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66 lines
2 KiB
C
66 lines
2 KiB
C
/* Copyright (C) 2007 MySQL AB & Michael Widenius
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
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#include "mysys_priv.h"
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#include <my_rnd.h>
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#include <m_string.h>
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/*
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Initialize random generator
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NOTES
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MySQL's password checks depends on this, so don't do any changes
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that changes the random numbers that are generated!
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*/
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void my_rnd_init(struct my_rnd_struct *rand_st, ulong seed1, ulong seed2)
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{
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#ifdef HAVE_valgrind
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bzero((char*) rand_st,sizeof(*rand_st)); /* Avoid UMC varnings */
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#endif
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rand_st->max_value= 0x3FFFFFFFL;
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rand_st->max_value_dbl=(double) rand_st->max_value;
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rand_st->seed1=seed1%rand_st->max_value ;
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rand_st->seed2=seed2%rand_st->max_value;
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}
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/*
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Generate random number.
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SYNOPSIS
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my_rnd()
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rand_st INOUT Structure used for number generation
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RETURN VALUE
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generated pseudo random number
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NOTE:
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This is codes so that it can be called by two threads at the same time
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with minimum impact.
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(As the number is supposed to be random, it doesn't matter much if
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rand->seed1 or rand->seed2 are updated with slightly wrong numbers or
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if two threads gets the same number.
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*/
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double my_rnd(struct my_rnd_struct *rand_st)
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{
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unsigned long seed1;
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seed1= (rand_st->seed1*3+rand_st->seed2) % rand_st->max_value;
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rand_st->seed2=(seed1+rand_st->seed2+33) % rand_st->max_value;
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rand_st->seed1= seed1;
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return (((double) seed1)/rand_st->max_value_dbl);
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}
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