From 3a926f0228c68d7d91cf3946624d7859976440ec Mon Sep 17 00:00:00 2001
From: Ladislav Zezula <ladislav.zezula@avg.com>
Date: Fri, 11 Jan 2013 14:55:08 +0100
Subject: Initial creation

---
 src/libtommath/bn_mp_div_d.c | 115 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 src/libtommath/bn_mp_div_d.c

(limited to 'src/libtommath/bn_mp_div_d.c')

diff --git a/src/libtommath/bn_mp_div_d.c b/src/libtommath/bn_mp_div_d.c
new file mode 100644
index 0000000..c0318a4
--- /dev/null
+++ b/src/libtommath/bn_mp_div_d.c
@@ -0,0 +1,115 @@
+#include "tommath.h"
+#ifdef BN_MP_DIV_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@gmail.com, http://libtom.org
+ */
+
+static int s_is_power_of_two(mp_digit b, int *p)
+{
+   int x;
+
+   /* fast return if no power of two */
+   if ((b==0) || (b & (b-1))) {
+      return 0;
+   }
+
+   for (x = 0; x < DIGIT_BIT; x++) {
+      if (b == (((mp_digit)1)<<x)) {
+         *p = x;
+         return 1;
+      }
+   }
+   return 0;
+}
+
+/* single digit division (based on routine from MPI) */
+int mp_div_d (mp_int * a, mp_digit b, mp_int * c, mp_digit * d)
+{
+  mp_int  q;
+  mp_word w;
+  mp_digit t;
+  int     res, ix;
+
+  /* cannot divide by zero */
+  if (b == 0) {
+     return MP_VAL;
+  }
+
+  /* quick outs */
+  if (b == 1 || mp_iszero(a) == 1) {
+     if (d != NULL) {
+        *d = 0;
+     }
+     if (c != NULL) {
+        return mp_copy(a, c);
+     }
+     return MP_OKAY;
+  }
+
+  /* power of two ? */
+  if (s_is_power_of_two(b, &ix) == 1) {
+     if (d != NULL) {
+        *d = a->dp[0] & ((((mp_digit)1)<<ix) - 1);
+     }
+     if (c != NULL) {
+        return mp_div_2d(a, ix, c, NULL);
+     }
+     return MP_OKAY;
+  }
+
+#ifdef BN_MP_DIV_3_C
+  /* three? */
+  if (b == 3) {
+     return mp_div_3(a, c, d);
+  }
+#endif
+
+  /* no easy answer [c'est la vie].  Just division */
+  if ((res = mp_init_size(&q, a->used)) != MP_OKAY) {
+     return res;
+  }
+  
+  q.used = a->used;
+  q.sign = a->sign;
+  w = 0;
+  for (ix = a->used - 1; ix >= 0; ix--) {
+     w = (w << ((mp_word)DIGIT_BIT)) | ((mp_word)a->dp[ix]);
+     
+     if (w >= b) {
+        t = (mp_digit)(w / b);
+        w -= ((mp_word)t) * ((mp_word)b);
+      } else {
+        t = 0;
+      }
+      q.dp[ix] = (mp_digit)t;
+  }
+  
+  if (d != NULL) {
+     *d = (mp_digit)w;
+  }
+  
+  if (c != NULL) {
+     mp_clamp(&q);
+     mp_exch(&q, c);
+  }
+  mp_clear(&q);
+  
+  return res;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtommath/bn_mp_div_d.c,v $ */
+/* $Revision: 1.5 $ */
+/* $Date: 2007/01/09 04:44:32 $ */
-- 
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