#include <stdio.h>
#include <stdlib.h>
#include "02-bitwise.h"

unsigned setbits(unsigned x, int p, int n, unsigned y);

/* parse command line args for setbits, print result */
int main(int argc, char *argv[])
{
    if (argc < 5) {
        printf("error : expected 4 arguments x p n y\n");
        return 1;
    }
    unsigned x, y;
    int bx = int_of_string(&x, argv[1]);
    int p  = atoi(argv[2]);
    int n  = atoi(argv[3]);
    int by = int_of_string(&y, argv[4]);

    if (!bx || !by) {
        return 2;
    }

    printd_base(bx, setbits(x, p, n, y));
    putchar('\n');
    return 0;
}

/* setbits: replace n bits in position p (right adjusted) in
 * x with the rightmost n bits of y, return the result */
unsigned setbits(unsigned x, int p, int n, unsigned y)
{
    unsigned mask = ~(~0 << n);
    return ((y & mask) << (p+1-n)) | (x & ~(mask << (p+1-n)));
}