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getenv.c revision 1.24 
      1 /*	$NetBSD: getenv.c,v 1.24 2010/10/01 20:11:32 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1987, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 #if 0
     35 static char sccsid[] = "@(#)getenv.c	8.1 (Berkeley) 6/4/93";
     36 #else
     37 __RCSID("$NetBSD: getenv.c,v 1.24 2010/10/01 20:11:32 christos Exp $");
     38 #endif
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include "namespace.h"
     42 #include <assert.h>
     43 #include <errno.h>
     44 #include <stdlib.h>
     45 #include <string.h>
     46 #include "reentrant.h"
     47 #include "local.h"
     48 
     49 #ifdef _REENTRANT
     50 rwlock_t __environ_lock = RWLOCK_INITIALIZER;
     51 #endif
     52 char **__environ_malloced;
     53 static char **saveenv;
     54 static size_t environ_malloced_len;
     55 
     56 __weak_alias(getenv_r, _getenv_r)
     57 
     58 /*
     59  * getenv --
     60  *	Returns ptr to value associated with name, if any, else NULL.
     61  *	XXX: we cannot use getenv_r to implement this, because getenv()
     62  *	cannot use a shared buffer, because if it did, subsequent calls
     63  *	to getenv would trash previous results.
     64  */
     65 char *
     66 getenv(const char *name)
     67 {
     68 	int offset;
     69 	char *result;
     70 
     71 	_DIAGASSERT(name != NULL);
     72 
     73 	rwlock_rdlock(&__environ_lock);
     74 	result = __findenv(name, &offset);
     75 	rwlock_unlock(&__environ_lock);
     76 	return result;
     77 }
     78 
     79 int
     80 getenv_r(const char *name, char *buf, size_t len)
     81 {
     82 	int offset;
     83 	char *result;
     84 	int rv = -1;
     85 
     86 	_DIAGASSERT(name != NULL);
     87 
     88 	rwlock_rdlock(&__environ_lock);
     89 	result = __findenv(name, &offset);
     90 	if (result == NULL) {
     91 		errno = ENOENT;
     92 		goto out;
     93 	}
     94 	if (strlcpy(buf, result, len) >= len) {
     95 		errno = ERANGE;
     96 		goto out;
     97 	}
     98 	rv = 0;
     99 out:
    100 	rwlock_unlock(&__environ_lock);
    101 	return rv;
    102 }
    103 
    104 int
    105 __allocenv(int offset)
    106 {
    107 	char **p;
    108 	size_t nl;
    109 
    110 	if (offset == -1 || saveenv != environ) {
    111 		char **ptr;
    112 		for (ptr = environ, offset = 0; *ptr != NULL; ptr++)
    113 			offset++;
    114 	}
    115 
    116 	nl = offset + 2; 	/* one for potentially new entry one for NULL */
    117 	if (nl <= environ_malloced_len && saveenv == environ)
    118 		return 0;
    119 
    120 	if (saveenv == environ) {		/* just increase size */
    121 		if ((p = realloc(saveenv, nl * sizeof(*p))) == NULL)
    122 			return -1;
    123 		saveenv = p;
    124 	} else {				/* get new space */
    125 		free(saveenv);
    126 		if ((saveenv = malloc(nl * sizeof(*saveenv))) == NULL)
    127 			return -1;
    128 		(void)memcpy(saveenv, environ, (nl - 2) * sizeof(*saveenv));
    129 	}
    130 	environ = saveenv;
    131 	environ[offset + 1] = NULL;
    132 
    133 	p = realloc(__environ_malloced, nl * sizeof(*p));
    134 	if (p == NULL)
    135 		return -1;
    136 
    137 	(void)memset(&p[environ_malloced_len], 0,
    138 	    (nl - environ_malloced_len) * sizeof(*p));
    139 	environ_malloced_len = nl;
    140 	__environ_malloced = p;
    141 
    142 	return 0;
    143 }
    144 
    145 /*
    146  * __findenv --
    147  *	Returns pointer to value associated with name, if any, else NULL.
    148  *	Sets offset to be the offset of the name/value combination in the
    149  *	environmental array, for use by setenv(3) and unsetenv(3).
    150  *	Explicitly removes '=' in argument name.
    151  *
    152  *	This routine *should* be a static; don't use it.
    153  */
    154 char *
    155 __findenv(const char *name, int *offset)
    156 {
    157 	size_t len;
    158 	const char *np;
    159 	char **p, *c;
    160 
    161 	if (name == NULL || environ == NULL)
    162 		return NULL;
    163 	for (np = name; *np && *np != '='; ++np)
    164 		continue;
    165 	len = np - name;
    166 	for (p = environ; (c = *p) != NULL; ++p)
    167 		if (strncmp(c, name, len) == 0 && c[len] == '=') {
    168 			*offset = (int)(p - environ);
    169 			return c + len + 1;
    170 		}
    171 	*offset = (int)(p - environ);
    172 	return NULL;
    173 }
    174