libc/stdlib/setenv.c

   1 /* Copyright (C) 1992,95,96,97,98,99,2000,2001 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If
  16    not, see <http://www.gnu.org/licenses/>.
  17
  18    modified for uClibc by Erik Andersen <andersen@codepoet.org>
  19 */
  20
  21 #include <features.h>
  22 #include <errno.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26
  27
  28 #include <bits/uClibc_mutex.h>
  29 __UCLIBC_MUTEX_STATIC(mylock, PTHREAD_MUTEX_INITIALIZER);
  30
  31
  32 /* If this variable is not a null pointer we allocated the current
  33    environment.  */
  34 static char **last_environ;
  35
  36
  37 /* This function is used by `setenv' and `putenv'.  The difference between
  38    the two functions is that for the former must create a new string which
  39    is then placed in the environment, while the argument of `putenv'
  40    must be used directly.  This is all complicated by the fact that we try
  41    to reuse values once generated for a `setenv' call since we can never
  42    free the strings. [in uclibc, we do not]  */
  43 static int __add_to_environ(const char *name, const char *value,
  44                 int replace)
  45 {
  46         register char **ep;
  47         register size_t size;
  48         char *var_val;
  49         char **new_environ;
  50         /* name may come from putenv() and thus may contain "=VAL" part */
  51         const size_t namelen = strchrnul(name, '=') - name;
  52         int rv = -1;
  53
  54         __UCLIBC_MUTEX_LOCK(mylock);
  55
  56         /* We have to get the pointer now that we have the lock and not earlier
  57            since another thread might have created a new environment.  */
  58         ep = __environ;
  59
  60         size = 0;
  61         if (ep != NULL) {
  62                 while (*ep != NULL) {
  63                         if (!strncmp(*ep, name, namelen) && (*ep)[namelen] == '=') {
  64                                 /* Found */
  65                                 if (!replace)
  66                                         goto DONE_OK;
  67                                 goto REPLACE;
  68                         }
  69                         ++size;
  70                         ++ep;
  71                 }
  72         }
  73
  74         /* Not found, add at the end */
  75
  76         /* We allocated this space; we can extend it.  */
  77         new_environ = realloc(last_environ, (size + 2) * sizeof(char *));
  78         if (new_environ == NULL) {
  79                 /* __set_errno(ENOMEM); */
  80                 goto DONE;
  81         }
  82         if (__environ != last_environ) {
  83                 memcpy(new_environ, __environ, size * sizeof(char *));
  84         }
  85         last_environ = __environ = new_environ;
  86
  87         ep = &new_environ[size];
  88         /* Ensure env is NULL terminated in case malloc below fails */
  89         ep[0] = NULL;
  90         ep[1] = NULL;
  91
  92  REPLACE:
  93         var_val = (char*) name;
  94         /* Build VAR=VAL if we called by setenv, not putenv.  */
  95         if (value != NULL) {
  96                 const size_t vallen = strlen(value) + 1;
  97
  98                 var_val = malloc(namelen + 1 + vallen);
  99                 if (var_val == NULL) {
 100                         /* __set_errno(ENOMEM); */
 101                         goto DONE;
 102                 }
 103                 memcpy(var_val, name, namelen);
 104                 var_val[namelen] = '=';
 105                 memcpy(&var_val[namelen + 1], value, vallen);
 106         }
 107         *ep = var_val;
 108
 109  DONE_OK:
 110         rv = 0;
 111
 112  DONE:
 113         __UCLIBC_MUTEX_UNLOCK(mylock);
 114         return rv;
 115 }
 116
 117 int setenv(const char *name, const char *value, int replace)
 118 {
 119         if (name == NULL || *name == '\0' || strchr (name, '=') != NULL) {
 120                 __set_errno(EINVAL);
 121                 return -1;
 122         }
 123
 124         /* NB: setenv("VAR", NULL, 1) inserts "VAR=" string */
 125         return __add_to_environ(name, value ? value : "", replace);
 126 }
 127 libc_hidden_def(setenv)
 128
 129 int unsetenv(const char *name)
 130 {
 131         const char *eq;
 132         size_t len;
 133         char **ep;
 134
 135         if (name == NULL || *name == '\0'
 136          || *(eq = strchrnul(name, '=')) == '='
 137         ) {
 138                 __set_errno(EINVAL);
 139                 return -1;
 140         }
 141         len = eq - name; /* avoiding strlen this way */
 142
 143         __UCLIBC_MUTEX_LOCK(mylock);
 144         ep = __environ;
 145         /* NB: clearenv(); unsetenv("foo"); should not segfault */
 146         if (ep) while (*ep != NULL) {
 147                 if (!strncmp(*ep, name, len) && (*ep)[len] == '=') {
 148                         /* Found it.  Remove this pointer by moving later ones back.  */
 149                         char **dp = ep;
 150                         do {
 151                                 dp[0] = dp[1];
 152                         } while (*dp++);
 153                         /* Continue the loop in case NAME appears again.  */
 154                 } else {
 155                         ++ep;
 156                 }
 157         }
 158         __UCLIBC_MUTEX_UNLOCK(mylock);
 159         return 0;
 160 }
 161 libc_hidden_def(unsetenv)
 162
 163 /* The `clearenv' was planned to be added to POSIX.1 but probably
 164    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 165    for Fortran 77) requires this function.  */
 166 int clearenv(void)
 167 {
 168         __UCLIBC_MUTEX_LOCK(mylock);
 169         /* If we allocated this environment we can free it.
 170          * If we did not allocate this environment, it's NULL already
 171          * and is safe to free().  */
 172         free(last_environ);
 173         last_environ = NULL;
 174         /* Clearing environ removes the whole environment.  */
 175         __environ = NULL;
 176         __UCLIBC_MUTEX_UNLOCK(mylock);
 177         return 0;
 178 }
 179
 180 /* Put STRING, which is of the form "NAME=VALUE", in the environment.  */
 181 int putenv(char *string)
 182 {
 183         if (strchr(string, '=') != NULL) {
 184                 return __add_to_environ(string, NULL, 1);
 185         }
 186         return unsetenv(string);
 187 }