Mercurial > dropbear
comparison libtommath/bn_mp_reduce_is_2k.c @ 389:5ff8218bcee9
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 2af95f00ebd5bb7a28b3817db1218442c935388e)
to branch 'au.asn.ucc.matt.dropbear' (head ecd779509ef23a8cdf64888904fc9b31d78aa933)
author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 11 Jan 2007 03:14:55 +0000 |
parents | eed26cff980b |
children | 60fc6476e044 |
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388:fb54020f78e1 | 389:5ff8218bcee9 |
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1 #include <tommath.h> | |
2 #ifdef BN_MP_REDUCE_IS_2K_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, [email protected], http://math.libtomcrypt.com | |
16 */ | |
17 | |
18 /* determines if mp_reduce_2k can be used */ | |
19 int mp_reduce_is_2k(mp_int *a) | |
20 { | |
21 int ix, iy, iw; | |
22 mp_digit iz; | |
23 | |
24 if (a->used == 0) { | |
25 return MP_NO; | |
26 } else if (a->used == 1) { | |
27 return MP_YES; | |
28 } else if (a->used > 1) { | |
29 iy = mp_count_bits(a); | |
30 iz = 1; | |
31 iw = 1; | |
32 | |
33 /* Test every bit from the second digit up, must be 1 */ | |
34 for (ix = DIGIT_BIT; ix < iy; ix++) { | |
35 if ((a->dp[iw] & iz) == 0) { | |
36 return MP_NO; | |
37 } | |
38 iz <<= 1; | |
39 if (iz > (mp_digit)MP_MASK) { | |
40 ++iw; | |
41 iz = 1; | |
42 } | |
43 } | |
44 } | |
45 return MP_YES; | |
46 } | |
47 | |
48 #endif | |
49 | |
50 /* $Source: /cvs/libtom/libtommath/bn_mp_reduce_is_2k.c,v $ */ | |
51 /* $Revision: 1.3 $ */ | |
52 /* $Date: 2006/03/31 14:18:44 $ */ |