/*
* 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.jdbm;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Hash Map which uses primitive long as key.
* Main advantage is new instanceof of Long does not have to be created for each lookup.
* <p/>
* This code comes from Android, which in turns comes from Apache Harmony.
* This class was modified to use primitive longs and stripped down to consume less space.
* <p/>
* Author of JDBM modifications: Jan Kotek
*/
class LongHashMap<V> implements Serializable {
private static final long serialVersionUID = 362499999763181265L;
private int elementCount;
private Entry<V>[] elementData;
private final float loadFactor;
private int threshold;
private int defaultSize = 16;
private transient Entry<V> reuseAfterDelete = null;
static final class Entry<V> implements Serializable{
private static final long serialVersionUID = 362445231113181265L;
Entry<V> next;
V value;
long key;
Entry(long theKey) {
this.key = theKey;
this.value = null;
}
}
static class HashMapIterator<V> implements Iterator<V> {
private int position = 0;
boolean canRemove = false;
Entry<V> entry;
Entry<V> lastEntry;
final LongHashMap<V> associatedMap;
HashMapIterator(LongHashMap<V> hm) {
associatedMap = hm;
}
public boolean hasNext() {
if (entry != null) {
return true;
}
Entry<V>[] elementData = associatedMap.elementData;
int length = elementData.length;
int newPosition = position;
boolean result = false;
while (newPosition < length) {
if (elementData[newPosition] == null) {
newPosition++;
} else {
result = true;
break;
}
}
position = newPosition;
return result;
}
public V next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
Entry<V> result;
Entry<V> _entry = entry;
if (_entry == null) {
result = lastEntry = associatedMap.elementData[position++];
entry = lastEntry.next;
} else {
if (lastEntry.next != _entry) {
lastEntry = lastEntry.next;
}
result = _entry;
entry = _entry.next;
}
canRemove = true;
return result.value;
}
public void remove() {
if (!canRemove) {
throw new IllegalStateException();
}
canRemove = false;
if (lastEntry.next == entry) {
while (associatedMap.elementData[--position] == null) {
// Do nothing
}
associatedMap.elementData[position] = associatedMap.elementData[position].next;
entry = null;
} else {
lastEntry.next = entry;
}
if (lastEntry != null) {
Entry<V> reuse = lastEntry;
lastEntry = null;
reuse.key = Long.MIN_VALUE;
reuse.value = null;
associatedMap.reuseAfterDelete = reuse;
}
associatedMap.elementCount--;
}
}
@SuppressWarnings("unchecked")
private Entry<V>[] newElementArray(int s) {
return new Entry[s];
}
/**
* Constructs a new empty {@code HashMap} instance.
*
* @since Android 1.0
*/
public LongHashMap() {
this(16);
}
/**
* Constructs a new {@code HashMap} instance with the specified capacity.
*
* @param capacity the initial capacity of this hash map.
* @throws IllegalArgumentException when the capacity is less than zero.
* @since Android 1.0
*/
public LongHashMap(int capacity) {
defaultSize = capacity;
if (capacity >= 0) {
elementCount = 0;
elementData = newElementArray(capacity == 0 ? 1 : capacity);
loadFactor = 0.75f; // Default load factor of 0.75
computeMaxSize();
} else {
throw new IllegalArgumentException();
}
}
// BEGIN android-changed
/**
* Removes all mappings from this hash map, leaving it empty.
*
* @see #isEmpty
* @see #size
* @since Android 1.0
*/
public void clear() {
if (elementCount > 0) {
elementCount = 0;
}
if(elementData.length>1024 && elementData.length>defaultSize)
elementData = new Entry[defaultSize];
else
Arrays.fill(elementData, null);
computeMaxSize();
}
// END android-changed
/**
* Returns a shallow copy of this map.
*
* @return a shallow copy of this map.
* @since Android 1.0
*/
private void computeMaxSize() {
threshold = (int) (elementData.length * loadFactor);
}
/**
* Returns the value of the mapping with the specified key.
