#ident "@(#)setenv.c 1.4"
/*
 * Copyright (c) 1987, 1988, 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

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

/*
 * __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.
 */
__inline static char *
__findenv (const char *name, int *offset)
{
	extern char **environ;
	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)
		continue;
	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);
}


#ifdef NEED_GETENV
/*
 * getenv --
 *      Returns ptr to value associated with name, if any, else NULL.
 */
char *
getenv (const char *name)
{
	int offset;

	return (__findenv (name, &offset));
}
#endif /* NEED_GETENV */


/* i see some os's have putenv but not setenv? */
#ifdef NEED_PUTENV
int 
putenv (const char *str)
{
	char *p, *equal;
	int rval;

	if ((p = strdup ((char *) str)) == NULL)
		return (-1);
	if ((equal = index (p, '=')) == NULL)
	{
		(void) free (p);
		return (-1);
	}
	*equal = '\0';
	rval = setenv (p, equal + 1, 1);
	(void) free (p);
	return (rval);
}
#endif /* NEED_PUTENV */

/*
 * 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)
{
	extern char **environ;
	static int alloced;	/* if allocated space before */
	register char *c;
	int l_value, offset;

	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 */
			environ = (char **) realloc ((char *) environ,
				    (size_t) (sizeof (char *) * (cnt + 2)));
			if (!environ)
				return (-1);
		}
		else
		{		/* get new space */
			alloced = 1;	/* copy old entries into it */
			p = malloc ((size_t) (sizeof (char *) * (cnt + 2)));
			if (!p)
				return (-1);
			memcpy (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);
}

/*
 * unsetenv(name) --
 *      Delete environmental variable "name".
 */
void 
unsetenv (const char *name)
{
	extern char **environ;
	register char **p;
	int offset;

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