Untitled

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

void add32(uint16_t ah, uint16_t al, uint16_t *rh, uint16_t *rl)
{
	uint16_t bh, bl;
	int c = 0;

	bh = *rh;
	bl = *rl;

	*rl = al + bl;
	if (*rl < al || *rl < bl)
		c = 1;

	*rh = ah + bh + c;
}

void mul32(uint16_t ah, uint16_t al, uint16_t *rh, uint16_t *rl)
{
	uint16_t bh, bl;
	int i;

	bh = *rh;
	bl = *rl;

	*rh = 0;
	*rl = 0;

	for (i = 0; i < 16; i++) {
		if (bl & 1)
			add32(ah, al, rh, rl);

		ah <<= 1;
		if (al & 0x8000)
			ah |= 1;
		al <<= 1;

		bl >>= 1;
	}

	for (i = 0; i < 16; i++) {
		if (bh & 1)
			add32(ah, al, rh, rl);

		ah <<= 1;
		if (al & 0x8000)
			ah |= 1;
		al <<= 1;

		bh >>= 1;
	}
}

int main(int argc, char **argv)
{
	uint32_t a, b, r;
	uint16_t ah, al, bh, bl;

	a = strtoul(argv[1], NULL, 0);
	b = strtoul(argv[2], NULL, 0);

	ah = (a >> 16) & 0xFFFF;
	al = (a & 0xFFFF);
	bh = (b >> 16) & 0xFFFF;
	bl = (b & 0xFFFF);

#if 0
	add32(ah, al, &bh, &bl);
	r = ((uint32_t)bh << 16) | bl;

	if (!strncmp(argv[1], "0x", 2) || !strncmp(argv[2], "0x", 2))
		printf("0x%08x ?= 0x%08x\n", a + b, r);
	else
		printf("%d ?= %d", a + b, r);
#else
	mul32(ah, al, &bh, &bl);
	r = ((uint32_t)bh << 16) | bl;

	if (!strncmp(argv[1], "0x", 2) || !strncmp(argv[2], "0x", 2))
		printf("0x%08x ?= 0x%08x\n", a * b, r);
	else
		printf("%d ?= %d\n", a * b, r);
#endif

	return 0;
}