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annotate libtommath/bn_mp_lcm.c @ 1938:77bc00dcc19f default tip main master

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Bump version to 2022.82
author Matt Johnston <matt@ucc.asn.au>
date Fri, 01 Apr 2022 14:43:27 +0800
parents 1051e4eea25a
children
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1655
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
diff changeset
1 #include "tommath_private.h"
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2 #ifdef BN_MP_LCM_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
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4 /* SPDX-License-Identifier: Unlicense */
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6 /* computes least common multiple as |a*b|/(a, b) */
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7 mp_err mp_lcm(const mp_int *a, const mp_int *b, mp_int *c)
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8 {
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9 mp_err err;
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parents: 1470
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10 mp_int t1, t2;
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12
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13 if ((err = mp_init_multi(&t1, &t2, NULL)) != MP_OKAY) {
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14 return err;
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parents: 1470
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15 }
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16
1655
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parents: 1470
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17 /* t1 = get the GCD of the two inputs */
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18 if ((err = mp_gcd(a, b, &t1)) != MP_OKAY) {
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19 goto LBL_T;
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parents: 1470
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20 }
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21
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parents: 1470
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22 /* divide the smallest by the GCD */
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23 if (mp_cmp_mag(a, b) == MP_LT) {
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parents: 1470
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24 /* store quotient in t2 such that t2 * b is the LCM */
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25 if ((err = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
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26 goto LBL_T;
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27 }
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28 err = mp_mul(b, &t2, c);
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parents: 1470
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29 } else {
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parents: 1470
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30 /* store quotient in t2 such that t2 * a is the LCM */
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31 if ((err = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
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parents: 1470
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32 goto LBL_T;
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parents: 1470
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33 }
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34 err = mp_mul(a, &t2, c);
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parents: 1470
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35 }
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36
1655
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parents: 1470
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37 /* fix the sign to positive */
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38 c->sign = MP_ZPOS;
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40 LBL_T:
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41 mp_clear_multi(&t1, &t2, NULL);
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42 return err;
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43 }
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44 #endif