/*
* Copyright 1998-2000 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package com.sun.tools.jdi;
import java.io.*;
import java.util.*;
/**
* Hash table based implementation of the Map interface. This implementation
* provides all of the optional Map operations, and permits null values and
* the null key. (HashMap is roughly equivalent to Hashtable, except that it
* is unsynchronized and permits nulls.) In addition, elements in the map are
* ordered and doubly linked together.
* <p>
* This implementation provides constant-time performance for the basic
* operations (get and put), assuming the the hash function disperses the
* elements properly among the buckets. Iteration over Collection views
* requires time proportional to its size (the number of key-value mappings)
* and returns elements in the order they are linked. In a HashMap the
* iteration would require time proportional to the capacity of the map
* plus the map size.
* <p>
* An instance of LinkedHashMap has two parameters that affect its efficiency:
* its <i>capacity</i> and its <i>load factor</i>. The load factor should be
* between 0.0 and 1.0. When the number of mappings in the LinkedHashMap exceeds
* the product of the load factor and the current capacity, the capacity is
* increased by calling the rehash method which requires time proportional
* to the number of key-value mappings in the map. Larger load factors
* use memory more efficiently, at the expense of larger expected time per
* lookup.
* <p>
* If many mappings are to be stored in a LinkedHashMap, creating it with a
* sufficiently large capacity will allow the mappings to be stored more
* efficiently than letting it perform automatic rehashing as needed to grow
* the table.
* <p>
* <strong>Note that this implementation is not synchronized.</strong> If
* multiple threads access a LinkedHashMap concurrently, and at least one of the
* threads modifies the LinkedHashMap structurally, it <em>must</em> be
* synchronized externally. (A structural modification is any operation that
* adds or deletes one or more mappings; merely changing the value associated
* with a key that is already contained in the Table is not a structural
* modification.) This is typically accomplished by synchronizing on some
* object that naturally encapsulates the LinkedHashMap. If no such object
* exists, the LinkedHashMap should be "wrapped" using the
* Collections.synchronizedSet method. This is best done at creation time, to
* prevent accidental unsynchronized access to the LinkedHashMap:
* <pre>
* Map m = Collections.synchronizedMap(new LinkedHashMap(...));
* </pre>
* <p>
* The Iterators returned by the iterator methods of the Collections returned
* by all of LinkedHashMap's "collection view methods" are <em>fail-fast</em>:
* if the LinkedHashMap is structurally modified at any time after the Iterator
* is created, in any way except through the Iterator's own remove or add
* methods, the Iterator will throw a ConcurrentModificationException. Thus,
* in the face of concurrent modification, the Iterator fails quickly and
* cleanly, rather than risking arbitrary, non-deterministic behavior at an
* undetermined time in the future.
*
* @author Josh Bloch
* @author Arthur van Hoff
* @author Zhenghua Li
* @see Object#hashCode()
* @see java.util.Collection
* @see java.util.Map
* @see java.util.TreeMap
* @see java.util.Hashtable
* @see java.util.HashMap
*/
import java.io.Serializable;
public class LinkedHashMap extends AbstractMap implements Map, Serializable {
/**
* The hash table data.
*/
private transient Entry table[];
/**
* The head of the double linked list.
*/
private transient Entry header;
/**
* The total number of mappings in the hash table.
*/
private transient int count;
/**
* Rehashes the table when count exceeds this threshold.
*/
private int threshold;
/**
* The load factor for the LinkedHashMap.
*/
private float loadFactor;
/**
* The number of times this LinkedHashMap has been structurally modified
* Structural modifications are those that change the number of mappings in
* the LinkedHashMap or otherwise modify its internal structure (e.g.,
* rehash). This field is used to make iterators on Collection-views of
* the LinkedHashMap fail-fast. (See ConcurrentModificationException).
*/
private transient int modCount = 0;
/**
* Constructs a new, empty LinkedHashMap with the specified initial
* capacity and the specified load factor.
*
* @param initialCapacity the initial capacity of the LinkedHashMap.
* @param loadFactor a number between 0.0 and 1.0.
