. Don't
      // bother even trying to find a duration...
      SetChained();
      endTime = -1;
      break;
    }

    int64_t t = codecState->Time(granulepos);
    if (t != -1) {
      endTime = t;
    }
  }

  return endTime;
}

nsresult OggDemuxer::GetSeekRanges(TrackInfo::TrackType aType,
                                   nsTArray<SeekRange>& aRanges) {
  AutoPinned<MediaResource> resource(Resource(aType)->GetResource());
  MediaByteRangeSet cached;
  nsresult res = resource->GetCachedRanges(cached);
  NS_ENSURE_SUCCESS(res, res);

  for (uint32_t index = 0; index < cached.Length(); index++) {
    auto& range = cached[index];
    int64_t startTime = -1;
    int64_t endTime = -1;
    if (NS_FAILED(Reset(aType))) {
      return NS_ERROR_FAILURE;
    }
    int64_t startOffset = range.mStart;
    int64_t endOffset = range.mEnd;
    startTime = RangeStartTime(aType, startOffset);
    if (startTime != -1 && ((endTime = RangeEndTime(aType, endOffset)) != -1)) {
      NS_WARNING_ASSERTION(startTime < endTime,
                           "Start time must be before end time");
      aRanges.AppendElement(
          SeekRange(startOffset, endOffset, startTime, endTime));
    }
  }
  if (NS_FAILED(Reset(aType))) {
    return NS_ERROR_FAILURE;
  }
  return NS_OK;
}

OggDemuxer::SeekRange OggDemuxer::SelectSeekRange(
    TrackInfo::TrackType aType, const nsTArray<SeekRange>& ranges,
    int64_t aTarget, int64_t aStartTime, int64_t aEndTime, bool aExact) {
  int64_t so = 0;
  int64_t eo = Resource(aType)->GetLength();
  int64_t st = aStartTime;
  int64_t et = aEndTime;
  for (uint32_t i = 0; i < ranges.Length(); i++) {
    const SeekRange& r = ranges[i];
    if (r.mTimeStart < aTarget) {
      so = r.mOffsetStart;
      st = r.mTimeStart;
    }
    if (r.mTimeEnd >= aTarget && r.mTimeEnd < et) {
      eo = r.mOffsetEnd;
      et = r.mTimeEnd;
    }

    if (r.mTimeStart < aTarget && aTarget <= r.mTimeEnd) {
      // Target lies exactly in this range.
      return ranges[i];
    }
  }
  if (aExact || eo == -1) {
    return SeekRange();
  }
  return SeekRange(so, eo, st, et);
}

nsresult OggDemuxer::SeekInBufferedRange(TrackInfo::TrackType aType,
                                         int64_t aTarget,
                                         int64_t aAdjustedTarget,
                                         int64_t aStartTime, int64_t aEndTime,
                                         const nsTArray<SeekRange>& aRanges,
                                         const SeekRange& aRange) {
  OGG_DEBUG("Seeking in buffered data to %" PRId64 " using bisection search",
            aTarget);
  if (aType == TrackInfo::kVideoTrack || aAdjustedTarget >= aTarget) {
    // We know the exact byte range in which the target must lie. It must
    // be buffered in the media cache. Seek there.
    nsresult res = SeekBisection(aType, aTarget, aRange, 0);
    if (NS_FAILED(res) || aType != TrackInfo::kVideoTrack) {
      return res;
    }

    // We have an active Theora bitstream. Peek the next Theora frame, and
    // extract its keyframe's time.
    DemuxUntilPacketAvailable(aType, mTheoraState);
    ogg_packet* packet = mTheoraState->PacketPeek();
    if (packet && !mTheoraState->IsKeyframe(packet)) {
      // First post-seek frame isn't a keyframe, seek back to previous keyframe,
      // otherwise we'll get visual artifacts.
      MOZ_ASSERT(packet->granulepos != -1, "Must have a granulepos");
      int shift = mTheoraState->KeyFrameGranuleJobs();
      int64_t keyframeGranulepos = (packet->granulepos >> shift) << shift;
      int64_t keyframeTime = mTheoraState->StartTime(keyframeGranulepos);
      SEEK_LOG(LogLevel::Debug,
               ("Keyframe for %lld is at %lld, seeking back to it", frameTime,
                keyframeTime));
      aAdjustedTarget = std::min(aAdjustedTarget, keyframeTime);
    }
  }

  nsresult res = NS_OK;
  if (aAdjustedTarget < aTarget) {
    SeekRange k = SelectSeekRange(aType, aRanges, aAdjustedTarget, aStartTime,
                                  aEndTime, false);
    res = SeekBisection(aType, aAdjustedTarget, k, OGG_SEEK_FUZZ_USECS);
  }
  return res;
}

nsresult OggDemuxer::SeekInUnbuffered(TrackInfo::TrackType aType,
                                      int64_t aTarget, int64_t aStartTime,
                                      int64_t aEndTime,
                                      const nsTArray<SeekRange>& aRanges) {
  OGG_DEBUG("Seeking in unbuffered data to %" PRId64 " using bisection search",
            aTarget);

