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flockfile.c revision 1.4 
      1 /*	$NetBSD: flockfile.c,v 1.4 2003/02/01 03:25:00 nathanw Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2002 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Nathan J. Williams.
      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. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 __RCSID("$NetBSD: flockfile.c,v 1.4 2003/02/01 03:25:00 nathanw Exp $");
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include "namespace.h"
     45 
     46 #include <assert.h>
     47 #include <errno.h>
     48 #include <stdio.h>
     49 #include <string.h>
     50 #include "reentrant.h"
     51 #include "local.h"
     52 
     53 #ifdef __weak_alias
     54 __weak_alias(flockfile,_flockfile)
     55 __weak_alias(ftrylockfile,_ftrylockfile)
     56 __weak_alias(funlockfile,_funlockfile)
     57 #endif
     58 
     59 #ifdef _REENTRANT
     60 /*
     61  * XXX This code makes the assumption that a thr_t (pthread_t) is a
     62  * XXX pointer.
     63  */
     64 
     65 extern int __isthreaded;
     66 
     67 void
     68 flockfile(FILE *fp)
     69 {
     70 
     71 	if (__isthreaded == 0)
     72 		return;
     73 
     74 	mutex_lock(&_LOCK(fp));
     75 
     76 	if (_LOCKOWNER(fp) == thr_self()) {
     77 		_LOCKCOUNT(fp)++;
     78 	} else {
     79 		while (_LOCKOWNER(fp) != NULL)
     80 			cond_wait(&_LOCKCOND(fp), &_LOCK(fp));
     81 		_LOCKOWNER(fp) = thr_self();
     82 		_LOCKCOUNT(fp) = 1;
     83 	}
     84 
     85 	mutex_unlock(&_LOCK(fp));
     86 }
     87 
     88 int
     89 ftrylockfile(FILE *fp)
     90 {
     91 	int retval;
     92 
     93 	if (__isthreaded == 0)
     94 		return 0;
     95 
     96 	retval = 0;
     97 	mutex_lock(&_LOCK(fp));
     98 
     99 	if (_LOCKOWNER(fp) == thr_self()) {
    100 		_LOCKCOUNT(fp)++;
    101 	} else if (_LOCKOWNER(fp) == NULL) {
    102 		_LOCKOWNER(fp) = thr_self();
    103 		_LOCKCOUNT(fp) = 1;
    104 	} else
    105 		retval = -1;
    106 
    107 	mutex_unlock(&_LOCK(fp));
    108 
    109 	return retval;
    110 }
    111 
    112 void
    113 funlockfile(FILE *fp)
    114 {
    115 
    116 	if (__isthreaded == 0)
    117 		return;
    118 
    119 	mutex_lock(&_LOCK(fp));
    120 
    121 	_LOCKCOUNT(fp)--;
    122 	if (_LOCKCOUNT(fp) == 0) {
    123 		_LOCKOWNER(fp) = NULL;
    124 		cond_signal(&_LOCKCOND(fp));
    125 	}
    126 
    127 	mutex_unlock(&_LOCK(fp));
    128 }
    129 
    130 #else /* _REENTRANT */
    131 
    132 void
    133 flockfile(FILE *fp)
    134 {
    135 	/* LINTED deliberate lack of effect */
    136 	(void)fp;
    137 
    138 	return;
    139 }
    140 
    141 int
    142 ftrylockfile(FILE *fp)
    143 {
    144 	/* LINTED deliberate lack of effect */
    145 	(void)fp;
    146 
    147 	return (0);
    148 }
    149 
    150 void
    151 funlockfile(FILE *fp)
    152 {
    153 	/* LINTED deliberate lack of effect */
    154 	(void)fp;
    155 
    156 	return;
    157 }
    158 
    159 #endif /* _REENTRANT */
    160