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NULL vs '\0'

/*	$OpenBSD: env.c,v 1.9 2001/02/18 20:17:20 millert Exp $	*/
/* Copyright 1988,1990,1993,1994 by Paul Vixie
 * All rights reserved
 */

/*
 * Copyright (c) 1997,2000 by Internet Software Consortium, Inc.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

#if !defined(lint) && !defined(LINT)
static char rcsid[] = "$OpenBSD: env.c,v 1.9 2001/02/18 20:17:20 millert Exp $";
#endif


#include "cron.h"


char **
env_init()
{
	char	**p = (char **) malloc(sizeof(char **));

	if (p != NULL)
		p[0] = NULL;
	return (p);
}


void
env_free(envp)
	char	**envp;
{
	char	**p;

	for (p = envp;  *p;  p++)
		free(*p);
	free(envp);
}


char **
env_copy(envp)
	char	**envp;
{
	int	count, i, save_errno;
	char	**p;

	for (count = 0;  envp[count] != NULL;  count++)
		;
	p = (char **) malloc((count+1) * sizeof(char *));  /* 1 for the NULL */
	if (p != NULL) {
		for (i = 0;  i < count;  i++)
			if ((p[i] = strdup(envp[i])) == NULL) {
				save_errno = errno;
				while (--i >= 0)
					free(p[i]);
				free(p);
				errno = save_errno;
				return (NULL);
			}
		p[count] = NULL;
	}
	return (p);
}


char **
env_set(envp, envstr)
	char	**envp;
	char	*envstr;
{
	int	count, found;
	char	**p, *cp;

	/*
	 * count the number of elements, including the null pointer;
	 * also set 'found' to -1 or index of entry if already in here.
	 */
	found = -1;
	for (count = 0;  envp[count] != NULL;  count++) {
		if (!strcmp_until(envp[count], envstr, '='))
			found = count;
	}
	count++;	/* for the NULL */

	if (found != -1) {
		/*
		 * it exists already, so just free the existing setting,
		 * save our new one there, and return the existing array.
		 */
		free(envp[found]);
		if ((envp[found] = strdup(envstr)) == NULL) {
			envp[found] = "";
			return (NULL);
		}
		return (envp);
	}

	/*
	 * it doesn't exist yet, so resize the array, move null pointer over
	 * one, save our string over the old null pointer, and return resized
	 * array.
	 */
	p = (char **) realloc((void *) envp,
			      (size_t) ((count+1) * sizeof(char **)));
	if (p == NULL)
		return (NULL);
	cp = strdup(envstr);
	if (cp == NULL)
		return(NULL);
	p[count] = p[count-1];
	p[count-1] = cp;
	return (p);
}


/* return	ERR = end of file
 *		FALSE = not an env setting (file was repositioned)
 *		TRUE = was an env setting
 */
int
load_env(envstr, f)
	char	*envstr;
	FILE	*f;
{
	long	filepos;
	int	fileline;
	char	name[MAX_ENVSTR], val[MAX_ENVSTR];
	int	fields;

	filepos = ftell(f);
	fileline = LineNumber;
	skip_comments(f);
	if (EOF == get_string(envstr, MAX_ENVSTR, f, "\n"))
		return (ERR);

	Debug(DPARS, ("load_env, read <%s>\n", envstr))

	name[0] = val[0] = '\0';
	fields = sscanf(envstr, "%[^ =] = %[^\n#]", name, val);
	if (fields != 2) {
		Debug(DPARS, ("load_env, not 2 fields (%d)\n", fields))
		fseek(f, filepos, 0);
		Set_LineNum(fileline);
		return (FALSE);
	}

	/*
	 * 2 fields from scanf; looks like an env setting.
	 */

	/*
	 * process value string
	 */
	/*local*/{
		int	len = strdtb(val);

		if (len >= 2) {
			if (val[0] == '\'' || val[0] == '"') {
				if (val[len-1] == val[0]) {
					val[len-1] = '\0';
					memmove(val, val+1, len);
				}
			}
		}
	}

	/*
	 * This can't overflow because get_string() limited the size of the
	 * name and val fields.  Still, it doesn't hurt...
	 */
	(void) snprintf(envstr, MAX_ENVSTR, "%s=%s", name, val);
	Debug(DPARS, ("load_env, <%s> <%s> -> <%s>\n", name, val, envstr))
	return (TRUE);
}


char *
env_get(name, envp)
	char	*name;
	char	**envp;
{
	int	len = strlen(name);
	char	*p, *q;

	while ((p = *envp++) != NULL) {
		if (!(q = strchr(p, '=')))
			continue;
		if ((q - p) == len && !strncmp(p, name, len))
			return (q+1);
	}
	return (NULL);
}