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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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package jsr166e; |
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import jsr166e.LongAdder; |
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import java.util.Map; |
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import java.util.Set; |
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import java.util.Collection; |
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import java.util.AbstractMap; |
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import java.util.AbstractSet; |
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import java.util.AbstractCollection; |
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import java.util.Hashtable; |
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import java.util.HashMap; |
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import java.util.Iterator; |
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import java.util.Enumeration; |
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import java.util.ConcurrentModificationException; |
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import java.util.NoSuchElementException; |
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import java.util.concurrent.ConcurrentMap; |
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import java.io.Serializable; |
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|
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/** |
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* A hash table supporting full concurrency of retrievals and |
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* high expected concurrency for updates. This class obeys the |
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* same functional specification as {@link java.util.Hashtable}, and |
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* includes versions of methods corresponding to each method of |
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* {@code Hashtable}. However, even though all operations are |
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* thread-safe, retrieval operations do <em>not</em> entail locking, |
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* and there is <em>not</em> any support for locking the entire table |
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* in a way that prevents all access. This class is fully |
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* interoperable with {@code Hashtable} in programs that rely on its |
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* thread safety but not on its synchronization details. |
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* |
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* <p> Retrieval operations (including {@code get}) generally do not |
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* block, so may overlap with update operations (including {@code put} |
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* and {@code remove}). Retrievals reflect the results of the most |
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* recently <em>completed</em> update operations holding upon their |
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* onset. For aggregate operations such as {@code putAll} and {@code |
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* clear}, concurrent retrievals may reflect insertion or removal of |
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* only some entries. Similarly, Iterators and Enumerations return |
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* elements reflecting the state of the hash table at some point at or |
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* since the creation of the iterator/enumeration. They do |
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* <em>not</em> throw {@link ConcurrentModificationException}. |
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* However, iterators are designed to be used by only one thread at a |
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* time. Bear in mind that the results of aggregate status methods |
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* including {@code size}, {@code isEmpty}, and {@code containsValue} |
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* are typically useful only when a map is not undergoing concurrent |
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* updates in other threads. Otherwise the results of these methods |
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* reflect transient states that may be adequate for monitoring |
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* purposes, but not for program control. |
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* |
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* <p> Resizing this or any other kind of hash table is a relatively |
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* slow operation, so, when possible, it is a good idea to provide |
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* estimates of expected table sizes in constructors. Also, for |
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* compatibility with previous versions of this class, constructors |
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* may optionally specify an expected {@code concurrencyLevel} as an |
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* additional hint for internal sizing. |
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* |
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* <p>This class and its views and iterators implement all of the |
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* <em>optional</em> methods of the {@link Map} and {@link Iterator} |
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* interfaces. |
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* |
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* <p> Like {@link Hashtable} but unlike {@link HashMap}, this class |
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* does <em>not</em> allow {@code null} to be used as a key or value. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* <p><em>jsr166e note: This class is a candidate replacement for |
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* java.util.concurrent.ConcurrentHashMap.<em> |
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* |
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* @since 1.5 |
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* @author Doug Lea |
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* @param <K> the type of keys maintained by this map |
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* @param <V> the type of mapped values |
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*/ |
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public class ConcurrentHashMapV8<K, V> |
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implements ConcurrentMap<K, V>, Serializable { |
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private static final long serialVersionUID = 7249069246763182397L; |
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|
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/** |
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* A function computing a mapping from the given key to a value, |
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* or {@code null} if there is no mapping. This is a place-holder |
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* for an upcoming JDK8 interface. |
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*/ |
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public static interface MappingFunction<K, V> { |
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/** |
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* Returns a value for the given key, or null if there is no |
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* mapping. If this function throws an (unchecked) exception, |
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* the exception is rethrown to its caller, and no mapping is |
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* recorded. Because this function is invoked within |
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* atomicity control, the computation should be short and |
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* simple. The most common usage is to construct a new object |
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* serving as an initial mapped value. |
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* |
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* @param key the (non-null) key |
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* @return a value, or null if none |
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*/ |
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V map(K key); |
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} |
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|
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/* |
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* Overview: |
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* |
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* The primary design goal of this hash table is to maintain |
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* concurrent readability (typically method get(), but also |
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* iterators and related methods) while minimizing update |
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* contention. |
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* |
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* Each key-value mapping is held in a Node. Because Node fields |
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* can contain special values, they are defined using plain Object |
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* types. Similarly in turn, all internal methods that use them |
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* work off Object types. All public generic-typed methods relay |
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* in/out of these internal methods, supplying casts as needed. |
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* |
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* The table is lazily initialized to a power-of-two size upon the |
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* first insertion. Each bin in the table contains a (typically |
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* short) list of Nodes. Table accesses require volatile/atomic |
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* reads, writes, and CASes. Because there is no other way to |
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* arrange this without adding further indirections, we use |
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* intrinsics (sun.misc.Unsafe) operations. The lists of nodes |
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* within bins are always accurately traversable under volatile |
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* reads, so long as lookups check hash code and non-nullness of |
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* key and value before checking key equality. (All valid hash |
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* codes are nonnegative. Negative values are reserved for special |
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* forwarding nodes; see below.) |
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* |
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* A bin may be locked during update (insert, delete, and replace) |
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* operations. We do not want to waste the space required to |
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* associate a distinct lock object with each bin, so instead use |
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* the first node of a bin list itself as a lock, using builtin |
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* "synchronized" locks. These save space and we can live with |
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* only plain block-structured lock/unlock operations. Using the |
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* first node of a list as a lock does not by itself suffice |
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* though: When a node is locked, any update must first validate |
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* that it is still the first node, and retry if not. (Because new |
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* nodes are always appended to lists, once a node is first in a |
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* bin, it remains first until deleted or the bin becomes |
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* invalidated.) However, update operations can and usually do |
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* still traverse the bin until the point of update, which helps |
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* reduce cache misses on retries. This is a converse of sorts to |
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* the lazy locking technique described by Herlihy & Shavit. If |
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* there is no existing node during a put operation, then one can |
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* be CAS'ed in (without need for lock except in computeIfAbsent); |
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* the CAS serves as validation. This is on average the most |
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* common case for put operations -- under random hash codes, the |
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* distribution of nodes in bins follows a Poisson distribution |
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* (see http://en.wikipedia.org/wiki/Poisson_distribution) with a |
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* parameter of 0.5 on average under the default loadFactor of |
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* 0.75. The expected number of locks covering different elements |
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* (i.e., bins with 2 or more nodes) is approximately 10% at |
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* steady state under default settings. Lock contention |
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* probability for two threads accessing arbitrary distinct |
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* elements is, roughly, 1 / (8 * #elements). |
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* |
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* The table is resized when occupancy exceeds a threshold. Only |
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* a single thread performs the resize (using field "resizing", to |
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* arrange exclusion), but the table otherwise remains usable for |
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* both reads and updates. Resizing proceeds by transferring bins, |
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* one by one, from the table to the next table. Upon transfer, |
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* the old table bin contains only a special forwarding node (with |
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* negative hash code ("MOVED")) that contains the next table as |
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* its key. On encountering a forwarding node, access and update |
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* operations restart, using the new table. To ensure concurrent |
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* readability of traversals, transfers must proceed from the last |
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* bin (table.length - 1) up towards the first. Any traversal |
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* starting from the first bin can then arrange to move to the new |
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* table for the rest of the traversal without revisiting nodes. |
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* This constrains bin transfers to a particular order, and so can |
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* block indefinitely waiting for the next lock, and other threads |
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* cannot help with the transfer. However, expected stalls are |
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* infrequent enough to not warrant the additional overhead and |
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* complexity of access and iteration schemes that could admit |
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* out-of-order or concurrent bin transfers. |
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* |
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* A similar traversal scheme (not yet implemented) can apply to |
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* partial traversals during partitioned aggregate operations. |
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* Also, read-only operations give up if ever forwarded to a null |
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* table, which provides support for shutdown-style clearing, |
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* which is also not currently implemented. |
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* |
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* The element count is maintained using a LongAdder, which avoids |
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* contention on updates but can encounter cache thrashing if read |
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* too frequently during concurrent updates. To avoid reading so |
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* often, resizing is normally attempted only upon adding to a bin |
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* already holding two or more nodes. Under the default threshold |
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* (0.75), and uniform hash distributions, the probability of this |
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* occurring at threshold is around 13%, meaning that only about 1 |
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* in 8 puts check threshold (and after resizing, many fewer do |
