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From kwsut...@apache.org
Subject svn commit: r672003 - in /openjpa/trunk: openjpa-kernel/src/main/java/org/apache/openjpa/util/CacheMap.java openjpa-lib/src/main/java/org/apache/openjpa/lib/util/concurrent/ConcurrentHashMap.java
Date Thu, 26 Jun 2008 19:31:21 GMT
Author: kwsutter
Date: Thu Jun 26 12:31:20 2008
New Revision: 672003

URL: http://svn.apache.org/viewvc?rev=672003&view=rev
Log:
OPENJPA-637.  Reverting ConcurrentHashMap implementation per the patch provided by Jeremy
Bauer.  A more complete, configurable implementation is being tracked via the related sub-task
OPENJPA-643.

Added:
    openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/concurrent/ConcurrentHashMap.java
  (with props)
Modified:
    openjpa/trunk/openjpa-kernel/src/main/java/org/apache/openjpa/util/CacheMap.java

Modified: openjpa/trunk/openjpa-kernel/src/main/java/org/apache/openjpa/util/CacheMap.java
URL: http://svn.apache.org/viewvc/openjpa/trunk/openjpa-kernel/src/main/java/org/apache/openjpa/util/CacheMap.java?rev=672003&r1=672002&r2=672003&view=diff
==============================================================================
--- openjpa/trunk/openjpa-kernel/src/main/java/org/apache/openjpa/util/CacheMap.java (original)
+++ openjpa/trunk/openjpa-kernel/src/main/java/org/apache/openjpa/util/CacheMap.java Thu Jun
26 12:31:20 2008
@@ -22,7 +22,6 @@
 import java.util.AbstractSet;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;
@@ -31,12 +30,10 @@
 import org.apache.commons.collections.iterators.FilterIterator;
 import org.apache.commons.collections.iterators.IteratorChain;
 import org.apache.openjpa.lib.util.LRUMap;
-import org.apache.openjpa.lib.util.ReferenceHashMap;
 import org.apache.openjpa.lib.util.ReferenceMap;
 import org.apache.openjpa.lib.util.SizedMap;
+import org.apache.openjpa.lib.util.concurrent.ConcurrentHashMap;
 import org.apache.openjpa.lib.util.concurrent.ConcurrentReferenceHashMap;
-import org.apache.openjpa.lib.util.concurrent.NullSafeConcurrentHashMap;
-import org.apache.openjpa.lib.util.concurrent.SizedConcurrentHashMap;
 
 import java.util.concurrent.locks.ReentrantLock;
 
@@ -114,10 +111,10 @@
                 softMapValueExpired(key);
             }
         };
-        pinnedMap = new NullSafeConcurrentHashMap();
+        pinnedMap = new ConcurrentHashMap();
 
         if (!lru) {
-            cacheMap = new SizedConcurrentHashMap(size, load, concurrencyLevel){
+            cacheMap = new ConcurrentHashMap(size, load) {
                 public void overflowRemoved(Object key, Object value) {
                     cacheMapOverflowRemoved(key, value);
                 }

Added: openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/concurrent/ConcurrentHashMap.java
URL: http://svn.apache.org/viewvc/openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/concurrent/ConcurrentHashMap.java?rev=672003&view=auto
==============================================================================
--- openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/concurrent/ConcurrentHashMap.java
(added)
+++ openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/concurrent/ConcurrentHashMap.java
Thu Jun 26 12:31:20 2008
@@ -0,0 +1,941 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.    
+ */
+package org.apache.openjpa.lib.util.concurrent;
+
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.util.AbstractCollection;
+import java.util.AbstractMap;
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Random;
+import java.util.Set;
+
+import org.apache.openjpa.lib.util.SizedMap;
+
+/**
+ * This class implements a HashMap which has limited synchronization.
+ * In particular mutators are generally synchronized while accessors
+ * are generally not. Additionally the Iterators returned by this
+ * class are not "fail-fast", but instead try to continue to iterate
+ * over the data structure after changes have been made.
+ * The synchronization semantics are built right in to the
+ * implementation rather than using a delegating wrapper like the
+ * other collection classes do because it wasn't clear to me that the
+ * how the two should be seperated or that it would be useful to do
+ * so. This can probably be a topic for further debate in the future.
+ * This class is based heavily on the HashMap class in the Java
+ * collections package.
