merge of '5fdf69ca60d1683cdd9f4c2595134bed26394834'

     and '6b61c50f4cf888bea302ac8fcf5dbb573b443251'

--HG--
extra : convert_revision : b1dd3b94e60a07a176dba2b035ac79968595990a

1 files changed, 61 insertions, 0 deletions

diff --git a/libtommath/bn_mp_reduce_2k.c b/libtommath/bn_mp_reduce_2k.c
new file mode 100644
index 0000000..5810696
--- /dev/null
+++ b/libtommath/bn_mp_reduce_2k.c
@@ -0,0 +1,61 @@
+#include <tommath.h>
+#ifdef BN_MP_REDUCE_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.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
+ */
+
+/* reduces a modulo n where n is of the form 2**p - d */
+int mp_reduce_2k(mp_int *a, mp_int *n, mp_digit d)
+{
+   mp_int q;
+   int    p, res;
+   
+   if ((res = mp_init(&q)) != MP_OKAY) {
+      return res;
+   }
+   
+   p = mp_count_bits(n);    
+top:
+   /* q = a/2**p, a = a mod 2**p */
+   if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) {
+      goto ERR;
+   }
+   
+   if (d != 1) {
+      /* q = q * d */
+      if ((res = mp_mul_d(&q, d, &q)) != MP_OKAY) { 
+         goto ERR;
+      }
+   }
+   
+   /* a = a + q */
+   if ((res = s_mp_add(a, &q, a)) != MP_OKAY) {
+      goto ERR;
+   }
+   
+   if (mp_cmp_mag(a, n) != MP_LT) {
+      s_mp_sub(a, n, a);
+      goto top;
+   }
+   
+ERR:
+   mp_clear(&q);
+   return res;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtommath/bn_mp_reduce_2k.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2006/03/31 14:18:44 $ */