kitaev@213: /*
kitaev@213:  * Copyright (c) 2011 TMate Software Ltd
kitaev@213:  *  
kitaev@213:  * This program is free software; you can redistribute it and/or modify
kitaev@213:  * it under the terms of the GNU General Public License as published by
kitaev@213:  * the Free Software Foundation; version 2 of the License.
kitaev@213:  *
kitaev@213:  * This program is distributed in the hope that it will be useful,
kitaev@213:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
kitaev@213:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
kitaev@213:  * GNU General Public License for more details.
kitaev@213:  *
kitaev@213:  * For information on how to redistribute this software under
kitaev@213:  * the terms of a license other than GNU General Public License
kitaev@213:  * contact TMate Software at support@hg4j.com
kitaev@213:  */
kitaev@213: package org.tmatesoft.hg.util;
kitaev@213: 
kitaev@213: /**
kitaev@213:  * Mix-in for objects that support cancellation. 
kitaev@213:  * 
kitaev@213:  * @author Artem Tikhomirov
kitaev@213:  * @author TMate Software Ltd.
kitaev@213:  */
kitaev@213: public interface CancelSupport {
kitaev@213: 
kitaev@213: 	/**
kitaev@213: 	 * This method is invoked to check if target had been brought to canceled state. Shall silently return if target is
kitaev@213: 	 * in regular state.
kitaev@213: 	 * @throws CancelledException when target internal state has been changed to canceled.
kitaev@213: 	 */
kitaev@213: 	void checkCancelled() throws CancelledException;
kitaev@213: 
kitaev@213: 
kitaev@213: 	// Yeah, this factory class looks silly now, but perhaps in the future I'll need wrappers for other cancellation sources?
kitaev@213: 	// just don't want to have general Utils class with methods like get() below
kitaev@213: 	static class Factory {
kitaev@213: 
kitaev@213: 		/**
kitaev@213: 		 * Obtain non-null cancel support object.
kitaev@213: 		 * 
kitaev@213: 		 * @param target any object (or <code>null</code>) that might have cancel support
kitaev@213: 		 * @return target if it's capable checking cancellation status or no-op implementation that never cancels.
kitaev@213: 				 */
kitaev@213: 		public static CancelSupport get(Object target) {
kitaev@213: 			if (target instanceof  CancelSupport) {
kitaev@213: 				return (CancelSupport) target;
kitaev@213: 			}
kitaev@213: 			if (target instanceof Adaptable) {
kitaev@213: 				CancelSupport cs = ((Adaptable) target).getAdapter(CancelSupport.class);
kitaev@213: 				if (cs != null) {
kitaev@213: 					return cs;
kitaev@213: 				}
kitaev@213: 			}
kitaev@213: 			return new CancelSupport() {
kitaev@213: 				public void checkCancelled() {
kitaev@213: 				}
kitaev@213: 			};
kitaev@213: 		}
kitaev@213: 	}
kitaev@213: }