+ */
+public class ConcurrentHashMap extends AbstractMap
+    implements ConcurrentMap, SizedMap, Cloneable, Serializable {
+
+    /**
+     * The default initial capacity - MUST be a power of two.
+     */
+    private static final int DEFAULT_INITIAL_CAPACITY = 16;
+
+    /**
+     * The maximum capacity, used if a higher value is implicitly specified
+     * by either of the constructors with arguments.
+     * MUST be a power of two <= 1<<30.
+     */
+    private static final int MAXIMUM_CAPACITY = 1 << 30;
+
+    /**
+     * The load fast used when none specified in constructor.
+     */
+    private static final float DEFAULT_LOAD_FACTOR = 0.75f;
+
+    /**
+     * Cache of random numbers used in "random" methods, since generating them
+     * is expensive. We hope each map changes enough between cycling through
+     * this list that the overall effect is random enough.
+     */
+    static final double[] RANDOMS = new double[1000];
+
+    static {
+        Random random = new Random();
+        for (int i = 0; i < RANDOMS.length; i++)
+            RANDOMS[i] = random.nextDouble();
+    }
+
+    /**
+     * The table, resized as necessary. Length MUST Always be a power of two.
+     */
+    private transient Entry[] table;
+
+    /**
+     * The number of key-value mappings contained in this identity hash map.
+     */
+    private transient int size;
+
+    /**
+     * The next size value at which to resize(capacity * load factor).
+     *
+     * @serial
+     */
+    private int threshold;
+
+    /**
+     * The load factor for the hash table.
+     *
+     * @serial
+     */
+    private final float loadFactor;
+
+    /**
+     * Spread "random" removes and iteration.
+     */
+    private int randomEntry = 0;
+
+    /**
+     * Maximum entries.
+     */
+    private int maxSize = Integer.MAX_VALUE;
+
+    /**
+     * Constructs an empty <tt>ConcurrentHashMap</tt> with the specified initial
+     * capacity and load factor.
+     *
+     * @param initialCapacity The initial capacity.
+     * @param loadFactor The load factor.
+     * @throws IllegalArgumentException if the initial capacity is negative
+     * or the load factor is nonpositive.
+     */
+    public ConcurrentHashMap(int initialCapacity, float loadFactor) {
+        if (initialCapacity < 0) {
+            throw new IllegalArgumentException("Illegal initial capacity: " +
+                initialCapacity);
+        }
+        if (initialCapacity > MAXIMUM_CAPACITY)
+            initialCapacity = MAXIMUM_CAPACITY;
+        if (loadFactor <= 0 || loadFactor > 1) {
+            throw new IllegalArgumentException("Illegal load factor: " +
+                loadFactor);
+        }
+
+        // Find a power of 2 >= initialCapacity
+        int capacity = 1;
+        while (capacity < initialCapacity) capacity <<= 1;
+
+        this.loadFactor = loadFactor;
+        threshold = (int) (capacity * loadFactor);
+        table = new Entry[capacity];
+    }
+
+    /**
+     * Constructs an empty <tt>ConcurrentHashMap</tt> with the specified initial
+     * capacity and the default load factor(0.75).
+     *
+     * @param initialCapacity the initial capacity.
+     * @throws IllegalArgumentException if the initial capacity is negative.
+     */
+    public ConcurrentHashMap(int initialCapacity) {
+        this(initialCapacity, DEFAULT_LOAD_FACTOR);
+    }
+
+    /**
+     * Constructs an empty <tt>ConcurrentHashMap</tt> with the default initial
+     * capacity(16) and the default load factor(0.75).
+     */
+    public ConcurrentHashMap() {
+        this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
+    }
+
+    /**
+     * Constructs a new <tt>ConcurrentHashMap</tt> with the same mappings as
the
+     * specified <tt>Map</tt>. The <tt>ConcurrentHashMap</tt> is
created with
+     * default load factor(0.75) and an initial capacity sufficient to
+     * hold the mappings in the specified <tt>Map</tt>.
+     *
+     * @param m the map whose mappings are to be placed in this map.
+     * @throws NullPointerException if the specified map is null.
+     */
+    public ConcurrentHashMap(Map m) {
+        this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
+            DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
+        putAll(m);
+    }
+
+    // internal utilities
+
+    /**
+     * Value representing null keys inside tables.
+     */
+    private static final Object NULL_KEY = new Object();
+
+    /**
+     * Returns internal representation for key. Use NULL_KEY if key is null.