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* so). But this approximation has high variance for small table |
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* sizes, so we check on any collision for sizes <= 64. Further, |
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* to increase the probability that a resize occurs soon enough, we |
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* offset the threshold (see THRESHOLD_OFFSET) by the expected |
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* number of puts between checks. This is currently set to 8, in |
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* accord with the default load factor. In practice, this is |
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* rarely overridden, and in any case is close enough to other |
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* plausible values not to waste dynamic probability computation |
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* for more precision. |
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*/ |
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|
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/* ---------------- Constants -------------- */ |
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|
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/** |
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* The smallest allowed table capacity. Must be a power of 2, at |
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* least 2. |
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*/ |
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static final int MINIMUM_CAPACITY = 2; |
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|
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/** |
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* The largest allowed table capacity. Must be a power of 2, at |
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* most 1<<30. |
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*/ |
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static final int MAXIMUM_CAPACITY = 1 << 30; |
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|
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/** |
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* The default initial table capacity. Must be a power of 2, at |
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* least MINIMUM_CAPACITY and at most MAXIMUM_CAPACITY |
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*/ |
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static final int DEFAULT_CAPACITY = 16; |
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|
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/** |
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* The default load factor for this table, used when not otherwise |
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* specified in a constructor. |
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*/ |
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static final float DEFAULT_LOAD_FACTOR = 0.75f; |
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|
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/** |
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* The default concurrency level for this table. Unused, but |
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* defined for compatibility with previous versions of this class. |
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*/ |
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static final int DEFAULT_CONCURRENCY_LEVEL = 16; |
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|
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/** |
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* The count value to offset thresholds to compensate for checking |
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* for resizing only when inserting into bins with two or more |
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* elements. See above for explanation. |
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*/ |
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static final int THRESHOLD_OFFSET = 8; |
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|
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/** |
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* Special node hash value indicating to use table in node.key |
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* Must be negative. |
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*/ |
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static final int MOVED = -1; |
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|
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/* ---------------- Fields -------------- */ |
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|
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/** |
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* The array of bins. Lazily initialized upon first insertion. |
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* Size is always a power of two. Accessed directly by inner |
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* classes. |
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*/ |
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transient volatile Node[] table; |
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|
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/** The counter maintaining number of elements. */ |
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private transient final LongAdder counter; |
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/** Nonzero when table is being initialized or resized. Updated via CAS. */ |
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private transient volatile int resizing; |
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/** The target load factor for the table. */ |
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private transient float loadFactor; |
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/** The next element count value upon which to resize the table. */ |
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private transient int threshold; |
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/** The initial capacity of the table. */ |
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private transient int initCap; |
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|
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// views |
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transient Set<K> keySet; |
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transient Set<Map.Entry<K,V>> entrySet; |
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transient Collection<V> values; |
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|
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/** For serialization compatibility. Null unless serialized; see below */ |
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Segment<K,V>[] segments; |
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|
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/** |
278 |
* Applies a supplemental hash function to a given hashCode, which |
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* defends against poor quality hash functions. The result must |
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* be non-negative, and for reasonable performance must have good |
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* avalanche properties; i.e., that each bit of the argument |
282 |
* affects each bit (except sign bit) of the result. |
283 |
*/ |
284 |
private static final int spread(int h) { |
285 |
// Apply base step of MurmurHash; see http://code.google.com/p/smhasher/ |
286 |
h ^= h >>> 16; |
287 |
h *= 0x85ebca6b; |
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h ^= h >>> 13; |
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h *= 0xc2b2ae35; |
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return (h >>> 16) ^ (h & 0x7fffffff); // mask out sign bit |
291 |
} |
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|
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/** |
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* Key-value entry. Note that this is never exported out as a |
295 |
* user-visible Map.Entry. |
296 |
*/ |
297 |
static final class Node { |
298 |
final int hash; |
299 |
final Object key; |
300 |
volatile Object val; |
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volatile Node next; |
302 |
|
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Node(int hash, Object key, Object val, Node next) { |
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this.hash = hash; |
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this.key = key; |
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this.val = val; |
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this.next = next; |
308 |
} |
309 |
} |
310 |
|
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/* |
312 |
* Volatile access methods are used for table elements as well as |
313 |
* elements of in-progress next table while resizing. Uses in |
314 |
* access and update methods are null checked by callers, and |
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* implicitly bounds-checked, relying on the invariants that tab |
