DosSetFileSize

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Description

Changes the size of a file.

Syntax

#define INCL_DOSFILEMGR
#include <os2.h>

HFILE     hFile;   /*  Handle of the file whose size to be changed. */
ULONG     cbSize;  /*  New size, in bytes, of the file. */
APIRET    ulrc;    /*  Return Code. */

ulrc = DosSetFileSize(hFile, cbSize);

Parameters

hFile (HFILE) - input 
Handle of the file whose size to be changed.
cbSize (ULONG) - input 
New size, in bytes, of the file.

Return Code

ulrc (APIRET) - returns

DosSetFileSize returns one of the following values:

  • 0 NO_ERROR
  • 5 ERROR_ACCESS_DENIED
  • 6 ERROR_INVALID_HANDLE
  • 26 ERROR_NOT_DOS_DISK
  • 33 ERROR_LOCK_VIOLATION
  • 87 ERROR_INVALID_PARAMETER
  • 112 ERROR_DISK_FULL

Remarks

When DosSetFileSize is issued, the file must be open in a mode that allows write access.

The size of the open file can be truncated or extended. If the file size is being extended, the file system tries to allocate additional bytes in a contiguous (or nearly contiguous) space on the medium. The values of the new bytes are undefined.

Example Code

This example writes to a file named "DOSMAN.DAT", resets the buffer, and changes the file size.

#define INCL_DOSFILEMGR          /* File Manager values */
#define INCL_DOSERRORS           /* DOS Error values    */
#include <os2.h>
#include <stdio.h>
#include <string.h>

int main(VOID) {
   HFILE  hfFileHandle   = 0L;     /* Handle for file being manipulated */
   ULONG  ulAction       = 0;      /* Action taken by DosOpen */
   ULONG  ulWrote        = 0;      /* Number of bytes written by DosWrite */
   UCHAR  uchFileName[20]  = "dosman.dat",     /* Name of file */
          uchFileData[4]   = "DATA";            /* Data to write to file */
   APIRET rc             = NO_ERROR;            /* Return code */

   /* Open the file dosman.dat.  Use an existing file or create a new */
   /* one if it doesn't exist.                                      */
   rc = DosOpen(uchFileName, &hfFileHandle, &ulAction, 4L,
                FILE_ARCHIVED | FILE_NORMAL,
                OPEN_ACTION_CREATE_IF_NEW | OPEN_ACTION_OPEN_IF_EXISTS,
                OPEN_FLAGS_NOINHERIT | OPEN_SHARE_DENYNONE  |
                OPEN_ACCESS_READWRITE, 0L);
   if (rc != NO_ERROR) {
      printf("DosOpen error: return code = %u\n", rc);
      return 1;
   }

   rc = DosWrite (hfFileHandle, (PVOID) uchFileData,
                  sizeof (uchFileData), &ulWrote);
   if (rc != NO_ERROR) {
      printf("DosWrite error: return code = %u\n", rc);
      return 1;
   }

   rc = DosResetBuffer (hfFileHandle);
   if (rc != NO_ERROR) {
      printf("DosResetBuffer error: return code = %u\n", rc);
      return 1;
   } /* endif */

   rc = DosSetFileSize (hfFileHandle, 8L);    /* Change file size */
   if (rc != NO_ERROR) {
      printf("DosSetFileSize error: return code = %u\n", rc);
      return 1;
   }

   return NO_ERROR;
}

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