/*      $OpenBSD: getenv.c,v 1.13 2024/07/10 14:17:58 jca 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 <stdlib.h>
#include <string.h>


/*
 * __findenv --
 *      Returns pointer to value associated with name, if any, else NULL.
 *      Starts searching within the environmental array at offset.
 *      Sets offset to be the offset of the name/value combination in the
 *      environmental array, for use by putenv(3), setenv(3) and unsetenv(3).
 *      Explicitly removes '=' in argument name.
 */
char *
__findenv(const char *name, int len, int *offset)
{
        int i;
        const char *np;
        char **p, *cp;

        if (name == NULL || environ == NULL)
                return (NULL);
        for (p = environ + *offset; (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);
}

/*
 * getenv --
 *      Returns ptr to value associated with name, if any, else NULL.
 */
char *
getenv(const char *name)
{
        int offset = 0;
        const char *np;

        for (np = name; *np && *np != '='; ++np)
                ;
        return (__findenv(name, (int)(np - name), &offset));
}
DEF_STRONG(getenv);