--- a/libtommath/bn_mp_mul_2.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_mp_mul_2.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,82 +1,64 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_MUL_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_mul_2(mp_int * a, mp_int * b)
+mp_err mp_mul_2(const mp_int *a, mp_int *b)
 {
-  int     x, res, oldused;
+   int     x, oldused;
+   mp_err err;
 
-  /* grow to accomodate result */
-  if (b->alloc < (a->used + 1)) {
-    if ((res = mp_grow (b, a->used + 1)) != MP_OKAY) {
-      return res;
-    }
-  }
+   /* grow to accomodate result */
+   if (b->alloc < (a->used + 1)) {
+      if ((err = mp_grow(b, a->used + 1)) != MP_OKAY) {
+         return err;
+      }
+   }
 
-  oldused = b->used;
-  b->used = a->used;
+   oldused = b->used;
+   b->used = a->used;
 
-  {
-    mp_digit r, rr, *tmpa, *tmpb;
+   {
+      mp_digit r, rr, *tmpa, *tmpb;
 
-    /* alias for source */
-    tmpa = a->dp;
-    
-    /* alias for dest */
-    tmpb = b->dp;
+      /* alias for source */
+      tmpa = a->dp;
+
+      /* alias for dest */
+      tmpb = b->dp;
+
+      /* carry */
+      r = 0;
+      for (x = 0; x < a->used; x++) {
 
-    /* carry */
-    r = 0;
-    for (x = 0; x < a->used; x++) {
-    
-      /* get what will be the *next* carry bit from the 
-       * MSB of the current digit 
-       */
-      rr = *tmpa >> ((mp_digit)(DIGIT_BIT - 1));
-      
-      /* now shift up this digit, add in the carry [from the previous] */
-      *tmpb++ = ((*tmpa++ << ((mp_digit)1)) | r) & MP_MASK;
-      
-      /* copy the carry that would be from the source 
-       * digit into the next iteration 
-       */
-      r = rr;
-    }
+         /* get what will be the *next* carry bit from the
+          * MSB of the current digit
+          */
+         rr = *tmpa >> (mp_digit)(MP_DIGIT_BIT - 1);
+
+         /* now shift up this digit, add in the carry [from the previous] */
+         *tmpb++ = ((*tmpa++ << 1uL) | r) & MP_MASK;
+
+         /* copy the carry that would be from the source
+          * digit into the next iteration
+          */
+         r = rr;
+      }
 
-    /* new leading digit? */
-    if (r != 0) {
-      /* add a MSB which is always 1 at this point */
-      *tmpb = 1;
-      ++(b->used);
-    }
+      /* new leading digit? */
+      if (r != 0u) {
+         /* add a MSB which is always 1 at this point */
+         *tmpb = 1;
+         ++(b->used);
+      }
 
-    /* now zero any excess digits on the destination 
-     * that we didn't write to 
-     */
-    tmpb = b->dp + b->used;
-    for (x = b->used; x < oldused; x++) {
-      *tmpb++ = 0;
-    }
-  }
-  b->sign = a->sign;
-  return MP_OKAY;
+      /* now zero any excess digits on the destination
+       * that we didn't write to
+       */
+      MP_ZERO_DIGITS(b->dp + b->used, oldused - b->used);
+   }
+   b->sign = a->sign;
+   return MP_OKAY;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */