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classlib: refactor LinkedHashMap
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I found regression somewhere in LinkedHashMap, when certain operations cause cycle in entry list. Since updated logic was totally unclear to me, I rewrote it from scratch. Also, reverted mechanism to remove entries NOT by keys and used it where necessary to improve performance.
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@konsoletyper
konsoletyper committed Nov 23, 2023
1 parent 86efdb0 commit a1355bb
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Showing 4 changed files with 165 additions and 134 deletions.
27 changes: 23 additions & 4 deletions classlib/src/main/java/org/teavm/classlib/java/util/THashMap.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,11 @@
import java.util.function.BiFunction;
import java.util.function.Consumer;
import org.teavm.classlib.java.io.TSerializable;
import org.teavm.classlib.java.lang.*;
import org.teavm.classlib.java.lang.TCloneNotSupportedException;
import org.teavm.classlib.java.lang.TCloneable;
import org.teavm.classlib.java.lang.TIllegalArgumentException;
import org.teavm.classlib.java.lang.TIllegalStateException;
import org.teavm.classlib.java.lang.TObject;
import org.teavm.interop.Rename;

public class THashMap<K, V> extends TAbstractMap<K, V> implements TCloneable, TSerializable {
Expand Down Expand Up @@ -192,10 +196,10 @@ public void clear() {
@Override
public boolean remove(Object object) {
if (object instanceof TMap.Entry) {
TMap.Entry<?, ?> oEntry = (TMap.Entry<?, ?>) object;
TMap.Entry<K, V> entry = associatedMap.entryByKey(oEntry.getKey());
var oEntry = (TMap.Entry<?, ?>) object;
var entry = associatedMap.entryByKey(oEntry.getKey());
if (entry != null && TObjects.equals(entry.getValue(), oEntry.getValue())) {
associatedMap.removeByKey(entry.getKey());
associatedMap.removeEntry(entry);
return true;
}
}
Expand Down Expand Up @@ -531,6 +535,21 @@ public V remove(Object key) {
return null;
}

final void removeEntry(HashEntry<K, V> entry) {
int index = entry.origKeyHash & (elementData.length - 1);
var m = elementData[index];
if (m == entry) {
elementData[index] = entry.next;
} else {
while (m.next != entry) {
m = m.next;
}
m.next = entry.next;
}
modCount++;
elementCount--;
}

final HashEntry<K, V> removeByKey(Object key) {
int index = 0;
HashEntry<K, V> entry;
Expand Down
227 changes: 101 additions & 126 deletions classlib/src/main/java/org/teavm/classlib/java/util/TLinkedHashMap.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
*/
package org.teavm.classlib.java.util;

import java.util.Objects;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;

Expand Down Expand Up @@ -63,8 +64,8 @@ void putAllImpl(TMap<? extends K, ? extends V> map) {
rehash(capacity);
}
for (var it = map.entrySet().iterator(); it.hasNext();) {
TMap.Entry<? extends K, ? extends V> entry = it.next();
putImpl(entry.getKey(), entry.getValue(), false);
var entry = it.next();
putImpl(entry.getKey(), entry.getValue(), false, accessOrder);
}
}

Expand Down Expand Up @@ -127,32 +128,21 @@ HashEntry<K, V>[] newElementArray(int s) {

@Override
public V getOrDefault(Object key, V defaultValue) {
LinkedHashMapEntry<K, V> m;
LinkedHashMapEntry<K, V> entry;
if (key == null) {
m = (LinkedHashMapEntry<K, V>) findNullKeyEntry();
entry = (LinkedHashMapEntry<K, V>) findNullKeyEntry();
} else {
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % elementData.length;
m = (LinkedHashMapEntry<K, V>) findNonNullKeyEntry(key, index, hash);
entry = (LinkedHashMapEntry<K, V>) findNonNullKeyEntry(key, index, hash);
}
if (m == null) {
if (entry == null) {
return defaultValue;
}
if (accessOrder && tail != m) {
LinkedHashMapEntry<K, V> p = m.chainBackward;
LinkedHashMapEntry<K, V> n = m.chainForward;
n.chainBackward = p;
if (p != null) {
p.chainForward = n;
} else {
head = n;
}
m.chainForward = null;
m.chainBackward = tail;
tail.chainForward = m;
tail = m;
if (accessOrder) {
linkEntry(entry, false);
}
return m.value;
return entry.value;
}

@Override
Expand All @@ -161,128 +151,103 @@ public V get(Object key) {
}

private HashEntry<K, V> createHashedEntry(K key, int index, int hash, boolean first) {
LinkedHashMapEntry<K, V> m = new LinkedHashMapEntry<>(key, hash);
m.next = elementData[index];
elementData[index] = m;
linkEntry(m, first);
return m;
var entry = new LinkedHashMapEntry<K, V>(key, hash);
entry.next = elementData[index];
elementData[index] = entry;
if (first) {
if (head != null) {
head.chainBackward = entry;
} else {
tail = entry;
}
entry.chainForward = head;
head = entry;
} else {
if (tail != null) {
tail.chainForward = entry;
} else {
head = entry;
}
entry.chainBackward = tail;
tail = entry;
}
return entry;
}

@Override
public V put(K key, V value) {
return putImpl(key, value, false);
var oldSize = size();
var existing = putImpl(key, value, false, accessOrder);
if (size() != oldSize) {
if (removeEldestEntry(head)) {
removeLinkedEntry(head);
}
}
return existing;
}

