SLRE: is_any_of() with escape character support

gistfile1.c

static int
is_any_of(const unsigned char *p, int len, const char *s, int *ofs)
{
	int	i, ch;

	ch = s[*ofs];

	for (i = 0; i < len; i++)
		if (p[i] == ch) {
			(*ofs)++;
			return (1);
		}
		else if (p[i] == 0)
		{
			if (   ((p[i + 1] == SPACE)    &&  isspace(ch) )
			    || ((p[i + 1] == NONSPACE) && !isspace(ch) )
			    || ((p[i + 1] == DIGIT)    &&  isdigit(ch) )
                            || ((p[i + 1] == '\0')     && (ch == '\0') )
			{
				(*ofs)++;
				return (1);
			}
			i++;
		}
	}

	return (0);
}