bits.c

/*
 * bits - pretty-print bits from a hex/dec/oct input
 *
 * cc -ansi -pedantic -Wall -o bits bits.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <stdint.h>

#define BITSIZE(n)        (CHAR_BIT*sizeof(n))
#define BITVALUE(n, bit)  ((n & (1UL<<bit)) == 0 ? 0 : 1)
#define BITS_PER_LINE     (CHAR_BIT*2)
#define NUM_LINES(n)      (BITSIZE(n)*1.0/BITS_PER_LINE)

int main(int argc, char *argv[])
{
  uint32_t number;
  int bit, line, a, b;

  if (argc != 2) {
    fprintf(stderr, "bits - pretty print bits from a hex/dec/oct input\n\n");
    fprintf(stderr, "usage: bits number\n");
    return 0;
  }

  number = strtoul(argv[1], NULL, 0);

  printf("input:            %s\n", argv[1]);
  printf("decimal unsigned: %u\n", (int32_t)number);
  printf("decimal signed:   %d\n", number);
  printf("hex:              0x%08x\n", number);

  printf("binary:           0b");
  for (bit = BITSIZE(number); bit-- > 0; ) {
    printf("%u", BITVALUE(number, bit));
  }
  printf("\n");

  printf("bits:\n\n");
  for (line = 0; line < NUM_LINES(number); line++) {
    a = BITSIZE(number) - (line*BITS_PER_LINE);
    b = a - BITS_PER_LINE;
    b = b < 0 ? 0 : b;

    for (bit = a; bit-- > b; ) {
      printf("%3u", bit);
    }
    printf("\n");

    for (bit = a; bit-- > b; ) {
      printf("%3u", BITVALUE(number, bit));
    }
    printf("\n\n");
  }

  return 0;
}