/* locals */
static unsigned int crc_table[256];


/* ----
 * crc_init()
 * ----
 */

void
crc_init(void)
{
  int i;
  unsigned int t, *p, *q;
  unsigned int poly = 0x864CFB;

  p = q = crc_table;
  *q++ = 0;
  *q++ = poly;

  for (i = 1; i < 128; i++) {
    t = *(++p);
    if (t & 0x800000) {
      t <<= 1;
      *q++ = t ^ poly;
      *q++ = t;
    }
    else {
      t <<= 1;
      *q++ = t;
      *q++ = t ^ poly;
    }
  }
}


/* ----
 * crc_calc()
 * ----
 * 24-bit crc
 */

unsigned int
crc_calc(unsigned char *data, int len)
{
  unsigned int crc = 0;
  int i;

  for (i = 0; i < len; i++)
    crc = (crc << 8) ^ crc_table[(unsigned char)(crc >> 16) ^ *data++];

  /* ok */
  return (crc & 0xFFFFFF);
}