C++ CanSeek函数代码示例

void Buffer::SetPos(int value) {
    if ((value >= fileLen) && (stream != NULL) && !CanSeek()) {
        // Wanted position is after buffer and the stream
        // is not seek-able e.g. network or console,
        // thus we have to read the stream manually till
        // the wanted position is in sight.
        while ((value >= fileLen) && (ReadNextStreamChunk() > 0));
    }

    if ((value < 0) || (value > fileLen)) {
        wprintf(L"--- buffer out of bounds access, position: %d\n", value);
        MX_DEBUG_BREAK;
        exit(1);
    }

    if ((value >= bufStart) && (value < (bufStart + bufLen))) { // already in buffer
        bufPos = value - bufStart;
    } else if (stream != NULL) { // must be swapped in
        fseek(stream, value, SEEK_SET);
        bufLen = fread(buf, sizeof(unsigned char), bufCapacity, stream);
        bufStart = value;
        bufPos = 0;
    } else {
        bufPos = fileLen - bufStart; // make Pos return fileLen
    }
}

void MediaPlayer2Player::currentSourceChanged() const
{
    QVariantMap properties;
    properties["Metadata"] = Metadata();
    properties["CanSeek"] = CanSeek();
    Mpris2::signalPropertiesChange(this, properties);
}

void PAPlayer::Seek(bool bPlus, bool bLargeStep, bool bChapterOverride)
{
  if (!CanSeek()) return;

  __int64 seek;
  if (g_advancedSettings.m_musicUseTimeSeeking && GetTotalTime() > 2 * g_advancedSettings.m_musicTimeSeekForwardBig)
  {
    if (bLargeStep)
      seek = bPlus ? g_advancedSettings.m_musicTimeSeekForwardBig : g_advancedSettings.m_musicTimeSeekBackwardBig;
    else
      seek = bPlus ? g_advancedSettings.m_musicTimeSeekForward : g_advancedSettings.m_musicTimeSeekBackward;
    seek *= 1000;
    seek += GetTime();
  }
  else
  {
    float percent;
    if (bLargeStep)
      percent = bPlus ? (float)g_advancedSettings.m_musicPercentSeekForwardBig : (float)g_advancedSettings.m_musicPercentSeekBackwardBig;
    else
      percent = bPlus ? (float)g_advancedSettings.m_musicPercentSeekForward : (float)g_advancedSettings.m_musicPercentSeekBackward;
    seek = (__int64)(GetTotalTime64() * (GetPercentage() + percent) / 100);
  }

  SeekTime(seek);
}

void Mpris::updateStatus()
{
    QVariantMap map;

    if (MPDStatus::self()->repeat()!=status.repeat) {
        map.insert("LoopStatus", LoopStatus());
    }
    if (MPDStatus::self()->random()!=status.random) {
        map.insert("Shuffle", Shuffle());
    }
    if (MPDStatus::self()->volume()!=status.volume) {
        map.insert("Volume", Volume());
    }
    if (MPDStatus::self()->playlistLength()!=status.playlistLength) {
        map.insert("CanGoNext", CanGoNext());
        map.insert("CanGoPrevious", CanGoPrevious());
    }
    if (MPDStatus::self()->state()!=status.state) {
        map.insert("PlaybackStatus", PlaybackStatus());
        map.insert("CanPlay", CanPlay());
        map.insert("CanPause", CanPause());
        map.insert("CanSeek", CanSeek());
    }
    if (MPDStatus::self()->timeElapsed()!=status.timeElapsed) {
        map.insert("Position", convertTime(MPDStatus::self()->timeElapsed()));
    }
    if (!map.isEmpty() || MPDStatus::self()->songId()!=status.songId) {
        if (!map.contains("Position")) {
            map.insert("Position", convertTime(MPDStatus::self()->timeElapsed()));
        }
        map.insert("Metadata", Metadata());
        signalUpdate(map);
    }
    status=MPDStatus::self()->getValues();
}

void MediaPlayer2Player::currentSourceChanged() const
{
    QVariantMap properties;
    properties["Metadata"] = Metadata();
    properties["CanSeek"] = CanSeek();
    properties["PlaybackStatus"] = PlaybackStatus();
    signalPropertiesChange(properties);
}

void PAPlayer::SeekTime(__int64 iTime /*=0*/)
{
  if (!CanSeek()) return;
  if (m_currentFile->m_lStartOffset)
    iTime += m_currentFile->m_lStartOffset * 1000 / 75;
  m_SeekTime = iTime;
  CLog::Log(LOGDEBUG, "PAPlayer::Seeking to time %f", 0.001f * m_SeekTime);
}

