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annotate libtommath/bn_mp_add.c @ 1663:c795520269f9

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Fallback for key gen without hard link support (#89) Add a non-atomic fallback for key generation on platforms where link() is not permitted (such as most stock Android installs) or on filesystems without hard link support (such as FAT).
author Matt Robinson <git@nerdoftheherd.com>
date Sat, 14 Mar 2020 14:37:35 +0000
parents f52919ffd3b1
children 1051e4eea25a
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_ADD_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 * SPDX-License-Identifier: Unlicense
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13 */
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14
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15 /* high level addition (handles signs) */
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16 int mp_add(const mp_int *a, const mp_int *b, mp_int *c)
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17 {
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18 int sa, sb, res;
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19
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20 /* get sign of both inputs */
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21 sa = a->sign;
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22 sb = b->sign;
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23
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24 /* handle two cases, not four */
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25 if (sa == sb) {
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26 /* both positive or both negative */
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27 /* add their magnitudes, copy the sign */
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28 c->sign = sa;
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29 res = s_mp_add(a, b, c);
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30 } else {
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31 /* one positive, the other negative */
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32 /* subtract the one with the greater magnitude from */
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33 /* the one of the lesser magnitude. The result gets */
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34 /* the sign of the one with the greater magnitude. */
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35 if (mp_cmp_mag(a, b) == MP_LT) {
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36 c->sign = sb;
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37 res = s_mp_sub(b, a, c);
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38 } else {
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39 c->sign = sa;
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40 res = s_mp_sub(a, b, c);
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41 }
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42 }
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43 return res;
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44 }
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46 #endif
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48 /* ref: HEAD -> master, tag: v1.1.0 */
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49 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
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50 /* commit time: 2019-01-28 20:32:32 +0100 */