1 #include <tommath.h> 2 #ifdef BN_MP_REDUCE_2K_SETUP_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 /* determines the setup value */ 19 int mp_reduce_2k_setup(mp_int *a, mp_digit *d) 20 { 21 int res, p; 22 mp_int tmp; 23 24 if ((res = mp_init(&tmp)) != MP_OKAY) { 25 return res; 26 } 27 28 p = mp_count_bits(a); 29 if ((res = mp_2expt(&tmp, p)) != MP_OKAY) { 30 mp_clear(&tmp); 31 return res; 32 } 33 34 if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) { 35 mp_clear(&tmp); 36 return res; 37 } 38 39 *d = tmp.dp[0]; 40 mp_clear(&tmp); 41 return MP_OKAY; 42 } 43 #endif 44 45 /* $Source: /cvs/libtom/libtommath/bn_mp_reduce_2k_setup.c,v $ */ 46 /* $Revision: 1.3 $ */ 47 /* $Date: 2006/03/31 14:18:44 $ */ 48
