1 /* $NetBSD: bn_mp_reduce_is_2k.c,v 1.2 2017/01/28 21:31:47 christos Exp $ */ 2 3 #include <tommath.h> 4 #ifdef BN_MP_REDUCE_IS_2K_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 if mp_reduce_2k can be used */ mp_reduce_is_2k(mp_int * a)21int mp_reduce_is_2k(mp_int *a) 22 { 23 int ix, iy, iw; 24 mp_digit iz; 25 26 if (a->used == 0) { 27 return MP_NO; 28 } else if (a->used == 1) { 29 return MP_YES; 30 } else if (a->used > 1) { 31 iy = mp_count_bits(a); 32 iz = 1; 33 iw = 1; 34 35 /* Test every bit from the second digit up, must be 1 */ 36 for (ix = DIGIT_BIT; ix < iy; ix++) { 37 if ((a->dp[iw] & iz) == 0) { 38 return MP_NO; 39 } 40 iz <<= 1; 41 if (iz > (mp_digit)MP_MASK) { 42 ++iw; 43 iz = 1; 44 } 45 } 46 } 47 return MP_YES; 48 } 49 50 #endif 51 52 /* Source: /cvs/libtom/libtommath/bn_mp_reduce_is_2k.c,v */ 53 /* Revision: 1.4 */ 54 /* Date: 2006/12/28 01:25:13 */ 55