compiler/clib/fseek.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Change the position in a stream.
   6 */
   7
   8 #include <errno.h>
   9 #include <dos/dos.h>
  10 #include <proto/dos.h>
  11 #include "__errno.h"
  12 #include "__stdio.h"
  13 #include "__open.h"
  14
  15 /*****************************************************************************
  16
  17     NAME */
  18 #include <stdio.h>
  19
  20         int fseek (
  21
  22 /*  SYNOPSIS */
  23         FILE * stream,
  24         long   offset,
  25         int    whence)
  26
  27 /*  FUNCTION
  28         Change the current position in a stream.
  29
  30     INPUTS
  31         stream - Modify this stream
  32         offset, whence - How to modify the current position. whence
  33                 can be SEEK_SET, then offset is the absolute position
  34                 in the file (0 is the first byte), SEEK_CUR then the
  35                 position will change by offset (ie. -5 means to move
  36                 5 bytes to the beginning of the file) or SEEK_END.
  37                 SEEK_END means that the offset is relative to the
  38                 end of the file (-1 is the last byte and 0 is
  39                 the EOF).
  40
  41     RESULT
  42         0 on success and -1 on error. If an error occurred, the global
  43         variable errno is set.
  44
  45     NOTES
  46
  47     EXAMPLE
  48
  49     BUGS
  50
  51     SEE ALSO
  52         fopen(), fwrite()
  53
  54     INTERNALS
  55
  56 ******************************************************************************/
  57 {
  58     int  cnt;
  59     BPTR fh;
  60     fdesc *fdesc = __getfdesc(stream->fd);
  61
  62     if (!fdesc)
  63     {
  64         errno = EBADF;
  65         return -1;
  66     }
  67
  68     switch (whence)
  69     {
  70         case SEEK_SET: whence = OFFSET_BEGINNING; break;
  71         case SEEK_CUR: whence = OFFSET_CURRENT; break;
  72         case SEEK_END: whence = OFFSET_END; break;
  73
  74         default:
  75             errno = EINVAL;
  76             return -1;
  77     }
  78
  79     fh = (BPTR)(fdesc->fh);
  80
  81     /* This is buffered IO, flush the buffer before any Seek */
  82     Flush (fh);
  83     cnt = Seek (fh, offset, whence);
  84
  85     if (cnt == -1)
  86         errno = IoErr2errno (IoErr ());
  87     else
  88         cnt = 0;
  89
  90     return cnt;
  91 } /* fseek */