org.springframework.ide.eclipse.boot.dash.util.CancelationTokens.java Source code

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Here is the source code for org.springframework.ide.eclipse.boot.dash.util.CancelationTokens.java

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/*******************************************************************************
 * Copyright (c) 2016 Pivotal, 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
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Pivotal, Inc. - initial API and implementation
 *******************************************************************************/
package org.springframework.ide.eclipse.boot.dash.util;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IProgressMonitor;

/**
 * Manages a set of CancelationTokens.
 *
 * @author Kris De Volder
 */
public class CancelationTokens {

    private String DEBUG = null;

    //Note: we don't actually have to keep a set of tokens explicitly.
    // The tokens use a 'id' which is incremented on each new token.
    //So it is easy to cancel all existing tokens based on a their
    //id simply by remembering the 'id' where the cancelation
    //occurred. All ids 'older' than the current id are 'canceled'.

    /**
     * An uncancelable token that can be used by operations that don't
     * need cancelation support.
     */
    public static final CancelationToken NULL = new CancelationToken() {
        @Override
        public boolean isCanceled() {
            return false;
        }
    };

    private final Object SYNC = CancelationTokens.this;

    private int canceledAllBefore = 0;
    private int nextId = 0;

    public CancelationTokens() {
    }

    public CancelationTokens(String debug) {
        this.DEBUG = debug;
    }

    public interface CancelationToken {
        boolean isCanceled();
    }

    public synchronized CancelationToken create() {
        CancelationToken token = new ManagedToken();
        debug("creating cancelation token: " + token);
        return token;
    }

    private class ManagedToken implements CancelationToken {
        private int id;

        private ManagedToken() {
            synchronized (SYNC) {
                this.id = nextId++;
            }
        }

        public boolean isCanceled() {
            synchronized (SYNC) {
                boolean isCanceled = id < canceledAllBefore;
                debug("isCanceled? [" + id + "] => " + isCanceled);
                return isCanceled;
            }
        }

        @Override
        public String toString() {
            return "CancelToken(" + id + ")";
        }
    }

    public synchronized void cancelAllBefore(CancelationToken token) {
        Assert.isLegal(token instanceof ManagedToken);
        canceledAllBefore = Math.max(canceledAllBefore, ((ManagedToken) token).id);
        debug("CancelationTokens < " + canceledAllBefore + " are Canceled");
    }

    public void cancelAll() {
        canceledAllBefore = nextId;
        debug("CancelationTokens < " + canceledAllBefore + " are Canceled");
    }

    private void debug(String string) {
        if (DEBUG != null) {
            System.out.println(DEBUG + ": " + string);
        }
    }

    public static CancelationToken merge(CancelationToken cancelationToken, IProgressMonitor monitor) {
        return new CancelationToken() {
            @Override
            public boolean isCanceled() {
                return cancelationToken.isCanceled() || monitor.isCanceled();
            }
        };
    }
}