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/* Copyright (C) 2009 Eric Blake
* Permission to use, copy, modify, and distribute this software
* is freely granted, provided that this notice is preserved.
*/
/*
FUNCTION
<<fpurge>>---discard pending file I/O
INDEX
fpurge
INDEX
_fpurge_r
INDEX
__fpurge
SYNOPSIS
#include <stdio.h>
int fpurge(FILE *<[fp]>);
int _fpurge_r(struct _reent *<[reent]>, FILE *<[fp]>);
#include <stdio.h>
#include <stdio_ext.h>
void __fpurge(FILE *<[fp]>);
DESCRIPTION
Use <<fpurge>> to clear all buffers of the given stream. For output
streams, this discards data not yet written to disk. For input streams,
this discards any data from <<ungetc>> and any data retrieved from disk
but not yet read via <<getc>>. This is more severe than <<fflush>>,
and generally is only needed when manually altering the underlying file
descriptor of a stream.
<<__fpurge>> behaves exactly like <<fpurge>> but does not return a value.
The alternate function <<_fpurge_r>> is a reentrant version, where the
extra argument <[reent]> is a pointer to a reentrancy structure, and
<[fp]> must not be NULL.
RETURNS
<<fpurge>> returns <<0>> unless <[fp]> is not valid, in which case it
returns <<EOF>> and sets <<errno>>.
PORTABILITY
These functions are not portable to any standard.
No supporting OS subroutines are required.
*/
#include <_ansi.h>
#include <stdio.h>
#ifndef __rtems__
#include <stdio_ext.h>
#endif
#include <errno.h>
#include "local.h"
/* Discard I/O from a single file. */
int
_DEFUN(_fpurge_r, (ptr, fp),
struct _reent *ptr,
register FILE * fp)
{
int t;
CHECK_INIT (ptr, fp);
_newlib_flockfile_start (fp);
t = fp->_flags;
if (!t)
{
ptr->_errno = EBADF;
_newlib_flockfile_exit (fp);
return EOF;
}
fp->_p = fp->_bf._base;
if ((t & __SWR) == 0)
{
fp->_r = 0;
if (HASUB (fp))
FREEUB (ptr, fp);
}
else
fp->_w = t & (__SLBF | __SNBF) ? 0 : fp->_bf._size;
_newlib_flockfile_end (fp);
return 0;
}
#ifndef _REENT_ONLY
int
_DEFUN(fpurge, (fp),
register FILE * fp)
{
return _fpurge_r (_REENT, fp);
}
#ifndef __rtems__
void
_DEFUN(__fpurge, (fp),
register FILE * fp)
{
_fpurge_r (_REENT, fp);
}
#endif
#endif /* _REENT_ONLY */
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