Import code from previous AssetBuilder version

thirdparty/libtommath/bn_mp_reduce_is_2k.c

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+#include "tommath_private.h"
+#ifdef BN_MP_REDUCE_IS_2K_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.
+ *
+ * SPDX-License-Identifier: Unlicense
+ */
+
+/* determines if mp_reduce_2k can be used */
+int mp_reduce_is_2k(const mp_int *a)
+{
+   int ix, iy, iw;
+   mp_digit iz;
+
+   if (a->used == 0) {
+      return MP_NO;
+   } else if (a->used == 1) {
+      return MP_YES;
+   } else if (a->used > 1) {
+      iy = mp_count_bits(a);
+      iz = 1;
+      iw = 1;
+
+      /* Test every bit from the second digit up, must be 1 */
+      for (ix = DIGIT_BIT; ix < iy; ix++) {
+         if ((a->dp[iw] & iz) == 0u) {
+            return MP_NO;
+         }
+         iz <<= 1;
+         if (iz > (mp_digit)MP_MASK) {
+            ++iw;
+            iz = 1;
+         }
+      }
+   }
+   return MP_YES;
+}
+
+#endif
+
+/* ref:         HEAD -> master, tag: v1.1.0 */
+/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
+/* commit time: 2019-01-28 20:32:32 +0100 */