#include <string.h>

char *strtok(char * restrict new_s, char const * restrict separators)
{
	static char *s = NULL;
	if(new_s) s = new_s;

	/* Skip leading delimiters */
	s += strspn(s, separators);
	if(!*s) return NULL;

	/* Skip non-delimiters */
	char *token = s;
	s += strcspn(s, separators);
	if(*s) *s++ = 0;

	return token;
}