crypto/external/bsd/heimdal/dist/lib/hcrypto/libtommath/bn_mp_mul.c

   1 /*      $NetBSD: bn_mp_mul.c,v 1.1.1.2 2014/04/24 12:45:31 pettai Exp $ */
   2
   3 #include <tommath.h>
   4 #ifdef BN_MP_MUL_C
   5 /* LibTomMath, multiple-precision integer library -- Tom St Denis
   6  *
   7  * LibTomMath is a library that provides multiple-precision
   8  * integer arithmetic as well as number theoretic functionality.
   9  *
  10  * The library was designed directly after the MPI library by
  11  * Michael Fromberger but has been written from scratch with
  12  * additional optimizations in place.
  13  *
  14  * The library is free for all purposes without any express
  15  * guarantee it works.
  16  *
  17  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
  18  */
  19
  20 /* high level multiplication (handles sign) */
  21 int mp_mul (mp_int * a, mp_int * b, mp_int * c)
  22 {
  23   int     res, neg;
  24   neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
  25
  26   /* use Toom-Cook? */
  27 #ifdef BN_MP_TOOM_MUL_C
  28   if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) {
  29     res = mp_toom_mul(a, b, c);
  30   } else
  31 #endif
  32 #ifdef BN_MP_KARATSUBA_MUL_C
  33   /* use Karatsuba? */
  34   if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
  35     res = mp_karatsuba_mul (a, b, c);
  36   } else
  37 #endif
  38   {
  39     /* can we use the fast multiplier?
  40      *
  41      * The fast multiplier can be used if the output will
  42      * have less than MP_WARRAY digits and the number of
  43      * digits won't affect carry propagation
  44      */
  45     int     digs = a->used + b->used + 1;
  46
  47 #ifdef BN_FAST_S_MP_MUL_DIGS_C
  48     if ((digs < MP_WARRAY) &&
  49         MIN(a->used, b->used) <=
  50         (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) {
  51       res = fast_s_mp_mul_digs (a, b, c, digs);
  52     } else
  53 #endif
  54 #ifdef BN_S_MP_MUL_DIGS_C
  55       res = s_mp_mul (a, b, c); /* uses s_mp_mul_digs */
  56 #else
  57       res = MP_VAL;
  58 #endif
  59
  60   }
  61   c->sign = (c->used > 0) ? neg : MP_ZPOS;
  62   return res;
  63 }
  64 #endif
  65
  66 /* Source: /cvs/libtom/libtommath/bn_mp_mul.c,v  */
  67 /* Revision: 1.4  */
  68 /* Date: 2006/12/28 01:25:13  */