* @exception IllegalArgumentException if the initial capacity is less
* than or equal to zero, or if the load factor is less than
* or equal to zero.
*/
public LinkedHashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Initial Capacity: "+
initialCapacity);
if ((loadFactor > 1) || (loadFactor <= 0))
throw new IllegalArgumentException("Illegal Load factor: "+
loadFactor);
if (initialCapacity==0)
initialCapacity = 1;
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int)(initialCapacity * loadFactor);
header = new Entry(-1, null, null, null);
header.before = header.after = header;
}
/**
* Constructs a new, empty LinkedHashMap with the specified initial capacity
* and default load factor.
*
* @param initialCapacity the initial capacity of the LinkedHashMap.
*/
public LinkedHashMap(int initialCapacity) {
this(initialCapacity, 0.75f);
}
/**
* Constructs a new, empty LinkedHashMap with a default capacity and load
* factor.
*/
public LinkedHashMap() {
this(101, 0.75f);
}
/**
* Constructs a new LinkedHashMap with the same mappings as the given
* Map. The LinkedHashMap is created with a capacity of thrice the number
* of mappings in the given Map or 11 (whichever is greater), and a
* default load factor.
*/
public LinkedHashMap(Map t) {
this(Math.max(3*t.size(), 11), 0.75f);
putAll(t);
}
/**
* Returns the number of key-value mappings in this Map.
*/
public int size() {
return count;
}
/**
* Returns true if this Map contains no key-value mappings.
*/
public boolean isEmpty() {
return count == 0;
}
/**
* Returns true if this LinkedHashMap maps one or more keys to the specified
* value.
*
* @param value value whose presence in this Map is to be tested.
*/
public boolean containsValue(Object value) {
if (value==null) {
for (Entry e = header.after; e != header; e = e.after)
if (e.value==null)
return true;
} else {
for (Entry e = header.after; e != header; e = e.after)
if (value.equals(e.value))
return true;
}
return false;
}
/**
* Returns true if this LinkedHashMap contains a mapping for the specified
* key.
*
* @param key key whose presence in this Map is to be tested.
*/
public boolean containsKey(Object key) {
Entry tab[] = table;
if (key != null) {
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next)
if (e.hash==hash && e.key.equals(key))
return true;
} else {
for (Entry e = tab[0]; e != null; e = e.next)
if (e.key==null)
return true;
}
return false;
}
/**
* Returns the value to which this LinkedHashMap maps the specified key.
* Returns null if the LinkedHashMap contains no mapping for this key.
* A return value of null does not <em>necessarily</em> indicate that the
* LinkedHashMap contains no mapping for the key; it's also possible that
* the LinkedHashMap explicitly maps the key to null. The containsKey
* operation may be used to distinguish these two cases.
*
* @param key key whose associated value is to be returned.
*/
public Object get(Object key) {
Entry e = getEntry(key);
return e==null ? null : e.value;
}
/**
* Returns the entry associated with the specified key in the LinkedHashMap.
* Returns null if the LinkedHashMap contains no mapping for this key.
*/
private Entry getEntry(Object key) {
Entry tab[] = table;
if (key != null) {
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next)
if ((e.hash == hash) && e.key.equals(key))
return e;
} else {
for (Entry e = tab[0]; e != null; e = e.next)
if (e.key==null)
return e;
}
return null;
}
/**
* Rehashes the contents of the LinkedHashMap into a LinkedHashMap with a
* larger capacity. This method is called automatically when the
* number of keys in the LinkedHashMap exceeds this LinkedHashMap's capacity
* and load factor.
*/
private void rehash() {
int oldCapacity = table.length;
Entry oldMap[] = table;
int newCapacity = oldCapacity * 2 + 1;
Entry newMap[] = new Entry[newCapacity];
modCount++;
threshold = (int)(newCapacity * loadFactor);
table = newMap;
for (Entry e = header.after; e != header; e = e.after) {
int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newMap[index];
newMap[index] = e;
}
}
/**
* Remove an entry from the linked list.
*/
private void listRemove(Entry entry) {
if (entry == null) {
return;
}
entry.before.after = entry.after;
entry.after.before = entry.before;
}
/**
* Add the specified entry before the specified existing entry to
* the linked list.
