/*
 * 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. 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.
 */

#include <config/have_setenv.h>

#ifndef HAVE_SETENV

#include <sys/types.h>

#include "setenv.h"

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

static char	*findenv(const char *, int *);

/*
 * 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.
 */
static char *
findenv(const char *name, int *offset)
{
	extern char **environ;
	int len, i;
	const char *np;
	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);
}

/*
 * 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 */
	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 */
		int cnt;
		char **P;

		for (P = environ, cnt = 0; *P; ++P, ++cnt);
		if (alloced) {			/* just increase size */
			P = realloc((void *)environ,
			    (size_t)(sizeof(char *) * (cnt + 2)));
			if (P == NULL)
				return (-1);
			environ = P;
		} else {			/* get new space */
			alloced = 1;		/* copy old entries into it */
			P = malloc((size_t)(sizeof(char *) * (cnt + 2)));
			if (P == NULL)
				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))) == NULL)
		return (-1);
	for (C = environ[offset]; (*C = *name++) && *C != '='; ++C)
		;
	for (*C++ = '='; (*C++ = *value++); )
		;
	return (0);
}

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

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

#endif /* HAVE_SETENV */