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/* Copyright (c) 2008, Nathan Sweet
* 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 Esoteric Software 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 HOLDER 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 com.esotericsoftware.kryo.util;
/** An unordered map where identity comparison is used for keys and the values are ints. This implementation is a cuckoo hash map
* using 3 hashes, random walking, and a small stash for problematic keys. Null keys are not allowed. No allocation is done except
* when growing the table size.
*
* This map performs very fast get, containsKey, and remove (typically O(1), worst case O(log(n))). Put may be a bit slower,
* depending on hash collisions. Load factors greater than 0.91 greatly increase the chances the map will have to rehash to the
* next higher POT size.
* @author Nathan Sweet */
public class IdentityObjectIntMap {
private static final int PRIME1 = 0xbe1f14b1;
private static final int PRIME2 = 0xb4b82e39;
private static final int PRIME3 = 0xced1c241;
public int size;
K[] keyTable;
int[] valueTable;
int capacity, stashSize;
private float loadFactor;
private int hashShift, mask, threshold;
private int stashCapacity;
private int pushIterations;
/** Creates a new map with an initial capacity of 32 and a load factor of 0.8. This map will hold 25 items before growing the
* backing table. */
public IdentityObjectIntMap () {
this(32, 0.8f);
}
/** Creates a new map with a load factor of 0.8. This map will hold initialCapacity * 0.8 items before growing the backing
* table. */
public IdentityObjectIntMap (int initialCapacity) {
this(initialCapacity, 0.8f);
}
/** Creates a new map with the specified initial capacity and load factor. This map will hold initialCapacity * loadFactor items
* before growing the backing table. */
public IdentityObjectIntMap (int initialCapacity, float loadFactor) {
if (initialCapacity < 0) throw new IllegalArgumentException("initialCapacity must be >= 0: " + initialCapacity);
if (capacity > 1 << 30) throw new IllegalArgumentException("initialCapacity is too large: " + initialCapacity);
capacity = ObjectMap.nextPowerOfTwo(initialCapacity);
if (loadFactor <= 0) throw new IllegalArgumentException("loadFactor must be > 0: " + loadFactor);
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
mask = capacity - 1;
hashShift = 31 - Integer.numberOfTrailingZeros(capacity);
stashCapacity = Math.max(3, (int)Math.ceil(Math.log(capacity)) * 2);
pushIterations = Math.max(Math.min(capacity, 8), (int)Math.sqrt(capacity) / 8);
keyTable = (K[])new Object[capacity + stashCapacity];
valueTable = new int[keyTable.length];
}
public void put (K key, int value) {
if (key == null) throw new IllegalArgumentException("key cannot be null.");
K[] keyTable = this.keyTable;
// Check for existing keys.
int hashCode = System.identityHashCode(key);
int index1 = hashCode & mask;
K key1 = keyTable[index1];
if (key == key1) {
valueTable[index1] = value;
return;
}
int index2 = hash2(hashCode);
K key2 = keyTable[index2];
if (key == key2) {
valueTable[index2] = value;
return;
}
int index3 = hash3(hashCode);
K key3 = keyTable[index3];
if (key == key3) {
valueTable[index3] = value;
return;
}
// Update key in the stash.
for (int i = capacity, n = i + stashSize; i < n; i++) {
if (keyTable[i] == key) {
valueTable[i] = value;
return;
}
}
// Check for empty buckets.
if (key1 == null) {
keyTable[index1] = key;
valueTable[index1] = value;
if (size++ >= threshold) resize(capacity << 1);
return;
}
if (key2 == null) {
keyTable[index2] = key;
valueTable[index2] = value;
if (size++ >= threshold) resize(capacity << 1);
return;
}
if (key3 == null) {
keyTable[index3] = key;
valueTable[index3] = value;
if (size++ >= threshold) resize(capacity << 1);
return;
}
push(key, value, index1, key1, index2, key2, index3, key3);
}
/** Skips checks for existing keys. */
private void putResize (K key, int value) {
// Check for empty buckets.
int hashCode = System.identityHashCode(key);
int index1 = hashCode & mask;
K key1 = keyTable[index1];
if (key1 == null) {
keyTable[index1] = key;
valueTable[index1] = value;
if (size++ >= threshold) resize(capacity << 1);
return;
}
int index2 = hash2(hashCode);
K key2 = keyTable[index2];
if (key2 == null) {
keyTable[index2] = key;
valueTable[index2] = value;
if (size++ >= threshold) resize(capacity << 1);
return;
}
int index3 = hash3(hashCode);
K key3 = keyTable[index3];
if (key3 == null) {
keyTable[index3] = key;
valueTable[index3] = value;
if (size++ >= threshold) resize(capacity << 1);
return;
}
push(key, value, index1, key1, index2, key2, index3, key3);
}
private void push (K insertKey, int insertValue, int index1, K key1, int index2, K key2, int index3, K key3) {
K[] keyTable = this.keyTable;
int[] valueTable = this.valueTable;
int mask = this.mask;
// Push keys until an empty bucket is found.