316 |
* arrays have non-zero size, and all indices are masked with |
317 |
* (tab.length - 1) which is never negative and always less than |
318 |
* length. The "relaxed" non-volatile forms are used only during |
319 |
* table initialization. The only other usage is in |
320 |
* HashIterator.advance, which performs explicit checks. |
321 |
*/ |
322 |
|
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static final Node tabAt(Node[] tab, int i) { // used in HashIterator |
324 |
return (Node)UNSAFE.getObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE); |
325 |
} |
326 |
|
327 |
private static final boolean casTabAt(Node[] tab, int i, Node c, Node v) { |
328 |
return UNSAFE.compareAndSwapObject(tab, ((long)i<<ASHIFT)+ABASE, c, v); |
329 |
} |
330 |
|
331 |
private static final void setTabAt(Node[] tab, int i, Node v) { |
332 |
UNSAFE.putObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE, v); |
333 |
} |
334 |
|
335 |
private static final Node relaxedTabAt(Node[] tab, int i) { |
336 |
return (Node)UNSAFE.getObject(tab, ((long)i<<ASHIFT)+ABASE); |
337 |
} |
338 |
|
339 |
private static final void relaxedSetTabAt(Node[] tab, int i, Node v) { |
340 |
UNSAFE.putObject(tab, ((long)i<<ASHIFT)+ABASE, v); |
341 |
} |
342 |
|
343 |
/* ---------------- Access and update operations -------------- */ |
344 |
|
345 |
/** Implementation for get and containsKey **/ |
346 |
private final Object internalGet(Object k) { |
347 |
int h = spread(k.hashCode()); |
348 |
Node[] tab = table; |
349 |
retry: while (tab != null) { |
350 |
Node e = tabAt(tab, (tab.length - 1) & h); |
351 |
while (e != null) { |
352 |
int eh = e.hash; |
353 |
if (eh == h) { |
354 |
Object ek = e.key, ev = e.val; |
355 |
if (ev != null && ek != null && (k == ek || k.equals(ek))) |
356 |
return ev; |
357 |
} |
358 |
else if (eh < 0) { // bin was moved during resize |
359 |
tab = (Node[])e.key; |
360 |
continue retry; |
361 |
} |
362 |
e = e.next; |
363 |
} |
364 |
break; |
365 |
} |
366 |
return null; |
367 |
} |
368 |
|
369 |
/** Implementation for put and putIfAbsent **/ |
370 |
private final Object internalPut(Object k, Object v, boolean replace) { |
371 |
int h = spread(k.hashCode()); |
372 |
Object oldVal = null; // the previous value or null if none |
373 |
Node[] tab = table; |
374 |
for (;;) { |
375 |
Node e; int i; |
376 |
if (tab == null) |
377 |
tab = grow(0); |
378 |
else if ((e = tabAt(tab, i = (tab.length - 1) & h)) == null) { |
379 |
if (casTabAt(tab, i, null, new Node(h, k, v, null))) |
380 |
break; |
381 |
} |
382 |
else if (e.hash < 0) |
383 |
tab = (Node[])e.key; |
384 |
else { |
385 |
boolean validated = false; |
386 |
boolean checkSize = false; |
387 |
synchronized (e) { |
388 |
Node first = e; |
389 |
for (;;) { |
390 |
Object ek, ev; |
391 |
if ((ev = e.val) == null) |
392 |
break; |
393 |
if (e.hash == h && (ek = e.key) != null && |
394 |
(k == ek || k.equals(ek))) { |
395 |
if (tabAt(tab, i) == first) { |
396 |
validated = true; |
397 |
oldVal = ev; |
398 |
if (replace) |
399 |
e.val = v; |
400 |
} |
401 |
break; |
402 |
} |
403 |
Node last = e; |
404 |
if ((e = e.next) == null) { |
405 |
if (tabAt(tab, i) == first) { |
406 |
validated = true; |
407 |
last.next = new Node(h, k, v, null); |
408 |
if (last != first || tab.length <= 64) |
409 |
checkSize = true; |
410 |
} |
411 |
break; |
412 |
} |
413 |
} |
414 |
} |
415 |
if (validated) { |
416 |
if (checkSize && tab.length < MAXIMUM_CAPACITY && |
417 |
resizing == 0 && counter.sum() >= threshold) |
418 |
grow(0); |
419 |
break; |
420 |
} |
421 |
} |
422 |
} |
423 |
if (oldVal == null) |
424 |
counter.increment(); |
425 |
return oldVal; |
426 |
} |
427 |
|
428 |
/** |
429 |
* Covers the four public remove/replace methods: Replaces node |
430 |
* value with v, conditional upon match of cv if non-null. If |
431 |
* resulting value is null, delete. |
432 |
*/ |
433 |
private final Object internalReplace(Object k, Object v, Object cv) { |
434 |
int h = spread(k.hashCode()); |
435 |
Object oldVal = null; |
436 |
Node e; int i; |
437 |
Node[] tab = table; |
438 |
while (tab != null && |
439 |
(e = tabAt(tab, i = (tab.length - 1) & h)) != null) { |
440 |
if (e.hash < 0) |
441 |
tab = (Node[])e.key; |
442 |
else { |
443 |
boolean validated = false; |
444 |
boolean deleted = false; |
445 |
synchronized (e) { |
446 |
Node pred = null; |
447 |
Node first = e; |
448 |
for (;;) { |
449 |
Object ek, ev; |
450 |
if ((ev = e.val) == null) |
451 |
break; |
452 |
if (e.hash == h && (ek = e.key) != null && |
453 |
(k == ek || k.equals(ek))) { |
454 |
if (tabAt(tab, i) == first) { |
455 |
validated = true; |
456 |
if (cv == null || cv == ev || cv.equals(ev)) { |
457 |
oldVal = ev; |
458 |
if ((e.val = v) == null) { |
459 |
deleted = true; |
460 |
Node en = e.next; |
461 |
if (pred != null) |
462 |
pred.next = en; |
463 |
else |
464 |
setTabAt(tab, i, en); |
465 |
} |
466 |
} |
467 |
} |
468 |
break; |
469 |
} |
470 |
pred = e; |
471 |
if ((e = e.next) == null) { |
472 |
if (tabAt(tab, i) == first) |
473 |
validated = true; |
474 |
break; |
475 |
} |
476 |
} |
477 |
} |
478 |
if (validated) { |
479 |
if (deleted) |
480 |
counter.decrement(); |
481 |
break; |
482 |
} |
483 |
} |
484 |
} |
485 |
return oldVal; |
486 |
} |
487 |
|
488 |
/** Implementation for computeIfAbsent and compute */ |
489 |
@SuppressWarnings("unchecked") |
490 |
private final V internalCompute(K k, |
491 |
MappingFunction<? super K, ? extends V> f, |
492 |
boolean replace) { |
493 |
int h = spread(k.hashCode()); |
494 |
V val = null; |
495 |
boolean added = false; |
496 |
boolean validated = false; |
497 |
Node[] tab = table; |
498 |
do { |
499 |
Node e; int i; |
500 |
if (tab == null) |
501 |
tab = grow(0); |
502 |
else if ((e = tabAt(tab, i = (tab.length - 1) & h)) == null) { |
503 |
Node node = new Node(h, k, null, null); |
504 |
synchronized (node) { |
505 |
if (casTabAt(tab, i, null, node)) { |
506 |
validated = true; |
507 |
try { |
508 |
val = f.map(k); |
509 |
if (val != null) { |
510 |
node.val = val; |
511 |
added = true; |
512 |
} |
513 |
} finally { |
514 |
if (!added) |
515 |
setTabAt(tab, i, null); |
516 |
} |
517 |
} |
518 |
} |
519 |
} |
520 |
else if (e.hash < 0) |
521 |
tab = (Node[])e.key; |
522 |
else if (Thread.holdsLock(e)) |
523 |
throw new IllegalStateException("Recursive map computation"); |
524 |
else { |
525 |
boolean checkSize = false; |
526 |
synchronized (e) { |
527 |
Node first = e; |
528 |
for (;;) { |
529 |
Object ek, ev; |
530 |
if ((ev = e.val) == null) |
531 |
break; |
532 |
if (e.hash == h && (ek = e.key) != null && |
533 |
(k == ek || k.equals(ek))) { |
534 |
if (tabAt(tab, i) == first) { |
535 |
validated = true; |
536 |
if (replace && (ev = f.map(k)) != null) |
537 |
e.val = ev; |
538 |
val = (V)ev; |
539 |
} |
540 |
break; |
541 |
} |
542 |
Node last = e; |
543 |
if ((e = e.next) == null) { |
544 |
if (tabAt(tab, i) == first) { |
545 |
validated = true; |
546 |
if ((val = f.map(k)) != null) { |
547 |
last.next = new Node(h, k, val, null); |
548 |
added = true; |
549 |
if (last != first || tab.length <= 64) |
550 |
checkSize = true; |
551 |
} |
552 |
} |
553 |
break; |
554 |
} |
555 |
} |
556 |
} |
557 |
if (checkSize && tab.length < MAXIMUM_CAPACITY && |
558 |
resizing == 0 && counter.sum() >= threshold) |
559 |
grow(0); |
560 |
} |
561 |
} while (!validated); |
562 |
if (added) |
563 |
counter.increment(); |
564 |
return val; |
565 |
} |
566 |
|
567 |
/* |
568 |
* Reclassifies nodes in each bin to new table. Because we are |
569 |
* using power-of-two expansion, the elements from each bin must |
570 |
* either stay at same index, or move with a power of two |
571 |
* offset. We eliminate unnecessary node creation by catching |
572 |
* cases where old nodes can be reused because their next fields |
573 |
* won't change. Statistically, at the default threshold, only |
574 |
* about one-sixth of them need cloning when a table doubles. The |
575 |
* nodes they replace will be garbage collectable as soon as they |
576 |
* are no longer referenced by any reader thread that may be in |
577 |
* the midst of concurrently traversing table. |
578 |
* |
579 |
* Transfers are done from the bottom up to preserve iterator |
580 |
* traversability. On each step, the old bin is locked, |
581 |
* moved/copied, and then replaced with a forwarding node. |
582 |
*/ |
583 |
private static final void transfer(Node[] tab, Node[] nextTab) { |
584 |
int n = tab.length; |
585 |
int mask = nextTab.length - 1; |
586 |
Node fwd = new Node(MOVED, nextTab, null, null); |
587 |
for (int i = n - 1; i >= 0; --i) { |
588 |
for (Node e;;) { |
589 |
if ((e = tabAt(tab, i)) == null) { |
590 |
if (casTabAt(tab, i, e, fwd)) |
591 |
break; |
592 |
} |
593 |
else { |
594 |
boolean validated = false; |
595 |
synchronized (e) { |
596 |
int idx = e.hash & mask; |
597 |
Node lastRun = e; |
598 |
for (Node p = e.next; p != null; p = p.next) { |
599 |
int j = p.hash & mask; |
600 |
if (j != idx) { |
601 |
idx = j; |
602 |
lastRun = p; |
603 |
} |
604 |
} |
605 |
if (tabAt(tab, i) == e) { |
606 |
validated = true; |
607 |
relaxedSetTabAt(nextTab, idx, lastRun); |
608 |
for (Node p = e; p != lastRun; p = p.next) { |
609 |
int h = p.hash; |
610 |
int j = h & mask; |
611 |
Node r = relaxedTabAt(nextTab, j); |
612 |
relaxedSetTabAt(nextTab, j, |
613 |
new Node(h, p.key, p.val, r)); |
614 |
} |
615 |
setTabAt(tab, i, fwd); |
616 |
} |
617 |
} |
618 |
if (validated) |
619 |
