Mercurial > dropbear
view libtommath/bn_mp_sub.c @ 1692:1051e4eea25a
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.
author | Steffen Jaeckel <s@jaeckel.eu> |
---|---|
date | Tue, 26 May 2020 17:36:47 +0200 |
parents | f52919ffd3b1 |
children |
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#include "tommath_private.h" #ifdef BN_MP_SUB_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* high level subtraction (handles signs) */ mp_err mp_sub(const mp_int *a, const mp_int *b, mp_int *c) { mp_sign sa = a->sign, sb = b->sign; mp_err err; if (sa != sb) { /* subtract a negative from a positive, OR */ /* subtract a positive from a negative. */ /* In either case, ADD their magnitudes, */ /* and use the sign of the first number. */ c->sign = sa; err = s_mp_add(a, b, c); } else { /* subtract a positive from a positive, OR */ /* subtract a negative from a negative. */ /* First, take the difference between their */ /* magnitudes, then... */ if (mp_cmp_mag(a, b) != MP_LT) { /* Copy the sign from the first */ c->sign = sa; /* The first has a larger or equal magnitude */ err = s_mp_sub(a, b, c); } else { /* The result has the *opposite* sign from */ /* the first number. */ c->sign = (sa == MP_ZPOS) ? MP_NEG : MP_ZPOS; /* The second has a larger magnitude */ err = s_mp_sub(b, a, c); } } return err; } #endif