RandomGenerator.cpp

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////////////////////////////////////////////////////////////////////////////////
//    Scorched3D (c) 2000-2009
//
//    This file is part of Scorched3D.
//
//    Scorched3D 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.
//
//    Scorched3D 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 Scorched3D; if not, write to the Free Software
//    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
////////////////////////////////////////////////////////////////////////////////

#include <common/RandomGenerator.h>
#include <common/Defines.h>
#include <net/NetBuffer.h>
#include <stdlib.h>
#include <stdio.h>

// Yes you guessed it, a really sucky way to create cross platform
// random numbers.  Store them in a file and read them in each system!

unsigned int RandomGenerator::bufferSize_ = 0;
unsigned int *RandomGenerator::buffer_ = 0;

RandomGenerator::RandomGenerator() :
        position_(0)
{
        // Cache the buffer so we only read it once
        // We can create many random generators easily now
        if (!buffer_)
        {
                std::string fileName = S3D::getDataFile("data/random.no");
                FILE *in = fopen(fileName.c_str(), "rb");
                DIALOG_ASSERT(in);
                bufferSize_= 100000;
                unsigned int *tmpbuffer = new unsigned int[bufferSize_];
                int size = fread(tmpbuffer, sizeof(unsigned int), bufferSize_, in);
                fclose(in);     
                DIALOG_ASSERT(size == bufferSize_);

                buffer_ = new unsigned int[bufferSize_];
                for (unsigned int i=0; i<bufferSize_; i++)
                {
                        unsigned int value = tmpbuffer[i];
                        buffer_[i] = SDLNet_Read32(&value);
                }
                delete [] tmpbuffer;
        }
}

RandomGenerator::~RandomGenerator()
{
}

void RandomGenerator::seed(unsigned int seed)
{
        position_ = seed;
}

unsigned int RandomGenerator::getSeed()
{
        return position_;
}

unsigned int RandomGenerator::getRandUInt()
{
        unsigned int pos = position_ % bufferSize_;
        position_++;

        unsigned int maskpos = (position_ / bufferSize_) % 32;
        unsigned int value = buffer_[pos];
        unsigned int lvalue = value << (32 - maskpos);
        unsigned int rvalue = value >> maskpos;
        return lvalue | rvalue;
}

fixed RandomGenerator::getRandFixed()
{
        unsigned int rd = getRandUInt();
        unsigned int fract = rd % 10000;
        fixed result(true, fract);

        return result;
}

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