/*
* Copyright 2012 Red Hat, Inc. and/or its affiliates.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301 USA
*/
package org.infinispan.util.concurrent.jdk8backported;
/*
* 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/
*/
import java.util.Arrays;
import java.util.Map;
import java.util.Set;
import java.util.Collection;
import java.util.Hashtable;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Enumeration;
import java.util.ConcurrentModificationException;
import java.util.NoSuchElementException;
import java.util.concurrent.ConcurrentMap;
import java.io.Serializable;
/**
* A hash table supporting full concurrency of retrievals and
* high 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
* {@code Hashtable}. 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 {@code Hashtable} in programs that rely on its
* thread safety but not on its synchronization details.
*
* <p> Retrieval operations (including {@code get}) generally do not
* block, so may overlap with update operations (including {@code put}
* and {@code remove}). Retrievals reflect the results of the most
* recently <em>completed</em> update operations holding upon their
* onset. For aggregate operations such as {@code putAll} and {@code
* clear}, 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. Bear in mind that the results of aggregate status methods
* including {@code size}, {@code isEmpty}, and {@code containsValue}
* are typically useful only when a map is not undergoing concurrent
* updates in other threads. Otherwise the results of these methods
* reflect transient states that may be adequate for monitoring
* or estimation purposes, but not for program control.
*
* <p> The table is dynamically expanded when there are too many
* collisions (i.e., keys that have distinct hash codes but fall into
* the same slot modulo the table size), with the expected average
* effect of maintaining roughly two bins per mapping (corresponding
* to a 0.75 load factor threshold for resizing). There may be much
* variance around this average as mappings are added and removed, but
* overall, this maintains a commonly accepted time/space tradeoff for
* hash tables. However, resizing this or any other kind of hash
* table may be a relatively slow operation. When possible, it is a
* good idea to provide a size estimate as an optional {@code
* initialCapacity} constructor argument. An additional optional
* {@code loadFactor} constructor argument provides a further means of
* customizing initial table capacity by specifying the table density
* to be used in calculating the amount of space to allocate for the
* given number of elements. Also, for compatibility with previous
* versions of this class, constructors may optionally specify an
* expected {@code concurrencyLevel} as an additional hint for
* internal sizing. Note that using many keys with exactly the same
* {@code hashCode()} is a sure way to slow down performance of any
* hash table.
*
* <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 {@code null} to be used as a key or value.
*
* <p>This class is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* <p><em>jsr166e note: This class is a candidate replacement for
* java.util.concurrent.ConcurrentHashMap.<em>
*
* @since 1.5
* @author Doug Lea
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*/
public class ConcurrentHashMapV8<K, V>
implements ConcurrentMap<K, V>, Serializable {
private static final long serialVersionUID = 7249069246763182397L;
/**
* A function computing a mapping from the given key to a value.
* This is a place-holder for an upcoming JDK8 interface.
*/
public static interface MappingFunction<K, V> {
/**
* Returns a non-null value for the given key.
*
* @param key the (non-null) key
* @return a non-null value
*/
V map(K key);
}
/**
* A function computing a new mapping given a key and its current
* mapped value (or {@code null} if there is no current
* mapping). This is a place-holder for an upcoming JDK8
* interface.
*/
public static interface RemappingFunction<K, V> {
/**
* Returns a new value given a key and its current value.
*
* @param key the (non-null) key
* @param value the current value, or null if there is no mapping
* @return a non-null value
*/
V remap(K key, V value);
}
/*
* Overview:
*
* The primary design goal of this hash table is to maintain
* concurrent readability (typically method get(), but also
* iterators and related methods) while minimizing update
* contention. Secondary goals are to keep space consumption about
* the same or better than java.util.HashMap, and to support high
* initial insertion rates on an empty table by many threads.
*
* Each key-value mapping is held in a Node. Because Node fields
* can contain special values, they are defined using plain Object
* types. Similarly in turn, all internal methods that use them
* work off Object types. And similarly, so do the internal
* methods of auxiliary iterator and view classes. All public
* generic typed methods relay in/out of these internal methods,
* supplying null-checks and casts as needed. This also allows
* many of the public methods to be factored into a smaller number
* of internal methods (although sadly not so for the five
* sprawling variants of put-related operations).
*
* The table is lazily initialized to a power-of-two size upon the
* first insertion. Each bin in the table contains a list of
* Nodes (most often, the list has only zero or one Node). Table
* accesses require volatile/atomic reads, writes, and CASes.
* Because there is no other way to arrange this without adding
* further indirections, we use intrinsics (sun.misc.Unsafe)
* operations. The lists of nodes within bins are always
* accurately traversable under volatile reads, so long as lookups
* check hash code and non-nullness of value before checking key
* equality.
*
* We use the top two bits of Node hash fields for control
* purposes -- they are available anyway because of addressing
* constraints. As explained further below, these top bits are
* used as follows:
* 00 - Normal
* 01 - Locked
* 11 - Locked and may have a thread waiting for lock
* 10 - Node is a forwarding node
*
* The lower 30 bits of each Node's hash field contain a
* transformation (for better randomization -- method "spread") of
* the key's hash code, except for forwarding nodes, for which the
* lower bits are zero (and so always have hash field == MOVED).
*
* Insertion (via put or its variants) of the first node in an
* empty bin is performed by just CASing it to the bin. This is
* by far the most common case for put operations. Other update
* operations (insert, delete, and replace) require locks. We do
* not want to waste the space required to associate a distinct
* lock object with each bin, so instead use the first node of a
* bin list itself as a lock. Blocking support for these locks
* relies on the builtin "synchronized" monitors. However, we
* also need a tryLock construction, so we overlay these by using
* bits of the Node hash field for lock control (see above), and
* so normally use builtin monitors only for blocking and
* signalling using wait/notifyAll constructions. See
* Node.tryAwaitLock.
*
* Using the first node of a list as a lock does not by itself
* suffice though: When a node is locked, any update must first
* validate that it is still the first node after locking it, and
* retry if not. Because new nodes are always appended to lists,
* once a node is first in a bin, it remains first until deleted
* or the bin becomes invalidated (upon resizing). However,
* operations that only conditionally update may inspect nodes
* until the point of update. This is a converse of sorts to the
* lazy locking technique described by Herlihy & Shavit.
*
* The main disadvantage of per-bin locks is that other update
* operations on other nodes in a bin list protected by the same
* lock can stall, for example when user equals() or mapping
* functions take a long time. However, statistically, this is
* not a common enough problem to outweigh the time/space overhead
* of alternatives: Under random hash codes, the frequency of
* nodes in bins follows a Poisson distribution
* (http://en.wikipedia.org/wiki/Poisson_distribution) with a
* parameter of about 0.5 on average, given the resizing threshold
* of 0.75, although with a large variance because of resizing
* granularity. Ignoring variance, the expected occurrences of
* list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The
* first few values are:
*
* 0: 0.607
* 1: 0.303
* 2: 0.076
* 3: 0.012
* more: 0.002
*
* Lock contention probability for two threads accessing distinct
* elements is roughly 1 / (8 * #elements). Function "spread"
* performs hashCode randomization that improves the likelihood
* that these assumptions hold unless users define exactly the
* same value for too many hashCodes.
*
* The table is resized when occupancy exceeds an occupancy
* threshold (nominally, 0.75, but see below). Only a single
* thread performs the resize (using field "sizeCtl", to arrange
* exclusion), but the table otherwise remains usable for reads
* and updates. Resizing proceeds by transferring bins, one by
* one, from the table to the next table. 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. On
* average, 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 concurrently traversing table. Upon
* transfer, the old table bin contains only a special forwarding
* node (with hash field "MOVED") that contains the next table as
* its key. On encountering a forwarding node, access and update
* operations restart, using the new table.
*
* Each bin transfer requires its bin lock. However, unlike other
* cases, a transfer can skip a bin if it fails to acquire its
* lock, and revisit it later. Method rebuild maintains a buffer
* of TRANSFER_BUFFER_SIZE bins that have been skipped because of
* failure to acquire a lock, and blocks only if none are
* available (i.e., only very rarely). The transfer operation
* must also ensure that all accessible bins in both the old and
* new table are usable by any traversal. When there are no lock
* acquisition failures, this is arranged simply by proceeding
* from the last bin (table.length - 1) up towards the first.
* Upon seeing a forwarding node, traversals (see class
* InternalIterator) arrange to move to the new table without
* revisiting nodes. However, when any node is skipped during a
* transfer, all earlier table bins may have become visible, so
* are initialized with a reverse-forwarding node back to the old
* table until the new ones are established. (This sometimes
* requires transiently locking a forwarding node, which is
* possible under the above encoding.) These more expensive
* mechanics trigger only when necessary.
*
* The traversal scheme also applies to partial traversals of
* ranges of bins (via an alternate InternalIterator constructor)
* to support partitioned aggregate operations (that are not
* otherwise implemented yet). Also, read-only operations give up
* if ever forwarded to a null table, which provides support for
* shutdown-style clearing, which is also not currently
* implemented.
*
* Lazy table initialization minimizes footprint until first use,
* and also avoids resizings when the first operation is from a
* putAll, constructor with map argument, or deserialization.
* These cases attempt to override the initial capacity settings,
* but harmlessly fail to take effect in cases of races.
*
* The element count is maintained using a LongAdder, which avoids
* contention on updates but can encounter cache thrashing if read
* too frequently during concurrent access. To avoid reading so
* often, resizing is attempted either when a bin lock is
* contended, or upon adding to a bin already holding two or more
* nodes (checked before adding in the xIfAbsent methods, after
* adding in others). Under uniform hash distributions, the
* probability of this occurring at threshold is around 13%,
* meaning that only about 1 in 8 puts check threshold (and after
* resizing, many fewer do so). But this approximation has high
* variance for small table sizes, so we check on any collision
* for sizes <= 64. The bulk putAll operation further reduces
* contention by only committing count updates upon these size
* checks.
*
* Maintaining API and serialization compatibility with previous
* versions of this class introduces several oddities. Mainly: We
* leave untouched but unused constructor arguments refering to
* concurrencyLevel. We accept a loadFactor constructor argument,
* but apply it only to initial table capacity (which is the only
* time that we can guarantee to honor it.) We also declare an
* unused "Segment" class that is instantiated in minimal form
* only when serializing.
*/
/* ---------------- Constants -------------- */
/**
* The largest possible table capacity. This value must be
* exactly 1<<30 to stay within Java array allocation and indexing
* bounds for power of two table sizes, and is further required
* because the top two bits of 32bit hash fields are used for
* control purposes.
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The default initial table capacity. Must be a power of 2
* (i.e., at least 1) and at most MAXIMUM_CAPACITY.
*/
private static final int DEFAULT_CAPACITY = 16;
/**
* The largest possible (non-power of two) array size.
* Needed by toArray and related methods.
*/
static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
/**
* The default concurrency level for this table. Unused but
* defined for compatibility with previous versions of this class.
*/
private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
/**
* The load factor for this table. Overrides of this value in
* constructors affect only the initial table capacity. The
* actual floating point value isn't normally used -- it is
* simpler to use expressions such as {@code n - (n >>> 2)} for
* the associated resizing threshold.
*/
private static final float LOAD_FACTOR = 0.75f;
/**
* The buffer size for skipped bins during transfers. The
* value is arbitrary but should be large enough to avoid
* most locking stalls during resizes.
*/
private static final int TRANSFER_BUFFER_SIZE = 32;
/*
* Encodings for special uses of Node hash fields. See above for
* explanation.
*/
static final int MOVED = 0x80000000; // hash field for forwarding nodes
static final int LOCKED = 0x40000000; // set/tested only as a bit
static final int WAITING = 0xc0000000; // both bits set/tested together
static final int HASH_BITS = 0x3fffffff; // usable bits of normal node hash
/* ---------------- Fields -------------- */
/**
* The array of bins. Lazily initialized upon first insertion.
* Size is always a power of two. Accessed directly by iterators.
*/
transient volatile Node[] table;
/**
* The counter maintaining number of elements.
*/
private transient final LongAdder counter;
/**
* Table initialization and resizing control. When negative, the
* table is being initialized or resized. Otherwise, when table is
* null, holds the initial table size to use upon creation, or 0
* for default. After initialization, holds the next element count
* value upon which to resize the table.
*/
private transient volatile int sizeCtl;
// views
private transient KeySet<K,V> keySet;
private transient Values<K,V> values;
private transient EntrySet<K,V> entrySet;
/** For serialization compatibility. Null unless serialized; see below */
private Segment<K,V>[] segments;
/* ---------------- Nodes -------------- */
/**
* Key-value entry. Note that this is never exported out as a
* user-visible Map.Entry (see WriteThroughEntry and SnapshotEntry
* below). Nodes with a hash field of MOVED are special, and do
* not contain user keys or values. Otherwise, keys are never
* null, and null val fields indicate that a node is in the
* process of being deleted or created. For purposes of read-only
* access, a key may be read before a val, but can only be used
* after checking val to be non-null.
*/
static final class Node {
volatile int hash;
final Object key;
volatile Object val;
volatile Node next;
Node(int hash, Object key, Object val, Node next) {
this.hash = hash;
this.key = key;
this.val = val;
this.next = next;
}
/** CompareAndSet the hash field */
final boolean casHash(int cmp, int val) {
return UNSAFE.compareAndSwapInt(this, hashOffset, cmp, val);
}
/** The number of spins before blocking for a lock */
static final int MAX_SPINS =
Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;
/**
* Spins a while if LOCKED bit set and this node is the first
* of its bin, and then sets WAITING bits on hash field and
* blocks (once) if they are still set. It is OK for this
* method to return even if lock is not available upon exit,
* which enables these simple single-wait mechanics.
*
* The corresponding signalling operation is performed within
* callers: Upon detecting that WAITING has been set when
* unlocking lock (via a failed CAS from non-waiting LOCKED
* state), unlockers acquire the sync lock and perform a
* notifyAll.
*/
final void tryAwaitLock(Node[] tab, int i) {
if (tab != null && i >= 0 && i < tab.length) { // bounds check
int spins = MAX_SPINS, h;
while (tabAt(tab, i) == this && ((h = hash) & LOCKED) != 0) {
if (spins >= 0) {
if (--spins == MAX_SPINS >>> 1)
Thread.yield(); // heuristically yield mid-way
}
else if (casHash(h, h | WAITING)) {
synchronized (this) {
if (tabAt(tab, i) == this &&
(hash & WAITING) == WAITING) {
try {
wait();
} catch (InterruptedException ie) {
Thread.currentThread().interrupt();
}
}
else
notifyAll(); // possibly won race vs signaller
}
break;
}
}
}
}
// Unsafe mechanics for casHash
private static final sun.misc.Unsafe UNSAFE;
private static final long hashOffset;
static {
try {
UNSAFE = getUnsafe();
Class<?> k = Node.class;
hashOffset = UNSAFE.objectFieldOffset
(k.getDeclaredField("hash"));
} catch (Exception e) {
throw new Error(e);
}
}
}
/* ---------------- Table element access -------------- */
/*
* Volatile access methods are used for table elements as well as
* elements of in-progress next table while resizing. Uses are
* null checked by callers, and implicitly bounds-checked, relying
* on the invariants that tab arrays have non-zero size, and all
* indices are masked with (tab.length - 1) which is never
* negative and always less than length. Note that, to be correct
* wrt arbitrary concurrency errors by users, bounds checks must
* operate on local variables, which accounts for some odd-looking
* inline assignments below.
*/
static final Node tabAt(Node[] tab, int i) { // used by InternalIterator
return (Node)UNSAFE.getObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE);
}
private static final boolean casTabAt(Node[] tab, int i, Node c, Node v) {
return UNSAFE.compareAndSwapObject(tab, ((long)i<<ASHIFT)+ABASE, c, v);
}
private static final void setTabAt(Node[] tab, int i, Node v) {
UNSAFE.putObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE, v);
}
/* ---------------- Internal access and update methods -------------- */
/**
* Applies a supplemental hash function to a given hashCode, which
* defends against poor quality hash functions. The result must
* be have the top 2 bits clear. For reasonable performance, this
* function must have good avalanche properties; i.e., that each
* bit of the argument affects each bit of the result. (Although
* we don't care about the unused top 2 bits.)
*/
private static final int spread(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) & HASH_BITS; // mask out top bits
}
/** Implementation for get and containsKey */
private final Object internalGet(Object k) {
int h = spread(k.hashCode());
retry: for (Node[] tab = table; tab != null;) {
Node e; Object ek, ev; int eh; // locals to read fields once
for (e = tabAt(tab, (tab.length - 1) & h); e != null; e = e.next) {
if ((eh = e.hash) == MOVED) {
tab = (Node[])e.key; // restart with new table
continue retry;
}
if ((eh & HASH_BITS) == h && (ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek)))
return ev;
}
break;
}
return null;
}
/**
* Implementation for the four public remove/replace methods:
* Replaces node value with v, conditional upon match of cv if
* non-null. If resulting value is null, delete.
*/
private final Object internalReplace(Object k, Object v, Object cv) {
int h = spread(k.hashCode());
Object oldVal = null;
for (Node[] tab = table;;) {
Node f; int i, fh;
if (tab == null ||
(f = tabAt(tab, i = (tab.length - 1) & h)) == null)
break;
else if ((fh = f.hash) == MOVED)
tab = (Node[])f.key;
else if ((fh & HASH_BITS) != h && f.next == null) // precheck
break; // rules out possible existence
else if ((fh & LOCKED) != 0) {
checkForResize(); // try resizing if can't get lock
f.tryAwaitLock(tab, i);
}
else if (f.casHash(fh, fh | LOCKED)) {
boolean validated = false;
boolean deleted = false;
try {
if (tabAt(tab, i) == f) {
validated = true;
for (Node e = f, pred = null;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h &&
((ev = e.val) != null) &&
((ek = e.key) == k || k.equals(ek))) {
if (cv == null || cv == ev || cv.equals(ev)) {
oldVal = ev;
if ((e.val = v) == null) {
deleted = true;
Node en = e.next;
if (pred != null)
pred.next = en;
else
setTabAt(tab, i, en);
}
}
break;
}
pred = e;
if ((e = e.next) == null)
break;
}
}
} finally {
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (validated) {
if (deleted)
counter.add(-1L);
break;
}
}
}
return oldVal;
}
/*
* Internal versions of the five insertion methods, each a
* little more complicated than the last. All have
* the same basic structure as the first (internalPut):
* 1. If table uninitialized, create
* 2. If bin empty, try to CAS new node
* 3. If bin stale, use new table
* 4. Lock and validate; if valid, scan and add or update
*
* The others interweave other checks and/or alternative actions:
* * Plain put checks for and performs resize after insertion.
* * putIfAbsent prescans for mapping without lock (and fails to add
* if present), which also makes pre-emptive resize checks worthwhile.
* * computeIfAbsent extends form used in putIfAbsent with additional
* mechanics to deal with, calls, potential exceptions and null
* returns from function call.
* * compute uses the same function-call mechanics, but without
* the prescans
* * putAll attempts to pre-allocate enough table space
* and more lazily performs count updates and checks.
*
* Someday when details settle down a bit more, it might be worth
* some factoring to reduce sprawl.
*/
/** Implementation for put */
private final Object internalPut(Object k, Object v) {
int h = spread(k.hashCode());
boolean checkSize = false;
for (Node[] tab = table;;) {
int i; Node f; int fh;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
if (casTabAt(tab, i, null, new Node(h, k, v, null)))
break; // no lock when adding to empty bin
}
else if ((fh = f.hash) == MOVED)
tab = (Node[])f.key;
else if ((fh & LOCKED) != 0) {
checkForResize();
f.tryAwaitLock(tab, i);
}
else if (f.casHash(fh, fh | LOCKED)) {
Object oldVal = null;
boolean validated = false;
try { // needed in case equals() throws
if (tabAt(tab, i) == f) {
validated = true; // retry if 1st already deleted
for (Node e = f;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
oldVal = ev;
e.val = v;
break;
}
Node last = e;
if ((e = e.next) == null) {
last.next = new Node(h, k, v, null);
if (last != f || tab.length <= 64)
checkSize = true;
break;
}
}
}
} finally { // unlock and signal if needed
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (validated) {
if (oldVal != null)
return oldVal;
break;
}
}
}
counter.add(1L);
if (checkSize)
checkForResize();
return null;
}
/** Implementation for putIfAbsent */
private final Object internalPutIfAbsent(Object k, Object v) {
int h = spread(k.hashCode());
for (Node[] tab = table;;) {
int i; Node f; int fh; Object fk, fv;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
if (casTabAt(tab, i, null, new Node(h, k, v, null)))
break;
}
else if ((fh = f.hash) == MOVED)
tab = (Node[])f.key;
else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
((fk = f.key) == k || k.equals(fk)))
return fv;
else {
Node g = f.next;
if (g != null) { // at least 2 nodes -- search and maybe resize
for (Node e = g;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek)))
return ev;
if ((e = e.next) == null) {
checkForResize();
break;
}
}
}
if (((fh = f.hash) & LOCKED) != 0) {
checkForResize();
f.tryAwaitLock(tab, i);
}
else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
Object oldVal = null;
boolean validated = false;
try {
if (tabAt(tab, i) == f) {
validated = true;
for (Node e = f;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
oldVal = ev;
break;
}
Node last = e;
if ((e = e.next) == null) {
last.next = new Node(h, k, v, null);
break;
}
}
}
} finally {
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (validated) {
if (oldVal != null)
return oldVal;
break;
}
}
}
}
counter.add(1L);
return null;
}
/** Implementation for computeIfAbsent */
private final Object internalComputeIfAbsent(K k,
MappingFunction<? super K, ?> mf) {
int h = spread(k.hashCode());
Object val = null;
for (Node[] tab = table;;) {
Node f; int i, fh; Object fk, fv;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
Node node = new Node(fh = h | LOCKED, k, null, null);
boolean validated = false;
if (casTabAt(tab, i, null, node)) {
validated = true;
try {
if ((val = mf.map(k)) != null)
node.val = val;
} finally {
if (val == null)
setTabAt(tab, i, null);
if (!node.casHash(fh, h)) {
node.hash = h;
synchronized (node) { node.notifyAll(); };
}
}
}
if (validated)
break;
}
else if ((fh = f.hash) == MOVED)
tab = (Node[])f.key;
else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
((fk = f.key) == k || k.equals(fk)))
return fv;
else {
Node g = f.next;
if (g != null) {
for (Node e = g;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek)))
return ev;
if ((e = e.next) == null) {
checkForResize();
break;
}
}
}
if (((fh = f.hash) & LOCKED) != 0) {
checkForResize();
f.tryAwaitLock(tab, i);
}
else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
boolean validated = false;
try {
if (tabAt(tab, i) == f) {
validated = true;
for (Node e = f;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
val = ev;
break;
}
Node last = e;
if ((e = e.next) == null) {
if ((val = mf.map(k)) != null)
last.next = new Node(h, k, val, null);
break;
}
}
}
} finally {
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (validated)
break;
}
}
}
if (val == null)
throw new NullPointerException();
counter.add(1L);
return val;
}
/** Implementation for compute */
@SuppressWarnings("unchecked")
private final Object internalCompute(K k,
RemappingFunction<? super K, V> mf) {
int h = spread(k.hashCode());
Object val = null;
boolean added = false;
boolean checkSize = false;
for (Node[] tab = table;;) {
Node f; int i, fh;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
Node node = new Node(fh = h | LOCKED, k, null, null);
boolean validated = false;
if (casTabAt(tab, i, null, node)) {
validated = true;
try {
if ((val = mf.remap(k, null)) != null) {
node.val = val;
added = true;
}
} finally {
if (!added)
setTabAt(tab, i, null);
if (!node.casHash(fh, h)) {
node.hash = h;
synchronized (node) { node.notifyAll(); };
}
}
}
if (validated)
break;
}
else if ((fh = f.hash) == MOVED)
tab = (Node[])f.key;
else if ((fh & LOCKED) != 0) {
checkForResize();
f.tryAwaitLock(tab, i);
}
else if (f.casHash(fh, fh | LOCKED)) {
boolean validated = false;
try {
if (tabAt(tab, i) == f) {
validated = true;
for (Node e = f;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
val = mf.remap(k, (V)ev);
if (val != null)
e.val = val;
break;
}
Node last = e;
if ((e = e.next) == null) {
if ((val = mf.remap(k, null)) != null) {
last.next = new Node(h, k, val, null);
added = true;
if (last != f || tab.length <= 64)
checkSize = true;
}
break;
}
}
}
} finally {
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (validated)
break;
}
}
if (val == null)
throw new NullPointerException();
if (added) {
counter.add(1L);
if (checkSize)
checkForResize();
}
return val;
}
/** Implementation for putAll */
private final void internalPutAll(Map<?, ?> m) {
tryPresize(m.size());
long delta = 0L; // number of uncommitted additions
boolean npe = false; // to throw exception on exit for nulls
try { // to clean up counts on other exceptions
for (Map.Entry<?, ?> entry : m.entrySet()) {
Object k, v;
if (entry == null || (k = entry.getKey()) == null ||
(v = entry.getValue()) == null) {
npe = true;
break;
}
int h = spread(k.hashCode());
for (Node[] tab = table;;) {
int i; Node f; int fh;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null){
if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
++delta;
break;
}
}
else if ((fh = f.hash) == MOVED)
tab = (Node[])f.key;
else if ((fh & LOCKED) != 0) {
counter.add(delta);
delta = 0L;
checkForResize();
f.tryAwaitLock(tab, i);
}
else if (f.casHash(fh, fh | LOCKED)) {
boolean validated = false;
boolean tooLong = false;
try {
if (tabAt(tab, i) == f) {
validated = true;
for (Node e = f;;) {
Object ek, ev;
if ((e.hash & HASH_BITS) == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
e.val = v;
break;
}
Node last = e;
if ((e = e.next) == null) {
++delta;
last.next = new Node(h, k, v, null);
break;
}
tooLong = true;
}
}
} finally {
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (validated) {
if (tooLong) {
counter.add(delta);
delta = 0L;
checkForResize();
}
break;
}
}
}
}
} finally {
if (delta != 0)
counter.add(delta);
}
if (npe)
throw new NullPointerException();
}
/* ---------------- Table Initialization and Resizing -------------- */
/**
* Returns a power of two table size for the given desired capacity.
* See Hackers Delight, sec 3.2
*/
private static final int tableSizeFor(int c) {
int n = c - 1;
n |= n >>> 1;
n |= n >>> 2;
n |= n >>> 4;
n |= n >>> 8;
n |= n >>> 16;
return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
}
/**
* Initializes table, using the size recorded in sizeCtl.
*/
private final Node[] initTable() {
Node[] tab; int sc;
while ((tab = table) == null) {
if ((sc = sizeCtl) < 0)
Thread.yield(); // lost initialization race; just spin
else if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
try {
if ((tab = table) == null) {
int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
tab = table = new Node[n];
sc = n - (n >>> 2);
}
} finally {
sizeCtl = sc;
}
break;
}
}
return tab;
}
/**
* If table is too small and not already resizing, creates next
* table and transfers bins. Rechecks occupancy after a transfer
* to see if another resize is already needed because resizings
* are lagging additions.
*/
private final void checkForResize() {
Node[] tab; int n, sc;
while ((tab = table) != null &&
(n = tab.length) < MAXIMUM_CAPACITY &&
(sc = sizeCtl) >= 0 && counter.sum() >= (long)sc &&
UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
try {
if (tab == table) {
table = rebuild(tab);
sc = (n << 1) - (n >>> 1);
}
} finally {
sizeCtl = sc;
}
}
}
/**
* Tries to presize table to accommodate the given number of elements.
*
* @param size number of elements (doesn't need to be perfectly accurate)
*/
private final void tryPresize(int size) {
int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
tableSizeFor(size + (size >>> 1) + 1);
int sc;
while ((sc = sizeCtl) >= 0) {
Node[] tab = table; int n;
if (tab == null || (n = tab.length) == 0) {
n = (sc > c) ? sc : c;
if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
try {
if (table == tab) {
table = new Node[n];
sc = n - (n >>> 2);
}
} finally {
sizeCtl = sc;
}
}
}
else if (c <= sc || n >= MAXIMUM_CAPACITY)
break;
else if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
try {
if (table == tab) {
table = rebuild(tab);
sc = (n << 1) - (n >>> 1);
}
} finally {
sizeCtl = sc;
}
}
}
}
/*
* Moves and/or copies the nodes in each bin to new table. See
* above for explanation.
*
* @return the new table
*/
private static final Node[] rebuild(Node[] tab) {
int n = tab.length;
Node[] nextTab = new Node[n << 1];
Node fwd = new Node(MOVED, nextTab, null, null);
int[] buffer = null; // holds bins to revisit; null until needed
Node rev = null; // reverse forwarder; null until needed
int nbuffered = 0; // the number of bins in buffer list
int bufferIndex = 0; // buffer index of current buffered bin
int bin = n - 1; // current non-buffered bin or -1 if none
for (int i = bin;;) { // start upwards sweep
int fh; Node f;
if ((f = tabAt(tab, i)) == null) {
if (bin >= 0) { // no lock needed (or available)
if (!casTabAt(tab, i, f, fwd))
continue;
}
else { // transiently use a locked forwarding node
Node g = new Node(MOVED|LOCKED, nextTab, null, null);
if (!casTabAt(tab, i, f, g))
continue;
setTabAt(nextTab, i, null);
setTabAt(nextTab, i + n, null);
setTabAt(tab, i, fwd);
if (!g.casHash(MOVED|LOCKED, MOVED)) {
g.hash = MOVED;
synchronized (g) { g.notifyAll(); }
}
}
}
else if (((fh = f.hash) & LOCKED) == 0 && f.casHash(fh, fh|LOCKED)) {
boolean validated = false;
try { // split to lo and hi lists; copying as needed
if (tabAt(tab, i) == f) {
validated = true;
Node e = f, lastRun = f;
Node lo = null, hi = null;
int runBit = e.hash & n;
for (Node p = e.next; p != null; p = p.next) {
int b = p.hash & n;
if (b != runBit) {
runBit = b;
lastRun = p;
}
}
if (runBit == 0)
lo = lastRun;
else
hi = lastRun;
for (Node p = e; p != lastRun; p = p.next) {
int ph = p.hash & HASH_BITS;
Object pk = p.key, pv = p.val;
if ((ph & n) == 0)
lo = new Node(ph, pk, pv, lo);
else
hi = new Node(ph, pk, pv, hi);
}
setTabAt(nextTab, i, lo);
setTabAt(nextTab, i + n, hi);
setTabAt(tab, i, fwd);
}
} finally {
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (!validated)
continue;
}
else {
if (buffer == null) // initialize buffer for revisits
buffer = new int[TRANSFER_BUFFER_SIZE];
if (bin < 0 && bufferIndex > 0) {
int j = buffer[--bufferIndex];
buffer[bufferIndex] = i;
i = j; // swap with another bin
continue;
}
if (bin < 0 || nbuffered >= TRANSFER_BUFFER_SIZE) {
f.tryAwaitLock(tab, i);
continue; // no other options -- block
}
if (rev == null) // initialize reverse-forwarder
rev = new Node(MOVED, tab, null, null);
if (tabAt(tab, i) != f || (f.hash & LOCKED) == 0)
continue; // recheck before adding to list
buffer[nbuffered++] = i;
setTabAt(nextTab, i, rev); // install place-holders
setTabAt(nextTab, i + n, rev);
}
if (bin > 0)
i = --bin;
else if (buffer != null && nbuffered > 0) {
bin = -1;
i = buffer[bufferIndex = --nbuffered];
}
else
return nextTab;
}
}
/**
* Implementation for clear. Steps through each bin, removing all
* nodes.
*/
private final void internalClear() {
long delta = 0L; // negative number of deletions
int i = 0;
Node[] tab = table;
while (tab != null && i < tab.length) {
int fh;
Node f = tabAt(tab, i);
if (f == null)
++i;
else if ((fh = f.hash) == MOVED)
tab = (Node[])f.key;
else if ((fh & LOCKED) != 0) {
counter.add(delta); // opportunistically update count
delta = 0L;
f.tryAwaitLock(tab, i);
}
else if (f.casHash(fh, fh | LOCKED)) {
boolean validated = false;
try {
if (tabAt(tab, i) == f) {
validated = true;
for (Node e = f; e != null; e = e.next) {
if (e.val != null) { // currently always true
e.val = null;
--delta;
}
}
setTabAt(tab, i, null);
}
} finally {
if (!f.casHash(fh | LOCKED, fh)) {
f.hash = fh;
synchronized (f) { f.notifyAll(); };
}
}
if (validated)
++i;
}
}
if (delta != 0)
counter.add(delta);
}
/* ----------------Table Traversal -------------- */
/**
* Encapsulates traversal for methods such as containsValue; also
* serves as a base class for other iterators.
*
* At each step, the iterator snapshots the key ("nextKey") and
* value ("nextVal") of a valid node (i.e., one that, at point of
* snapshot, has a non-null user value). Because val fields can
* change (including to null, indicating deletion), field nextVal
* might not be accurate at point of use, but still maintains the
* weak consistency property of holding a value that was once
* valid.
*
* Internal traversals directly access these fields, as in:
* {@code while (it.next != null) { process(it.nextKey); it.advance(); }}
*
* Exported iterators (subclasses of ViewIterator) extract key,
* value, or key-value pairs as return values of Iterator.next(),
* and encapsulate the it.next check as hasNext();
*
* The iterator visits once each still-valid node that was
* reachable upon iterator construction. It might miss some that
* were added to a bin after the bin was visited, which is OK wrt
* consistency guarantees. Maintaining this property in the face
* of possible ongoing resizes requires a fair amount of
* bookkeeping state that is difficult to optimize away amidst
* volatile accesses. Even so, traversal maintains reasonable
* throughput.
*
* Normally, iteration proceeds bin-by-bin traversing lists.
* However, if the table has been resized, then all future steps
* must traverse both the bin at the current index as well as at
* (index + baseSize); and so on for further resizings. To
* paranoically cope with potential sharing by users of iterators
* across threads, iteration terminates if a bounds checks fails
* for a table read.
*
* The range-based constructor enables creation of parallel
* range-splitting traversals. (Not yet implemented.)
*/
static class InternalIterator {
Node next; // the next entry to use
Node last; // the last entry used
Object nextKey; // cached key field of next
Object nextVal; // cached val field of next
Node[] tab; // current table; updated if resized
int index; // index of bin to use next
int baseIndex; // current index of initial table
final int baseLimit; // index bound for initial table
final int baseSize; // initial table size
/** Creates iterator for all entries in the table. */
InternalIterator(Node[] tab) {
this.tab = tab;
baseLimit = baseSize = (tab == null) ? 0 : tab.length;
index = baseIndex = 0;
next = null;
advance();
}
/** Creates iterator for the given range of the table */
InternalIterator(Node[] tab, int lo, int hi) {
this.tab = tab;
baseSize = (tab == null) ? 0 : tab.length;
baseLimit = (hi <= baseSize) ? hi : baseSize;
index = baseIndex = (lo >= 0) ? lo : 0;
next = null;
advance();
}
/** Advances next. See above for explanation. */
final void advance() {
Node e = last = next;
outer: do {
if (e != null) // advance past used/skipped node
e = e.next;
while (e == null) { // get to next non-null bin
Node[] t; int b, i, n; // checks must use locals
if ((b = baseIndex) >= baseLimit || (i = index) < 0 ||
(t = tab) == null || i >= (n = t.length))
break outer;
else if ((e = tabAt(t, i)) != null && e.hash == MOVED)
tab = (Node[])e.key; // restarts due to null val
else // visit upper slots if present
index = (i += baseSize) < n ? i : (baseIndex = b + 1);
}
nextKey = e.key;
} while ((nextVal = e.val) == null);// skip deleted or special nodes
next = e;
}
}
/* ---------------- Public operations -------------- */
/**
* Creates a new, empty map with the default initial table size (16),
*/
public ConcurrentHashMapV8() {
this.counter = new LongAdder();
}
/**
* Creates a new, empty map with an initial table size
* accommodating the specified number of elements without the need
* to dynamically resize.
*
* @param initialCapacity The implementation performs internal
* sizing to accommodate this many elements.
* @throws IllegalArgumentException if the initial capacity of
* elements is negative
*/
public ConcurrentHashMapV8(int initialCapacity) {
if (initialCapacity < 0)
throw new IllegalArgumentException();
int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
MAXIMUM_CAPACITY :
tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1));
this.counter = new LongAdder();
this.sizeCtl = cap;
}
/**
* Creates a new map with the same mappings as the given map.
*
* @param m the map
*/
public ConcurrentHashMapV8(Map<? extends K, ? extends V> m) {
this.counter = new LongAdder();
this.sizeCtl = DEFAULT_CAPACITY;
internalPutAll(m);
}
/**
* Creates a new, empty map with an initial table size based on
* the given number of elements ({@code initialCapacity}) and
* initial table density ({@code loadFactor}).
*
* @param initialCapacity the initial capacity. The implementation
* performs internal sizing to accommodate this many elements,
* given the specified load factor.
* @param loadFactor the load factor (table density) for
* establishing the initial table size
* @throws IllegalArgumentException if the initial capacity of
* elements is negative or the load factor is nonpositive
*
* @since 1.6
*/
public ConcurrentHashMapV8(int initialCapacity, float loadFactor) {
this(initialCapacity, loadFactor, 1);
}
/**
* Creates a new, empty map with an initial table size based on
* the given number of elements ({@code initialCapacity}), table
* density ({@code loadFactor}), and number of concurrently
* updating threads ({@code concurrencyLevel}).
*
* @param initialCapacity the initial capacity. The implementation
* performs internal sizing to accommodate this many elements,
* given the specified load factor.
* @param loadFactor the load factor (table density) for
* establishing the initial table size
* @param concurrencyLevel the estimated number of concurrently
* updating threads. The implementation may use this value as
* a sizing hint.
* @throws IllegalArgumentException if the initial capacity is
* negative or the load factor or concurrencyLevel are
* nonpositive
*/
public ConcurrentHashMapV8(int initialCapacity,
float loadFactor, int concurrencyLevel) {
if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
throw new IllegalArgumentException();
if (initialCapacity < concurrencyLevel) // Use at least as many bins
initialCapacity = concurrencyLevel; // as estimated threads
long size = (long)(1.0 + (long)initialCapacity / loadFactor);
int cap = ((size >= (long)MAXIMUM_CAPACITY) ?
MAXIMUM_CAPACITY: tableSizeFor((int)size));
this.counter = new LongAdder();
this.sizeCtl = cap;
}
/**
* {@inheritDoc}
*/
@Override
public boolean isEmpty() {
return counter.sum() <= 0L; // ignore transient negative values
}
/**
* {@inheritDoc}
*/
@Override
public int size() {
long n = counter.sum();
return ((n < 0L) ? 0 :
(n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
(int)n);
}
final long longSize() { // accurate version of size needed for views
long n = counter.sum();
return (n < 0L) ? 0L : n;
}
/**
* 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
@SuppressWarnings("unchecked")
public V get(Object key) {
if (key == null)
throw new NullPointerException();
return (V)internalGet(key);
}
/**
* Tests if the specified object is a key in this table.
*
* @param key possible key
* @return {@code true} if and only if the specified object
* is a key in this table, as determined by the
* {@code equals} method; {@code false} otherwise
* @throws NullPointerException if the specified key is null
*/
@Override
public boolean containsKey(Object key) {
if (key == null)
throw new NullPointerException();
return internalGet(key) != null;
}
/**
* Returns {@code true} if this map maps one or more keys to the
* specified value. Note: This method may require a full traversal
* of the map, and is much slower than method {@code containsKey}.
*
* @param value value whose presence in this map is to be tested
* @return {@code true} if this map maps one or more keys to the
* specified value
* @throws NullPointerException if the specified value is null
*/
@Override
public boolean containsValue(Object value) {
if (value == null)
throw new NullPointerException();
Object v;
InternalIterator it = new InternalIterator(table);
while (it.next != null) {
if ((v = it.nextVal) == value || value.equals(v))
return true;
it.advance();
}
return false;
}
/**
* 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 value a value to search for
* @return {@code true} if and only if some key maps to the
* {@code value} argument in this table as
* determined by the {@code equals} method;
* {@code false} otherwise
* @throws NullPointerException if the specified value is null
*/
public boolean contains(Object value) {
return containsValue(value);
}
/**
* 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 {@code get} method
* with a key that is equal to the original key.
*
* @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 {@code key}, or
* {@code null} if there was no mapping for {@code key}
* @throws NullPointerException if the specified key or value is null
*/
@Override
@SuppressWarnings("unchecked")
public V put(K key, V value) {
if (key == null || value == null)
throw new NullPointerException();
return (V)internalPut(key, value);
}
/**
* {@inheritDoc}
*
* @return the previous value associated with the specified key,
* or {@code null} if there was no mapping for the key
* @throws NullPointerException if the specified key or value is null
*/
@Override
@SuppressWarnings("unchecked")
public V putIfAbsent(K key, V value) {
if (key == null || value == null)
throw new NullPointerException();
return (V)internalPutIfAbsent(key, value);
}
/**
* 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) {
internalPutAll(m);
}
/**
* If the specified key is not already associated with a value,
* computes its value using the given mappingFunction and
* enters it into the map. This is equivalent to
* <pre> {@code
* if (map.containsKey(key))
* return map.get(key);
* value = mappingFunction.map(key);
* map.put(key, value);
* return value;}</pre>
*
* except that the action is performed atomically. If the
* function returns {@code null} (in which case a {@code
* NullPointerException} is thrown), or the function itself throws
* an (unchecked) exception, the exception is rethrown to its
* caller, and no mapping is recorded. Some attempted update
* operations on this map by other threads may be blocked while
* computation is in progress, so the computation should be short
* and simple, and must not attempt to update any other mappings
* of this Map. The most appropriate usage is to construct a new
* object serving as an initial mapped value, or memoized result,
* as in:
*
* <pre> {@code
* map.computeIfAbsent(key, new MappingFunction<K, V>() {
* public V map(K k) { return new Value(f(k)); }});}</pre>
*
* @param key key with which the specified value is to be associated
* @param mappingFunction the function to compute a value
* @return the current (existing or computed) value associated with
* the specified key.
* @throws NullPointerException if the specified key, mappingFunction,
* or computed value is null
* @throws IllegalStateException if the computation detectably
* attempts a recursive update to this map that would
* otherwise never complete
* @throws RuntimeException or Error if the mappingFunction does so,
* in which case the mapping is left unestablished
*/
@SuppressWarnings("unchecked")
public V computeIfAbsent(K key, MappingFunction<? super K, ? extends V> mappingFunction) {
if (key == null || mappingFunction == null)
throw new NullPointerException();
return (V)internalComputeIfAbsent(key, mappingFunction);
}
/**
* Computes and enters a new mapping value given a key and
* its current mapped value (or {@code null} if there is no current
* mapping). This is equivalent to
* <pre> {@code
* map.put(key, remappingFunction.remap(key, map.get(key));
* }</pre>
*
* except that the action is performed atomically. If the
* function returns {@code null} (in which case a {@code
* NullPointerException} is thrown), or the function itself throws
* an (unchecked) exception, the exception is rethrown to its
* caller, and current mapping is left unchanged. Some attempted
* update operations on this map by other threads may be blocked
* while computation is in progress, so the computation should be
* short and simple, and must not attempt to update any other
* mappings of this Map. For example, to either create or
* append new messages to a value mapping:
*
* <pre> {@code
* Map<Key, String> map = ...;
* final String msg = ...;
* map.compute(key, new RemappingFunction<Key, String>() {
* public String remap(Key k, String v) {
* return (v == null) ? msg : v + msg;});}}</pre>
*
* @param key key with which the specified value is to be associated
* @param remappingFunction the function to compute a value
* @return the new value associated with
* the specified key.
* @throws NullPointerException if the specified key or remappingFunction
* or computed value is null
* @throws IllegalStateException if the computation detectably
* attempts a recursive update to this map that would
* otherwise never complete
* @throws RuntimeException or Error if the remappingFunction does so,
* in which case the mapping is unchanged
*/
@SuppressWarnings("unchecked")
public V compute(K key, RemappingFunction<? super K, V> remappingFunction) {
if (key == null || remappingFunction == null)
throw new NullPointerException();
return (V)internalCompute(key, remappingFunction);
}
/**
* 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 {@code key}, or
* {@code null} if there was no mapping for {@code key}
* @throws NullPointerException if the specified key is null
*/
@Override
@SuppressWarnings("unchecked")
public V remove(Object key) {
if (key == null)
throw new NullPointerException();
return (V)internalReplace(key, null, null);
}
/**
* {@inheritDoc}
*
* @throws NullPointerException if the specified key is null
*/
@Override
public boolean remove(Object key, Object value) {
if (key == null)
throw new NullPointerException();
if (value == null)
return false;
return internalReplace(key, null, value) != null;
}
/**
* {@inheritDoc}
*
* @throws NullPointerException if any of the arguments are null
*/
@Override
public boolean replace(K key, V oldValue, V newValue) {
if (key == null || oldValue == null || newValue == null)
throw new NullPointerException();
return internalReplace(key, newValue, oldValue) != null;
}
/**
* {@inheritDoc}
*
* @return the previous value associated with the specified key,
* or {@code null} if there was no mapping for the key
* @throws NullPointerException if the specified key or value is null
*/
@Override
@SuppressWarnings("unchecked")
public V replace(K key, V value) {
if (key == null || value == null)
throw new NullPointerException();
return (V)internalReplace(key, value, null);
}
/**
* Removes all of the mappings from this map.
*/
@Override
public void clear() {
internalClear();
}
/**
* 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 {@code Iterator.remove}, {@code Set.remove},
* {@code removeAll}, {@code retainAll}, and {@code clear}
* operations. It does not support the {@code add} or
* {@code addAll} operations.
*
* <p>The view's {@code iterator} 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() {
KeySet<K,V> ks = keySet;
return (ks != null) ? ks : (keySet = new KeySet<K,V>(this));
}
/**
* 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 {@code Iterator.remove},
* {@code Collection.remove}, {@code removeAll},
* {@code retainAll}, and {@code clear} operations. It does not
* support the {@code add} or {@code addAll} operations.
*
* <p>The view's {@code iterator} 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() {
Values<K,V> vs = values;
return (vs != null) ? vs : (values = new Values<K,V>(this));
}
/**
* 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 {@code Iterator.remove}, {@code Set.remove},
* {@code removeAll}, {@code retainAll}, and {@code clear}
* operations. It does not support the {@code add} or
* {@code addAll} operations.
*
* <p>The view's {@code iterator} 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() {
EntrySet<K,V> es = entrySet;
return (es != null) ? es : (entrySet = new EntrySet<K,V>(this));
}
/**
* 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<K,V>(this);
}
/**
* 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<K,V>(this);
}
/**
* Returns the hash code value for this {@link Map}, i.e.,
* the sum of, for each key-value pair in the map,
* {@code key.hashCode() ^ value.hashCode()}.
*
* @return the hash code value for this map
*/
public int hashCode() {
int h = 0;
InternalIterator it = new InternalIterator(table);
while (it.next != null) {
h += it.nextKey.hashCode() ^ it.nextVal.hashCode();
it.advance();
}
return h;
}
/**
* Returns a string representation of this map. The string
* representation consists of a list of key-value mappings (in no
* particular order) enclosed in braces ("{@code {}}"). Adjacent
* mappings are separated by the characters {@code ", "} (comma
* and space). Each key-value mapping is rendered as the key
* followed by an equals sign ("{@code =}") followed by the
* associated value.
*
* @return a string representation of this map
*/
public String toString() {
InternalIterator it = new InternalIterator(table);
StringBuilder sb = new StringBuilder();
sb.append('{');
if (it.next != null) {
for (;;) {
Object k = it.nextKey, v = it.nextVal;
sb.append(k == this ? "(this Map)" : k);
sb.append('=');
sb.append(v == this ? "(this Map)" : v);
it.advance();
if (it.next == null)
break;
sb.append(',').append(' ');
}
}
return sb.append('}').toString();
}
/**
* Compares the specified object with this map for equality.
* Returns {@code true} if the given object is a map with the same
* mappings as this map. This operation may return misleading
* results if either map is concurrently modified during execution
* of this method.
*
* @param o object to be compared for equality with this map
* @return {@code true} if the specified object is equal to this map
*/
public boolean equals(Object o) {
if (o != this) {
if (!(o instanceof Map))
return false;
Map<?,?> m = (Map<?,?>) o;
InternalIterator it = new InternalIterator(table);
while (it.next != null) {
Object val = it.nextVal;
Object v = m.get(it.nextKey);
if (v == null || (v != val && !v.equals(val)))
return false;
it.advance();
}
for (Map.Entry<?,?> e : m.entrySet()) {
Object mk, mv, v;
if ((mk = e.getKey()) == null ||
(mv = e.getValue()) == null ||
(v = internalGet(mk)) == null ||
(mv != v && !mv.equals(v)))
return false;
}
}
return true;
}
/* ----------------Iterators -------------- */
/**
* Base class for key, value, and entry iterators. Adds a map
* reference to InternalIterator to support Iterator.remove.
*/
static abstract class ViewIterator<K,V> extends InternalIterator {
final ConcurrentHashMapV8<K, V> map;
ViewIterator(ConcurrentHashMapV8<K, V> map) {
super(map.table);
this.map = map;
}
public final void remove() {
if (last == null)
throw new IllegalStateException();
map.remove(last.key);
last = null;
}
public final boolean hasNext() { return next != null; }
public final boolean hasMoreElements() { return next != null; }
}
static final class KeyIterator<K,V> extends ViewIterator<K,V>
implements Iterator<K>, Enumeration<K> {
KeyIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
@Override
@SuppressWarnings("unchecked")
public final K next() {
if (next == null)
throw new NoSuchElementException();
Object k = nextKey;
advance();
return (K)k;
}
@Override
public final K nextElement() { return next(); }
}
static final class ValueIterator<K,V> extends ViewIterator<K,V>
implements Iterator<V>, Enumeration<V> {
ValueIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
@Override
@SuppressWarnings("unchecked")
public final V next() {
if (next == null)
throw new NoSuchElementException();
Object v = nextVal;
advance();
return (V)v;
}
@Override
public final V nextElement() { return next(); }
}
static final class EntryIterator<K,V> extends ViewIterator<K,V>
implements Iterator<Map.Entry<K,V>> {
EntryIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
@Override
@SuppressWarnings("unchecked")
public final Map.Entry<K,V> next() {
if (next == null)
throw new NoSuchElementException();
Object k = nextKey;
Object v = nextVal;
advance();
return new WriteThroughEntry<K,V>((K)k, (V)v, map);
}
}
static final class SnapshotEntryIterator<K,V> extends ViewIterator<K,V>
implements Iterator<Map.Entry<K,V>> {
SnapshotEntryIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
@Override
@SuppressWarnings("unchecked")
public final Map.Entry<K,V> next() {
if (next == null)
throw new NoSuchElementException();
Object k = nextKey;
Object v = nextVal;
advance();
return new SnapshotEntry<K,V>((K)k, (V)v);
}
}
/**
* Base of writeThrough and Snapshot entry classes
*/
static abstract class MapEntry<K,V> implements Map.Entry<K, V> {
final K key; // non-null
V val; // non-null
MapEntry(K key, V val) { this.key = key; this.val = val; }
@Override
public final K getKey() { return key; }
@Override
public final V getValue() { return val; }
public final int hashCode() { return key.hashCode() ^ val.hashCode(); }
public final String toString(){ return key + "=" + val; }
public final boolean equals(Object o) {
Object k, v; Map.Entry<?,?> e;
return ((o instanceof Map.Entry) &&
(k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
(k == key || k.equals(key)) &&
(v == val || v.equals(val)));
}
@Override
public abstract V setValue(V value);
}
/**
* Entry used by EntryIterator.next(), that relays setValue
* changes to the underlying map.
*/
static final class WriteThroughEntry<K,V> extends MapEntry<K,V>
implements Map.Entry<K, V> {
final ConcurrentHashMapV8<K, V> map;
WriteThroughEntry(K key, V val, ConcurrentHashMapV8<K, V> map) {
super(key, val);
this.map = map;
}
/**
* Sets our entry's value and writes 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 final V setValue(V value) {
if (value == null) throw new NullPointerException();
V v = val;
val = value;
map.put(key, value);
return v;
}
}
/**
* Internal version of entry, that doesn't write though changes
*/
static final class SnapshotEntry<K,V> extends MapEntry<K,V>
implements Map.Entry<K, V> {
SnapshotEntry(K key, V val) { super(key, val); }
@Override
public final V setValue(V value) { // only locally update
if (value == null) throw new NullPointerException();
V v = val;
val = value;
return v;
}
}
/* ----------------Views -------------- */
/**
* Base class for views. This is done mainly to allow adding
* customized parallel traversals (not yet implemented.)
