setbits.c

#include <stdio.h>

unsigned getbits(unsigned, int, int);
unsigned setbits(unsigned, int, int, unsigned);

int main(void)
{
  int n;
  int x, y;
  n = 58 ^ 20;
  n = 57 << 1;
  x = y = 64;
  /* printf("%d\n", 57 & 1 + 9); */
  /* printf("%d\n", 57 | 19); */
  /* printf("%d\n", 57 ^ 19); */
  /* printf("%d - right\n", 57 >> 2); */
  /* printf("%d\n", 57 << 2); */
  printf("%d\n", (~(~0 << 3)));
  printf("%u\n", setbits(x, 7, 3, y));
  printf("%d\n", x);
  printf("%d\n", y);

  return 0;
}

unsigned getbits(unsigned x, int p, int n)
{
  return (x >> (p + 1 - n)) & ~(~0 << n);
}

/* unsigned setbits(unsigned x, int p, int n, int y) */
/* { */
/*   return getbits(x, p, n) | y >> n; */
/* } */
unsigned setbits(unsigned x, int p, int n, unsigned y)
{
    return (x & ((~0 << (p+1)) | ~(~0 << (p+1-n)))) | ((y & ~(~0 << n)) << (p+1-n));
}