*/
private void listAddBefore(Entry entry, Entry existEntry) {
entry.after = existEntry;
entry.before = existEntry.before;
entry.before.after = entry;
entry.after.before = entry;
}
/**
* Returns the position of the mapping for the specified key
* in the ordered map.
*
* @param key the specified key.
* @return index of the key mapping.
*/
public int indexOf(Object key) {
int i = 0;
if (key == null) {
for (Entry e = header.after; e != header; e = e.after, i++)
if (e.key == null)
return i;
} else {
for (Entry e = header.after; e != header; e = e.after, i++)
if(key.equals(e.key))
return i;
}
return -1;
}
/**
* Associates the specified value with the specified key in this
* LinkedHashMap. If the LinkedHashMap previously contained a mapping for
* this key, the old value is replaced and the position of this mapping
* entry in the double linked list remains the same. Otherwise, a new
* mapping entry is created and inserted into the list before the specified
* existing mapping entry. The method returns the previous value associated
* with the specified key, or null if there was no mapping for key. A null
* return can also indicate that the LinkedHashMap previously associated
* null with the specified key.
*/
private Object putAhead(Object key, Object value, Entry existEntry) {
// Makes sure the key is not already in the LinkedHashMap.
Entry tab[] = table;
int hash = 0;
int index = 0;
if (key != null) {
hash = key.hashCode();
index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
Object old = e.value;
e.value = value;
return old;
}
}
} else {
for (Entry e = tab[0] ; e != null ; e = e.next) {
if (e.key == null) {
Object old = e.value;
e.value = value;
return old;
}
}
}
modCount++;
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash();
tab = table;
index = (hash & 0x7FFFFFFF) % tab.length;
}
// Creates the new entry.
Entry e = new Entry(hash, key, value, tab[index]);
tab[index] = e;
listAddBefore(e, existEntry);
count++;
return null;
}
/**
* Associates the specified value with the specified key in this
* LinkedHashMap and position the mapping at the specified index.
* If the LinkedHashMap previously contained a mapping for this key,
* the old value is replaced and the position of this mapping entry
* in the double linked list remains the same. Otherwise, a new mapping
* entry is created and inserted into the list at the specified
* position.
*
* @param index the position to put the key-value mapping.
* @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 null if there
* was no mapping for key. A null return can also indicate that
* the LinkedHashMap previously associated null with the specified
* key.
*/
public Object put(int index, Object key, Object value) {
if (index < 0 || index > count)
throw new IndexOutOfBoundsException();
Entry e = header.after;
if (index == count)
return putAhead(key, value, header); //fast approach for append
else {
for (int i = 0; i < index; i++)
e = e.after;
return putAhead(key, value, e);
}
}
/**
* Associates the specified value with the specified key in this
* LinkedHashMap. If the LinkedHashMap previously contained a mapping for
* this key, the old value is replaced. The mapping entry is also appended
* to the end of the ordered linked list.
*
* @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 null if there
* was no mapping for key. A null return can also indicate that
* the LinkedHashMap previously associated null with the specified
* key.
*/
public Object put(Object key, Object value) {
return putAhead(key, value, header);
}
/**
* Removes the mapping for this key from this LinkedHashMap if present.
* The mapping would also be removed from the double linked list.
*
* @param key key whose mapping is to be removed from the Map.
* @return previous value associated with specified key, or null if there
* was no mapping for key. A null return can also indicate that
* the LinkedHashMap previously associated null with the specified
* key.
*/
public Object remove(Object key) {
Entry tab[] = table;
if (key != null) {
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index], prev = null; e != null;
prev = e, e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
modCount++;
if (prev != null)
prev.next = e.next;
else
tab[index] = e.next;
count--;
Object oldValue = e.value;
e.value = null;
listRemove(e);
return oldValue;
}
}
} else {
for (Entry e = tab[0], prev = null; e != null;
prev = e, e = e.next) {
if (e.key == null) {
modCount++;
if (prev != null)
prev.next = e.next;
else
tab[0] = e.next;
count--;
Object oldValue = e.value;
e.value = null;
listRemove(e);
return oldValue;
}
}
}
return null;
}
/**
* Copies all of the mappings from the specified Map to this LinkedHashMap
* These mappings will replace any mappings that this LinkedHashMap had for
* any of the keys currently in the specified Map.
