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Replace per-bit listener count fields with an AtomicIntegerArray #2664

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Replace per-bit listener count fields with an AtomicIntegerArray #2664

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115 changes: 29 additions & 86 deletions ...lipse.core.resources/src/org/eclipse/core/internal/events/ResourceChangeListenerList.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*******************************************************************************
* Copyright (c) 2000, 2008 IBM Corporation and others.
* Copyright (c) 2000, 2026 IBM Corporation and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
Expand All @@ -15,6 +15,7 @@

import java.util.Objects;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicIntegerArray;
import org.eclipse.core.resources.IResourceChangeListener;

/**
Expand Down Expand Up @@ -44,22 +45,18 @@ static final class ListenerEntry {

@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Listener [eventMask="); //$NON-NLS-1$
sb.append(eventMask);
sb.append(", "); //$NON-NLS-1$
sb.append(listener);
sb.append("]"); //$NON-NLS-1$
return sb.toString();
return "Listener [eventMask=" + eventMask + ", " + listener + "]"; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
}
}

private volatile int count1 = 0;
private volatile int count2 = 0;
private volatile int count4 = 0;
private volatile int count8 = 0;
private volatile int count16 = 0;
private volatile int count32 = 0;
/**
* Per-event-bit listener counts, indexed by
* {@code Integer.numberOfTrailingZeros(eventMask)}. An
* {@link AtomicIntegerArray} preserves the per-element volatile read
* semantics that {@link #hasListenerFor(int)} relies on outside the
* synchronized {@link #add}/{@link #remove}/{@link #clear} paths.
*/
private final AtomicIntegerArray bitCounts = new AtomicIntegerArray(Integer.SIZE);

/**
* The list of listeners.
Expand All @@ -79,43 +76,22 @@ public synchronized void add(IResourceChangeListener listener, int mask) {
remove(listener);
return;
}
ResourceChangeListenerList.ListenerEntry entry = new ResourceChangeListenerList.ListenerEntry(listener, mask);
ListenerEntry entry = new ListenerEntry(listener, mask);
final int oldSize = listeners.size();
// check for duplicates using identity
for (int i = 0; i < oldSize; ++i) {
ListenerEntry oldEntry = listeners.get(i);
if (oldEntry.listener == listener) {
removing(oldEntry.eventMask);
adding(mask);
adjust(oldEntry.eventMask, -1);
adjust(mask, +1);
listeners.set(i, entry);
return;
}
}
adding(mask);
adjust(mask, +1);
listeners.add(entry);
}

private void adding(int mask) {
if ((mask & 1) != 0) {
count1++;
}
if ((mask & 2) != 0) {
count2++;
}
if ((mask & 4) != 0) {
count4++;
}
if ((mask & 8) != 0) {
count8++;
}
if ((mask & 16) != 0) {
count16++;
}
if ((mask & 32) != 0) {
count32++;
}
}

/**
* Returns a copy of the registered listeners.
* @return the list of registered listeners that must not be modified
Expand All @@ -125,22 +101,11 @@ public ListenerEntry[] getListeners() {
}

public boolean hasListenerFor(int event) {
switch (event) {
case 1:
return count1 > 0;
case 2:
return count2 > 0;
case 4:
return count4 > 0;
case 8:
return count8 > 0;
case 16:
return count16 > 0;
case 32:
return count32 > 0;
default:
// event is expected to be a single bit (a power of two)
if (event <= 0 || Integer.bitCount(event) != 1) {
return false;
}
return bitCounts.get(Integer.numberOfTrailingZeros(event)) > 0;
}

/**
Expand All @@ -155,7 +120,7 @@ public synchronized void remove(IResourceChangeListener listener) {
for (int i = 0; i < oldSize; ++i) {
ListenerEntry oldEntry = listeners.get(i);
if (oldEntry.listener == listener) {
removing(oldEntry.eventMask);
adjust(oldEntry.eventMask, -1);
listeners.remove(i);
return;
}
Expand All @@ -164,44 +129,22 @@ public synchronized void remove(IResourceChangeListener listener) {

public synchronized void clear() {
listeners.clear();
count1 = 0;
count2 = 0;
count4 = 0;
count8 = 0;
count16 = 0;
count32 = 0;
for (int i = 0; i < bitCounts.length(); i++) {
bitCounts.set(i, 0);
}
}

private void removing(int mask) {
if ((mask & 1) != 0) {
count1--;
}
if ((mask & 2) != 0) {
count2--;
}
if ((mask & 4) != 0) {
count4--;
}
if ((mask & 8) != 0) {
count8--;
}
if ((mask & 16) != 0) {
count16--;
}
if ((mask & 32) != 0) {
count32--;
private void adjust(int mask, int delta) {
int remaining = mask;
while (remaining != 0) {
int bit = Integer.numberOfTrailingZeros(remaining);
bitCounts.addAndGet(bit, delta);
remaining &= remaining - 1;
}
}

@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("ResourceChangeListenerList ["); //$NON-NLS-1$
if (listeners != null) {
builder.append("listeners="); //$NON-NLS-1$
builder.append(listeners.toString());
}
builder.append("]"); //$NON-NLS-1$
return builder.toString();
return "ResourceChangeListenerList [listeners=" + listeners + "]"; //$NON-NLS-1$ //$NON-NLS-2$
}
}
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