155 lines
3.6 KiB
C
155 lines
3.6 KiB
C
/*
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* This file is distributed as part of the MariaDB Corporation MaxScale. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright MariaDB Corporation Ab 2013-2014
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*/
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/**
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* @file random_jkiss.c - Random number generator for the MariaDB Corporation MaxScale
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*
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* See http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf for discussion of random
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* number generators (RNGs).
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*
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* @verbatim
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* Revision History
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*
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* Date Who Description
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* 26/08/15 Martin Brampton Initial implementation
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*
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* @endverbatim
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*/
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#include <stdbool.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <spinlock.h>
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#include <random_jkiss.h>
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/* Public domain code for JKISS RNG - Comment header added */
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/* If possible, the seed variables will be set from /dev/urandom but
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* should that fail, these arbitrary numbers will be used as a last resort.
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*/
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static unsigned int x = 123456789,y = 987654321,z = 43219876,c = 6543217; /* Seed variables */
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static bool init = false;
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static SPINLOCK random_jkiss_spinlock = SPINLOCK_INIT;
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static unsigned int random_jkiss_devrand(void);
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static void random_init_jkiss(void);
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/***
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*
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* Return a pseudo-random number that satisfies major tests for random sequences
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*
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* @return uint Random number
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*
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*/
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unsigned int
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random_jkiss(void)
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{
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unsigned long long t;
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unsigned int result;
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spinlock_acquire(&random_jkiss_spinlock);
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if (!init)
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{
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/* Must set init first because initialisation calls this function */
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init = true;
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spinlock_release(&random_jkiss_spinlock);
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random_init_jkiss();
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}
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x = 314527869 * x + 1234567;
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y ^= y << 5;
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y ^= y >> 7;
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y ^= y << 22;
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t = 4294584393ULL * z + c;
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c = t >> 32;
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z = t;
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result = x + y + z;
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spinlock_release(&random_jkiss_spinlock);
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return result;
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}
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/* Own code adapted from http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf */
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/***
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*
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* Obtain a seed random number from /dev/urandom if available.
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*
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* @return uint Random number
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*
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*/
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static unsigned int
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random_jkiss_devrand(void)
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{
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int fn;
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unsigned int r;
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if ((fn = open("/dev/urandom", O_RDONLY)) == -1)
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{
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return 0;
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}
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if (read(fn, &r, sizeof(r)) != sizeof(r))
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{
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r = 0;
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}
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close(fn);
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return r;
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}
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/***
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*
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* Initialise the generator using /dev/urandom if available, and warm up
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* with 1000 iterations
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*
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*/
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static void
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random_init_jkiss(void)
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{
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int newrand, i;
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spinlock_acquire(&random_jkiss_spinlock);
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if ((newrand = random_jkiss_devrand()) != 0)
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{
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x = newrand;
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}
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if ((newrand = random_jkiss_devrand()) != 0)
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{
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y = newrand;
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}
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if ((newrand = random_jkiss_devrand()) != 0)
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{
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z = newrand;
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}
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if ((newrand = random_jkiss_devrand()) != 0)
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{
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c = newrand % 698769068 + 1; /* Should be less than 698769069 */
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}
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spinlock_release(&random_jkiss_spinlock);
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/* "Warm up" our random number generator */
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for (i = 0; i < 100; i++)
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{
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random_jkiss();
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}
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}
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