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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);
}
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