void PAPlayer::SeekTime(__int64 iTime /*=0*/)
{
  if (!CanSeek()) return;
  int seekOffset = (int)(iTime - GetTime());
  if (m_currentFile->m_lStartOffset)
    iTime += m_currentFile->m_lStartOffset * 1000 / 75;
  m_SeekTime = iTime;
  m_callback.OnPlayBackSeek((int)m_SeekTime, seekOffset);
  CLog::Log(LOGDEBUG, "PAPlayer::Seeking to time %f", 0.001f * m_SeekTime);
}

int Buffer::Read() {
	if (bufPos < bufLen) {
		return buf[bufPos++];
	} else if (GetPos() < fileLen) {
		SetPos(GetPos()); // shift buffer start to Pos
		return buf[bufPos++];
	} else if ((stream != NULL) && !CanSeek() && (ReadNextStreamChunk() > 0)) {
		return buf[bufPos++];
	} else {
		return EoF;
	}
}

Buffer::Buffer(FILE* s, bool isUserStream) {
// ensure binary read on windows
#if _MSC_VER >= 1300
	_setmode(_fileno(s), _O_BINARY);
#endif
	stream = s; this->isUserStream = isUserStream;
	if (CanSeek()) {
		fseek(s, 0, SEEK_END);
		fileLen = ftell(s);
		fseek(s, 0, SEEK_SET);
		bufLen = (fileLen < MAX_BUFFER_LENGTH) ? fileLen : MAX_BUFFER_LENGTH;
		bufStart = INT_MAX; // nothing in the buffer so far
	} else {
		fileLen = bufLen = bufStart = 0;
	}
	bufCapacity = (bufLen>0) ? bufLen : MIN_BUFFER_LENGTH;
	buf = new unsigned char[bufCapacity];	
	if (fileLen > 0) SetPos(0);          // setup  buffer to position 0 (start)
	else bufPos = 0; // index 0 is already after the file, thus Pos = 0 is invalid
	if (bufLen == fileLen && CanSeek()) Close();
}

int64_t CInputStreamPVRBase::Seek(int64_t offset, int whence)
{
  if (whence == SEEK_POSSIBLE)
    return CanSeek() ? 1 : 0;

  int64_t ret = SeekPVRStream(offset, whence);

  // if we succeed, we are not eof anymore
  if (ret >= 0)
    m_eof = false;

  return ret;
}

void PAPlayer::SeekTime(int64_t iTime /*=0*/)
{
  if (!CanSeek()) return;

  CSharedLock lock(m_streamsLock);
  if (!m_currentStream)
    return;

  int seekOffset = (int)(iTime - GetTimeInternal());

  if (m_playbackSpeed != 1)
    ToFFRW(1);

  m_currentStream->m_seekFrame = (int)((float)m_currentStream->m_sampleRate * ((float)iTime + (float)m_currentStream->m_startOffset) / 1000.0f);
  m_callback.OnPlayBackSeek((int)iTime, seekOffset);
}

void CApplicationPlayer::SetPlaySpeed(int iSpeed, bool bApplicationMuted)
{
  boost::shared_ptr<IPlayer> player = GetInternal();
  if (!player)
    return;

  if (!IsPlayingAudio() && !IsPlayingVideo())
    return ;
  if (m_iPlaySpeed == iSpeed)
    return ;
  if (!CanSeek())
    return;
  if (IsPaused())
  {
    if (
      ((m_iPlaySpeed > 1) && (iSpeed > m_iPlaySpeed)) ||
      ((m_iPlaySpeed < -1) && (iSpeed < m_iPlaySpeed))
    )
    {
      iSpeed = m_iPlaySpeed; // from pause to ff/rw, do previous ff/rw speed
    }
    Pause();
  }
  m_iPlaySpeed = iSpeed;

  ToFFRW(m_iPlaySpeed);

  // if player has volume control, set it.
  if (ControlsVolume())
  {
    if (m_iPlaySpeed == 1)
    { // restore volume
      player->SetVolume(g_application.GetVolume(false));
    }
    else
    { // mute volume
      player->SetVolume(VOLUME_MINIMUM);
    }
    player->SetMute(bApplicationMuted);
  }
}

size_t FileStream::Seek(StreamSeek seek, int pos)
{
    if (!CanSeek())
    {
        return 0;
    }

    int stdclib_seek;
    switch (seek)
    {
    case kSeekBegin:    stdclib_seek = SEEK_SET; break;
    case kSeekCurrent:  stdclib_seek = SEEK_CUR; break;
    case kSeekEnd:      stdclib_seek = SEEK_END; break;
    default:
        // TODO: warning to the log
        return 0;
    }

    fseek(_file, pos, stdclib_seek);
    return GetPosition();
}

void Mpris2::slotCurrentSourceChanged()
{
    EmitPropertyChanged("Metadata", Metadata());
    EmitPropertyChanged("CanSeek", CanSeek());
}