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From sboi...@apache.org
Subject [07/15] incubator-ignite git commit: ignite-242 Jdk8 moved to core
Date Sat, 14 Feb 2015 16:53:02 GMT
http://git-wip-us.apache.org/repos/asf/incubator-ignite/blob/c1e649dc/modules/jdk8-backport/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java
----------------------------------------------------------------------
diff --git a/modules/jdk8-backport/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java b/modules/jdk8-backport/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java
deleted file mode 100644
index e944961..0000000
--- a/modules/jdk8-backport/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java
+++ /dev/null
@@ -1,3825 +0,0 @@
-/*
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.  Oracle designates this
- * particular file as subject to the "Classpath" exception as provided
- * by Oracle in the LICENSE file that accompanied this code.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-
-/*
- * This file is available under and governed by the GNU General Public
- * License version 2 only, as published by the Free Software Foundation.
- * However, the following notice accompanied the original version of this
- * file:
- *
- * 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/
- */
-
-/*
- * Copyright © 1993, 2013, Oracle and/or its affiliates.
- * All rights reserved.
- */
-
-package org.jdk8.backport;
-
-import java.io.*;
-import java.util.*;
-import java.util.concurrent.*;
-import java.util.concurrent.locks.*;
-
-/**
- * A hash table supporting full concurrency of retrievals and
- * high expected concurrency for updates. This class obeys the
- * same functional specification as {@link java.util.Hashtable}, and
- * includes versions of methods corresponding to each method of
- * {@code Hashtable}. However, even though all operations are
- * thread-safe, retrieval operations do <em>not</em> entail locking,
- * and there is <em>not</em> any support for locking the entire table
- * in a way that prevents all access.  This class is fully
- * interoperable with {@code Hashtable} in programs that rely on its
- * thread safety but not on its synchronization details.
- *
- * <p>Retrieval operations (including {@code get}) generally do not
- * block, so may overlap with update operations (including {@code put}
- * and {@code remove}). Retrievals reflect the results of the most
- * recently <em>completed</em> update operations holding upon their
- * onset. (More formally, an update operation for a given key bears a
- * <em>happens-before</em> 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 <em>not</em> throw {@link
- * ConcurrentModificationException}.  However, iterators are designed
- * to be used by only one thread at a time.  Bear in mind that the
- * results of aggregate status methods including {@code size}, {@code
- * isEmpty}, and {@code containsValue} are typically useful only when
- * a map is not undergoing concurrent updates in other threads.
- * Otherwise the results of these methods reflect transient states
- * that may be adequate for monitoring or estimation purposes, but not
- * for program control.
- *
- * <p>The table is dynamically expanded when there are too many
- * collisions (i.e., keys that have distinct hash codes but fall into
- * the same slot modulo the table size), with the expected average
- * effect of maintaining roughly two bins per mapping (corresponding
- * to a 0.75 load factor threshold for resizing). There may be much
- * variance around this average as mappings are added and removed, but
- * overall, this maintains a commonly accepted time/space tradeoff for
- * hash tables.  However, resizing this or any other kind of hash
- * table may be a relatively slow operation. When possible, it is a
- * good idea to provide a size estimate as an optional {@code
- * initialCapacity} constructor argument. An additional optional
- * {@code loadFactor} constructor argument provides a further means of
- * customizing initial table capacity by specifying the table density
- * to be used in calculating the amount of space to allocate for the
- * given number of elements.  Also, for compatibility with previous
- * versions of this class, constructors may optionally specify an
- * expected {@code concurrencyLevel} as an additional hint for
- * internal sizing.  Note that using many keys with exactly the same
- * {@code hashCode()} is a sure way to slow down performance of any
- * hash table.
- *
- * <p>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.
- *
- * <p>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<String,LongAdder> freqs}, you
- * can use {@code freqs.computeIfAbsent(k -> new
- * LongAdder()).increment();}
- *
- * <p>This class and its views and iterators implement all of the
- * <em>optional</em> methods of the {@link Map} and {@link Iterator}
- * interfaces.