  // If we've got an active Theora bitstream, determine the maximum possible
  // time in usecs which a keyframe could be before a given interframe. We
  // subtract this from our seek target, seek to the new target, and then
  // will decode forward to the original seek target. We should encounter a
  // keyframe in that interval. This prevents us from needing to run two
  // bisections; one for the seek target frame, and another to find its
  // keyframe. It's usually faster to just download this extra data, rather
  // tham perform two bisections to find the seek target's keyframe. We
  // don't do this offsetting when seeking in a buffered range,
  // as the extra decoding causes a noticeable speed hit when all the data
  // is buffered (compared to just doing a bisection to exactly find the
  // keyframe).
  int64_t keyframeOffsetMs = 0;
  if (aType == TrackInfo::kVideoTrack && mTheoraState) {
    keyframeOffsetMs = mTheoraState->MaxKeyframeOffset();
  }
  // Add in the Opus pre-roll if necessary, as well.
  if (aType == TrackInfo::kAudioTrack && mOpusState) {
    keyframeOffsetMs =
        std::max(keyframeOffsetMs, OGG_SEEK_OPUS_PREROLL.ToMilliseconds());
  }
  int64_t seekTarget = std::max(aStartTime, aTarget - keyframeOffsetMs);
  // Minimize the bisection search space using the known timestamps from the
  // buffered ranges.
  SeekRange k =
      SelectSeekRange(aType, aRanges, seekTarget, aStartTime, aEndTime, false);
  return SeekBisection(aType, seekTarget, k, OGG_SEEK_FUZZ_USECS);
}

nsresult OggDemuxer::SeekBisection(TrackInfo::TrackType aType, int64_t aTarget,
                                   const SeekRange& aRange, uint32_t aFuzz) {
  nsresult res;

  if (aTarget <= aRange.mTimeStart) {
    if (NS_FAILED(Reset(aType))) {
      return NS_ERROR_FAILURE;
    }
    res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, 0);
    NS_ENSURE_SUCCESS(res, res);
    return NS_OK;
  }

  // Bisection search, find start offset of last page with end time less than
  // the seek target.
  ogg_int64_t startOffset = aRange.mOffsetStart;
  ogg_int64_t startTime = aRange.mTimeStart;
  ogg_int64_t startLength = 0;  // Length of the page at startOffset.
  ogg_int64_t endOffset = aRange.mOffsetEnd;
  ogg_int64_t endTime = aRange.mTimeEnd;

  ogg_int64_t seekTarget = aTarget;
  int64_t seekLowerBound = std::max(static_cast<int64_t>(0), aTarget - aFuzz);
  int hops = 0;
  DebugOnly<ogg_int64_t> previousGuess = -1;
  int backsteps = 0;
  const int maxBackStep = 10;
  MOZ_ASSERT(
      static_cast<uint64_t>(PAGE_STEP) * pow(2.0, maxBackStep) < INT32_MAX,
      "Backstep calculation must not overflow");

  // Seek via bisection search. Loop until we find the offset where the page
  // before the offset is before the seek target, and the page after the offset
  // is after the seek target.
  tainted_ogg<ogg_page*> page = mSandbox->malloc_in_sandbox<ogg_page>();
  if (!page) {
    return NS_ERROR_OUT_OF_MEMORY;
  }
  auto clean_page = MakeScopeExit([&] { mSandbox->free_in_sandbox(page); });
  while (true) {
    ogg_int64_t duration = 0;
    double target = 0;
    ogg_int64_t interval = 0;
    ogg_int64_t guess = 0;
    int skippedBytes = 0;
    ogg_int64_t pageOffset = 0;
    ogg_int64_t pageLength = 0;
    ogg_int64_t granuleTime = -1;
    bool mustBackoff = false;

    // Guess where we should bisect to, based on the bit rate and the time
    // remaining in the interval. Loop until we can determine the time at
    // the guess offset.
    while (true) {
      // Discard any previously buffered packets/pages.
      if (NS_FAILED(Reset(aType))) {
        return NS_ERROR_FAILURE;
      }

      interval = endOffset - startOffset - startLength;
      if (interval == 0) {
        // Our interval is empty, we've found the optimal seek point, as the
        // page at the start offset is before the seek target, and the page
        // at the end offset is after the seek target.
        SEEK_LOG(LogLevel::Debug,
                 ("Interval narrowed, terminating bisection."));
        break;
      }

