EventConfigCache.java

/*******************************************************************************
 * Copyright (c) 2008, 2009 Red Hat, Inc.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Kent Sebastian <ksebasti@redhat.com> - initial API and implementation
 *
 *******************************************************************************/
package org.eclipse.linuxtools.internal.oprofile.launch.configuration;

import java.util.HashMap;

import org.eclipse.linuxtools.internal.oprofile.core.Oprofile;

/**
 * Cache class for event configuration. Currently only used to cache the results
 * of an `opxml check-event ..` run, since the isValid() method in the EventConfigTab
 * needlessly spawns opxml dozens of times with the same values. Note that multiple
 * checks of the same value will necessarily return the same result (for a given
 * processor) so there is no worry of an invalid cache entry.
 */
public class EventConfigCache {
    //a cache entry for an event check, used as the hashmap key
    static class CheckEventEntry {
        public Integer counterNum, maskValue;
        public String eventName;

        public CheckEventEntry(int counterNum, String eventName, int maskValue) {
            this.counterNum = Integer.valueOf(counterNum);
            this.eventName = eventName;
            this.maskValue = Integer.valueOf(maskValue);
        }

        @Override
        public boolean equals(Object obj) {
            if (obj instanceof CheckEventEntry) {
                CheckEventEntry other = (CheckEventEntry)obj;
                return (counterNum.equals(other.counterNum) && eventName.equals(other.eventName) && maskValue.equals(other.maskValue));
            } else {
                return false;
            }
        }

        @Override
        public int hashCode() {
            int prime = 11, result = 3;
            result = prime*result + counterNum.hashCode();
            result = prime*result + eventName.hashCode();
            result = prime*result + maskValue.hashCode();
            return result;
        }
    }

    HashMap<CheckEventEntry, Boolean> validEventCache;

    /**
     * Default constructor, creates an empty cache.
     */
    public EventConfigCache() {
        validEventCache = new HashMap<>();
    }

    /**
     * Method to be used to check the validity of an event. Will check
     * the cache for the result of a previous check of the same values,
     * or otherwise will spawn opxml to check properly.
     * @param counter counter number
     * @param event event name
     * @param mask unit mask value
     * @return true or false, depending if the event config is valid
     */
    public boolean checkEvent(int counter, String event, int mask) {
        CheckEventEntry e = new CheckEventEntry(counter, event, mask);
        Boolean result = null;

        result = validEventCache.get(e);

        if (result == null) {
            //not in the map, get its value and add it in
            result = Oprofile.checkEvent(counter, event, mask);

            //possible to be null if there is no opxmlProvider
            if (result != null) {
                validEventCache.put(e, result);
            }
        }

        return (result == null ? false : result);
    }
}