36 lines
1.0 KiB
C
36 lines
1.0 KiB
C
#include "amplify_tommath_private.h"
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#ifdef AMPLIFY_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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/* Modifications Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. */
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/* Decrement "a" by one like "a--". Changes input! */
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amplify_mp_err amplify_mp_decr(amplify_mp_int *a)
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{
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if (AMPLIFY_MP_IS_ZERO(a)) {
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amplify_mp_set(a,1uL);
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a->sign = AMPLIFY_MP_NEG;
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return AMPLIFY_MP_OKAY;
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} else if (a->sign == AMPLIFY_MP_NEG) {
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amplify_mp_err err;
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a->sign = AMPLIFY_MP_ZPOS;
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if ((err = amplify_mp_incr(a)) != AMPLIFY_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 (!AMPLIFY_MP_IS_ZERO(a)) {
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a->sign = AMPLIFY_MP_NEG;
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}
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return AMPLIFY_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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amplify_mp_zero(a);
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}
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return AMPLIFY_MP_OKAY;
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} else {
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return amplify_mp_sub_d(a, 1uL,a);
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}
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}
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#endif
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