Subversion Repositories openrisc_me

/* 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

ANSI_SYNOPSIS

        #include <stdio.h>

        int fpurge(FILE *<[fp]>);

        int _fpurge_r(struct _reent *<[reent]>, 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.

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>

#include <errno.h>

#include "local.h"

/* Discard I/O from a single file.  */

int

_DEFUN(_fpurge_r, (ptr, fp),

       struct _reent *ptr _AND

       register FILE * fp)

{

  int t;

  CHECK_INIT (ptr, fp);

  _flockfile (fp);

  t = fp->_flags;

  if (!t)

    {

      ptr->_errno = EBADF;

      _funlockfile (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;

  _funlockfile (fp);

  return 0;

}

#ifndef _REENT_ONLY

int

_DEFUN(fpurge, (fp),

       register FILE * fp)

{

  return _fpurge_r (_REENT, fp);

}

#endif /* _REENT_ONLY */