Question

I originally used GetFileSize() and then found out that is not the correct way to go. Please give me some suggestions.

Answer 1

When you launch a process, you will get an output stream (assuming you have redirected its standard output). A proper way of dealing with streams is to read it by chunks, multiple times untill you reach end of the stream. A sample code is on MSDN page — look for function ReadFromPipe(void). Here is the copy of the code:

void ReadFromPipe(void) 

// Read output from the child process's pipe for STDOUT
// and write to the parent process's pipe for STDOUT. 
// Stop when there is no more data. 
{ 
   DWORD dwRead, dwWritten; 
   CHAR chBuf[BUFSIZE]; 
   BOOL bSuccess = FALSE;
   HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);

   for (;;) 
   { 
      bSuccess = ReadFile( g_hChildStd_OUT_Rd, chBuf, BUFSIZE, &dwRead, NULL);
      if( ! bSuccess || dwRead == 0 ) break; 

      // ... -> do your processing here.
   } 
} 

If you do need to aggregate the entire stream into one buffer, you can use dynamically allocated containers, e.g. std::vector, std::string, std::list, etc.