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