kc3-lang/libtommath/mp_add_d.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_add_d.c

• #include "tommath_private.h"
  #ifdef MP_ADD_D_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* single digit addition */
  mp_err mp_add_d(const mp_int *a, mp_digit b, mp_int *c)
  {
     mp_err     err;
     int ix, oldused;
     mp_digit *tmpa, *tmpc;
  
     /* grow c as required */
     if (c->alloc < (a->used + 1)) {
        if ((err = mp_grow(c, a->used + 1)) != MP_OKAY) {
           return err;
        }
     }
  
     /* if a is negative and |a| >= b, call c = |a| - b */
     if ((a->sign == MP_NEG) && ((a->used > 1) || (a->dp[0] >= b))) {
        mp_int a_ = *a;
        /* temporarily fix sign of a */
        a_.sign = MP_ZPOS;
  
        /* c = |a| - b */
        err = mp_sub_d(&a_, b, c);
  
        /* fix sign  */
        c->sign = MP_NEG;
  
        /* clamp */
        mp_clamp(c);
  
        return err;
     }
  
     /* old number of used digits in c */
     oldused = c->used;
  
     /* source alias */
     tmpa    = a->dp;
  
     /* destination alias */
     tmpc    = c->dp;
  
     /* if a is positive */
     if (a->sign == MP_ZPOS) {
        /* add digits, mu is carry */
        mp_digit mu = b;
        for (ix = 0; ix < a->used; ix++) {
           *tmpc   = *tmpa++ + mu;
           mu      = *tmpc >> MP_DIGIT_BIT;
           *tmpc++ &= MP_MASK;
        }
        /* set final carry */
        ix++;
        *tmpc++  = mu;
  
        /* setup size */
        c->used = a->used + 1;
     } else {
        /* a was negative and |a| < b */
        c->used  = 1;
  
        /* the result is a single digit */
        if (a->used == 1) {
           *tmpc++  =  b - a->dp[0];
        } else {
           *tmpc++  =  b;
        }
  
        /* setup count so the clearing of oldused
         * can fall through correctly
         */
        ix       = 1;
     }
  
     /* sign always positive */
     c->sign = MP_ZPOS;
  
     /* now zero to oldused */
     MP_ZERO_DIGITS(tmpc, oldused - ix);
     mp_clamp(c);
  
     return MP_OKAY;
  }
  
  #endif
  

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