data file help

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gilgamesh gilgamesh is offline Offline
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data file help

 
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  #1
May 14th, 2003
i need to be able to add data to my .dat file without deleting my old data during a program run can anyone help me?
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Re: data file help

 
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May 14th, 2003
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Originally Posted by gilgamesh
i need to be able to add data to my .dat file without deleting my old data during a program run can anyone help me?

If this is a console app (DOS program) or UNIX program that outputs to standard output, you could redirect the output to your data file

program.exe >> datafile.dat


If this is a Windows program, you can use CreateFile with the following arguments

C Syntax (Toggle Plain Text) 
  1. HANDLE hFile = INVALID_HANDLE_VALUE;
  2. hFile = CreateFile("yourfile.dat", 
  3.   GENERIC_READ | GENERIC_WRITE, 
  4.   0, // no file sharing
  5.   NULL, // no security descriptor
  6.   OPEN_ALWAYS, // creates if not found
  7.   FILE_ATTRIBUTE_NORMAL,
  8.   NULL); // No template handle

This returns a HANDLE that you can pass to ReadFile and WriteFile

Using SetFilePointer if you need to position to any part of the file.

C Syntax (Toggle Plain Text) 
  1. if (hFile != INVALID_HANDLE_VALUE)
  2. {
  3.   DWORD bytesWritten;
  4.   if (FALSE == WriteFile(hFile,
  5.     dataBuffer, // data to write
  6.     dataBufferSize,
  7.     &bytesWritten,
  8.     NULL))  // not using overlapped I/O
  9.   {
  10.     MessageBox(GetActiveWindow(),
  11.       "Error", "Error", MB_ICONSTOP);
  12.   }
  13.   // will want to verify 
  14.   // bytesWritten == dataBufferSize
  15. }

Be sure to close the file with
C Syntax (Toggle Plain Text) 
  1. CloseHandle(hFile);

Hope this helps.
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