439 lines
16 KiB
Java
439 lines
16 KiB
Java
/*
|
|
* Copyright 2018 dorkbox, llc.
|
|
*
|
|
* Licensed 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 dorkbox.collections;
|
|
|
|
import static dorkbox.collections.IntMap.*;
|
|
|
|
import java.util.HashMap;
|
|
import java.util.Iterator;
|
|
import java.util.Map;
|
|
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
|
|
|
|
/**
|
|
* A bimap (or "bidirectional map") is a map that preserves the uniqueness of its values as well as that of its keys. This constraint
|
|
* enables bimaps to support an "inverse view", which is another bimap containing the same entries as this bimap but with reversed keys and values.
|
|
*
|
|
* This class uses the "single-writer-principle" for lock-free publication.
|
|
*
|
|
* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
|
|
* one thread, or only one thread can access it at a time) -- we chose the 2nd option -- and use 'synchronized' to make sure that only
|
|
* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
|
|
* manner.
|
|
*
|
|
* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
|
|
* contended writes.
|
|
*
|
|
* This data structure is for many-read/few-write scenarios
|
|
*/
|
|
public
|
|
class LockFreeIntBiMap<V> {
|
|
// Recommended for best performance while adhering to the "single writer principle". Must be static-final
|
|
private static final AtomicReferenceFieldUpdater<LockFreeIntBiMap, IntMap> forwardREF = AtomicReferenceFieldUpdater.newUpdater(
|
|
LockFreeIntBiMap.class,
|
|
IntMap.class,
|
|
"forwardHashMap");
|
|
|
|
private static final AtomicReferenceFieldUpdater<LockFreeIntBiMap, ObjectIntMap> reverseREF = AtomicReferenceFieldUpdater.newUpdater(
|
|
LockFreeIntBiMap.class,
|
|
ObjectIntMap.class,
|
|
"reverseHashMap");
|
|
|
|
private volatile IntMap<V> forwardHashMap;
|
|
private volatile ObjectIntMap<V> reverseHashMap;
|
|
|
|
private final int defaultReturnValue;
|
|
private final LockFreeObjectIntBiMap<V> inverse;
|
|
|
|
// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
|
|
// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
|
|
// use-case 99% of the time)
|
|
|
|
// public static
|
|
// void main(String[] args) {
|
|
// LockFreeIntBiMap<String> test = new LockFreeIntBiMap<String>();
|
|
// String one = "One";
|
|
// String four = "Four";
|
|
//
|
|
// test.put(1, one);
|
|
// test.put(2, "Two");
|
|
// test.put(3, "Three");
|
|
// test.put(4, four);
|
|
// // try {
|
|
// // test.put(1, four);
|
|
// // } catch (IllegalArgumentException e) {
|
|
// // }
|
|
// test.putForce(1, four);
|
|
// test.put(5, one);
|
|
//
|
|
// System.out.println(test.toString());
|
|
//
|
|
// System.out.println("Reverse");
|
|
// System.out.println(test.inverse().toString());
|
|
// }
|
|
|
|
/**
|
|
* Creates a new bimap using @{link Integer#MIN_VALUE}.
|
|
*/
|
|
public
|
|
LockFreeIntBiMap() {
|
|
this(Integer.MIN_VALUE);
|
|
}
|
|
|
|
/**
|
|
* The default return value is used for various get/put operations on the IntMap/ObjectIntMap.
|
|
*
|
|
* @param defaultReturnValue value used for various get/put operations on the IntMap/ObjectIntMap.
|
|
*/
|
|
public
|
|
LockFreeIntBiMap(int defaultReturnValue) {
|
|
this(new IntMap<V>(), new ObjectIntMap<V>(), defaultReturnValue);
|
|
}
|
|
|
|
/**
|
|
* The default return value is used for various get/put operations on the IntMap/ObjectIntMap.
|
|
*
|
|
* @param defaultReturnValue value used for various get/put operations on the IntMap/ObjectIntMap.
