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      1 /*	$NetBSD: refill.c,v 1.16 2012/03/27 15:05:42 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Chris Torek.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)refill.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 __RCSID("$NetBSD: refill.c,v 1.16 2012/03/27 15:05:42 christos Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <assert.h>
     45 #include <errno.h>
     46 #include <stdio.h>
     47 #include <stdlib.h>
     48 #include "reentrant.h"
     49 #include "local.h"
     50 
     51 #ifdef _REENTRANT
     52 extern rwlock_t __sfp_lock;
     53 #endif
     54 
     55 static int
     56 lflush(FILE *fp)
     57 {
     58 
     59 	_DIAGASSERT(fp != NULL);
     60 
     61 	if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
     62 		return __sflush(fp);
     63 	return 0;
     64 }
     65 
     66 /*
     67  * Refill a stdio buffer.
     68  * Return EOF on eof or error, 0 otherwise.
     69  */
     70 int
     71 __srefill(FILE *fp)
     72 {
     73 
     74 	_DIAGASSERT(fp != NULL);
     75 
     76 	/* make sure stdio is set up */
     77 	if (!__sdidinit)
     78 		__sinit();
     79 
     80 	fp->_r = 0;		/* largely a convenience for callers */
     81 
     82 	/* SysV does not make this test; take it out for compatibility */
     83 	if (fp->_flags & __SEOF)
     84 		return EOF;
     85 
     86 	/* if not already reading, have to be reading and writing */
     87 	if ((fp->_flags & __SRD) == 0) {
     88 		if ((fp->_flags & __SRW) == 0) {
     89 			errno = EBADF;
     90 			fp->_flags |= __SERR;
     91 			return EOF;
     92 		}
     93 		/* switch to reading */
     94 		if (fp->_flags & __SWR) {
     95 			if (__sflush(fp))
     96 				return EOF;
     97 			fp->_flags &= ~__SWR;
     98 			fp->_w = 0;
     99 			fp->_lbfsize = 0;
    100 		}
    101 		fp->_flags |= __SRD;
    102 	} else {
    103 		/*
    104 		 * We were reading.  If there is an ungetc buffer,
    105 		 * we must have been reading from that.  Drop it,
    106 		 * restoring the previous buffer (if any).  If there
    107 		 * is anything in that buffer, return.
    108 		 */
    109 		if (HASUB(fp)) {
    110 			FREEUB(fp);
    111 			if ((fp->_r = fp->_ur) != 0) {
    112 				fp->_p = fp->_up;
    113 				return 0;
    114 			}
    115 		}
    116 	}
    117 
    118 	if (fp->_bf._base == NULL)
    119 		__smakebuf(fp);
    120 
    121 	/*
    122 	 * Before reading from a line buffered or unbuffered file,
    123 	 * flush all line buffered output files, per the ANSI C
    124 	 * standard.
    125 	 */
    126 	if (fp->_flags & (__SLBF|__SNBF)) {
    127 		rwlock_rdlock(&__sfp_lock);
    128 		(void) _fwalk(lflush);
    129 		rwlock_unlock(&__sfp_lock);
    130 	}
    131 	fp->_p = fp->_bf._base;
    132 	fp->_r = (int)(*fp->_read)(fp->_cookie, (char *)fp->_p,
    133 	    (size_t)fp->_bf._size);
    134 	fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */
    135 	if (fp->_r <= 0) {
    136 		if (fp->_r == 0)
    137 			fp->_flags |= __SEOF;
    138 		else {
    139 			fp->_r = 0;
    140 			fp->_flags |= __SERR;
    141 		}
    142 		return EOF;
    143 	}
    144 	return 0;
    145 }
    146