break; |
620 |
} |
621 |
} |
622 |
} |
623 |
} |
624 |
|
625 |
/** |
626 |
* If not already resizing, initializes or creates next table and |
627 |
* transfers bins. Rechecks occupancy after a transfer to see if |
628 |
* another resize is already needed because resizings are lagging |
629 |
* additions. |
630 |
* |
631 |
* @param sizeHint overridden capacity target (nonzero only from putAll) |
632 |
* @return current table |
633 |
*/ |
634 |
private final Node[] grow(int sizeHint) { |
635 |
if (resizing == 0 && |
636 |
UNSAFE.compareAndSwapInt(this, resizingOffset, 0, 1)) { |
637 |
try { |
638 |
for (;;) { |
639 |
int cap, n; |
640 |
Node[] tab = table; |
641 |
if (tab == null) { |
642 |
int c = initCap; |
643 |
if (c < sizeHint) |
644 |
c = sizeHint; |
645 |
if (c == DEFAULT_CAPACITY) |
646 |
cap = c; |
647 |
else if (c >= MAXIMUM_CAPACITY) |
648 |
cap = MAXIMUM_CAPACITY; |
649 |
else { |
650 |
cap = MINIMUM_CAPACITY; |
651 |
while (cap < c) |
652 |
cap <<= 1; |
653 |
} |
654 |
} |
655 |
else if ((n = tab.length) < MAXIMUM_CAPACITY && |
656 |
(sizeHint <= 0 || n < sizeHint)) |
657 |
cap = n << 1; |
658 |
else |
659 |
break; |
660 |
threshold = (int)(cap * loadFactor) - THRESHOLD_OFFSET; |
661 |
Node[] nextTab = new Node[cap]; |
662 |
if (tab != null) |
663 |
transfer(tab, nextTab); |
664 |
table = nextTab; |
665 |
if (tab == null || cap >= MAXIMUM_CAPACITY || |
666 |
(sizeHint > 0 && cap >= sizeHint) || |
667 |
counter.sum() < threshold) |
668 |
break; |
669 |
} |
670 |
} finally { |
671 |
resizing = 0; |
672 |
} |
673 |
} |
674 |
else if (table == null) |
675 |
Thread.yield(); // lost initialization race; just spin |
676 |
return table; |
677 |
} |
678 |
|
679 |
/** |
680 |
* Implementation for putAll and constructor with Map |
681 |
* argument. Tries to first override initial capacity or grow |
682 |
* based on map size to pre-allocate table space. |
683 |
*/ |
684 |
private final void internalPutAll(Map<? extends K, ? extends V> m) { |
685 |
int s = m.size(); |
686 |
grow((s >= (MAXIMUM_CAPACITY >>> 1)) ? s : s + (s >>> 1)); |
687 |
for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) { |
688 |
Object k = e.getKey(); |
689 |
Object v = e.getValue(); |
690 |
if (k == null || v == null) |
691 |
throw new NullPointerException(); |
692 |
internalPut(k, v, true); |
693 |
} |
694 |
} |
695 |
|
696 |
/** |
697 |
* Implementation for clear. Steps through each bin, removing all nodes. |
698 |
*/ |
699 |
private final void internalClear() { |
700 |
long deletions = 0L; |
701 |
int i = 0; |
702 |
Node[] tab = table; |
703 |
while (tab != null && i < tab.length) { |
704 |
Node e = tabAt(tab, i); |
705 |
if (e == null) |
706 |
++i; |
707 |
else if (e.hash < 0) |
708 |
tab = (Node[])e.key; |
709 |
else { |
710 |
boolean validated = false; |
711 |
synchronized (e) { |
712 |
if (tabAt(tab, i) == e) { |
713 |
validated = true; |
714 |
do { |
715 |
if (e.val != null) { |
716 |
e.val = null; |
717 |
++deletions; |
718 |
} |
719 |
} while ((e = e.next) != null); |
720 |
setTabAt(tab, i, null); |
721 |
} |
722 |
} |
723 |
if (validated) { |
724 |
++i; |
725 |
if (deletions > THRESHOLD_OFFSET) { // bound lag in counts |
726 |
counter.add(-deletions); |
727 |
deletions = 0L; |
728 |
} |
729 |
} |
730 |
} |
731 |
} |
732 |
if (deletions != 0L) |
733 |
counter.add(-deletions); |
734 |
} |
735 |
|
736 |
/** |
737 |
* Base class for key, value, and entry iterators, plus internal |
738 |
* implementations of public traversal-based methods, to avoid |
739 |
* duplicating traversal code. |
740 |
*/ |
741 |
class HashIterator { |
742 |
private Node next; // the next entry to return |
743 |
private Node[] tab; // current table; updated if resized |
744 |
private Node lastReturned; // the last entry returned, for remove |
745 |
private Object nextVal; // cached value of next |
746 |
private int index; // index of bin to use next |
747 |
private int baseIndex; // current index of initial table |
748 |
private final int baseSize; // initial table size |
749 |
|
750 |
HashIterator() { |
751 |
Node[] t = tab = table; |
752 |
if (t == null) |
753 |
baseSize = 0; |
754 |
else { |
755 |
baseSize = t.length; |
756 |
advance(null); |
757 |
} |
758 |
} |
759 |
|
760 |
public final boolean hasNext() { return next != null; } |
761 |
public final boolean hasMoreElements() { return next != null; } |
762 |
|
763 |
/** |
764 |
* Advances next. Normally, iteration proceeds bin-by-bin |
765 |
* traversing lists. However, if the table has been resized, |
766 |
* then all future steps must traverse both the bin at the |
767 |
* current index as well as at (index + baseSize); and so on |
768 |
* for further resizings. To paranoically cope with potential |
769 |
* (improper) sharing of iterators across threads, table reads |
770 |
* are bounds-checked. |
771 |
*/ |
772 |
final void advance(Node e) { |
773 |
for (;;) { |
774 |
Node[] t; int i; // for bounds checks |
775 |
if (e != null) { |
776 |
Object ek = e.key, ev = e.val; |
777 |
if (ev != null && ek != null) { |
778 |
nextVal = ev; |
779 |
next = e; |
780 |
break; |
781 |
} |
782 |
e = e.next; |
783 |
} |
784 |
else if (baseIndex < baseSize && (t = tab) != null && |
785 |
t.length > (i = index) && i >= 0) { |
786 |
if ((e = tabAt(t, i)) != null && e.hash < 0) { |
787 |
tab = (Node[])e.key; |
788 |
e = null; |
789 |
} |
790 |
else if (i + baseSize < t.length) |
791 |
index += baseSize; // visit forwarded upper slots |
792 |
else |
793 |
index = ++baseIndex; |
794 |
} |
795 |
else { |
796 |
next = null; |
797 |
break; |
798 |
} |
799 |
} |
800 |
} |
801 |
|
802 |
final Object nextKey() { |
803 |
Node e = next; |
804 |
if (e == null) |
805 |
throw new NoSuchElementException(); |
806 |
Object k = e.key; |
807 |
advance((lastReturned = e).next); |
808 |
return k; |
809 |
} |
810 |
|
811 |
final Object nextValue() { |
812 |
Node e = next; |
813 |
if (e == null) |
814 |
throw new NoSuchElementException(); |
815 |
Object v = nextVal; |
816 |
advance((lastReturned = e).next); |
817 |
return v; |
818 |
} |
819 |
|
820 |
final WriteThroughEntry nextEntry() { |
821 |
Node e = next; |
822 |
if (e == null) |
823 |
throw new NoSuchElementException(); |
824 |
WriteThroughEntry entry = |
825 |
new WriteThroughEntry(e.key, nextVal); |
826 |
advance((lastReturned = e).next); |
827 |
return entry; |
828 |
} |
829 |
|
830 |
public final void remove() { |
831 |
if (lastReturned == null) |
832 |
throw new IllegalStateException(); |
833 |
ConcurrentHashMapV8.this.remove(lastReturned.key); |
834 |
lastReturned = null; |
835 |
} |
836 |
|
837 |
/** Helper for serialization */ |
838 |
final void writeEntries(java.io.ObjectOutputStream s) |
839 |
throws java.io.IOException { |
840 |
Node e; |
841 |
while ((e = next) != null) { |
842 |
s.writeObject(e.key); |
843 |
s.writeObject(nextVal); |
844 |
advance(e.next); |
845 |
} |
846 |
} |
847 |
|
848 |
/** Helper for containsValue */ |
849 |
final boolean containsVal(Object value) { |
850 |
if (value != null) { |
851 |
Node e; |
852 |
while ((e = next) != null) { |
853 |
Object v = nextVal; |
854 |
if (value == v || value.equals(v)) |
855 |
return true; |
856 |
advance(e.next); |
857 |
} |
858 |
} |
859 |
return false; |
860 |
} |
861 |
|
862 |
/** Helper for Map.hashCode */ |
863 |
final int mapHashCode() { |
864 |
int h = 0; |
865 |
Node e; |
866 |
while ((e = next) != null) { |
867 |
h += e.key.hashCode() ^ nextVal.hashCode(); |
868 |
advance(e.next); |
869 |
} |
870 |
return h; |
871 |
} |
872 |
|
873 |
/** Helper for Map.toString */ |
874 |
final String mapToString() { |
875 |
Node e = next; |
876 |
if (e == null) |
877 |
return "{}"; |
878 |
StringBuilder sb = new StringBuilder(); |
879 |
sb.append('{'); |
880 |
for (;;) { |
881 |
sb.append(e.key == this ? "(this Map)" : e.key); |
882 |
sb.append('='); |
883 |
sb.append(nextVal == this ? "(this Map)" : nextVal); |
884 |
advance(e.next); |
885 |
if ((e = next) != null) |
886 |
sb.append(',').append(' '); |
887 |
else |
888 |
return sb.append('}').toString(); |
889 |
} |
890 |
} |
891 |
} |
892 |
|
893 |
/* ---------------- Public operations -------------- */ |
894 |
|
895 |
/** |
896 |
* Creates a new, empty map with the specified initial |
897 |
* capacity, load factor and concurrency level. |
898 |
* |
899 |
* @param initialCapacity the initial capacity. The implementation |
900 |
* performs internal sizing to accommodate this many elements. |
901 |
* @param loadFactor the load factor threshold, used to control resizing. |
902 |
* Resizing may be performed when the average number of elements per |
903 |
* bin exceeds this threshold. |
904 |
* @param concurrencyLevel the estimated number of concurrently |
905 |
* updating threads. The implementation may use this value as |
906 |
* a sizing hint. |
907 |
* @throws IllegalArgumentException if the initial capacity is |
908 |
* negative or the load factor or concurrencyLevel are |
909 |
* nonpositive. |
910 |
*/ |
911 |
public ConcurrentHashMapV8(int initialCapacity, |
912 |
float loadFactor, int concurrencyLevel) { |
913 |
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0) |
914 |
throw new IllegalArgumentException(); |
915 |
this.initCap = initialCapacity; |
916 |
this.loadFactor = loadFactor; |
917 |
this.counter = new LongAdder(); |
918 |
} |
919 |
|
920 |
/** |
921 |
* Creates a new, empty map with the specified initial capacity |
922 |
* and load factor and with the default concurrencyLevel (16). |
923 |
* |
924 |
