/*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
*/
/*
* The initial version of this file was copied from JSR-166:
* http://gee.cs.oswego.edu/dl/concurrency-interest/
*/
package org.jsr166;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.ignite.internal.util.tostring.GridToStringExclude;
import org.apache.ignite.internal.util.typedef.internal.S;
import org.jetbrains.annotations.Nullable;
import static org.jsr166.ConcurrentLinkedHashMap.QueuePolicy.PER_SEGMENT_Q;
import static org.jsr166.ConcurrentLinkedHashMap.QueuePolicy.PER_SEGMENT_Q_OPTIMIZED_RMV;
import static org.jsr166.ConcurrentLinkedHashMap.QueuePolicy.SINGLE_Q;
/**
* A hash table supporting full concurrency of retrievals and
* adjustable expected concurrency for updates. This class obeys the
* same functional specification as {@link java.util.Hashtable}, and
* includes versions of methods corresponding to each method of
* <tt>Hashtable</tt>. However, even though all operations are
* thread-safe, retrieval operations do <em>not</em> entail locking,
* and there is <em>not</em> any support for locking the entire table
* in a way that prevents all access. This class is fully
* interoperable with <tt>Hashtable</tt> in programs that rely on its
* thread safety but not on its synchronization details.
*
* <p> Retrieval operations (including <tt>get</tt>) generally do not
* block, so may overlap with update operations (including
* <tt>put</tt> and <tt>remove</tt>). Retrievals reflect the results
* of the most recently <em>completed</em> update operations holding
* upon their onset. For aggregate operations such as <tt>putAll</tt>
* and <tt>clear</tt>, concurrent retrievals may reflect insertion or
* removal of only some entries. Similarly, Iterators and
* Enumerations return elements reflecting the state of the hash table
* at some point at or since the creation of the iterator/enumeration.
* They do <em>not</em> throw {@link ConcurrentModificationException}.
* However, iterators are designed to be used by only one thread at a time.
*
* <p> The allowed concurrency among update operations is guided by
* the optional <tt>concurrencyLevel</tt> constructor argument
* (default <tt>16</tt>), which is used as a hint for internal sizing. The
* table is internally partitioned to try to permit the indicated
* number of concurrent updates without contention. Because placement
* in hash tables is essentially random, the actual concurrency will
* vary. Ideally, you should choose a value to accommodate as many
* threads as will ever concurrently modify the table. Using a
* significantly higher value than you need can waste space and time,
* and a significantly lower value can lead to thread contention. But
* overestimates and underestimates within an order of magnitude do
* not usually have much noticeable impact. A value of one is
* appropriate when it is known that only one thread will modify and
* all others will only read. Also, resizing this or any other kind of
* hash table is a relatively slow operation, so, when possible, it is
* a good idea to provide estimates of expected table sizes in
* constructors.
*
* <p/> This implementation differs from
* <tt>HashMap</tt> in that it maintains a doubly-linked list running through
* all of its entries. This linked list defines the iteration ordering,
* which is the order in which keys were inserted into the map
* (<i>insertion-order</i>).
*
* <p> NOTE: Access order is not supported by this map.
*
* Note that insertion order is not affected
* if a key is <i>re-inserted</i> into the map. (A key <tt>k</tt> is
* reinserted into a map <tt>m</tt> if <tt>m.put(k, v)</tt> is invoked when
* <tt>m.containsKey(k)</tt> would return <tt>true</tt> immediately prior to
* the invocation.)
*
* <p>An optional {@code maxCap} may be passed to the map constructor to
* create bounded map that will remove stale mappings automatically when new mappings
* are added to the map.
*
* <p/>When iterating over the key set in insertion order one should note that iterator
* will see all removes done since the iterator was created, but will see <b>no</b>
* inserts to map.
*
* <p>This class and its views and iterators implement all of the
* <em>optional</em> methods of the {@link Map} and {@link Iterator}
* interfaces.
*
* <p> Like {@link Hashtable} but unlike {@link HashMap}, this class
* does <em>not</em> allow <tt>null</tt> to be used as a key or value.
*
* @author Doug Lea
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*/
@SuppressWarnings("NullableProblems")
public class ConcurrentLinkedHashMap<K, V> extends AbstractMap<K, V> implements ConcurrentMap<K, V> {
/*
* The basic strategy is to subdivide the table among Segments,
* each of which itself is a concurrently readable hash table.
*/
/* ---------------- Constants -------------- */
/**
* The default initial capacity for this table,
* used when not otherwise specified in a constructor.
*/
public static final int DFLT_INIT_CAP = 16;
/**
* The default load factor for this table, used when not
* otherwise specified in a constructor.
*/
public static final float DFLT_LOAD_FACTOR = 0.75f;
/**
* The default concurrency level for this table, used when not
* otherwise specified in a constructor.
*/
public static final int DFLT_CONCUR_LVL = 16;
/**
* The maximum capacity, used if a higher value is implicitly
* specified by either of the constructors with arguments. MUST
* be a power of two <= 1<<30 to ensure that entries are indexable
* using ints.
*/
public static final int MAX_CAP_LIMIT = 1 << 30;
/**
* The maximum number of segments to allow; used to bound
* constructor arguments.
*/
public static final int MAX_SEGS = 1 << 16; // slightly conservative
/**
* Number of unsynchronized retries in {@link #size} and {@link #containsValue}
* methods before resorting to locking. This is used to avoid
* unbounded retries if tables undergo continuous modification
* which would make it impossible to obtain an accurate result.
*/
public static final int RETRIES_BEFORE_LOCK = 2;
/* ---------------- Fields -------------- */
/**
* Mask value for indexing into segments. The upper bits of a
* key's hash code are used to choose the segment.
*/
private final int segmentMask;
/** Shift value for indexing within segments. */
private final int segmentShift;
/** The segments, each of which is a specialized hash table. */
private final Segment<K, V>[] segments;
/** Key set. */
private Set<K> keySet;
/** Key set. */
private Set<K> descKeySet;
/** Entry set */
private Set<Map.Entry<K, V>> entrySet;
/** Entry set in descending order. */
private Set<Map.Entry<K, V>> descEntrySet;
/** Values collection. */
private Collection<V> vals;
/** Values collection in descending order. */
private Collection<V> descVals;
/** Queue containing order of entries. */
private final ConcurrentLinkedDeque8<HashEntry<K, V>> entryQ;
/** Atomic variable containing map size. */
private final LongAdder8 size = new LongAdder8();
/** */
private final LongAdder8 modCnt = new LongAdder8();
/** */
private final int maxCap;
/** */
private final QueuePolicy qPlc;
/* ---------------- Small Utilities -------------- */
/**
* Applies a supplemental hash function to a given hashCode, which
* defends against poor quality hash functions. This is critical
* because ConcurrentHashMap uses power-of-two length hash tables,
* that otherwise encounter collisions for hashCodes that do not
* differ in lower or upper bits.
