newlib/libc/stdio/fgetpos.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 <<fgetpos>>---record position in a stream or file
  21
  22 INDEX
  23         fgetpos
  24 INDEX
  25         _fgetpos_r
  26
  27 SYNOPSIS
  28         #include <stdio.h>
  29         int fgetpos(FILE *restrict <[fp]>, fpos_t *restrict <[pos]>);
  30         int _fgetpos_r(struct _reent *<[ptr]>, FILE *restrict <[fp]>, fpos_t *restrict <[pos]>);
  31
  32 DESCRIPTION
  33 Objects of type <<FILE>> can have a ``position'' that records how much
  34 of the file your program has already read.  Many of the <<stdio>> functions
  35 depend on this position, and many change it as a side effect.
  36
  37 You can use <<fgetpos>> to report on the current position for a file
  38 identified by <[fp]>; <<fgetpos>> will write a value
  39 representing that position at <<*<[pos]>>>.  Later, you can
  40 use this value with <<fsetpos>> to return the file to this
  41 position.
  42
  43 In the current implementation, <<fgetpos>> simply uses a character
  44 count to represent the file position; this is the same number that
  45 would be returned by <<ftell>>.
  46
  47 RETURNS
  48 <<fgetpos>> returns <<0>> when successful.  If <<fgetpos>> fails, the
  49 result is <<1>>.  Failure occurs on streams that do not support
  50 positioning; the global <<errno>> indicates this condition with the
  51 value <<ESPIPE>>.
  52
  53 PORTABILITY
  54 <<fgetpos>> is required by the ANSI C standard, but the meaning of the
  55 value it records is not specified beyond requiring that it be
  56 acceptable as an argument to <<fsetpos>>.  In particular, other
  57 conforming C implementations may return a different result from
  58 <<ftell>> than what <<fgetpos>> writes at <<*<[pos]>>>.
  59
  60 No supporting OS subroutines are required.
  61 */
  62
  63 #include <_ansi.h>
  64 #include <reent.h>
  65 #include <stdio.h>
  66
  67 int
  68 _fgetpos_r (struct _reent * ptr,
  69        FILE *__restrict fp,
  70        _fpos_t *__restrict pos)
  71 {
  72   *pos = _ftell_r (ptr, fp);
  73
  74   if (*pos != -1)
  75     {
  76       return 0;
  77     }
  78   return 1;
  79 }
  80
  81 #ifndef _REENT_ONLY
  82
  83 int
  84 fgetpos (FILE *__restrict fp,
  85        _fpos_t *__restrict pos)
  86 {
  87   return _fgetpos_r (_REENT, fp, pos);
  88 }
  89
  90 #endif /* !_REENT_ONLY */