--- a/libtommath/bn_mp_copy.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_mp_copy.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,68 +1,47 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_COPY_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 */
 
 /* copy, b = a */
-int
-mp_copy (mp_int * a, mp_int * b)
+mp_err mp_copy(const mp_int *a, mp_int *b)
 {
-  int     res, n;
-
-  /* if dst == src do nothing */
-  if (a == b) {
-    return MP_OKAY;
-  }
+   int n;
+   mp_digit *tmpa, *tmpb;
+   mp_err err;
 
-  /* grow dest */
-  if (b->alloc < a->used) {
-     if ((res = mp_grow (b, a->used)) != MP_OKAY) {
-        return res;
-     }
-  }
+   /* if dst == src do nothing */
+   if (a == b) {
+      return MP_OKAY;
+   }
 
-  /* zero b and copy the parameters over */
-  {
-    mp_digit *tmpa, *tmpb;
+   /* grow dest */
+   if (b->alloc < a->used) {
+      if ((err = mp_grow(b, a->used)) != MP_OKAY) {
+         return err;
+      }
+   }
 
-    /* pointer aliases */
+   /* zero b and copy the parameters over */
+   /* pointer aliases */
 
-    /* source */
-    tmpa = a->dp;
+   /* source */
+   tmpa = a->dp;
 
-    /* destination */
-    tmpb = b->dp;
+   /* destination */
+   tmpb = b->dp;
 
-    /* copy all the digits */
-    for (n = 0; n < a->used; n++) {
+   /* copy all the digits */
+   for (n = 0; n < a->used; n++) {
       *tmpb++ = *tmpa++;
-    }
+   }
+
+   /* clear high digits */
+   MP_ZERO_DIGITS(tmpb, b->used - n);
 
-    /* clear high digits */
-    for (; n < b->used; n++) {
-      *tmpb++ = 0;
-    }
-  }
-
-  /* copy used count and sign */
-  b->used = a->used;
-  b->sign = a->sign;
-  return MP_OKAY;
+   /* copy used count and sign */
+   b->used = a->used;
+   b->sign = a->sign;
+   return MP_OKAY;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */