001    /**
002     * Copyright (c) 2008-2009 Apple Inc. All rights reserved.
003     * Copyright (C) 2012 FuseSource, Inc.
004     * http://fusesource.com
005     *
006     * Licensed under the Apache License, Version 2.0 (the "License");
007     * you may not use this file except in compliance with the License.
008     * You may obtain a copy of the License at
009     *
010     *    http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.fusesource.hawtdispatch;
020    
021    /**
022     * <p>
023     * A dispatch source is used to monitor low-level system objects and
024     * automatically submit a handler runnable to a dispatch queue in response
025     * to events.
026     * </p><p>
027     * Dispatch sources are not reentrant. Any events received while the dispatch
028     * source is suspended or while the event handler runnable is currently executing
029     * will be coalesced and delivered after the dispatch source is resumed or the
030     * event handler runnable has returned.
031     * </p><p>
032     * Dispatch sources are created in a suspended state. After creating the
033     * source and setting any desired attributes (i.e. the handlers),
034     * a call must be made to the dispatch source's <code>resume()</code> method
035     * in order to begin event delivery.
036     * </p>
037     *
038     * @author <a href="http://hiramchirino.com">Hiram Chirino</a>
039     */
040    public interface DispatchSource extends DispatchObject {
041    
042        /**
043         * <p>
044         * Sets the cancellation handler runnable for the given dispatch source.
045         * </p><p>
046         * The cancellation handler (if specified) will be submitted to the source's
047         * target queue in response to a call to {@link #cancel()} once the
048         * system has released all references to the source's underlying handle and
049         * the source's event handler runnable has returned.
050         * </p>
051         *
052         * @param handler
053         * The cancellation handler runnable to submit to the source's target queue.
054         */
055        public void setCancelHandler(Runnable handler);
056    
057        /**
058         * <p>
059         * Sets the event handler runnable of this dispatch source.
060         * </p>
061         *
062         * @param handler
063         * The event handler runnable to submit to the source's target queue.
064         */
065        public void setEventHandler(Runnable handler);
066    
067        /**
068         * <p>
069         * Sets the cancellation handler task for the given dispatch source.
070         * </p><p>
071         * The cancellation handler (if specified) will be submitted to the source's
072         * target queue in response to a call to {@link #cancel()} once the
073         * system has released all references to the source's underlying handle and
074         * the source's event handler runnable has returned.
075         * </p>
076         *
077         * @param task
078         * The cancellation handler runnable to submit to the source's target queue.
079         */
080        public void setCancelHandler(Task task);
081    
082        /**
083         * <p>
084         * Sets the event handler task of this dispatch source.
085         * </p>
086         *
087         * @param task
088         * The event handler runnable to submit to the source's target queue.
089         */
090        public void setEventHandler(Task task);
091    
092        /**
093         * <p>
094         * Asynchronously cancel the dispatch source, preventing any further invocation
095         * of its event handler runnable.
096         * </p><p>
097         * Cancellation prevents any further invocation of the event handler runnable for
098         * the specified dispatch source, but does not interrupt an event handler
099         * runnable that is already in progress.
100         * </p><p>
101         * The cancellation handler is submitted to the source's target queue once the
102         * the source's event handler has finished, indicating it is now safe to close
103         * the source's handle.
104         * </p>
105         *
106         * @see #setCancelHandler(Runnable) 
107         */
108        public void cancel();
109    
110        /**
111         * @see #cancel()  
112         * @return true if the dispatch source has been canceled.
113         */
114        public boolean isCanceled();
115    
116    }