Imported gcc-4.4.3

[msp430-gcc.git] / gmp / randmui.c

diff --git a/gmp/randmui.c b/gmp/randmui.c
new file mode 100644 (file)
index 0000000..f349d35
--- /dev/null
+++ b/gmp/randmui.c
@@ -0,0 +1,75 @@
+/* gmp_urandomm_ui -- uniform random number 0 to N-1 for ulong N.
+
+Copyright 2003, 2004 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+/* If n is a power of 2 then the test ret<n is always true and the loop is
+   unnecessary, but there's no need to add special code for this.  Just get
+   the "bits" calculation correct and let it go through normally.
+
+   If n is 1 then will have bits==0 and _gmp_rand will produce no output and
+   we always return 0.  Again there seems no need for a special case, just
+   initialize a[0]=0 and let it go through normally.  */
+
+#define MAX_URANDOMM_ITER  80
+
+unsigned long
+gmp_urandomm_ui (gmp_randstate_ptr rstate, unsigned long n)
+{
+  mp_limb_t      a[LIMBS_PER_ULONG];
+  unsigned long  ret, bits, leading;
+  int            i;
+
+  if (UNLIKELY (n == 0))
+    DIVIDE_BY_ZERO;
+
+  /* start with zeros, since if bits==0 then _gmp_rand will store nothing at
+     all (bits==0 arises when n==1), or if bits <= GMP_NUMB_BITS then it
+     will store only a[0].  */
+  a[0] = 0;
+#if LIMBS_PER_ULONG > 1
+  a[1] = 0;
+#endif
+
+  count_leading_zeros (leading, (mp_limb_t) n);
+  bits = GMP_LIMB_BITS - leading - (POW2_P(n) != 0);
+
+  for (i = 0; i < MAX_URANDOMM_ITER; i++)
+    {
+      _gmp_rand (a, rstate, bits);
+#if LIMBS_PER_ULONG == 1
+      ret = a[0];
+#else
+      ret = a[0] | (a[1] << GMP_NUMB_BITS);
+#endif
+      if (LIKELY (ret < n))   /* usually one iteration suffices */
+        goto done;
+    }
+
+  /* Too many iterations, there must be something degenerate about the
+     rstate algorithm.  Return r%n.  */
+  ret -= n;
+  ASSERT (ret < n);
+
+ done:
+  return ret;
+}