|
|
*/
|
|
public
|
|
LockFreeIntBiMap(IntMap<V> forwardHashMap, ObjectIntMap<V> reverseHashMap, int defaultReturnValue) {
|
|
this.forwardHashMap = forwardHashMap;
|
|
this.reverseHashMap = reverseHashMap;
|
|
this.defaultReturnValue = defaultReturnValue;
|
|
|
|
this.inverse = new LockFreeObjectIntBiMap<V>(reverseHashMap, forwardHashMap, defaultReturnValue, this);
|
|
}
|
|
|
|
LockFreeIntBiMap(final IntMap<V> forwardHashMap,
|
|
final ObjectIntMap<V> reverseHashMap,
|
|
final int defaultReturnValue,
|
|
final LockFreeObjectIntBiMap<V> inverse) {
|
|
|
|
this.forwardHashMap = forwardHashMap;
|
|
this.reverseHashMap = reverseHashMap;
|
|
this.defaultReturnValue = defaultReturnValue;
|
|
this.inverse = inverse;
|
|
}
|
|
|
|
/**
|
|
* Removes all of the mappings from this bimap.
|
|
* The bimap will be empty after this call returns.
|
|
*/
|
|
public synchronized
|
|
void clear() {
|
|
forwardHashMap.clear();
|
|
reverseHashMap.clear();
|
|
}
|
|
|
|
/**
|
|
* @return the inverse view of this bimap, which maps each of this bimap's values to its associated key.
|
|
*/
|
|
public
|
|
LockFreeObjectIntBiMap<V> inverse() {
|
|
return inverse;
|
|
}
|
|
|
|
/**
|
|
* Associates the specified value with the specified key in this bimap.
|
|
* If the bimap previously contained a mapping for the key, the old
|
|
* value is replaced. If the given value is already bound to a different
|
|
* key in this bimap, the bimap will remain unmodified. To avoid throwing
|
|
* an exception, call {@link #putForce(int, Object)} putForce(K, V) instead.
|
|
*
|
|
* @param key key with which the specified value is to be associated
|
|
* @param value value to be associated with the specified key
|
|
*
|
|
* @return the previous value associated with <tt>key</tt>, or
|
|
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
|
|
* (A <tt>null</tt> return can also indicate that the map
|
|
* previously associated <tt>null</tt> with <tt>key</tt>.)
|
|
*
|
|
* @throws IllegalArgumentException if the given value is already bound to a different key in this bimap. The bimap will remain
|
|
* unmodified in this event. To avoid this exception, call {@link #putForce(int, Object)} putForce(K, V) instead.
|
|
*/
|
|
public synchronized
|
|
V put(final int key, final V value) throws IllegalArgumentException {
|
|
V prevForwardValue = this.forwardHashMap.put(key, value);
|
|
if (prevForwardValue != null) {
|
|
reverseHashMap.remove(prevForwardValue, defaultReturnValue);
|
|
}
|
|
|
|
int prevReverseValue = this.reverseHashMap.get(value, defaultReturnValue);
|
|
this.reverseHashMap.put(value, key);
|
|
if (prevReverseValue != defaultReturnValue) {
|
|
// put the old value back
|
|
if (prevForwardValue != null) {
|
|
this.forwardHashMap.put(key, prevForwardValue);
|
|
}
|
|
else {
|
|
this.forwardHashMap.remove(key);
|
|
}
|
|
|
|
this.reverseHashMap.put(value, prevReverseValue);
|
|
|
|
throw new IllegalArgumentException("Value already exists. Keys and values must both be unique!");
|
|
}
|
|
|
|
return prevForwardValue;
|
|
}
|
|
|
|
/**
|
|
* Associates the specified value with the specified key in this bimap.
|
|
* If the bimap previously contained a mapping for the key, the old
|
|
* value is replaced. This is an alternate form of {@link #put(int, Object)}
|
|
* that will silently ignore duplicates
|
|
*
|
|
* @param key key with which the specified value is to be associated
|
|
* @param value value to be associated with the specified key
|
|
*
|
|
* @return the previous value associated with <tt>key</tt>, or
|
|
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
|
|
* (A <tt>null</tt> return can also indicate that the map
|
|
* previously associated <tt>null</tt> with <tt>key</tt>.)