*
* @param h Input hash.
* @return Hash.
*/
private static int hash(int h) {
// Apply base step of MurmurHash; see http://code.google.com/p/smhasher/
// Despite two multiplies, this is often faster than others
// with comparable bit-spread properties.
h ^= h >>> 16;
h *= 0x85ebca6b;
h ^= h >>> 13;
h *= 0xc2b2ae35;
return ((h >>> 16) ^ h);
}
/**
* Returns the segment that should be used for key with given hash.
*
* @param hash the hash code for the key
* @return the segment
*/
private Segment<K, V> segmentFor(int hash) {
return segments[(hash >>> segmentShift) & segmentMask];
}
/* ---------------- Inner Classes -------------- */
/**
* ConcurrentHashMap list entry. Note that this is never exported
* out as a user-visible Map.Entry.
*
* Because the value field is volatile, not final, it is legal wrt
* the Java Memory Model for an unsynchronized reader to see null
* instead of initial value when read via a data race. Although a
* reordering leading to this is not likely to ever actually
* occur, the Segment.readValueUnderLock method is used as a
* snapshot in case a null (pre-initialized) value is ever seen in
* an unsynchronized access method.
*/
@SuppressWarnings({"PublicInnerClass"})
public static final class HashEntry<K, V> {
/** Key. */
private final K key;
/** Hash of the key after {@code hash()} method is applied. */
private final int hash;
/** Value. */
private volatile V val;
/** Reference to a node in queue for fast removal operations. */
@GridToStringExclude
private volatile ConcurrentLinkedDeque8.Node node;
/** Modification count of the map for duplicates exclusion. */
private volatile int modCnt;
/** Link to the next entry in a bucket */
@GridToStringExclude
private final HashEntry<K, V> next;
/**
* @param key Key.
* @param hash Key hash.
* @param next Link to next.
* @param val Value.
*/
HashEntry(K key, int hash, HashEntry<K, V> next, V val) {
this.key = key;
this.hash = hash;
this.next = next;
this.val = val;
}
/**
* @param key Key.
* @param hash Key hash.
* @param next Link to next.
* @param val Value.
* @param node Queue node.
* @param modCnt Mod count.
*/
HashEntry(K key, int hash, HashEntry<K, V> next, V val, ConcurrentLinkedDeque8.Node node, int modCnt) {
this.key = key;
this.hash = hash;
this.next = next;
this.val = val;
this.node = node;
this.modCnt = modCnt;
}
/**
* Returns key of this entry.
*
* @return Key.
*/
public K getKey() {
return key;
}
/**
* Return value of this entry.
*
* @return Value.
*/
public V getValue() {
return val;
}
/**
* Creates new array of entries.
*
* @param i Size of array.
* @param <K> Key type.
* @param <V> Value type.
* @return Empty array.
*/
@SuppressWarnings("unchecked")
static <K, V> HashEntry<K, V>[] newArray(int i) {
return new HashEntry[i];
}
/** {@inheritDoc} */
@Override public String toString() {
return S.toString(HashEntry.class, this, "key", key, "val", val);
}
}
/**
* Segments are specialized versions of hash tables. This
* subclasses from ReentrantLock opportunistically, just to
* simplify some locking and avoid separate construction.
*/
@SuppressWarnings({"TransientFieldNotInitialized"})
private final class Segment<K, V> extends ReentrantReadWriteLock {
/*
* Segments maintain a table of entry lists that are ALWAYS
* kept in a consistent state, so can be read without locking.
* Next fields of nodes are immutable (final). All list
* additions are performed at the front of each bin. This
* makes it easy to check changes, and also fast to traverse.
* When nodes would otherwise be changed, new nodes are
* created to replace them. This works well for hash tables
* since the bin lists tend to be short. (The average length
* is less than two for the default load factor threshold.)
*
* Read operations can thus proceed without locking, but rely
* on selected uses of volatiles to ensure that completed
* write operations performed by other threads are
* noticed. For most purposes, the "count" field, tracking the
* number of elements, serves as that volatile variable
* ensuring visibility. This is convenient because this field
* needs to be read in many read operations anyway:
*
* - All (unsynchronized) read operations must first read the
* "count" field, and should not look at table entries if
* it is 0.
*
* - All (synchronized) write operations should write to
* the "count" field after structurally changing any bin.
* The operations must not take any action that could even
* momentarily cause a concurrent read operation to see
* inconsistent data. This is made easier by the nature of
* the read operations in Map. For example, no operation
* can reveal that the table has grown but the threshold
* has not yet been updated, so there are no atomicity
* requirements for this with respect to reads.
*
* As a guide, all critical volatile reads and writes to the
* count field are marked in code comments.
*/
/** The number of elements in this segment's region. */
private transient volatile int cnt;
/**
* Number of updates that alter the size of the table. This is
* used during bulk-read methods to make sure they see a
* consistent snapshot: If modCounts change during a traversal
* of segments computing size or checking containsValue, then
* we might have an inconsistent view of state so (usually)
* must retry.
*/
private transient int modCnt;
/**
* The table is rehashed when its size exceeds this threshold.
* (The value of this field is always <tt>(int)(capacity *
* loadFactor)</tt>.)
*/
private transient int threshold;
/** The per-segment table. */
private transient volatile HashEntry<K, V>[] tbl;
/**
* The load factor for the hash table. Even though this value
* is same for all segments, it is replicated to avoid needing
* links to outer object.
*/
private final float loadFactor;
/** */
private final Queue<HashEntry<K, V>> segEntryQ;
/**
* @param initCap Segment initial capacity.
* @param loadFactor Segment load factor,
*/
Segment(int initCap, float loadFactor) {
this.loadFactor = loadFactor;
segEntryQ = qPlc == PER_SEGMENT_Q ? new ArrayDeque<HashEntry<K, V>>() :
qPlc == PER_SEGMENT_Q_OPTIMIZED_RMV ? new ConcurrentLinkedDeque8<HashEntry<K, V>>() : null;
setTable(HashEntry.<K, V>newArray(initCap));
}
/**
* Sets table to new HashEntry array.
* Call only while holding lock or in constructor.
*
* @param newTbl New hash table
*/
void setTable(HashEntry<K, V>[] newTbl) {
threshold = (int)(newTbl.length * loadFactor);
tbl = newTbl;
}
/**
* Returns properly casted first entry of bin for given hash.
*
* @param hash Hash of the key.
* @return Head of bin's linked list.
*/
HashEntry<K, V> getFirst(int hash) {
HashEntry<K, V>[] tab = tbl;
return tab[hash & (tab.length - 1)];
}
/**
* Reads value field of an entry under lock. Called if value
* field ever appears to be null. This is possible only if a
* compiler happens to reorder a HashEntry initialization with
* its table assignment, which is legal under memory model
* but is not known to ever occur.
