fizzbuzz_direct_threaded.c

#include <stdio.h>
#include <stdint.h>

#define MAX 100

int
main(int argc, char **argv)
{
	intptr_t op[MAX + 2];
	int ip;

	void *compile_ops[8] = {
		[0]       = &&op_print,
		[1]       = &&op_fizz,
		[2]       = &&op_buzz,
		[3]       = &&op_fizzbuzz,
		[4 ... 7] = &&op_done
	};

	for (ip = 0; ip < MAX + 2; ip++)
		op[ip] = (intptr_t) compile_ops[
			   (!(ip % 3))
			| ((!(ip % 5))  << 1)
			|   ((ip > MAX) << 2)
		];

	ip = 0;

#define NEXT goto *op[++ip]

op_print:    printf("%d\n", ip); NEXT;
op_fizz:     puts("fizz");       NEXT;
op_buzz:     puts("buzz");       NEXT;
op_fizzbuzz: puts("fizzbuzz");   NEXT;
op_done:
	return 0;
}