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#include "tommath_private.h"
#ifdef BN_MP_DECR_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* Decrement "a" by one like "a--". Changes input! */
mp_err mp_decr(mp_int *a)
{
if (MP_IS_ZERO(a)) {
mp_set(a,1uL);
a->sign = MP_NEG;
return MP_OKAY;
} else if (a->sign == MP_NEG) {
mp_err err;
a->sign = MP_ZPOS;
if ((err = mp_incr(a)) != MP_OKAY) {
return err;
}
/* There is no -0 in LTM */
if (!MP_IS_ZERO(a)) {
a->sign = MP_NEG;
}
return MP_OKAY;
} else if (a->dp[0] > 1uL) {
a->dp[0]--;
if (a->dp[0] == 0u) {
mp_zero(a);
}
return MP_OKAY;
} else {
return mp_sub_d(a, 1uL,a);
}
}
#endif
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