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31f7410f | 1 | /* Copyright (C) 1991, 1992, 1994, 1996, 1998 Free Software Foundation, Inc. |
f65fd747 | 2 | This file is part of the GNU C Library. |
28f540f4 | 3 | |
f65fd747 UD |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Library General Public License as | |
6 | published by the Free Software Foundation; either version 2 of the | |
7 | License, or (at your option) any later version. | |
28f540f4 | 8 | |
f65fd747 UD |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | Library General Public License for more details. | |
28f540f4 | 13 | |
f65fd747 UD |
14 | You should have received a copy of the GNU Library General Public |
15 | License along with the GNU C Library; see the file COPYING.LIB. If not, | |
16 | write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
17 | Boston, MA 02111-1307, USA. */ | |
28f540f4 | 18 | |
31f7410f | 19 | #include <endian.h> |
28f540f4 | 20 | #include <errno.h> |
31f7410f | 21 | #include <stdint.h> |
28f540f4 RM |
22 | #include <stdlib.h> |
23 | #include <string.h> | |
24 | #include <unistd.h> | |
25 | ||
26 | #ifndef HAVE_GNU_LD | |
27 | #define __environ environ | |
28 | #endif | |
29 | ||
31f7410f UD |
30 | /* Return the value of the environment variable NAME. This implementation |
31 | is tuned a bit in that it assumes no environment variable has an empty | |
32 | name which of course should always be true. We have a special case for | |
33 | one character names so that for the general case we can assume at least | |
34 | two characters which we can access. By doing this we can avoid using the | |
35 | `strncmp' most of the time. */ | |
28f540f4 | 36 | char * |
d68171ed UD |
37 | getenv (name) |
38 | const char *name; | |
28f540f4 | 39 | { |
d68171ed UD |
40 | const size_t len = strlen (name); |
41 | char **ep; | |
31f7410f | 42 | uint16_t name_start; |
28f540f4 | 43 | |
31f7410f | 44 | if (__environ == NULL || name[0] == '\0') |
28f540f4 RM |
45 | return NULL; |
46 | ||
31f7410f UD |
47 | if (name[1] == '\0') |
48 | { | |
49 | /* The name of the variable consists of only one character. Therefore | |
50 | the first two characters of the environment entry are this character | |
51 | and a '=' character. */ | |
52 | #if __BYTE_ORDER == __LITTLE_ENDIAN | |
53 | name_start = ('=' << 8) | *(const unsigned char *) name; | |
54 | #else | |
55 | # if __BYTE_ORDER == __BIG_ENDIAN | |
56 | name_start = '=' | ((*(const unsigned char *) name) << 8); | |
57 | # else | |
58 | #error "Funny byte order." | |
59 | # endif | |
60 | #endif | |
61 | for (ep = __environ; *ep != NULL; ++ep) | |
62 | { | |
63 | #if _STRING_ARCH_unaligned | |
64 | uint16_t ep_start = *(uint16_t *) *ep; | |
65 | #else | |
66 | uint16_t ep_start = (((unsigned char *) *ep)[0] | |
67 | | (((unsigned char *) *ep)[1] << 8)); | |
68 | #endif | |
69 | if (name_start == ep_start) | |
70 | return &(*ep)[2]; | |
71 | } | |
72 | } | |
73 | else | |
74 | { | |
75 | #if _STRING_ARCH_unaligned | |
76 | name_start = *(const uint16_t *) name; | |
77 | #else | |
78 | name_start = (((const unsigned char *) name)[0] | |
79 | | (((const unsigned char *) name)[1] << 8)); | |
80 | #endif | |
81 | len -= 2; | |
82 | name += 2; | |
83 | ||
84 | for (ep = __environ; *ep != NULL; ++ep) | |
85 | { | |
86 | #if _STRING_ARCH_unaligned | |
87 | uint16_t ep_start = *(uint16_t *) *ep; | |
88 | #else | |
89 | uint16_t ep_start = (((unsigned char *) *ep)[0] | |
90 | | (((unsigned char *) *ep)[1] << 8)); | |
91 | #endif | |
92 | ||
93 | if (name_start == ep_start && !strncmp (*ep + 2, name, len) | |
94 | && (*ep)[len + 2] == '=') | |
95 | return &(*ep)[len + 3]; | |
96 | } | |
97 | } | |
28f540f4 RM |
98 | |
99 | return NULL; | |
100 | } |