K evictedKey;
int evictedValue;
int i = 0, pushIterations = this.pushIterations;
do {
// Replace the key and value for one of the hashes.
switch (ObjectMap.random.nextInt(3)) {
case 0:
evictedKey = key1;
evictedValue = valueTable[index1];
keyTable[index1] = insertKey;
valueTable[index1] = insertValue;
break;
case 1:
evictedKey = key2;
evictedValue = valueTable[index2];
keyTable[index2] = insertKey;
valueTable[index2] = insertValue;
break;
default:
evictedKey = key3;
evictedValue = valueTable[index3];
keyTable[index3] = insertKey;
valueTable[index3] = insertValue;
break;
}
// If the evicted key hashes to an empty bucket, put it there and stop.
int hashCode = System.identityHashCode(evictedKey);
index1 = hashCode & mask;
key1 = keyTable[index1];
if (key1 == null) {
keyTable[index1] = evictedKey;
valueTable[index1] = evictedValue;
if (size++ >= threshold) resize(capacity << 1);
return;
}
index2 = hash2(hashCode);
key2 = keyTable[index2];
if (key2 == null) {
keyTable[index2] = evictedKey;
valueTable[index2] = evictedValue;
if (size++ >= threshold) resize(capacity << 1);
return;
}
index3 = hash3(hashCode);
key3 = keyTable[index3];
if (key3 == null) {
keyTable[index3] = evictedKey;
valueTable[index3] = evictedValue;
if (size++ >= threshold) resize(capacity << 1);
return;
}
if (++i == pushIterations) break;
insertKey = evictedKey;
insertValue = evictedValue;
} while (true);
putStash(evictedKey, evictedValue);
}
private void putStash (K key, int value) {
if (stashSize == stashCapacity) {
// Too many pushes occurred and the stash is full, increase the table size.
resize(capacity << 1);
put(key, value);
return;
}
// Store key in the stash.
int index = capacity + stashSize;
keyTable[index] = key;
valueTable[index] = value;
stashSize++;
size++;
}
/** @param defaultValue Returned if the key was not associated with a value. */
public int get (K key, int defaultValue) {
int hashCode = System.identityHashCode(key);
int index = hashCode & mask;
if (key != keyTable[index]) {
index = hash2(hashCode);
if (key != keyTable[index]) {
index = hash3(hashCode);
if (key != keyTable[index]) return getStash(key, defaultValue);
}
}
return valueTable[index];
}
private int getStash (K key, int defaultValue) {
K[] keyTable = this.keyTable;
for (int i = capacity, n = i + stashSize; i < n; i++)
if (key == keyTable[i]) return valueTable[i];
return defaultValue;
}
/** Returns the key's current value and increments the stored value. If the key is not in the map, defaultValue + increment is
* put into the map. */
public int getAndIncrement (K key, int defaultValue, int increment) {
int hashCode = System.identityHashCode(key);
int index = hashCode & mask;
if (key != keyTable[index]) {
index = hash2(hashCode);
if (key != keyTable[index]) {
index = hash3(hashCode);
if (key != keyTable[index]) return getAndIncrementStash(key, defaultValue, increment);
}
}
int value = valueTable[index];
valueTable[index] = value + increment;
return value;
}
private int getAndIncrementStash (K key, int defaultValue, int increment) {
K[] keyTable = this.keyTable;
for (int i = capacity, n = i + stashSize; i < n; i++)
if (key == keyTable[i]) {
int value = valueTable[i];
valueTable[i] = value + increment;
return value;
}
put(key, defaultValue + increment);
return defaultValue;
}
public int remove (K key, int defaultValue) {
int hashCode = System.identityHashCode(key);
int index = hashCode & mask;
if (key == keyTable[index]) {
keyTable[index] = null;
int oldValue = valueTable[index];
size--;
return oldValue;
}
index = hash2(hashCode);
if (key == keyTable[index]) {
keyTable[index] = null;
int oldValue = valueTable[index];
size--;
return oldValue;
}
index = hash3(hashCode);
if (key == keyTable[index]) {
keyTable[index] = null;
int oldValue = valueTable[index];
size--;
return oldValue;
}
return removeStash(key, defaultValue);
}
int removeStash (K key, int defaultValue) {
K[] keyTable = this.keyTable;
for (int i = capacity, n = i + stashSize; i < n; i++) {
if (key == keyTable[i]) {
int oldValue = valueTable[i];
removeStashIndex(i);
size--;
return oldValue;
}
}
return defaultValue;
}
void removeStashIndex (int index) {
// If the removed location was not last, move the last tuple to the removed location.
