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/*
** weightedlist.h
** A weighted list template class
**
**---------------------------------------------------------------------------
** Copyright 1998-2006 Randy Heit
** All rights reserved.
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions
** are met:
**
** 1. Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
** 2. Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in the
** documentation and/or other materials provided with the distribution.
** 3. The name of the author may not be used to endorse or promote products
** derived from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
**---------------------------------------------------------------------------
**
*/
#include <stdlib.h>
#include "doomtype.h"
class FRandom;
template<class T>
class TWeightedList
{
template<class U>
struct Choice
{
Choice(WORD w, U v) : Next(NULL), Weight(w), RandomVal(0), Value(v) {}
Choice<U> *Next;
WORD Weight;
BYTE RandomVal; // 0 (never) - 255 (always)
T Value;
};
public:
TWeightedList (FRandom &pr) : Choices (NULL), RandomClass (pr) {}
~TWeightedList ()
{
Choice<T> *choice = Choices;
while (choice != NULL)
{
Choice<T> *next = choice->Next;
delete choice;
choice = next;
}
}
void AddEntry (T value, WORD weight);
T PickEntry () const;
void ReplaceValues (T oldval, T newval);
private:
Choice<T> *Choices;
FRandom &RandomClass;
void RecalcRandomVals ();
TWeightedList &operator= (const TWeightedList &) { return *this; }
};
template<class T>
void TWeightedList<T>::AddEntry (T value, WORD weight)
{
if (weight == 0)
{ // If the weight is 0, don't bother adding it,
// since it will never be chosen.
return;
}
Choice<T> **insAfter = &Choices, *insBefore = Choices;
Choice<T> *theNewOne;
while (insBefore != NULL && insBefore->Weight < weight)
{
insAfter = &insBefore->Next;
insBefore = insBefore->Next;
}
theNewOne = new Choice<T> (weight, value);
*insAfter = theNewOne;
theNewOne->Next = insBefore;
RecalcRandomVals ();
}
template<class T>
T TWeightedList<T>::PickEntry () const
{
BYTE randomnum = RandomClass();
Choice<T> *choice = Choices;
while (choice != NULL && randomnum > choice->RandomVal)
{
choice = choice->Next;
}
return choice != NULL ? choice->Value : NULL;
}
template<class T>
void TWeightedList<T>::RecalcRandomVals ()
{
// Redistribute the RandomVals so that they form the correct
// distribution (as determined by the range of weights).
int numChoices, weightSums;
Choice<T> *choice;
double randVal, weightDenom;
if (Choices == NULL)
{ // No choices, so nothing to do.
return;
}
numChoices = 1;
weightSums = 0;
for (choice = Choices; choice->Next != NULL; choice = choice->Next)
{
++numChoices;
weightSums += choice->Weight;
}
weightSums += choice->Weight;
choice->RandomVal = 255; // The last choice is always randomval 255
randVal = 0.0;
weightDenom = 1.0 / (double)weightSums;
for (choice = Choices; choice->Next != NULL; choice = choice->Next)
{
randVal += (double)choice->Weight * weightDenom;
choice->RandomVal = (BYTE)(randVal * 255.0);
}
}
// Replace all values that match oldval with newval
template<class T>
void TWeightedList<T>::ReplaceValues(T oldval, T newval)
{
Choice<T> *choice;
for (choice = Choices; choice != NULL; choice = choice->Next)
{
if (choice->Value == oldval)
{
choice->Value = newval;
}
}
}
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