*
* @param e Entry that needs to be read.
* @return Value of entry.
*/
V readValueUnderLock(HashEntry<K, V> e) {
readLock().lock();
try {
return e.val;
}
finally {
readLock().unlock();
}
}
/* Specialized implementations of map methods */
/**
* Performs lock-free read of value for given key.
*
* @param key Key to be read.
* @param hash Hash of the key
* @return Stored value
*/
V get(Object key, int hash) {
if (cnt != 0) { // read-volatile
HashEntry<K, V> e = getFirst(hash);
while (e != null) {
if (e.hash == hash && key.equals(e.key)) {
V v = e.val;
if (v != null)
return v;
v = readValueUnderLock(e);
return v; // recheck
}
e = e.next;
}
}
return null;
}
/**
* Performs lock-based read of value for given key.
* In contrast with {@link #get(Object, int)} it is guaranteed
* to be consistent with order-based iterators.
*
* @param key Key to be read.
* @param hash Hash of the key
* @return Stored value
*/
V getSafe(Object key, int hash) {
readLock().lock();
try {
HashEntry<K, V> e = getFirst(hash);
while (e != null) {
if (e.hash == hash && key.equals(e.key))
return e.val;
e = e.next;
}
return null;
}
finally {
readLock().unlock();
}
}
/**
* Performs lock-free check of key presence.
*
* @param key Key to lookup.
* @param hash Hash of the key.
* @return {@code true} if segment contains this key.
*/
boolean containsKey(Object key, int hash) {
if (cnt != 0) { // read-volatile
HashEntry<K, V> e = getFirst(hash);
while (e != null) {
if (e.hash == hash && key.equals(e.key))
return true;
e = e.next;
}
}
return false;
}
/**
* Performs lock-free check of value presence.
*
* @param val Value.
* @return {@code true} if segment contains this key.
*/
@SuppressWarnings("ForLoopReplaceableByForEach")
boolean containsValue(Object val) {
if (cnt != 0) { // read-volatile
HashEntry<K, V>[] tab = tbl;
int len = tab.length;
for (int i = 0 ; i < len; i++) {
for (HashEntry<K, V> e = tab[i]; e != null; e = e.next) {
V v = e.val;
if (v == null) // recheck
v = readValueUnderLock(e);
if (val.equals(v))
return true;
}
}
}
return false;
}
/**
* Performs value replacement for a given key with old value check.
*
* @param key Key to replace.
* @param hash Hash of the key.
* @param oldVal Old value.
* @param newVal New value
* @return {@code true} If value was replaced.
*/
@SuppressWarnings({"unchecked"})
boolean replace(K key, int hash, V oldVal, V newVal) {
writeLock().lock();
boolean replaced = false;
try {
HashEntry<K, V> e = getFirst(hash);
while (e != null && (e.hash != hash || !key.equals(e.key)))
e = e.next;
if (e != null && oldVal.equals(e.val)) {
replaced = true;
e.val = newVal;
}
}
finally {
writeLock().unlock();
}
return replaced;
}
/**
* Performs value replacement for a given key with old value check.
*
* @param key Key to replace.
* @param hash Hash of the key.
* @param oldVal Old value.
* @param newVal New value
* @return {@code oldVal}, if value was replaced, non-null object if map
* contained some other value and {@code null} if there were no such key.
*/
@SuppressWarnings({"unchecked"})
V replacex(K key, int hash, V oldVal, V newVal) {
writeLock().lock();
V replaced = null;
try {
HashEntry<K, V> e = getFirst(hash);
while (e != null && (e.hash != hash || !key.equals(e.key)))
e = e.next;
if (e != null) {
if (oldVal.equals(e.val)) {
replaced = oldVal;
e.val = newVal;
}
else
replaced = e.val;
}
}
finally {
writeLock().unlock();
}
return replaced;
}
@SuppressWarnings({"unchecked"})
V replace(K key, int hash, V newVal) {
writeLock().lock();
V oldVal = null;
try {
HashEntry<K, V> e = getFirst(hash);
while (e != null && (e.hash != hash || !key.equals(e.key)))
e = e.next;
if (e != null) {
oldVal = e.val;
e.val = newVal;
}
}
finally {
writeLock().unlock();
}
return oldVal;
}
@SuppressWarnings({"unchecked"})
V put(K key, int hash, V val, boolean onlyIfAbsent) {
writeLock().lock();
V oldVal;
boolean added = false;
try {
int c = cnt;
if (c++ > threshold) // ensure capacity
rehash();
HashEntry<K, V>[] tab = tbl;
int idx = hash & (tab.length - 1);
HashEntry<K, V> first = tab[idx];
HashEntry<K, V> e = first;
while (e != null && (e.hash != hash || !key.equals(e.key)))
e = e.next;
boolean modified = false;
if (e != null) {
oldVal = e.val;
if (!onlyIfAbsent) {
e.val = val;
ConcurrentLinkedDeque8.Node node = e.node;
if (node != null) {
HashEntry<K, V> qEntry = (HashEntry<K, V>)node.item();
if (qEntry != null && qEntry != e)
qEntry.val = val;
}
modified = true;
}
}
else {
oldVal = null;
++modCnt;
size.increment();
e = tab[idx] = new HashEntry<>(key, hash, first, val);
ConcurrentLinkedHashMap.this.modCnt.increment();
e.modCnt = ConcurrentLinkedHashMap.this.modCnt.intValue();
cnt = c; // write-volatile
added = true;
}
assert !(added && modified);
if (added) {
switch (qPlc) {
case PER_SEGMENT_Q_OPTIMIZED_RMV:
recordInsert(e, (ConcurrentLinkedDeque8)segEntryQ);
if (maxCap > 0)
checkRemoveEldestEntrySegment(c);
break;
case PER_SEGMENT_Q:
segEntryQ.add(e);
if (maxCap > 0)
checkRemoveEldestEntrySegment(c);
break;
default:
assert qPlc == SINGLE_Q;
recordInsert(e, entryQ);
}
}
}
finally {
writeLock().unlock();
}
if (qPlc == SINGLE_Q && added && maxCap > 0)
checkRemoveEldestEntry();
return oldVal;
}
/**
* @param cnt Segment entries count.
*/
private void checkRemoveEldestEntrySegment(int cnt) {
assert maxCap > 0;
if (cnt - ((maxCap / segments.length) + 1) > 0) {
HashEntry<K, V> e0 = segEntryQ.poll();
assert e0 != null;
removeLocked(
e0.key,
e0.hash,
null /*no need to compare*/,
false);
}
}
/**
* This method is called under the segment lock.
