35 lines
790 B
C
35 lines
790 B
C
#include "tommath_private.h"
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#ifdef BN_MP_DECR_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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/* Decrement "a" by one like "a--". Changes input! */
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mp_err mp_decr(mp_int *a)
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{
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if (MP_IS_ZERO(a)) {
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mp_set(a,1uL);
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a->sign = MP_NEG;
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return MP_OKAY;
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} else if (a->sign == MP_NEG) {
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mp_err err;
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a->sign = MP_ZPOS;
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if ((err = mp_incr(a)) != MP_OKAY) {
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return err;
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}
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/* There is no -0 in LTM */
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if (!MP_IS_ZERO(a)) {
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a->sign = MP_NEG;
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}
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return MP_OKAY;
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} else if (a->dp[0] > 1uL) {
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a->dp[0]--;
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if (a->dp[0] == 0u) {
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mp_zero(a);
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}
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return MP_OKAY;
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} else {
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return mp_sub_d(a, 1uL,a);
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}
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}
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#endif
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