/*	$NetBSD: setenv.c,v 1.44 2015/01/20 18:31:25 christos Exp $	*/

/*
 * Copyright (c) 1987, 1993
 *	The 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 <sys/cdefs.h>
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include "env.h"
#include "local.h"

/*
 * setenv --
 *	Set the value of the environmental variable "name" to be
 *	"value".  If rewrite is set, replace any current value.
 */
int setenv(const char *name, const char *value, int rewrite) {
  size_t l_name, l_value, length;
  ssize_t offset;
  char *envvar;

  _DIAGASSERT(name != NULL);
  _DIAGASSERT(value != NULL);

  l_name = __envvarnamelen(name, false);
  if (l_name == 0 || value == NULL) {
    errno = EINVAL;
    return -1;
  }

  if (!__writelockenv())
    return -1;

  /* Find slot in the enviroment. */
  offset = __getenvslot(name, l_name, true);
  if (offset == -1)
    goto bad;

  l_value = strlen(value);
  length = l_name + l_value + 2;

  /* Handle overwriting a current environt variable. */
  envvar = environ[offset];
  if (envvar != NULL) {
    if (!rewrite)
      goto good;
    /*
     * Check whether the buffer was allocated via setenv(3) and
     * whether there is enough space. If so simply overwrite the
     * existing value.
     */
    if (__canoverwriteenvvar(envvar, length)) {
      envvar += l_name + 1;
      goto copy;
    }
  }

  /* Allocate memory for name + `=' + value + NUL. */
  if ((envvar = __allocenvvar(length)) == NULL)
    goto bad;

  if (environ[offset] != NULL)
    __freeenvvar(environ[offset]);

  environ[offset] = envvar;

  (void)memcpy(envvar, name, l_name);

  envvar += l_name;
  *envvar++ = '=';

copy:
  (void)memcpy(envvar, value, l_value + 1);

good:
  (void)__unlockenv();
  return 0;

bad:
  (void)__unlockenv();
  return -1;
}
