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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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* compatability 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</code> if there is no mapping. This is a |
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* place-holder for an upcoming JDK8 interface. |
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*/ |
89 |
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 |
114 |
* 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 served for special |
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* nodes.) |
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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 |
139 |
* 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. The expected number of locks |
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* covering different elements (i.e., bins with 2 or more nodes) |
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* is approximately 10% at steady state under default settings. |
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* Lock contention probability for two threads accessing arbitrary |
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* distinct elements is thus less than 1% even for small tables. |
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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 |
158 |
* 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 |
172 |
* 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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* (While not yet implemented, a similar traversal scheme can |
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* apply to partial traversals during partitioned aggregate |
177 |
* operations. Also, read-only operations give up if ever |
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* forwarded to a null table, which provides support for |
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* shutdown-style clearing, which is also not currently |
180 |
* 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 attempted only upon adding to a bin already |
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* holding two or more nodes. Under the default threshold (0.75), |
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* and uniform hash distributions, the probability of this |
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* occurring at threshold is around 13%, meaning that only about 1 |
189 |
* in 8 puts check threshold (and after resizing, many fewer do |
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* so). To increase the probablity that a resize occurs soon |
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* enough, we offset the threshold (see THRESHOLD_OFFSET) by the |
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* expected number of puts between checks. This is currently set |
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* to 8, in accord with the default load factor. In practice, this |
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* is rarely overridden, and in any case is close enough to other |
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* plausible values not to waste dynamic probablity 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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/** |
226 |
* 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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*/ |
229 |
static final int DEFAULT_CONCURRENCY_LEVEL = 16; |
230 |
|
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/** |
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* The count value to offset thesholds 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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*/ |
236 |
static final int THRESHOLD_OFFSET = 8; |
237 |
|
238 |
/** |
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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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*/ |
242 |
static final int MOVED = -1; |
243 |
|
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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. |
250 |
*/ |
251 |
transient volatile Node[] table; |
252 |
|
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/** The counter maintaining number of elements. */ |
254 |
private transient final LongAdder counter; |
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/** Nonzero when table is being initialized or resized. Updated via CAS. */ |
256 |
private transient volatile int resizing; |
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/** The target load factor for the table. */ |
258 |
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; |