+     */
+    private static Object maskNull(Object key) {
+        return (key == null ? NULL_KEY : key);
+    }
+
+    /**
+     * Returns key represented by specified internal representation.
+     */
+    private static Object unmaskNull(Object key) {
+        return (key == NULL_KEY ? null : key);
+    }
+
+    /**
+     * Returns a hash code for non-null Object x.
+     */
+    private static int hash(Object x) {
+        int h = x.hashCode();
+        return h - (h << 7); // i.e., -127 * h
+    }
+
+    /**
+     * Check for equality of non-null reference x and possibly-null y.
+     */
+    private static boolean eq(Object x, Object y) {
+        return x == y || x.equals(y);
+    }
+
+    /**
+     * Returns the current capacity of backing table in this map.
+     *
+     * @return the current capacity of backing table in this map.
+     */
+    public final int capacity() {
+        return table.length;
+    }
+
+    /**
+     * Returns the load factor for this map.
+     *
+     * @return the load factor for this map.
+     */
+    public final float loadFactor() {
+        return loadFactor;
+    }
+
+    public int getMaxSize() {
+        return maxSize;
+    }
+
+    public void setMaxSize(int maxSize) {
+        this.maxSize = (maxSize < 0) ? Integer.MAX_VALUE : maxSize;
+        if (this.maxSize != Integer.MAX_VALUE)
+            removeOverflow(this.maxSize);
+    }
+
+    public boolean isFull() {
+        return maxSize != Integer.MAX_VALUE && size() >= maxSize;
+    }
+
+    public void overflowRemoved(Object key, Object value) {
+    }
+
+    /**
+     * Returns the number of key-value mappings in this map.
+     *
+     * @return the number of key-value mappings in this map.
+     */
+    public final int size() {
+        return size;
+    }
+
+    /**
+     * Returns <tt>true</tt> if this map contains no key-value mappings.
+     *
+     * @return <tt>true</tt> if this map contains no key-value mappings.
+     */
+    public final boolean isEmpty() {
+        return size == 0;
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped in this identity
+     * hash map, or <tt>null</tt> if the map contains no mapping for this key.
+     * A return value of <tt>null</tt> does not <i>necessarily</i>
indicate
+     * that the map contains no mapping for the key; it is also possible that
+     * the map explicitly maps the key to <tt>null</tt>. The
+     * <tt>containsKey</tt> method may be used to distinguish these two cases.
+     *
+     * @param key the key whose associated value is to be returned.
+     * @return the value to which this map maps the specified key, or
+     * <tt>null</tt> if the map contains no mapping for this key.
+     * @see #put(Object, Object)
+     */
+    public Object get(Object key) {
+        Entry e = getEntry(key);
+        return e == null ? null : e.value;
+    }
+
+    /**
+     * Returns <tt>true</tt> if this map contains a mapping for the
+     * specified key.
+     *
+     * @param key The key whose presence in this map is to be tested
+     * @return <tt>true</tt> if this map contains a mapping for the specified
+     * key.
+     */
+    public final boolean containsKey(Object key) {
+        return getEntry(key) != null;
+    }
+
+    /**
+     * Returns the entry associated with the specified key in the
+     * ConcurrentHashMap. Returns null if the ConcurrentHashMap contains no
+     * mapping for this key.
+     */
+    protected Entry getEntry(Object key) {
+        Object k = maskNull(key);
+        int hash = hash(k);
+        Entry[] tab = table;
+        for (Entry e = tab[hash & (tab.length - 1)]; e != null; e = e.next) {
+            if (e.hash == hash && eq(k, e.key)) return e;
+        }
+        return null;
+    }
+
+    /**
+     * Associates the specified value with the specified key in this map.
+     * If the map previously contained a mapping for this key, the old
+     * value is replaced.
+     *
+     * @param key key with which the specified value is to be associated.
+     * @param value value to be associated with the specified key.
+     * @return previous value associated with specified key, or <tt>null</tt>
+     * if there was no mapping for key. A <tt>null</tt> return can
+     * also indicate that the ConcurrentHashMap previously associated
+     * <tt>null</tt> with the specified key.
