com.lastcalc.engines.RecentFirstParserPickerFactory.java Source code

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Here is the source code for com.lastcalc.engines.RecentFirstParserPickerFactory.java

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/*******************************************************************************
 * LastCalc - The last calculator you'll ever need
 * Copyright (C) 2011, 2012 Uprizer Labs LLC
 * 
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Affero General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program 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 Affero General Public License for more
 * details.
 ******************************************************************************/
package com.lastcalc.engines;

import java.util.*;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import com.google.common.collect.*;

import com.lastcalc.parsers.*;

public class RecentFirstParserPickerFactory extends ParserPickerFactory {

    ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();

    private static final long serialVersionUID = -5521465155099741906L;

    LinkedList<Parser> parsers = new LinkedList<Parser>();

    private final int maxParsers;

    public RecentFirstParserPickerFactory(final Iterable<Parser> parsers) {
        this(parsers, Integer.MAX_VALUE);
    }

    public RecentFirstParserPickerFactory(final Iterable<Parser> parsers, final int maxParsers) {
        this.maxParsers = maxParsers;
        Iterables.addAll(this.parsers, parsers);
        while (this.parsers.size() > maxParsers) {
            this.parsers.removeLast();
        }
    }

    @Override
    public void addParser(final Parser parser) {
        parsers.add(parser);
    }

    @Override
    public void teach(final Iterable<ParseStep> steps) {
        final ArrayList<ParseStep> reversed = Lists.newArrayList(steps);
        Collections.reverse(reversed);
        rwl.writeLock().lock();
        for (final ParseStep ps : reversed) {
            // TODO: This is slow, probably need to use a better
            // datastructure for parsers, perhaps LinkedHashMap
            // or something
            parsers.remove(ps.parser);
            parsers.addFirst(ps.parser);
        }
        while (parsers.size() > maxParsers) {
            parsers.removeLast();
        }
        rwl.writeLock().unlock();
    }

    @Override
    public ParserPicker getPicker(final Map<Attempt, Integer> prevAttemptPos) {
        return new ParserPicker(prevAttemptPos) {

            @Override
            public ParseStep pickNext(final ParserContext context, final ParseStep previous) {
                // matchTemplate
                rwl.readLock().lock();
                final ParseStep nextParseStep = getNext(context, parsers, previous);
                rwl.readLock().unlock();
                return nextParseStep;
            }
        };
    }

    @Override
    public List<Parser> getParsers() {
        return parsers;
    }

}