*
* @param t Mappings to be stored in this Map.
*/
public void putAll(Map t) {
Iterator i = t.entrySet().iterator();
while (i.hasNext()) {
Map.Entry e = (Map.Entry) i.next();
put(e.getKey(), e.getValue());
}
}
/**
* Removes all mappings from this LinkedHashMap.
*/
public void clear() {
Entry tab[] = table;
modCount++;
for (int index = tab.length; --index >= 0; )
tab[index] = null;
count = 0;
header.before = header.after = header;
}
/**
* Returns a shallow copy of this LinkedHashMap. The keys and values
* themselves are not cloned.
*/
public Object clone() {
return new LinkedHashMap(this);
}
// Views
private transient Set keySet = null;
private transient Set entries = null;
private transient Collection values = null;
/**
* Returns a Set view of the keys contained in this LinkedHashMap. The Set
* is backed by the LinkedHashMap, so changes to the LinkedHashMap are
* reflected in the Set, and vice-versa. The Set supports element removal,
* which removes the corresponding mapping from the LinkedHashMap, via the
* Iterator.remove, Set.remove, removeAll retainAll, and clear operations.
* It does not support the add or addAll operations.
*/
public Set keySet() {
if (keySet == null) {
keySet = new AbstractSet() {
public Iterator iterator() {
return new HashIterator(KEYS);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
return LinkedHashMap.this.remove(o) != null;
}
public void clear() {
LinkedHashMap.this.clear();
}
};
}
return keySet;
}
/**
* Returns a Collection view of the values contained in this LinkedHashMap.
* The Collection is backed by the LinkedHashMap, so changes to the
* LinkedHashMap are reflected in the Collection, and vice-versa. The
* Collection supports element removal, which removes the corresponding
* mapping from the LinkedHashMap, via the Iterator.remove,
* Collection.remove, removeAll, retainAll and clear operations. It does
* not support the add or addAll operations.
*/
public Collection values() {
if (values==null) {
values = new AbstractCollection() {
public Iterator iterator() {
return new HashIterator(VALUES);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
LinkedHashMap.this.clear();
}
};
}
return values;
}
/**
* Returns a Collection view of the mappings contained in this
* LinkedHashMap. Each element in the returned collection is a Map.Entry.
* The Collection is backed by the LinkedHashMap, so changes to the
* LinkedHashMap are reflected in the Collection, and vice-versa. The
* Collection supports element removal, which removes the corresponding
* mapping from the LinkedHashMap, via the Iterator.remove,
* Collection.remove, removeAll, retainAll and clear operations. It does
* not support the add or addAll operations.
*
* @see java.util.Map.Entry
*/
public Set entrySet() {
if (entries==null) {
entries = new AbstractSet() {
public Iterator iterator() {
return new HashIterator(ENTRIES);
}
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry entry = (Map.Entry)o;
Object key = entry.getKey();
Entry tab[] = table;
int hash = (key==null ? 0 : key.hashCode());
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next)
if (e.hash==hash && e.equals(entry))
return true;
return false;
}
public boolean remove(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry entry = (Map.Entry)o;
Object key = entry.getKey();
Entry tab[] = table;
int hash = (key==null ? 0 : key.hashCode());
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index], prev = null; e != null;
prev = e, e = e.next) {
if (e.hash==hash && e.equals(entry)) {
modCount++;
if (prev != null)
prev.next = e.next;
else
tab[index] = e.next;
count--;
e.value = null;
listRemove(e);
return true;
}
}
return false;
}
public int size() {
return count;
}
public void clear() {
LinkedHashMap.this.clear();
}
};
}
return entries;
}
/**
* Compares the specified Object with this Map for equality.
