usr/src/boot/lib/libstand/environment.c

   1 /*
   2  * Copyright (c) 1998 Michael Smith.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD$");
  29
  30 /*
  31  * Manage an environment-like space in which string variables may be stored.
  32  * Provide support for some method-like operations for setting/retrieving
  33  * variables in order to allow some type strength.
  34  */
  35
  36 #include "stand.h"
  37
  38 #include <string.h>
  39
  40 static void     env_discard(struct env_var *ev);
  41
  42 struct env_var  *environ = NULL;
  43
  44 /*
  45  * Look up (name) and return it's env_var structure.
  46  */
  47 struct env_var  *
  48 env_getenv(const char *name)
  49 {
  50     struct env_var      *ev;
  51
  52     for (ev = environ; ev != NULL; ev = ev->ev_next)
  53         if (!strcmp(ev->ev_name, name))
  54             break;
  55     return(ev);
  56 }
  57
  58 /*
  59  * Some notes:
  60  *
  61  * If the EV_VOLATILE flag is set, a copy of the variable is made.
  62  * If EV_DYNAMIC is set, the variable has been allocated with
  63  * malloc and ownership transferred to the environment.
  64  * If (value) is NULL, the variable is set but has no value.
  65  */
  66 int
  67 env_setenv(const char *name, int flags, const void *value,
  68            ev_sethook_t sethook, ev_unsethook_t unsethook)
  69 {
  70     struct env_var      *ev, *curr, *last;
  71
  72     if ((ev = env_getenv(name)) != NULL) {
  73         /*
  74          * If there's a set hook, let it do the work (unless we are working
  75          * for one already.
  76          */
  77         if ((ev->ev_sethook != NULL) && !(flags & EV_NOHOOK))
  78             return (ev->ev_sethook(ev, flags, value));
  79
  80         /* If there is data in the variable, discard it. */
  81         if (ev->ev_value != NULL && (ev->ev_flags & EV_DYNAMIC) != 0)
  82             free(ev->ev_value);
  83         ev->ev_value = NULL;
  84         ev->ev_flags &= ~EV_DYNAMIC;
  85
  86     } else {
  87
  88         /*
  89          * New variable; create and sort into list
  90          */
  91         ev = malloc(sizeof(struct env_var));
  92         ev->ev_name = strdup(name);
  93         ev->ev_value = NULL;
  94         ev->ev_flags = 0;
  95         /* hooks can only be set when the variable is instantiated */
  96         ev->ev_sethook = sethook;
  97         ev->ev_unsethook = unsethook;
  98
  99         /* Sort into list */
 100         ev->ev_prev = NULL;
 101         ev->ev_next = NULL;
 102         /* Search for the record to insert before */
 103         for (last = NULL, curr = environ;
 104              curr != NULL;
 105              last = curr, curr = curr->ev_next) {
 106
 107             if (strcmp(ev->ev_name, curr->ev_name) < 0) {
 108                 if (curr->ev_prev) {
 109                     curr->ev_prev->ev_next = ev;
 110                 } else {
 111                     environ = ev;
 112                 }
 113                 ev->ev_next = curr;
 114                 ev->ev_prev = curr->ev_prev;
 115                 curr->ev_prev = ev;
 116                 break;
 117             }
 118         }
 119         if (curr == NULL) {
 120             if (last == NULL) {
 121                 environ = ev;
 122             } else {
 123                 last->ev_next = ev;
 124                 ev->ev_prev = last;
 125             }
 126         }
 127     }
 128
 129     /* If we have a new value, use it */
 130     if (flags & EV_VOLATILE) {
 131         ev->ev_value = strdup(value);
 132         ev->ev_flags |= EV_DYNAMIC;
 133     } else {
 134         ev->ev_value = (char *)value;
 135         ev->ev_flags |= flags & EV_DYNAMIC;
 136     }
 137
 138     return(0);
 139 }
 140
 141 char *
 142 getenv(const char *name)
 143 {
 144     struct env_var      *ev;
 145
 146     /* Set but no value gives empty string */
 147     if ((ev = env_getenv(name)) != NULL) {
 148         if (ev->ev_value != NULL)
 149             return(ev->ev_value);
 150         return("");
 151     }
 152     return(NULL);
 153 }
 154
 155 int
 156 setenv(const char *name, const char *value, int overwrite)
 157 {
 158     /* No guarantees about state, always assume volatile */
 159     if (overwrite || (env_getenv(name) == NULL))
 160         return(env_setenv(name, EV_VOLATILE, value, NULL, NULL));
 161     return(0);
 162 }
 163
 164 int
 165 putenv(const char *string)
 166 {
 167     char        *value, *copy;
 168     int         result;
 169
 170     copy = strdup(string);
 171     if ((value = strchr(copy, '=')) != NULL)
 172         *(value++) = 0;
 173     result = setenv(copy, value, 1);
 174     free(copy);
 175     return(result);
 176 }
 177
 178 int
 179 unsetenv(const char *name)
 180 {
 181     struct env_var      *ev;
 182     int                 err;
 183
 184     err = 0;
 185     if ((ev = env_getenv(name)) == NULL) {
 186         err = ENOENT;
 187     } else {
 188         if (ev->ev_unsethook != NULL)
 189             err = ev->ev_unsethook(ev);
 190         if (err == 0) {
 191             env_discard(ev);
 192         }
 193     }
 194     return(err);
 195 }
 196
 197 static void
 198 env_discard(struct env_var *ev)
 199 {
 200     if (ev->ev_prev)
 201         ev->ev_prev->ev_next = ev->ev_next;
 202     if (ev->ev_next)
 203         ev->ev_next->ev_prev = ev->ev_prev;
 204     if (environ == ev)
 205         environ = ev->ev_next;
 206     free(ev->ev_name);
 207     if (ev->ev_value != NULL && (ev->ev_flags & EV_DYNAMIC) != 0)
 208         free(ev->ev_value);
 209     free(ev);
 210 }
 211
 212 int
 213 env_noset(struct env_var *ev __unused, int flags __unused,
 214     const void *value __unused)
 215 {
 216     return(EPERM);
 217 }
 218
 219 int
 220 env_nounset(struct env_var *ev __unused)
 221 {
 222     return(EPERM);
 223 }