--- a/libtommath/bn_mp_div_d.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_mp_div_d.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,115 +1,84 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_DIV_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
- */
-
-static int s_is_power_of_two(mp_digit b, int *p)
-{
-   int x;
-
-   /* fast return if no power of two */
-   if ((b == 0) || ((b & (b-1)) != 0)) {
-      return 0;
-   }
-
-   for (x = 0; x < DIGIT_BIT; x++) {
-      if (b == (((mp_digit)1)<<x)) {
-         *p = x;
-         return 1;
-      }
-   }
-   return 0;
-}
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
 /* single digit division (based on routine from MPI) */
-int mp_div_d (mp_int * a, mp_digit b, mp_int * c, mp_digit * d)
+mp_err mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d)
 {
-  mp_int  q;
-  mp_word w;
-  mp_digit t;
-  int     res, ix;
-
-  /* cannot divide by zero */
-  if (b == 0) {
-     return MP_VAL;
-  }
+   mp_int  q;
+   mp_word w;
+   mp_digit t;
+   mp_err err;
+   int ix;
 
-  /* quick outs */
-  if ((b == 1) || (mp_iszero(a) == MP_YES)) {
-     if (d != NULL) {
-        *d = 0;
-     }
-     if (c != NULL) {
-        return mp_copy(a, c);
-     }
-     return MP_OKAY;
-  }
+   /* cannot divide by zero */
+   if (b == 0u) {
+      return MP_VAL;
+   }
 
-  /* power of two ? */
-  if (s_is_power_of_two(b, &ix) == 1) {
-     if (d != NULL) {
-        *d = a->dp[0] & ((((mp_digit)1)<<ix) - 1);
-     }
-     if (c != NULL) {
-        return mp_div_2d(a, ix, c, NULL);
-     }
-     return MP_OKAY;
-  }
+   /* quick outs */
+   if ((b == 1u) || MP_IS_ZERO(a)) {
+      if (d != NULL) {
+         *d = 0;
+      }
+      if (c != NULL) {
+         return mp_copy(a, c);
+      }
+      return MP_OKAY;
+   }
 
-#ifdef BN_MP_DIV_3_C
-  /* three? */
-  if (b == 3) {
-     return mp_div_3(a, c, d);
-  }
-#endif
+   /* power of two ? */
+   if ((b & (b - 1u)) == 0u) {
+      ix = 1;
+      while ((ix < MP_DIGIT_BIT) && (b != (((mp_digit)1)<<ix))) {
+         ix++;
+      }
+      if (d != NULL) {
+         *d = a->dp[0] & (((mp_digit)1<<(mp_digit)ix) - 1uL);
+      }
+      if (c != NULL) {
+         return mp_div_2d(a, ix, c, NULL);
+      }
+      return MP_OKAY;
+   }
+
+   /* three? */
+   if (MP_HAS(MP_DIV_3) && (b == 3u)) {
+      return mp_div_3(a, c, d);
+   }
+
+   /* no easy answer [c'est la vie].  Just division */
+   if ((err = mp_init_size(&q, a->used)) != MP_OKAY) {
+      return err;
+   }
 
-  /* no easy answer [c'est la vie].  Just division */
-  if ((res = mp_init_size(&q, a->used)) != MP_OKAY) {
-     return res;
-  }
-  
-  q.used = a->used;
-  q.sign = a->sign;
-  w = 0;
-  for (ix = a->used - 1; ix >= 0; ix--) {
-     w = (w << ((mp_word)DIGIT_BIT)) | ((mp_word)a->dp[ix]);
-     
-     if (w >= b) {
-        t = (mp_digit)(w / b);
-        w -= ((mp_word)t) * ((mp_word)b);
+   q.used = a->used;
+   q.sign = a->sign;
+   w = 0;
+   for (ix = a->used - 1; ix >= 0; ix--) {
+      w = (w << (mp_word)MP_DIGIT_BIT) | (mp_word)a->dp[ix];
+
+      if (w >= b) {
+         t = (mp_digit)(w / b);
+         w -= (mp_word)t * (mp_word)b;
       } else {
-        t = 0;
+         t = 0;
       }
-      q.dp[ix] = (mp_digit)t;
-  }
-  
-  if (d != NULL) {
-     *d = (mp_digit)w;
-  }
-  
-  if (c != NULL) {
-     mp_clamp(&q);
-     mp_exch(&q, c);
-  }
-  mp_clear(&q);
-  
-  return res;
+      q.dp[ix] = t;
+   }
+
+   if (d != NULL) {
+      *d = (mp_digit)w;
+   }
+
+   if (c != NULL) {
+      mp_clamp(&q);
+      mp_exch(&q, c);
+   }
+   mp_clear(&q);
+
+   return err;
 }
 
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */