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+/* mpn_random2 -- Generate random numbers with relatively long strings
+ of ones and zeroes. Suitable for border testing.
+
+Copyright (C) 1992, 1993, 1994, 1996 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 Library General Public License as published by
+the Free Software Foundation; either version 2 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 Library General Public
+License for more details.
+
+You should have received a copy of the GNU Library 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"
+
+#if defined (__hpux) || defined (alpha__) || defined (__svr4__) || defined (__SVR4)
+/* HPUX lacks random(). DEC OSF/1 1.2 random() returns a double. */
+long mrand48 ();
+static inline long
+random ()
+{
+ return mrand48 ();
+}
+#else
+long random ();
+#endif
+
+/* It's a bit tricky to get this right, so please test the code well
+ if you hack with it. Some early versions of the function produced
+ random numbers with the leading limb == 0, and some versions never
+ made the most significant bit set. */
+
+void
+mpn_random2 (res_ptr, size)
+ mp_ptr res_ptr;
+ mp_size_t size;
+{
+ int n_bits;
+ int bit_pos;
+ mp_size_t limb_pos;
+ unsigned int ran;
+ mp_limb_t limb;
+
+ limb = 0;
+
+ /* Start off in a random bit position in the most significant limb. */
+ bit_pos = random () & (BITS_PER_MP_LIMB - 1);
+
+ /* Least significant bit of RAN chooses string of ones/string of zeroes.
+ Make most significant limb be non-zero by setting bit 0 of RAN. */
+ ran = random () | 1;
+
+ for (limb_pos = size - 1; limb_pos >= 0; )
+ {
+ n_bits = (ran >> 1) % BITS_PER_MP_LIMB + 1;
+ if ((ran & 1) != 0)
+ {
+ /* Generate a string of ones. */
+ if (n_bits >= bit_pos)
+ {
+ res_ptr[limb_pos--] = limb | ((((mp_limb_t) 2) << bit_pos) - 1);
+ bit_pos += BITS_PER_MP_LIMB;
+ limb = (~(mp_limb_t) 0) << (bit_pos - n_bits);
+ }
+ else
+ {
+ limb |= ((((mp_limb_t) 1) << n_bits) - 1) << (bit_pos - n_bits + 1);
+ }
+ }
+ else
+ {
+ /* Generate a string of zeroes. */
+ if (n_bits >= bit_pos)
+ {
+ res_ptr[limb_pos--] = limb;
+ limb = 0;
+ bit_pos += BITS_PER_MP_LIMB;
+ }
+ }
+ bit_pos -= n_bits;
+ ran = random ();
+ }
+}
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