C++ IOCallback::setFilePointer方法代码示例

filepos_t EbmlString::ReadData(IOCallback & input, ScopeMode ReadFully)
{
	if (ReadFully != SCOPE_NO_DATA)
	{
		if (GetSize() == 0) {
			Value = "";
			SetValueIsSet();
		} else {
			char *Buffer = new char[GetSize() + 1];
			if (Buffer == NULL) {
				// unable to store the data, skip it
				input.setFilePointer(GetSize(), seek_current);
			} else {
				input.readFully(Buffer, GetSize());
				if (Buffer[GetSize()-1] != '\0') {
					Buffer[GetSize()] = '\0';
				}
				Value = Buffer;
				delete [] Buffer;
				SetValueIsSet();
			}
		}
	}

	return GetSize();
}

uint64 EbmlString::ReadData(IOCallback & input, ScopeMode ReadFully)
{
	if (ReadFully != SCOPE_NO_DATA)
	{
		if (Size == 0) {
			Value = "";
			bValueIsSet = true;
		} else {
			char *Buffer = new char[Size + 1];
			if (Buffer == NULL) {
				// unable to store the data, skip it
				input.setFilePointer(Size, seek_current);
			} else {
				input.readFully(Buffer, Size);
				if (Buffer[Size-1] != '\0') {
					Buffer[Size] = '\0';
				}
				Value = Buffer;
				delete [] Buffer;
				bValueIsSet = true;
			}
		}
	}

	return Size;
}

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();
}

filepos_t EbmlCrc32::ReadData(IOCallback & input, ScopeMode ReadFully)
{
	if (ReadFully != SCOPE_NO_DATA)
	{
		binary *Buffer = new binary[GetSize()];
		if (Buffer == NULL) {
			// impossible to read, skip it
			input.setFilePointer(GetSize(), seek_current);
		} else {
			input.readFully(Buffer, GetSize());

			memcpy((void *)&m_crc_final, Buffer, 4);
			delete [] Buffer;
			SetValueIsSet();
		}
	}

	return GetSize();
}

/*!
	\todo this code is very suspicious !
*/
filepos_t EbmlMaster::ReadData(IOCallback & input, ScopeMode ReadFully)
{
	input.setFilePointer(GetSize(), seek_current);
	return GetSize();
}