+     */
+    public Object put(Object key, Object value) {
+        Object k = maskNull(key);
+        int hash = hash(k);
+        synchronized (this) {
+            int i = hash & (table.length - 1);
+
+            for (Entry e = table[i]; e != null; e = e.next) {
+                if (e.hash == hash && eq(k, e.key)) {
+                    Object oldValue = e.value;
+                    e.value = value;
+                    return oldValue;
+                }
+            }
+
+            if (maxSize != Integer.MAX_VALUE)
+                removeOverflow(maxSize - 1);
+            table[i] = createEntry(hash, k, value, table[i]);
+            if (size++ >= threshold) resize(2 * table.length);
+        }
+        return null;
+    }
+
+    /**
+     * Remove any entries equal to or over the max size.
+     */
+    private void removeOverflow(int maxSize) {
+        while (size > maxSize) {
+            Map.Entry entry = removeRandom();
+            if (entry == null)
+                break;
+            overflowRemoved(entry.getKey(), entry.getValue());
+        }
+    }
+
+    public Object putIfAbsent(Object key, Object value) {
+        Object k = maskNull(key);
+        int hash = hash(k);
+        synchronized (this) {
+            int i = hash & (table.length - 1);
+
+            for (Entry e = table[i]; e != null; e = e.next) {
+                if (e.hash == hash && eq(k, e.key)) {
+                    return e.value;
+                }
+            }
+
+            if (maxSize != Integer.MAX_VALUE)
+                removeOverflow(maxSize - 1);
+            table[i] = createEntry(hash, k, value, table[i]);
+            if (size++ >= threshold) resize(2 * table.length);
+        }
+        return null;
+    }
+
+    /**
+     * Rehashes the contents of this map into a new <tt>ConcurrentHashMap</tt>
+     * instance with a larger capacity. This method is called automatically when
+     * the number of keys in this map exceeds its capacity and load factor.
+     *
+     * @param newCapacity the new capacity, MUST be a power of two.
+     */
+    private void resize(int newCapacity) {
+        // assert(newCapacity & -newCapacity) == newCapacity; // power of 2
+        Entry[] oldTable = table;
+        int oldCapacity = oldTable.length;
+
+        // check if needed
+        if (size < threshold || oldCapacity > newCapacity) return;
+
+        Entry[] newTable = new Entry[newCapacity];
+        int mask = newCapacity - 1;
+        for (int i = oldCapacity; i-- > 0;) {
+            for (Entry e = oldTable[i]; e != null; e = e.next) {
+                Entry clone = (Entry) e.clone();
+                int j = clone.hash & mask;
+                clone.next = newTable[j];
+                newTable[j] = clone;
+            }
+        }
+        table = newTable;
+        threshold = (int) (newCapacity * loadFactor);
+    }
+
+    /**
+     * Copies all of the mappings from the specified map to this map
+     * These mappings will replace any mappings that
+     * this map had for any of the keys currently in the specified map.
+     *
+     * @param t mappings to be stored in this map.
+     * @throws NullPointerException if the specified map is null.
+     */
+    public final synchronized void putAll(Map t) {
+        // Expand enough to hold t's elements without resizing.
+        int n = t.size();
+        if (n == 0) return;
+        if (n >= threshold) {
+            n = (int) (n / loadFactor + 1);
+            if (n > MAXIMUM_CAPACITY) n = MAXIMUM_CAPACITY;
+            int capacity = table.length;
+            while (capacity < n) capacity <<= 1;
+            resize(capacity);
+        }
+
+        for (Iterator i = t.entrySet().iterator(); i.hasNext();) {
+            Map.Entry e = (Map.Entry) i.next();
+            put(e.getKey(), e.getValue());
+        }
+    }
+
+    /**
+     * Removes the mapping for this key from this map if present.
+     *
+     * @param key key whose mapping is to be removed from the map.
+     * @return previous value associated with specified key, or <tt>null</tt>
+     * if there was no mapping for key. A <tt>null</tt> return can
+     * also indicate that the map previously associated <tt>null</tt>
+     * with the specified key.
+     */
+    public Object remove(Object key) {
+        Entry e = removeEntryForKey(key);
+        return (e == null ? e : e.value);
+    }
+
+    /**
+     * Removes and returns the entry associated with the specified key in the
+     * ConcurrentHashMap. Returns null if the ConcurrentHashMap contains no
+     * mapping for this key.