      // Guess bisection point.
      duration = endTime - startTime;
      target = (double)(seekTarget - startTime) / (double)duration;
      guess = startOffset + startLength +
              static_cast<ogg_int64_t>((double)interval * target);
      guess = std::min(guess, endOffset - PAGE_STEP);
      if (mustBackoff) {
        // We previously failed to determine the time at the guess offset,
        // probably because we ran out of data to decode. This usually happens
        // when we guess very close to the end offset. So reduce the guess
        // offset using an exponential backoff until we determine the time.
        SEEK_LOG(
            LogLevel::Debug,
            ("Backing off %d bytes, backsteps=%d",
             static_cast<int32_t>(PAGE_STEP * pow(2.0, backsteps)), backsteps));
        guess -= PAGE_STEP * static_cast<ogg_int64_t>(pow(2.0, backsteps));

        if (guess <= startOffset) {
          // We've tried to backoff to before the start offset of our seek
          // range. This means we couldn't find a seek termination position
          // near the end of the seek range, so just set the seek termination
          // condition, and break out of the bisection loop. We'll begin
          // decoding from the start of the seek range.
          interval = 0;
          break;
        }

        backsteps = std::min(backsteps + 1, maxBackStep);
        // We reset mustBackoff. If we still need to backoff further, it will
        // be set to true again.
        mustBackoff = false;
      } else {
        backsteps = 0;
      }
      guess = std::max(guess, startOffset + startLength);

      SEEK_LOG(LogLevel::Debug,
               ("Seek loop start[o=%lld..%lld t=%lld] "
                "end[o=%lld t=%lld] "
                "interval=%lld target=%lf guess=%lld",
                startOffset, (startOffset + startLength), startTime, endOffset,
                endTime, interval, target, guess));

      MOZ_ASSERT(guess >= startOffset + startLength,
                 "Guess must be after range start");
      MOZ_ASSERT(guess < endOffset, "Guess must be before range end");
      MOZ_ASSERT(guess != previousGuess,
                 "Guess should be different to previous");
      previousGuess = guess;

      hops++;

      // Locate the next page after our seek guess, and then figure out the
      // granule time of the audio and video bitstreams there. We can then
      // make a bisection decision based on our location in the media.
      PageSyncResult pageSyncResult =
          PageSync(mSandbox.get(), Resource(aType), OggSyncState(aType), false,
                   guess, endOffset, page, skippedBytes);
      NS_ENSURE_TRUE(pageSyncResult != PAGE_SYNC_ERROR, NS_ERROR_FAILURE);

      if (pageSyncResult == PAGE_SYNC_END_OF_RANGE) {
        // Our guess was too close to the end, we've ended up reading the end
        // page. Backoff exponentially from the end point, in case the last
        // page/frame/sample is huge.
        mustBackoff = true;
        SEEK_LOG(LogLevel::Debug, ("Hit the end of range, backing off"));
        continue;
      }

      // We've located a page of length |ret| at |guess + skippedBytes|.
      // Remember where the page is located.
      pageOffset = guess + skippedBytes;

      bool failedPageLenVerify = false;
      // Page length should be under 64Kb according to
      // https://xiph.org/ogg/doc/libogg/ogg_page.html
      pageLength = CopyAndVerifyOrFail(page->header_len + page->body_len,
                                       val <= 64 * 1024, &failedPageLenVerify);
      if (failedPageLenVerify) {
        return NS_ERROR_FAILURE;
      }

      // Read pages until we can determine the granule time of the audio and
      // video bitstream.
      ogg_int64_t audioTime = -1;
      ogg_int64_t videoTime = -1;
      do {
        // Add the page to its codec state, determine its granule time.
        uint32_t serial = static_cast<uint32_t>(
            sandbox_invoke(*mSandbox, ogg_page_serialno, page)
                .unverified_safe_because(RLBOX_OGG_PAGE_SERIAL_REASON));
        OggCodecState* codecState = mCodecStore.Get(serial);
        if (codecState && GetCodecStateType(codecState) == aType) {
          if (codecState->mActive) {
            int ret =
                sandbox_invoke(*mSandbox, ogg_stream_pagein, codecState->mState,
                               page)
                    .unverified_safe_because(RLBOX_OGG_STATE_ASSERT_REASON);
            NS_ENSURE_TRUE(ret == 0, NS_ERROR_FAILURE);
          }

