newlib/libc/stdio64/fgetpos64.c

   1 /*
   2 FUNCTION
   3 <<fgetpos64>>---record position in a large stream or file
   4
   5 INDEX
   6         fgetpos64
   7 INDEX
   8         _fgetpos64_r
   9
  10 SYNOPSIS
  11         #include <stdio.h>
  12         int fgetpos64(FILE *<[fp]>, _fpos64_t *<[pos]>);
  13         int _fgetpos64_r(struct _reent *<[ptr]>, FILE *<[fp]>,
  14                          _fpos64_t *<[pos]>);
  15
  16 DESCRIPTION
  17 Objects of type <<FILE>> can have a ``position'' that records how much
  18 of the file your program has already read.  Many of the <<stdio>> functions
  19 depend on this position, and many change it as a side effect.
  20
  21 You can use <<fgetpos64>> to report on the current position for a file
  22 identified by <[fp]> that was opened by <<fopen64>>; <<fgetpos>> will write
  23 a value representing that position at <<*<[pos]>>>.  Later, you can
  24 use this value with <<fsetpos64>> to return the file to this
  25 position.
  26
  27 In the current implementation, <<fgetpos64>> simply uses a character
  28 count to represent the file position; this is the same number that
  29 would be returned by <<ftello64>>.
  30
  31 RETURNS
  32 <<fgetpos64>> returns <<0>> when successful.  If <<fgetpos64>> fails, the
  33 result is <<1>>.  Failure occurs on streams that do not support
  34 positioning or streams not opened via <<fopen64>>; the global <<errno>>
  35 indicates these conditions with the value <<ESPIPE>>.
  36
  37 PORTABILITY
  38 <<fgetpos64>> is a glibc extension.
  39
  40 No supporting OS subroutines are required.
  41 */
  42
  43 #include <stdio.h>
  44
  45 #ifdef __LARGE64_FILES
  46
  47 int
  48 _fgetpos64_r (struct _reent * ptr,
  49         FILE * fp,
  50         _fpos64_t * pos)
  51 {
  52   *pos = (_fpos64_t)_ftello64_r (ptr, fp);
  53
  54   if (*pos != -1)
  55     {
  56       return 0;
  57     }
  58   return 1;
  59 }
  60
  61 #ifndef _REENT_ONLY
  62
  63 int
  64 fgetpos64 (FILE * fp,
  65         _fpos64_t * pos)
  66 {
  67   return _fgetpos64_r (_REENT, fp, pos);
  68 }
  69
  70 #endif /* !_REENT_ONLY */
  71
  72 #endif /* __LARGE64_FILES */