ack/lang/cem/libcc.ansi/stdlib/putenv.c

/*
 * (c) copyright 1989 by the Vrije Universiteit, Amsterdam, The Netherlands.
 * See the copyright notice in the ACK home directory, in the file "Copyright".
 */
/* $Id$ */

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

#define ENTRY_INC 10
#define rounded(x) (((x / ENTRY_INC) + 1) * ENTRY_INC)

extern char** environ;

int putenv(char* name)
{
	register char** v = environ;
	register char* r;
	static int size = 0;
	/* When size != 0, it contains the number of entries in the
	 * table (including the final NULL pointer). This means that the
	 * last non-null entry  is environ[size - 2].
	 */

	if (!name)
		return 0;
	if (r = strchr(name, '='))
	{
		register const char *p, *q;

		*r = '\0';

		if (v != NULL)
		{
			while ((p = *v) != NULL)
			{
				q = name;
				while (*q && (*q++ == *p++))
					/* EMPTY */;
				if (*q || (*p != '='))
				{
					v++;
				}
				else
				{
					/* The name was already in the
					 * environment.
					 */
					*r = '=';
					*v = name;
					return 0;
				}
			}
		}
		*r = '=';
		v = environ;
	}

	if (!size)
	{
		register char** p;
		register int i = 0;

		if (v)
			do
			{
				i++;
			} while (*v++);
		if (!(v = malloc(rounded(i) * sizeof(char**))))
			return 1;
		size = i;
		p = environ;
		environ = v;
		while (*v++ = *p++)
			; /* copy the environment */
		v = environ;
	}
	else if (!(size % ENTRY_INC))
	{
		if (!(v = realloc(environ, rounded(size) * sizeof(char**))))
			return 1;
		environ = v;
	}
	v[size - 1] = name;
	v[size] = NULL;
	size++;
	return 0;
}