rand48.cc

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/*
* Copyright (c) 1993 Martin Birgmeier
* All rights reserved.
*
* You may redistribute unmodified or modified versions of this source
* code provided that the above copyright notice and this and the
* following conditions are retained.
*
* This software is provided ``as is'', and comes with no warranties
* of any kind. I shall in no event be liable for anything that happens
* to anyone/anything when using this software.
*/
 
#ifndef HAVE_SRAND48
 
#include <math.h>
#include <stdlib.h>
#include <spatialindex/tools/rand48.h>
 
#define RAND48_SEED_0   (0x330e)
#define RAND48_SEED_1   (0xabcd)
#define RAND48_SEED_2   (0x1234)
#define RAND48_MULT_0   (0xe66d)
#define RAND48_MULT_1   (0xdeec)
#define RAND48_MULT_2   (0x0005)
#define RAND48_ADD  (0x000b)
 
 
 /* Internal function to compute next state of the generator.  */
static void _dorand48(unsigned short[3]);
 
/* Unfortunately, 3 __globals, which the exported functions must access */
unsigned short __rand48_Seed[3] = {
    RAND48_SEED_0,
    RAND48_SEED_1,
    RAND48_SEED_2
};
unsigned short __rand48_Mult[3] = {
    RAND48_MULT_0,
    RAND48_MULT_1,
    RAND48_MULT_2
};
unsigned short __rand48_Add = RAND48_ADD;
 
/* Internal function to compute next state of the generator.  */
    static void
_dorand48(unsigned short xseed[3])
{
    unsigned long accu;
    unsigned short temp[2];
 
    accu = (unsigned long) __rand48_Mult[0] * (unsigned long) xseed[0] +
     (unsigned long) __rand48_Add;
    temp[0] = (unsigned short) accu;    /* lower 16 bits */
    accu >>= sizeof(unsigned short) * 8;
    accu += (unsigned long) __rand48_Mult[0] * (unsigned long) xseed[1] +
         (unsigned long) __rand48_Mult[1] * (unsigned long) xseed[0];
    temp[1] = (unsigned short) accu;    /* middle 16 bits */
    accu >>= sizeof(unsigned short) * 8;
    accu += __rand48_Mult[0] * xseed[2] + __rand48_Mult[1] * xseed[1] +
            __rand48_Mult[2] * xseed[0];
    xseed[0] = temp[0];
    xseed[1] = temp[1];
    xseed[2] = (unsigned short) accu;
}
 
    extern void
srand48(long seed) __THROW
{
    __rand48_Seed[0] = RAND48_SEED_0;
    __rand48_Seed[1] = (unsigned short) seed;
    __rand48_Seed[2] = (unsigned short) (seed >> 16);
    __rand48_Mult[0] = RAND48_MULT_0;
    __rand48_Mult[1] = RAND48_MULT_1;
    __rand48_Mult[2] = RAND48_MULT_2;
    __rand48_Add = RAND48_ADD;
}
 
    extern unsigned short *
seed48(unsigned short xseed[3]) __THROW
{
    static unsigned short sseed[3];
 
    sseed[0] = __rand48_Seed[0];
    sseed[1] = __rand48_Seed[1];
    sseed[2] = __rand48_Seed[2];
    __rand48_Seed[0] = xseed[0];
    __rand48_Seed[1] = xseed[1];
    __rand48_Seed[2] = xseed[2];
    __rand48_Mult[0] = RAND48_MULT_0;
    __rand48_Mult[1] = RAND48_MULT_1;
    __rand48_Mult[2] = RAND48_MULT_2;
    __rand48_Add = RAND48_ADD;
    return sseed;
}
    
    extern long
nrand48(unsigned short xseed[3]) __THROW
{
    _dorand48(xseed);
    return ((long) xseed[2] << 15) + ((long) xseed[1] >> 1);
}
    extern long
mrand48(void) __THROW
{
    _dorand48(__rand48_Seed);
    return ((long) __rand48_Seed[2] << 16) + (long) __rand48_Seed[1];
}
 
    extern long
lrand48(void) __THROW
{
    _dorand48(__rand48_Seed);
    return ((long) __rand48_Seed[2] << 15) + ((long) __rand48_Seed[1] >> 1);
}
 
    extern void
lcong48(unsigned short p[7]) __THROW
{
    __rand48_Seed[0] = p[0];
    __rand48_Seed[1] = p[1];
    __rand48_Seed[2] = p[2];
    __rand48_Mult[0] = p[3];
    __rand48_Mult[1] = p[4];
    __rand48_Mult[2] = p[5];
    __rand48_Add = p[6];
}
    extern long
jrand48(unsigned short xseed[3]) __THROW
{
    _dorand48(xseed);
    return ((long) xseed[2] << 16) + (long) xseed[1];
}
 
    extern double
erand48(unsigned short xseed[3]) __THROW
{
    _dorand48(xseed);
    return ldexp((double) xseed[0], -48) +
           ldexp((double) xseed[1], -32) +
           ldexp((double) xseed[2], -16);
}
 
    extern double
drand48(void) __THROW
{
    return erand48(__rand48_Seed);
}
 
#endif