newlib/libc/stdio/fsetpos.c

   1 /*
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms are permitted
   6  * provided that the above copyright notice and this paragraph are
   7  * duplicated in all such forms and that any documentation,
   8  * and/or other materials related to such
   9  * distribution and use acknowledge that the software was developed
  10  * by the University of California, Berkeley.  The name of the
  11  * University may not be used to endorse or promote products derived
  12  * from this software without specific prior written permission.
  13  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  15  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  16  */
  17
  18 /*
  19 FUNCTION
  20 <<fsetpos>>---restore position of a stream or file
  21
  22 INDEX
  23         fsetpos
  24 INDEX
  25         _fsetpos_r
  26
  27 SYNOPSIS
  28         #include <stdio.h>
  29         int fsetpos(FILE *<[fp]>, const fpos_t *<[pos]>);
  30         int _fsetpos_r(struct _reent *<[ptr]>, FILE *<[fp]>,
  31                        const fpos_t *<[pos]>);
  32
  33 DESCRIPTION
  34 Objects of type <<FILE>> can have a ``position'' that records how much
  35 of the file your program has already read.  Many of the <<stdio>> functions
  36 depend on this position, and many change it as a side effect.
  37
  38 You can use <<fsetpos>> to return the file identified by <[fp]> to a previous
  39 position <<*<[pos]>>> (after first recording it with <<fgetpos>>).
  40
  41 See <<fseek>> for a similar facility.
  42
  43 RETURNS
  44 <<fgetpos>> returns <<0>> when successful.  If <<fgetpos>> fails, the
  45 result is <<1>>.  The reason for failure is indicated in <<errno>>:
  46 either <<ESPIPE>> (the stream identified by <[fp]> doesn't support
  47 repositioning) or <<EINVAL>> (invalid file position).
  48
  49 PORTABILITY
  50 ANSI C requires <<fsetpos>>, but does not specify the nature of
  51 <<*<[pos]>>> beyond identifying it as written by <<fgetpos>>.
  52
  53 Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
  54 <<lseek>>, <<read>>, <<sbrk>>, <<write>>.
  55 */
  56
  57 #include <_ansi.h>
  58 #include <reent.h>
  59 #include <stdio.h>
  60
  61 int
  62 _fsetpos_r (struct _reent * ptr,
  63        FILE * iop,
  64        const _fpos_t * pos)
  65 {
  66   int x = _fseek_r (ptr, iop, *pos, SEEK_SET);
  67
  68   if (x != 0)
  69     return 1;
  70   return 0;
  71 }
  72
  73 #ifndef _REENT_ONLY
  74
  75 int
  76 fsetpos (FILE * iop,
  77        const _fpos_t * pos)
  78 {
  79   return _fsetpos_r (_REENT, iop, pos);
  80 }
  81
  82 #endif /* !_REENT_ONLY */