--- a/libtommath/bn_mp_invmod.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_mp_invmod.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,43 +1,23 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_INVMOD_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 */
 
 /* hac 14.61, pp608 */
-int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
+mp_err mp_invmod(const mp_int *a, const mp_int *b, mp_int *c)
 {
-  /* b cannot be negative */
-  if ((b->sign == MP_NEG) || (mp_iszero(b) == MP_YES)) {
-    return MP_VAL;
-  }
+   /* b cannot be negative and has to be >1 */
+   if ((b->sign == MP_NEG) || (mp_cmp_d(b, 1uL) != MP_GT)) {
+      return MP_VAL;
+   }
 
-#ifdef BN_FAST_MP_INVMOD_C
-  /* if the modulus is odd we can use a faster routine instead */
-  if ((mp_isodd(b) == MP_YES) && (mp_cmp_d(b, 1) != MP_EQ)) {
-    return fast_mp_invmod (a, b, c);
-  }
-#endif
+   /* if the modulus is odd we can use a faster routine instead */
+   if (MP_HAS(S_MP_INVMOD_FAST) && MP_IS_ODD(b)) {
+      return s_mp_invmod_fast(a, b, c);
+   }
 
-#ifdef BN_MP_INVMOD_SLOW_C
-  return mp_invmod_slow(a, b, c);
-#else
-  return MP_VAL;
-#endif
+   return MP_HAS(S_MP_INVMOD_SLOW)
+          ? s_mp_invmod_slow(a, b, c)
+          : MP_VAL;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */