compiler/stdc/fseek.c

   1 /*
   2     Copyright © 1995-2013, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     C99 function fseek()
   6 */
   7 #include <dos/dos.h>
   8 #include <proto/dos.h>
   9 #include <errno.h>
  10
  11 #include "__stdio.h"
  12
  13 #define DEBUG 0
  14 #include <aros/debug.h>
  15
  16 /*****************************************************************************
  17
  18     NAME */
  19 #include <stdio.h>
  20
  21         int fseek (
  22
  23 /*  SYNOPSIS */
  24         FILE * stream,
  25         long   offset,
  26         int    whence)
  27
  28 /*  FUNCTION
  29         Change the current position in a stream.
  30
  31     INPUTS
  32         stream - Modify this stream
  33         offset, whence - How to modify the current position. whence
  34                 can be SEEK_SET, then offset is the absolute position
  35                 in the file (0 is the first byte), SEEK_CUR then the
  36                 position will change by offset (ie. -5 means to move
  37                 5 bytes to the beginning of the file) or SEEK_END.
  38                 SEEK_END means that the offset is relative to the
  39                 end of the file (-1 is the last byte and 0 is
  40                 the EOF).
  41
  42     RESULT
  43         0 on success and -1 on error. If an error occurred, the global
  44         variable errno is set.
  45
  46     NOTES
  47         The seek is handled by the files system so effects of what happens
  48         when seeking after end of file may differ between file systems.
  49
  50     EXAMPLE
  51
  52     BUGS
  53         Not fully compatible with iso fseek, especially in 'ab' and 'a+b'
  54         modes
  55
  56     SEE ALSO
  57         fopen(), fwrite()
  58
  59     INTERNALS
  60
  61 ******************************************************************************/
  62 {
  63     LONG mode;
  64     BPTR fh = stream->fh;
  65
  66     D(bug("[stdcio/fseek()] Entering stream=0x%x, offset=%d, whence=%d\n",
  67           stream, offset, whence
  68     ));
  69
  70     switch (whence)
  71     {
  72     case SEEK_SET:
  73         mode = OFFSET_BEGINNING;
  74         break;
  75
  76     case SEEK_CUR:
  77         mode = OFFSET_CURRENT;
  78         break;
  79
  80     case SEEK_END:
  81         mode = OFFSET_END;
  82         break;
  83
  84     default:
  85         errno = EINVAL;
  86         return -1;
  87     }
  88
  89     if (Seek(fh, offset, mode) < 0)
  90     {
  91         D(bug("[stdcio/fseek()] Failed (IoErr()=%d)\n", IoErr()));
  92         if (IoErr() == ERROR_UNKNOWN)
  93             errno = EINVAL;
  94         else
  95             errno = __stdc_ioerr2errno(IoErr());
  96         return -1;
  97     }
  98     else
  99     {
 100         D(bug("[stdcio/fseek()] Done\n"));
 101         return 0;
 102     }
 103 } /* fseek */