--- a/libtommath/bn_mp_div_2.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_mp_div_2.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,68 +1,49 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_DIV_2_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 */
 
 /* b = a/2 */
-int mp_div_2(mp_int * a, mp_int * b)
+mp_err mp_div_2(const mp_int *a, mp_int *b)
 {
-  int     x, res, oldused;
+   int     x, oldused;
+   mp_digit r, rr, *tmpa, *tmpb;
+   mp_err err;
 
-  /* copy */
-  if (b->alloc < a->used) {
-    if ((res = mp_grow (b, a->used)) != MP_OKAY) {
-      return res;
-    }
-  }
+   /* copy */
+   if (b->alloc < a->used) {
+      if ((err = mp_grow(b, a->used)) != MP_OKAY) {
+         return err;
+      }
+   }
 
-  oldused = b->used;
-  b->used = a->used;
-  {
-    mp_digit r, rr, *tmpa, *tmpb;
+   oldused = b->used;
+   b->used = a->used;
 
-    /* source alias */
-    tmpa = a->dp + b->used - 1;
+   /* source alias */
+   tmpa = a->dp + b->used - 1;
 
-    /* dest alias */
-    tmpb = b->dp + b->used - 1;
+   /* dest alias */
+   tmpb = b->dp + b->used - 1;
 
-    /* carry */
-    r = 0;
-    for (x = b->used - 1; x >= 0; x--) {
+   /* carry */
+   r = 0;
+   for (x = b->used - 1; x >= 0; x--) {
       /* get the carry for the next iteration */
-      rr = *tmpa & 1;
+      rr = *tmpa & 1u;
 
       /* shift the current digit, add in carry and store */
-      *tmpb-- = (*tmpa-- >> 1) | (r << (DIGIT_BIT - 1));
+      *tmpb-- = (*tmpa-- >> 1) | (r << (MP_DIGIT_BIT - 1));
 
       /* forward carry to next iteration */
       r = rr;
-    }
+   }
 
-    /* zero excess digits */
-    tmpb = b->dp + b->used;
-    for (x = b->used; x < oldused; x++) {
-      *tmpb++ = 0;
-    }
-  }
-  b->sign = a->sign;
-  mp_clamp (b);
-  return MP_OKAY;
+   /* zero excess digits */
+   MP_ZERO_DIGITS(b->dp + b->used, oldused - b->used);
+
+   b->sign = a->sign;
+   mp_clamp(b);
+   return MP_OKAY;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */