compiler/clib/lseek.c

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