V putImpl(K key, V value, boolean first) {
LinkedHashMapEntry<K, V> m;
V putImpl(K key, V value, boolean first, boolean forceMotion) {
LinkedHashMapEntry<K, V> entry;
if (elementCount == 0) {
head = null;
tail = null;
}
if (key == null) {
m = (LinkedHashMapEntry<K, V>) findNullKeyEntry();
if (m == null) {
modCount++;
// Check if we need to remove the oldest entry. The check
// includes accessOrder since an accessOrder LinkedHashMap does
// not record the oldest member in 'head'.
if (++elementCount > threshold) {
rehash();
}
m = (LinkedHashMapEntry<K, V>) createHashedEntry(null, 0, 0, first);
} else {
linkEntry(m, first);
}
} else {
int hash = key.hashCode();
int index = (hash & Integer.MAX_VALUE) % elementData.length;
m = (LinkedHashMapEntry<K, V>) findNonNullKeyEntry(key, index, hash);
if (m == null) {
modCount++;
if (++elementCount > threshold) {
rehash();
index = (hash & Integer.MAX_VALUE) % elementData.length;
}
m = (LinkedHashMapEntry<K, V>) createHashedEntry(key, index, hash, first);
} else {
linkEntry(m, first);
int hash = Objects.hashCode(key);
int index = (hash & Integer.MAX_VALUE) % elementData.length;
entry = (LinkedHashMapEntry<K, V>) (key != null ? findNonNullKeyEntry(key, index, hash) : findNullKeyEntry());
if (entry == null) {
modCount++;
if (++elementCount > threshold) {
rehash();
index = (hash & Integer.MAX_VALUE) % elementData.length;
}
entry = (LinkedHashMapEntry<K, V>) createHashedEntry(key, index, hash, first);
} else if (forceMotion) {
linkEntry(entry, first);
}

V result = m.value;
m.value = value;

if (removeEldestEntry(head)) {
remove(head.key);
}

return result;
var existing = entry.value;
entry.value = value;
return existing;
}

void linkEntry(LinkedHashMapEntry<K, V> m, boolean first) {
if (head == null) {
// Check if the map is empty
head = m;
tail = m;
return;
}

// we need to link the new entry into either the head or tail
// of the chain depending on if the LinkedHashMap is accessOrder or not
LinkedHashMapEntry<K, V> p = m.chainBackward;
LinkedHashMapEntry<K, V> n = m.chainForward;
if (p == null) {
private void linkEntry(LinkedHashMapEntry<K, V> entry, boolean first) {
if (first) {
var p = entry.chainBackward;
if (p == null) {
return;
}
var n = entry.chainForward;
if (n != null) {
// Existing entry must be the head but not the tail
if (!first && accessOrder) {
head = n;
n.chainBackward = null;
m.chainBackward = tail;
m.chainForward = null;
tail.chainForward = m;
tail = m;
}
n.chainBackward = p;
} else {
// This is a new entry
m.chainBackward = first ? null : tail;
m.chainForward = first ? head : null;
if (first) {
head.chainBackward = m;
head = m;
} else {
tail.chainForward = m;
tail = m;
}
tail = p;
}
p.chainForward = n;
if (head != null) {
head.chainBackward = entry;
}
entry.chainForward = head;
entry.chainBackward = null;
head = entry;
} else {
var n = entry.chainForward;
if (n == null) {
// Existing entry must be the tail but not the head
if (first && accessOrder) {
tail = p;
p.chainForward = null;
m.chainBackward = null;
m.chainForward = head;
head.chainBackward = m;
head = m;
}
return;
}
var p = entry.chainBackward;
if (p != null) {
p.chainForward = n;
} else {
if (elementCount > 1 && accessOrder) {
// Existing entry is neither the head nor tail
p.chainForward = n;
n.chainBackward = p;
if (first) {
m.chainForward = head;
m.chainBackward = null;
head.chainBackward = m;
head = m;
} else {
m.chainForward = null;
m.chainBackward = tail;
tail.chainForward = m;
tail = m;
}
}
head = n;
}
n.chainBackward = p;
if (tail != null) {
tail.chainForward = entry;
}
entry.chainBackward = tail;
entry.chainForward = null;
tail = entry;
}
}

Expand Down Expand Up @@ -324,12 +289,23 @@ public TSequencedSet<Entry<K, V>> sequencedEntrySet() {

@Override
public V remove(Object key) {
LinkedHashMapEntry<K, V> m = (LinkedHashMapEntry<K, V>) removeByKey(key);
var m = (LinkedHashMapEntry<K, V>) removeByKey(key);
if (m == null) {
return null;
}
LinkedHashMapEntry<K, V> p = m.chainBackward;
LinkedHashMapEntry<K, V> n = m.chainForward;
unlinkEntry(m);

return m.value;
}

void removeLinkedEntry(LinkedHashMapEntry<K, V> entry) {
removeEntry(entry);
unlinkEntry(entry);
}

private void unlinkEntry(LinkedHashMapEntry<K, V> entry) {
var p = entry.chainBackward;
var n = entry.chainForward;
if (p != null) {
p.chainForward = n;
if (n != null) {
Expand All @@ -345,7 +321,6 @@ public V remove(Object key) {
tail = null;
}
}
return m.value;
}

@Override
Expand Down Expand Up @@ -391,12 +366,12 @@ public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {

@Override
public V putFirst(K k, V v) {
return putImpl(k, v, true);
return putImpl(k, v, true, true);
}

@Override
public V putLast(K k, V v) {
return putImpl(k, v, false);
return putImpl(k, v, false, true);
}

@Override
Expand Down
2 changes: 1 addition & 1 deletion classlib/src/main/java/org/teavm/classlib/java/util/TLinkedHashMapIterator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,7 @@ public void remove() {
throw new IllegalStateException();
}
checkConcurrentMod();
base.remove(currentEntry.key);
base.removeLinkedEntry(currentEntry);
currentEntry = null;
expectedModCount++;
}
Expand Down
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