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author | Ulrich Drepper <drepper@redhat.com> | 2004-12-22 20:10:10 +0000 |
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committer | Ulrich Drepper <drepper@redhat.com> | 2004-12-22 20:10:10 +0000 |
commit | a334319f6530564d22e775935d9c91663623a1b4 (patch) | |
tree | b5877475619e4c938e98757d518bb1e9cbead751 /sysdeps/generic/getenv.c | |
parent | 0ecb606cb6cf65de1d9fc8a919bceb4be476c602 (diff) | |
download | glibc-a334319f6530564d22e775935d9c91663623a1b4.tar.gz glibc-a334319f6530564d22e775935d9c91663623a1b4.tar.xz glibc-a334319f6530564d22e775935d9c91663623a1b4.zip |
(CFLAGS-tst-align.c): Add -mpreferred-stack-boundary=4.
Diffstat (limited to 'sysdeps/generic/getenv.c')
-rw-r--r-- | sysdeps/generic/getenv.c | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/sysdeps/generic/getenv.c b/sysdeps/generic/getenv.c new file mode 100644 index 0000000000..d659f66022 --- /dev/null +++ b/sysdeps/generic/getenv.c @@ -0,0 +1,101 @@ +/* Copyright (C) 1991,92,94,96,98,99,2002 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <endian.h> +#include <errno.h> +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#ifndef HAVE_GNU_LD +#define __environ environ +#endif + +/* Return the value of the environment variable NAME. This implementation + is tuned a bit in that it assumes no environment variable has an empty + name which of course should always be true. We have a special case for + one character names so that for the general case we can assume at least + two characters which we can access. By doing this we can avoid using the + `strncmp' most of the time. */ +char * +getenv (name) + const char *name; +{ + size_t len = strlen (name); + char **ep; + uint16_t name_start; + + if (__environ == NULL || name[0] == '\0') + return NULL; + + if (name[1] == '\0') + { + /* The name of the variable consists of only one character. Therefore + the first two characters of the environment entry are this character + and a '=' character. */ +#if __BYTE_ORDER == __LITTLE_ENDIAN || !_STRING_ARCH_unaligned + name_start = ('=' << 8) | *(const unsigned char *) name; +#else +# if __BYTE_ORDER == __BIG_ENDIAN + name_start = '=' | ((*(const unsigned char *) name) << 8); +# else + #error "Funny byte order." +# endif +#endif + for (ep = __environ; *ep != NULL; ++ep) + { +#if _STRING_ARCH_unaligned + uint16_t ep_start = *(uint16_t *) *ep; +#else + uint16_t ep_start = (((unsigned char *) *ep)[0] + | (((unsigned char *) *ep)[1] << 8)); +#endif + if (name_start == ep_start) + return &(*ep)[2]; + } + } + else + { +#if _STRING_ARCH_unaligned + name_start = *(const uint16_t *) name; +#else + name_start = (((const unsigned char *) name)[0] + | (((const unsigned char *) name)[1] << 8)); +#endif + len -= 2; + name += 2; + + for (ep = __environ; *ep != NULL; ++ep) + { +#if _STRING_ARCH_unaligned + uint16_t ep_start = *(uint16_t *) *ep; +#else + uint16_t ep_start = (((unsigned char *) *ep)[0] + | (((unsigned char *) *ep)[1] << 8)); +#endif + + if (name_start == ep_start && !strncmp (*ep + 2, name, len) + && (*ep)[len + 2] == '=') + return &(*ep)[len + 3]; + } + } + + return NULL; +} +libc_hidden_def (getenv) |