org.apache.activemq.artemis.utils.collections.ConcurrentLongHashSet Maven / Gradle / Ivy
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*
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* 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
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* under the License.
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package org.apache.activemq.artemis.utils.collections;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.locks.StampedLock;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.invoke.MethodHandles;
import static org.apache.activemq.artemis.utils.Preconditions.checkArgument;
/**
* Concurrent hash set for primitive longs
*
* Provides similar methods as a ConcurrentSet<Long> but since it's an open hash map with linear probing, no node
* allocations are required to store the values.
*
* Items MUST be >= 0.
*/
public class ConcurrentLongHashSet {
private static final Logger logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
private static final long EmptyItem = -1L;
private static final long DeletedItem = -2L;
private static final float SetFillFactor = 0.66f;
private static final int DefaultExpectedItems = 256;
private static final int DefaultConcurrencyLevel = 16;
private final Section[] sections;
public interface ConsumerLong {
void accept(long item);
}
public ConcurrentLongHashSet() {
this(DefaultExpectedItems);
}
public ConcurrentLongHashSet(int expectedItems) {
this(expectedItems, DefaultConcurrencyLevel);
}
public ConcurrentLongHashSet(int expectedItems, final int numSections) {
checkArgument(numSections > 0);
if (expectedItems < numSections) {
expectedItems = numSections;
}
int perSectionExpectedItems = expectedItems / numSections;
int perSectionCapacity = (int) (perSectionExpectedItems / SetFillFactor);
this.sections = new Section[numSections];
for (int i = 0; i < numSections; i++) {
sections[i] = new Section(perSectionCapacity);
}
}
public int size() {
int size = 0;
for (Section s : sections) {
//read-acquire s.size that was write-released by s.unlockWrite
s.tryOptimisticRead();
//a stale value won't hurt: anyway it's subject to concurrent modifications
size += s.size;
}
return size;
}
public long capacity() {
long capacity = 0;
for (Section s : sections) {
capacity += s.capacity;
}
return capacity;
}
public boolean isEmpty() {
for (Section s : sections) {
//read-acquire s.size that was write-released by s.unlockWrite
s.tryOptimisticRead();
//a stale value won't hurt: anyway it's subject to concurrent modifications
if (s.size != 0) {
return false;
}
}
return true;
}
long getUsedBucketCount() {
long usedBucketCount = 0;
for (Section s : sections) {
usedBucketCount += s.usedBuckets;
}
return usedBucketCount;
}
public boolean contains(long item) {
if (!moreThanZero(item)) {
return false;
}
long h = hash(item);
return getSection(h).contains(item, (int) h);
}
public boolean add(long item) {
if (!moreThanZero(item)) {
return false;
}
long h = hash(item);
return getSection(h).add(item, (int) h);
}
/**
* Remove an existing entry if found
*
* @param item
* @return true if removed or false if item was not present
*/
public boolean remove(long item) {
if (!moreThanZero(item)) {
return false;
}
long h = hash(item);
return getSection(h).remove(item, (int) h);
}
private Section getSection(long hash) {
// Use 32 msb out of long to get the section
final int sectionIdx = (int) (hash >>> 32) & (sections.length - 1);
return sections[sectionIdx];
}
public void clear() {
for (Section s : sections) {
s.clear();
}
}
public void forEach(ConsumerLong processor) {
for (Section s : sections) {
s.forEach(processor);
}
}
/**
* @return a new list of all keys (makes a copy)
*/
public Set items() {
Set items = new HashSet<>();
forEach(items::add);
return items;
}
// A section is a portion of the hash map that is covered by a single
@SuppressWarnings("serial")
private static final class Section extends StampedLock {
private static final AtomicIntegerFieldUpdater CAPACITY_UPDATER = AtomicIntegerFieldUpdater.newUpdater(Section.class, "capacity");
// Keys and values are stored interleaved in the table array
private long[] table;
private volatile int capacity;
private int size;
private int usedBuckets;
private int resizeThreshold;
Section(int capacity) {
this.capacity = alignToPowerOfTwo(capacity);
this.table = new long[this.capacity];
this.size = 0;
this.usedBuckets = 0;
this.resizeThreshold = (int) (this.capacity * SetFillFactor);
Arrays.fill(table, EmptyItem);
}
boolean contains(long item, int hash) {
long stamp = tryOptimisticRead();
boolean acquiredLock = false;
int bucket = signSafeMod(hash, capacity);
