Simple hex + ASCII dump

hexdump.c

void hexdump(const void* data, size_t size) {
  size_t j;
  size_t i;
  #define nexti (i + 1)

  const uint8_t wrap = 16;
  char ascii[wrap + 1];
  memset(ascii, 0, sizeof(ascii));

  for (i = 0; i < size; ++i) {
    printf("%02X ", ((uint8_t *)data)[i]);

    if (((uint8_t *)data)[i] >= ' ' && ((uint8_t *)data)[i] <= '~') {
      ascii[i % wrap] = ((uint8_t *)data)[i];
    } 
    else {
      ascii[i % wrap] = '.';
    }

    if (nexti % 8 == 0 || nexti == size) {
      printf(" ");

      if (nexti % wrap == 0) {
        printf("| %-*s |\n", wrap, ascii);
      } 
      else if (nexti == size) {
        ascii[nexti % wrap] = '\0';
        if (nexti % wrap <= 8) {
          printf(" ");
        }
        for (j = nexti % wrap; j < wrap; ++j) {
          printf("   ");
        }
        printf("| %-*s |\n", wrap, ascii);
      }
    }
  }
}