1/* $NetBSD$ */ 2 3#include <tommath.h> 4#ifdef BN_MP_MUL_D_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/* multiply by a digit */ 21int 22mp_mul_d (mp_int * a, mp_digit b, mp_int * c) 23{ 24 mp_digit u, *tmpa, *tmpc; 25 mp_word r; 26 int ix, res, olduse; 27 28 /* make sure c is big enough to hold a*b */ 29 if (c->alloc < a->used + 1) { 30 if ((res = mp_grow (c, a->used + 1)) != MP_OKAY) { 31 return res; 32 } 33 } 34 35 /* get the original destinations used count */ 36 olduse = c->used; 37 38 /* set the sign */ 39 c->sign = a->sign; 40 41 /* alias for a->dp [source] */ 42 tmpa = a->dp; 43 44 /* alias for c->dp [dest] */ 45 tmpc = c->dp; 46 47 /* zero carry */ 48 u = 0; 49 50 /* compute columns */ 51 for (ix = 0; ix < a->used; ix++) { 52 /* compute product and carry sum for this term */ 53 r = ((mp_word) u) + ((mp_word)*tmpa++) * ((mp_word)b); 54 55 /* mask off higher bits to get a single digit */ 56 *tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK)); 57 58 /* send carry into next iteration */ 59 u = (mp_digit) (r >> ((mp_word) DIGIT_BIT)); 60 } 61 62 /* store final carry [if any] and increment ix offset */ 63 *tmpc++ = u; 64 ++ix; 65 66 /* now zero digits above the top */ 67 while (ix++ < olduse) { 68 *tmpc++ = 0; 69 } 70 71 /* set used count */ 72 c->used = a->used + 1; 73 mp_clamp(c); 74 75 return MP_OKAY; 76} 77#endif 78 79/* Source: /cvs/libtom/libtommath/bn_mp_mul_d.c,v */ 80/* Revision: 1.4 */ 81/* Date: 2006/12/28 01:25:13 */ 82