*/
@SuppressWarnings({"ForLoopReplaceableByForEach", "unchecked"})
void rehash() {
HashEntry<K, V>[] oldTbl = tbl;
int oldCap = oldTbl.length;
if (oldCap >= MAX_CAP_LIMIT)
return;
/*
* Reclassify nodes in each list to new Map. Because we are
* using power-of-two expansion, the elements from each bin
* must either stay at same index, or move with a power of two
* offset. We eliminate unnecessary node creation by catching
* cases where old nodes can be reused because their next
* fields won't change. Statistically, at the default
* threshold, only about one-sixth of them need cloning when
* a table doubles. The nodes they replace will be garbage
* collectable as soon as they are no longer referenced by any
* reader thread that may be in the midst of traversing table
* right now.
*/
int c = cnt;
HashEntry<K, V>[] newTbl = HashEntry.newArray(oldCap << 1);
threshold = (int)(newTbl.length * loadFactor);
int sizeMask = newTbl.length - 1;
for (int i = 0; i < oldCap; i++) {
// We need to guarantee that any existing reads of old Map can
// proceed. So we cannot yet null out each bin.
HashEntry<K, V> e = oldTbl[i];
if (e != null) {
HashEntry<K, V> next = e.next;
int idx = e.hash & sizeMask;
// Single node on list
if (next == null)
newTbl[idx] = e;
else {
// Reuse trailing consecutive sequence at same slot
HashEntry<K, V> lastRun = e;
int lastIdx = idx;
for (HashEntry<K, V> last = next; last != null; last = last.next) {
int k = last.hash & sizeMask;
if (k != lastIdx) {
lastIdx = k;
lastRun = last;
}
}
newTbl[lastIdx] = lastRun;
// Clone all remaining nodes
for (HashEntry<K, V> p = e; p != lastRun; p = p.next) {
int k = p.hash & sizeMask;
HashEntry<K, V> n = newTbl[k];
HashEntry<K, V> e0 = new HashEntry<>(p.key, p.hash, n, p.val, p.node, p.modCnt);
newTbl[k] = e0;
}
}
}
}
cnt = c;
tbl = newTbl;
}
/**
* Remove; match on key only if value null, else match both.
*
* @param key Key to be removed.
* @param hash Hash of the key.
* @param val Value to match.
* @param cleanupQ {@code True} if need to cleanup queue.
* @return Old value, if entry existed, {@code null} otherwise.
*/
V remove(Object key, int hash, Object val, boolean cleanupQ) {
writeLock().lock();
try {
return removeLocked(key, hash, val, cleanupQ);
}
finally {
writeLock().unlock();
}
}
/**
* Locked version of remove. Match on key only if value null, else match both.
*
* @param key Key to be removed.
* @param hash Hash of the key.
* @param val Value to match.
* @param cleanupQ {@code True} if need to cleanup queue.
* @return Old value, if entry existed, {@code null} otherwise.
*/
@SuppressWarnings({"unchecked"})
V removeLocked(Object key, int hash, Object val, boolean cleanupQ) {
int c = cnt - 1;
HashEntry<K, V>[] tab = tbl;
int idx = hash & (tab.length - 1);
HashEntry<K, V> first = tab[idx];
HashEntry<K, V> e = first;
while (e != null && (e.hash != hash || !key.equals(e.key)))
e = e.next;
V oldVal = null;
if (e != null) {
V v = e.val;
if (val == null || val.equals(v)) {
oldVal = v;
// All entries following removed node can stay
// in list, but all preceding ones need to be
// cloned.
++modCnt;
ConcurrentLinkedHashMap.this.modCnt.increment();
HashEntry<K, V> newFirst = e.next;
for (HashEntry<K, V> p = first; p != e; p = p.next)
newFirst = new HashEntry<>(p.key, p.hash, newFirst, p.val, p.node, p.modCnt);
tab[idx] = newFirst;
cnt = c; // write-volatile
size.decrement();
}
}
if (oldVal != null && cleanupQ) {
switch (qPlc) {
case PER_SEGMENT_Q_OPTIMIZED_RMV:
((ConcurrentLinkedDeque8)segEntryQ).unlinkx(e.node);
e.node = null;
break;
case PER_SEGMENT_Q:
// Linear time method call.
segEntryQ.remove(e);
break;
default:
assert qPlc == SINGLE_Q;
entryQ.unlinkx(e.node);
e.node = null;
}
}
return oldVal;
}
/**
*
*/
void clear() {
if (cnt != 0) {
writeLock().lock();
try {
HashEntry<K, V>[] tab = tbl;
for (int i = 0; i < tab.length ; i++)
tab[i] = null;
++modCnt;
cnt = 0; // write-volatile
}
finally {
writeLock().unlock();
}
}
}
}
/* ---------------- Public operations -------------- */
/**
* Creates a new, empty map with the specified initial
* capacity, load factor, concurrency level and max capacity.
*
* @param initCap the initial capacity. The implementation
* performs internal sizing to accommodate this many elements.
* @param loadFactor the load factor threshold, used to control resizing.
* Resizing may be performed when the average number of elements per
* bin exceeds this threshold.
* @param concurLvl the estimated number of concurrently
* updating threads. The implementation performs internal sizing
* to try to accommodate this many threads.
* @param maxCap Max capacity ({@code 0} for unbounded).
* @param qPlc Queue policy.
* @throws IllegalArgumentException if the initial capacity is
* negative or the load factor or concurLvl are
* non-positive.
*/
@SuppressWarnings({"unchecked"})
public ConcurrentLinkedHashMap(int initCap, float loadFactor, int concurLvl, int maxCap, QueuePolicy qPlc) {
if (!(loadFactor > 0) || initCap < 0 || concurLvl <= 0)
throw new IllegalArgumentException();
if (concurLvl > MAX_SEGS)
concurLvl = MAX_SEGS;
this.maxCap = maxCap;
this.qPlc = qPlc;
entryQ = qPlc == SINGLE_Q ? new ConcurrentLinkedDeque8<HashEntry<K, V>>() : null;
// Find power-of-two sizes best matching arguments
int sshift = 0;
int ssize = 1;
while (ssize < concurLvl) {
++sshift;
ssize <<= 1;
}
segmentShift = 32 - sshift;
segmentMask = ssize - 1;
segments = new Segment[ssize];
if (initCap > MAX_CAP_LIMIT)
initCap = MAX_CAP_LIMIT;
int c = initCap / ssize;
if (c * ssize < initCap)
++c;
int cap = 1;
while (cap < c)
cap <<= 1;
for (int i = 0; i < segments.length; ++i)
segments[i] = new Segment<>(cap, loadFactor);
}
/**
* Creates a new, empty map with the specified initial
* capacity, load factor, concurrency level and max capacity.
