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-rw-r--r--mysys/my_rnd.c66
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+/* 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);
+}
+