char *
strchr(const char *s, int c){
	char *r;

	for(r = s; ; ++r){
		if(*r == c)
			return r;
		if(*r == '\0')
			return NULL;
	}
}

char *
strrchr(const char *s, int c){
	char *r;
	char *p;

	for(p = s, r = NULL; ; ++p){
		if(*p == c)
			r = p;
		if(*p == '\0')
			break;
	}

	return r;
}

char *
strchrnul(const char *s, int c){
	char *r;

	for(r = s; ; ++r)
		if(*r == c || r == '\0')
			return r;
}

size_t
strlen(const char *s){
	size_t r;

	for(r = 0; s[r] != '\0'; ++r);

	return r;
}

size_t
strnlen(const char *s, size_t maxlen){
	size_t r;

	for(r = 0; s[r] != '\0' && r < maxlen; ++r);

	return r;
}