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annotate libtommath/bn_mp_set_int.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_SET_INT_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 /* set a 32-bit const */
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19 int mp_set_int (mp_int * a, unsigned long b)
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20 {
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21 int x, res;
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23 mp_zero (a);
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24
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25 /* set four bits at a time */
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26 for (x = 0; x < 8; x++) {
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27 /* shift the number up four bits */
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28 if ((res = mp_mul_2d (a, 4, a)) != MP_OKAY) {
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29 return res;
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30 }
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32 /* OR in the top four bits of the source */
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33 a->dp[0] |= (b >> 28) & 15;
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35 /* shift the source up to the next four bits */
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36 b <<= 4;
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38 /* ensure that digits are not clamped off */
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39 a->used += 1;
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40 }
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41 mp_clamp (a);
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42 return MP_OKAY;
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43 }
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44 #endif
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45
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46 /* $Source: /cvs/libtom/libtommath/bn_mp_set_int.c,v $ */
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47 /* $Revision: 1.3 $ */
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48 /* $Date: 2006/03/31 14:18:44 $ */