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-rw-r--r--libtommath/bn_mp_reduce_2k_setup.c44
1 files changed, 44 insertions, 0 deletions
diff --git a/libtommath/bn_mp_reduce_2k_setup.c b/libtommath/bn_mp_reduce_2k_setup.c
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+++ b/libtommath/bn_mp_reduce_2k_setup.c
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+#include <tommath.h>
+#ifdef BN_MP_REDUCE_2K_SETUP_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
+ */
+
+/* determines the setup value */
+int
+mp_reduce_2k_setup(mp_int *a, mp_digit *d)
+{
+ int res, p;
+ mp_int tmp;
+
+ if ((res = mp_init(&tmp)) != MP_OKAY) {
+ return res;
+ }
+
+ p = mp_count_bits(a);
+ if ((res = mp_2expt(&tmp, p)) != MP_OKAY) {
+ mp_clear(&tmp);
+ return res;
+ }
+
+ if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) {
+ mp_clear(&tmp);
+ return res;
+ }
+
+ *d = tmp.dp[0];
+ mp_clear(&tmp);
+ return MP_OKAY;
+}
+#endif