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c43feefa80
and extend configure to test for it properly instead of hard-wiring an assumption that everybody but Windows has the rand48 functions. (We do cheat to the extent of assuming that probing for erand48 will do for the entire rand48 family.) erand48() is unused as of this commit, but a followon patch will cause GEQO to depend on it. Andres Freund, additional hacking by Tom
101 lines
2.7 KiB
C
101 lines
2.7 KiB
C
/*-------------------------------------------------------------------------
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*
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* erand48.c
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*
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* This file supplies versions of erand48(), lrand48(), and srand48()
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* for machines that lack them. (These are all the members of the drand48
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* family that Postgres currently requires. We name the file after erand48
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* because that is the one that configure tests for.)
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*
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*
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* Copyright (c) 1993 Martin Birgmeier
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* All rights reserved.
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*
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* You may redistribute unmodified or modified versions of this source
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* code provided that the above copyright notice and this and the
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* following conditions are retained.
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*
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* This software is provided ``as is'', and comes with no warranties
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* of any kind. I shall in no event be liable for anything that happens
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* to anyone/anything when using this software.
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/port/erand48.c,v 1.1 2009/07/16 17:43:52 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "c.h"
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#include <math.h>
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#define RAND48_SEED_0 (0x330e)
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#define RAND48_SEED_1 (0xabcd)
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#define RAND48_SEED_2 (0x1234)
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#define RAND48_MULT_0 (0xe66d)
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#define RAND48_MULT_1 (0xdeec)
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#define RAND48_MULT_2 (0x0005)
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#define RAND48_ADD (0x000b)
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static unsigned short _rand48_seed[3] = {
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RAND48_SEED_0,
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RAND48_SEED_1,
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RAND48_SEED_2
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};
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static unsigned short _rand48_mult[3] = {
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RAND48_MULT_0,
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RAND48_MULT_1,
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RAND48_MULT_2
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};
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static unsigned short _rand48_add = RAND48_ADD;
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static void
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_dorand48(unsigned short xseed[3])
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{
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unsigned long accu;
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unsigned short temp[2];
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accu = (unsigned long) _rand48_mult[0] * (unsigned long) xseed[0] +
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(unsigned long) _rand48_add;
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temp[0] = (unsigned short) accu; /* lower 16 bits */
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accu >>= sizeof(unsigned short) * 8;
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accu += (unsigned long) _rand48_mult[0] * (unsigned long) xseed[1] +
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(unsigned long) _rand48_mult[1] * (unsigned long) xseed[0];
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temp[1] = (unsigned short) accu; /* middle 16 bits */
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accu >>= sizeof(unsigned short) * 8;
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accu += _rand48_mult[0] * xseed[2] + _rand48_mult[1] * xseed[1] + _rand48_mult[2] * xseed[0];
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xseed[0] = temp[0];
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xseed[1] = temp[1];
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xseed[2] = (unsigned short) accu;
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}
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double
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erand48(unsigned short xseed[3])
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{
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_dorand48(xseed);
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return ldexp((double) xseed[0], -48) +
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ldexp((double) xseed[1], -32) +
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ldexp((double) xseed[2], -16);
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}
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long
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lrand48(void)
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{
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_dorand48(_rand48_seed);
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return ((long) _rand48_seed[2] << 15) + ((long) _rand48_seed[1] >> 1);
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}
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void
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srand48(long seed)
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{
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_rand48_seed[0] = RAND48_SEED_0;
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_rand48_seed[1] = (unsigned short) seed;
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_rand48_seed[2] = (unsigned short) (seed > 16);
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_rand48_mult[0] = RAND48_MULT_0;
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_rand48_mult[1] = RAND48_MULT_1;
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_rand48_mult[2] = RAND48_MULT_2;
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_rand48_add = RAND48_ADD;
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}
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