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