- *
- * <p>Like {@link Hashtable} but unlike {@link HashMap}, this class
- * does <em>not</em> allow {@code null} to be used as a key or value.
- *
- * <ul>
- * <li> forEach: Perform a given action on each element.
- * A variant form applies a given transformation on each element
- * before performing the action.</li>
- *
- * <li> search: Return the first available non-null result of
- * applying a given function on each element; skipping further
- * search when a result is found.</li>
- *
- * <li> 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:
- *
- * <ul>
- *
- * <li> Plain reductions. (There is not a form of this method for
- * (key, value) function arguments since there is no corresponding
- * return type.)</li>
- *
- * <li> Mapped reductions that accumulate the results of a given
- * function applied to each element.</li>
- *
- * <li> Reductions to scalar doubles, longs, and ints, using a
- * given basis value.</li>
- *
- * </li>
- * </ul>
- * </ul>
- *
- * <p>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.
- *
- * <p>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.
- *
- * <p>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)}.
- *
- * <p>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.
- *
- * <p>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.
- *
- * <p>All arguments to all task methods must be non-null.
- *
- * <p><em>jsr166e note: During transition, this class
- * uses nested functional interfaces with different names but the
- * same forms as those expected for JDK8.</em>
- *
- * @since 1.5
- * @author Doug Lea
- * @param <K> the type of keys maintained by this map
- * @param <V> the type of mapped values
- */
-@SuppressWarnings("ALL")
-public class ConcurrentHashMap8<K, V>
-    implements ConcurrentMap<K, V>, Serializable {
-    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.
-     *
-     * <p>This interface exports a subset of expected JDK8
-     * functionality.
-     *
-     * <p>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.
-     *
-     * <pre>
-     * {@code ConcurrentHashMapV8<String, Long> 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<Long> {
-     *   final Spliterator<Long> s;
-     *   final int split;             // split while > 1
-     *   final SumValues nextJoin;    // records forked subtasks to join
-     *   SumValues(Spliterator<Long> 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;
-     *   }
-     * }
-     * }</pre>
-     */
-    public static interface Spliterator<T> extends Iterator<T> {
-        /**
-         * 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 <em>not</em> 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<T> 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.
-     */
-    private static final int TREE_THRESHOLD = 8;
-
-    /*
-     * 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<K,V> keySet;
-    private transient ValuesView<K,V> values;
-    private transient EntrySetView<K,V> entrySet;
-
-    /** For serialization compatibility. Null unless serialized; see below */
-    private Segment<K,V>[] 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<<ASHIFT)+ABASE);
-    }
-
-    private static final boolean casTabAt(Node[] tab, int i, Node c, Node v) {
-        return UNSAFE.compareAndSwapObject(tab, ((long)i<<ASHIFT)+ABASE, c, v);
-    }
-
-    private static final void setTabAt(Node[] tab, int i, Node v) {
-        UNSAFE.putObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE, v);
-    }
-
-    /* ---------------- Nodes -------------- */
-
-    /**
-     * Key-value entry. Note that this is never exported out as a
-     * user-visible Map.Entry (see MapEntry below). Nodes with a hash
-     * field of MOVED are special, and do not contain user keys or
-     * values.  Otherwise, keys are never null, and null val fields
-     * indicate that a node is in the process of being deleted or
-     * created. For purposes of read-only access, a key may be read
-     * before a val, but can only be used after checking val to be
-     * non-null.
-     */
-    static class Node {
-        volatile int hash;
-        final Object key;
-        volatile Object val;
-        volatile Node next;
-
-        Node(int hash, Object key, Object val, Node next) {
-            this.hash = hash;
-            this.key = key;
-            this.val = val;
-            this.next = next;
-        }
-
-        /** CompareAndSet the hash field */
-        final boolean casHash(int cmp, int val) {
-            return UNSAFE.compareAndSwapInt(this, hashOffset, cmp, val);
-        }
-
-        /** The number of spins before blocking for a lock */
-        static final int MAX_SPINS =
-            Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;
-
-        /**
-         * Spins a while if LOCKED bit set and this node is the first
-         * of its bin, and then sets WAITING bits on hash field and
-         * blocks (once) if they are still set.  It is OK for this
-         * method to return even if lock is not available upon exit,
-         * which enables these simple single-wait mechanics.
-         *
-         * The corresponding signalling operation is performed within
-         * callers: Upon detecting that WAITING has been set when
-         * unlocking lock (via a failed CAS from non-waiting LOCKED
-         * state), unlockers acquire the sync lock and perform a
-         * notifyAll.
-         *
-         * 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 = ThreadLocalRandom8.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) {
-                                    try {
-                                        Thread.currentThread().interrupt();
-                                    } catch (SecurityException ignore) {
-                                    }
-                                }
-                            }
-                            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<T>
-     * 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;
-            }
-        }
-
-        /**
-         * Returns the TreeNode (or null if not found) for the given key
-         * starting at given root.
-         */
-        @SuppressWarnings("unchecked") final TreeNode getTreeNode
-        (int h, Object k, TreeNode p) {
-            Class<?> c = k.getClass();
-            while (p != null) {
-                int dir, ph;  Object pk; Class<?> pc;
-                if ((ph = p.hash) == h) {
-                    if ((pk = p.key) == k || k.equals(pk))
-                        return p;
-                    if (c != (pc = pk.getClass()) ||
-                        !(k instanceof Comparable) ||
-                        (dir = ((Comparable)k).compareTo((Comparable)pk)) == 0) {
-                        dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
-                        TreeNode r = null, s = null, pl, pr;
-                        if (dir >= 0) {
-                            if ((pl = p.left) != null && h <= pl.hash)
-                                s = pl;
-                        }
-                        else if ((pr = p.right) != null && h >= pr.hash)
-                            s = pr;
-                        if (s != null && (r = getTreeNode(h, k, s)) != null)
-                            return r;
-                    }
-                }
-                else
-                    dir = (h < ph) ? -1 : 1;
-                p = (dir > 0) ? p.right : p.left;
-            }
-            return null;
-        }
-
-        /**
-         * 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;
-        }
-
-        /**
-         * Finds or adds a node.
-         * @return null if added
-         */
-        @SuppressWarnings("unchecked") final TreeNode putTreeNode
-        (int h, Object k, Object v) {
-            Class<?> c = k.getClass();
-            TreeNode pp = root, p = null;
-            int dir = 0;
-            while (pp != null) { // find existing node or leaf to insert at
-                int ph;  Object pk; Class<?> pc;
-                p = pp;
-                if ((ph = p.hash) == h) {
-                    if ((pk = p.key) == k || k.equals(pk))
-                        return p;
-                    if (c != (pc = pk.getClass()) ||
-                        !(k instanceof Comparable) ||
-                        (dir = ((Comparable)k).compareTo((Comparable)pk)) == 0) {
-                        dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
-                        TreeNode r = null, s = null, pl, pr;
-                        if (dir >= 0) {
-                            if ((pl = p.left) != null && h <= pl.hash)
-                                s = pl;
-                        }
-                        else if ((pr = p.right) != null && h >= pr.hash)
-                            s = pr;
-                        if (s != null && (r = getTreeNode(h, k, s)) != null)
-                            return r;
-                    }
-                }
-                else
-                    dir = (h < ph) ? -1 : 1;
-                pp = (dir > 0) ? p.right : p.left;
-            }
-
-            TreeNode f = first;
-            TreeNode x = first = new TreeNode(h, 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 = (p == null) ? null : 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, (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) {
-                                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.
-

<TRUNCATED>

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