1 files changed, 66 insertions, 0 deletions
diff --git a/mysys/my_rnd.c b/mysys/my_rnd.c
new file mode 100644
index 00000000..b1dd8b1f
--- /dev/null
+++ b/mysys/my_rnd.c
@@ -0,0 +1,66 @@
+/* Copyright (C) 2007 MySQL AB & Michael Widenius
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
+
+#include "mysys_priv.h"
+#include <my_rnd.h>
+#include <m_string.h>
+
+/*
+  Initialize random generator
+
+  NOTES
+    MySQL's password checks depends on this, so don't do any changes
+    that changes the random numbers that are generated!
+*/
+
+void my_rnd_init(struct my_rnd_struct *rand_st, ulong seed1, ulong seed2)
+{
+#ifdef HAVE_valgrind
+  bzero((char*) rand_st,sizeof(*rand_st));      /* Avoid UMC varnings */
+#endif
+  rand_st->max_value= 0x3FFFFFFFL;
+  rand_st->max_value_dbl=(double) rand_st->max_value;
+  rand_st->seed1=seed1%rand_st->max_value ;
+  rand_st->seed2=seed2%rand_st->max_value;
+}
+
+
+/*
+  Generate random number.
+
+  SYNOPSIS
+    my_rnd()
+    rand_st    INOUT  Structure used for number generation
+    
+  RETURN VALUE
+    generated pseudo random number
+
+  NOTE:
+    This is codes so that it can be called by two threads at the same time
+    with minimum impact.
+    (As the number is supposed to be random, it doesn't matter much if
+    rand->seed1 or rand->seed2 are updated with slightly wrong numbers or
+    if two threads gets the same number.
+*/
+
+double my_rnd(struct my_rnd_struct *rand_st)
+{
+  unsigned long seed1;
+  seed1= (rand_st->seed1*3+rand_st->seed2) % rand_st->max_value;
+  rand_st->seed2=(seed1+rand_st->seed2+33) % rand_st->max_value;
+  rand_st->seed1= seed1;
+  return (((double) seed1)/rand_st->max_value_dbl);
+}
+