inspired by hexcmp, bitcmp is a tool to view `cmp -l` output in bitwise form

bitcmp.c

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

/*
 * E.g.,
 * cmp -l <(dd if=/dev/urandom count=1) \
 *        <(dd if=/dev/urandom count=1) \
 *        | bitcmp -o
 */

int main(int argc, char *argv[]) {
  int value_base = 10;
  int offset_base = 10;
  bool inverse = false;

  for (int opt; (opt = getopt(argc, argv, "oOxXv")) != -1;) {
    switch (opt) {
      case 'o':
        value_base = 8;
        break;
      case 'O':
        offset_base = 8;
        break;
      case 'x':
        value_base = 16;
        break;
      case 'X':
        offset_base = 16;
        break;
      case 'v':
        inverse = true;
        break;
      default:
        fprintf(stderr, "usage: %s [OPTION]...\n", argv[0]);
        exit(EXIT_FAILURE);
    }
  }

  for (char buf[256]; fgets(buf, sizeof(buf), stdin);) {
    char offsetstr[16], leftstr[16], rightstr[16];
    if (sscanf(buf, "%s %s %s", offsetstr, leftstr, rightstr) != 3) {
      fprintf(stderr, "unexpected input: %s\n", buf);
      continue;
    }

    int offset = strtol(offsetstr, NULL, offset_base);
    int left = strtol(leftstr, NULL, value_base);
    int right = strtol(rightstr, NULL, value_base);

    if (inverse) {
      int tmp = right;
      right = left;
      left = tmp;
    }

    if (left < 0 || left > 0xFF || right < 0 || right > 0xFF) {
      fprintf(stderr, "unexpected input: %s\n", buf);
      continue;
    }

    int diff = left ^ right;

    char oct[9] = {'.', '.', '.', '.', '.', '.', '.', '.', '\0'};

    for (int i = 0; i < 8; i++) {
      if ((diff >> i) & 1) {
        oct[7 - i] = (left >> i) & 1 ? '0' : '1';
      }
    }

    printf("0x%08X %s\n", offset, oct);
  }

  exit(EXIT_SUCCESS);
}