newlib/libc/stdio/fpurge.c

   1 /* Copyright (C) 2009 Eric Blake
   2  * Permission to use, copy, modify, and distribute this software
   3  * is freely granted, provided that this notice is preserved.
   4  */
   5
   6 /*
   7 FUNCTION
   8 <<fpurge>>---discard pending file I/O
   9
  10 INDEX
  11         fpurge
  12 INDEX
  13         _fpurge_r
  14 INDEX
  15         __fpurge
  16
  17 SYNOPSIS
  18         #include <stdio.h>
  19         int fpurge(FILE *<[fp]>);
  20
  21         int _fpurge_r(struct _reent *<[reent]>, FILE *<[fp]>);
  22
  23         #include <stdio.h>
  24         #include <stdio_ext.h>
  25         void  __fpurge(FILE *<[fp]>);
  26
  27
  28 DESCRIPTION
  29 Use <<fpurge>> to clear all buffers of the given stream.  For output
  30 streams, this discards data not yet written to disk.  For input streams,
  31 this discards any data from <<ungetc>> and any data retrieved from disk
  32 but not yet read via <<getc>>.  This is more severe than <<fflush>>,
  33 and generally is only needed when manually altering the underlying file
  34 descriptor of a stream.
  35
  36 <<__fpurge>> behaves exactly like <<fpurge>> but does not return a value.
  37
  38 The alternate function <<_fpurge_r>> is a reentrant version, where the
  39 extra argument <[reent]> is a pointer to a reentrancy structure, and
  40 <[fp]> must not be NULL.
  41
  42 RETURNS
  43 <<fpurge>> returns <<0>> unless <[fp]> is not valid, in which case it
  44 returns <<EOF>> and sets <<errno>>.
  45
  46 PORTABILITY
  47 These functions are not portable to any standard.
  48
  49 No supporting OS subroutines are required.
  50 */
  51
  52 #include <_ansi.h>
  53 #include <stdio.h>
  54 #ifndef __rtems__
  55 #include <stdio_ext.h>
  56 #endif
  57 #include <errno.h>
  58 #include "local.h"
  59
  60 /* Discard I/O from a single file.  */
  61
  62 int
  63 _fpurge_r (struct _reent *ptr,
  64        register FILE * fp)
  65 {
  66   int t;
  67
  68   CHECK_INIT (ptr, fp);
  69
  70   _newlib_flockfile_start (fp);
  71
  72   t = fp->_flags;
  73   if (!t)
  74     {
  75       _REENT_ERRNO(ptr) = EBADF;
  76       _newlib_flockfile_exit (fp);
  77       return EOF;
  78     }
  79   fp->_p = fp->_bf._base;
  80   if ((t & __SWR) == 0)
  81     {
  82       fp->_r = 0;
  83       if (HASUB (fp))
  84         FREEUB (ptr, fp);
  85     }
  86   else
  87     fp->_w = t & (__SLBF | __SNBF) ? 0 : fp->_bf._size;
  88   _newlib_flockfile_end (fp);
  89   return 0;
  90 }
  91
  92 #ifndef _REENT_ONLY
  93
  94 int
  95 fpurge (register FILE * fp)
  96 {
  97   return _fpurge_r (_REENT, fp);
  98 }
  99
 100 #ifndef __rtems__
 101
 102 void
 103 __fpurge (register FILE * fp)
 104 {
 105   _fpurge_r (_REENT, fp);
 106 }
 107
 108 #endif
 109
 110 #endif /* _REENT_ONLY */