*
* @param initCap the initial capacity. The implementation
* performs internal sizing to accommodate this many elements.
* @param loadFactor the load factor threshold, used to control resizing.
* Resizing may be performed when the average number of elements per
* bin exceeds this threshold.
* @param concurLvl the estimated number of concurrently
* updating threads. The implementation performs internal sizing
* to try to accommodate this many threads.
* @param maxCap Max capacity ({@code 0} for unbounded).
* @throws IllegalArgumentException if the initial capacity is
* negative or the load factor or concurLvl are
* non-positive.
*/
public ConcurrentLinkedHashMap(int initCap, float loadFactor, int concurLvl, int maxCap) {
this(initCap, loadFactor, concurLvl, maxCap, SINGLE_Q);
}
/**
* Creates a new, empty map with the specified initial
* capacity, load factor and concurrency level.
*
* @param initCap the initial capacity. The implementation
* performs internal sizing to accommodate this many elements.
* @param loadFactor the load factor threshold, used to control resizing.
* Resizing may be performed when the average number of elements per
* bin exceeds this threshold.
* @param concurLvl the estimated number of concurrently
* updating threads. The implementation performs internal sizing
* to try to accommodate this many threads.
* @throws IllegalArgumentException if the initial capacity is
* negative or the load factor or concurLvl are
* non-positive.
*/
@SuppressWarnings({"unchecked"})
public ConcurrentLinkedHashMap(int initCap, float loadFactor, int concurLvl) {
this(initCap, loadFactor, concurLvl, 0);
}
/**
* Creates a new, empty map with the specified initial capacity
* and load factor and with the default concurrencyLevel (16).
*
* @param initCap The implementation performs internal
* sizing to accommodate this many elements.
* @param loadFactor the load factor threshold, used to control resizing.
* Resizing may be performed when the average number of elements per
* bin exceeds this threshold.
* @throws IllegalArgumentException if the initial capacity of
* elements is negative or the load factor is non-positive
*
* @since 1.6
*/
public ConcurrentLinkedHashMap(int initCap, float loadFactor) {
this(initCap, loadFactor, DFLT_CONCUR_LVL);
}
/**
* Creates a new, empty map with the specified initial capacity,
* and with default load factor (0.75) and concurrencyLevel (16).
*
* @param initCap the initial capacity. The implementation
* performs internal sizing to accommodate this many elements.
* @throws IllegalArgumentException if the initial capacity of
* elements is negative.
*/
public ConcurrentLinkedHashMap(int initCap) {
this(initCap, DFLT_LOAD_FACTOR, DFLT_CONCUR_LVL);
}
/**
* Creates a new, empty map with a default initial capacity (16),
* load factor (0.75) and concurrencyLevel (16).
*/
public ConcurrentLinkedHashMap() {
this(DFLT_INIT_CAP, DFLT_LOAD_FACTOR, DFLT_CONCUR_LVL);
}
/**
* Creates a new map with the same mappings as the given map.
* The map is created with a capacity of 1.5 times the number
* of mappings in the given map or 16 (whichever is greater),
* and a default load factor (0.75) and concurrencyLevel (16).
*
* @param m the map
*/
public ConcurrentLinkedHashMap(Map<? extends K, ? extends V> m) {
this(Math.max((int) (m.size() / DFLT_LOAD_FACTOR) + 1, DFLT_INIT_CAP),
DFLT_LOAD_FACTOR, DFLT_CONCUR_LVL);
putAll(m);
}
/**
* Returns <tt>true</tt> if this map contains no key-value mappings.
*
* @return <tt>true</tt> if this map contains no key-value mappings.
*/
@Override public boolean isEmpty() {
Segment<K, V>[] segments = this.segments;
/*
* We keep track of per-segment modCounts to avoid ABA
* problems in which an element in one segment was added and
* in another removed during traversal, in which case the
* table was never actually empty at any point. Note the
* similar use of modCounts in the size() and containsValue()
* methods, which are the only other methods also susceptible
* to ABA problems.
*/
int[] mc = new int[segments.length];
int mcsum = 0;
for (int i = 0; i < segments.length; ++i) {
if (segments[i].cnt != 0)
return false;
else
mcsum += mc[i] = segments[i].modCnt;
}
// If mcsum happens to be zero, then we know we got a snapshot
// before any modifications at all were made. This is
// probably common enough to bother tracking.
if (mcsum != 0) {
for (int i = 0; i < segments.length; ++i) {
if (segments[i].cnt != 0 ||
mc[i] != segments[i].modCnt)
return false;
}
}
return true;
}
/**
* 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
*/
@SuppressWarnings({"LockAcquiredButNotSafelyReleased"})
@Override public int size() {
Segment<K, V>[] segments = this.segments;
long sum = 0;
long check = 0;
int[] mc = new int[segments.length];
// Try a few times to get accurate count. On failure due to
// continuous async changes in table, resort to locking.
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
check = 0;
sum = 0;
int mcsum = 0;
for (int i = 0; i < segments.length; ++i) {
sum += segments[i].cnt;
mcsum += mc[i] = segments[i].modCnt;
}
if (mcsum != 0) {
for (int i = 0; i < segments.length; ++i) {
check += segments[i].cnt;
if (mc[i] != segments[i].modCnt) {
check = -1; // force retry
break;
}
}
}
if (check == sum)
break;
}
if (check != sum) { // Resort to locking all segments
sum = 0;
for (Segment<K, V> segment : segments)
segment.readLock().lock();
for (Segment<K, V> segment : segments)
sum += segment.cnt;
for (Segment<K, V> segment : segments)
segment.readLock().unlock();
}
return sum > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int)sum;
}
/**
* @return The number of key-value mappings in this map (constant-time).
*/
public int sizex() {
int i = size.intValue();
return i > 0 ? i : 0;
}
/**
* @return <tt>true</tt> if this map contains no key-value mappings
*/
public boolean isEmptyx() {
return sizex() == 0;
}
/**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
*
* <p>More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code key.equals(k)},
* then this method returns {@code v}; otherwise it returns
* {@code null}. (There can be at most one such mapping.)
*
* @throws NullPointerException if the specified key is null
*/
@Override public V get(Object key) {
int hash = hash(key.hashCode());
return segmentFor(hash).get(key, hash);
}
/**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
*
* <p>More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code key.equals(k)},
* then this method returns {@code v}; otherwise it returns
* {@code null}. (There can be at most one such mapping.)
*
* In contrast with {@link #get(Object)} this method acquires
* read lock on segment where the key is mapped.
*
* @throws NullPointerException if the specified key is null
*/
public V getSafe(Object key) {
int hash = hash(key.hashCode());
return segmentFor(hash).getSafe(key, hash);
}
/**
* Tests if the specified object is a key in this table.