* @param initialCapacity The implementation performs internal |
925 |
* sizing to accommodate this many elements. |
926 |
* @param loadFactor the load factor threshold, used to control resizing. |
927 |
* Resizing may be performed when the average number of elements per |
928 |
* bin exceeds this threshold. |
929 |
* @throws IllegalArgumentException if the initial capacity of |
930 |
* elements is negative or the load factor is nonpositive |
931 |
* |
932 |
* @since 1.6 |
933 |
*/ |
934 |
public ConcurrentHashMapV8(int initialCapacity, float loadFactor) { |
935 |
this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL); |
936 |
} |
937 |
|
938 |
/** |
939 |
* Creates a new, empty map with the specified initial capacity, |
940 |
* and with default load factor (0.75) and concurrencyLevel (16). |
941 |
* |
942 |
* @param initialCapacity the initial capacity. The implementation |
943 |
* performs internal sizing to accommodate this many elements. |
944 |
* @throws IllegalArgumentException if the initial capacity of |
945 |
* elements is negative. |
946 |
*/ |
947 |
public ConcurrentHashMapV8(int initialCapacity) { |
948 |
this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
949 |
} |
950 |
|
951 |
/** |
952 |
* Creates a new, empty map with a default initial capacity (16), |
953 |
* load factor (0.75) and concurrencyLevel (16). |
954 |
*/ |
955 |
public ConcurrentHashMapV8() { |
956 |
this(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
957 |
} |
958 |
|
959 |
/** |
960 |
* Creates a new map with the same mappings as the given map. |
961 |
* The map is created with a capacity of 1.5 times the number |
962 |
* of mappings in the given map or 16 (whichever is greater), |
963 |
* and a default load factor (0.75) and concurrencyLevel (16). |
964 |
* |
965 |
* @param m the map |
966 |
*/ |
967 |
public ConcurrentHashMapV8(Map<? extends K, ? extends V> m) { |
968 |
this(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
969 |
if (m == null) |
970 |
throw new NullPointerException(); |
971 |
internalPutAll(m); |
972 |
} |
973 |
|
974 |
/** |
975 |
* Returns {@code true} if this map contains no key-value mappings. |
976 |
* |
977 |
* @return {@code true} if this map contains no key-value mappings |
978 |
*/ |
979 |
public boolean isEmpty() { |
980 |
return counter.sum() <= 0L; // ignore transient negative values |
981 |
} |
982 |
|
983 |
/** |
984 |
* Returns the number of key-value mappings in this map. If the |
985 |
* map contains more than {@code Integer.MAX_VALUE} elements, returns |
986 |
* {@code Integer.MAX_VALUE}. |
987 |
* |
988 |
* @return the number of key-value mappings in this map |
989 |
*/ |
990 |
public int size() { |
991 |
long n = counter.sum(); |
992 |
return ((n >>> 31) == 0) ? (int)n : (n < 0L) ? 0 : Integer.MAX_VALUE; |
993 |
} |
994 |
|
995 |
/** |
996 |
* Returns the value to which the specified key is mapped, |
997 |
* or {@code null} if this map contains no mapping for the key. |
998 |
* |
999 |
* <p>More formally, if this map contains a mapping from a key |
1000 |
* {@code k} to a value {@code v} such that {@code key.equals(k)}, |
1001 |
* then this method returns {@code v}; otherwise it returns |
1002 |
* {@code null}. (There can be at most one such mapping.) |
1003 |
* |
1004 |
* @throws NullPointerException if the specified key is null |
1005 |
*/ |
1006 |
@SuppressWarnings("unchecked") |
1007 |
public V get(Object key) { |
1008 |
if (key == null) |
1009 |
throw new NullPointerException(); |
1010 |
return (V)internalGet(key); |
1011 |
} |
1012 |
|
1013 |
/** |
1014 |
* Tests if the specified object is a key in this table. |
1015 |
* |
1016 |
* @param key possible key |
1017 |
* @return {@code true} if and only if the specified object |
1018 |
* is a key in this table, as determined by the |
1019 |
* {@code equals} method; {@code false} otherwise. |
1020 |
* @throws NullPointerException if the specified key is null |
1021 |
*/ |
1022 |
public boolean containsKey(Object key) { |
1023 |
if (key == null) |
1024 |
throw new NullPointerException(); |
1025 |
return internalGet(key) != null; |
1026 |
} |
1027 |
|
1028 |
/** |
1029 |
* Returns {@code true} if this map maps one or more keys to the |
1030 |
* specified value. Note: This method requires a full internal |
1031 |
* traversal of the hash table, and so is much slower than |
1032 |
* method {@code containsKey}. |
1033 |
* |
1034 |
* @param value value whose presence in this map is to be tested |
1035 |
* @return {@code true} if this map maps one or more keys to the |
1036 |
* specified value |
1037 |
* @throws NullPointerException if the specified value is null |
1038 |
*/ |
1039 |
public boolean containsValue(Object value) { |
1040 |
if (value == null) |
1041 |
throw new NullPointerException(); |
1042 |
return new HashIterator().containsVal(value); |
1043 |
} |
1044 |
|
1045 |
/** |
1046 |
* Legacy method testing if some key maps into the specified value |
1047 |
* in this table. This method is identical in functionality to |
1048 |
* {@link #containsValue}, and exists solely to ensure |
1049 |
* full compatibility with class {@link java.util.Hashtable}, |
1050 |
* which supported this method prior to introduction of the |
1051 |
* Java Collections framework. |
1052 |
* |
1053 |
* @param value a value to search for |
1054 |
* @return {@code true} if and only if some key maps to the |
1055 |
* {@code value} argument in this table as |
1056 |
* determined by the {@code equals} method; |
1057 |
* {@code false} otherwise |
1058 |
* @throws NullPointerException if the specified value is null |
1059 |
*/ |
1060 |
public boolean contains(Object value) { |
1061 |
return containsValue(value); |
1062 |
} |
1063 |
|
1064 |
/** |
1065 |
* Maps the specified key to the specified value in this table. |
1066 |
* Neither the key nor the value can be null. |
1067 |
* |
1068 |
* <p> The value can be retrieved by calling the {@code get} method |
1069 |
* with a key that is equal to the original key. |
1070 |
* |
1071 |
* @param key key with which the specified value is to be associated |
1072 |
* @param value value to be associated with the specified key |
1073 |
* @return the previous value associated with {@code key}, or |
1074 |
* {@code null} if there was no mapping for {@code key} |
1075 |
* @throws NullPointerException if the specified key or value is null |
1076 |
*/ |
1077 |
@SuppressWarnings("unchecked") |
1078 |
public V put(K key, V value) { |
1079 |
if (key == null || value == null) |
1080 |
throw new NullPointerException(); |
1081 |
return (V)internalPut(key, value, true); |
1082 |
} |
1083 |
|
1084 |
/** |
1085 |
* {@inheritDoc} |
1086 |
* |
1087 |
* @return the previous value associated with the specified key, |
1088 |
* or {@code null} if there was no mapping for the key |
1089 |
* @throws NullPointerException if the specified key or value is null |
1090 |
*/ |
1091 |
@SuppressWarnings("unchecked") |
1092 |
public V putIfAbsent(K key, V value) { |
1093 |
if (key == null || value == null) |
1094 |
throw new NullPointerException(); |
1095 |
return (V)internalPut(key, value, false); |
1096 |
} |
1097 |
|
1098 |
/** |
1099 |
* Copies all of the mappings from the specified map to this one. |
1100 |
* These mappings replace any mappings that this map had for any of the |
1101 |
* keys currently in the specified map. |
1102 |
* |
1103 |
* @param m mappings to be stored in this map |
1104 |
*/ |
1105 |
public void putAll(Map<? extends K, ? extends V> m) { |
1106 |
if (m == null) |
1107 |
throw new NullPointerException(); |
1108 |
internalPutAll(m); |
1109 |
} |
1110 |
|
1111 |
/** |
1112 |
* If the specified key is not already associated with a value, |
1113 |
* computes its value using the given mappingFunction, and if |
1114 |
* non-null, enters it into the map. This is equivalent to |
1115 |
* |
1116 |
* <pre> |
1117 |
* if (map.containsKey(key)) |
1118 |
* return map.get(key); |
1119 |
* value = mappingFunction.map(key); |
1120 |
* if (value != null) |
1121 |
* map.put(key, value); |
1122 |
* return value; |
1123 |
* </pre> |
1124 |
* |
1125 |
* except that the action is performed atomically. Some attempted |
1126 |
* update operations on this map by other threads may be blocked |
1127 |
* while computation is in progress, so the computation should be |
1128 |
* short and simple, and must not attempt to update any other |
1129 |
* mappings of this Map. The most appropriate usage is to |
1130 |
* construct a new object serving as an initial mapped value, or |
1131 |
* memoized result, as in: |
1132 |
* <pre>{@code |
1133 |
* map.computeIfAbsent(key, new MappingFunction<K, V>() { |
1134 |
* public V map(K k) { return new Value(f(k)); }}; |
1135 |
* }</pre> |
1136 |
* |
1137 |
* @param key key with which the specified value is to be associated |
1138 |
* @param mappingFunction the function to compute a value |
1139 |
* @return the current (existing or computed) value associated with |
1140 |
* the specified key, or {@code null} if the computation |
1141 |
* returned {@code null}. |
1142 |
* @throws NullPointerException if the specified key or mappingFunction |
1143 |
* is null, |
1144 |
* @throws IllegalStateException if the computation detectably |
1145 |
* attempts a recursive update to this map that would |
1146 |
* otherwise never complete. |
1147 |
* @throws RuntimeException or Error if the mappingFunction does so, |
1148 |
* in which case the mapping is left unestablished. |
1149 |
*/ |
1150 |
