--- a/libtommath/bn_mp_mod_2d.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_mp_mod_2d.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,55 +1,38 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_MOD_2D_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 */
 
 /* calc a value mod 2**b */
-int
-mp_mod_2d (mp_int * a, int b, mp_int * c)
+mp_err mp_mod_2d(const mp_int *a, int b, mp_int *c)
 {
-  int     x, res;
+   int x;
+   mp_err err;
 
-  /* if b is <= 0 then zero the int */
-  if (b <= 0) {
-    mp_zero (c);
-    return MP_OKAY;
-  }
+   /* if b is <= 0 then zero the int */
+   if (b <= 0) {
+      mp_zero(c);
+      return MP_OKAY;
+   }
 
-  /* if the modulus is larger than the value than return */
-  if (b >= (int) (a->used * DIGIT_BIT)) {
-    res = mp_copy (a, c);
-    return res;
-  }
+   /* if the modulus is larger than the value than return */
+   if (b >= (a->used * MP_DIGIT_BIT)) {
+      return mp_copy(a, c);
+   }
+
+   /* copy */
+   if ((err = mp_copy(a, c)) != MP_OKAY) {
+      return err;
+   }
 
-  /* copy */
-  if ((res = mp_copy (a, c)) != MP_OKAY) {
-    return res;
-  }
+   /* zero digits above the last digit of the modulus */
+   x = (b / MP_DIGIT_BIT) + (((b % MP_DIGIT_BIT) == 0) ? 0 : 1);
+   MP_ZERO_DIGITS(c->dp + x, c->used - x);
 
-  /* zero digits above the last digit of the modulus */
-  for (x = (b / DIGIT_BIT) + (((b % DIGIT_BIT) == 0) ? 0 : 1); x < c->used; x++) {
-    c->dp[x] = 0;
-  }
-  /* clear the digit that is not completely outside/inside the modulus */
-  c->dp[b / DIGIT_BIT] &=
-    (mp_digit) ((((mp_digit) 1) << (((mp_digit) b) % DIGIT_BIT)) - ((mp_digit) 1));
-  mp_clamp (c);
-  return MP_OKAY;
+   /* clear the digit that is not completely outside/inside the modulus */
+   c->dp[b / MP_DIGIT_BIT] &=
+      ((mp_digit)1 << (mp_digit)(b % MP_DIGIT_BIT)) - (mp_digit)1;
+   mp_clamp(c);
+   return MP_OKAY;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */