#include <stdio.h>
#include <assert.h>
/**
* @param s - Signal to match the filter, any value
* @param f - The filter itself, 0 or 1
* @returns s if f == 1, 0 otherwise
*/
signed int filter(signed int s, unsigned char f)
{
assert(sizeof(s) == 4);
assert(0 <= f <= 1);
signed int A = f * 0x80000000;
unsigned char B = f;
signed char C = s >> 31;
signed int D = s & 0x7FFFFFFF;
signed int
x = A,
y = (A+B+C == 0x80000000) ? (A+B+C) : 0,
z = (A+D < 0) ? (A+D) : 0;
signed int res = x+y+z;
printf("==============\n");
printf("filter(%i, %d):\n", s, f);
printf("> A = %d * 0x80000000 // == %i\n", f, A);
printf("> B = %d\n", B);
printf("> C = %i >> 31 // == %d\n", s, C);
printf("> D = %i & 0x7FFFFFFF // == %i\n", s, D);
printf(">> x = %i\n", x);
printf(">> y = %i\n", y);
printf(">> z = %i\n", z);
printf(">>> res = %i\n", res);
printf("filter(%i, %d) == %i\n", s, f, res);
printf("==============\n");
printf("\n");
return res;
}
int main()
{
filter(42, 0);
filter(42, 1);
filter(-625, 0);
filter(-625, 1);
return 0;
}
