/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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 * 
 * The contents of this file are subject to the terms of either the GNU
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 * and Distribution License("CDDL") (collectively, the "License").  You
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 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
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 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
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package com.sun.enterprise.web.connector.grizzly;

import java.io.IOException;
import java.nio.channels.Selector;
import java.util.EmptyStackException;
import java.util.Stack;

/**
 * Factory used to dispatch/share <code>Selector</code>.
 *
 * @author Scott Oaks
 * @author Jean-Francois Arcand
 */
public class SelectorFactory{
    
    /**
     * The timeout before we exit.
     */
    protected static long timeout = 5000;
    
    
    /**
     * The number of <code>Selector</code> to create.
     */
    protected static int maxSelectors = 20;
    
    
    /**
     * Cache of <code>Selector</code>
     */
    private final static Stack<Selector> selectors = new Stack<Selector>();
    
    
    /**
     * Creates the <code>Selector</code>
     */
    static {
        try{
            for (int i = 0; i < maxSelectors; i++) 
                selectors.add(Selector.open());
        } catch (IOException ex){
            ; // do nothing.
        }
    }

    
    /**
     * Get a exclusive <code>Selector</code>
     */
    public final static Selector getSelector() {
        synchronized(selectors) {
            Selector s = null;
            try {
                if ( selectors.size() != 0 )
                    s = selectors.pop();
            } catch (EmptyStackException ex){}
                       
            int attempts = 0;
            try{
                while (s == null && attempts < 2) {
                    selectors.wait(timeout);
                    try {
                        if ( selectors.size() != 0 )
                            s = selectors.pop();
                    } catch (EmptyStackException ex){
                        break;
                    }
                    attempts++;
                }
            } catch (InterruptedException ex){};
            return s;
        }
    }


    /**
     * Return the <code>Selector</code> to the cache
     */
    public final static void returnSelector(Selector s) {
        synchronized(selectors) {
            selectors.push(s);
            if (selectors.size() == 1)
                selectors.notify();
        }
    }

}