Reorganisation of the source tree

[ghc-hetmet.git] / rts / gmp / mpz / urandomm.c

diff --git a/rts/gmp/mpz/urandomm.c b/rts/gmp/mpz/urandomm.c
new file mode 100644 (file)
index 0000000..69e1bae
--- /dev/null
+++ b/rts/gmp/mpz/urandomm.c
@@ -0,0 +1,78 @@
+/* mpz_urandomm (rop, state, n) -- Generate a uniform pseudorandom
+   integer in the range 0 to N-1, using STATE as the random state
+   previously initialized by a call to gmp_randinit().
+
+Copyright (C) 2000  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 2.1 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; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+void
+#if __STDC__
+mpz_urandomm (mpz_t rop, gmp_randstate_t rstate, mpz_t n)
+#else
+mpz_urandomm (rop, rstate, n)
+     mpz_t rop;
+     gmp_randstate_t rstate;
+     mpz_t n;
+#endif
+{
+  mpz_t t, p, m;
+  mp_ptr tp;
+  mp_size_t nbits, size;
+  int count;
+  TMP_DECL (marker);
+
+  TMP_MARK (marker);
+
+  /* FIXME: Should check for n == 0 and report error */
+
+  size = SIZ (n);
+  count_leading_zeros (count, PTR (n)[size - 1]);
+  nbits = size * BITS_PER_MP_LIMB - count;
+
+  /* Allocate enough for any mpz function called since a realloc of
+     these will fail.  */
+  MPZ_TMP_INIT (t, size);
+  MPZ_TMP_INIT (m, size + 1);
+  MPZ_TMP_INIT (p, size + 1);
+
+  /* Let m = highest possible random number plus 1.  */
+  mpz_set_ui (m, 0);
+  mpz_setbit (m, nbits);
+
+  /* Let p = floor(m / n) * n.  */
+  mpz_fdiv_q (p, m, n);
+  mpz_mul (p, p, n);
+
+  tp = PTR (t);
+  do
+    {
+      _gmp_rand (tp, rstate, nbits);
+      MPN_NORMALIZE (tp, size);        /* FIXME: Really necessary?  */
+      SIZ (t) = size;
+    }
+  while (mpz_cmp (t, p) >= 0);
+
+  mpz_mod (rop, t, n);
+
+  TMP_FREE (marker);
+}