| /* Copyright (C) 1991-2018 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, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <endian.h> |
| #include <errno.h> |
| #include <stdint.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <unistd.h> |
| |
| |
| /* 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 (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 |
| name_start = '=' | ((*(const unsigned char *) name) << 8); |
| #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) |