Method Write

libcppcryptfs/file/cryptfile.cpp:367–611

BOOL CryptFileForward::Write(const unsigned char *buf, DWORD buflen, LPDWORD pNwritten, LONGLONG offset, BOOL bWriteToEndOfFile, BOOL bPagingIo)
{
		
	if (m_real_file_size == (long long)-1)
		return FALSE;

	if (!pNwritten || !buf)
		return FALSE;

	*pNwritten = 0;

	if (buflen < 1)
		return TRUE;

	BOOL bRet = TRUE;

	if (bWriteToEndOfFile) {
		LARGE_INTEGER l;
		l.QuadPart = m_real_file_size;
		if (!adjust_file_offset_down(l))
			return FALSE;
		offset = l.QuadPart;
	} else {
		if (bPagingIo) {
			LARGE_INTEGER l;
			l.QuadPart = m_real_file_size;
			if (!adjust_file_offset_down(l))
				return FALSE;

			if (offset >= l.QuadPart)
			{
				DbgPrint(L"CryptFile paging io past end of file, return\n");
				*pNwritten = 0;
				return true;
			}

			if ((offset + buflen) > l.QuadPart)
			{
				DbgPrint(L"CryptFile addjusting write length due to paging io\n");
				buflen = (DWORD)(l.QuadPart - offset);
			}
		}
	}	

	// if we're going to increase the size of the file we need
	// to hold onto exclusive access

	bool bGrowingFile = false;

	if (m_is_empty) {
		bGrowingFile = true;
		if (!WriteVersionAndFileId())
			return FALSE;	
	} else {
		LARGE_INTEGER size_down;
		size_down.QuadPart = m_real_file_size;
		adjust_file_offset_down(size_down);