/*
 *  Baltisot
 *  Copyright (C) 1999-2008 Nicolas "Pixel" Noble
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/* $Id: RandISAAC.cc,v 1.3 2008-07-22 14:34:15 pixel Exp $ */

/* Based on ISAAC. See original (C) mention below. */

/*
------------------------------------------------------------------------------
rand.c: By Bob Jenkins.  My random number generator, ISAAC.  Public Domain
MODIFIED:
  960327: Creation (addition of randinit, really)
  970719: use context, not global variables, for internal state
  980324: make a portable version
  010626: Note this is public domain
------------------------------------------------------------------------------
*/

#include <stdio.h>
#include <time.h>

#include <RandISAAC.h>

#define ind(mm,x)  ((mm)[(x>>2)&(RANDSIZ-1)])
#define rngstep(mix,a,b,mm,m,m2,r,x) \
{ \
  x = *m;  \
  a = ((a^(mix)) + *(m2++)) & 0xffffffff; \
  *(m++) = y = (ind(mm,x) + a + b) & 0xffffffff; \
  *(r++) = b = (ind(mm,y>>RANDSIZL) + x) & 0xffffffff; \
}

void Random::isaac()
{
    Uint32 a, b, x, y, *m, *mm, *m2, *r, *mend;

    mm = randmem;
    r = randrsl;
    a = randa;
    b = (randb + (++randc)) & 0xffffffff;
    for (m = mm, mend = m2 = m + (RANDSIZ / 2); m < mend;) {
        rngstep(a << 13, a, b, mm, m, m2, r, x);
        rngstep(a >> 6, a, b, mm, m, m2, r, x);
        rngstep(a << 2, a, b, mm, m, m2, r, x);
        rngstep(a >> 16, a, b, mm, m, m2, r, x);
    }
    for (m2 = mm; m2 < mend;) {
        rngstep(a << 13, a, b, mm, m, m2, r, x);
        rngstep(a >> 6, a, b, mm, m, m2, r, x);
        rngstep(a << 2, a, b, mm, m, m2, r, x);
        rngstep(a >> 16, a, b, mm, m, m2, r, x);
    }
    randb = b;
    randa = a;
}

#define mix(a,b,c,d,e,f,g,h) \
{ \
   a^=b<<11; d+=a; b+=c; \
   b^=c>>2;  e+=b; c+=d; \
   c^=d<<8;  f+=c; d+=e; \
   d^=e>>16; g+=d; e+=f; \
   e^=f<<10; h+=e; f+=g; \
   f^=g>>4;  a+=f; g+=h; \
   g^=h<<8;  b+=g; h+=a; \
   h^=a>>9;  c+=h; a+=b; \
}

/*
 * if (flag==TRUE), then use the contents of randrsl[] to initialize mm[]. 
 */
void Random::randinit(int flag)
{
    int i;

    Uint32 a, b, c, d, e, f, g, h;

    Uint32 *m, *r;

    randa = randb = randc = 0;
    m = randmem;
    r = randrsl;
    a = b = c = d = e = f = g = h = 0x9e3779b9; /* the golden ratio */

    for (i = 0; i < 4; ++i) {   /* scramble it */
        mix(a, b, c, d, e, f, g, h);
    }

    if (flag) {
       /*
        * initialize using the contents of r[] as the seed 
        */
        for (i = 0; i < RANDSIZ; i += 8) {
            a += r[i];
            b += r[i + 1];
            c += r[i + 2];
            d += r[i + 3];
            e += r[i + 4];
            f += r[i + 5];
            g += r[i + 6];
            h += r[i + 7];
            mix(a, b, c, d, e, f, g, h);
            m[i] = a;
            m[i + 1] = b;
            m[i + 2] = c;
            m[i + 3] = d;
            m[i + 4] = e;
            m[i + 5] = f;
            m[i + 6] = g;
            m[i + 7] = h;
        }
       /*
        * do a second pass to make all of the seed affect all of m 
        */
        for (i = 0; i < RANDSIZ; i += 8) {
            a += m[i];
            b += m[i + 1];
            c += m[i + 2];
            d += m[i + 3];
            e += m[i + 4];
            f += m[i + 5];
            g += m[i + 6];
            h += m[i + 7];
            mix(a, b, c, d, e, f, g, h);
            m[i] = a;
            m[i + 1] = b;
            m[i + 2] = c;
            m[i + 3] = d;
            m[i + 4] = e;
            m[i + 5] = f;
            m[i + 6] = g;
            m[i + 7] = h;
        }
    } else {
        for (i = 0; i < RANDSIZ; i += 8) {
           /*
            * fill in mm[] with messy stuff 
            */
            mix(a, b, c, d, e, f, g, h);
            m[i] = a;
            m[i + 1] = b;
            m[i + 2] = c;
            m[i + 3] = d;
            m[i + 4] = e;
            m[i + 5] = f;
            m[i + 6] = g;
            m[i + 7] = h;
        }
    }

    isaac();                    /* fill in the first set of results */
    randcnt = RANDSIZ;          /* prepare to use the first set of results */
}

Random::Random() {
    int i;

    srand(time(NULL));
    for (i = 0; i < RANDSIZ; i++) {
        randrsl[i] = rand();
    }
    randinit(1);
}

Random::~Random() {
}

Uint32 Random::get() {
    if (!randcnt--) {
        isaac();
        randcnt = RANDSIZ - 1;
    }
    return randrsl[randcnt];
}