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BATIK-1271: thread-safe AWTGlyphGeometryCache using ConcurrentHashMap #67

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BATIK-1271: thread-safe AWTGlyphGeometryCache using ConcurrentHashMap #67

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169 changes: 14 additions & 155 deletions batik-gvt/src/main/java/org/apache/batik/gvt/font/AWTGlyphGeometryCache.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,12 +20,12 @@ Licensed to the Apache Software Foundation (ASF) under one or more

import java.awt.Shape;
import java.awt.geom.Rectangle2D;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.concurrent.ConcurrentHashMap;

/**
* This class represents a doubly indexed hash table, which holds
* soft references to the contained glyph geometry informations.
* This class holds
* soft references to the contained glyph geometry information using a {@link java.util.concurrent.ConcurrentHashMap}.
*
* @author <a href="mailto:[email protected]">Stephane Hillion</a>
* @author <a href="mailto:[email protected]">Thierry Kormann</a>
Expand All @@ -38,161 +38,58 @@ public class AWTGlyphGeometryCache {
*/
protected static final int INITIAL_CAPACITY = 71;

/**
* The underlying array
*/
protected Entry[] table;

/**
* The number of entries
*/
protected int count;
private static <T> T getIfSet(SoftReference<T> ref) {
return ref == null ? null : ref.get();
}

/**
* The reference queue.
* The underlying map
*/
protected ReferenceQueue referenceQueue = new ReferenceQueue();
ConcurrentHashMap<Character, SoftReference<Value>> cache;

/**
* Creates a new AWTGlyphGeometryCache.
*/
public AWTGlyphGeometryCache() {
table = new Entry[INITIAL_CAPACITY];
this(INITIAL_CAPACITY);
}

/**
* Creates a new AWTGlyphGeometryCache.
* @param c The inital capacity.
*/
public AWTGlyphGeometryCache(int c) {
table = new Entry[c];
cache = new ConcurrentHashMap<>(c);
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}

/**
* Returns the size of this table.
*/
public int size() {
return count;
return cache.size();
}

/**
* Gets the value of a variable
* @return the value or null
*/
public Value get(char c) {
int hash = hashCode(c) & 0x7FFFFFFF;
int index = hash % table.length;

for (Entry e = table[index]; e != null; e = e.next) {
if ((e.hash == hash) && e.match(c)) {
return (Value)e.get();
}
}
return null;
return getIfSet(cache.get(c));
}

/**
* Sets a new value for the given variable
* @return the old value or null
*/
public Value put(char c, Value value) {
removeClearedEntries();

int hash = hashCode(c) & 0x7FFFFFFF;
int index = hash % table.length;

Entry e = table[index];
if (e != null) {
if ((e.hash == hash) && e.match(c)) {
Object old = e.get();
table[index] = new Entry(hash, c, value, e.next);
return (Value)old;
}
Entry o = e;
e = e.next;
while (e != null) {
if ((e.hash == hash) && e.match(c)) {
Object old = e.get();
e = new Entry(hash, c, value, e.next);
o.next = e;
return (Value)old;
}

o = e;
e = e.next;
}
}

// The key is not in the hash table
int len = table.length;
if (count++ >= (len - (len >> 2))) {
// more than 75% loaded: grow
rehash();
index = hash % table.length;
}

table[index] = new Entry(hash, c, value, table[index]);
return null;
return getIfSet(cache.put(c, new SoftReference<>(value)));
}

/**
* Clears the table.
*/
public void clear() {
table = new Entry[INITIAL_CAPACITY];
count = 0;
referenceQueue = new ReferenceQueue();
}

/**
* Rehash the table
*/
protected void rehash () {
Entry[] oldTable = table;

table = new Entry[oldTable.length * 2 + 1];

for (int i = oldTable.length-1; i >= 0; i--) {
for (Entry old = oldTable[i]; old != null;) {
Entry e = old;
old = old.next;

int index = e.hash % table.length;
e.next = table[index];
table[index] = e;
}
}
}

/**
* Computes a hash code corresponding to the given objects.
*/
protected int hashCode(char c) {
return c;
}

/**
* Removes the cleared entries.
*/
protected void removeClearedEntries() {
Entry e;
while ((e = (Entry)referenceQueue.poll()) != null) {
int index = e.hash % table.length;
Entry t = table[index];
if (t == e) {
table[index] = e.next;
} else {
loop: for (;t!=null;) {
Entry c = t.next;
if (c == e) {
t.next = e.next;
break loop;
}
t = c;
}
}
count--;
}
cache.clear();
}

/**
Expand Down Expand Up @@ -234,42 +131,4 @@ public Rectangle2D getOutlineBounds2D() {
return outlineBounds;
}
}

/**
* To manage collisions
*/
protected class Entry extends SoftReference {

/**
* The hash code
*/
public int hash;

/**
* The character
*/
public char c;

/**
* The next entry
*/
public Entry next;

/**
* Creates a new entry
*/
public Entry(int hash, char c, Value value, Entry next) {
super(value, referenceQueue);
this.hash = hash;
this.c = c;
this.next = next;
}

/**
* Whether this entry match the given keys.
*/
public boolean match(char o2) {
return (c == o2);
}
}
}