public V computeIfAbsent(K key, MappingFunction<? super K, ? extends V> mappingFunction) { |
1151 |
if (key == null || mappingFunction == null) |
1152 |
throw new NullPointerException(); |
1153 |
return internalCompute(key, mappingFunction, false); |
1154 |
} |
1155 |
|
1156 |
/** |
1157 |
* Computes the value associated with the given key using the given |
1158 |
* mappingFunction, and if non-null, enters it into the map. This |
1159 |
* is equivalent to |
1160 |
* |
1161 |
* <pre> |
1162 |
* value = mappingFunction.map(key); |
1163 |
* if (value != null) |
1164 |
* map.put(key, value); |
1165 |
* else |
1166 |
* value = map.get(key); |
1167 |
* return value; |
1168 |
* </pre> |
1169 |
* |
1170 |
* except that the action is performed atomically. Some attempted |
1171 |
* update operations on this map by other threads may be blocked |
1172 |
* while computation is in progress, so the computation should be |
1173 |
* short and simple, and must not attempt to update any other |
1174 |
* mappings of this Map. |
1175 |
* |
1176 |
* @param key key with which the specified value is to be associated |
1177 |
* @param mappingFunction the function to compute a value |
1178 |
* @return the current value associated with |
1179 |
* the specified key, or {@code null} if the computation |
1180 |
* returned {@code null} and the value was not otherwise present. |
1181 |
* @throws NullPointerException if the specified key or mappingFunction |
1182 |
* is null, |
1183 |
* @throws IllegalStateException if the computation detectably |
1184 |
* attempts a recursive update to this map that would |
1185 |
* otherwise never complete. |
1186 |
* @throws RuntimeException or Error if the mappingFunction does so, |
1187 |
* in which case the mapping is unchanged. |
1188 |
*/ |
1189 |
public V compute(K key, MappingFunction<? super K, ? extends V> mappingFunction) { |
1190 |
if (key == null || mappingFunction == null) |
1191 |
throw new NullPointerException(); |
1192 |
return internalCompute(key, mappingFunction, true); |
1193 |
} |
1194 |
|
1195 |
/** |
1196 |
* Removes the key (and its corresponding value) from this map. |
1197 |
* This method does nothing if the key is not in the map. |
1198 |
* |
1199 |
* @param key the key that needs to be removed |
1200 |
* @return the previous value associated with {@code key}, or |
1201 |
* {@code null} if there was no mapping for {@code key} |
1202 |
* @throws NullPointerException if the specified key is null |
1203 |
*/ |
1204 |
@SuppressWarnings("unchecked") |
1205 |
public V remove(Object key) { |
1206 |
if (key == null) |
1207 |
throw new NullPointerException(); |
1208 |
return (V)internalReplace(key, null, null); |
1209 |
} |
1210 |
|
1211 |
/** |
1212 |
* {@inheritDoc} |
1213 |
* |
1214 |
* @throws NullPointerException if the specified key is null |
1215 |
*/ |
1216 |
public boolean remove(Object key, Object value) { |
1217 |
if (key == null) |
1218 |
throw new NullPointerException(); |
1219 |
if (value == null) |
1220 |
return false; |
1221 |
return internalReplace(key, null, value) != null; |
1222 |
} |
1223 |
|
1224 |
/** |
1225 |
* {@inheritDoc} |
1226 |
* |
1227 |
* @throws NullPointerException if any of the arguments are null |
1228 |
*/ |
1229 |
public boolean replace(K key, V oldValue, V newValue) { |
1230 |
if (key == null || oldValue == null || newValue == null) |
1231 |
throw new NullPointerException(); |
1232 |
return internalReplace(key, newValue, oldValue) != null; |
1233 |
} |
1234 |
|
1235 |
/** |
1236 |
* {@inheritDoc} |
1237 |
* |
1238 |
* @return the previous value associated with the specified key, |
1239 |
* or {@code null} if there was no mapping for the key |
1240 |
* @throws NullPointerException if the specified key or value is null |
1241 |
*/ |
1242 |
@SuppressWarnings("unchecked") |
1243 |
public V replace(K key, V value) { |
1244 |
if (key == null || value == null) |
1245 |
throw new NullPointerException(); |
1246 |
return (V)internalReplace(key, value, null); |
1247 |
} |
1248 |
|
1249 |
/** |
1250 |
* Removes all of the mappings from this map. |
1251 |
*/ |
1252 |
public void clear() { |
1253 |
internalClear(); |
1254 |
} |
1255 |
|
1256 |
/** |
1257 |
* Returns a {@link Set} view of the keys contained in this map. |
1258 |
* The set is backed by the map, so changes to the map are |
1259 |
* reflected in the set, and vice-versa. The set supports element |
1260 |
* removal, which removes the corresponding mapping from this map, |
1261 |
* via the {@code Iterator.remove}, {@code Set.remove}, |
1262 |
* {@code removeAll}, {@code retainAll}, and {@code clear} |
1263 |
* operations. It does not support the {@code add} or |
1264 |
* {@code addAll} operations. |
1265 |
* |
1266 |
* <p>The view's {@code iterator} is a "weakly consistent" iterator |
1267 |
* that will never throw {@link ConcurrentModificationException}, |
1268 |
* and guarantees to traverse elements as they existed upon |
1269 |
* construction of the iterator, and may (but is not guaranteed to) |
1270 |
* reflect any modifications subsequent to construction. |
1271 |
*/ |
1272 |
public Set<K> keySet() { |
1273 |
Set<K> ks = keySet; |
1274 |
return (ks != null) ? ks : (keySet = new KeySet()); |
1275 |
} |
1276 |
|
1277 |
/** |
1278 |
* Returns a {@link Collection} view of the values contained in this map. |
1279 |
* The collection is backed by the map, so changes to the map are |
1280 |
* reflected in the collection, and vice-versa. The collection |
1281 |
* supports element removal, which removes the corresponding |
1282 |
* mapping from this map, via the {@code Iterator.remove}, |
1283 |
* {@code Collection.remove}, {@code removeAll}, |
1284 |
* {@code retainAll}, and {@code clear} operations. It does not |
1285 |
* support the {@code add} or {@code addAll} operations. |
1286 |
* |
1287 |
* <p>The view's {@code iterator} is a "weakly consistent" iterator |
1288 |
* that will never throw {@link ConcurrentModificationException}, |
1289 |
* and guarantees to traverse elements as they existed upon |
1290 |
* construction of the iterator, and may (but is not guaranteed to) |
1291 |
* reflect any modifications subsequent to construction. |
1292 |
*/ |
1293 |
public Collection<V> values() { |
1294 |
Collection<V> vs = values; |
1295 |
return (vs != null) ? vs : (values = new Values()); |
1296 |
} |
1297 |
|
1298 |
/** |
1299 |
* Returns a {@link Set} view of the mappings contained in this map. |
1300 |
* The set is backed by the map, so changes to the map are |
1301 |
* reflected in the set, and vice-versa. The set supports element |
1302 |
* removal, which removes the corresponding mapping from the map, |
1303 |
* via the {@code Iterator.remove}, {@code Set.remove}, |
1304 |
* {@code removeAll}, {@code retainAll}, and {@code clear} |
1305 |
* operations. It does not support the {@code add} or |
1306 |
* {@code addAll} operations. |
1307 |
* |
1308 |
* <p>The view's {@code iterator} is a "weakly consistent" iterator |
1309 |
* that will never throw {@link ConcurrentModificationException}, |
1310 |
* and guarantees to traverse elements as they existed upon |
1311 |
* construction of the iterator, and may (but is not guaranteed to) |
1312 |
* reflect any modifications subsequent to construction. |
1313 |
*/ |
1314 |
public Set<Map.Entry<K,V>> entrySet() { |
1315 |
Set<Map.Entry<K,V>> es = entrySet; |
1316 |
return (es != null) ? es : (entrySet = new EntrySet()); |
1317 |
} |
1318 |
|
1319 |
/** |
1320 |
* Returns an enumeration of the keys in this table. |
1321 |
* |
1322 |
* @return an enumeration of the keys in this table |
1323 |
* @see #keySet() |
1324 |
*/ |
1325 |
public Enumeration<K> keys() { |
1326 |
return new KeyIterator(); |
1327 |
} |
1328 |
|
1329 |
/** |
1330 |
* Returns an enumeration of the values in this table. |
1331 |
* |
1332 |
* @return an enumeration of the values in this table |
1333 |
* @see #values() |
1334 |
*/ |
1335 |
public Enumeration<V> elements() { |
1336 |
return new ValueIterator(); |
1337 |
} |
1338 |
|
1339 |
/** |
1340 |
* Returns the hash code value for this {@link Map}, i.e., |
1341 |
* the sum of, for each key-value pair in the map, |
1342 |
* {@code key.hashCode() ^ value.hashCode()}. |
1343 |
* |
1344 |
* @return the hash code value for this map |
1345 |
*/ |
1346 |
public int hashCode() { |
1347 |
return new HashIterator().mapHashCode(); |
1348 |
} |
1349 |
|
1350 |
/** |
1351 |
* Returns a string representation of this map. The string |
1352 |
* representation consists of a list of key-value mappings (in no |
1353 |
* particular order) enclosed in braces ("{@code {}}"). Adjacent |
1354 |
* mappings are separated by the characters {@code ", "} (comma |
1355 |
* and space). Each key-value mapping is rendered as the key |
1356 |
* followed by an equals sign ("{@code =}") followed by the |
1357 |
* associated value. |
1358 |
* |
1359 |
* @return a string representation of this map |
1360 |
*/ |
1361 |
public String toString() { |
1362 |
return new HashIterator().mapToString(); |
1363 |
} |
1364 |
|
1365 |
/** |
1366 |
* Compares the specified object with this map for equality. |
1367 |
* Returns {@code true} if the given object is a map with the same |
1368 |
* mappings as this map. This operation may return misleading |
1369 |
* results if either map is concurrently modified during execution |
1370 |
* of this method. |
1371 |
* |
1372 |
* @param o object to be compared for equality with this map |
1373 |
* @return {@code true} if the specified object is equal to this map |
