kc3-lang/libtommath/mp_sub.c

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• Hash : 7a68f128
  Author :
  Date : 2019-10-19T16:24:39
  

  Execute move.sh - Rename files from bn_* to match the function names. * git blame <renamed-file> is not affected * git log --follow <renamed-file> can be used to show log across renames

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• 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)
  {
     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
  

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