-/* ========================================================================
- * Routines used for CRC calculation. Some are also required for the table
- * generation above.
- */
-
-/*
- Return a(x) multiplied by b(x) modulo p(x), where p(x) is the CRC polynomial,
- reflected. For speed, this requires that a not be zero.
- */
-local z_crc_t multmodp(a, b)
- z_crc_t a;
- z_crc_t b;
-{
- z_crc_t m, p;
-
- m = (z_crc_t)1 << 31;
- p = 0;
- for (;;) {
- if (a & m) {
- p ^= b;
- if ((a & (m - 1)) == 0)
- break;
- }
- m >>= 1;
- b = b & 1 ? (b >> 1) ^ POLY : b >> 1;
- }
- return p;
-}
-
-/*
- Return x^(n * 2^k) modulo p(x). Requires that x2n_table[] has been
- initialized.
- */
-local z_crc_t x2nmodp(n, k)
- z_off64_t n;
- unsigned k;
-{
- z_crc_t p;
-
- p = (z_crc_t)1 << 31; /* x^0 == 1 */
- while (n) {
- if (n & 1)
- p = multmodp(x2n_table[k & 31], p);
- n >>= 1;
- k++;
- }
- return p;
-}
-