Method RollbackFilePointer

source/TextIO.h:140–153

	virtual __int64 _Length() const = 0;
	
	void RollbackFilePointer()
	{
		if (mPos) // Buffered reading was used.
		{
			// Discard the buffer and rollback the file pointer.
			ptrdiff_t offset = (mPos - mBuffer) - mLength; // should be a value <= 0
			_Seek(offset, SEEK_CUR);
			// Callers expect the buffer to be cleared (e.g. to be reused for buffered writing), so if
			// _Seek fails, the data is simply discarded.  This can probably only happen for non-seeking
			// devices such as pipes or the console, which won't typically be both read from and written to:
			mPos = NULL;
			mLength = 0;
		}
	}
	
	void FlushWriteBuffer()
	{