1 #include <tommath.h> 2 #ifdef BN_MP_MUL_C 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis 4 * 5 * LibTomMath is a library that provides multiple-precision 6 * integer arithmetic as well as number theoretic functionality. 7 * 8 * The library was designed directly after the MPI library by 9 * Michael Fromberger but has been written from scratch with 10 * additional optimizations in place. 11 * 12 * The library is free for all purposes without any express 13 * guarantee it works. 14 * 15 * Tom St Denis, tomstdenis (at) gmail.com, http://math.libtomcrypt.com 16 */ 17 18 /* high level multiplication (handles sign) */ 19 int mp_mul (mp_int * a, mp_int * b, mp_int * c) 20 { 21 int res, neg; 22 neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG; 23 24 /* use Toom-Cook? */ 25 #ifdef BN_MP_TOOM_MUL_C 26 if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) { 27 res = mp_toom_mul(a, b, c); 28 } else 29 #endif 30 #ifdef BN_MP_KARATSUBA_MUL_C 31 /* use Karatsuba? */ 32 if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) { 33 res = mp_karatsuba_mul (a, b, c); 34 } else 35 #endif 36 { 37 /* can we use the fast multiplier? 38 * 39 * The fast multiplier can be used if the output will 40 * have less than MP_WARRAY digits and the number of 41 * digits won't affect carry propagation 42 */ 43 int digs = a->used + b->used + 1; 44 45 #ifdef BN_FAST_S_MP_MUL_DIGS_C 46 if ((digs < MP_WARRAY) && 47 MIN(a->used, b->used) <= 48 (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { 49 res = fast_s_mp_mul_digs (a, b, c, digs); 50 } else 51 #endif 52 #ifdef BN_S_MP_MUL_DIGS_C 53 res = s_mp_mul (a, b, c); /* uses s_mp_mul_digs */ 54 #else 55 res = MP_VAL; 56 #endif 57 58 } 59 c->sign = (c->used > 0) ? neg : MP_ZPOS; 60 return res; 61 } 62 #endif 63 64 /* $Source: /cvs/libtom/libtommath/bn_mp_mul.c,v $ */ 65 /* $Revision: 1.3 $ */ 66 /* $Date: 2006/03/31 14:18:44 $ */ 67
