45 lines
1.1 KiB
C
45 lines
1.1 KiB
C
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#include "tommath_private.h"
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#ifdef BN_MP_LCM_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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/* computes least common multiple as |a*b|/(a, b) */
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mp_err mp_lcm(const mp_int *a, const mp_int *b, mp_int *c)
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{
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mp_err err;
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mp_int t1, t2;
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if ((err = mp_init_multi(&t1, &t2, NULL)) != MP_OKAY) {
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return err;
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}
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/* t1 = get the GCD of the two inputs */
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if ((err = mp_gcd(a, b, &t1)) != MP_OKAY) {
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goto LBL_T;
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}
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/* divide the smallest by the GCD */
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if (mp_cmp_mag(a, b) == MP_LT) {
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/* store quotient in t2 such that t2 * b is the LCM */
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if ((err = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
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goto LBL_T;
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}
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err = mp_mul(b, &t2, c);
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} else {
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/* store quotient in t2 such that t2 * a is the LCM */
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if ((err = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
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goto LBL_T;
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}
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err = mp_mul(a, &t2, c);
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}
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/* fix the sign to positive */
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c->sign = MP_ZPOS;
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LBL_T:
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mp_clear_multi(&t1, &t2, NULL);
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return err;
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}
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#endif
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