+     */
+    private Entry removeEntryForKey(Object key) {
+        Object k = maskNull(key);
+        int hash = hash(k);
+        synchronized (this) {
+            int i = hash & (table.length - 1);
+            Entry e = table[i];
+
+            if (e == null) return null;
+            if (e.hash == hash && eq(k, e.key)) {
+                size--;
+                table[i] = e.next;
+                return e;
+            }
+
+            Entry prev = e;
+            for (e = e.next; e != null; prev = e, e = e.next) {
+                if (e.hash == hash && eq(k, e.key)) {
+                    size--;
+                    prev.next = e.next;
+                    return e;
+                }
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Special version of remove for EntrySet.
+     */
+    private Entry removeMapping(Object o) {
+        if (!(o instanceof Map.Entry)) return null;
+
+        Map.Entry entry = (Map.Entry) o;
+        Object k = maskNull(entry.getKey());
+        int hash = hash(k);
+        synchronized (this) {
+            int i = hash & (table.length - 1);
+            Entry e = table[i];
+
+            if (e == null) return null;
+            if (e.hash == hash && e.equals(entry)) {
+                size--;
+                table[i] = e.next;
+                return e;
+            }
+
+            Entry prev = e;
+            for (e = e.next; e != null; prev = e, e = e.next) {
+                if (e.hash == hash && e.equals(entry)) {
+                    size--;
+                    prev.next = e.next;
+                    return e;
+                }
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Removes all mappings from this map.
+     */
+    public synchronized void clear() {
+        table = new Entry[table.length];
+        size = 0;
+    }
+
+    /**
+     * Return an arbitrary entry index.
+     */
+    private int randomEntryIndex() {
+        if (randomEntry == RANDOMS.length)
+            randomEntry = 0;
+        return (int) (RANDOMS[randomEntry++] * table.length);
+    }
+
+    public Map.Entry removeRandom() {
+        if (size == 0)
+            return null;
+
+        synchronized (this) {
+            int random = randomEntryIndex();
+            int index = findEntry(random, random % 2 == 0, false);
+            if (index == -1)
+                return null;
+            Entry rem = table[index];
+            table[index] = rem.next;
+            size--;
+            return rem;
+        }
+    }
+
+    /**
+     * Find the index of the entry nearest the given index, starting in the
+     * given direction.
+     */
+    private int findEntry(int start, boolean forward, boolean searchedOther) {
+        if (forward) {
+            for (int i = start; i < table.length; i++)
+                if (table[i] != null)
+                    return i;
+            return (searchedOther || start == 0) ? -1
+                : findEntry(start - 1, false, true);
+        } else {
+            for (int i = start; i >= 0; i--)
+                if (table[i] != null)
+                    return i;
+            return (searchedOther || start == table.length - 1) ? -1
+                : findEntry(start + 1, true, true);
+        }
+    }
+
+    public Iterator randomEntryIterator() {
+        // pass index so calculated before iterator refs table, in case table
+        // gets replace with a larger one
+        return new HashIterator(ENTRIES, randomEntryIndex());
+    }
+
+    /**
+     * Returns <tt>true</tt> if this map maps one or more keys to the
+     * specified value.
+     *
+     * @param value value whose presence in this map is to be tested.
+     * @return <tt>true</tt> if this map maps one or more keys to the
+     * specified value.
+     */
+    public final boolean containsValue(Object value) {
+        if (value == null) return containsNullValue();
+
+        Entry tab[] = table;
+        for (int i = 0; i < tab.length; i++) {
+            for (Entry e = tab[i]; e != null; e = e.next) {
+                if (value.equals(e.value)) return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Special-case code for containsValue with null argument
+     */
+    private boolean containsNullValue() {
+        Entry tab[] = table;
+        for (int i = 0; i < tab.length; i++) {
+            for (Entry e = tab[i]; e != null; e = e.next) {
+                if (e.value == null) return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Returns a shallow copy of this <tt>ConcurrentHashMap</tt> instance: the
+     * keys and values themselves are not cloned.
+     *
+     * @return a shallow copy of this map.
+     */
+    public final Object clone() {
+        return new ConcurrentHashMap(this);
+    }
+
+    protected Entry createEntry(int h, Object k, Object v, Entry n) {
+        return new Entry(h, k, v, n);
+    }
+
+    protected static class Entry implements Map.Entry {
+
+        final Object key;
+        Object value;
+        final int hash;
+        Entry next;
+
+        /**
+         * Create new entry.
