/*
* Copyright (c) 2004, Oracle and/or its affiliates. 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package sun.util;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.NoSuchElementException;
/**
* A precomputed hash map.
*
* <p> Subclasses of this class are of the following form:
*
* <blockquote><pre>
* class FooMap
* extends sun.util.PreHashedMap<String>
* {
*
* private FooMap() {
* super(ROWS, SIZE, SHIFT, MASK);
* }
*
* protected void init(Object[] ht) {
* ht[0] = new Object[] { "key-1", value_1 };
* ht[1] = new Object[] { "key-2", value_2,
* new Object { "key-3", value_3 } };
* ...
* }
*
* }</pre></blockquote>
*
* <p> The <tt>init</tt> method is invoked by the <tt>PreHashedMap</tt>
* constructor with an object array long enough for the map's rows. The method
* must construct the hash chain for each row and store it in the appropriate
* element of the array.
*
* <p> Each entry in the map is represented by a unique hash-chain node. The
* final node of a hash chain is a two-element object array whose first element
* is the entry's key and whose second element is the entry's value. A
* non-final node of a hash chain is a three-element object array whose first
* two elements are the entry's key and value and whose third element is the
* next node in the chain.
*
* <p> Instances of this class are mutable and are not safe for concurrent
* access. They may be made immutable and thread-safe via the appropriate
* methods in the {@link java.util.Collections} utility class.
*
* <p> In the JDK build, subclasses of this class are typically created via the
* <tt>Hasher</tt> program in the <tt>make/tools/Hasher</tt> directory.
*
* @author Mark Reinhold
* @since 1.5
*
* @see java.util.AbstractMap
*/
public abstract class PreHashedMap<V>
extends AbstractMap<String,V>
{
private final int rows;
private final int size;
private final int shift;
private final int mask;
private final Object[] ht;
/**
* Creates a new map.
*
* <p> This constructor invokes the {@link #init init} method, passing it a
* newly-constructed row array that is <tt>rows</tt> elements long.
*
* @param rows
* The number of rows in the map
* @param size
* The number of entries in the map
* @param shift
* The value by which hash codes are right-shifted
* @param mask
* The value with which hash codes are masked after being shifted
*/
protected PreHashedMap(int rows, int size, int shift, int mask) {
this.rows = rows;
this.size = size;
this.shift = shift;
this.mask = mask;
this.ht = new Object[rows];
init(ht);
}
/**
* Initializes this map.
*
* <p> This method must construct the map's hash chains and store them into
* the appropriate elements of the given hash-table row array.
*
* @param rows
* The row array to be initialized
*/
protected abstract void init(Object[] ht);
// @SuppressWarnings("unchecked")
private V toV(Object x) {
return (V)x;
}
public V get(Object k) {
int h = (k.hashCode() >> shift) & mask;
Object[] a = (Object[])ht[h];
if (a == null) return null;
for (;;) {
if (a[0].equals(k))
return toV(a[1]);
if (a.length < 3)
return null;
a = (Object[])a[2];
}
}
/**
* @throws UnsupportedOperationException
* If the given key is not part of this map's initial key set
*/
public V put(String k, V v) {
int h = (k.hashCode() >> shift) & mask;
Object[] a = (Object[])ht[h];
if (a == null)
throw new UnsupportedOperationException(k);
for (;;) {
if (a[0].equals(k)) {
V ov = toV(a[1]);
a[1] = v;
return ov;
}
if (a.length < 3)
throw new UnsupportedOperationException(k);
a = (Object[])a[2];
}
}
public Set<String> keySet() {
return new AbstractSet<String> () {
public int size() {
return size;
}
public Iterator<String> iterator() {
return new Iterator<String>() {
private int i = -1;
Object[] a = null;
String cur = null;
private boolean findNext() {
if (a != null) {
if (a.length == 3) {
a = (Object[])a[2];
cur = (String)a[0];
return true;
}
i++;
a = null;
}
cur = null;
if (i >= rows)
return false;
if (i < 0 || ht[i] == null) {
do {
if (++i >= rows)
return false;
} while (ht[i] == null);
}
a = (Object[])ht[i];
cur = (String)a[0];
return true;
}
public boolean hasNext() {
if (cur != null)
return true;
return findNext();
}
public String next() {
if (cur == null) {
if (!findNext())
throw new NoSuchElementException();
}
String s = cur;
cur = null;
return s;
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
};
}
public Set<Map.Entry<String,V>> entrySet() {
return new AbstractSet<Map.Entry<String,V>> () {
public int size() {
return size;
}
public Iterator<Map.Entry<String,V>> iterator() {
return new Iterator<Map.Entry<String,V>>() {
final Iterator<String> i = keySet().iterator();
public boolean hasNext() {
return i.hasNext();
}
public Map.Entry<String,V> next() {
return new Map.Entry<String,V>() {
String k = i.next();
public String getKey() { return k; }
public V getValue() { return get(k); }
public int hashCode() {
V v = get(k);
return (k.hashCode()
+ (v == null
? 0
: v.hashCode()));
}
public boolean equals(Object ob) {
if (ob == this)
return true;
if (!(ob instanceof Map.Entry))
return false;
Map.Entry<String,V> that
= (Map.Entry<String,V>)ob;
return ((this.getKey() == null
? that.getKey() == null
: this.getKey()
.equals(that.getKey()))
&&
(this.getValue() == null
? that.getValue() == null
: this.getValue()
.equals(that.getValue())));
}
public V setValue(V v) {
throw new UnsupportedOperationException();
}
};
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
};
}
}