*
* @param key possible key
* @return <tt>true</tt> if and only if the specified object
* is a key in this table, as determined by the
* <tt>equals</tt> method; <tt>false</tt> otherwise.
* @throws NullPointerException if the specified key is null
*/
@Override public boolean containsKey(Object key) {
int hash = hash(key.hashCode());
return segmentFor(hash).containsKey(key, hash);
}
/**
* Returns <tt>true</tt> if this map maps one or more keys to the
* specified value. Note: This method requires a full internal
* traversal of the hash table, and so is much slower than
* method <tt>containsKey</tt>.
*
* @param val value whose presence in this map is to be tested
* @return <tt>true</tt> if this map maps one or more keys to the
* specified value
* @throws NullPointerException if the specified value is null
*/
@SuppressWarnings({"LockAcquiredButNotSafelyReleased"})
@Override public boolean containsValue(Object val) {
if (val == null)
throw new NullPointerException();
// See explanation of modCount use above
Segment<K, V>[] segments = this.segments;
int[] mc = new int[segments.length];
// Try a few times without locking
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
int mcsum = 0;
for (int i = 0; i < segments.length; ++i) {
mcsum += mc[i] = segments[i].modCnt;
if (segments[i].containsValue(val))
return true;
}
boolean cleanSweep = true;
if (mcsum != 0) {
for (int i = 0; i < segments.length; ++i) {
if (mc[i] != segments[i].modCnt) {
cleanSweep = false;
break;
}
}
}
if (cleanSweep)
return false;
}
// Resort to locking all segments
for (Segment<K, V> segment : segments)
segment.readLock().lock();
boolean found = false;
try {
for (Segment<K, V> segment : segments) {
if (segment.containsValue(val)) {
found = true;
break;
}
}
} finally {
for (Segment<K, V> segment : segments)
segment.readLock().unlock();
}
return found;
}
/**
* Legacy method testing if some key maps into the specified value
* in this table. This method is identical in functionality to
* {@link #containsValue}, and exists solely to ensure
* full compatibility with class {@link java.util.Hashtable},
* which supported this method prior to introduction of the
* Java Collections framework.
* @param val a value to search for
* @return <tt>true</tt> if and only if some key maps to the
* <tt>value</tt> argument in this table as
* determined by the <tt>equals</tt> method;
* <tt>false</tt> otherwise
* @throws NullPointerException if the specified value is null
*/
public boolean contains(Object val) {
return containsValue(val);
}
/**
* Maps the specified key to the specified value in this table.
* Neither the key nor the value can be null.
*
* <p> The value can be retrieved by calling the <tt>get</tt> method
* with a key that is equal to the original key.
*
* @param key key with which the specified value is to be associated
* @param val 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>
* @throws NullPointerException if the specified key or value is null
*/
@Override public V put(K key, V val) {
if (val == null)
throw new NullPointerException();
int hash = hash(key.hashCode());
return segmentFor(hash).put(key, hash, val, false);
}
/**
* {@inheritDoc}
*
* @return the previous value associated with the specified key,
* or <tt>null</tt> if there was no mapping for the key
* @throws NullPointerException if the specified key or value is null
*/
@Override public V putIfAbsent(K key, V val) {
if (val == null)
throw new NullPointerException();
int hash = hash(key.hashCode());
return segmentFor(hash).put(key, hash, val, true);
}
/**
* Copies all of the mappings from the specified map to this one.
* These mappings replace any mappings that this map had for any of the
* keys currently in the specified map.
*
* @param m mappings to be stored in this map
*/
@Override public void putAll(Map<? extends K, ? extends V> m) {
for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
put(e.getKey(), e.getValue());
}
/**
* Removes the key (and its corresponding value) from this map.
* This method does nothing if the key is not in the map.
*
* @param key the key that needs to be removed
* @return the previous value associated with <tt>key</tt>, or
* <tt>null</tt> if there was no mapping for <tt>key</tt>
* @throws NullPointerException if the specified key is null
*/
@Override public V remove(Object key) {
int hash = hash(key.hashCode());
return segmentFor(hash).remove(key, hash, null, true);
}
/**
* {@inheritDoc}
*
* @throws NullPointerException if the specified key is null
*/
@SuppressWarnings("NullableProblems")
@Override public boolean remove(Object key, Object val) {
int hash = hash(key.hashCode());
return val != null && segmentFor(hash).remove(key, hash, val, true) != null;
}
/**
* {@inheritDoc}
*
* @throws NullPointerException if any of the arguments are null
*/
@SuppressWarnings("NullableProblems")
@Override public boolean replace(K key, V oldVal, V newVal) {
if (oldVal == null || newVal == null)
throw new NullPointerException();
int hash = hash(key.hashCode());
return segmentFor(hash).replace(key, hash, oldVal, newVal);
}
/**
* Replaces the entry for a key only if currently mapped to a given value.
* This is equivalent to
* <pre>
* if (map.containsKey(key)) {
* if (map.get(key).equals(oldValue)) {
* map.put(key, newValue);
* return oldValue;
* } else
* return map.get(key);
* } else return null;</pre>
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param oldVal value expected to be associated with the specified key
* @param newVal value to be associated with the specified key
* @return {@code oldVal}, if value was replaced, non-null previous value if map
* contained some other value and {@code null} if there were no such key.
*/
public V replacex(K key, V oldVal, V newVal) {
if (oldVal == null || newVal == null)
throw new NullPointerException();
int hash = hash(key.hashCode());
return segmentFor(hash).replacex(key, hash, oldVal, newVal);
}
/**
* {@inheritDoc}
*
* @return the previous value associated with the specified key,
* or <tt>null</tt> if there was no mapping for the key
* @throws NullPointerException if the specified key or value is null
*/
@SuppressWarnings("NullableProblems")
@Override public V replace(K key, V val) {
if (val == null)
throw new NullPointerException();
int hash = hash(key.hashCode());
return segmentFor(hash).replace(key, hash, val);
}
/**
* Removes all of the mappings from this map.
*/
@Override public void clear() {
for (Segment<K, V> segment : segments)
segment.clear();
}
/**
* Returns a {@link Set} view of the keys contained in this map.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. The set supports element
* removal, which removes the corresponding mapping from this map,
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
* operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
* that will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*/
@Override public Set<K> keySet() {
Set<K> ks = keySet;
return (ks != null) ? ks : (keySet = new KeySet());
}
/**
* Returns a {@link Set} view of the keys contained in this map
* in descending order.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. The set supports element
* removal, which removes the corresponding mapping from this map,
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
* operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
* that will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*/
public Set<K> descendingKeySet() {
Set<K> ks = descKeySet;
return (ks != null) ? ks : (descKeySet = new KeySetDescending());
}
/**
* Returns a {@link Collection} view of the values contained in this map.
