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+#include <tommath.h>
+#ifdef BN_MP_CMP_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, tomstdenis@iahu.ca, http://math.libtomcrypt.org
+ */
+
+/* compare a digit */
+int mp_cmp_d(mp_int * a, mp_digit b)
+{
+ /* compare based on sign */
+ if (a->sign == MP_NEG) {
+ return MP_LT;
+ }
+
+ /* compare based on magnitude */
+ if (a->used > 1) {
+ return MP_GT;
+ }
+
+ /* compare the only digit of a to b */
+ if (a->dp[0] > b) {
+ return MP_GT;
+ } else if (a->dp[0] < b) {
+ return MP_LT;
+ } else {
+ return MP_EQ;
+ }
+}
+#endif