1 /* $NetBSD: bn_mp_reduce_2k_setup.c,v 1.1.1.1 2011/04/13 18:14:54 elric Exp $ */ 2 3 #include <tommath.h> 4 #ifdef BN_MP_REDUCE_2K_SETUP_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 /* determines the setup value */ 21 int mp_reduce_2k_setup(mp_int *a, mp_digit *d) 22 { 23 int res, p; 24 mp_int tmp; 25 26 if ((res = mp_init(&tmp)) != MP_OKAY) { 27 return res; 28 } 29 30 p = mp_count_bits(a); 31 if ((res = mp_2expt(&tmp, p)) != MP_OKAY) { 32 mp_clear(&tmp); 33 return res; 34 } 35 36 if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) { 37 mp_clear(&tmp); 38 return res; 39 } 40 41 *d = tmp.dp[0]; 42 mp_clear(&tmp); 43 return MP_OKAY; 44 } 45 #endif 46 47 /* Source: /cvs/libtom/libtommath/bn_mp_reduce_2k_setup.c,v */ 48 /* Revision: 1.4 */ 49 /* Date: 2006/12/28 01:25:13 */ 50