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annotate libtommath/bn_mp_reduce_2k_setup.c @ 709:abd99ecd7ec2

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use an empty writebuf rather than a NULL one
author Matt Johnston <matt@ucc.asn.au>
date Wed, 20 Mar 2013 22:31:07 +0800
parents 5ff8218bcee9
children 60fc6476e044
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1 #include <tommath.h>
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2 #ifdef BN_MP_REDUCE_2K_SETUP_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://math.libtomcrypt.com
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16 */
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18 /* determines the setup value */
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19 int mp_reduce_2k_setup(mp_int *a, mp_digit *d)
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20 {
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21 int res, p;
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22 mp_int tmp;
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24 if ((res = mp_init(&tmp)) != MP_OKAY) {
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25 return res;
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26 }
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28 p = mp_count_bits(a);
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29 if ((res = mp_2expt(&tmp, p)) != MP_OKAY) {
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30 mp_clear(&tmp);
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31 return res;
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32 }
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34 if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) {
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35 mp_clear(&tmp);
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36 return res;
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37 }
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39 *d = tmp.dp[0];
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40 mp_clear(&tmp);
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41 return MP_OKAY;
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42 }
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43 #endif
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44
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45 /* $Source: /cvs/libtom/libtommath/bn_mp_reduce_2k_setup.c,v $ */
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46 /* $Revision: 1.3 $ */
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47 /* $Date: 2006/03/31 14:18:44 $ */