kc3-lang/libtommath/s_mp_mul_balance.c

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• Hash : 5c335f84
  Author :
  Date : 2019-10-30T17:26:27
  

  rename mul/sqr functions for consistency, comba instead of fast suffix

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• s_mp_mul_balance.c

• #include "tommath_private.h"
  #ifdef S_MP_MUL_BALANCE_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* single-digit multiplication with the smaller number as the single-digit */
  mp_err s_mp_mul_balance(const mp_int *a, const mp_int *b, mp_int *c)
  {
     mp_int a0, tmp, r;
     mp_err err;
     int i, j,
         nblocks = MP_MAX(a->used, b->used) / MP_MIN(a->used, b->used),
         bsize = MP_MIN(a->used, b->used);
  
     if ((err = mp_init_size(&a0, bsize + 2)) != MP_OKAY) {
        return err;
     }
     if ((err = mp_init_multi(&tmp, &r, NULL)) != MP_OKAY) {
        mp_clear(&a0);
        return err;
     }
  
     /* Make sure that A is the larger one*/
     if (a->used < b->used) {
        MP_EXCH(const mp_int *, a, b);
     }
  
     for (i = 0, j=0; i < nblocks; i++) {
        /* Cut a slice off of a */
        a0.used = bsize;
        s_mp_copy_digs(a0.dp, a->dp + j, a0.used);
        j += a0.used;
        mp_clamp(&a0);
  
        /* Multiply with b */
        if ((err = mp_mul(&a0, b, &tmp)) != MP_OKAY) {
           goto LBL_ERR;
        }
        /* Shift tmp to the correct position */
        if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
           goto LBL_ERR;
        }
        /* Add to output. No carry needed */
        if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) {
           goto LBL_ERR;
        }
     }
     /* The left-overs; there are always left-overs */
     if (j < a->used) {
        a0.used = a->used - j;
        s_mp_copy_digs(a0.dp, a->dp + j, a0.used);
        j += a0.used;
        mp_clamp(&a0);
  
        if ((err = mp_mul(&a0, b, &tmp)) != MP_OKAY) {
           goto LBL_ERR;
        }
        if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
           goto LBL_ERR;
        }
        if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) {
           goto LBL_ERR;
        }
     }
  
     mp_exch(&r,c);
  LBL_ERR:
     mp_clear_multi(&a0, &tmp, &r,NULL);
     return err;
  }
  #endif
  

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