kc3-lang/libtommath/mp_sub.c

• Show log

  Commit

• Hash : 1cc289d2
  Author :
  Date : 2019-11-09T20:23:03
  

  better use of mp_isneg() and mp_iszero()

Download

• mp_sub.c

• #include "tommath_private.h"
  #ifdef 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)
  {
     if (a->sign != b->sign) {
        /* 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 = a->sign;
        return s_mp_add(a, b, c);
     }
  
     /* 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) {
        /* The second has a larger magnitude */
        /* The result has the *opposite* sign from */
        /* the first number. */
        c->sign = (!mp_isneg(a) ? MP_NEG : MP_ZPOS);
        MP_EXCH(const mp_int *, a, b);
     } else {
        /* The first has a larger or equal magnitude */
        /* Copy the sign from the first */
        c->sign = a->sign;
     }
     return s_mp_sub(a, b, c);
  }
  
  #endif
  

Download