dropbear/libtommath/bn_mp_decr.c
Steffen Jaeckel b4bd23b4d2
Update LibTomMath to 1.2.0 (#84)
* update C files

* update other files

* update headers

* update makefiles

* remove mp_set/get_double()

* use ltm 1.2.0 API

* update ltm_desc

* use bundled tommath if system-tommath is too old

* XMALLOC etc. were changed to MP_MALLOC etc.
2020-05-26 23:36:47 +08:00

35 lines
790 B
C

#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