mirror of
https://github.com/linux-apfs/apfstests.git
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Nathan Scott
241 lines
4.9 KiB
C
241 lines
4.9 KiB
C
/**************************************************************************
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*
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* random.c -- pseudo random number generator
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* Copyright (C) 1994 Chris Wallace (csw@bruce.cs.monash.edu.au)
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*
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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; either version 2 of the License, or
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* (at your option) any later version.
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*
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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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*
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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., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*
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**************************************************************************/
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#include <sys/types.h>
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/*
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* modified by dxm@sgi.com so that this file acts as a drop in replacement
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* for srandom and random.
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*/
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/*
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* A random number generator called as a function by
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* random (iseed) or irandm (iseed)
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* The parameter should be a pointer to a 2-element int32_t vector.
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* The first function returns a double uniform in 0 .. 1.
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* The second returns a int32_t integer uniform in 0 .. 2**31-1
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* Both update iseed[] in exactly the same way.
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* iseed[] must be a 2-element integer vector.
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* The initial value of the second element may be anything.
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*
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* The period of the random sequence is 2**32 * (2**32-1)
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* The table mt[0:127] is defined by mt[i] = 69069 ** (128-i)
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*/
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#define MASK ((int32_t) 593970775)
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/* or in hex, 23674657 */
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#define SCALE ((double) 1.0 / (1024.0 * 1024.0 * 1024.0 * 2.0))
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/* i.e. 2 to power -31 */
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static int32_t mt [128] = {
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902906369,
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2030498053,
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-473499623,
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1640834941,
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723406961,
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1993558325,
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-257162999,
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-1627724755,
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913952737,
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278845029,
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1327502073,
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-1261253155,
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981676113,
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-1785280363,
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1700077033,
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366908557,
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-1514479167,
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-682799163,
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141955545,
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-830150595,
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317871153,
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1542036469,
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-946413879,
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-1950779155,
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985397153,
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626515237,
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530871481,
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783087261,
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-1512358895,
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1031357269,
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-2007710807,
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-1652747955,
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-1867214463,
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928251525,
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1243003801,
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-2132510467,
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1874683889,
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-717013323,
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218254473,
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-1628774995,
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-2064896159,
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69678053,
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281568889,
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-2104168611,
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-165128239,
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1536495125,
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-39650967,
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546594317,
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-725987007,
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1392966981,
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1044706649,
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687331773,
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-2051306575,
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1544302965,
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-758494647,
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-1243934099,
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-75073759,
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293132965,
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-1935153095,
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118929437,
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807830417,
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-1416222507,
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-1550074071,
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-84903219,
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1355292929,
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-380482555,
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-1818444007,
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-204797315,
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170442609,
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-1636797387,
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868931593,
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-623503571,
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1711722209,
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381210981,
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-161547783,
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-272740131,
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-1450066095,
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2116588437,
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1100682473,
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358442893,
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-1529216831,
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2116152005,
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-776333095,
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1265240893,
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-482278607,
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1067190005,
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333444553,
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86502381,
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753481377,
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39000101,
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1779014585,
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219658653,
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-920253679,
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2029538901,
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1207761577,
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-1515772851,
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-236195711,
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442620293,
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423166617,
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-1763648515,
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-398436623,
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-1749358155,
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-538598519,
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-652439379,
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430550625,
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-1481396507,
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2093206905,
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-1934691747,
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-962631983,
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1454463253,
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-1877118871,
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-291917555,
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-1711673279,
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201201733,
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-474645415,
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-96764739,
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-1587365199,
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1945705589,
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1303896393,
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1744831853,
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381957665,
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2135332261,
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-55996615,
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-1190135011,
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1790562961,
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-1493191723,
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475559465,
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69069
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};
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double
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_random (int32_t is [2])
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{
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int32_t it, leh, nit;
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it = is [0];
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leh = is [1];
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if (it <= 0)
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it = (it + it) ^ MASK;
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else
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it = it + it;
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nit = it - 1;
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/* to ensure all-ones pattern omitted */
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leh = leh * mt[nit & 127] + nit;
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is [0] = it; is [1] = leh;
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if (leh < 0) leh = ~leh;
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return (SCALE * ((int32_t) (leh | 1)));
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}
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int32_t
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_irandm (int32_t is [2])
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{
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int32_t it, leh, nit;
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it = is [0];
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leh = is [1];
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if (it <= 0)
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it = (it + it) ^ MASK;
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else
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it = it + it;
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nit = it - 1;
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/* to ensure all-ones pattern omitted */
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leh = leh * mt[nit & 127] + nit;
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is [0] = it; is [1] = leh;
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if (leh < 0) leh = ~leh;
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return (leh);
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}
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/*
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* make this a drop in replacement for random and srandom
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*
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* XXX not thread safe I guess.
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*/
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static int32_t saved_seed[2];
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long random(void)
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{
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return _irandm(saved_seed);
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}
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void srandom(unsigned seed)
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{
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saved_seed[0]=seed;
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saved_seed[1]=0;
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_irandm(saved_seed);
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}
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