/* shift2.c

 * Inputs:
 *   - direction:  shift left (0) or right (else)
 *   - number:     shift amount (number of bits)
 */
#include <stdio.h>
#include <stdlib.h>

void print_binary(unsigned char number, int size)
{
  if (!number)
  {
    putc('0', stdout);
    return;
  }
  if (size == 1)
  {
    putc((number & 1) ? '1' : '0', stdout);
    return;
  }
  print_binary(number >> 1, size - 1);
  putc((number & 1) ? '1' : '0', stdout);
}

int main(int argc, char *argv[])
{
  unsigned char dir, num, pos;

  // Want two arguments, but executable name is always argv[0]
  if (argc != 4)
  {
    printf("Usage:  ./shift2 <direction> <number> <pos> \n");
    printf("        direction: shift left (0) or right (1)\n");
    printf("        number:    shift amount (number of bits)\n");
    return 1;
  }

  // atoi() converts strings to integers
  dir = atoi(argv[1]);
  num = (int)strtol(argv[2], NULL, 16);
  pos = atoi(argv[3]);

  if (dir) // shift right
  {
    print_binary(num, sizeof(num) * 8);
    printf(" >> %d = ", pos);
    print_binary(num >> pos, sizeof(num) * 8);
    printf("\n");
    // printf("%x >> %x = %x\n", num, pos, num >> pos);
  }
  else
  { // shift left
    print_binary(num, sizeof(num) * 8);
    printf(" << %d = ", pos);
    print_binary(num << pos, sizeof(num) * 8);
    printf("\n");
    // printf("%x << %x = %x\n", num, pos, num << pos);
  }
  return 0;
}