FilterParamIndexCompareString.java

/**************************************************************************************
 * Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 * http://esper.codehaus.org                                                          *
 * http://www.espertech.com                                                           *
 * ---------------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the GPL license       *
 * a copy of which has been included with this distribution in the license.txt file.  *
 **************************************************************************************/
package com.espertech.esper.filter;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.client.EventPropertyGetter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.Collection;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * Index for filter parameter constants for the comparison operators (less, greater, etc).
 * The implementation is based on the SortedMap implementation of TreeMap.
 * The index only accepts String constants. It keeps a lower and upper bounds of all constants in the index
 * for fast range checking, since the assumption is that frequently values fall within a range.
 */
public final class FilterParamIndexCompareString extends FilterParamIndexLookupableBase
{
    private final TreeMap<Object, EventEvaluator> constantsMap;
    private final ReadWriteLock constantsMapRWLock;

    public FilterParamIndexCompareString(FilterSpecLookupable lookupable, FilterOperator filterOperator) {
        super(filterOperator, lookupable);

        constantsMap = new TreeMap<Object, EventEvaluator>();
        constantsMapRWLock = new ReentrantReadWriteLock();

        if ((filterOperator != FilterOperator.GREATER) &&
            (filterOperator != FilterOperator.GREATER_OR_EQUAL) &&
            (filterOperator != FilterOperator.LESS) &&
            (filterOperator != FilterOperator.LESS_OR_EQUAL))
        {
            throw new IllegalArgumentException("Invalid filter operator for index of " + filterOperator);
        }
    }

    public final EventEvaluator get(Object filterConstant)
    {
        return constantsMap.get(filterConstant);
    }

    public final void put(Object filterConstant, EventEvaluator matcher)
    {
        constantsMap.put(filterConstant, matcher);
    }

    public final boolean remove(Object filterConstant)
    {
        if (constantsMap.remove(filterConstant) == null)
        {
            return false;
        }

        return true;
    }

    public final int size()
    {
        return constantsMap.size();
    }

    public final ReadWriteLock getReadWriteLock()
    {
        return constantsMapRWLock;
    }

    public final void matchEvent(EventBean theEvent, Collection<FilterHandle> matches)
    {
        Object propertyValue = lookupable.getGetter().get(theEvent);

        if (propertyValue == null)
        {
            return;
        }

        FilterOperator filterOperator = this.getFilterOperator();

        // Look up in table
        constantsMapRWLock.readLock().lock();
        try {

            // Get the head or tail end of the map depending on comparison type
            Map<Object, EventEvaluator> subMap;

            if ((filterOperator == FilterOperator.GREATER) ||
                (filterOperator == FilterOperator.GREATER_OR_EQUAL))
            {
                // At the head of the map are those with a lower numeric constants
                subMap = constantsMap.headMap(propertyValue);
            }
            else
            {
                subMap = constantsMap.tailMap(propertyValue);
            }

            // All entries in the subMap are elgibile, with an exception
            EventEvaluator exactEquals = null;
            if (filterOperator == FilterOperator.LESS)
            {
                exactEquals = constantsMap.get(propertyValue);
            }

            for (EventEvaluator matcher : subMap.values())
            {
                // For the LESS comparison type we ignore the exactly equal case
                // The subMap is sorted ascending, thus the exactly equals case is the first
                if (exactEquals != null)
                {
                    exactEquals = null;
                    continue;
                }

                matcher.matchEvent(theEvent, matches);
            }

            if (filterOperator == FilterOperator.GREATER_OR_EQUAL)
            {
                EventEvaluator matcher = constantsMap.get(propertyValue);
                if (matcher != null)
                {
                    matcher.matchEvent(theEvent, matches);
                }
            }
        }
        finally {
            constantsMapRWLock.readLock().unlock();
        }
    }

    private static final Log log = LogFactory.getLog(FilterParamIndexCompareString.class);
}