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- Replaced implementation of the Generator class. The previous version was not yielding correctly.
git-svn-id: svn://192.168.0.80/JavaXT/javaxt-core@1077 2c7b0aa6-e0b2-3c4e-bb4a-8b65b6c465ff
1 parent 506ff60 commit fabbece

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+114
-103
lines changed

1 file changed

+114
-103
lines changed

‎src/javaxt/utils/Generator.java‎

Lines changed: 114 additions & 103 deletions
Original file line numberDiff line numberDiff line change
@@ -29,113 +29,124 @@ public void run() {
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}
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};
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</pre>
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*
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* Clients can iterate through the generated results using standard iterators
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* or an enhanced for loop like this:
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<pre>
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for (String row : generator){
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System.out.println(row);
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}
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</pre>
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*
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* @author Adrian Kuhn &lt;akuhn(at)iam.unibe.ch&gt;
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* @author Michael Herrmann
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* https://github.com/mherrmann/java-generator-functions
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*
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******************************************************************************/
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public abstract class Generator<T> implements Iterable<T> {
3847

39-
public abstract void run();
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public Iterator<T> iterator() {
42-
return new Iter();
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}
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private static final Object DONE = new Object();
46-
private static final Object EMPTY = new Object();
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private Object drop = EMPTY;
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private Thread th = null;
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private synchronized Object take() {
51-
while (drop == EMPTY) {
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try {
53-
wait();
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} catch (InterruptedException ex) {
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Thread.currentThread().interrupt();
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}
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}
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Object temp = drop;
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if (drop != DONE)
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drop = EMPTY;
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notifyAll();
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return temp;
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}
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private synchronized void put(Object value) {
66-
if (drop == DONE)
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throw new IllegalStateException();
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if (drop != EMPTY)
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throw new IllegalStateException();
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drop = value;
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notifyAll();
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while (drop != EMPTY) {
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try {
74-
wait();
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} catch (InterruptedException ex) {
76-
Thread.currentThread().interrupt();
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}
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}
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}
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81-
protected void yield(T value) {
82-
put(value);
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}
84-
85-
public synchronized void done() {
86-
if (drop == DONE)
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throw new IllegalStateException();
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if (drop != EMPTY)
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throw new IllegalStateException();
90-
drop = DONE;
91-
notifyAll();
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}
93-
94-
private class Iter implements Iterator<T>, Runnable {
95-
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private Object next = EMPTY;
97-
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public Iter() {
99-
if (th != null)
100-
throw new IllegalStateException("Can not run coroutine twice");
101-
th = new Thread(this);
102-
th.setDaemon(true);
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th.start();
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}
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public void run() {
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Generator.this.run();
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done();
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}
110-
111-
public boolean hasNext() {
112-
if (next == EMPTY)
113-
next = take();
114-
return next != DONE;
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}
116-
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@SuppressWarnings("unchecked")
118-
public T next() {
119-
if (next == EMPTY)
120-
next = take();
121-
if (next == DONE)
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throw new NoSuchElementException();
123-
Object temp = next;
124-
next = EMPTY;
125-
return (T) temp;
126-
}
127-
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public void remove() {
129-
throw new UnsupportedOperationException();
130-
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}
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@SuppressWarnings("deprecation")
134-
@Override
135-
protected void finalize() throws Throwable {
136-
th.stop(); // let's commit suicide
137-
}
138-
139-
}
140-
48+
private class Condition {
49+
private boolean isSet;
50+
public synchronized void set() {
51+
isSet = true;
52+
notify();
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}
54+
public synchronized void await() throws InterruptedException {
55+
try {
56+
if (isSet)
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return;
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wait();
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} finally {
60+
isSet = false;
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}
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}
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}
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static ThreadGroup THREAD_GROUP;
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Thread producer;
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private boolean hasFinished;
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private final Condition itemAvailableOrHasFinished = new Condition();
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private final Condition itemRequested = new Condition();
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private T nextItem;
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private boolean nextItemAvailable;
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private RuntimeException exceptionRaisedByProducer;
74+
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@Override
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public Iterator<T> iterator() {
77+
return new Iterator<T>() {
78+
@Override
79+
public boolean hasNext() {
80+
return waitForNext();
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}
82+
@Override
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public T next() {
84+
if (!waitForNext())
85+
throw new NoSuchElementException();
86+
nextItemAvailable = false;
87+
return nextItem;
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}
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@Override
90+
public void remove() {
91+
throw new UnsupportedOperationException();
92+
}
93+
private boolean waitForNext() {
94+
if (nextItemAvailable)
95+
return true;
96+
if (hasFinished)
97+
return false;
98+
if (producer == null)
99+
startProducer();
100+
itemRequested.set();
101+
try {
102+
itemAvailableOrHasFinished.await();
103+
} catch (InterruptedException e) {
104+
hasFinished = true;
105+
}
106+
if (exceptionRaisedByProducer != null)
107+
throw exceptionRaisedByProducer;
108+
return !hasFinished;
109+
}
110+
};
111+
}
112+
113+
protected abstract void run() throws InterruptedException;
114+
115+
protected void yield(T element) throws InterruptedException {
116+
nextItem = element;
117+
nextItemAvailable = true;
118+
itemAvailableOrHasFinished.set();
119+
itemRequested.await();
120+
}
121+
122+
private void startProducer() {
123+
assert producer == null;
124+
if (THREAD_GROUP == null)
125+
THREAD_GROUP = new ThreadGroup("generatorfunctions");
126+
producer = new Thread(THREAD_GROUP, new Runnable() {
127+
@Override
128+
public void run() {
129+
try {
130+
itemRequested.await();
131+
Generator.this.run();
132+
} catch (InterruptedException e) {
133+
// No need to do anything here; Remaining steps in run()
134+
// will cleanly shut down the thread.
135+
} catch (RuntimeException e) {
136+
exceptionRaisedByProducer = e;
137+
}
138+
hasFinished = true;
139+
itemAvailableOrHasFinished.set();
140+
}
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});
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producer.setDaemon(true);
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producer.start();
144+
}
145+
146+
@Override
147+
protected void finalize() throws Throwable {
148+
producer.interrupt();
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producer.join();
150+
super.finalize();
151+
}
141152
}

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