C++ String reaches over several NUL Bytes - c++

Question

I hate to ask this because I think this must be very trivial. But as someone who is used to high-level-languages this is a real problem.
I got a C++ program which uses PDFium to generate an Image to a PDF. And i have a C# program which communicates with the C++ program via Named Pipes. The PDF file (Which is saved as a byte-array) gets transmitted by the pipe. And here is my Problem.
On the 374th Position of the stream is a NUL byte (00) and im too stupid to somehow reach the data after it.
Here is my Code:
LPTSTR lpszPipename2 = TEXT("\\\\.\\pipe\\myNamedPipe2");
hPipe2=CreateFile(lpszPipename2, GENERIC_READ, 0,NULL,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);
if(ReadFile( hPipe2, chBuf, dwBytesToRead, &cbRead, NULL))
{
PDFData = chBuf;
}
dwBytes to read is the size of the file and cbRead shows the correct number. But PDFData only contains the first 373 bytes. I checked that the data beyond the 373th position is there with the Immediate Window i just don't know how to process it.
I gotta put the Data into a char-array.
As I already said, i think this is very trivial. But although i know where the problem comes from, i have simply no idea how to fix it.
Many Thanks and Regards
Michael
Edit: The C#-Code. Its everything but perfect. But i'm very sure this Problem is on the C++ side.
public void SendRawData(byte[] data)
{
while (clientse == null || clientse.stream == null)
{ }
if (clientse.stream.CanWrite)
{
clientse.stream.Write(data, 0, data.Length);
clientse.stream.Flush();
}
}
private void ListenForClients()
{
while (true)
{
clientHandle = CreateNamedPipe(this.pipeName, DUPLEX | FILE_FLAG_OVERLAPPED, 0, 255, BUFFER_SIZE, BUFFER_SIZE, 0, IntPtr.Zero);
//could not create named pipe
if (clientHandle.IsInvalid)
return;
int success = ConnectNamedPipe(clientHandle, IntPtr.Zero);
//could not connect client
if (success == 0)
return;
clientse = new Client();
clientse.handle = clientHandle;
clientse.stream = new FileStream(clientse.handle, FileAccess.ReadWrite, BUFFER_SIZE, true);
if (ClientType == 0)
{
Thread readThread = new Thread(new ThreadStart(Read));
readThread.Start();
}
}
}
"Solution":
Actually this never was a real problem. I just got my wires crossed. While chBuf seemed after copying it into PDFData or when i read its value is VS to only have those 373 bytes. All ~20 kilobytes were copied to that position.
I knew that, but i didn't understand how the PDFium sources should know that if the string terminates after 373 chars.
Well... the PDFium-sources know it cause i have to pass the length. Which was determined by
size_t len = PDFData.length();
and was therefore of course only 373 bytes.

Answer 1

The null character '\0' is used by C/C++ to terminate char* strings. So any library function (i.e. strlen(), strncpy(), etc) will use the null character as an implicit end-of-string indicator. Your code is obviously doing this somewhere. Instead, use something more like memcpy() or a std::vector<char> with an explicit data length.

Answer 2

Have a look at string:assign (http://www.cplusplus.com/reference/string/string/assign/)
String assignment operator from char * uses the C-style end-of-string convention. You need the "buffer" assign call:
string& assign (const char* s, size_t n);
This will include any NULs.
That being said, vector of bytes may indeed be a better choice.

Answer 3

Actually this never was a real problem. I just got my wires crossed. While chBuf seemed after copying it into PDFData or when i read its value is VS to only have those 373 bytes. All ~20 kilobytes were copied to that position. I knew that, but i didn't understand how the PDFium sources should know that if the string terminates after 373 chars.
Well... the PDFium-sources know it cause i have to pass the length. Which was determined by
size_t len = PDFData.length();
and was therefore of course only 373 bytes.
I'm sorry that i bothered you with that stuff