|
|
*/
|
|
public synchronized
|
|
V putForce(final int key, final V value) {
|
|
V prevForwardValue = this.forwardHashMap.put(key, value);
|
|
if (prevForwardValue != null) {
|
|
reverseHashMap.remove(prevForwardValue, defaultReturnValue);
|
|
}
|
|
|
|
|
|
int prevReverseValue = this.reverseHashMap.get(value, defaultReturnValue);
|
|
this.reverseHashMap.put(value, key);
|
|
|
|
if (prevReverseValue != defaultReturnValue) {
|
|
forwardHashMap.remove(prevReverseValue);
|
|
}
|
|
|
|
return prevForwardValue;
|
|
}
|
|
|
|
/**
|
|
* Copies all of the mappings from the specified map to this map.
|
|
* These mappings will replace any mappings that this map had for
|
|
* any of the keys currently in the specified map.
|
|
*
|
|
* @param hashMap mappings to be stored in this map
|
|
*
|
|
* @throws NullPointerException if the specified map is null
|
|
*
|
|
* @throws IllegalArgumentException if the given value is already bound to a different key in this bimap. The bimap will remain
|
|
* unmodified in this event. To avoid this exception, call {@link #putAllForce(Map)} instead.
|
|
*/
|
|
public synchronized
|
|
void putAll(final Map<Integer, V> hashMap) throws IllegalArgumentException {
|
|
LockFreeIntBiMap<V> biMap = new LockFreeIntBiMap<V>();
|
|
|
|
try {
|
|
for (Map.Entry<Integer, V> entry : hashMap.entrySet()) {
|
|
Integer key = entry.getKey();
|
|
V value = entry.getValue();
|
|
|
|
biMap.put(key, value);
|
|
|
|
// we have to verify that the keys/values between the bimaps are unique
|
|
if (this.forwardHashMap.containsKey(key)) {
|
|
throw new IllegalArgumentException("Key already exists. Keys and values must both be unique!");
|
|
}
|
|
|
|
if (this.reverseHashMap.containsKey(value)) {
|
|
throw new IllegalArgumentException("Value already exists. Keys and values must both be unique!");
|
|
}
|
|
}
|
|
} catch (IllegalArgumentException e) {
|
|
// do nothing if there is an exception
|
|
throw e;
|
|
}
|
|
|
|
|
|
// we have checked to make sure that the bimap is unique, AND have checked that we don't already have any of the key/values in ourselves
|
|
this.forwardHashMap.putAll(biMap.forwardHashMap);
|
|
this.reverseHashMap.putAll(biMap.reverseHashMap);
|
|
}
|
|
|
|
/**
|
|
* Copies all of the mappings from the specified map to this map.
|
|
* These mappings will replace any mappings that this map had for
|
|
* any of the keys currently in the specified map. This is an alternate
|
|
* form of {@link #putAll(Map)} putAll(K, V) that will silently
|
|
* ignore duplicates
|
|
*
|
|
* @param hashMap mappings to be stored in this map
|
|
*
|
|
* @throws NullPointerException if the specified map is null
|
|
*/
|
|
public synchronized
|
|
void putAllForce(final Map<Integer, V> hashMap) {
|
|
for (Map.Entry<Integer, V> entry : hashMap.entrySet()) {
|
|
Integer key = entry.getKey();
|
|
V value = entry.getValue();
|
|
|
|
putForce(key, value);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Removes the mapping for the specified key from this map if present.
|
|
*
|
|
* @param key key whose mapping is to be removed from the map
|
|
*
|
|
* @return the previous value associated with <tt>key</tt>, or
|
|
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
|
|
* (A <tt>null</tt> return can also indicate that the map
|
|
* previously associated <tt>null</tt> with <tt>key</tt>.)
|
|
*/
|
|
public synchronized
|
|
V remove(final int key) {
|
|
V value = forwardHashMap.remove(key);
|
|
if (value != null) {
|
|
reverseHashMap.remove(value, defaultReturnValue);
|
|
}
|
|
return value;
|
|
}
|
|
|
|
|
|
/**
|
|
* Returns the value to which the specified key is mapped,
|
|
* or {@code null} if this map contains no mapping for the key.