try {
while (true) {
// First try optimistic locking
long storedItem = table[bucket];
if (!acquiredLock && validate(stamp)) {
// The values we have read are consistent
if (item == storedItem) {
return true;
} else if (storedItem == EmptyItem) {
// Not found
return false;
}
} else {
// Fallback to acquiring read lock
if (!acquiredLock) {
stamp = readLock();
acquiredLock = true;
bucket = signSafeMod(hash, capacity);
storedItem = table[bucket];
}
if (item == storedItem) {
return true;
} else if (storedItem == EmptyItem) {
// Not found
return false;
}
}
bucket = (bucket + 1) & (table.length - 1);
}
} finally {
if (acquiredLock) {
unlockRead(stamp);
}
}
}
@SuppressWarnings("NonAtomicVolatileUpdate")
boolean add(long item, long hash) {
long stamp = writeLock();
int bucket = signSafeMod(hash, capacity);
// Remember where we find the first available spot
int firstDeletedItem = -1;
try {
while (true) {
long storedItem = table[bucket];
if (item == storedItem) {
// Item was already in set
return false;
} else if (storedItem == EmptyItem) {
// Found an empty bucket. This means the key is not in the map. If we've already seen a deleted
// key, we should write at that position
if (firstDeletedItem != -1) {
bucket = firstDeletedItem;
} else {
++usedBuckets;
}
table[bucket] = item;
++size;
return true;
} else if (storedItem == DeletedItem) {
// The bucket contained a different deleted key
if (firstDeletedItem == -1) {
firstDeletedItem = bucket;
}
}
bucket = (bucket + 1) & (table.length - 1);
}
} finally {
if (usedBuckets > resizeThreshold) {
try {
rehash();
} finally {
unlockWrite(stamp);
}
} else {
unlockWrite(stamp);
}
}
}
@SuppressWarnings("NonAtomicVolatileUpdate")
private boolean remove(long item, int hash) {
long stamp = writeLock();
int bucket = signSafeMod(hash, capacity);
try {
while (true) {
long storedItem = table[bucket];
if (item == storedItem) {
--size;
cleanBucket(bucket);
return true;
} else if (storedItem == EmptyItem) {
// Key wasn't found
return false;
}
bucket = (bucket + 1) & (table.length - 1);
}
} finally {
unlockWrite(stamp);
}
}
private void cleanBucket(int bucket) {
int nextInArray = (bucket + 1) & (table.length - 1);
if (table[nextInArray] == EmptyItem) {
table[bucket] = EmptyItem;
--usedBuckets;
} else {
table[bucket] = DeletedItem;
}
}
void clear() {
long stamp = writeLock();
try {
Arrays.fill(table, EmptyItem);
this.size = 0;
this.usedBuckets = 0;
} finally {
unlockWrite(stamp);
}
}
public void forEach(ConsumerLong processor) {
long stamp = tryOptimisticRead();
long[] table = this.table;
boolean acquiredReadLock = false;
try {
// Validate no rehashing
if (!validate(stamp)) {
// Fallback to read lock
stamp = readLock();
acquiredReadLock = true;
table = this.table;
}
// Go through all the buckets for this section
for (int bucket = 0; bucket < table.length; bucket++) {
long storedItem = table[bucket];
if (!acquiredReadLock && !validate(stamp)) {
// Fallback to acquiring read lock
stamp = readLock();
acquiredReadLock = true;
storedItem = table[bucket];
}
if (storedItem != DeletedItem && storedItem != EmptyItem) {
processor.accept(storedItem);
}
}
} finally {
if (acquiredReadLock) {
unlockRead(stamp);
}
}
}
private void rehash() {
// Expand the hashmap
int newCapacity = capacity * 2;
long[] newTable = new long[newCapacity];
Arrays.fill(newTable, EmptyItem);
// Re-hash table
for (int i = 0; i < table.length; i++) {
long storedItem = table[i];
if (storedItem != EmptyItem && storedItem != DeletedItem) {
insertKeyValueNoLock(newTable, newCapacity, storedItem);
}
}
table = newTable;
usedBuckets = size;
CAPACITY_UPDATER.lazySet(this, newCapacity);
resizeThreshold = (int) (newCapacity * SetFillFactor);
}
private static void insertKeyValueNoLock(long[] table, int capacity, long item) {
int bucket = signSafeMod(hash(item), capacity);
while (true) {
long storedKey = table[bucket];
if (storedKey == EmptyItem) {
// The bucket is empty, so we can use it
table[bucket] = item;
return;
}
bucket = (bucket + 1) & (table.length - 1);
}
}
}
private static final long HashMixer = 0xc6a4a7935bd1e995L;
private static final int R = 47;
static long hash(long key) {
long hash = key * HashMixer;
hash ^= hash >>> R;
hash *= HashMixer;
return hash;
}
static int signSafeMod(long n, int Max) {
return (int) (n & (Max - 1));
}
static int alignToPowerOfTwo(int n) {
return (int) Math.pow(2, 32 - Integer.numberOfLeadingZeros(n - 1));
}
static boolean moreThanZero(long n) {
if (n < 0L) {
logger.warn("Keys and values must be >= 0, while it was {}, entry will be ignored", n, new Exception("invalid record " + n));
return false;
} else {
return true;
}
}
}