+         */
+        protected Entry(int h, Object k, Object v, Entry n) {
+            value = v;
+            next = n;
+            key = k;
+            hash = h;
+        }
+
+        public Object getKey() {
+            return unmaskNull(key);
+        }
+
+        public Object getValue() {
+            return value;
+        }
+
+        public Object setValue(Object newValue) {
+            Object oldValue = value;
+            value = newValue;
+            return oldValue;
+        }
+
+        public boolean equals(Object o) {
+            if (!(o instanceof Map.Entry)) return false;
+            Map.Entry e = (Map.Entry) o;
+            Object k1 = getKey();
+            Object k2 = e.getKey();
+            if (k1 == k2 || (k1 != null && k1.equals(k2))) {
+                Object v1 = getValue();
+                Object v2 = e.getValue();
+                if (v1 == v2 || (v1 != null && v1.equals(v2)))
+                    return true;
+            }
+            return false;
+        }
+
+        public int hashCode() {
+            return (key == NULL_KEY ? 0 : key.hashCode()) ^
+                (value == null ? 0 : value.hashCode());
+        }
+
+        public String toString() {
+            return getKey() + "=" + getValue();
+        }
+
+        protected Object clone() {
+            // It is the callers responsibility to set the next field
+            // correctly.
+            return new Entry(hash, key, value, null);
+        }
+    }
+
+    // Types of Enumerations/Iterations
+    private static final int KEYS = 0;
+    private static final int VALUES = 1;
+    private static final int ENTRIES = 2;
+
+    /**
+     * Map iterator.
+     */
+    private class HashIterator implements Iterator {
+
+        final Entry[] table = ConcurrentHashMap.this.table;
+        final int type;
+        int startIndex;
+        int stopIndex = 0;
+        int index;
+        Entry entry = null;
+        Entry lastReturned = null;
+
+        HashIterator(int type, int startIndex) {
+            this.type = type;
+            this.startIndex = startIndex;
+            index = startIndex;
+        }
+
+        public boolean hasNext() {
+            if (entry != null) {
+                return true;
+            }
+            while (index >= stopIndex) {
+                if ((entry = table[index--]) != null) {
+                    return true;
+                }
+            }
+            if (stopIndex == 0) {
+                index = table.length - 1;
+                stopIndex = startIndex + 1;
+                while (index >= stopIndex) {
+                    if ((entry = table[index--]) != null) {
+                        return true;
+                    }
+                }
+            }
+            return false;
+        }
+
+        public Object next() {
+            if (!hasNext())
+                throw new NoSuchElementException();
+            Entry e = lastReturned = entry;
+            entry = e.next;
+            return type == KEYS ? e.key : (type == VALUES ? e.value : e);
+        }
+
+        public void remove() {
+            if (lastReturned == null)
+                throw new IllegalStateException();
+            synchronized (ConcurrentHashMap.this) {
+                Entry[] tab = ConcurrentHashMap.this.table;
+                int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length;
+
+                for (Entry e = tab[index], prev = null; e != null;
+                    prev = e, e = e.next) {
+                    if (e == lastReturned) {
+                        if (prev == null)
+                            tab[index] = e.next;
+                        else
+                            prev.next = e.next;
+                        size--;
+                        lastReturned = null;
+                        return;
+                    }
+                }
+                throw new Error("Iterated off table when doing remove");
+            }
+        }
+    }
+
+    // Views
+
+    private transient Set entrySet = null;
+    private transient Set keySet = null;
+    private transient Collection values = null;
+
+    /**
+     * Returns a set view of the keys contained in this map. The set is
+     * backed by the map, so changes to the map are reflected in the set, and
+     * vice-versa. The set supports element removal, which removes the
+     * corresponding mapping from this map, via the <tt>Iterator.remove</tt>,
+     * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>,
and
+     * <tt>clear</tt> operations. It does not support the <tt>add</tt>
or
+     * <tt>addAll</tt> operations.
+     *
+     * @return a set view of the keys contained in this map.
+     */
+    public final Set keySet() {
+        Set ks = keySet;
+        return (ks != null ? ks : (keySet = new KeySet()));
+    }
+
+    private final class KeySet extends AbstractSet {
+
+        public Iterator iterator() {
+            return new HashIterator(KEYS, table.length - 1);
+        }
+
+        public int size() {
+            return size;
+        }
+
+        public boolean contains(Object o) {
+            return containsKey(o);
+        }
+
+        public boolean remove(Object o) {
+            return ConcurrentHashMap.this.removeEntryForKey(o) != null;
+        }
+
+        public void clear() {
+            ConcurrentHashMap.this.clear();
+        }
+    }
+
+    /**
+     * Returns a collection view of the values contained in this map. The
+     * collection is backed by the map, so changes to the map are reflected in
+     * the collection, and vice-versa. The collection supports element
+     * removal, which removes the corresponding mapping from this map, via the
+     * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
+     * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
operations.