* The collection is backed by the map, so changes to the map are
* reflected in the collection, and vice-versa. The collection
* supports element removal, which removes the corresponding
* mapping from this map, via the <tt>Iterator.remove</tt>,
* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
* <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not
* support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
* that will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*/
@Override public Collection<V> values() {
Collection<V> vs = vals;
return (vs != null) ? vs : (vals = new Values());
}
/**
* Returns a {@link Collection} view of the values contained in this map
* in descending order.
* The collection is backed by the map, so changes to the map are
* reflected in the collection, and vice-versa. The collection
* supports element removal, which removes the corresponding
* mapping from this map, via the <tt>Iterator.remove</tt>,
* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
* <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not
* support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
* that will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*/
public Collection<V> descendingValues() {
Collection<V> vs = descVals;
return (vs != null) ? vs : (descVals = new ValuesDescending());
}
/**
* Returns a {@link Set} view of the mappings contained in this map.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. The set supports element
* removal, which removes the corresponding mapping from the map,
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
* operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
* that will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*/
@Override public Set<Map.Entry<K, V>> entrySet() {
Set<Map.Entry<K, V>> es = entrySet;
return (es != null) ? es : (entrySet = new EntrySet());
}
/**
* Returns a {@link Set} view of the mappings contained in this map
* in descending order.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. The set supports element
* removal, which removes the corresponding mapping from the map,
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
* operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
* that will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*/
public Set<Map.Entry<K, V>> descendingEntrySet() {
Set<Map.Entry<K, V>> es = descEntrySet;
return (es != null) ? es : (descEntrySet = new EntrySetDescending());
}
/**
* Returns an enumeration of the keys in this table.
*
* @return an enumeration of the keys in this table.
* @see #keySet()
*/
public Enumeration<K> keys() {
return new KeyIterator(true);
}
/**
* Returns an enumeration of the keys in this table in descending order.
*
* @return an enumeration of the keys in this table in descending order.
* @see #keySet()
*/
public Enumeration<K> descendingKeys() {
return new KeyIterator(false);
}
/**
* Returns an enumeration of the values in this table.
*
* @return an enumeration of the values in this table.
* @see #values()
*/
public Enumeration<V> elements() {
return new ValueIterator(true);
}
/**
* Returns an enumeration of the values in this table in descending order.
*
* @return an enumeration of the values in this table in descending order.
* @see #values()
*/
public Enumeration<V> descendingElements() {
return new ValueIterator(false);
}
/**
* This method is called by hash map whenever a new entry is inserted into map.
* <p>
* This method is called outside the segment-protection lock and may be called concurrently.
*
* @param e The new inserted entry.
*/
@SuppressWarnings({"unchecked"})
private void recordInsert(HashEntry e, ConcurrentLinkedDeque8 q) {
e.node = q.addx(e);
}
/**
* Concurrently removes eldest entry from the map.
*/
private void checkRemoveEldestEntry() {
assert maxCap > 0;
assert qPlc == SINGLE_Q;
int sizex = sizex();
for (int i = maxCap; i < sizex; i++) {
HashEntry<K, V> e = entryQ.poll();
if (e != null)
segmentFor(e.hash).remove(e.key, e.hash, e.val, false);
else
return;
if (sizex() <= maxCap)
return;
}
}
/**
* This method is intended for test purposes only.
*
* @return Queue.
*/
public ConcurrentLinkedDeque8<HashEntry<K, V>> queue() {
return entryQ;
}
/**
* @return Queue policy.
*/
public QueuePolicy policy() {
return qPlc;
}
/**
* Class implementing iteration over map entries.
*/
private abstract class HashIterator {
/** Underlying collection iterator. */
private Iterator<HashEntry<K, V>> delegate;
/** Last returned entry, used in {@link #remove()} method. */
private HashEntry<K, V> lastReturned;
/** Next entry to return */
private HashEntry<K, V> nextEntry;
/** The map modification count at the creation time. */
private int modCnt;
/**
* @param asc {@code True} for ascending iterator.
*/
HashIterator(boolean asc) {
modCnt = ConcurrentLinkedHashMap.this.modCnt.intValue();
// Init delegate.
switch (qPlc) {
case SINGLE_Q:
delegate = asc ? entryQ.iterator() : entryQ.descendingIterator();
break;
default:
assert qPlc == PER_SEGMENT_Q || qPlc == PER_SEGMENT_Q_OPTIMIZED_RMV : qPlc;
delegate = new HashIteratorDelegate();
}
advance();
}
/**
* @return {@code true} If iterator has elements to iterate.
*/
public boolean hasMoreElements() {
return hasNext();
}
/**
* @return {@code true} If iterator has elements to iterate.
*/
public boolean hasNext() {
return nextEntry != null;
}
/**
* @return Next entry.
*/
HashEntry<K, V> nextEntry() {
if (nextEntry == null)
throw new NoSuchElementException();
lastReturned = nextEntry;
advance();
return lastReturned;
}
/**
* Removes entry returned by {@link #nextEntry()}.
*/
public void remove() {
if (lastReturned == null)
throw new IllegalStateException();
ConcurrentLinkedHashMap.this.remove(lastReturned.key);
lastReturned = null;
}
/**
* Moves iterator to the next position.
*/
private void advance() {
nextEntry = null;
while (delegate.hasNext()) {
HashEntry<K, V> n = delegate.next();
if (n.modCnt <= modCnt) {
nextEntry = n;
break;
}
}
}
}
/**
*
*/
private class HashIteratorDelegate implements Iterator<HashEntry<K, V>> {
/** */
private HashEntry<K, V>[] curTbl;
/** */
private int nextSegIdx;
/** */
private int nextTblIdx;
/** */
private HashEntry<K, V> next;
/** */
private HashEntry<K, V> next0;
/** */
private HashEntry<K, V> cur;
/**
*
*/
public HashIteratorDelegate() {
nextSegIdx = segments.length - 1;
nextTblIdx = -1;
advance();
}
/**
*
*/
private void advance() {
if (next0 != null && advanceInBucket(next0, true))
return;
while (nextTblIdx >= 0) {
HashEntry<K, V> bucket = curTbl[nextTblIdx--];
if (bucket != null && advanceInBucket(bucket, false))
return;
}
while (nextSegIdx >= 0) {
int nextSegIdx0 = nextSegIdx--;
Segment seg = segments[nextSegIdx0];
curTbl = seg.tbl;
for (int j = curTbl.length - 1; j >= 0; --j) {
HashEntry<K, V> bucket = curTbl[j];
if (bucket != null && advanceInBucket(bucket, false)) {
nextTblIdx = j - 1;
return;
}
}
}
}
/**
* @param e Current next.
* @return {@code True} if advance succeeded.
