Random.cpp

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/*  Project nGenEx
        Destroyer Studios LLC
        Copyright © 1997-2004. All Rights Reserved.

        SUBSYSTEM:    nGenEx.lib
        FILE:         Random.cpp
        AUTHOR:       John DiCamillo


        OVERVIEW
        ========
        Utility functions for generating random numbers and locations.
*/

#include "MemDebug.h"
#include "Random.h"

// +----------------------------------------------------------------------+

void RandomInit()
{
        srand(timeGetTime());
}

// +----------------------------------------------------------------------+

Point RandomDirection()
{
        Point p = Point(rand() - 16384, rand() - 16384, 0);
        p.Normalize();
        return p;
}

// +----------------------------------------------------------------------+

Point RandomPoint()
{
        Point p = Point(rand() - 16384, rand() - 16384, 0);
        p.Normalize();
        p *= 15e3 + rand()/3;
        return p;
}

// +----------------------------------------------------------------------+

Vec3 RandomVector(double radius)
{
        Vec3 v = Vec3(rand() - 16384, rand() - 16384, rand() - 16384);
        v.Normalize();

        if (radius > 0)
        v *= (float) radius;
        else
        v *= (float) Random(radius/3, radius);

        return v;
}

// +----------------------------------------------------------------------+

double Random(double min, double max)
{
        double delta = max - min;
        double r     = delta * rand() / 32768.0;

        return min + r;
}

// +----------------------------------------------------------------------+

int RandomIndex()
{
        static int index     = 0;
        static int table[16] = { 0, 9, 4, 7, 14, 11, 2, 12, 1, 5, 13, 8, 6, 10, 3, 15 };

        int r = 1 + ((rand() & 0x0700) >> 8);
        index += r;
        if (index > 1e7) index = 0;
        return table[index % 16];
}

// +----------------------------------------------------------------------+

bool RandomChance(int wins, int tries)
{
        double fraction = 256.0 * wins / tries;
        double r        = (rand() >> 4) & 0xFF;

        return r < fraction;
}

// +----------------------------------------------------------------------+

int RandomSequence(int current, int range)
{
        if (range > 1) {
                int step = (int) Random(1, range-1);
                return (current + step) % range;
        }

        return current;
}

// +----------------------------------------------------------------------+

int RandomShuffle(int count)
{
        static int  set_size = -1;
        static BYTE set[256];
        static int  index    = -1;

        if (count < 0 || count > 250)
        return 0;

        if (set_size != count) {
                set_size = count;
                index    = -1;
        }

        // need to reshuffle
        if (index < 0 || index > set_size-1) {
                // set up the deck
                int tmp[256];
                for (int i = 0; i < 256; i++)
                tmp[i] = i;

                // shuffle the cards
                for (int i = 0; i < set_size; i++) {
                        int n     = (int) Random(0, set_size);
                        int tries = set_size;
                        while (tmp[n] < 0 && tries--) {
                                n = (n+1) % set_size;
                        }

                        if (tmp[n] >= 0) {
                                set[i] = tmp[n];
                                tmp[n] = -1;
                        }
                        else {
                                set[i] = 0;
                        }
                }

                index = 0;
        }

        return set[index++];
}