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/*
* Copyright (C) 2009, Google Inc.
* Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
* Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
* and other copyright owners as documented in the project's IP log.
*
* This program and the accompanying materials are made available
* under the terms of the Eclipse Distribution License v1.0 which
* accompanies this distribution, is reproduced below, and is
* available at http://www.eclipse.org/org/documents/edl-v10.php
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* - Neither the name of the Eclipse Foundation, Inc. nor the
* names of its contributors may be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.eclipse.jgit.lib;
import java.util.Iterator;
/**
* Fast, efficient map specifically for {@link ObjectId} subclasses.
* <p>
* This map provides an efficient translation from any ObjectId instance to a
* cached subclass of ObjectId that has the same value.
* <p>
* Raw value equality is tested when comparing two ObjectIds (or subclasses),
* not reference equality and not <code>.equals(Object)</code> equality. This
* allows subclasses to override <code>equals</code> to supply their own
* extended semantics.
*
* @param <V>
* type of subclass of ObjectId that will be stored in the map.
*/
public class ObjectIdSubclassMap<V extends ObjectId> implements Iterable<V> {
private int size;
private V[] obj_hash;
/** Create an empty map. */
public ObjectIdSubclassMap() {
obj_hash = createArray(32);
}
/** Remove all entries from this map. */
public void clear() {
size = 0;
obj_hash = createArray(32);
}
/**
* Lookup an existing mapping.
*
* @param toFind
* the object identifier to find.
* @return the instance mapped to toFind, or null if no mapping exists.
*/
public V get(final AnyObjectId toFind) {
int i = index(toFind);
V obj;
while ((obj = obj_hash[i]) != null) {
if (AnyObjectId.equals(obj, toFind))
return obj;
if (++i == obj_hash.length)
i = 0;
}
return null;
}
/**
* Store an object for future lookup.
* <p>
* An existing mapping for <b>must not</b> be in this map. Callers must
* first call {@link #get(AnyObjectId)} to verify there is no current
* mapping prior to adding a new mapping.
*
* @param newValue
* the object to store.
* @param
* <Q>
* type of instance to store.
*/
public <Q extends V> void add(final Q newValue) {
if (obj_hash.length - 1 <= size * 2)
grow();
insert(newValue);
size++;
}
/**
* @return number of objects in map
*/
public int size() {
return size;
}
public Iterator<V> iterator() {
return new Iterator<V>() {
private int found;
private int i;
public boolean hasNext() {
return found < size;
}
public V next() {
while (i < obj_hash.length) {
final V v = obj_hash[i++];
if (v != null) {
found++;
return v;
}
}
throw new IllegalStateException();
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
private final int index(final AnyObjectId id) {
return (id.w1 >>> 1) % obj_hash.length;
}
private void insert(final V newValue) {
int j = index(newValue);
while (obj_hash[j] != null) {
if (++j >= obj_hash.length)
j = 0;
}
obj_hash[j] = newValue;
}
private void grow() {
final V[] old_hash = obj_hash;
final int old_hash_size = obj_hash.length;
obj_hash = createArray(2 * old_hash_size);
for (int i = 0; i < old_hash_size; i++) {
final V obj = old_hash[i];
if (obj != null)
insert(obj);
}
}
@SuppressWarnings("unchecked")
private final V[] createArray(final int sz) {
return (V[]) new ObjectId[sz];
}
}
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