+     * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
+     *
+     * @return a collection view of the values contained in this map.
+     */
+    public final Collection values() {
+        Collection vs = values;
+        return (vs != null ? vs : (values = new Values()));
+    }
+
+    private final class Values extends AbstractCollection {
+
+        public Iterator iterator() {
+            return new HashIterator(VALUES, table.length - 1);
+        }
+
+        public int size() {
+            return size;
+        }
+
+        public boolean contains(Object o) {
+            return containsValue(o);
+        }
+
+        public void clear() {
+            ConcurrentHashMap.this.clear();
+        }
+    }
+
+    /**
+     * Returns a collection view of the mappings contained in this map. Each
+     * element in the returned collection is a <tt>Map.Entry</tt>. The
+     * collection is backed by the map, so changes to the map are reflected in
+     * the collection, and vice-versa. The collection supports element
+     * removal, which removes the corresponding mapping from the map, via the
+     * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
+     * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
operations.
+     * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
+     *
+     * @return a collection view of the mappings contained in this map.
+     * @see Map.Entry
+     */
+    public final Set entrySet() {
+        Set es = entrySet;
+        return (es != null ? es : (entrySet = new EntrySet()));
+    }
+
+    private final class EntrySet extends AbstractSet {
+
+        public Iterator iterator() {
+            return new HashIterator(ENTRIES, table.length - 1);
+        }
+
+        public boolean contains(Object o) {
+            if (!(o instanceof Map.Entry)) return false;
+            Map.Entry e = (Map.Entry) o;
+            Entry candidate = getEntry(e.getKey());
+            return candidate != null && candidate.equals(e);
+        }
+
+        public boolean remove(Object o) {
+            return removeMapping(o) != null;
+        }
+
+        public int size() {
+            return size;
+        }
+
+        public void clear() {
+            ConcurrentHashMap.this.clear();
+        }
+    }
+
+    /**
+     * Save the state of the <tt>ConcurrentHashMap</tt> instance to a stream
+     * (i.e., serialize it).
+     *
+     * @serialData The <i>capacity</i> of the ConcurrentHashMap(the length of
+     * the bucket array) is emitted(int), followed by the <i>size</i> of the
+     * ConcurrentHashMap(the number of key-value mappings), followed by the key
+     * (Object) and value(Object) for each key-value mapping represented by the
+     * ConcurrentHashMap The key-value mappings are emitted in the order that
+     * they are returned by <tt>entrySet().iterator()</tt>.
+     */
+    private void writeObject(ObjectOutputStream s) throws IOException {
+        // Write out the threshold, loadfactor, and any hidden stuff
+        s.defaultWriteObject();
+
+        // Write out number of buckets
+        s.writeInt(table.length);
+
+        // Write out size(number of Mappings)
+        s.writeInt(size);
+        s.writeInt(maxSize);
+
+        // Write out keys and values(alternating)
+        for (Iterator i = entrySet().iterator(); i.hasNext();) {
+            Map.Entry e = (Map.Entry) i.next();
+            s.writeObject(e.getKey());
+            s.writeObject(e.getValue());
+        }
+    }
+
+    private static final long serialVersionUID = -6452706556724125778L;
+
+    /**
+     * Reconstitute the <tt>ConcurrentHashMap</tt> instance from a stream(i.e.,
+     * deserialize it).
+     */
+    private void readObject(ObjectInputStream s)
+        throws IOException, ClassNotFoundException {
+        // Read in the threshold, loadfactor, and any hidden stuff
+        s.defaultReadObject();
+
+        // Read in number of buckets and allocate the bucket array;
+        int numBuckets = s.readInt();
+        table = new Entry[numBuckets];
+
+        // Read in size(number of Mappings)
+        int size = s.readInt();
+        
+        // read the max size
+        maxSize = s.readInt();
+
+        // Read the keys and values, and put the mappings in the
+        // ConcurrentHashMap
+        for (int i = 0; i < size; i++) {
+            Object key = s.readObject();
+            Object value = s.readObject();
+            put(key, value);
+        }
+    }
+}

Propchange: openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/concurrent/ConcurrentHashMap.java
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