1374 |
*/ |
1375 |
public boolean equals(Object o) { |
1376 |
if (o == this) |
1377 |
return true; |
1378 |
if (!(o instanceof Map)) |
1379 |
return false; |
1380 |
Map<?,?> m = (Map<?,?>) o; |
1381 |
try { |
1382 |
for (Map.Entry<K,V> e : this.entrySet()) |
1383 |
if (! e.getValue().equals(m.get(e.getKey()))) |
1384 |
return false; |
1385 |
for (Map.Entry<?,?> e : m.entrySet()) { |
1386 |
Object k = e.getKey(); |
1387 |
Object v = e.getValue(); |
1388 |
if (k == null || v == null || !v.equals(get(k))) |
1389 |
return false; |
1390 |
} |
1391 |
return true; |
1392 |
} catch (ClassCastException unused) { |
1393 |
return false; |
1394 |
} catch (NullPointerException unused) { |
1395 |
return false; |
1396 |
} |
1397 |
} |
1398 |
|
1399 |
/** |
1400 |
* Custom Entry class used by EntryIterator.next(), that relays |
1401 |
* setValue changes to the underlying map. |
1402 |
*/ |
1403 |
final class WriteThroughEntry extends AbstractMap.SimpleEntry<K,V> { |
1404 |
@SuppressWarnings("unchecked") |
1405 |
WriteThroughEntry(Object k, Object v) { |
1406 |
super((K)k, (V)v); |
1407 |
} |
1408 |
|
1409 |
/** |
1410 |
* Sets our entry's value and writes through to the map. The |
1411 |
* value to return is somewhat arbitrary here. Since a |
1412 |
* WriteThroughEntry does not necessarily track asynchronous |
1413 |
* changes, the most recent "previous" value could be |
1414 |
* different from what we return (or could even have been |
1415 |
* removed in which case the put will re-establish). We do not |
1416 |
* and cannot guarantee more. |
1417 |
*/ |
1418 |
public V setValue(V value) { |
1419 |
if (value == null) throw new NullPointerException(); |
1420 |
V v = super.setValue(value); |
1421 |
ConcurrentHashMapV8.this.put(getKey(), value); |
1422 |
return v; |
1423 |
} |
1424 |
} |
1425 |
|
1426 |
final class KeyIterator extends HashIterator |
1427 |
implements Iterator<K>, Enumeration<K> { |
1428 |
@SuppressWarnings("unchecked") |
1429 |
public final K next() { return (K)super.nextKey(); } |
1430 |
@SuppressWarnings("unchecked") |
1431 |
public final K nextElement() { return (K)super.nextKey(); } |
1432 |
} |
1433 |
|
1434 |
final class ValueIterator extends HashIterator |
1435 |
implements Iterator<V>, Enumeration<V> { |
1436 |
@SuppressWarnings("unchecked") |
1437 |
public final V next() { return (V)super.nextValue(); } |
1438 |
@SuppressWarnings("unchecked") |
1439 |
public final V nextElement() { return (V)super.nextValue(); } |
1440 |
} |
1441 |
|
1442 |
final class EntryIterator extends HashIterator |
1443 |
implements Iterator<Entry<K,V>> { |
1444 |
public final Map.Entry<K,V> next() { return super.nextEntry(); } |
1445 |
} |
1446 |
|
1447 |
final class KeySet extends AbstractSet<K> { |
1448 |
public int size() { |
1449 |
return ConcurrentHashMapV8.this.size(); |
1450 |
} |
1451 |
public boolean isEmpty() { |
1452 |
return ConcurrentHashMapV8.this.isEmpty(); |
1453 |
} |
1454 |
public void clear() { |
1455 |
ConcurrentHashMapV8.this.clear(); |
1456 |
} |
1457 |
public Iterator<K> iterator() { |
1458 |
return new KeyIterator(); |
1459 |
} |
1460 |
public boolean contains(Object o) { |
1461 |
return ConcurrentHashMapV8.this.containsKey(o); |
1462 |
} |
1463 |
public boolean remove(Object o) { |
1464 |
return ConcurrentHashMapV8.this.remove(o) != null; |
1465 |
} |
1466 |
} |
1467 |
|
1468 |
final class Values extends AbstractCollection<V> { |
1469 |
public int size() { |
1470 |
return ConcurrentHashMapV8.this.size(); |
1471 |
} |
1472 |
public boolean isEmpty() { |
1473 |
return ConcurrentHashMapV8.this.isEmpty(); |
1474 |
} |
1475 |
public void clear() { |
1476 |
ConcurrentHashMapV8.this.clear(); |
1477 |
} |
1478 |
public Iterator<V> iterator() { |
1479 |
return new ValueIterator(); |
1480 |
} |
1481 |
public boolean contains(Object o) { |
1482 |
return ConcurrentHashMapV8.this.containsValue(o); |
1483 |
} |
1484 |
} |
1485 |
|
1486 |
final class EntrySet extends AbstractSet<Map.Entry<K,V>> { |
1487 |
public int size() { |
1488 |
return ConcurrentHashMapV8.this.size(); |
1489 |
} |
1490 |
public boolean isEmpty() { |
1491 |
return ConcurrentHashMapV8.this.isEmpty(); |
1492 |
} |
1493 |
public void clear() { |
1494 |
ConcurrentHashMapV8.this.clear(); |
1495 |
} |
1496 |
public Iterator<Map.Entry<K,V>> iterator() { |
1497 |
return new EntryIterator(); |
1498 |
} |
1499 |
public boolean contains(Object o) { |
1500 |
if (!(o instanceof Map.Entry)) |
1501 |
return false; |
1502 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1503 |
V v = ConcurrentHashMapV8.this.get(e.getKey()); |
1504 |
return v != null && v.equals(e.getValue()); |
1505 |
} |
1506 |
public boolean remove(Object o) { |
1507 |
if (!(o instanceof Map.Entry)) |
1508 |
return false; |
1509 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1510 |
return ConcurrentHashMapV8.this.remove(e.getKey(), e.getValue()); |
1511 |
} |
1512 |
} |
1513 |
|
1514 |
/* ---------------- Serialization Support -------------- */ |
1515 |
|
1516 |
/** |
1517 |
* Helper class used in previous version, declared for the sake of |
1518 |
* serialization compatibility |
1519 |
*/ |
1520 |
static class Segment<K,V> extends java.util.concurrent.locks.ReentrantLock |
1521 |
implements Serializable { |
1522 |
private static final long serialVersionUID = 2249069246763182397L; |
1523 |
final float loadFactor; |
1524 |
Segment(float lf) { this.loadFactor = lf; } |
1525 |
} |
1526 |
|
1527 |
/** |
1528 |
* Saves the state of the {@code ConcurrentHashMapV8} instance to a |
1529 |
* stream (i.e., serializes it). |
1530 |
* @param s the stream |
1531 |
* @serialData |
1532 |
* the key (Object) and value (Object) |
1533 |
* for each key-value mapping, followed by a null pair. |
1534 |
* The key-value mappings are emitted in no particular order. |
1535 |
*/ |
1536 |
@SuppressWarnings("unchecked") |
1537 |
private void writeObject(java.io.ObjectOutputStream s) |
1538 |
throws java.io.IOException { |
1539 |
if (segments == null) { // for serialization compatibility |
1540 |
segments = (Segment<K,V>[]) |
1541 |
new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL]; |
1542 |
for (int i = 0; i < segments.length; ++i) |
1543 |
segments[i] = new Segment<K,V>(loadFactor); |
1544 |
} |
1545 |
s.defaultWriteObject(); |
1546 |
new HashIterator().writeEntries(s); |
1547 |
s.writeObject(null); |
1548 |
s.writeObject(null); |
1549 |
segments = null; // throw away |
1550 |
} |
1551 |
|
1552 |
/** |
1553 |
* Reconstitutes the instance from a |
1554 |
* stream (i.e., deserializes it). |
1555 |
* @param s the stream |
1556 |
*/ |
1557 |
@SuppressWarnings("unchecked") |
1558 |
private void readObject(java.io.ObjectInputStream s) |
1559 |
throws java.io.IOException, ClassNotFoundException { |
1560 |
s.defaultReadObject(); |
1561 |
// find load factor in a segment, if one exists |
1562 |
if (segments != null && segments.length != 0) |
1563 |
this.loadFactor = segments[0].loadFactor; |
1564 |
else |
1565 |
this.loadFactor = DEFAULT_LOAD_FACTOR; |
1566 |
this.initCap = DEFAULT_CAPACITY; |
1567 |
LongAdder ct = new LongAdder(); // force final field write |
1568 |
UNSAFE.putObjectVolatile(this, counterOffset, ct); |
1569 |
this.segments = null; // unneeded |
1570 |
|
1571 |
// Read the keys and values, and put the mappings in the table |
1572 |
for (;;) { |
1573 |
K key = (K) s.readObject(); |
1574 |
V value = (V) s.readObject(); |
1575 |
if (key == null) |
1576 |
break; |
1577 |
put(key, value); |
1578 |
} |
1579 |
} |
1580 |
|
1581 |
// Unsafe mechanics |
1582 |
private static final sun.misc.Unsafe UNSAFE; |
1583 |
private static final long counterOffset; |
1584 |
private static final long resizingOffset; |
1585 |
private static final long ABASE; |
1586 |
private static final int ASHIFT; |
1587 |
|
1588 |
static { |
1589 |
int ss; |
1590 |
try { |
1591 |
UNSAFE = getUnsafe(); |
1592 |
Class<?> k = ConcurrentHashMapV8.class; |
1593 |
counterOffset = UNSAFE.objectFieldOffset |
1594 |
(k.getDeclaredField("counter")); |
1595 |
resizingOffset = UNSAFE.objectFieldOffset |
1596 |
(k.getDeclaredField("resizing")); |
1597 |
Class<?> sc = Node[].class; |
1598 |
ABASE = UNSAFE.arrayBaseOffset(sc); |
1599 |
ss = UNSAFE.arrayIndexScale(sc); |
1600 |
} catch (Exception e) { |
1601 |
throw new Error(e); |
1602 |
} |
1603 |
if ((ss & (ss-1)) != 0) |
1604 |
throw new Error("data type scale not a power of two"); |
1605 |
ASHIFT = 31 - Integer.numberOfLeadingZeros(ss); |
1606 |
} |
1607 |
|
1608 |
/** |
1609 |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1610 |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1611 |
* into a jdk. |
1612 |
* |
1613 |
* @return a sun.misc.Unsafe |
1614 |
*/ |
1615 |
private static sun.misc.Unsafe getUnsafe() { |
1616 |
try { |
1617 |
return sun.misc.Unsafe.getUnsafe(); |
1618 |
} catch (SecurityException se) { |
1619 |
try { |
1620 |
return java.security.AccessController.doPrivileged |
1621 |
(new java.security |
1622 |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1623 |
public sun.misc.Unsafe run() throws Exception { |
1624 |
java.lang.reflect.Field f = sun.misc |
1625 |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1626 |
f.setAccessible(true); |
1627 |
return (sun.misc.Unsafe) f.get(null); |
1628 |
}}); |
1629 |
} catch (java.security.PrivilegedActionException e) { |
1630 |
throw new RuntimeException("Could not initialize intrinsics", |
1631 |
e.getCause()); |
1632 |
} |
1633 |
} |
1634 |
} |
1635 |
|
1636 |
} |