stashSize--;
int lastIndex = capacity + stashSize;
if (index < lastIndex) {
keyTable[index] = keyTable[lastIndex];
valueTable[index] = valueTable[lastIndex];
}
}
/** Reduces the size of the backing arrays to be the specified capacity or less. If the capacity is already less, nothing is
* done. If the map contains more items than the specified capacity, nothing is done. */
public void shrink (int maximumCapacity) {
if (maximumCapacity < 0) throw new IllegalArgumentException("maximumCapacity must be >= 0: " + maximumCapacity);
if (size > maximumCapacity) maximumCapacity = size;
if (capacity <= maximumCapacity) return;
maximumCapacity = ObjectMap.nextPowerOfTwo(maximumCapacity);
resize(maximumCapacity);
}
/** Clears the map and reduces the size of the backing arrays to be the specified capacity if they are larger. */
public void clear (int maximumCapacity) {
if (capacity <= maximumCapacity) {
clear();
return;
}
size = 0;
resize(maximumCapacity);
}
public void clear () {
K[] keyTable = this.keyTable;
for (int i = capacity + stashSize; i-- > 0;)
keyTable[i] = null;
size = 0;
stashSize = 0;
}
/** Returns true if the specified value is in the map. Note this traverses the entire map and compares every value, which may be
* an expensive operation. */
public boolean containsValue (int value) {
int[] valueTable = this.valueTable;
for (int i = capacity + stashSize; i-- > 0;)
if (valueTable[i] == value) return true;
return false;
}
public boolean containsKey (K key) {
int hashCode = System.identityHashCode(key);
int index = hashCode & mask;
if (key != keyTable[index]) {
index = hash2(hashCode);
if (key != keyTable[index]) {
index = hash3(hashCode);
if (key != keyTable[index]) return containsKeyStash(key);
}
}
return true;
}
private boolean containsKeyStash (K key) {
K[] keyTable = this.keyTable;
for (int i = capacity, n = i + stashSize; i < n; i++)
if (key == keyTable[i]) return true;
return false;
}
/** Returns the key for the specified value, or null if it is not in the map. Note this traverses the entire map and compares
* every value, which may be an expensive operation. */
public K findKey (int value) {
int[] valueTable = this.valueTable;
for (int i = capacity + stashSize; i-- > 0;)
if (valueTable[i] == value) return keyTable[i];
return null;
}
/** Increases the size of the backing array to acommodate the specified number of additional items. Useful before adding many
* items to avoid multiple backing array resizes. */
public void ensureCapacity (int additionalCapacity) {
int sizeNeeded = size + additionalCapacity;
if (sizeNeeded >= threshold) resize(ObjectMap.nextPowerOfTwo((int)(sizeNeeded / loadFactor)));
}
private void resize (int newSize) {
int oldEndIndex = capacity + stashSize;
capacity = newSize;
threshold = (int)(newSize * loadFactor);
mask = newSize - 1;
hashShift = 31 - Integer.numberOfTrailingZeros(newSize);
stashCapacity = Math.max(3, (int)Math.ceil(Math.log(newSize)) * 2);
pushIterations = Math.max(Math.min(newSize, 8), (int)Math.sqrt(newSize) / 8);
K[] oldKeyTable = keyTable;
int[] oldValueTable = valueTable;
keyTable = (K[])new Object[newSize + stashCapacity];
valueTable = new int[newSize + stashCapacity];
int oldSize = size;
size = 0;
stashSize = 0;
if (oldSize > 0) {
for (int i = 0; i < oldEndIndex; i++) {
K key = oldKeyTable[i];
if (key != null) putResize(key, oldValueTable[i]);
}
}
}
private int hash2 (int h) {
h *= PRIME2;
return (h ^ h >>> hashShift) & mask;
}
private int hash3 (int h) {
h *= PRIME3;
return (h ^ h >>> hashShift) & mask;
}
public String toString () {
if (size == 0) return "{}";
StringBuilder buffer = new StringBuilder(32);
buffer.append('{');
K[] keyTable = this.keyTable;
int[] valueTable = this.valueTable;
int i = keyTable.length;
while (i-- > 0) {
K key = keyTable[i];
if (key == null) continue;
buffer.append(key);
buffer.append('=');
buffer.append(valueTable[i]);
break;
}
while (i-- > 0) {
K key = keyTable[i];
if (key == null) continue;
buffer.append(", ");
buffer.append(key);
buffer.append('=');
buffer.append(valueTable[i]);
}
buffer.append('}');
return buffer.toString();
}
}
