Mercurial > dropbear
comparison bn_mp_reduce_is_2k.c @ 1:22d5cf7d4b1a libtommath
Renaming branch
author | Matt Johnston <matt@ucc.asn.au> |
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date | Mon, 31 May 2004 18:23:46 +0000 |
parents | |
children | d29b64170cf0 |
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-1:000000000000 | 1:22d5cf7d4b1a |
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1 /* LibTomMath, multiple-precision integer library -- Tom St Denis | |
2 * | |
3 * LibTomMath is a library that provides multiple-precision | |
4 * integer arithmetic as well as number theoretic functionality. | |
5 * | |
6 * The library was designed directly after the MPI library by | |
7 * Michael Fromberger but has been written from scratch with | |
8 * additional optimizations in place. | |
9 * | |
10 * The library is free for all purposes without any express | |
11 * guarantee it works. | |
12 * | |
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org | |
14 */ | |
15 #include <tommath.h> | |
16 | |
17 /* determines if mp_reduce_2k can be used */ | |
18 int mp_reduce_is_2k(mp_int *a) | |
19 { | |
20 int ix, iy, iz, iw; | |
21 | |
22 if (a->used == 0) { | |
23 return 0; | |
24 } else if (a->used == 1) { | |
25 return 1; | |
26 } else if (a->used > 1) { | |
27 iy = mp_count_bits(a); | |
28 iz = 1; | |
29 iw = 1; | |
30 | |
31 /* Test every bit from the second digit up, must be 1 */ | |
32 for (ix = DIGIT_BIT; ix < iy; ix++) { | |
33 if ((a->dp[iw] & iz) == 0) { | |
34 return 0; | |
35 } | |
36 iz <<= 1; | |
37 if (iz > (int)MP_MASK) { | |
38 ++iw; | |
39 iz = 1; | |
40 } | |
41 } | |
42 } | |
43 return 1; | |
44 } | |
45 |