C++ IOCallback::getFilePointer方法代码示例

uint64 EbmlVoid::Overwrite(const EbmlElement & EltToVoid, IOCallback & output, bool ComeBackAfterward, bool bWithDefault)
{
//	EltToVoid.UpdateSize(bWithDefault);
	if (EltToVoid.GetElementPosition() == 0) {
		// this element has never been written
		return 0;
	}
	if (EltToVoid.GetSize() + EltToVoid.HeadSize() <2) {
		// the element can't be written here !
		return 0;
	}

	uint64 CurrentPosition = output.getFilePointer();

	output.setFilePointer(EltToVoid.GetElementPosition());

	// compute the size of the voided data based on the original one
	SetSize(EltToVoid.GetSize() + EltToVoid.HeadSize() - 1); // 1 for the ID
	SetSize(GetSize() - CodedSizeLength(GetSize(), GetSizeLength(), IsFiniteSize()));
	// make sure we handle even the strange cases
	//uint32 A1 = GetSize() + HeadSize();
	//uint32 A2 = EltToVoid.GetSize() + EltToVoid.HeadSize();
	if (GetSize() + HeadSize() != EltToVoid.GetSize() + EltToVoid.HeadSize()) {
		SetSize(GetSize()-1);
		SetSizeLength(CodedSizeLength(GetSize(), GetSizeLength(), IsFiniteSize()) + 1);
	}

	if (GetSize() != 0) {
		RenderHead(output, false, bWithDefault); // the rest of the data is not rewritten
	}

	if (ComeBackAfterward) {
		output.setFilePointer(CurrentPosition);
	}

	return EltToVoid.GetSize() + EltToVoid.HeadSize();
}

uint64 EbmlVoid::ReplaceWith(EbmlElement & EltToReplaceWith, IOCallback & output, bool ComeBackAfterward, bool bWithDefault)
{
	EltToReplaceWith.UpdateSize(bWithDefault);
	if (HeadSize() + GetSize() < EltToReplaceWith.GetSize() + EltToReplaceWith.HeadSize()) {
		// the element can't be written here !
		return INVALID_FILEPOS_T;
	}
	if (HeadSize() + GetSize() - EltToReplaceWith.GetSize() - EltToReplaceWith.HeadSize() == 1) {
		// there is not enough space to put a filling element
		return INVALID_FILEPOS_T;
	}

	uint64 CurrentPosition = output.getFilePointer();

	output.setFilePointer(GetElementPosition());
	EltToReplaceWith.Render(output, bWithDefault);

	if (HeadSize() + GetSize() - EltToReplaceWith.GetSize() - EltToReplaceWith.HeadSize() > 1) {
	  // fill the rest with another void element
	  EbmlVoid aTmp;
	  aTmp.SetSize_(HeadSize() + GetSize() - EltToReplaceWith.GetSize() - EltToReplaceWith.HeadSize() - 1); // 1 is the length of the Void ID
	  int HeadBefore = aTmp.HeadSize();
	  aTmp.SetSize_(aTmp.GetSize() - CodedSizeLength(aTmp.GetSize(), aTmp.GetSizeLength(), aTmp.IsFiniteSize()));
	  int HeadAfter = aTmp.HeadSize();
	  if (HeadBefore != HeadAfter) {
		  aTmp.SetSizeLength(CodedSizeLength(aTmp.GetSize(), aTmp.GetSizeLength(), aTmp.IsFiniteSize()) - (HeadAfter - HeadBefore));
	  }
	  aTmp.RenderHead(output, false, bWithDefault); // the rest of the data is not rewritten
	}

	if (ComeBackAfterward) {
		output.setFilePointer(CurrentPosition);
	}

	return GetSize() + HeadSize();
}

/*!
	\todo better zero copy handling
*/
filepos_t KaxInternalBlock::ReadData(IOCallback & input, ScopeMode ReadFully)
{
	filepos_t Result;

	FirstFrameLocation = input.getFilePointer(); // will be updated accordingly below

	if (ReadFully == SCOPE_ALL_DATA)
	{
		Result = EbmlBinary::ReadData(input, ReadFully);
        binary *cursor = EbmlBinary::GetBuffer();
		uint8 BlockHeadSize = 4;

		// update internal values
		TrackNumber = *cursor++;
		if ((TrackNumber & 0x80) == 0) {
			// there is extra data
			if ((TrackNumber & 0x40) == 0) {
				// We don't support track numbers that large !
				return Result;
			}
			TrackNumber = (TrackNumber & 0x3F) << 8;
			TrackNumber += *cursor++;
			BlockHeadSize++;
		} else {
			TrackNumber &= 0x7F;
		}

		big_int16 b16;
		b16.Eval(cursor);
		LocalTimecode = int16(b16);
		bLocalTimecodeUsed = true;
		cursor += 2;

		if (EbmlId(*this) == EBML_ID(KaxSimpleBlock)) {
			bIsKeyframe = (*cursor & 0x80) != 0;
			bIsDiscardable = (*cursor & 0x01) != 0;
		}
		mInvisible = (*cursor & 0x08) >> 3;
		mLacing = LacingType((*cursor++ & 0x06) >> 1);

		// put all Frames in the list
		if (mLacing == LACING_NONE) {
			FirstFrameLocation += cursor - EbmlBinary::GetBuffer();
			DataBuffer * soloFrame = new DataBuffer(cursor, GetSize() - BlockHeadSize);
			myBuffers.push_back(soloFrame);
			SizeList.resize(1);
			SizeList[0] = GetSize() - BlockHeadSize;
		} else {
			// read the number of frames in the lace
			uint32 LastBufferSize = GetSize() - BlockHeadSize - 1; // 1 for number of frame
			uint8 FrameNum = *cursor++; // number of frames in the lace - 1
			// read the list of frame sizes
			uint8 Index;
			int32 FrameSize;
			uint32 SizeRead;
			uint64 SizeUnknown;