* Returns true if the given object is also a LinkedHashMap and the two
* Maps represent the same mappings in the same order. More formally,
* two Maps <code>t1</code> and <code>t2</code> represent the same mappings
* if <code>t1.keySet().equals(t2.keySet())</code> and for every
* key <code>k</code> in <code>t1.keySet()</code>, <code>
* (t1.get(k)==null ? t2.get(k)==null : t1.get(k).equals(t2.get(k)))
* </code>.
* <p>
* This implementation first checks if the specified Object is this Map;
* if so it returns true. Then, it checks if the specified Object is
* a Map whose size is identical to the size of this Set; if not, it
* it returns false. If so, it iterates over this Map and the specified
* Map's entrySet() Collection, and checks that the specified Map contains
* each mapping that this Map contains at the same position. If the
* specified Map fails to contain such a mapping in the right order, false
* is returned. If the iteration completes, true is returned.
*
* @param o Object to be compared for equality with this Map.
* @return true if the specified Object is equal to this Map.
*
*/
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof LinkedHashMap))
return false;
LinkedHashMap t = (LinkedHashMap) o;
if (t.size() != size())
return false;
Iterator i1 = entrySet().iterator();
Iterator i2 = t.entrySet().iterator();
while (i1.hasNext()) {
Entry e1 = (Entry) i1.next();
Entry e2 = (Entry) i2.next();
Object key1 = e1.getKey();
Object value1 = e1.getValue();
Object key2 = e2.getKey();
Object value2 = e2.getValue();
if ((key1 == null ? key2 == null : key1.equals(key2)) &&
(value1 == null ? value2 == null : value1.equals(value2))) {
continue;
} else {
return false;
}
}
return true;
}
/**
* LinkedHashMap collision list entry.
*/
private static class Entry implements Map.Entry {
int hash;
Object key;
Object value;
Entry next;
// These fields comprise the doubly linked list that is used for
// iteration.
Entry before, after;
Entry(int hash, Object key, Object value, Entry next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
// Map.Entry Ops
public Object getKey() {
return key;
}
public Object getValue() {
return value;
}
public Object setValue(Object value) {
Object oldValue = this.value;
this.value = value;
return oldValue;
}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry)o;
return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
(value==null ? e.getValue()==null : value.equals(e.getValue()));
}
public int hashCode() {
return hash ^ (value==null ? 0 : value.hashCode());
}
public String toString() {
return key+"="+value;
}
}
// Types of Iterators
private static final int KEYS = 0;
private static final int VALUES = 1;
private static final int ENTRIES = 2;
private class HashIterator implements Iterator {
private Entry[] table = LinkedHashMap.this.table;
private Entry entry = null;
private Entry lastReturned = null;
private int type;
/**
* The modCount value that the iterator believes that the backing
* List should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
private int expectedModCount = modCount;
HashIterator(int type) {
this.type = type;
this.entry = LinkedHashMap.this.header.after;
}
public boolean hasNext() {
return entry != header;
}
public Object next() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
if (entry == LinkedHashMap.this.header)
throw new NoSuchElementException();
Entry e = lastReturned = entry;
entry = e.after;
return type == KEYS ? e.key : (type == VALUES ? e.value : e);
}
public void remove() {
if (lastReturned == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Entry[] tab = LinkedHashMap.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) {
modCount++;
expectedModCount++;
if (prev == null)
tab[index] = e.next;
else
prev.next = e.next;
count--;
listRemove(e);
lastReturned = null;
return;
}
}
throw new ConcurrentModificationException();
}
}
/**
* Save the state of the LinkedHashMap to a stream (i.e., serialize it).
* The objects will be written out in the order they are linked
* in the list.
*/
private void writeObject(java.io.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(count);
// Write out keys and values (alternating)
for (Entry e = header.after; e != header; e = e.after) {
s.writeObject(e.key);
s.writeObject(e.value);
}
}
/**
* Reconstitute the LinkedHashMap from a stream (i.e., deserialize it).
*/
private void readObject(java.io.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];
header = new Entry(-1, null, null, null);
header.before = header;
header.after = header;
// Read in size (number of Mappings)
int size = s.readInt();
// Read the keys and values, and put the mappings in the LinkedHashMap
for (int i=0; i<size; i++) {
Object key = s.readObject();
Object value = s.readObject();
put(key, value);
}
}
}