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setenv.c

/*
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdlib.h>
#include <string.h>

#include "config.h"
#if !defined(HAVE_SETENV) || !defined(HAVE_UNSETENV)

static char *__findenv(const char *name, int *offset);
#ifndef HAVE_SETENV
int setenv(const char *, const char *, int);
#endif
#ifndef HAVE_UNSETENV
void unsetenv(const char *);
#endif
extern char **environ;

/*
 * __findenv --
 *    Returns pointer to value associated with name, if any, else NULL.
 *    Sets offset to be the offset of the name/value combination in the
 *    environmental array, for use by setenv(3) and unsetenv(3).
 *    Explicitly removes '=' in argument name.
 *
 *    This routine *should* be a static; don't use it.
 */
static char *
__findenv(name, offset)
      register const char *name;
      int *offset;
{
      register int len, i;
      register const char *np;
      register char **p, *cp;

      if (name == NULL || environ == NULL)
            return (NULL);
      for (np = name; *np && *np != '='; ++np)
            ;
      len = np - name;
      for (p = environ; (cp = *p) != NULL; ++p) {
            for (np = name, i = len; i && *cp; i--)
                  if (*cp++ != *np++)
                        break;
            if (i == 0 && *cp++ == '=') {
                  *offset = p - environ;
                  return (cp);
            }
      }
      return (NULL);
}

#ifndef HAVE_SETENV
/*
 * setenv --
 *    Set the value of the environmental variable "name" to be
 *    "value".  If rewrite is set, replace any current value.
 */
int
setenv(name, value, rewrite)
      register const char *name;
      register const char *value;
      int rewrite;
{
      static int alloced;                 /* if allocated space before */
      register char *C;
      int offset;
      size_t l_value;

      if (*value == '=')                  /* no `=' in value */
            ++value;
      l_value = strlen(value);
      if ((C = __findenv(name, &offset))) {     /* find if already exists */
            if (!rewrite)
                  return (0);
            if (strlen(C) >= l_value) {   /* old larger; copy over */
                  while ((*C++ = *value++))
                        ;
                  return (0);
            }
      } else {                            /* create new slot */
            register int      cnt;
            register char     **P;

            for (P = environ, cnt = 0; *P; ++P, ++cnt);
            if (alloced) {                /* just increase size */
                  P = (char **)realloc((void *)environ,
                      (size_t)(sizeof(char *) * (cnt + 2)));
                  if (!P)
                        return (-1);
                  environ = P;
            }
            else {                        /* get new space */
                  alloced = 1;            /* copy old entries into it */
                  P = (char **)malloc((size_t)(sizeof(char *) *
                      (cnt + 2)));
                  if (!P)
                        return (-1);
                  memmove(P, environ, cnt * sizeof(char *));
                  environ = P;
            }
            environ[cnt + 1] = NULL;
            offset = cnt;
      }
      for (C = (char *)name; *C && *C != '='; ++C);   /* no `=' in name */
      if (!(environ[offset] =             /* name + `=' + value */
          malloc((size_t)((int)(C - name) + l_value + 2))))
            return (-1);
      for (C = environ[offset]; (*C = *name++) && *C != '='; ++C)
            ;
      for (*C++ = '='; (*C++ = *value++); )
            ;
      return (0);
}
#endif /* HAVE_SETENV */

#ifndef HAVE_UNSETENV
/*
 * unsetenv(name) --
 *    Delete environmental variable "name".
 */
void
unsetenv(name)
      const char  *name;
{
      register char **P;
      int offset;

      while (__findenv(name, &offset))          /* if set multiple times */
            for (P = &environ[offset];; ++P)
                  if (!(*P = *(P + 1)))
                        break;
}
#endif /* HAVE_UNSETENV */

#endif /* !defined(HAVE_SETENV) || !defined(HAVE_UNSETENV) */

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