--- a/libtommath/bn_s_mp_mul_high_digs.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_s_mp_mul_high_digs.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,81 +1,64 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_S_MP_MUL_HIGH_DIGS_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 */
 
 /* multiplies |a| * |b| and does not compute the lower digs digits
  * [meant to get the higher part of the product]
  */
-int
-s_mp_mul_high_digs (mp_int * a, mp_int * b, mp_int * c, int digs)
+mp_err s_mp_mul_high_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs)
 {
-  mp_int  t;
-  int     res, pa, pb, ix, iy;
-  mp_digit u;
-  mp_word r;
-  mp_digit tmpx, *tmpt, *tmpy;
+   mp_int   t;
+   int      pa, pb, ix, iy;
+   mp_err   err;
+   mp_digit u;
+   mp_word  r;
+   mp_digit tmpx, *tmpt, *tmpy;
 
-  /* can we use the fast multiplier? */
-#ifdef BN_FAST_S_MP_MUL_HIGH_DIGS_C
-  if (((a->used + b->used + 1) < MP_WARRAY)
-      && (MIN (a->used, b->used) < (1 << ((CHAR_BIT * sizeof(mp_word)) - (2 * DIGIT_BIT))))) {
-    return fast_s_mp_mul_high_digs (a, b, c, digs);
-  }
-#endif
+   /* can we use the fast multiplier? */
+   if (MP_HAS(S_MP_MUL_HIGH_DIGS_FAST)
+       && ((a->used + b->used + 1) < MP_WARRAY)
+       && (MP_MIN(a->used, b->used) < MP_MAXFAST)) {
+      return s_mp_mul_high_digs_fast(a, b, c, digs);
+   }
 
-  if ((res = mp_init_size (&t, a->used + b->used + 1)) != MP_OKAY) {
-    return res;
-  }
-  t.used = a->used + b->used + 1;
+   if ((err = mp_init_size(&t, a->used + b->used + 1)) != MP_OKAY) {
+      return err;
+   }
+   t.used = a->used + b->used + 1;
 
-  pa = a->used;
-  pb = b->used;
-  for (ix = 0; ix < pa; ix++) {
-    /* clear the carry */
-    u = 0;
+   pa = a->used;
+   pb = b->used;
+   for (ix = 0; ix < pa; ix++) {
+      /* clear the carry */
+      u = 0;
 
-    /* left hand side of A[ix] * B[iy] */
-    tmpx = a->dp[ix];
+      /* left hand side of A[ix] * B[iy] */
+      tmpx = a->dp[ix];
 
-    /* alias to the address of where the digits will be stored */
-    tmpt = &(t.dp[digs]);
+      /* alias to the address of where the digits will be stored */
+      tmpt = &(t.dp[digs]);
 
-    /* alias for where to read the right hand side from */
-    tmpy = b->dp + (digs - ix);
+      /* alias for where to read the right hand side from */
+      tmpy = b->dp + (digs - ix);
 
-    for (iy = digs - ix; iy < pb; iy++) {
-      /* calculate the double precision result */
-      r       = (mp_word)*tmpt +
-                ((mp_word)tmpx * (mp_word)*tmpy++) +
-                (mp_word)u;
+      for (iy = digs - ix; iy < pb; iy++) {
+         /* calculate the double precision result */
+         r       = (mp_word)*tmpt +
+                   ((mp_word)tmpx * (mp_word)*tmpy++) +
+                   (mp_word)u;
 
-      /* get the lower part */
-      *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK));
+         /* get the lower part */
+         *tmpt++ = (mp_digit)(r & (mp_word)MP_MASK);
 
-      /* carry the carry */
-      u       = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
-    }
-    *tmpt = u;
-  }
-  mp_clamp (&t);
-  mp_exch (&t, c);
-  mp_clear (&t);
-  return MP_OKAY;
+         /* carry the carry */
+         u       = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
+      }
+      *tmpt = u;
+   }
+   mp_clamp(&t);
+   mp_exch(&t, c);
+   mp_clear(&t);
+   return MP_OKAY;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */