Quadcap Embeddable Server

com/quadcap/util/threads/Stream.java

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package com.quadcap.util.threads;

/* Copyright 1997 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.util.Vector;

import com.quadcap.util.Debug;
import com.quadcap.util.DList;
import com.quadcap.util.DListItem;
import com.quadcap.util.ListException;

/**
 * This class implements a thread-safe stream data structure, where the
 * stream has a fixed-size buffer of Objects.
 *
 * @author Stan Bailes
 */
public class Stream {
    int                         maxSize                 = 10;
    DList                       queue                   = new DList();
    boolean                     full                    = false;
    boolean                     closed                  = false;

    /**
     * Construct a new stream using defaults
     */
    public Stream() {}

    /**
     * Construct a new stream with a specified buffer size.
     *
     * @param maxSize the maximum number of items to buffer.
     */
    public Stream(int maxSize) {
        this.maxSize = maxSize;
    }

    /**
     * Return the next item from the stream.  Block if the stream's empty.
     *
     * @return the next stream item.
     */
    public Object read() {
        Object obj = null;
        synchronized (queue) {
            while (queue.size() == 0) {
                if (closed) {
                    return new RuntimeException("stream closed");
                }
                try {
                    queue.wait();
                    if (closed) throw new RuntimeException("stream closed");
                } catch (InterruptedException e) {
                    Debug.print(e);
                }
            }
            try {
                DListItem d = queue.popFront();
                obj = d.obj;
            } catch (ListException e) {
                Debug.print(e);
            }
            if (full) {
                full = false;
                queue.notifyAll();
            }
        }
        return obj;
    }

    /**
     * Write an item to the stream.  Block if the stream buffer is full.
     *
     * @param obj the object to write to the stream.
     */
    public void write(Object obj) {
        synchronized (queue) {
            while (queue.size() >= maxSize) {
                if (closed) {
                    throw new RuntimeException("stream closed");
                }
                full = true;
                try {
                    queue.wait();
                } catch (InterruptedException e) {
                    Debug.print(e);
                }
            }
            queue.addBack(obj);
            if (queue.size() == 1) queue.notifyAll();
        }
    }

    /**
     * Close this stream.
     */
    public void close() {
        synchronized (queue) {
            closed = true;
            queue.notifyAll();
        }
    }
}