--- /dev/null
+#include "tommath_private.h"
+#ifdef BN_MP_REDUCE_IS_2K_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* determines if mp_reduce_2k can be used */
+mp_bool 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 = MP_DIGIT_BIT; ix < iy; ix++) {
+ if ((a->dp[iw] & iz) == 0u) {
+ return MP_NO;
+ }
+ iz <<= 1;
+ if (iz > MP_DIGIT_MAX) {
+ ++iw;
+ iz = 1;
+ }
+ }
+ return MP_YES;
+ } else {
+ return MP_YES;
+ }
+}
+
+#endif