*/
@SuppressWarnings( {"unchecked"})
private boolean advanceInBucket(@Nullable HashEntry<K, V> e, boolean skipFirst) {
if (e == null)
return false;
next0 = e;
do {
if (!skipFirst) {
next = next0;
return true;
}
else
skipFirst = false;
}
while ((next0 = next0.next) != null);
assert next0 == null;
next = null;
return false;
}
/** {@inheritDoc} */
@Override public boolean hasNext() {
return next != null;
}
/** {@inheritDoc} */
@Override public HashEntry<K, V> next() {
HashEntry<K, V> e = next;
if (e == null)
throw new NoSuchElementException();
advance();
return e;
}
/** {@inheritDoc} */
@Override public void remove() {
if (cur == null)
throw new IllegalStateException();
HashEntry<K, V> e = cur;
cur = null;
ConcurrentLinkedHashMap.this.remove(e.key, e.val);
}
}
/**
* Key iterator implementation.
*/
private final class KeyIterator extends HashIterator implements Iterator<K>, Enumeration<K> {
/**
* @param asc {@code True} for ascending iterator.
*/
private KeyIterator(boolean asc) {
super(asc);
}
/** {@inheritDoc} */
@Override public K next() {
return nextEntry().key;
}
/** {@inheritDoc} */
@Override public K nextElement() {
return nextEntry().key;
}
}
/**
* Value iterator implementation.
*/
private final class ValueIterator extends HashIterator implements Iterator<V>, Enumeration<V> {
/**
* @param asc {@code True} for ascending iterator.
*/
private ValueIterator(boolean asc) {
super(asc);
}
/** {@inheritDoc} */
@Override public V next() {
return nextEntry().val;
}
/** {@inheritDoc} */
@Override public V nextElement() {
return nextEntry().val;
}
}
/**
* Custom Entry class used by EntryIterator.next(), that relays
* setValue changes to the underlying map.
*/
private final class WriteThroughEntry extends AbstractMap.SimpleEntry<K, V> {
/**
* @param k Key
* @param v Value
*/
WriteThroughEntry(K k, V v) {
super(k,v);
}
/**
* Set our entry's value and write through to the map. The
* value to return is somewhat arbitrary here. Since a
* WriteThroughEntry does not necessarily track asynchronous
* changes, the most recent "previous" value could be
* different from what we return (or could even have been
* removed in which case the put will re-establish). We do not
* and cannot guarantee more.
*/
@Override public V setValue(V val) {
if (val == null)
throw new NullPointerException();
V v = super.setValue(val);
put(getKey(), val);
return v;
}
}
/**
* Entry iterator implementation.
*/
private final class EntryIterator extends HashIterator implements Iterator<Entry<K, V>> {
/**
* @param asc {@code True} for ascending iterator.
*/
private EntryIterator(boolean asc) {
super(asc);
}
/** {@inheritDoc} */
@Override public Map.Entry<K, V> next() {
HashEntry<K, V> e = nextEntry();
return new WriteThroughEntry(e.key, e.val);
}
}
/**
* Key set of the map.
*/
private abstract class AbstractKeySet extends AbstractSet<K> {
/** {@inheritDoc} */
@Override public int size() {
return ConcurrentLinkedHashMap.this.size();
}
/** {@inheritDoc} */
@Override public boolean contains(Object o) {
return containsKey(o);
}
/** {@inheritDoc} */
@Override public boolean remove(Object o) {
return ConcurrentLinkedHashMap.this.remove(o) != null;
}
/** {@inheritDoc} */
@Override public void clear() {
ConcurrentLinkedHashMap.this.clear();
}
}
/**
* Key set of the map.
*/
private final class KeySet extends AbstractKeySet {
/** {@inheritDoc} */
@Override public Iterator<K> iterator() {
return new KeyIterator(true);
}
}
/**
* Key set of the map.
*/
private final class KeySetDescending extends AbstractKeySet {
/** {@inheritDoc} */
@Override public Iterator<K> iterator() {
return new KeyIterator(false);
}
}
/**
* Values collection of the map.
*/
private abstract class AbstractValues extends AbstractCollection<V> {
/** {@inheritDoc} */
@Override public int size() {
return ConcurrentLinkedHashMap.this.size();
}
/** {@inheritDoc} */
@Override public boolean contains(Object o) {
return containsValue(o);
}
/** {@inheritDoc} */
@Override public void clear() {
ConcurrentLinkedHashMap.this.clear();
}
}
/**
* Values collection of the map.
*/
private final class Values extends AbstractValues {
/** {@inheritDoc} */
@Override public Iterator<V> iterator() {
return new ValueIterator(true);
}
}
/**
* Values collection of the map.
*/
private final class ValuesDescending extends AbstractValues {
/** {@inheritDoc} */
@Override public Iterator<V> iterator() {
return new ValueIterator(false);
}
}
/**
* Entry set implementation.
*/
private abstract class AbstractEntrySet extends AbstractSet<Map.Entry<K, V>> {
/** {@inheritDoc} */
@Override public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
V v = get(e.getKey());
return v != null && v.equals(e.getValue());
}
/** {@inheritDoc} */
@Override public boolean remove(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
return ConcurrentLinkedHashMap.this.remove(e.getKey(), e.getValue());
}
/** {@inheritDoc} */
@Override public int size() {
return ConcurrentLinkedHashMap.this.size();
}
/** {@inheritDoc} */
@Override public void clear() {
ConcurrentLinkedHashMap.this.clear();
}
}
/**
* Entry set implementation.
*/
private final class EntrySet extends AbstractEntrySet {
/** {@inheritDoc} */
@Override public Iterator<Map.Entry<K, V>> iterator() {
return new EntryIterator(true);
}
}
/**
* Entry set implementation.
*/
private final class EntrySetDescending extends AbstractEntrySet {
/** {@inheritDoc} */
@Override public Iterator<Map.Entry<K, V>> iterator() {
return new EntryIterator(false);
}
}
/**
* Defines queue policy for this hash map.
*/
@SuppressWarnings("PublicInnerClass")
public enum QueuePolicy {
/**
* Default policy. Single queue is maintained. Iteration order is preserved.
*/
SINGLE_Q,
/**
* Instance of {@code ArrayDeque} is created for each segment. This gives
* the fastest "natural" evicts for bounded maps.
* <p>
* NOTE: Remove operations on map are slower than with other policies.
* <p>
* NOTE: Iteration order is not preserved, i.e. iteration goes as if it was ordinary hash map.
*/
PER_SEGMENT_Q,
/**
* Instance of {@code GridConcurrentLinkedDequeue} is created for each segment. This gives
* faster "natural" evicts for bounded queues and better remove operation times.
* <p>
* NOTE: Iteration order is not preserved, i.e. iteration goes as if it was ordinary hash map.
*/
PER_SEGMENT_Q_OPTIMIZED_RMV
}
}