xref: /netbsd-src/lib/libc/stdlib/getenv.c (revision 7db74b9a82dee21d579708a10c5cb35e512a9a79)
1 /*	$NetBSD: getenv.c,v 1.20 2010/09/23 17:30:49 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 1.20 2010/09/23 17:30:49 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 <bitstring.h>
47 #include "reentrant.h"
48 #include "local.h"
49 
50 #ifdef _REENTRANT
51 rwlock_t __environ_lock = RWLOCK_INITIALIZER;
52 #endif
53 bitstr_t *__environ_malloced;
54 static size_t environ_bitlen;
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 	bitstr_t *s;
108 	size_t nl;
109 
110 	if (offset == -1) {
111 		char **ptr;
112 		for (ptr = environ, offset = 0; *ptr; ptr++)
113 			offset++;
114 	}
115 	nl = bitstr_size(offset + 2);
116 	if (__environ_malloced == NULL) {
117 		s = malloc(nl);
118 	} else if (environ_bitlen < nl)
119 		s = realloc(__environ_malloced, nl);
120 	else
121 		return 0;
122 
123 	if (s == NULL)
124 		return -1;
125 
126 	(void)memset(&s[environ_bitlen], 0, nl - environ_bitlen);
127 	environ_bitlen = nl;
128 	__environ_malloced = s;
129 
130 	return 0;
131 }
132 
133 /*
134  * __findenv --
135  *	Returns pointer to value associated with name, if any, else NULL.
136  *	Sets offset to be the offset of the name/value combination in the
137  *	environmental array, for use by setenv(3) and unsetenv(3).
138  *	Explicitly removes '=' in argument name.
139  *
140  *	This routine *should* be a static; don't use it.
141  */
142 char *
143 __findenv(const char *name, int *offset)
144 {
145 	size_t len;
146 	const char *np;
147 	char **p, *c;
148 
149 	if (name == NULL || environ == NULL)
150 		return NULL;
151 	for (np = name; *np && *np != '='; ++np)
152 		continue;
153 	len = np - name;
154 	for (p = environ; (c = *p) != NULL; ++p)
155 		if (strncmp(c, name, len) == 0 && c[len] == '=') {
156 			*offset = p - environ;
157 			return c + len + 1;
158 		}
159 	*offset = p - environ;
160 	return NULL;
161 }
162