			SizeList.resize(FrameNum + 1);

			switch (mLacing)
			{
			case LACING_XIPH:
				for (Index=0; Index<FrameNum; Index++) {
					// get the size of the frame
					FrameSize = 0;
					do {
						FrameSize += uint8(*cursor);
						LastBufferSize--;
					} while (*cursor++ == 0xFF);
					SizeList[Index] = FrameSize;
					LastBufferSize -= FrameSize;
				}
				SizeList[Index] = LastBufferSize;
				break;
			case LACING_EBML:
				SizeRead = LastBufferSize;
				FrameSize = ReadCodedSizeValue(cursor, SizeRead, SizeUnknown);
				SizeList[0] = FrameSize;
				cursor += SizeRead;
				LastBufferSize -= FrameSize + SizeRead;

				for (Index=1; Index<FrameNum; Index++) {
					// get the size of the frame
					SizeRead = LastBufferSize;
					FrameSize += ReadCodedSizeSignedValue(cursor, SizeRead, SizeUnknown);
					SizeList[Index] = FrameSize;
					cursor += SizeRead;
					LastBufferSize -= FrameSize + SizeRead;
				}
				SizeList[Index] = LastBufferSize;
				break;
			case LACING_FIXED:
				for (Index=0; Index<=FrameNum; Index++) {
					// get the size of the frame
					SizeList[Index] = LastBufferSize / (FrameNum + 1);
				}
				break;
//.........这里部分代码省略.........

/*!
  \todo better zero copy handling
*/
filepos_t KaxInternalBlock::ReadData(IOCallback & input, ScopeMode ReadFully)
{
  filepos_t Result;

  FirstFrameLocation = input.getFilePointer(); // will be updated accordingly below

  SetValueIsSet(false);

  try {
    if (ReadFully == SCOPE_ALL_DATA) {
      Result = EbmlBinary::ReadData(input, ReadFully);
      if (Result != GetSize())
        throw SafeReadIOCallback::EndOfStreamX(GetSize() - Result);

      binary *BufferStart = EbmlBinary::GetBuffer();

      SafeReadIOCallback Mem(*this);
      uint8 BlockHeadSize = 4;

      // update internal values
      TrackNumber = Mem.GetUInt8();
      if ((TrackNumber & 0x80) == 0) {
        // there is extra data
        if ((TrackNumber & 0x40) == 0) {
          // We don't support track numbers that large !
          throw SafeReadIOCallback::EndOfStreamX(0);
        }
        TrackNumber = (TrackNumber & 0x3F) << 8;
        TrackNumber += Mem.GetUInt8();
        BlockHeadSize++;
      } else {
        TrackNumber &= 0x7F;
      }

      LocalTimecode = int16(Mem.GetUInt16BE());
      bLocalTimecodeUsed = true;

      uint8 Flags = Mem.GetUInt8();
      if (EbmlId(*this) == EBML_ID(KaxSimpleBlock)) {
        bIsKeyframe = (Flags & 0x80) != 0;
        bIsDiscardable = (Flags & 0x01) != 0;
      }
      mInvisible = (Flags & 0x08) >> 3;
      mLacing = LacingType((Flags & 0x06) >> 1);

      // put all Frames in the list
      if (mLacing == LACING_NONE) {
        FirstFrameLocation += Mem.GetPosition();
        DataBuffer * soloFrame = new DataBuffer(BufferStart + Mem.GetPosition(), GetSize() - BlockHeadSize);
        myBuffers.push_back(soloFrame);
        SizeList.resize(1);
        SizeList[0] = GetSize() - BlockHeadSize;
      } else {
        // read the number of frames in the lace
        uint32 LastBufferSize = GetSize() - BlockHeadSize - 1; // 1 for number of frame
        uint8 FrameNum = Mem.GetUInt8(); // number of frames in the lace - 1
        // read the list of frame sizes
        uint8 Index;
        int32 FrameSize;
        uint32 SizeRead;
        uint64 SizeUnknown;

        SizeList.resize(FrameNum + 1);

        switch (mLacing) {
          case LACING_XIPH:
            for (Index=0; Index<FrameNum; Index++) {
              // get the size of the frame
              FrameSize = 0;
              uint8 Value;
              do {
                Value = Mem.GetUInt8();
                FrameSize += Value;
                LastBufferSize--;
              } while (Value == 0xFF);
              SizeList[Index] = FrameSize;
              LastBufferSize -= FrameSize;
            }
            SizeList[Index] = LastBufferSize;
            break;
          case LACING_EBML:
            SizeRead = LastBufferSize;
            FrameSize = ReadCodedSizeValue(BufferStart + Mem.GetPosition(), SizeRead, SizeUnknown);
            SizeList[0] = FrameSize;
            Mem.Skip(SizeRead);
            LastBufferSize -= FrameSize + SizeRead;

            for (Index=1; Index<FrameNum; Index++) {
              // get the size of the frame
              SizeRead = LastBufferSize;
              FrameSize += ReadCodedSizeSignedValue(BufferStart + Mem.GetPosition(), SizeRead, SizeUnknown);
              SizeList[Index] = FrameSize;
              Mem.Skip(SizeRead);
              LastBufferSize -= FrameSize + SizeRead;
            }
            if (Index <= FrameNum) // Safety check if FrameNum == 0
              SizeList[Index] = LastBufferSize;
//.........这里部分代码省略.........