          ogg_int64_t granulepos =
              sandbox_invoke(*mSandbox, ogg_page_granulepos, page)
                  .unverified_safe_because(
                      "If this is incorrect it may lead to incorrect seeking "
                      "behavior in the stream, however will not affect the "
                      "memory safety of the Firefox renderer.");

          if (aType == TrackInfo::kAudioTrack && granulepos > 0 &&
              audioTime == -1) {
            if (mVorbisState && serial == mVorbisState->mSerial) {
              audioTime = mVorbisState->Time(granulepos);
            } else if (mOpusState && serial == mOpusState->mSerial) {
              audioTime = mOpusState->Time(granulepos);
            } else if (mFlacState && serial == mFlacState->mSerial) {
              audioTime = mFlacState->Time(granulepos);
            }
          }

          if (aType == TrackInfo::kVideoTrack && granulepos > 0 &&
              serial == mTheoraState->mSerial && videoTime == -1) {
            videoTime = mTheoraState->Time(granulepos);
          }

          if (pageOffset + pageLength >= endOffset) {
            // Hit end of readable data.
            break;
          }
        }
        if (!ReadOggPage(aType, page.to_opaque())) {
          break;
        }

      } while ((aType == TrackInfo::kAudioTrack && audioTime == -1) ||
               (aType == TrackInfo::kVideoTrack && videoTime == -1));

      if ((aType == TrackInfo::kAudioTrack && audioTime == -1) ||
          (aType == TrackInfo::kVideoTrack && videoTime == -1)) {
        // We don't have timestamps for all active tracks...
        if (pageOffset == startOffset + startLength &&
            pageOffset + pageLength >= endOffset) {
          // We read the entire interval without finding timestamps for all
          // active tracks. We know the interval start offset is before the seek
          // target, and the interval end is after the seek target, and we can't
          // terminate inside the interval, so we terminate the seek at the
          // start of the interval.
          interval = 0;
          break;
        }

        // We should backoff; cause the guess to back off from the end, so
        // that we've got more room to capture.
        mustBackoff = true;
        continue;
      }

      // We've found appropriate time stamps here. Proceed to bisect
      // the search space.
      granuleTime = aType == TrackInfo::kAudioTrack ? audioTime : videoTime;
      MOZ_ASSERT(granuleTime > 0, "Must get a granuletime");
      break;
    }  // End of "until we determine time at guess offset" loop.

    if (interval == 0) {
      // Seek termination condition; we've found the page boundary of the
      // last page before the target, and the first page after the target.
      SEEK_LOG(LogLevel::Debug,
               ("Terminating seek at offset=%lld", startOffset));
      MOZ_ASSERT(startTime < aTarget,
                 "Start time must always be less than target");
      res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, startOffset);
      NS_ENSURE_SUCCESS(res, res);
      if (NS_FAILED(Reset(aType))) {
        return NS_ERROR_FAILURE;
      }
      break;
    }

    SEEK_LOG(LogLevel::Debug,
             ("Time at offset %lld is %lld", guess, granuleTime));
    if (granuleTime < seekTarget && granuleTime > seekLowerBound) {
      // We're within the fuzzy region in which we want to terminate the search.
      res = Resource(aType)->Seek(nsISeekableStream::NS_SEEK_SET, pageOffset);
      NS_ENSURE_SUCCESS(res, res);
      if (NS_FAILED(Reset(aType))) {
        return NS_ERROR_FAILURE;
      }
      SEEK_LOG(LogLevel::Debug,
               ("Terminating seek at offset=%lld", pageOffset));
      break;
    }

    if (granuleTime >= seekTarget) {
      // We've landed after the seek target.
      MOZ_ASSERT(pageOffset < endOffset, "offset_end must decrease");
      endOffset = pageOffset;
      endTime = granuleTime;
    } else if (granuleTime < seekTarget) {
      // Landed before seek target.
      MOZ_ASSERT(pageOffset >= startOffset + startLength,
                 "Bisection point should be at or after end of first page in "
                 "interval");
      startOffset = pageOffset;
      startLength = pageLength;
      startTime = granuleTime;
    }
    MOZ_ASSERT(startTime <= seekTarget, "Must be before seek target");
    MOZ_ASSERT(endTime >= seekTarget, "End must be after seek target");
  }

  (void)hops;
  SEEK_LOG(LogLevel::Debug, ("Seek complete in %d bisections.", hops));

  return NS_OK;
}

#undef OGG_DEBUG
#undef SEEK_LOG
#undef CopyAndVerifyOrFail
}  // namespace mozilla