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data file help

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Join Date: May 2003

Posts: 1

Reputation: gilgamesh is an unknown quantity at this point

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gilgamesh

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Newbie Poster

data file help

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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Join Date: May 2003

Posts: 2

Reputation: evenstar is an unknown quantity at this point

Solved Threads: 0

evenstar

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Newbie Poster

Re: data file help

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

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
HANDLE hFile = INVALID_HANDLE_VALUE;
hFile = CreateFile("yourfile.dat", 
  GENERIC_READ | GENERIC_WRITE, 
  0, // no file sharing
  NULL, // no security descriptor
  OPEN_ALWAYS, // creates if not found
  FILE_ATTRIBUTE_NORMAL,
  NULL); // No template handle
HANDLE hFile = INVALID_HANDLE_VALUE;
hFile = CreateFile("yourfile.dat", 
  GENERIC_READ | GENERIC_WRITE, 
  0, // no file sharing
  NULL, // no security descriptor
  OPEN_ALWAYS, // creates if not found
  FILE_ATTRIBUTE_NORMAL,
  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.

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
if (hFile != INVALID_HANDLE_VALUE)
{
  DWORD bytesWritten;
  if (FALSE == WriteFile(hFile,
    dataBuffer, // data to write
    dataBufferSize,
    &bytesWritten,
    NULL))  // not using overlapped I/O
  {
    MessageBox(GetActiveWindow(),
      "Error", "Error", MB_ICONSTOP);
  }
  // will want to verify 
  // bytesWritten == dataBufferSize
}
if (hFile != INVALID_HANDLE_VALUE)
{
  DWORD bytesWritten;
  if (FALSE == WriteFile(hFile,
    dataBuffer, // data to write
    dataBufferSize,
    &bytesWritten,
    NULL))  // not using overlapped I/O
  {
    MessageBox(GetActiveWindow(),
      "Error", "Error", MB_ICONSTOP);
  }
  // will want to verify 
  // bytesWritten == dataBufferSize
}