lib/hcrypto/libtommath/bn_mp_reduce_is_2k.c

   1 #include "tommath_private.h"
   2 #ifdef BN_MP_REDUCE_IS_2K_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
   4 /* SPDX-License-Identifier: Unlicense */
   5
   6 /* determines if mp_reduce_2k can be used */
   7 mp_bool mp_reduce_is_2k(const mp_int *a)
   8 {
   9    int ix, iy, iw;
  10    mp_digit iz;
  11
  12    if (a->used == 0) {
  13       return MP_NO;
  14    } else if (a->used == 1) {
  15       return MP_YES;
  16    } else if (a->used > 1) {
  17       iy = mp_count_bits(a);
  18       iz = 1;
  19       iw = 1;
  20
  21       /* Test every bit from the second digit up, must be 1 */
  22       for (ix = MP_DIGIT_BIT; ix < iy; ix++) {
  23          if ((a->dp[iw] & iz) == 0u) {
  24             return MP_NO;
  25          }
  26          iz <<= 1;
  27          if (iz > MP_DIGIT_MAX) {
  28             ++iw;
  29             iz = 1;
  30          }
  31       }
  32       return MP_YES;
  33    } else {
  34       return MP_YES;
  35    }
  36 }
  37
  38 #endif