--- a/libtommath/bn_mp_add_d.c	Thu Mar 21 23:28:59 2019 +0800
+++ b/libtommath/bn_mp_add_d.c	Fri Jun 26 21:07:34 2020 +0800
@@ -1,112 +1,89 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_ADD_D_C
-/* LibTomMath, multiple-precision integer library -- Tom St Denis
- *
- * LibTomMath is a library that provides multiple-precision
- * integer arithmetic as well as number theoretic functionality.
- *
- * The library was designed directly after the MPI library by
- * Michael Fromberger but has been written from scratch with
- * additional optimizations in place.
- *
- * The library is free for all purposes without any express
- * guarantee it works.
- *
- * Tom St Denis, [email protected], http://libtom.org
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
 /* single digit addition */
-int
-mp_add_d (mp_int * a, mp_digit b, mp_int * c)
+mp_err mp_add_d(const mp_int *a, mp_digit b, mp_int *c)
 {
-  int     res, ix, oldused;
-  mp_digit *tmpa, *tmpc, mu;
+   mp_err     err;
+   int ix, oldused;
+   mp_digit *tmpa, *tmpc;
 
-  /* grow c as required */
-  if (c->alloc < (a->used + 1)) {
-     if ((res = mp_grow(c, a->used + 1)) != MP_OKAY) {
-        return res;
-     }
-  }
+   /* 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))) {
-     /* temporarily fix sign of a */
-     a->sign = MP_ZPOS;
+   /* 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 */
-     res = mp_sub_d(a, b, c);
+      /* c = |a| - b */
+      err = mp_sub_d(&a_, b, c);
 
-     /* fix sign  */
-     a->sign = c->sign = MP_NEG;
+      /* fix sign  */
+      c->sign = MP_NEG;
 
-     /* clamp */
-     mp_clamp(c);
+      /* clamp */
+      mp_clamp(c);
 
-     return res;
-  }
+      return err;
+   }
 
-  /* old number of used digits in c */
-  oldused = c->used;
+   /* old number of used digits in c */
+   oldused = c->used;
 
-  /* source alias */
-  tmpa    = a->dp;
+   /* source alias */
+   tmpa    = a->dp;
 
-  /* destination alias */
-  tmpc    = c->dp;
+   /* destination alias */
+   tmpc    = c->dp;
 
-  /* if a is positive */
-  if (a->sign == MP_ZPOS) {
-     /* add digit, after this we're propagating
-      * the carry.
-      */
-     *tmpc   = *tmpa++ + b;
-     mu      = *tmpc >> DIGIT_BIT;
-     *tmpc++ &= MP_MASK;
+   /* 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;
 
-     /* now handle rest of the digits */
-     for (ix = 1; ix < a->used; ix++) {
-        *tmpc   = *tmpa++ + mu;
-        mu      = *tmpc >> 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;
 
-     /* 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;
-     }
+      /* 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;
-  }
+      /* setup count so the clearing of oldused
+       * can fall through correctly
+       */
+      ix       = 1;
+   }
 
-  /* sign always positive */
-  c->sign = MP_ZPOS;
+   /* sign always positive */
+   c->sign = MP_ZPOS;
 
-  /* now zero to oldused */
-  while (ix++ < oldused) {
-     *tmpc++ = 0;
-  }
-  mp_clamp(c);
+   /* now zero to oldused */
+   MP_ZERO_DIGITS(tmpc, oldused - ix);
+   mp_clamp(c);
 
-  return MP_OKAY;
+   return MP_OKAY;
 }
 
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */