> entrySet();
+ public int size();
+ public V getValueOrDefault(Object key, V defaultValue);
+
+ public boolean containsValue(V value);
+ public K findKey(V value);
+}
diff --git a/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMapV8.java b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMapV8.java
new file mode 100644
index 0000000..86aa4eb
--- /dev/null
+++ b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMapV8.java
@@ -0,0 +1,3863 @@
+/*
+ * 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/
+ */
+
+// This is based on the 1.79 version.
+
+package com.concurrent_ruby.ext.jsr166e;
+
+import org.jruby.RubyClass;
+import org.jruby.RubyNumeric;
+import org.jruby.RubyObject;
+import org.jruby.exceptions.RaiseException;
+import com.concurrent_ruby.ext.jsr166y.ThreadLocalRandom;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+
+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.util.concurrent.locks.AbstractQueuedSynchronizer;
+
+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 not entail locking,
+ * and there is not 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.
+ *
+ * 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 completed update operations holding upon their
+ * onset. (More formally, an update operation for a given key bears a
+ * happens-before relation with any (non-null) retrieval for
+ * that key reporting the updated value.) 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 not 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.
+ *
+ *
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.
+ *
+ *
A {@link Set} projection of a ConcurrentHashMapV8 may be created
+ * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed
+ * (using {@link #keySet(Object)} when only keys are of interest, and the
+ * mapped values are (perhaps transiently) not used or all take the
+ * same mapping value.
+ *
+ *
A ConcurrentHashMapV8 can be used as scalable frequency map (a
+ * form of histogram or multiset) by using {@link LongAdder} values
+ * and initializing via {@link #computeIfAbsent}. For example, to add
+ * a count to a {@code ConcurrentHashMapV8 freqs}, you
+ * can use {@code freqs.computeIfAbsent(k -> new
+ * LongAdder()).increment();}
+ *
+ * This class and its views and iterators implement all of the
+ * optional methods of the {@link Map} and {@link Iterator}
+ * interfaces.
+ *
+ *
Like {@link Hashtable} but unlike {@link HashMap}, this class
+ * does not allow {@code null} to be used as a key or value.
+ *
+ *
ConcurrentHashMapV8s support parallel operations using the {@link
+ * ForkJoinPool#commonPool}. (Tasks that may be used in other contexts
+ * are available in class {@link ForkJoinTasks}). These operations are
+ * designed to be safely, and often sensibly, applied even with maps
+ * that are being concurrently updated by other threads; for example,
+ * when computing a snapshot summary of the values in a shared
+ * registry. There are three kinds of operation, each with four
+ * forms, accepting functions with Keys, Values, Entries, and (Key,
+ * Value) arguments and/or return values. (The first three forms are
+ * also available via the {@link #keySet()}, {@link #values()} and
+ * {@link #entrySet()} views). Because the elements of a
+ * ConcurrentHashMapV8 are not ordered in any particular way, and may be
+ * processed in different orders in different parallel executions, the
+ * correctness of supplied functions should not depend on any
+ * ordering, or on any other objects or values that may transiently
+ * change while computation is in progress; and except for forEach
+ * actions, should ideally be side-effect-free.
+ *
+ *
+ * - forEach: Perform a given action on each element.
+ * A variant form applies a given transformation on each element
+ * before performing the action.
+ *
+ * - search: Return the first available non-null result of
+ * applying a given function on each element; skipping further
+ * search when a result is found.
+ *
+ * - reduce: Accumulate each element. The supplied reduction
+ * function cannot rely on ordering (more formally, it should be
+ * both associative and commutative). There are five variants:
+ *
+ *
+ *
+ * - Plain reductions. (There is not a form of this method for
+ * (key, value) function arguments since there is no corresponding
+ * return type.)
+ *
+ * - Mapped reductions that accumulate the results of a given
+ * function applied to each element.
+ *
+ * - Reductions to scalar doubles, longs, and ints, using a
+ * given basis value.
+ *
+ *
+ *
+ *
+ *
+ * The concurrency properties of bulk operations follow
+ * from those of ConcurrentHashMapV8: Any non-null result returned
+ * from {@code get(key)} and related access methods bears a
+ * happens-before relation with the associated insertion or
+ * update. The result of any bulk operation reflects the
+ * composition of these per-element relations (but is not
+ * necessarily atomic with respect to the map as a whole unless it
+ * is somehow known to be quiescent). Conversely, because keys
+ * and values in the map are never null, null serves as a reliable
+ * atomic indicator of the current lack of any result. To
+ * maintain this property, null serves as an implicit basis for
+ * all non-scalar reduction operations. For the double, long, and
+ * int versions, the basis should be one that, when combined with
+ * any other value, returns that other value (more formally, it
+ * should be the identity element for the reduction). Most common
+ * reductions have these properties; for example, computing a sum
+ * with basis 0 or a minimum with basis MAX_VALUE.
+ *
+ *
Search and transformation functions provided as arguments
+ * should similarly return null to indicate the lack of any result
+ * (in which case it is not used). In the case of mapped
+ * reductions, this also enables transformations to serve as
+ * filters, returning null (or, in the case of primitive
+ * specializations, the identity basis) if the element should not
+ * be combined. You can create compound transformations and
+ * filterings by composing them yourself under this "null means
+ * there is nothing there now" rule before using them in search or
+ * reduce operations.
+ *
+ *
Methods accepting and/or returning Entry arguments maintain
+ * key-value associations. They may be useful for example when
+ * finding the key for the greatest value. Note that "plain" Entry
+ * arguments can be supplied using {@code new
+ * AbstractMap.SimpleEntry(k,v)}.
+ *
+ *
Bulk operations may complete abruptly, throwing an
+ * exception encountered in the application of a supplied
+ * function. Bear in mind when handling such exceptions that other
+ * concurrently executing functions could also have thrown
+ * exceptions, or would have done so if the first exception had
+ * not occurred.
+ *
+ *
Parallel speedups for bulk operations compared to sequential
+ * processing are common but not guaranteed. Operations involving
+ * brief functions on small maps may execute more slowly than
+ * sequential loops if the underlying work to parallelize the
+ * computation is more expensive than the computation itself.
+ * Similarly, parallelization may not lead to much actual parallelism
+ * if all processors are busy performing unrelated tasks.
+ *
+ *
All arguments to all task methods must be non-null.
+ *
+ *
jsr166e note: During transition, this class
+ * uses nested functional interfaces with different names but the
+ * same forms as those expected for JDK8.
+ *
+ *
This class is a member of the
+ *
+ * Java Collections Framework.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param the type of keys maintained by this map
+ * @param the type of mapped values
+ */
+public class ConcurrentHashMapV8
+ implements ConcurrentMap, Serializable, ConcurrentHashMap {
+ private static final long serialVersionUID = 7249069246763182397L;
+
+ /**
+ * A partitionable iterator. A Spliterator can be traversed
+ * directly, but can also be partitioned (before traversal) by
+ * creating another Spliterator that covers a non-overlapping
+ * portion of the elements, and so may be amenable to parallel
+ * execution.
+ *
+ * This interface exports a subset of expected JDK8
+ * functionality.
+ *
+ *
Sample usage: Here is one (of the several) ways to compute
+ * the sum of the values held in a map using the ForkJoin
+ * framework. As illustrated here, Spliterators are well suited to
+ * designs in which a task repeatedly splits off half its work
+ * into forked subtasks until small enough to process directly,
+ * and then joins these subtasks. Variants of this style can also
+ * be used in completion-based designs.
+ *
+ *
+ * {@code ConcurrentHashMapV8 m = ...
+ * // split as if have 8 * parallelism, for load balance
+ * int n = m.size();
+ * int p = aForkJoinPool.getParallelism() * 8;
+ * int split = (n < p)? n : p;
+ * long sum = aForkJoinPool.invoke(new SumValues(m.valueSpliterator(), split, null));
+ * // ...
+ * static class SumValues extends RecursiveTask {
+ * final Spliterator s;
+ * final int split; // split while > 1
+ * final SumValues nextJoin; // records forked subtasks to join
+ * SumValues(Spliterator s, int depth, SumValues nextJoin) {
+ * this.s = s; this.depth = depth; this.nextJoin = nextJoin;
+ * }
+ * public Long compute() {
+ * long sum = 0;
+ * SumValues subtasks = null; // fork subtasks
+ * for (int s = split >>> 1; s > 0; s >>>= 1)
+ * (subtasks = new SumValues(s.split(), s, subtasks)).fork();
+ * while (s.hasNext()) // directly process remaining elements
+ * sum += s.next();
+ * for (SumValues t = subtasks; t != null; t = t.nextJoin)
+ * sum += t.join(); // collect subtask results
+ * return sum;
+ * }
+ * }
+ * }
+ */
+ public static interface Spliterator extends Iterator {
+ /**
+ * Returns a Spliterator covering approximately half of the
+ * elements, guaranteed not to overlap with those subsequently
+ * returned by this Spliterator. After invoking this method,
+ * the current Spliterator will not produce any of
+ * the elements of the returned Spliterator, but the two
+ * Spliterators together will produce all of the elements that
+ * would have been produced by this Spliterator had this
+ * method not been called. The exact number of elements
+ * produced by the returned Spliterator is not guaranteed, and
+ * may be zero (i.e., with {@code hasNext()} reporting {@code
+ * false}) if this Spliterator cannot be further split.
+ *
+ * @return a Spliterator covering approximately half of the
+ * elements
+ * @throws IllegalStateException if this Spliterator has
+ * already commenced traversing elements
+ */
+ Spliterator split();
+ }
+
+
+ /*
+ * 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
+ * variants of put-related operations). The validation-based
+ * approach explained below leads to a lot of code sprawl because
+ * retry-control precludes factoring into smaller methods.
+ *
+ * The table is lazily initialized to a power-of-two size upon the
+ * first insertion. Each bin in the table normally 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 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 under most
+ * key/hash distributions. 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, under
+ * random hash codes, this is not a common problem. Ideally, 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 values are:
+ *
+ * 0: 0.60653066
+ * 1: 0.30326533
+ * 2: 0.07581633
+ * 3: 0.01263606
+ * 4: 0.00157952
+ * 5: 0.00015795
+ * 6: 0.00001316
+ * 7: 0.00000094
+ * 8: 0.00000006
+ * more: less than 1 in ten million
+ *
+ * Lock contention probability for two threads accessing distinct
+ * elements is roughly 1 / (8 * #elements) under random hashes.
+ *
+ * Actual hash code distributions encountered in practice
+ * sometimes deviate significantly from uniform randomness. This
+ * includes the case when N > (1<<30), so some keys MUST collide.
+ * Similarly for dumb or hostile usages in which multiple keys are
+ * designed to have identical hash codes. Also, although we guard
+ * against the worst effects of this (see method spread), sets of
+ * hashes may differ only in bits that do not impact their bin
+ * index for a given power-of-two mask. So we use a secondary
+ * strategy that applies when the number of nodes in a bin exceeds
+ * a threshold, and at least one of the keys implements
+ * Comparable. These TreeBins use a balanced tree to hold nodes
+ * (a specialized form of red-black trees), bounding search time
+ * to O(log N). Each search step in a TreeBin is around twice as
+ * slow as in a regular list, but given that N cannot exceed
+ * (1<<64) (before running out of addresses) this bounds search
+ * steps, lock hold times, etc, to reasonable constants (roughly
+ * 100 nodes inspected per operation worst case) so long as keys
+ * are Comparable (which is very common -- String, Long, etc).
+ * TreeBin nodes (TreeNodes) also maintain the same "next"
+ * traversal pointers as regular nodes, so can be traversed in
+ * iterators in the same way.
+ *
+ * The table is resized when occupancy exceeds a percentage
+ * 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 (unless it is a TreeBin). 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 Iter) 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 Traverser constructor)
+ * to support partitioned aggregate operations. 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;
+
+ /**
+ * The bin count threshold for using a tree rather than list for a
+ * bin. The value reflects the approximate break-even point for
+ * using tree-based operations.
+ * Note that Doug's version defaults to 8, but when dealing with
+ * Ruby objects it is actually beneficial to avoid TreeNodes
+ * as long as possible as it usually means going into Ruby land.
+ */
+ private static final int TREE_THRESHOLD = 16;
+
+ /*
+ * 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 KeySetView keySet;
+ private transient ValuesView values;
+ private transient EntrySetView entrySet;
+
+ /** For serialization compatibility. Null unless serialized; see below */
+ private Segment[] segments;
+
+ /* ---------------- 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 Iter
+ return (Node)UNSAFE.getObjectVolatile(tab, ((long)i< 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.
+ *
+ * The initial sanity check on tab and bounds is not currently
+ * necessary in the only usages of this method, but enables
+ * use in other future contexts.
+ */
+ final void tryAwaitLock(Node[] tab, int i) {
+ if (tab != null && i >= 0 && i < tab.length) { // sanity check
+ int r = ThreadLocalRandom.current().nextInt(); // randomize spins
+ int spins = MAX_SPINS, h;
+ while (tabAt(tab, i) == this && ((h = hash) & LOCKED) != 0) {
+ if (spins >= 0) {
+ r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
+ if (r >= 0 && --spins == 0)
+ Thread.yield(); // yield before block
+ }
+ 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);
+ }
+ }
+ }
+
+ /* ---------------- TreeBins -------------- */
+
+ /**
+ * Nodes for use in TreeBins
+ */
+ static final class TreeNode extends Node {
+ TreeNode parent; // red-black tree links
+ TreeNode left;
+ TreeNode right;
+ TreeNode prev; // needed to unlink next upon deletion
+ boolean red;
+
+ TreeNode(int hash, Object key, Object val, Node next, TreeNode parent) {
+ super(hash, key, val, next);
+ this.parent = parent;
+ }
+ }
+
+ /**
+ * A specialized form of red-black tree for use in bins
+ * whose size exceeds a threshold.
+ *
+ * TreeBins use a special form of comparison for search and
+ * related operations (which is the main reason we cannot use
+ * existing collections such as TreeMaps). TreeBins contain
+ * Comparable elements, but may contain others, as well as
+ * elements that are Comparable but not necessarily Comparable
+ * for the same T, so we cannot invoke compareTo among them. To
+ * handle this, the tree is ordered primarily by hash value, then
+ * by getClass().getName() order, and then by Comparator order
+ * among elements of the same class. On lookup at a node, if
+ * elements are not comparable or compare as 0, both left and
+ * right children may need to be searched in the case of tied hash
+ * values. (This corresponds to the full list search that would be
+ * necessary if all elements were non-Comparable and had tied
+ * hashes.) The red-black balancing code is updated from
+ * pre-jdk-collections
+ * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java)
+ * based in turn on Cormen, Leiserson, and Rivest "Introduction to
+ * Algorithms" (CLR).
+ *
+ * TreeBins also maintain a separate locking discipline than
+ * regular bins. Because they are forwarded via special MOVED
+ * nodes at bin heads (which can never change once established),
+ * we cannot use those nodes as locks. Instead, TreeBin
+ * extends AbstractQueuedSynchronizer to support a simple form of
+ * read-write lock. For update operations and table validation,
+ * the exclusive form of lock behaves in the same way as bin-head
+ * locks. However, lookups use shared read-lock mechanics to allow
+ * multiple readers in the absence of writers. Additionally,
+ * these lookups do not ever block: While the lock is not
+ * available, they proceed along the slow traversal path (via
+ * next-pointers) until the lock becomes available or the list is
+ * exhausted, whichever comes first. (These cases are not fast,
+ * but maximize aggregate expected throughput.) The AQS mechanics
+ * for doing this are straightforward. The lock state is held as
+ * AQS getState(). Read counts are negative; the write count (1)
+ * is positive. There are no signalling preferences among readers
+ * and writers. Since we don't need to export full Lock API, we
+ * just override the minimal AQS methods and use them directly.
+ */
+ static final class TreeBin extends AbstractQueuedSynchronizer {
+ private static final long serialVersionUID = 2249069246763182397L;
+ transient TreeNode root; // root of tree
+ transient TreeNode first; // head of next-pointer list
+
+ /* AQS overrides */
+ public final boolean isHeldExclusively() { return getState() > 0; }
+ public final boolean tryAcquire(int ignore) {
+ if (compareAndSetState(0, 1)) {
+ setExclusiveOwnerThread(Thread.currentThread());
+ return true;
+ }
+ return false;
+ }
+ public final boolean tryRelease(int ignore) {
+ setExclusiveOwnerThread(null);
+ setState(0);
+ return true;
+ }
+ public final int tryAcquireShared(int ignore) {
+ for (int c;;) {
+ if ((c = getState()) > 0)
+ return -1;
+ if (compareAndSetState(c, c -1))
+ return 1;
+ }
+ }
+ public final boolean tryReleaseShared(int ignore) {
+ int c;
+ do {} while (!compareAndSetState(c = getState(), c + 1));
+ return c == -1;
+ }
+
+ /** From CLR */
+ private void rotateLeft(TreeNode p) {
+ if (p != null) {
+ TreeNode r = p.right, pp, rl;
+ if ((rl = p.right = r.left) != null)
+ rl.parent = p;
+ if ((pp = r.parent = p.parent) == null)
+ root = r;
+ else if (pp.left == p)
+ pp.left = r;
+ else
+ pp.right = r;
+ r.left = p;
+ p.parent = r;
+ }
+ }
+
+ /** From CLR */
+ private void rotateRight(TreeNode p) {
+ if (p != null) {
+ TreeNode l = p.left, pp, lr;
+ if ((lr = p.left = l.right) != null)
+ lr.parent = p;
+ if ((pp = l.parent = p.parent) == null)
+ root = l;
+ else if (pp.right == p)
+ pp.right = l;
+ else
+ pp.left = l;
+ l.right = p;
+ p.parent = l;
+ }
+ }
+
+ @SuppressWarnings("unchecked") final TreeNode getTreeNode
+ (int h, Object k, TreeNode p) {
+ return getTreeNode(h, (RubyObject)k, p);
+ }
+
+ /**
+ * Returns the TreeNode (or null if not found) for the given key
+ * starting at given root.
+ */
+ @SuppressWarnings("unchecked") final TreeNode getTreeNode
+ (int h, RubyObject k, TreeNode p) {
+ RubyClass c = k.getMetaClass(); boolean kNotComparable = !k.respondsTo("<=>");
+ while (p != null) {
+ int dir, ph; RubyObject pk; RubyClass pc;
+ if ((ph = p.hash) == h) {
+ if ((pk = (RubyObject)p.key) == k || k.equals(pk))
+ return p;
+ if (c != (pc = (RubyClass)pk.getMetaClass()) ||
+ kNotComparable ||
+ (dir = rubyCompare(k, pk)) == 0) {
+ dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
+ if (dir == 0) { // if still stuck, need to check both sides
+ TreeNode r = null, pl, pr;
+ // try to recurse on the right
+ if ((pr = p.right) != null && h >= pr.hash && (r = getTreeNode(h, k, pr)) != null)
+ return r;
+ // try to continue iterating on the left side
+ else if ((pl = p.left) != null && h <= pl.hash)
+ dir = -1;
+ else // no matching node found
+ return null;
+ }
+ }
+ }
+ else
+ dir = (h < ph) ? -1 : 1;
+ p = (dir > 0) ? p.right : p.left;
+ }
+ return null;
+ }
+
+ int rubyCompare(RubyObject l, RubyObject r) {
+ ThreadContext context = l.getMetaClass().getRuntime().getCurrentContext();
+ IRubyObject result;
+ try {
+ result = l.callMethod(context, "<=>", r);
+ } catch (RaiseException e) {
+ // handle objects "lying" about responding to <=>, ie: an Array containing non-comparable keys
+ if (context.runtime.getNoMethodError().isInstance(e.getException())) {
+ return 0;
+ }
+ throw e;
+ }
+
+ return result.isNil() ? 0 : RubyNumeric.num2int(result.convertToInteger());
+ }
+
+ /**
+ * Wrapper for getTreeNode used by CHM.get. Tries to obtain
+ * read-lock to call getTreeNode, but during failure to get
+ * lock, searches along next links.
+ */
+ final Object getValue(int h, Object k) {
+ Node r = null;
+ int c = getState(); // Must read lock state first
+ for (Node e = first; e != null; e = e.next) {
+ if (c <= 0 && compareAndSetState(c, c - 1)) {
+ try {
+ r = getTreeNode(h, k, root);
+ } finally {
+ releaseShared(0);
+ }
+ break;
+ }
+ else if ((e.hash & HASH_BITS) == h && k.equals(e.key)) {
+ r = e;
+ break;
+ }
+ else
+ c = getState();
+ }
+ return r == null ? null : r.val;
+ }
+
+ @SuppressWarnings("unchecked") final TreeNode putTreeNode
+ (int h, Object k, Object v) {
+ return putTreeNode(h, (RubyObject)k, v);
+ }
+
+ /**
+ * Finds or adds a node.
+ * @return null if added
+ */
+ @SuppressWarnings("unchecked") final TreeNode putTreeNode
+ (int h, RubyObject k, Object v) {
+ RubyClass c = k.getMetaClass();
+ boolean kNotComparable = !k.respondsTo("<=>");
+ TreeNode pp = root, p = null;
+ int dir = 0;
+ while (pp != null) { // find existing node or leaf to insert at
+ int ph; RubyObject pk; RubyClass pc;
+ p = pp;
+ if ((ph = p.hash) == h) {
+ if ((pk = (RubyObject)p.key) == k || k.equals(pk))
+ return p;
+ if (c != (pc = pk.getMetaClass()) ||
+ kNotComparable ||
+ (dir = rubyCompare(k, pk)) == 0) {
+ dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
+ if (dir == 0) { // if still stuck, need to check both sides
+ TreeNode r = null, pr;
+ // try to recurse on the right
+ if ((pr = p.right) != null && h >= pr.hash && (r = getTreeNode(h, k, pr)) != null)
+ return r;
+ else // continue descending down the left subtree
+ dir = -1;
+ }
+ }
+ }
+ else
+ dir = (h < ph) ? -1 : 1;
+ pp = (dir > 0) ? p.right : p.left;
+ }
+
+ TreeNode f = first;
+ TreeNode x = first = new TreeNode(h, (Object)k, v, f, p);
+ if (p == null)
+ root = x;
+ else { // attach and rebalance; adapted from CLR
+ TreeNode xp, xpp;
+ if (f != null)
+ f.prev = x;
+ if (dir <= 0)
+ p.left = x;
+ else
+ p.right = x;
+ x.red = true;
+ while (x != null && (xp = x.parent) != null && xp.red &&
+ (xpp = xp.parent) != null) {
+ TreeNode xppl = xpp.left;
+ if (xp == xppl) {
+ TreeNode y = xpp.right;
+ if (y != null && y.red) {
+ y.red = false;
+ xp.red = false;
+ xpp.red = true;
+ x = xpp;
+ }
+ else {
+ if (x == xp.right) {
+ rotateLeft(x = xp);
+ xpp = (xp = x.parent) == null ? null : xp.parent;
+ }
+ if (xp != null) {
+ xp.red = false;
+ if (xpp != null) {
+ xpp.red = true;
+ rotateRight(xpp);
+ }
+ }
+ }
+ }
+ else {
+ TreeNode y = xppl;
+ if (y != null && y.red) {
+ y.red = false;
+ xp.red = false;
+ xpp.red = true;
+ x = xpp;
+ }
+ else {
+ if (x == xp.left) {
+ rotateRight(x = xp);
+ xpp = (xp = x.parent) == null ? null : xp.parent;
+ }
+ if (xp != null) {
+ xp.red = false;
+ if (xpp != null) {
+ xpp.red = true;
+ rotateLeft(xpp);
+ }
+ }
+ }
+ }
+ }
+ TreeNode r = root;
+ if (r != null && r.red)
+ r.red = false;
+ }
+ return null;
+ }
+
+ /**
+ * Removes the given node, that must be present before this
+ * call. This is messier than typical red-black deletion code
+ * because we cannot swap the contents of an interior node
+ * with a leaf successor that is pinned by "next" pointers
+ * that are accessible independently of lock. So instead we
+ * swap the tree linkages.
+ */
+ final void deleteTreeNode(TreeNode p) {
+ TreeNode next = (TreeNode)p.next; // unlink traversal pointers
+ TreeNode pred = p.prev;
+ if (pred == null)
+ first = next;
+ else
+ pred.next = next;
+ if (next != null)
+ next.prev = pred;
+ TreeNode replacement;
+ TreeNode pl = p.left;
+ TreeNode pr = p.right;
+ if (pl != null && pr != null) {
+ TreeNode s = pr, sl;
+ while ((sl = s.left) != null) // find successor
+ s = sl;
+ boolean c = s.red; s.red = p.red; p.red = c; // swap colors
+ TreeNode sr = s.right;
+ TreeNode pp = p.parent;
+ if (s == pr) { // p was s's direct parent
+ p.parent = s;
+ s.right = p;
+ }
+ else {
+ TreeNode sp = s.parent;
+ if ((p.parent = sp) != null) {
+ if (s == sp.left)
+ sp.left = p;
+ else
+ sp.right = p;
+ }
+ if ((s.right = pr) != null)
+ pr.parent = s;
+ }
+ p.left = null;
+ if ((p.right = sr) != null)
+ sr.parent = p;
+ if ((s.left = pl) != null)
+ pl.parent = s;
+ if ((s.parent = pp) == null)
+ root = s;
+ else if (p == pp.left)
+ pp.left = s;
+ else
+ pp.right = s;
+ replacement = sr;
+ }
+ else
+ replacement = (pl != null) ? pl : pr;
+ TreeNode pp = p.parent;
+ if (replacement == null) {
+ if (pp == null) {
+ root = null;
+ return;
+ }
+ replacement = p;
+ }
+ else {
+ replacement.parent = pp;
+ if (pp == null)
+ root = replacement;
+ else if (p == pp.left)
+ pp.left = replacement;
+ else
+ pp.right = replacement;
+ p.left = p.right = p.parent = null;
+ }
+ if (!p.red) { // rebalance, from CLR
+ TreeNode x = replacement;
+ while (x != null) {
+ TreeNode xp, xpl;
+ if (x.red || (xp = x.parent) == null) {
+ x.red = false;
+ break;
+ }
+ if (x == (xpl = xp.left)) {
+ TreeNode sib = xp.right;
+ if (sib != null && sib.red) {
+ sib.red = false;
+ xp.red = true;
+ rotateLeft(xp);
+ sib = (xp = x.parent) == null ? null : xp.right;
+ }
+ if (sib == null)
+ x = xp;
+ else {
+ TreeNode sl = sib.left, sr = sib.right;
+ if ((sr == null || !sr.red) &&
+ (sl == null || !sl.red)) {
+ sib.red = true;
+ x = xp;
+ }
+ else {
+ if (sr == null || !sr.red) {
+ if (sl != null)
+ sl.red = false;
+ sib.red = true;
+ rotateRight(sib);
+ sib = (xp = x.parent) == null ? null : xp.right;
+ }
+ if (sib != null) {
+ sib.red = (xp == null) ? false : xp.red;
+ if ((sr = sib.right) != null)
+ sr.red = false;
+ }
+ if (xp != null) {
+ xp.red = false;
+ rotateLeft(xp);
+ }
+ x = root;
+ }
+ }
+ }
+ else { // symmetric
+ TreeNode sib = xpl;
+ if (sib != null && sib.red) {
+ sib.red = false;
+ xp.red = true;
+ rotateRight(xp);
+ sib = (xp = x.parent) == null ? null : xp.left;
+ }
+ if (sib == null)
+ x = xp;
+ else {
+ TreeNode sl = sib.left, sr = sib.right;
+ if ((sl == null || !sl.red) &&
+ (sr == null || !sr.red)) {
+ sib.red = true;
+ x = xp;
+ }
+ else {
+ if (sl == null || !sl.red) {
+ if (sr != null)
+ sr.red = false;
+ sib.red = true;
+ rotateLeft(sib);
+ sib = (xp = x.parent) == null ? null : xp.left;
+ }
+ if (sib != null) {
+ sib.red = (xp == null) ? false : xp.red;
+ if ((sl = sib.left) != null)
+ sl.red = false;
+ }
+ if (xp != null) {
+ xp.red = false;
+ rotateRight(xp);
+ }
+ x = root;
+ }
+ }
+ }
+ }
+ }
+ if (p == replacement && (pp = p.parent) != null) {
+ if (p == pp.left) // detach pointers
+ pp.left = null;
+ else if (p == pp.right)
+ pp.right = null;
+ p.parent = null;
+ }
+ }
+ }
+
+ /* ---------------- Collision reduction methods -------------- */
+
+ /**
+ * Spreads higher bits to lower, and also forces top 2 bits to 0.
+ * Because the table uses power-of-two masking, sets of hashes
+ * that vary only in bits above the current mask will always
+ * collide. (Among known examples are sets of Float keys holding
+ * consecutive whole numbers in small tables.) To counter this,
+ * we apply a transform that spreads the impact of higher bits
+ * downward. There is a tradeoff between speed, utility, and
+ * quality of bit-spreading. Because many common sets of hashes
+ * are already reasonably distributed across bits (so don't benefit
+ * from spreading), and because we use trees to handle large sets
+ * of collisions in bins, we don't need excessively high quality.
+ */
+ private static final int spread(int h) {
+ h ^= (h >>> 18) ^ (h >>> 12);
+ return (h ^ (h >>> 10)) & HASH_BITS;
+ }
+
+ /**
+ * Replaces a list bin with a tree bin. Call only when locked.
+ * Fails to replace if the given key is non-comparable or table
+ * is, or needs, resizing.
+ */
+ private final void replaceWithTreeBin(Node[] tab, int index, Object key) {
+ if ((key instanceof Comparable) &&
+ (tab.length >= MAXIMUM_CAPACITY || counter.sum() < (long)sizeCtl)) {
+ TreeBin t = new TreeBin();
+ for (Node e = tabAt(tab, index); e != null; e = e.next)
+ t.putTreeNode(e.hash & HASH_BITS, e.key, e.val);
+ setTabAt(tab, index, new Node(MOVED, t, null, null));
+ }
+ }
+
+ /* ---------------- Internal access and update methods -------------- */
+
+ /** 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, p; 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) {
+ if ((ek = e.key) instanceof TreeBin) // search TreeBin
+ return ((TreeBin)ek).getValue(h, k);
+ else { // restart with new table
+ tab = (Node[])ek;
+ continue retry;
+ }
+ }
+ else 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; Object fk;
+ if (tab == null ||
+ (f = tabAt(tab, i = (tab.length - 1) & h)) == null)
+ break;
+ else if ((fh = f.hash) == MOVED) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ boolean validated = false;
+ boolean deleted = false;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ validated = true;
+ TreeNode p = t.getTreeNode(h, k, t.root);
+ if (p != null) {
+ Object pv = p.val;
+ if (cv == null || cv == pv || cv.equals(pv)) {
+ oldVal = pv;
+ if ((p.val = v) == null) {
+ deleted = true;
+ t.deleteTreeNode(p);
+ }
+ }
+ }
+ }
+ } finally {
+ t.release(0);
+ }
+ if (validated) {
+ if (deleted)
+ counter.add(-1L);
+ break;
+ }
+ }
+ else
+ tab = (Node[])fk;
+ }
+ 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 six 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. if bin converted to TreeBin, validate and relay to TreeBin methods
+ * 5. 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
+ * * merge acts as putIfAbsent in the absent case, but invokes the
+ * update function if present
+ * * 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());
+ int count = 0;
+ for (Node[] tab = table;;) {
+ int i; Node f; int fh; Object fk;
+ 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) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ Object oldVal = null;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 2;
+ TreeNode p = t.putTreeNode(h, k, v);
+ if (p != null) {
+ oldVal = p.val;
+ p.val = v;
+ }
+ }
+ } finally {
+ t.release(0);
+ }
+ if (count != 0) {
+ if (oldVal != null)
+ return oldVal;
+ break;
+ }
+ }
+ else
+ tab = (Node[])fk;
+ }
+ else if ((fh & LOCKED) != 0) {
+ checkForResize();
+ f.tryAwaitLock(tab, i);
+ }
+ else if (f.casHash(fh, fh | LOCKED)) {
+ Object oldVal = null;
+ try { // needed in case equals() throws
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ for (Node e = f;; ++count) {
+ 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 (count >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
+ break;
+ }
+ }
+ }
+ } finally { // unlock and signal if needed
+ if (!f.casHash(fh | LOCKED, fh)) {
+ f.hash = fh;
+ synchronized (f) { f.notifyAll(); };
+ }
+ }
+ if (count != 0) {
+ if (oldVal != null)
+ return oldVal;
+ if (tab.length <= 64)
+ count = 2;
+ break;
+ }
+ }
+ }
+ counter.add(1L);
+ if (count > 1)
+ checkForResize();
+ return null;
+ }
+
+ /** Implementation for putIfAbsent */
+ private final Object internalPutIfAbsent(Object k, Object v) {
+ int h = spread(k.hashCode());
+ int count = 0;
+ 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) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ Object oldVal = null;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 2;
+ TreeNode p = t.putTreeNode(h, k, v);
+ if (p != null)
+ oldVal = p.val;
+ }
+ } finally {
+ t.release(0);
+ }
+ if (count != 0) {
+ if (oldVal != null)
+ return oldVal;
+ break;
+ }
+ }
+ else
+ tab = (Node[])fk;
+ }
+ 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;
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ for (Node e = f;; ++count) {
+ 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);
+ if (count >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
+ break;
+ }
+ }
+ }
+ } finally {
+ if (!f.casHash(fh | LOCKED, fh)) {
+ f.hash = fh;
+ synchronized (f) { f.notifyAll(); };
+ }
+ }
+ if (count != 0) {
+ if (oldVal != null)
+ return oldVal;
+ if (tab.length <= 64)
+ count = 2;
+ break;
+ }
+ }
+ }
+ }
+ counter.add(1L);
+ if (count > 1)
+ checkForResize();
+ return null;
+ }
+
+ /** Implementation for computeIfAbsent */
+ private final Object internalComputeIfAbsent(K k,
+ Fun super K, ?> mf) {
+ int h = spread(k.hashCode());
+ Object val = null;
+ int count = 0;
+ 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);
+ if (casTabAt(tab, i, null, node)) {
+ count = 1;
+ try {
+ if ((val = mf.apply(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 (count != 0)
+ break;
+ }
+ else if ((fh = f.hash) == MOVED) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ boolean added = false;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ TreeNode p = t.getTreeNode(h, k, t.root);
+ if (p != null)
+ val = p.val;
+ else if ((val = mf.apply(k)) != null) {
+ added = true;
+ count = 2;
+ t.putTreeNode(h, k, val);
+ }
+ }
+ } finally {
+ t.release(0);
+ }
+ if (count != 0) {
+ if (!added)
+ return val;
+ break;
+ }
+ }
+ else
+ tab = (Node[])fk;
+ }
+ 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 added = false;
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ for (Node e = f;; ++count) {
+ 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.apply(k)) != null) {
+ added = true;
+ last.next = new Node(h, k, val, null);
+ if (count >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
+ }
+ break;
+ }
+ }
+ }
+ } finally {
+ if (!f.casHash(fh | LOCKED, fh)) {
+ f.hash = fh;
+ synchronized (f) { f.notifyAll(); };
+ }
+ }
+ if (count != 0) {
+ if (!added)
+ return val;
+ if (tab.length <= 64)
+ count = 2;
+ break;
+ }
+ }
+ }
+ }
+ if (val != null) {
+ counter.add(1L);
+ if (count > 1)
+ checkForResize();
+ }
+ return val;
+ }
+
+ /** Implementation for compute */
+ @SuppressWarnings("unchecked") private final Object internalCompute
+ (K k, boolean onlyIfPresent, BiFun super K, ? super V, ? extends V> mf) {
+ int h = spread(k.hashCode());
+ Object val = null;
+ int delta = 0;
+ int count = 0;
+ for (Node[] tab = table;;) {
+ Node f; int i, fh; Object fk;
+ if (tab == null)
+ tab = initTable();
+ else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+ if (onlyIfPresent)
+ break;
+ Node node = new Node(fh = h | LOCKED, k, null, null);
+ if (casTabAt(tab, i, null, node)) {
+ try {
+ count = 1;
+ if ((val = mf.apply(k, null)) != null) {
+ node.val = val;
+ delta = 1;
+ }
+ } finally {
+ if (delta == 0)
+ setTabAt(tab, i, null);
+ if (!node.casHash(fh, h)) {
+ node.hash = h;
+ synchronized (node) { node.notifyAll(); };
+ }
+ }
+ }
+ if (count != 0)
+ break;
+ }
+ else if ((fh = f.hash) == MOVED) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ TreeNode p = t.getTreeNode(h, k, t.root);
+ Object pv;
+ if (p == null) {
+ if (onlyIfPresent)
+ break;
+ pv = null;
+ } else
+ pv = p.val;
+ if ((val = mf.apply(k, (V)pv)) != null) {
+ if (p != null)
+ p.val = val;
+ else {
+ count = 2;
+ delta = 1;
+ t.putTreeNode(h, k, val);
+ }
+ }
+ else if (p != null) {
+ delta = -1;
+ t.deleteTreeNode(p);
+ }
+ }
+ } finally {
+ t.release(0);
+ }
+ if (count != 0)
+ break;
+ }
+ else
+ tab = (Node[])fk;
+ }
+ else if ((fh & LOCKED) != 0) {
+ checkForResize();
+ f.tryAwaitLock(tab, i);
+ }
+ else if (f.casHash(fh, fh | LOCKED)) {
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ for (Node e = f, pred = null;; ++count) {
+ Object ek, ev;
+ if ((e.hash & HASH_BITS) == h &&
+ (ev = e.val) != null &&
+ ((ek = e.key) == k || k.equals(ek))) {
+ val = mf.apply(k, (V)ev);
+ if (val != null)
+ e.val = val;
+ else {
+ delta = -1;
+ Node en = e.next;
+ if (pred != null)
+ pred.next = en;
+ else
+ setTabAt(tab, i, en);
+ }
+ break;
+ }
+ pred = e;
+ if ((e = e.next) == null) {
+ if (!onlyIfPresent && (val = mf.apply(k, null)) != null) {
+ pred.next = new Node(h, k, val, null);
+ delta = 1;
+ if (count >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
+ }
+ break;
+ }
+ }
+ }
+ } finally {
+ if (!f.casHash(fh | LOCKED, fh)) {
+ f.hash = fh;
+ synchronized (f) { f.notifyAll(); };
+ }
+ }
+ if (count != 0) {
+ if (tab.length <= 64)
+ count = 2;
+ break;
+ }
+ }
+ }
+ if (delta != 0) {
+ counter.add((long)delta);
+ if (count > 1)
+ checkForResize();
+ }
+ return val;
+ }
+
+ /** Implementation for merge */
+ @SuppressWarnings("unchecked") private final Object internalMerge
+ (K k, V v, BiFun super V, ? super V, ? extends V> mf) {
+ int h = spread(k.hashCode());
+ Object val = null;
+ int delta = 0;
+ int count = 0;
+ 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))) {
+ delta = 1;
+ val = v;
+ break;
+ }
+ }
+ else if ((fh = f.hash) == MOVED) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ TreeNode p = t.getTreeNode(h, k, t.root);
+ val = (p == null) ? v : mf.apply((V)p.val, v);
+ if (val != null) {
+ if (p != null)
+ p.val = val;
+ else {
+ count = 2;
+ delta = 1;
+ t.putTreeNode(h, k, val);
+ }
+ }
+ else if (p != null) {
+ delta = -1;
+ t.deleteTreeNode(p);
+ }
+ }
+ } finally {
+ t.release(0);
+ }
+ if (count != 0)
+ break;
+ }
+ else
+ tab = (Node[])fk;
+ }
+ else if ((fh & LOCKED) != 0) {
+ checkForResize();
+ f.tryAwaitLock(tab, i);
+ }
+ else if (f.casHash(fh, fh | LOCKED)) {
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ for (Node e = f, pred = null;; ++count) {
+ Object ek, ev;
+ if ((e.hash & HASH_BITS) == h &&
+ (ev = e.val) != null &&
+ ((ek = e.key) == k || k.equals(ek))) {
+ val = mf.apply((V)ev, v);
+ if (val != null)
+ e.val = val;
+ else {
+ delta = -1;
+ Node en = e.next;
+ if (pred != null)
+ pred.next = en;
+ else
+ setTabAt(tab, i, en);
+ }
+ break;
+ }
+ pred = e;
+ if ((e = e.next) == null) {
+ val = v;
+ pred.next = new Node(h, k, val, null);
+ delta = 1;
+ if (count >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
+ break;
+ }
+ }
+ }
+ } finally {
+ if (!f.casHash(fh | LOCKED, fh)) {
+ f.hash = fh;
+ synchronized (f) { f.notifyAll(); };
+ }
+ }
+ if (count != 0) {
+ if (tab.length <= 64)
+ count = 2;
+ break;
+ }
+ }
+ }
+ if (delta != 0) {
+ counter.add((long)delta);
+ if (count > 1)
+ 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; Object fk;
+ 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) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ boolean validated = false;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ validated = true;
+ TreeNode p = t.getTreeNode(h, k, t.root);
+ if (p != null)
+ p.val = v;
+ else {
+ t.putTreeNode(h, k, v);
+ ++delta;
+ }
+ }
+ } finally {
+ t.release(0);
+ }
+ if (validated)
+ break;
+ }
+ else
+ tab = (Node[])fk;
+ }
+ else if ((fh & LOCKED) != 0) {
+ counter.add(delta);
+ delta = 0L;
+ checkForResize();
+ f.tryAwaitLock(tab, i);
+ }
+ else if (f.casHash(fh, fh | LOCKED)) {
+ int count = 0;
+ try {
+ if (tabAt(tab, i) == f) {
+ count = 1;
+ for (Node e = f;; ++count) {
+ 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);
+ if (count >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
+ break;
+ }
+ }
+ }
+ } finally {
+ if (!f.casHash(fh | LOCKED, fh)) {
+ f.hash = fh;
+ synchronized (f) { f.notifyAll(); };
+ }
+ }
+ if (count != 0) {
+ if (count > 1) {
+ 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) { // Unbuffered; 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) == MOVED) {
+ Object fk = f.key;
+ if (fk instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ boolean validated = false;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ validated = true;
+ splitTreeBin(nextTab, i, t);
+ setTabAt(tab, i, fwd);
+ }
+ } finally {
+ t.release(0);
+ }
+ if (!validated)
+ continue;
+ }
+ }
+ else if ((fh & 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;
+ splitBin(nextTab, i, f);
+ 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;
+ }
+ }
+
+ /**
+ * Splits a normal bin with list headed by e into lo and hi parts;
+ * installs in given table.
+ */
+ private static void splitBin(Node[] nextTab, int i, Node e) {
+ int bit = nextTab.length >>> 1; // bit to split on
+ int runBit = e.hash & bit;
+ Node lastRun = e, lo = null, hi = null;
+ for (Node p = e.next; p != null; p = p.next) {
+ int b = p.hash & bit;
+ 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 & bit) == 0)
+ lo = new Node(ph, pk, pv, lo);
+ else
+ hi = new Node(ph, pk, pv, hi);
+ }
+ setTabAt(nextTab, i, lo);
+ setTabAt(nextTab, i + bit, hi);
+ }
+
+ /**
+ * Splits a tree bin into lo and hi parts; installs in given table.
+ */
+ private static void splitTreeBin(Node[] nextTab, int i, TreeBin t) {
+ int bit = nextTab.length >>> 1;
+ TreeBin lt = new TreeBin();
+ TreeBin ht = new TreeBin();
+ int lc = 0, hc = 0;
+ for (Node e = t.first; e != null; e = e.next) {
+ int h = e.hash & HASH_BITS;
+ Object k = e.key, v = e.val;
+ if ((h & bit) == 0) {
+ ++lc;
+ lt.putTreeNode(h, k, v);
+ }
+ else {
+ ++hc;
+ ht.putTreeNode(h, k, v);
+ }
+ }
+ Node ln, hn; // throw away trees if too small
+ if (lc <= (TREE_THRESHOLD >>> 1)) {
+ ln = null;
+ for (Node p = lt.first; p != null; p = p.next)
+ ln = new Node(p.hash, p.key, p.val, ln);
+ }
+ else
+ ln = new Node(MOVED, lt, null, null);
+ setTabAt(nextTab, i, ln);
+ if (hc <= (TREE_THRESHOLD >>> 1)) {
+ hn = null;
+ for (Node p = ht.first; p != null; p = p.next)
+ hn = new Node(p.hash, p.key, p.val, hn);
+ }
+ else
+ hn = new Node(MOVED, ht, null, null);
+ setTabAt(nextTab, i + bit, hn);
+ }
+
+ /**
+ * 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; Object fk;
+ Node f = tabAt(tab, i);
+ if (f == null)
+ ++i;
+ else if ((fh = f.hash) == MOVED) {
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ for (Node p = t.first; p != null; p = p.next) {
+ if (p.val != null) { // (currently always true)
+ p.val = null;
+ --delta;
+ }
+ }
+ t.first = null;
+ t.root = null;
+ ++i;
+ }
+ } finally {
+ t.release(0);
+ }
+ }
+ else
+ tab = (Node[])fk;
+ }
+ else if ((fh & LOCKED) != 0) {
+ counter.add(delta); // opportunistically update count
+ delta = 0L;
+ f.tryAwaitLock(tab, i);
+ }
+ else if (f.casHash(fh, fh | LOCKED)) {
+ try {
+ if (tabAt(tab, i) == f) {
+ for (Node e = f; e != null; e = e.next) {
+ if (e.val != null) { // (currently always true)
+ e.val = null;
+ --delta;
+ }
+ }
+ setTabAt(tab, i, null);
+ ++i;
+ }
+ } finally {
+ if (!f.casHash(fh | LOCKED, fh)) {
+ f.hash = fh;
+ synchronized (f) { f.notifyAll(); };
+ }
+ }
+ }
+ }
+ if (delta != 0)
+ counter.add(delta);
+ }
+
+ /* ----------------Table Traversal -------------- */
+
+ /**
+ * Encapsulates traversal for methods such as containsValue; also
+ * serves as a base class for other iterators and bulk tasks.
+ *
+ * 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. To support iterator.remove, the nextKey field is not
+ * updated (nulled out) when the iterator cannot advance.
+ *
+ * Internal traversals directly access these fields, as in:
+ * {@code while (it.advance() != null) { process(it.nextKey); }}
+ *
+ * Exported iterators must track whether the iterator has advanced
+ * (in hasNext vs next) (by setting/checking/nulling field
+ * nextVal), and then extract key, value, or key-value pairs as
+ * return values of next().
+ *
+ * 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.
+ *
+ * This class extends ForkJoinTask to streamline parallel
+ * iteration in bulk operations (see BulkTask). This adds only an
+ * int of space overhead, which is close enough to negligible in
+ * cases where it is not needed to not worry about it. Because
+ * ForkJoinTask is Serializable, but iterators need not be, we
+ * need to add warning suppressions.
+ */
+ @SuppressWarnings("serial") static class Traverser {
+ final ConcurrentHashMapV8 map;
+ Node next; // the next entry to use
+ K nextKey; // cached key field of next
+ V 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
+ int baseLimit; // index bound for initial table
+ int baseSize; // initial table size
+
+ /** Creates iterator for all entries in the table. */
+ Traverser(ConcurrentHashMapV8 map) {
+ this.map = map;
+ }
+
+ /** Creates iterator for split() methods */
+ Traverser(Traverser it) {
+ ConcurrentHashMapV8 m; Node[] t;
+ if ((m = this.map = it.map) == null)
+ t = null;
+ else if ((t = it.tab) == null && // force parent tab initialization
+ (t = it.tab = m.table) != null)
+ it.baseLimit = it.baseSize = t.length;
+ this.tab = t;
+ this.baseSize = it.baseSize;
+ it.baseLimit = this.index = this.baseIndex =
+ ((this.baseLimit = it.baseLimit) + it.baseIndex + 1) >>> 1;
+ }
+
+ /**
+ * Advances next; returns nextVal or null if terminated.
+ * See above for explanation.
+ */
+ final V advance() {
+ Node e = next;
+ V ev = null;
+ outer: do {
+ if (e != null) // advance past used/skipped node
+ e = e.next;
+ while (e == null) { // get to next non-null bin
+ ConcurrentHashMapV8 m;
+ Node[] t; int b, i, n; Object ek; // checks must use locals
+ if ((t = tab) != null)
+ n = t.length;
+ else if ((m = map) != null && (t = tab = m.table) != null)
+ n = baseLimit = baseSize = t.length;
+ else
+ break outer;
+ if ((b = baseIndex) >= baseLimit ||
+ (i = index) < 0 || i >= n)
+ break outer;
+ if ((e = tabAt(t, i)) != null && e.hash == MOVED) {
+ if ((ek = e.key) instanceof TreeBin)
+ e = ((TreeBin)ek).first;
+ else {
+ tab = (Node[])ek;
+ continue; // restarts due to null val
+ }
+ } // visit upper slots if present
+ index = (i += baseSize) < n ? i : (baseIndex = b + 1);
+ }
+ nextKey = (K) e.key;
+ } while ((ev = (V) e.val) == null); // skip deleted or special nodes
+ next = e;
+ return nextVal = ev;
+ }
+
+ public final void remove() {
+ Object k = nextKey;
+ if (k == null && (advance() == null || (k = nextKey) == null))
+ throw new IllegalStateException();
+ map.internalReplace(k, null, null);
+ }
+
+ public final boolean hasNext() {
+ return nextVal != null || advance() != null;
+ }
+
+ public final boolean hasMoreElements() { return hasNext(); }
+ public final void setRawResult(Object x) { }
+ public R getRawResult() { return null; }
+ public boolean exec() { return true; }
+ }
+
+ /* ---------------- 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;
+ }
+
+ /**
+ * Creates a new {@link Set} backed by a ConcurrentHashMapV8
+ * from the given type to {@code Boolean.TRUE}.
+ *
+ * @return the new set
+ */
+ public static KeySetView newKeySet() {
+ return new KeySetView(new ConcurrentHashMapV8(),
+ Boolean.TRUE);
+ }
+
+ /**
+ * Creates a new {@link Set} backed by a ConcurrentHashMapV8
+ * from the given type to {@code Boolean.TRUE}.
+ *
+ * @param initialCapacity The implementation performs internal
+ * sizing to accommodate this many elements.
+ * @throws IllegalArgumentException if the initial capacity of
+ * elements is negative
+ * @return the new set
+ */
+ public static KeySetView newKeySet(int initialCapacity) {
+ return new KeySetView(new ConcurrentHashMapV8(initialCapacity),
+ Boolean.TRUE);
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ public boolean isEmpty() {
+ return counter.sum() <= 0L; // ignore transient negative values
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ public int size() {
+ long n = counter.sum();
+ return ((n < 0L) ? 0 :
+ (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
+ (int)n);
+ }
+
+ /**
+ * Returns the number of mappings. This method should be used
+ * instead of {@link #size} because a ConcurrentHashMapV8 may
+ * contain more mappings than can be represented as an int. The
+ * value returned is a snapshot; the actual count may differ if
+ * there are ongoing concurrent insertions or removals.
+ *
+ * @return the number of mappings
+ */
+ public long mappingCount() {
+ long n = counter.sum();
+ return (n < 0L) ? 0L : n; // ignore transient negative values
+ }
+
+ /**
+ * Returns the value to which the specified key is mapped,
+ * or {@code null} if this map contains no mapping for the key.
+ *
+ * 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
+ */
+ @SuppressWarnings("unchecked") public V get(Object key) {
+ if (key == null)
+ throw new NullPointerException();
+ return (V)internalGet(key);
+ }
+
+ /**
+ * Returns the value to which the specified key is mapped,
+ * or the given defaultValue if this map contains no mapping for the key.
+ *
+ * @param key the key
+ * @param defaultValue the value to return if this map contains
+ * no mapping for the given key
+ * @return the mapping for the key, if present; else the defaultValue
+ * @throws NullPointerException if the specified key is null
+ */
+ @SuppressWarnings("unchecked") public V getValueOrDefault(Object key, V defaultValue) {
+ if (key == null)
+ throw new NullPointerException();
+ V v = (V) internalGet(key);
+ return v == null ? defaultValue : v;
+ }
+
+ /**
+ * 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
+ */
+ 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
+ */
+ public boolean containsValue(Object value) {
+ if (value == null)
+ throw new NullPointerException();
+ Object v;
+ Traverser it = new Traverser(this);
+ while ((v = it.advance()) != null) {
+ if (v == value || value.equals(v))
+ return true;
+ }
+ return false;
+ }
+
+ public K findKey(Object value) {
+ if (value == null)
+ throw new NullPointerException();
+ Object v;
+ Traverser it = new Traverser(this);
+ while ((v = it.advance()) != null) {
+ if (v == value || value.equals(v))
+ return it.nextKey;
+ }
+ return null;
+ }
+
+ /**
+ * 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.
+ *
+ * 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
+ */
+ @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
+ */
+ @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
+ */
+ 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 unless null. This is equivalent to
+ *
{@code
+ * if (map.containsKey(key))
+ * return map.get(key);
+ * value = mappingFunction.apply(key);
+ * if (value != null)
+ * map.put(key, value);
+ * return value;}
+ *
+ * except that the action is performed atomically. If the
+ * function returns {@code null} no mapping is recorded. If 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:
+ *
+ * {@code
+ * map.computeIfAbsent(key, new Fun() {
+ * public V map(K k) { return new Value(f(k)); }});}
+ *
+ * @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, or null if the computed value is null
+ * @throws NullPointerException if the specified key or mappingFunction
+ * 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, Fun super K, ? extends V> mappingFunction) {
+ if (key == null || mappingFunction == null)
+ throw new NullPointerException();
+ return (V)internalComputeIfAbsent(key, mappingFunction);
+ }
+
+ /**
+ * If the given key is present, computes a new mapping value given a key and
+ * its current mapped value. This is equivalent to
+ * {@code
+ * if (map.containsKey(key)) {
+ * value = remappingFunction.apply(key, map.get(key));
+ * if (value != null)
+ * map.put(key, value);
+ * else
+ * map.remove(key);
+ * }
+ * }
+ *
+ * except that the action is performed atomically. If the
+ * function returns {@code null}, the mapping is removed. If the
+ * function itself throws an (unchecked) exception, the exception
+ * is rethrown to its caller, and the 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:
+ *
+ * @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, or null if none
+ * @throws NullPointerException if the specified key or remappingFunction
+ * 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 computeIfPresent
+ (K key, BiFun super K, ? super V, ? extends V> remappingFunction) {
+ if (key == null || remappingFunction == null)
+ throw new NullPointerException();
+ return (V)internalCompute(key, true, remappingFunction);
+ }
+
+ /**
+ * Computes 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
+ * {@code
+ * value = remappingFunction.apply(key, map.get(key));
+ * if (value != null)
+ * map.put(key, value);
+ * else
+ * map.remove(key);
+ * }
+ *
+ * except that the action is performed atomically. If the
+ * function returns {@code null}, the mapping is removed. If the
+ * function itself throws an (unchecked) exception, the exception
+ * is rethrown to its caller, and the 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:
+ *
+ * {@code
+ * Map map = ...;
+ * final String msg = ...;
+ * map.compute(key, new BiFun() {
+ * public String apply(Key k, String v) {
+ * return (v == null) ? msg : v + msg;});}}
+ *
+ * @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, or null if none
+ * @throws NullPointerException if the specified key or remappingFunction
+ * 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, BiFun super K, ? super V, ? extends V> remappingFunction) {
+ if (key == null || remappingFunction == null)
+ throw new NullPointerException();
+ return (V)internalCompute(key, false, remappingFunction);
+ }
+
+ /**
+ * If the specified key is not already associated
+ * with a value, associate it with the given value.
+ * Otherwise, replace the value with the results of
+ * the given remapping function. This is equivalent to:
+ * {@code
+ * if (!map.containsKey(key))
+ * map.put(value);
+ * else {
+ * newValue = remappingFunction.apply(map.get(key), value);
+ * if (value != null)
+ * map.put(key, value);
+ * else
+ * map.remove(key);
+ * }
+ * }
+ * except that the action is performed atomically. If the
+ * function returns {@code null}, the mapping is removed. If the
+ * function itself throws an (unchecked) exception, the exception
+ * is rethrown to its caller, and the 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.
+ */
+ @SuppressWarnings("unchecked") public V merge
+ (K key, V value, BiFun super V, ? super V, ? extends V> remappingFunction) {
+ if (key == null || value == null || remappingFunction == null)
+ throw new NullPointerException();
+ return (V)internalMerge(key, value, 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
+ */
+ @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
+ */
+ 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
+ */
+ 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
+ */
+ @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.
+ */
+ 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.
+ *
+ * @return the set view
+ */
+ public KeySetView keySet() {
+ KeySetView ks = keySet;
+ return (ks != null) ? ks : (keySet = new KeySetView(this, null));
+ }
+
+ /**
+ * Returns a {@link Set} view of the keys in this map, using the
+ * given common mapped value for any additions (i.e., {@link
+ * Collection#add} and {@link Collection#addAll}). This is of
+ * course only appropriate if it is acceptable to use the same
+ * value for all additions from this view.
+ *
+ * @param mappedValue the mapped value to use for any
+ * additions.
+ * @return the set view
+ * @throws NullPointerException if the mappedValue is null
+ */
+ public KeySetView keySet(V mappedValue) {
+ if (mappedValue == null)
+ throw new NullPointerException();
+ return new KeySetView(this, mappedValue);
+ }
+
+ /**
+ * 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.
+ */
+ public ValuesView values() {
+ ValuesView vs = values;
+ return (vs != null) ? vs : (values = new ValuesView(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.
+ *
+ * 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.
+ */
+ public Set> entrySet() {
+ EntrySetView es = entrySet;
+ return (es != null) ? es : (entrySet = new EntrySetView(this));
+ }
+
+ /**
+ * Returns an enumeration of the keys in this table.
+ *
+ * @return an enumeration of the keys in this table
+ * @see #keySet()
+ */
+ public Enumeration keys() {
+ return new KeyIterator(this);
+ }
+
+ /**
+ * Returns an enumeration of the values in this table.
+ *
+ * @return an enumeration of the values in this table
+ * @see #values()
+ */
+ public Enumeration elements() {
+ return new ValueIterator(this);
+ }
+
+ /**
+ * Returns a partitionable iterator of the keys in this map.
+ *
+ * @return a partitionable iterator of the keys in this map
+ */
+ public Spliterator keySpliterator() {
+ return new KeyIterator(this);
+ }
+
+ /**
+ * Returns a partitionable iterator of the values in this map.
+ *
+ * @return a partitionable iterator of the values in this map
+ */
+ public Spliterator valueSpliterator() {
+ return new ValueIterator(this);
+ }
+
+ /**
+ * Returns a partitionable iterator of the entries in this map.
+ *
+ * @return a partitionable iterator of the entries in this map
+ */
+ public Spliterator> entrySpliterator() {
+ return new EntryIterator(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;
+ Traverser it = new Traverser(this);
+ Object v;
+ while ((v = it.advance()) != null) {
+ h += it.nextKey.hashCode() ^ v.hashCode();
+ }
+ 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() {
+ Traverser it = new Traverser(this);
+ StringBuilder sb = new StringBuilder();
+ sb.append('{');
+ Object v;
+ if ((v = it.advance()) != null) {
+ for (;;) {
+ Object k = it.nextKey;
+ sb.append(k == this ? "(this Map)" : k);
+ sb.append('=');
+ sb.append(v == this ? "(this Map)" : v);
+ if ((v = it.advance()) == 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;
+ Traverser it = new Traverser(this);
+ Object val;
+ while ((val = it.advance()) != null) {
+ Object v = m.get(it.nextKey);
+ if (v == null || (v != val && !v.equals(val)))
+ return false;
+ }
+ 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 -------------- */
+
+ @SuppressWarnings("serial") static final class KeyIterator extends Traverser
+ implements Spliterator, Enumeration {
+ KeyIterator(ConcurrentHashMapV8 map) { super(map); }
+ KeyIterator(Traverser it) {
+ super(it);
+ }
+ public KeyIterator split() {
+ if (nextKey != null)
+ throw new IllegalStateException();
+ return new KeyIterator(this);
+ }
+ @SuppressWarnings("unchecked") public final K next() {
+ if (nextVal == null && advance() == null)
+ throw new NoSuchElementException();
+ Object k = nextKey;
+ nextVal = null;
+ return (K) k;
+ }
+
+ public final K nextElement() { return next(); }
+ }
+
+ @SuppressWarnings("serial") static final class ValueIterator extends Traverser
+ implements Spliterator, Enumeration {
+ ValueIterator(ConcurrentHashMapV8 map) { super(map); }
+ ValueIterator(Traverser it) {
+ super(it);
+ }
+ public ValueIterator split() {
+ if (nextKey != null)
+ throw new IllegalStateException();
+ return new ValueIterator(this);
+ }
+
+ @SuppressWarnings("unchecked") public final V next() {
+ Object v;
+ if ((v = nextVal) == null && (v = advance()) == null)
+ throw new NoSuchElementException();
+ nextVal = null;
+ return (V) v;
+ }
+
+ public final V nextElement() { return next(); }
+ }
+
+ @SuppressWarnings("serial") static final class EntryIterator extends Traverser
+ implements Spliterator> {
+ EntryIterator(ConcurrentHashMapV8 map) { super(map); }
+ EntryIterator(Traverser it) {
+ super(it);
+ }
+ public EntryIterator split() {
+ if (nextKey != null)
+ throw new IllegalStateException();
+ return new EntryIterator(this);
+ }
+
+ @SuppressWarnings("unchecked") public final Map.Entry next() {
+ Object v;
+ if ((v = nextVal) == null && (v = advance()) == null)
+ throw new NoSuchElementException();
+ Object k = nextKey;
+ nextVal = null;
+ return new MapEntry((K)k, (V)v, map);
+ }
+ }
+
+ /**
+ * Exported Entry for iterators
+ */
+ static final class MapEntry implements Map.Entry {
+ final K key; // non-null
+ V val; // non-null
+ final ConcurrentHashMapV8 map;
+ MapEntry(K key, V val, ConcurrentHashMapV8 map) {
+ this.key = key;
+ this.val = val;
+ this.map = map;
+ }
+ public final K getKey() { return key; }
+ 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)));
+ }
+
+ /**
+ * Sets our entry's value and writes through to the map. The
+ * value to return is somewhat arbitrary here. Since we do 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.
+ */
+ public final V setValue(V value) {
+ if (value == null) throw new NullPointerException();
+ V v = val;
+ val = value;
+ map.put(key, value);
+ return v;
+ }
+ }
+
+ /* ---------------- Serialization Support -------------- */
+
+ /**
+ * Stripped-down version of helper class used in previous version,
+ * declared for the sake of serialization compatibility
+ */
+ static class Segment 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[])
+ new Segment,?>[DEFAULT_CONCURRENCY_LEVEL];
+ for (int i = 0; i < segments.length; ++i)
+ segments[i] = new Segment(LOAD_FACTOR);
+ }
+ s.defaultWriteObject();
+ Traverser it = new Traverser(this);
+ Object v;
+ while ((v = it.advance()) != null) {
+ s.writeObject(it.nextKey);
+ s.writeObject(v);
+ }
+ 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) {
+ int h = spread(k.hashCode());
+ p = new Node(h, 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;
+ boolean collide = false;
+ 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;
+ Node q = p.next = tabAt(tab, j);
+ setTabAt(tab, j, p);
+ if (!collide && q != null && q.hash == p.hash)
+ collide = true;
+ p = next;
+ }
+ table = tab;
+ counter.add(size);
+ sc = n - (n >>> 2);
+ }
+ } finally {
+ sizeCtl = sc;
+ }
+ if (collide) { // rescan and convert to TreeBins
+ Node[] tab = table;
+ for (int i = 0; i < tab.length; ++i) {
+ int c = 0;
+ for (Node e = tabAt(tab, i); e != null; e = e.next) {
+ if (++c > TREE_THRESHOLD &&
+ (e.key instanceof Comparable)) {
+ replaceWithTreeBin(tab, i, e.key);
+ break;
+ }
+ }
+ }
+ }
+ }
+ if (!init) { // Can only happen if unsafely published.
+ while (p != null) {
+ internalPut(p.key, p.val);
+ p = p.next;
+ }
+ }
+ }
+ }
+
+
+ // -------------------------------------------------------
+
+ // Sams
+ /** Interface describing a void action of one argument */
+ public interface Action { void apply(A a); }
+ /** Interface describing a void action of two arguments */
+ public interface BiAction { void apply(A a, B b); }
+ /** Interface describing a function of one argument */
+ public interface Generator { T apply(); }
+ /** Interface describing a function mapping its argument to a double */
+ public interface ObjectToDouble { double apply(A a); }
+ /** Interface describing a function mapping its argument to a long */
+ public interface ObjectToLong { long apply(A a); }
+ /** Interface describing a function mapping its argument to an int */
+ public interface ObjectToInt {int apply(A a); }
+ /** Interface describing a function mapping two arguments to a double */
+ public interface ObjectByObjectToDouble { double apply(A a, B b); }
+ /** Interface describing a function mapping two arguments to a long */
+ public interface ObjectByObjectToLong { long apply(A a, B b); }
+ /** Interface describing a function mapping two arguments to an int */
+ public interface ObjectByObjectToInt {int apply(A a, B b); }
+ /** Interface describing a function mapping a double to a double */
+ public interface DoubleToDouble { double apply(double a); }
+ /** Interface describing a function mapping a long to a long */
+ public interface LongToLong { long apply(long a); }
+ /** Interface describing a function mapping an int to an int */
+ public interface IntToInt { int apply(int a); }
+ /** Interface describing a function mapping two doubles to a double */
+ public interface DoubleByDoubleToDouble { double apply(double a, double b); }
+ /** Interface describing a function mapping two longs to a long */
+ public interface LongByLongToLong { long apply(long a, long b); }
+ /** Interface describing a function mapping two ints to an int */
+ public interface IntByIntToInt { int apply(int a, int b); }
+
+
+ /* ----------------Views -------------- */
+
+ /**
+ * Base class for views.
+ */
+ static abstract class CHMView {
+ final ConcurrentHashMapV8 map;
+ CHMView(ConcurrentHashMapV8 map) { this.map = map; }
+
+ /**
+ * Returns the map backing this view.
+ *
+ * @return the map backing this view
+ */
+ public ConcurrentHashMapV8 getMap() { return 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 public Iterator> iterator();
+ 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.mappingCount();
+ if (sz > (long)(MAX_ARRAY_SIZE))
+ throw new OutOfMemoryError(oomeMsg);
+ int n = (int)sz;
+ Object[] r = new Object[n];
+ int i = 0;
+ Iterator> it = iterator();
+ 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[] toArray(T[] a) {
+ long sz = map.mappingCount();
+ 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 = iterator();
+ 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 = iterator(); it.hasNext();)
+ h += it.next().hashCode();
+ return h;
+ }
+
+ public final String toString() {
+ StringBuilder sb = new StringBuilder();
+ sb.append('[');
+ Iterator> it = iterator();
+ 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 = iterator(); 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 = iterator(); it.hasNext();) {
+ if (!c.contains(it.next())) {
+ it.remove();
+ modified = true;
+ }
+ }
+ return modified;
+ }
+
+ }
+
+ /**
+ * A view of a ConcurrentHashMapV8 as a {@link Set} of keys, in
+ * which additions may optionally be enabled by mapping to a
+ * common value. This class cannot be directly instantiated. See
+ * {@link #keySet}, {@link #keySet(Object)}, {@link #newKeySet()},
+ * {@link #newKeySet(int)}.
+ */
+ public static class KeySetView extends CHMView implements Set, java.io.Serializable {
+ private static final long serialVersionUID = 7249069246763182397L;
+ private final V value;
+ KeySetView(ConcurrentHashMapV8 map, V value) { // non-public
+ super(map);
+ this.value = value;
+ }
+
+ /**
+ * Returns the default mapped value for additions,
+ * or {@code null} if additions are not supported.
+ *
+ * @return the default mapped value for additions, or {@code null}
+ * if not supported.
+ */
+ public V getMappedValue() { return value; }
+
+ // implement Set API
+
+ public boolean contains(Object o) { return map.containsKey(o); }
+ public boolean remove(Object o) { return map.remove(o) != null; }
+
+ /**
+ * Returns 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.
+ *
+ * @return an iterator over the keys of this map
+ */
+ public Iterator iterator() { return new KeyIterator(map); }
+ public boolean add(K e) {
+ V v;
+ if ((v = value) == null)
+ throw new UnsupportedOperationException();
+ if (e == null)
+ throw new NullPointerException();
+ return map.internalPutIfAbsent(e, v) == null;
+ }
+ public boolean addAll(Collection extends K> c) {
+ boolean added = false;
+ V v;
+ if ((v = value) == null)
+ throw new UnsupportedOperationException();
+ for (K e : c) {
+ if (e == null)
+ throw new NullPointerException();
+ if (map.internalPutIfAbsent(e, v) == null)
+ added = true;
+ }
+ return added;
+ }
+ public boolean equals(Object o) {
+ Set> c;
+ return ((o instanceof Set) &&
+ ((c = (Set>)o) == this ||
+ (containsAll(c) && c.containsAll(this))));
+ }
+ }
+
+ /**
+ * A view of a ConcurrentHashMapV8 as a {@link Collection} of
+ * values, in which additions are disabled. This class cannot be
+ * directly instantiated. See {@link #values},
+ *
+ * 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.
+ */
+ public static final class ValuesView extends CHMView
+ implements Collection {
+ ValuesView(ConcurrentHashMapV8 map) { super(map); }
+ public final boolean contains(Object o) { return map.containsValue(o); }
+ public final boolean remove(Object o) {
+ if (o != null) {
+ Iterator it = new ValueIterator(map);
+ while (it.hasNext()) {
+ if (o.equals(it.next())) {
+ it.remove();
+ return true;
+ }
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Returns 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.
+ *
+ * @return an iterator over the values of this map
+ */
+ public final Iterator iterator() {
+ return new ValueIterator(map);
+ }
+ public final boolean add(V e) {
+ throw new UnsupportedOperationException();
+ }
+ public final boolean addAll(Collection extends V> c) {
+ throw new UnsupportedOperationException();
+ }
+ }
+
+ /**
+ * A view of a ConcurrentHashMapV8 as a {@link Set} of (key, value)
+ * entries. This class cannot be directly instantiated. See
+ * {@link #entrySet}.
+ */
+ public static final class EntrySetView extends CHMView
+ implements Set> {
+ EntrySetView(ConcurrentHashMapV8 map) { super(map); }
+ 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)));
+ }
+ 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));
+ }
+
+ /**
+ * Returns 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.
+ *
+ * @return an iterator over the entries of this map
+ */
+ public final Iterator> iterator() {
+ return new EntryIterator(map);
+ }
+
+ public final boolean add(Entry e) {
+ K key = e.getKey();
+ V value = e.getValue();
+ if (key == null || value == null)
+ throw new NullPointerException();
+ return map.internalPut(key, value) == null;
+ }
+ public final boolean addAll(Collection extends Entry> c) {
+ boolean added = false;
+ for (Entry e : c) {
+ if (add(e))
+ added = true;
+ }
+ return added;
+ }
+ public boolean equals(Object o) {
+ Set> c;
+ return ((o instanceof Set) &&
+ ((c = (Set>)o) == this ||
+ (containsAll(c) && c.containsAll(this))));
+ }
+ }
+
+ // 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() {
+ 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());
+ }
+ }
+ }
+}
diff --git a/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/LongAdder.java b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/LongAdder.java
new file mode 100644
index 0000000..47a923c
--- /dev/null
+++ b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/LongAdder.java
@@ -0,0 +1,203 @@
+/*
+ * 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/
+ */
+
+// This is based on 1.9 version.
+
+package com.concurrent_ruby.ext.jsr166e;
+import java.util.concurrent.atomic.AtomicLong;
+import java.io.IOException;
+import java.io.Serializable;
+import java.io.ObjectInputStream;
+
+/**
+ * One or more variables that together maintain an initially zero
+ * {@code long} sum. When updates (method {@link #add}) are contended
+ * across threads, the set of variables may grow dynamically to reduce
+ * contention. Method {@link #sum} (or, equivalently, {@link
+ * #longValue}) returns the current total combined across the
+ * variables maintaining the sum.
+ *
+ * This class is usually preferable to {@link AtomicLong} when
+ * multiple threads update a common sum that is used for purposes such
+ * as collecting statistics, not for fine-grained synchronization
+ * control. Under low update contention, the two classes have similar
+ * characteristics. But under high contention, expected throughput of
+ * this class is significantly higher, at the expense of higher space
+ * consumption.
+ *
+ *
This class extends {@link Number}, but does not define
+ * methods such as {@code hashCode} and {@code compareTo} because
+ * instances are expected to be mutated, and so are not useful as
+ * collection keys.
+ *
+ *
jsr166e note: This class is targeted to be placed in
+ * java.util.concurrent.atomic.
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class LongAdder extends Striped64 implements Serializable {
+ private static final long serialVersionUID = 7249069246863182397L;
+
+ /**
+ * Version of plus for use in retryUpdate
+ */
+ final long fn(long v, long x) { return v + x; }
+
+ /**
+ * Creates a new adder with initial sum of zero.
+ */
+ public LongAdder() {
+ }
+
+ /**
+ * Adds the given value.
+ *
+ * @param x the value to add
+ */
+ public void add(long x) {
+ Cell[] as; long b, v; HashCode hc; Cell a; int n;
+ if ((as = cells) != null || !casBase(b = base, b + x)) {
+ boolean uncontended = true;
+ int h = (hc = threadHashCode.get()).code;
+ if (as == null || (n = as.length) < 1 ||
+ (a = as[(n - 1) & h]) == null ||
+ !(uncontended = a.cas(v = a.value, v + x)))
+ retryUpdate(x, hc, uncontended);
+ }
+ }
+
+ /**
+ * Equivalent to {@code add(1)}.
+ */
+ public void increment() {
+ add(1L);
+ }
+
+ /**
+ * Equivalent to {@code add(-1)}.
+ */
+ public void decrement() {
+ add(-1L);
+ }
+
+ /**
+ * Returns the current sum. The returned value is NOT an
+ * atomic snapshot: Invocation in the absence of concurrent
+ * updates returns an accurate result, but concurrent updates that
+ * occur while the sum is being calculated might not be
+ * incorporated.
+ *
+ * @return the sum
+ */
+ public long sum() {
+ long sum = base;
+ Cell[] as = cells;
+ if (as != null) {
+ int n = as.length;
+ for (int i = 0; i < n; ++i) {
+ Cell a = as[i];
+ if (a != null)
+ sum += a.value;
+ }
+ }
+ return sum;
+ }
+
+ /**
+ * Resets variables maintaining the sum to zero. This method may
+ * be a useful alternative to creating a new adder, but is only
+ * effective if there are no concurrent updates. Because this
+ * method is intrinsically racy, it should only be used when it is
+ * known that no threads are concurrently updating.
+ */
+ public void reset() {
+ internalReset(0L);
+ }
+
+ /**
+ * Equivalent in effect to {@link #sum} followed by {@link
+ * #reset}. This method may apply for example during quiescent
+ * points between multithreaded computations. If there are
+ * updates concurrent with this method, the returned value is
+ * not guaranteed to be the final value occurring before
+ * the reset.
+ *
+ * @return the sum
+ */
+ public long sumThenReset() {
+ long sum = base;
+ Cell[] as = cells;
+ base = 0L;
+ if (as != null) {
+ int n = as.length;
+ for (int i = 0; i < n; ++i) {
+ Cell a = as[i];
+ if (a != null) {
+ sum += a.value;
+ a.value = 0L;
+ }
+ }
+ }
+ return sum;
+ }
+
+ /**
+ * Returns the String representation of the {@link #sum}.
+ * @return the String representation of the {@link #sum}
+ */
+ public String toString() {
+ return Long.toString(sum());
+ }
+
+ /**
+ * Equivalent to {@link #sum}.
+ *
+ * @return the sum
+ */
+ public long longValue() {
+ return sum();
+ }
+
+ /**
+ * Returns the {@link #sum} as an {@code int} after a narrowing
+ * primitive conversion.
+ */
+ public int intValue() {
+ return (int)sum();
+ }
+
+ /**
+ * Returns the {@link #sum} as a {@code float}
+ * after a widening primitive conversion.
+ */
+ public float floatValue() {
+ return (float)sum();
+ }
+
+ /**
+ * Returns the {@link #sum} as a {@code double} after a widening
+ * primitive conversion.
+ */
+ public double doubleValue() {
+ return (double)sum();
+ }
+
+ private void writeObject(java.io.ObjectOutputStream s)
+ throws java.io.IOException {
+ s.defaultWriteObject();
+ s.writeLong(sum());
+ }
+
+ private void readObject(ObjectInputStream s)
+ throws IOException, ClassNotFoundException {
+ s.defaultReadObject();
+ busy = 0;
+ cells = null;
+ base = s.readLong();
+ }
+
+}
diff --git a/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/Striped64.java b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/Striped64.java
new file mode 100644
index 0000000..93a277f
--- /dev/null
+++ b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/Striped64.java
@@ -0,0 +1,342 @@
+/*
+ * 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/
+ */
+
+// This is based on 1.5 version.
+
+package com.concurrent_ruby.ext.jsr166e;
+import java.util.Random;
+
+/**
+ * A package-local class holding common representation and mechanics
+ * for classes supporting dynamic striping on 64bit values. The class
+ * extends Number so that concrete subclasses must publicly do so.
+ */
+abstract class Striped64 extends Number {
+ /*
+ * This class maintains a lazily-initialized table of atomically
+ * updated variables, plus an extra "base" field. The table size
+ * is a power of two. Indexing uses masked per-thread hash codes.
+ * Nearly all declarations in this class are package-private,
+ * accessed directly by subclasses.
+ *
+ * Table entries are of class Cell; a variant of AtomicLong padded
+ * to reduce cache contention on most processors. Padding is
+ * overkill for most Atomics because they are usually irregularly
+ * scattered in memory and thus don't interfere much with each
+ * other. But Atomic objects residing in arrays will tend to be
+ * placed adjacent to each other, and so will most often share
+ * cache lines (with a huge negative performance impact) without
+ * this precaution.
+ *
+ * In part because Cells are relatively large, we avoid creating
+ * them until they are needed. When there is no contention, all
+ * updates are made to the base field. Upon first contention (a
+ * failed CAS on base update), the table is initialized to size 2.
+ * The table size is doubled upon further contention until
+ * reaching the nearest power of two greater than or equal to the
+ * number of CPUS. Table slots remain empty (null) until they are
+ * needed.
+ *
+ * A single spinlock ("busy") is used for initializing and
+ * resizing the table, as well as populating slots with new Cells.
+ * There is no need for a blocking lock: When the lock is not
+ * available, threads try other slots (or the base). During these
+ * retries, there is increased contention and reduced locality,
+ * which is still better than alternatives.
+ *
+ * Per-thread hash codes are initialized to random values.
+ * Contention and/or table collisions are indicated by failed
+ * CASes when performing an update operation (see method
+ * retryUpdate). Upon a collision, if the table size is less than
+ * the capacity, it is doubled in size unless some other thread
+ * holds the lock. If a hashed slot is empty, and lock is
+ * available, a new Cell is created. Otherwise, if the slot
+ * exists, a CAS is tried. Retries proceed by "double hashing",
+ * using a secondary hash (Marsaglia XorShift) to try to find a
+ * free slot.
+ *
+ * The table size is capped because, when there are more threads
+ * than CPUs, supposing that each thread were bound to a CPU,
+ * there would exist a perfect hash function mapping threads to
+ * slots that eliminates collisions. When we reach capacity, we
+ * search for this mapping by randomly varying the hash codes of
+ * colliding threads. Because search is random, and collisions
+ * only become known via CAS failures, convergence can be slow,
+ * and because threads are typically not bound to CPUS forever,
+ * may not occur at all. However, despite these limitations,
+ * observed contention rates are typically low in these cases.
+ *
+ * It is possible for a Cell to become unused when threads that
+ * once hashed to it terminate, as well as in the case where
+ * doubling the table causes no thread to hash to it under
+ * expanded mask. We do not try to detect or remove such cells,
+ * under the assumption that for long-running instances, observed
+ * contention levels will recur, so the cells will eventually be
+ * needed again; and for short-lived ones, it does not matter.
+ */
+
+ /**
+ * Padded variant of AtomicLong supporting only raw accesses plus CAS.
+ * The value field is placed between pads, hoping that the JVM doesn't
+ * reorder them.
+ *
+ * JVM intrinsics note: It would be possible to use a release-only
+ * form of CAS here, if it were provided.
+ */
+ static final class Cell {
+ volatile long p0, p1, p2, p3, p4, p5, p6;
+ volatile long value;
+ volatile long q0, q1, q2, q3, q4, q5, q6;
+ Cell(long x) { value = x; }
+
+ final boolean cas(long cmp, long val) {
+ return UNSAFE.compareAndSwapLong(this, valueOffset, cmp, val);
+ }
+
+ // Unsafe mechanics
+ private static final sun.misc.Unsafe UNSAFE;
+ private static final long valueOffset;
+ static {
+ try {
+ UNSAFE = getUnsafe();
+ Class> ak = Cell.class;
+ valueOffset = UNSAFE.objectFieldOffset
+ (ak.getDeclaredField("value"));
+ } catch (Exception e) {
+ throw new Error(e);
+ }
+ }
+
+ }
+
+ /**
+ * Holder for the thread-local hash code. The code is initially
+ * random, but may be set to a different value upon collisions.
+ */
+ static final class HashCode {
+ static final Random rng = new Random();
+ int code;
+ HashCode() {
+ int h = rng.nextInt(); // Avoid zero to allow xorShift rehash
+ code = (h == 0) ? 1 : h;
+ }
+ }
+
+ /**
+ * The corresponding ThreadLocal class
+ */
+ static final class ThreadHashCode extends ThreadLocal {
+ public HashCode initialValue() { return new HashCode(); }
+ }
+
+ /**
+ * Static per-thread hash codes. Shared across all instances to
+ * reduce ThreadLocal pollution and because adjustments due to
+ * collisions in one table are likely to be appropriate for
+ * others.
+ */
+ static final ThreadHashCode threadHashCode = new ThreadHashCode();
+
+ /** Number of CPUS, to place bound on table size */
+ static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+ /**
+ * Table of cells. When non-null, size is a power of 2.
+ */
+ transient volatile Cell[] cells;
+
+ /**
+ * Base value, used mainly when there is no contention, but also as
+ * a fallback during table initialization races. Updated via CAS.
+ */
+ transient volatile long base;
+
+ /**
+ * Spinlock (locked via CAS) used when resizing and/or creating Cells.
+ */
+ transient volatile int busy;
+
+ /**
+ * Package-private default constructor
+ */
+ Striped64() {
+ }
+
+ /**
+ * CASes the base field.
+ */
+ final boolean casBase(long cmp, long val) {
+ return UNSAFE.compareAndSwapLong(this, baseOffset, cmp, val);
+ }
+
+ /**
+ * CASes the busy field from 0 to 1 to acquire lock.
+ */
+ final boolean casBusy() {
+ return UNSAFE.compareAndSwapInt(this, busyOffset, 0, 1);
+ }
+
+ /**
+ * Computes the function of current and new value. Subclasses
+ * should open-code this update function for most uses, but the
+ * virtualized form is needed within retryUpdate.
+ *
+ * @param currentValue the current value (of either base or a cell)
+ * @param newValue the argument from a user update call
+ * @return result of the update function
+ */
+ abstract long fn(long currentValue, long newValue);
+
+ /**
+ * Handles cases of updates involving initialization, resizing,
+ * creating new Cells, and/or contention. See above for
+ * explanation. This method suffers the usual non-modularity
+ * problems of optimistic retry code, relying on rechecked sets of
+ * reads.
+ *
+ * @param x the value
+ * @param hc the hash code holder
+ * @param wasUncontended false if CAS failed before call
+ */
+ final void retryUpdate(long x, HashCode hc, boolean wasUncontended) {
+ int h = hc.code;
+ boolean collide = false; // True if last slot nonempty
+ for (;;) {
+ Cell[] as; Cell a; int n; long v;
+ if ((as = cells) != null && (n = as.length) > 0) {
+ if ((a = as[(n - 1) & h]) == null) {
+ if (busy == 0) { // Try to attach new Cell
+ Cell r = new Cell(x); // Optimistically create
+ if (busy == 0 && casBusy()) {
+ boolean created = false;
+ try { // Recheck under lock
+ Cell[] rs; int m, j;
+ if ((rs = cells) != null &&
+ (m = rs.length) > 0 &&
+ rs[j = (m - 1) & h] == null) {
+ rs[j] = r;
+ created = true;
+ }
+ } finally {
+ busy = 0;
+ }
+ if (created)
+ break;
+ continue; // Slot is now non-empty
+ }
+ }
+ collide = false;
+ }
+ else if (!wasUncontended) // CAS already known to fail
+ wasUncontended = true; // Continue after rehash
+ else if (a.cas(v = a.value, fn(v, x)))
+ break;
+ else if (n >= NCPU || cells != as)
+ collide = false; // At max size or stale
+ else if (!collide)
+ collide = true;
+ else if (busy == 0 && casBusy()) {
+ try {
+ if (cells == as) { // Expand table unless stale
+ Cell[] rs = new Cell[n << 1];
+ for (int i = 0; i < n; ++i)
+ rs[i] = as[i];
+ cells = rs;
+ }
+ } finally {
+ busy = 0;
+ }
+ collide = false;
+ continue; // Retry with expanded table
+ }
+ h ^= h << 13; // Rehash
+ h ^= h >>> 17;
+ h ^= h << 5;
+ }
+ else if (busy == 0 && cells == as && casBusy()) {
+ boolean init = false;
+ try { // Initialize table
+ if (cells == as) {
+ Cell[] rs = new Cell[2];
+ rs[h & 1] = new Cell(x);
+ cells = rs;
+ init = true;
+ }
+ } finally {
+ busy = 0;
+ }
+ if (init)
+ break;
+ }
+ else if (casBase(v = base, fn(v, x)))
+ break; // Fall back on using base
+ }
+ hc.code = h; // Record index for next time
+ }
+
+
+ /**
+ * Sets base and all cells to the given value.
+ */
+ final void internalReset(long initialValue) {
+ Cell[] as = cells;
+ base = initialValue;
+ if (as != null) {
+ int n = as.length;
+ for (int i = 0; i < n; ++i) {
+ Cell a = as[i];
+ if (a != null)
+ a.value = initialValue;
+ }
+ }
+ }
+
+ // Unsafe mechanics
+ private static final sun.misc.Unsafe UNSAFE;
+ private static final long baseOffset;
+ private static final long busyOffset;
+ static {
+ try {
+ UNSAFE = getUnsafe();
+ Class> sk = Striped64.class;
+ baseOffset = UNSAFE.objectFieldOffset
+ (sk.getDeclaredField("base"));
+ busyOffset = UNSAFE.objectFieldOffset
+ (sk.getDeclaredField("busy"));
+ } catch (Exception e) {
+ throw new Error(e);
+ }
+ }
+
+ /**
+ * 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() {
+ 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());
+ }
+ }
+ }
+
+}
diff --git a/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/ConcurrentHashMapV8.java b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/ConcurrentHashMapV8.java
new file mode 100644
index 0000000..b7fc5a9
--- /dev/null
+++ b/vendor/bundle/ruby/3.0.0/gems/concurrent-ruby-1.2.2/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/ConcurrentHashMapV8.java
@@ -0,0 +1,3800 @@
+/*
+ * 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/
+ */
+
+// This is based on the 1.79 version.
+
+package com.concurrent_ruby.ext.jsr166e.nounsafe;
+
+import org.jruby.RubyClass;
+import org.jruby.RubyNumeric;
+import org.jruby.RubyObject;
+import org.jruby.exceptions.RaiseException;
+import com.concurrent_ruby.ext.jsr166e.ConcurrentHashMap;
+import com.concurrent_ruby.ext.jsr166y.ThreadLocalRandom;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+
+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.util.concurrent.atomic.AtomicIntegerFieldUpdater;
+import java.util.concurrent.atomic.AtomicReferenceArray;
+import java.util.concurrent.locks.AbstractQueuedSynchronizer;
+
+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 not entail locking,
+ * and there is not 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.
+ *
+ * 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 completed update operations holding upon their
+ * onset. (More formally, an update operation for a given key bears a
+ * happens-before relation with any (non-null) retrieval for
+ * that key reporting the updated value.) 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 not 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.
+ *
+ *
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.
+ *
+ *
A {@link Set} projection of a ConcurrentHashMapV8 may be created
+ * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed
+ * (using {@link #keySet(Object)} when only keys are of interest, and the
+ * mapped values are (perhaps transiently) not used or all take the
+ * same mapping value.
+ *
+ *
A ConcurrentHashMapV8 can be used as scalable frequency map (a
+ * form of histogram or multiset) by using {@link LongAdder} values
+ * and initializing via {@link #computeIfAbsent}. For example, to add
+ * a count to a {@code ConcurrentHashMapV8 freqs}, you
+ * can use {@code freqs.computeIfAbsent(k -> new
+ * LongAdder()).increment();}
+ *
+ * This class and its views and iterators implement all of the
+ * optional methods of the {@link Map} and {@link Iterator}
+ * interfaces.
+ *
+ *
Like {@link Hashtable} but unlike {@link HashMap}, this class
+ * does not allow {@code null} to be used as a key or value.
+ *
+ *
ConcurrentHashMapV8s support parallel operations using the {@link
+ * ForkJoinPool#commonPool}. (Tasks that may be used in other contexts
+ * are available in class {@link ForkJoinTasks}). These operations are
+ * designed to be safely, and often sensibly, applied even with maps
+ * that are being concurrently updated by other threads; for example,
+ * when computing a snapshot summary of the values in a shared
+ * registry. There are three kinds of operation, each with four
+ * forms, accepting functions with Keys, Values, Entries, and (Key,
+ * Value) arguments and/or return values. (The first three forms are
+ * also available via the {@link #keySet()}, {@link #values()} and
+ * {@link #entrySet()} views). Because the elements of a
+ * ConcurrentHashMapV8 are not ordered in any particular way, and may be
+ * processed in different orders in different parallel executions, the
+ * correctness of supplied functions should not depend on any
+ * ordering, or on any other objects or values that may transiently
+ * change while computation is in progress; and except for forEach
+ * actions, should ideally be side-effect-free.
+ *
+ *
+ * - forEach: Perform a given action on each element.
+ * A variant form applies a given transformation on each element
+ * before performing the action.
+ *
+ * - search: Return the first available non-null result of
+ * applying a given function on each element; skipping further
+ * search when a result is found.
+ *
+ * - reduce: Accumulate each element. The supplied reduction
+ * function cannot rely on ordering (more formally, it should be
+ * both associative and commutative). There are five variants:
+ *
+ *
+ *
+ * - Plain reductions. (There is not a form of this method for
+ * (key, value) function arguments since there is no corresponding
+ * return type.)
+ *
+ * - Mapped reductions that accumulate the results of a given
+ * function applied to each element.
+ *
+ * - Reductions to scalar doubles, longs, and ints, using a
+ * given basis value.
+ *
+ *
+ *
+ *
+ *
+ * The concurrency properties of bulk operations follow
+ * from those of ConcurrentHashMapV8: Any non-null result returned
+ * from {@code get(key)} and related access methods bears a
+ * happens-before relation with the associated insertion or
+ * update. The result of any bulk operation reflects the
+ * composition of these per-element relations (but is not
+ * necessarily atomic with respect to the map as a whole unless it
+ * is somehow known to be quiescent). Conversely, because keys
+ * and values in the map are never null, null serves as a reliable
+ * atomic indicator of the current lack of any result. To
+ * maintain this property, null serves as an implicit basis for
+ * all non-scalar reduction operations. For the double, long, and
+ * int versions, the basis should be one that, when combined with
+ * any other value, returns that other value (more formally, it
+ * should be the identity element for the reduction). Most common
+ * reductions have these properties; for example, computing a sum
+ * with basis 0 or a minimum with basis MAX_VALUE.
+ *
+ *
Search and transformation functions provided as arguments
+ * should similarly return null to indicate the lack of any result
+ * (in which case it is not used). In the case of mapped
+ * reductions, this also enables transformations to serve as
+ * filters, returning null (or, in the case of primitive
+ * specializations, the identity basis) if the element should not
+ * be combined. You can create compound transformations and
+ * filterings by composing them yourself under this "null means
+ * there is nothing there now" rule before using them in search or
+ * reduce operations.
+ *
+ *
Methods accepting and/or returning Entry arguments maintain
+ * key-value associations. They may be useful for example when
+ * finding the key for the greatest value. Note that "plain" Entry
+ * arguments can be supplied using {@code new
+ * AbstractMap.SimpleEntry(k,v)}.
+ *
+ *
Bulk operations may complete abruptly, throwing an
+ * exception encountered in the application of a supplied
+ * function. Bear in mind when handling such exceptions that other
+ * concurrently executing functions could also have thrown
+ * exceptions, or would have done so if the first exception had
+ * not occurred.
+ *
+ *
Parallel speedups for bulk operations compared to sequential
+ * processing are common but not guaranteed. Operations involving
+ * brief functions on small maps may execute more slowly than
+ * sequential loops if the underlying work to parallelize the
+ * computation is more expensive than the computation itself.
+ * Similarly, parallelization may not lead to much actual parallelism
+ * if all processors are busy performing unrelated tasks.
+ *
+ *
All arguments to all task methods must be non-null.
+ *
+ *
jsr166e note: During transition, this class
+ * uses nested functional interfaces with different names but the
+ * same forms as those expected for JDK8.
+ *
+ *
This class is a member of the
+ *
+ * Java Collections Framework.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param the type of keys maintained by this map
+ * @param the type of mapped values
+ */
+public class ConcurrentHashMapV8
+ implements ConcurrentMap, Serializable, ConcurrentHashMap {
+ private static final long serialVersionUID = 7249069246763182397L;
+
+ /**
+ * A partitionable iterator. A Spliterator can be traversed
+ * directly, but can also be partitioned (before traversal) by
+ * creating another Spliterator that covers a non-overlapping
+ * portion of the elements, and so may be amenable to parallel
+ * execution.
+ *
+ * This interface exports a subset of expected JDK8
+ * functionality.
+ *
+ *
Sample usage: Here is one (of the several) ways to compute
+ * the sum of the values held in a map using the ForkJoin
+ * framework. As illustrated here, Spliterators are well suited to
+ * designs in which a task repeatedly splits off half its work
+ * into forked subtasks until small enough to process directly,
+ * and then joins these subtasks. Variants of this style can also
+ * be used in completion-based designs.
+ *
+ *
+ * {@code ConcurrentHashMapV8 m = ...
+ * // split as if have 8 * parallelism, for load balance
+ * int n = m.size();
+ * int p = aForkJoinPool.getParallelism() * 8;
+ * int split = (n < p)? n : p;
+ * long sum = aForkJoinPool.invoke(new SumValues(m.valueSpliterator(), split, null));
+ * // ...
+ * static class SumValues extends RecursiveTask {
+ * final Spliterator s;
+ * final int split; // split while > 1
+ * final SumValues nextJoin; // records forked subtasks to join
+ * SumValues(Spliterator s, int depth, SumValues nextJoin) {
+ * this.s = s; this.depth = depth; this.nextJoin = nextJoin;
+ * }
+ * public Long compute() {
+ * long sum = 0;
+ * SumValues subtasks = null; // fork subtasks
+ * for (int s = split >>> 1; s > 0; s >>>= 1)
+ * (subtasks = new SumValues(s.split(), s, subtasks)).fork();
+ * while (s.hasNext()) // directly process remaining elements
+ * sum += s.next();
+ * for (SumValues t = subtasks; t != null; t = t.nextJoin)
+ * sum += t.join(); // collect subtask results
+ * return sum;
+ * }
+ * }
+ * }
+ */
+ public static interface Spliterator extends Iterator {
+ /**
+ * Returns a Spliterator covering approximately half of the
+ * elements, guaranteed not to overlap with those subsequently
+ * returned by this Spliterator. After invoking this method,
+ * the current Spliterator will not produce any of
+ * the elements of the returned Spliterator, but the two
+ * Spliterators together will produce all of the elements that
+ * would have been produced by this Spliterator had this
+ * method not been called. The exact number of elements
+ * produced by the returned Spliterator is not guaranteed, and
+ * may be zero (i.e., with {@code hasNext()} reporting {@code
+ * false}) if this Spliterator cannot be further split.
+ *
+ * @return a Spliterator covering approximately half of the
+ * elements
+ * @throws IllegalStateException if this Spliterator has
+ * already commenced traversing elements
+ */
+ Spliterator split();
+ }
+
+
+ /*
+ * 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
+ * variants of put-related operations). The validation-based
+ * approach explained below leads to a lot of code sprawl because
+ * retry-control precludes factoring into smaller methods.
+ *
+ * The table is lazily initialized to a power-of-two size upon the
+ * first insertion. Each bin in the table normally 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 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 under most
+ * key/hash distributions. 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, under
+ * random hash codes, this is not a common problem. Ideally, 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 values are:
+ *
+ * 0: 0.60653066
+ * 1: 0.30326533
+ * 2: 0.07581633
+ * 3: 0.01263606
+ * 4: 0.00157952
+ * 5: 0.00015795
+ * 6: 0.00001316
+ * 7: 0.00000094
+ * 8: 0.00000006
+ * more: less than 1 in ten million
+ *
+ * Lock contention probability for two threads accessing distinct
+ * elements is roughly 1 / (8 * #elements) under random hashes.
+ *
+ * Actual hash code distributions encountered in practice
+ * sometimes deviate significantly from uniform randomness. This
+ * includes the case when N > (1<<30), so some keys MUST collide.
+ * Similarly for dumb or hostile usages in which multiple keys are
+ * designed to have identical hash codes. Also, although we guard
+ * against the worst effects of this (see method spread), sets of
+ * hashes may differ only in bits that do not impact their bin
+ * index for a given power-of-two mask. So we use a secondary
+ * strategy that applies when the number of nodes in a bin exceeds
+ * a threshold, and at least one of the keys implements
+ * Comparable. These TreeBins use a balanced tree to hold nodes
+ * (a specialized form of red-black trees), bounding search time
+ * to O(log N). Each search step in a TreeBin is around twice as
+ * slow as in a regular list, but given that N cannot exceed
+ * (1<<64) (before running out of addresses) this bounds search
+ * steps, lock hold times, etc, to reasonable constants (roughly
+ * 100 nodes inspected per operation worst case) so long as keys
+ * are Comparable (which is very common -- String, Long, etc).
+ * TreeBin nodes (TreeNodes) also maintain the same "next"
+ * traversal pointers as regular nodes, so can be traversed in
+ * iterators in the same way.
+ *
+ * The table is resized when occupancy exceeds a percentage
+ * 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 (unless it is a TreeBin). 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 Iter) 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 Traverser constructor)
+ * to support partitioned aggregate operations. 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;
+
+ /**
+ * The bin count threshold for using a tree rather than list for a
+ * bin. The value reflects the approximate break-even point for
+ * using tree-based operations.
+ * Note that Doug's version defaults to 8, but when dealing with
+ * Ruby objects it is actually beneficial to avoid TreeNodes
+ * as long as possible as it usually means going into Ruby land.
+ */
+ private static final int TREE_THRESHOLD = 16;
+
+ /*
+ * 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 AtomicReferenceArray table;
+
+ /**
+ * The counter maintaining number of elements.
+ */
+ private transient 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 KeySetView keySet;
+ private transient ValuesView values;
+ private transient EntrySetView entrySet;
+
+ /** For serialization compatibility. Null unless serialized; see below */
+ private Segment[] segments;
+
+ static AtomicIntegerFieldUpdater SIZE_CTRL_UPDATER = AtomicIntegerFieldUpdater.newUpdater(ConcurrentHashMapV8.class, "sizeCtl");
+
+ /* ---------------- 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(AtomicReferenceArray