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This artifact contains the API of AutomataLib, which mainly consists of interfaces for the various concepts and automaton models supported by the AutomataLib core. In addition to that, it also defines some fundamental classes for dealing with words of symbols.
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/* Copyright (C) 2013 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 * 
 * AutomataLib is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 3.0 as published by the Free Software Foundation.
 * 
 * AutomataLib 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with AutomataLib; if not, see
 * http://www.gnu.de/documents/lgpl.en.html.
 */
package net.automatalib.words;

import java.util.List;


/**
 * An immutable word implementation that is based on the idea of a common array storage.
 * This allows a very efficient creation of subwords (e.g., prefixes and suffixes).
 * 
 * @author Malte Isberner 
 *
 * @param  input symbol class
 */
final class SharedWord extends Word {
	
	/**
	 * Iterator for iterating over {@link SharedWord}s.
	 * 
	 * @author Malte Isberner 
	 *
	 * @param  symbol class.
	 */
	private static final class Iterator implements java.util.ListIterator {
		
		private final Object[] storage;
		private final int startIdx, endIdx;
		private int currIdx;
		
		public Iterator(SharedWord word) {
			this(word, 0);
		}
		
		public Iterator(SharedWord word, int index) {
			this.storage = word.storage;
			this.startIdx = word.offset;
			this.currIdx = word.offset + index;
			this.endIdx = word.offset + word.length;
		}

		@Override
		public boolean hasNext() {
			return (currIdx < endIdx);
		}

		@Override
		@SuppressWarnings("unchecked")
		public I next() {
			return (I)storage[currIdx++];
		}

		@Override
		public void remove() {
			throw new UnsupportedOperationException("SharedWord does not support removal of elements");
		}

		@Override
		public boolean hasPrevious() {
			return (currIdx > startIdx);
		}

		@Override
		@SuppressWarnings("unchecked")
		public I previous() {
			return (I)storage[--currIdx];
		}

		@Override
		public int nextIndex() {
			return currIdx - startIdx;
		}

		@Override
		public int previousIndex() {
			return currIdx - startIdx - 1;
		}

		@Override
		public void set(I e) {
			throw new UnsupportedOperationException("SharedWord does not support modification");
		}

		@Override
		public void add(I e) {
			throw new UnsupportedOperationException("SharedWord does not support modification");
		}
		
	}
	
	private final Object[] storage;
	private final int offset;
	private final int length;
	
	/**
	 * Constructor.
	 * @param storage
	 */
	public SharedWord(Object[] storage) {
		this(storage, 0, storage.length);
	}
	
	public SharedWord(Object[] storage, int offset, int length) {
		this.storage = storage;
		this.offset = offset;
		this.length = length;
	}
	
	/**
	 * Constructor. Creates a {@link SharedWord} from a {@link List} of input symbols.
	 * @param other the list of input symbols.
	 */
	public SharedWord(List other) {
		this.storage = other.toArray();
		this.offset = 0;
		this.length = other.size();
	}

	/*
	 * (non-Javadoc)
	 * @see de.ls5.words.Word#getSymbol(int)
	 */
	@Override
	@SuppressWarnings("unchecked")
	public I getSymbol(int index) {
		return (I)storage[offset+index];
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#length()
	 */
	@Override
	public int length() {
		return this.length;
	}
	
	
	/*
	 * (non-Javadoc)
	 * @see de.ls5.words.Word#subWord(int, int)
	 */
	@Override
	public Word _subWord(int fromIndex, int toIndex) {
		int newOfs = offset + fromIndex;
		int newLen = toIndex - fromIndex;
		if(newLen <= 0)
			return Word.epsilon();
		if(newOfs + newLen > storage.length)
			return Word.epsilon();
		return new SharedWord<>(storage, newOfs, newLen);
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#writeToArray(int, java.lang.Object[], int, int)
	 */
	@Override
	public void writeToArray(int offset, Object[] array, int tgtOfs, int num) {
		System.arraycopy(storage, this.offset + offset, array, tgtOfs, num);
	}
	
	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#lastSymbol()
	 */
	@Override
	@SuppressWarnings("unchecked")
	public I lastSymbol() {
		return (I)storage[length-1];
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#iterator()
	 */
	@Override
	public Iterator iterator() {
		return new Iterator<>(this);
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#flatten()
	 */
	@Override
	public Word flatten() {
		return this;
	}
	
	
	@Override
	public Word trimmed() {
		if(offset == 0 && length == storage.length)
			return this;
		Object[] trimmed = new Object[length];
		System.arraycopy(storage, offset, trimmed, 0, length);
		return new SharedWord<>(trimmed);
	}
}