*/
static abstract class MapView<K, V> {
final ConcurrentHashMapV8<K, V> map;
MapView(ConcurrentHashMapV8<K, V> map) { this.map = map; }
public final int size() { return map.size(); }
public final boolean isEmpty() { return map.isEmpty(); }
public final void clear() { map.clear(); }
// implementations below rely on concrete classes supplying these
abstract Iterator<?> iter();
abstract public boolean contains(Object o);
abstract public boolean remove(Object o);
private static final String oomeMsg = "Required array size too large";
public final Object[] toArray() {
long sz = map.longSize();
if (sz > (long)(MAX_ARRAY_SIZE))
throw new OutOfMemoryError(oomeMsg);
int n = (int)sz;
Object[] r = new Object[n];
int i = 0;
Iterator<?> it = iter();
while (it.hasNext()) {
if (i == n) {
if (n >= MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
n = MAX_ARRAY_SIZE;
else
n += (n >>> 1) + 1;
r = Arrays.copyOf(r, n);
}
r[i++] = it.next();
}
return (i == n) ? r : Arrays.copyOf(r, i);
}
@SuppressWarnings("unchecked")
public final <T> T[] toArray(T[] a) {
long sz = map.longSize();
if (sz > (long)(MAX_ARRAY_SIZE))
throw new OutOfMemoryError(oomeMsg);
int m = (int)sz;
T[] r = (a.length >= m) ? a :
(T[])java.lang.reflect.Array
.newInstance(a.getClass().getComponentType(), m);
int n = r.length;
int i = 0;
Iterator<?> it = iter();
while (it.hasNext()) {
if (i == n) {
if (n >= MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
n = MAX_ARRAY_SIZE;
else
n += (n >>> 1) + 1;
r = Arrays.copyOf(r, n);
}
r[i++] = (T)it.next();
}
if (a == r && i < n) {
r[i] = null; // null-terminate
return r;
}
return (i == n) ? r : Arrays.copyOf(r, i);
}
public final int hashCode() {
int h = 0;
for (Iterator<?> it = iter(); it.hasNext();)
h += it.next().hashCode();
return h;
}
public final String toString() {
StringBuilder sb = new StringBuilder();
sb.append('[');
Iterator<?> it = iter();
if (it.hasNext()) {
for (;;) {
Object e = it.next();
sb.append(e == this ? "(this Collection)" : e);
if (!it.hasNext())
break;
sb.append(',').append(' ');
}
}
return sb.append(']').toString();
}
public final boolean containsAll(Collection<?> c) {
if (c != this) {
for (Iterator<?> it = c.iterator(); it.hasNext();) {
Object e = it.next();
if (e == null || !contains(e))
return false;
}
}
return true;
}
public final boolean removeAll(Collection<?> c) {
boolean modified = false;
for (Iterator<?> it = iter(); it.hasNext();) {
if (c.contains(it.next())) {
it.remove();
modified = true;
}
}
return modified;
}
public final boolean retainAll(Collection<?> c) {
boolean modified = false;
for (Iterator<?> it = iter(); it.hasNext();) {
if (!c.contains(it.next())) {
it.remove();
modified = true;
}
}
return modified;
}
}
static final class KeySet<K,V> extends MapView<K,V> implements Set<K> {
KeySet(ConcurrentHashMapV8<K, V> map) { super(map); }
@Override
public final boolean contains(Object o) { return map.containsKey(o); }
@Override
public final boolean remove(Object o) { return map.remove(o) != null; }
@Override
public final Iterator<K> iterator() {
return new KeyIterator<K,V>(map);
}
@Override
final Iterator<?> iter() {
return new KeyIterator<K,V>(map);
}
@Override
public final boolean add(K e) {
throw new UnsupportedOperationException();
}
@Override
public final boolean addAll(Collection<? extends K> c) {
throw new UnsupportedOperationException();
}
public boolean equals(Object o) {
Set<?> c;
return ((o instanceof Set) &&
((c = (Set<?>)o) == this ||
(containsAll(c) && c.containsAll(this))));
}
}
static final class Values<K,V> extends MapView<K,V>
implements Collection<V> {
Values(ConcurrentHashMapV8<K, V> map) { super(map); }
@Override
public final boolean contains(Object o) { return map.containsValue(o); }
@Override
public final boolean remove(Object o) {
if (o != null) {
Iterator<V> it = new ValueIterator<K,V>(map);
while (it.hasNext()) {
if (o.equals(it.next())) {
it.remove();
return true;
}
}
}
return false;
}
@Override
public final Iterator<V> iterator() {
return new ValueIterator<K,V>(map);
}
@Override
final Iterator<?> iter() {
return new ValueIterator<K,V>(map);
}
@Override
public final boolean add(V e) {
throw new UnsupportedOperationException();
}
@Override
public final boolean addAll(Collection<? extends V> c) {
throw new UnsupportedOperationException();
}
}
static final class EntrySet<K,V> extends MapView<K,V>
implements Set<Map.Entry<K,V>> {
EntrySet(ConcurrentHashMapV8<K, V> map) { super(map); }
@Override
public final boolean contains(Object o) {
Object k, v, r; Map.Entry<?,?> e;
return ((o instanceof Map.Entry) &&
(k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
(r = map.get(k)) != null &&
(v = e.getValue()) != null &&
(v == r || v.equals(r)));
}
@Override
public final boolean remove(Object o) {
Object k, v; Map.Entry<?,?> e;
return ((o instanceof Map.Entry) &&
(k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
map.remove(k, v));
}
@Override
public final Iterator<Map.Entry<K,V>> iterator() {
return new EntryIterator<K,V>(map);
}
@Override
final Iterator<?> iter() {
return new SnapshotEntryIterator<K,V>(map);
}
@Override
public final boolean add(Entry<K,V> e) {
throw new UnsupportedOperationException();
}
@Override
public final boolean addAll(Collection<? extends Entry<K,V>> c) {
throw new UnsupportedOperationException();
}
public boolean equals(Object o) {
Set<?> c;
return ((o instanceof Set) &&
((c = (Set<?>)o) == this ||
(containsAll(c) && c.containsAll(this))));
}
}
/* ---------------- Serialization Support -------------- */
/**
* Stripped-down version of helper class used in previous version,
* declared for the sake of serialization compatibility
*/
static class Segment<K,V> implements Serializable {
private static final long serialVersionUID = 2249069246763182397L;
final float loadFactor;
Segment(float lf) { this.loadFactor = lf; }
}
/**
* Saves the state of the {@code ConcurrentHashMapV8} instance to a
* stream (i.e., serializes it).
* @param s the stream
* @serialData
* the key (Object) and value (Object)
* for each key-value mapping, followed by a null pair.
* The key-value mappings are emitted in no particular order.
*/
@SuppressWarnings("unchecked")
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
if (segments == null) { // for serialization compatibility
segments = (Segment<K,V>[])
new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];
for (int i = 0; i < segments.length; ++i)
segments[i] = new Segment<K,V>(LOAD_FACTOR);
}
s.defaultWriteObject();
InternalIterator it = new InternalIterator(table);
while (it.next != null) {
s.writeObject(it.nextKey);
s.writeObject(it.nextVal);
it.advance();
}
s.writeObject(null);
s.writeObject(null);
segments = null; // throw away
}
/**
* Reconstitutes the instance from a stream (that is, deserializes it).
* @param s the stream
*/
@SuppressWarnings("unchecked")
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
this.segments = null; // unneeded
// initialize transient final field
UNSAFE.putObjectVolatile(this, counterOffset, new LongAdder());
// Create all nodes, then place in table once size is known
long size = 0L;
Node p = null;
for (;;) {
K k = (K) s.readObject();
V v = (V) s.readObject();
if (k != null && v != null) {
p = new Node(spread(k.hashCode()), k, v, p);
++size;
}
else
break;
}
if (p != null) {
boolean init = false;
int n;
if (size >= (long)(MAXIMUM_CAPACITY >>> 1))
n = MAXIMUM_CAPACITY;
else {
int sz = (int)size;
n = tableSizeFor(sz + (sz >>> 1) + 1);
}
int sc = sizeCtl;
if (n > sc &&
UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
try {
if (table == null) {
init = true;
Node[] tab = new Node[n];
int mask = n - 1;
while (p != null) {
int j = p.hash & mask;
Node next = p.next;
p.next = tabAt(tab, j);
setTabAt(tab, j, p);
p = next;
}
table = tab;
counter.add(size);
sc = n - (n >>> 2);
}
} finally {
sizeCtl = sc;
}
}
if (!init) { // Can only happen if unsafely published.
while (p != null) {
internalPut(p.key, p.val);
p = p.next;
}
}
}
}
// Unsafe mechanics
private static final sun.misc.Unsafe UNSAFE;
private static final long counterOffset;
private static final long sizeCtlOffset;
private static final long ABASE;
private static final int ASHIFT;
static {
int ss;
try {
UNSAFE = getUnsafe();
Class<?> k = ConcurrentHashMapV8.class;
counterOffset = UNSAFE.objectFieldOffset
(k.getDeclaredField("counter"));
sizeCtlOffset = UNSAFE.objectFieldOffset
(k.getDeclaredField("sizeCtl"));
Class<?> sc = Node[].class;
ABASE = UNSAFE.arrayBaseOffset(sc);
ss = UNSAFE.arrayIndexScale(sc);
} catch (Exception e) {
throw new Error(e);
}
if ((ss & (ss-1)) != 0)
throw new Error("data type scale not a power of two");
ASHIFT = 31 - Integer.numberOfLeadingZeros(ss);
}
/**
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package.
* Replace with a simple call to Unsafe.getUnsafe when integrating
* into a jdk.
*
* @return a sun.misc.Unsafe
*/
private static sun.misc.Unsafe getUnsafe() {
try {
return sun.misc.Unsafe.getUnsafe();
} catch (SecurityException se) {
try {
return java.security.AccessController.doPrivileged
(new java.security
.PrivilegedExceptionAction<sun.misc.Unsafe>() {
@Override
public sun.misc.Unsafe run() throws Exception {
java.lang.reflect.Field f = sun.misc
.Unsafe.class.getDeclaredField("theUnsafe");
f.setAccessible(true);
return (sun.misc.Unsafe) f.get(null);
}});
} catch (java.security.PrivilegedActionException e) {
throw new RuntimeException("Could not initialize intrinsics",
e.getCause());
}
}
}
}