|
|
* <p>
|
|
* <p>More formally, if this map contains a mapping from a key
|
|
* {@code k} to a value {@code v} such that {@code (key==null ? k==null :
|
|
* key.equals(k))}, then this method returns {@code v}; otherwise
|
|
* it returns {@code null}. (There can be at most one such mapping.)
|
|
* <p>
|
|
* <p>A return value of {@code null} does not <i>necessarily</i>
|
|
* indicate that the map contains no mapping for the key; it's also
|
|
* possible that the map explicitly maps the key to {@code null}.
|
|
* The {@link HashMap#containsKey containsKey} operation may be used to
|
|
* distinguish these two cases.
|
|
*
|
|
* @see #put(int, Object)
|
|
*/
|
|
@SuppressWarnings("unchecked")
|
|
public
|
|
V get(final int key) {
|
|
// use the SWP to get a lock-free get of the value
|
|
return (V) forwardREF.get(this).get(key);
|
|
}
|
|
|
|
/**
|
|
* Returns <tt>true</tt> if this bimap contains no key-value mappings.
|
|
*
|
|
* @return <tt>true</tt> if this bimap contains no key-value mappings
|
|
*/
|
|
public
|
|
boolean isEmpty() {
|
|
// use the SWP to get a lock-free get of the value
|
|
return forwardREF.get(this)
|
|
.size == 0;
|
|
}
|
|
|
|
/**
|
|
* Returns the number of key-value mappings in this map. If the
|
|
* map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
|
|
* <tt>Integer.MAX_VALUE</tt>.
|
|
*
|
|
* @return the number of key-value mappings in this map
|
|
*/
|
|
public
|
|
int size() {
|
|
// use the SWP to get a lock-free get of the value
|
|
return forwardREF.get(this)
|
|
.size;
|
|
}
|
|
|
|
/**
|
|
* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
|
|
*
|
|
* Returns an iterator for the keys in the map. Remove is supported. Note that the same iterator instance is returned each
|
|
* time this method is called. Use the {@link Entries} constructor for nested or multithreaded iteration.
|
|
*/
|
|
public
|
|
Keys keys() {
|
|
return forwardREF.get(this)
|
|
.keys();
|
|
}
|
|
|
|
/**
|
|
* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
|
|
*
|
|
* Returns an iterator for the values in the map. Remove is supported. Note that the same iterator instance is returned each
|
|
* time this method is called. Use the {@link Entries} constructor for nested or multithreaded iteration.
|
|
*/
|
|
@SuppressWarnings("unchecked")
|
|
public
|
|
Values<V> values() {
|
|
return forwardREF.get(this)
|
|
.values();
|
|
}
|
|
|
|
/**
|
|
* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
|
|
*
|
|
* Returns an iterator for the entries in the map. Remove is supported. Note that the same iterator instance is returned each
|
|
* time this method is called. Use the {@link Entries} constructor for nested or multithreaded iteration.
|
|
*/
|
|
public
|
|
Entries entries() {
|
|
return forwardREF.get(this)
|
|
.entries();
|
|
}
|
|
|
|
/**
|
|
* Identity equals only!
|
|
*/
|
|
@Override
|
|
public
|
|
boolean equals(final Object o) {
|
|
return this == o;
|
|
}
|
|
|
|
@Override
|
|
public
|
|
int hashCode() {
|
|
int result = forwardREF.get(this).hashCode();
|
|
result = 31 * result + reverseREF.get(this).hashCode();
|
|
result = 31 * result + defaultReturnValue;
|
|
return result;
|
|
}
|
|
|
|
@Override
|
|
public
|
|
String toString() {
|
|
StringBuilder builder = new StringBuilder("LockFreeIntBiMap {");
|
|
|
|
Keys keys = keys();
|
|
Iterator<V> values = values();
|
|
|
|
while (keys.hasNext) {
|
|
builder.append(keys.next());
|
|
builder.append(" (")
|
|
.append(values.next())
|
|
.append("), ");
|
|
}
|
|
|
|
int length = builder.length();
|
|
if (length > 1) {
|
|
// delete the ', '
|
|
builder.delete(length - 2, length);
|
|
}
|
|
|
|
builder.append('}');
|
|
|
|
return builder.toString();
|
|
}
|
|
}
|