Emulating a hardware signed multiplier

[Børge Strand-Bergesen]

Pedro,

most elegant. Thank you!

Your predictions are right. I did a quick check. My FPGA interface
prefers capital-letter hex without preceding 0x. And that prints
beautifully. However, the %#016Zx drops "0x" at offset==0 and seems to
use two less characters at offset>0. I assume this is a printf issue.
The issue won't bother my application but I wouldn't mind knowing how
to make it print correctly.

Regards,
Borge


int main(void) {
	mpz_t a, mask64, a_fpga;
	int8_t offset;

	mpz_init(a);
	mpz_init_set_str(mask64, "FFFFFFFFFFFFFFFF", 16);
	mpz_init(a_fpga);

	for (offset=-10; offset<11; offset++) {
		mpz_set_si(a, offset);
		mpz_and(a_fpga, a, mask64);
		gmp_printf("%3d, %016ZX, %#016Zx\n", offset, a_fpga, a_fpga); //
FPGA interface uses capital hex and no "0x"
	}
	
/* Prints:
-10, FFFFFFFFFFFFFFF6, 0xfffffffffffffff6
 -9, FFFFFFFFFFFFFFF7, 0xfffffffffffffff7
 -8, FFFFFFFFFFFFFFF8, 0xfffffffffffffff8
 -7, FFFFFFFFFFFFFFF9, 0xfffffffffffffff9
 -6, FFFFFFFFFFFFFFFA, 0xfffffffffffffffa
 -5, FFFFFFFFFFFFFFFB, 0xfffffffffffffffb
 -4, FFFFFFFFFFFFFFFC, 0xfffffffffffffffc
 -3, FFFFFFFFFFFFFFFD, 0xfffffffffffffffd
 -2, FFFFFFFFFFFFFFFE, 0xfffffffffffffffe
 -1, FFFFFFFFFFFFFFFF, 0xffffffffffffffff
  0, 0000000000000000, 0000000000000000
  1, 0000000000000001, 0x00000000000001
  2, 0000000000000002, 0x00000000000002
  3, 0000000000000003, 0x00000000000003
  4, 0000000000000004, 0x00000000000004
  5, 0000000000000005, 0x00000000000005
  6, 0000000000000006, 0x00000000000006
  7, 0000000000000007, 0x00000000000007
  8, 0000000000000008, 0x00000000000008
  9, 0000000000000009, 0x00000000000009
 10, 000000000000000A, 0x0000000000000a
*/

}