*
* @param key the key.
* @return the value of the mapping with the specified key, or {@code null}
* if no mapping for the specified key is found.
* @since Android 1.0
*/
public V get(final long key) {
final int hash = powerHash(key);
final int index = (hash & 0x7FFFFFFF) % elementData.length;
//find non null entry
Entry<V> m = elementData[index];
while (m != null) {
if (key == m.key)
return m.value;
m = m.next;
}
return null;
}
/**
* Returns whether this map is empty.
*
* @return {@code true} if this map has no elements, {@code false}
* otherwise.
* @see #size()
* @since Android 1.0
*/
public boolean isEmpty() {
return elementCount == 0;
}
/**
* @return iterator over keys
*/
// public Iterator<K> keyIterator(){
// return new HashMapIterator<K, K, V>(
// new MapEntry.Type<K, K, V>() {
// public K get(Entry<K, V> entry) {
// return entry.key;
// }
// }, HashMap.this);
//
// }
/**
* Maps the specified key to the specified value.
*
* @param key the key.
* @param value the value.
* @return the value of any previous mapping with the specified key or
* {@code null} if there was no such mapping.
* @since Android 1.0
*/
public V put(final long key, final V value) {
int hash = powerHash(key);
int index = (hash & 0x7FFFFFFF) % elementData.length;
//find non null entry
Entry<V> entry = elementData[index];
while (entry != null && key != entry.key) {
entry = entry.next;
}
if (entry == null) {
if (++elementCount > threshold) {
rehash();
index = (hash & 0x7FFFFFFF) % elementData.length;
}
entry = createHashedEntry(key, index);
}
V result = entry.value;
entry.value = value;
return result;
}
Entry<V> createHashedEntry(final long key, final int index) {
Entry<V> entry = reuseAfterDelete;
if (entry == null) {
entry = new Entry<V>(key);
} else {
reuseAfterDelete = null;
entry.key = key;
entry.value = null;
}
entry.next = elementData[index];
elementData[index] = entry;
return entry;
}
void rehash(final int capacity) {
int length = (capacity == 0 ? 1 : capacity << 1);
Entry<V>[] newData = newElementArray(length);
for (int i = 0; i < elementData.length; i++) {
Entry<V> entry = elementData[i];
while (entry != null) {
int index = ((int) powerHash(entry.key) & 0x7FFFFFFF) % length;
Entry<V> next = entry.next;
entry.next = newData[index];
newData[index] = entry;
entry = next;
}
}
elementData = newData;
computeMaxSize();
}
void rehash() {
rehash(elementData.length);
}
/**
* Removes the mapping with the specified key from this map.
*
* @param key the key of the mapping to remove.
* @return the value of the removed mapping or {@code null} if no mapping
* for the specified key was found.
* @since Android 1.0
*/
public V remove(final long key) {
Entry<V> entry = removeEntry(key);
if (entry == null)
return null;
V ret = entry.value;
entry.value = null;
entry.key = Long.MIN_VALUE;
reuseAfterDelete = entry;
return ret;
}
Entry<V> removeEntry(final long key) {
Entry<V> last = null;
final int hash = powerHash(key);
final int index = (hash & 0x7FFFFFFF) % elementData.length;
Entry<V> entry = elementData[index];
while (true) {
if (entry == null) {
return null;
}
if (key == entry.key) {
if (last == null) {
elementData[index] = entry.next;
} else {
last.next = entry.next;
}
elementCount--;
return entry;
}
last = entry;
entry = entry.next;
}
}
/**
* Returns the number of elements in this map.
*
* @return the number of elements in this map.
* @since Android 1.0
*/
public int size() {
return elementCount;
}
/**
* @returns iterator over values in map
*/
public Iterator<V> valuesIterator() {
return new HashMapIterator<V>(this);
}
static final private int powerHash(final long key){
int h = (int)(key ^ (key >>> 32));
h ^= (h >>> 20) ^ (h >>> 12);
return h ^ (h >>> 7) ^ (h >>> 4);
}
}