Mercurial > dropbear

annotate libtommath/bn_mp_sub.c @ 447:278805938dcf

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Patch from Nicolai Ehemann to try binding before going to the background, so that if it exits early (because something's already listening etc) then it will return an exitcode of 1.
author Matt Johnston <matt@ucc.asn.au>
date Thu, 19 Jul 2007 15:54:18 +0000
parents 5ff8218bcee9
children 60fc6476e044
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1 #include <tommath.h>
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2 #ifdef BN_MP_SUB_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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17
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18 /* high level subtraction (handles signs) */
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19 int
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20 mp_sub (mp_int * a, mp_int * b, mp_int * c)
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21 {
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22 int sa, sb, res;
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23
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24 sa = a->sign;
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25 sb = b->sign;
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26
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27 if (sa != sb) {
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28 /* subtract a negative from a positive, OR */
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29 /* subtract a positive from a negative. */
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30 /* In either case, ADD their magnitudes, */
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31 /* and use the sign of the first number. */
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32 c->sign = sa;
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33 res = s_mp_add (a, b, c);
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34 } else {
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35 /* subtract a positive from a positive, OR */
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36 /* subtract a negative from a negative. */
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37 /* First, take the difference between their */
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38 /* magnitudes, then... */
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39 if (mp_cmp_mag (a, b) != MP_LT) {
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40 /* Copy the sign from the first */
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41 c->sign = sa;
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42 /* The first has a larger or equal magnitude */
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43 res = s_mp_sub (a, b, c);
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44 } else {
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45 /* The result has the *opposite* sign from */
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46 /* the first number. */
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47 c->sign = (sa == MP_ZPOS) ? MP_NEG : MP_ZPOS;
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48 /* The second has a larger magnitude */
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49 res = s_mp_sub (b, a, c);
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50 }
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51 }
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52 return res;
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53 }
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54
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55 #endif
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56
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57 /* $Source: /cvs/libtom/libtommath/bn_mp_sub.c,v $ */
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58 /* $Revision: 1.3 $ */
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59 /* $Date: 2006/03/31 14:18:44 $ */