/interpreter/tags/reactive-pattern-matching/src/edu/vub/at/signals/eval/EncapsulatingSignal.java

 1/**
 2 * AmbientTalk/2 Project
 3 * EncapsulatingReactiveComputation.java created on Jun 10, 2008 at 8:48:38 PM
 4 * (c) Programming Technology Lab, 2006 - 2007
 5 * Authors: Tom Van Cutsem & Stijn Mostinckx
 6 * 
 7 * Permission is hereby granted, free of charge, to any person
 8 * obtaining a copy of this software and associated documentation
 9 * files (the "Software"), to deal in the Software without
10 * restriction, including without limitation the rights to use,
11 * copy, modify, merge, publish, distribute, sublicense, and/or
12 * sell copies of the Software, and to permit persons to whom the
13 * Software is furnished to do so, subject to the following
14 * conditions:
15 *
16 * The above copyright notice and this permission notice shall be
17 * included in all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
26 * OTHER DEALINGS IN THE SOFTWARE.
27 */
28package edu.vub.at.signals.eval;
29
30import java.util.HashSet;
31import java.util.Iterator;
32
33import edu.vub.at.signals.SignalListener;
34
35/**
36 * When creating a dependency network inside the body of a method, this network may depend implicitly
37 * on other reactive computations, for instance if the method was called with another behavior as the
38 * receiver or as an argument of that method.  EncapsulatingSignal instances are managed in a dynamic
39 * variable by the interpreter to keep track of these implicit dependencies.
40 * 
41 * Hence, when the method is triggered due to changes in an argument or the receiver,  the dependency
42 * network that was constructed in the previous invocation is automatically dismantled.
43 * 
44 * @author smostinc
45 */
46public class EncapsulatingSignal {
47
48	private HashSet nestedSignalListeners_ = new HashSet();
49	private int dependencyHeight_;
50	
51	public EncapsulatingSignal(int dependencyHeight) {
52		dependencyHeight_ = dependencyHeight;
53	}
54	
55	/**
56	 * When dependent computations are created within the control flow of this encapsulating
57	 * signal,  their minimal dependency height should be greater than the dependency height
58	 * of the encapsulating signal.
59	 */
60	public int dependencyHeight() {
61		return dependencyHeight_;
62	}
63	
64	/**
65	 * When the encapsulating reactive computation needs to be performed anew, all dependent
66	 * computations that were constructed within its dynamic extent need need to be unhooked.
67	 */
68	public synchronized void unhookAllDependencies() {
69		for (Iterator nestedSignalIt = nestedSignalListeners_.iterator(); nestedSignalIt.hasNext();) {
70			SignalListener currentSignalListener = (SignalListener) nestedSignalIt.next();
71			
72			currentSignalListener.unhook();
73			nestedSignalIt.remove();
74		}
75	}
76	
77	
78	public synchronized void registerDependency(SignalListener theNestedListener) {
79		nestedSignalListeners_.add(theNestedListener);
80	}
81}