Line data    Source code

       1             : #include "tommath_private.h"
       2             : #ifdef BN_S_MP_BALANCE_MUL_C
       3             : /* LibTomMath, multiple-precision integer library -- Tom St Denis */
       4             : /* SPDX-License-Identifier: Unlicense */
       5             : 
       6             : /* single-digit multiplication with the smaller number as the single-digit */
       7           0 : mp_err s_mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c)
       8             : {
       9           0 :    int count, len_a, len_b, nblocks, i, j, bsize;
      10           0 :    mp_int a0, tmp, A, B, r;
      11           0 :    mp_err err;
      12             : 
      13           0 :    len_a = a->used;
      14           0 :    len_b = b->used;
      15             : 
      16           0 :    nblocks = MP_MAX(a->used, b->used) / MP_MIN(a->used, b->used);
      17           0 :    bsize = MP_MIN(a->used, b->used) ;
      18             : 
      19           0 :    if ((err = mp_init_size(&a0, bsize + 2)) != MP_OKAY) {
      20           0 :       return err;
      21             :    }
      22           0 :    if ((err = mp_init_multi(&tmp, &r, NULL)) != MP_OKAY) {
      23           0 :       mp_clear(&a0);
      24           0 :       return err;
      25             :    }
      26             : 
      27             :    /* Make sure that A is the larger one*/
      28           0 :    if (len_a < len_b) {
      29           0 :       B = *a;
      30           0 :       A = *b;
      31             :    } else {
      32           0 :       A = *a;
      33           0 :       B = *b;
      34             :    }
      35             : 
      36           0 :    for (i = 0, j=0; i < nblocks; i++) {
      37             :       /* Cut a slice off of a */
      38           0 :       a0.used = 0;
      39           0 :       for (count = 0; count < bsize; count++) {
      40           0 :          a0.dp[count] = A.dp[ j++ ];
      41           0 :          a0.used++;
      42             :       }
      43           0 :       mp_clamp(&a0);
      44             :       /* Multiply with b */
      45           0 :       if ((err = mp_mul(&a0, &B, &tmp)) != MP_OKAY) {
      46           0 :          goto LBL_ERR;
      47             :       }
      48             :       /* Shift tmp to the correct position */
      49           0 :       if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
      50           0 :          goto LBL_ERR;
      51             :       }
      52             :       /* Add to output. No carry needed */
      53           0 :       if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) {
      54           0 :          goto LBL_ERR;
      55             :       }
      56             :    }
      57             :    /* The left-overs; there are always left-overs */
      58           0 :    if (j < A.used) {
      59           0 :       a0.used = 0;
      60           0 :       for (count = 0; j < A.used; count++) {
      61           0 :          a0.dp[count] = A.dp[ j++ ];
      62           0 :          a0.used++;
      63             :       }
      64           0 :       mp_clamp(&a0);
      65           0 :       if ((err = mp_mul(&a0, &B, &tmp)) != MP_OKAY) {
      66           0 :          goto LBL_ERR;
      67             :       }
      68           0 :       if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
      69           0 :          goto LBL_ERR;
      70             :       }
      71           0 :       if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) {
      72           0 :          goto LBL_ERR;
      73             :       }
      74             :    }
      75             : 
      76           0 :    mp_exch(&r,c);
      77           0 : LBL_ERR:
      78           0 :    mp_clear_multi(&a0, &tmp, &r,NULL);
      79           0 :    return err;
      80             : }
      81             : #endif