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annotate libtommath/bn_mp_decr.c @ 1856:8f28519e34b0

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author Matt Johnston <matt@ucc.asn.au>
date Sun, 23 Jan 2022 17:29:39 +0800
parents 1051e4eea25a
children
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1692
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_DECR_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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5
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6 /* Decrement "a" by one like "a--". Changes input! */
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7 mp_err mp_decr(mp_int *a)
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8 {
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9 if (MP_IS_ZERO(a)) {
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10 mp_set(a,1uL);
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11 a->sign = MP_NEG;
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12 return MP_OKAY;
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13 } else if (a->sign == MP_NEG) {
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14 mp_err err;
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15 a->sign = MP_ZPOS;
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16 if ((err = mp_incr(a)) != MP_OKAY) {
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17 return err;
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18 }
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19 /* There is no -0 in LTM */
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20 if (!MP_IS_ZERO(a)) {
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21 a->sign = MP_NEG;
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22 }
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23 return MP_OKAY;
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24 } else if (a->dp[0] > 1uL) {
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25 a->dp[0]--;
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26 if (a->dp[0] == 0u) {
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27 mp_zero(a);
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28 }
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29 return MP_OKAY;
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30 } else {
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31 return mp_sub_d(a, 1uL,a);
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32 }
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33 }
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34 #endif