268 |
|
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/** For serialization compatability. Null unless serialized; see below */ |
270 |
Segment<K,V>[] segments; |
271 |
|
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/** |
273 |
* Applies a supplemental hash function to a given hashCode, which |
274 |
* defends against poor quality hash functions. The result must |
275 |
* be non-negative, and for reasonable performance must have good |
276 |
* avalanche properties; i.e., that each bit of the argument |
277 |
* affects each bit (except sign bit) of the result. |
278 |
*/ |
279 |
private static final int spread(int h) { |
280 |
// Apply base step of MurmurHash; see http://code.google.com/p/smhasher/ |
281 |
h ^= h >>> 16; |
282 |
h *= 0x85ebca6b; |
283 |
h ^= h >>> 13; |
284 |
h *= 0xc2b2ae35; |
285 |
return (h >>> 16) ^ (h & 0x7fffffff); // mask out sign bit |
286 |
} |
287 |
|
288 |
/** |
289 |
* Key-value entry. Note that this is never exported out as a |
290 |
* user-visible Map.Entry. |
291 |
*/ |
292 |
static final class Node { |
293 |
final int hash; |
294 |
final Object key; |
295 |
volatile Object val; |
296 |
volatile Node next; |
297 |
|
298 |
Node(int hash, Object key, Object val, Node next) { |
299 |
this.hash = hash; |
300 |
this.key = key; |
301 |
this.val = val; |
302 |
this.next = next; |
303 |
} |
304 |
} |
305 |
|
306 |
/* |
307 |
* Volatile access nethods are used for table elements as well as |
308 |
* elements of in-progress next table while resizing. Uses in |
309 |
* access and update methods are null checked by callers, and |
310 |
* implicitly bounds-checked, relying on the invariants that tab |
311 |
* arrays have non-zero size, and all indices are masked with |
312 |
* (tab.length - 1) which is never negative and always less than |
313 |
* length. The only other usage is in HashIterator.advance, which |
314 |
* performs explicit checks. |
315 |
*/ |
316 |
|
317 |
static final Node tabAt(Node[] tab, int i) { // used in HashIterator |
318 |
return (Node)UNSAFE.getObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE); |
319 |
} |
320 |
|
321 |
private static final boolean casTabAt(Node[] tab, int i, Node c, Node v) { |
322 |
return UNSAFE.compareAndSwapObject(tab, ((long)i<<ASHIFT)+ABASE, c, v); |
323 |
} |
324 |
|
325 |
private static final void setTabAt(Node[] tab, int i, Node v) { |
326 |
UNSAFE.putObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE, v); |
327 |
} |
328 |
|
329 |
/* ---------------- Access and update operations -------------- */ |
330 |
|
331 |
/** Implements get and containsKey **/ |
332 |
private final Object internalGet(Object k) { |
333 |
int h = spread(k.hashCode()); |
334 |
Node[] tab = table; |
335 |
retry: while (tab != null) { |
336 |
Node e = tabAt(tab, (tab.length - 1) & h); |
337 |
while (e != null) { |
338 |
int eh = e.hash; |
339 |
if (eh == h) { |
340 |
Object ek = e.key, ev = e.val; |
341 |
if (ev != null && ek != null && (k == ek || k.equals(ek))) |
342 |
return ev; |
343 |
} |
344 |
if (eh < 0) { // bin was moved during resize |
345 |
tab = (Node[])e.key; |
346 |
continue retry; |
347 |
} |
348 |
e = e.next; |
349 |
} |
350 |
break; |
351 |
} |
352 |
return null; |
353 |
} |
354 |
|
355 |
/** Implements put and putIfAbsent **/ |
356 |
private final Object internalPut(Object k, Object v, boolean replace) { |
357 |
int h = spread(k.hashCode()); |
358 |
Object oldVal = null; // the previous value or null if none |
359 |
Node node = null; // the node created if absent |
360 |
Node[] tab = table; |
361 |
for (;;) { |
362 |
Node e; int i; |
363 |
if (tab == null) |
364 |
tab = grow(0); |
365 |
else if ((e = tabAt(tab, i = (tab.length - 1) & h)) == null) { |
366 |
if (node == null) |
367 |
node = new Node(h, k, v, null); |
368 |
if (casTabAt(tab, i, null, node)) |
369 |
break; |
370 |
} |
371 |
else if (e.hash < 0) |
372 |
tab = (Node[])e.key; |
373 |
else { |
374 |
boolean validated = false; |
375 |
boolean checkSize = false; |
376 |
synchronized(e) { |
377 |
Node first = e; |
378 |
for (;;) { |
379 |
Object ek, ev; |
380 |
if ((ev = e.val) == null) |
381 |
break; |
382 |
if (e.hash == h && (ek = e.key) != null && |
383 |
(k == ek || k.equals(ek))) { |
384 |
if (tabAt(tab, i) == first) { |
385 |
validated = true; |
386 |
oldVal = ev; |
387 |
if (replace) |
388 |
e.val = v; |
389 |
} |
390 |
break; |
391 |
} |
392 |
Node last = e; |
393 |
if ((e = e.next) == null) { |
394 |
if (tabAt(tab, i) == first) { |
395 |
validated = true; |
396 |
if (node == null) |
397 |
node = new Node(h, k, v, null); |
398 |
last.next = node; |
399 |
if (last != first) |
400 |
checkSize = true; |
401 |
} |
402 |
break; |
403 |
} |
404 |
} |
405 |
} |
406 |
if (validated) { |
407 |
if (checkSize && tab.length < MAXIMUM_CAPACITY && |
408 |
resizing == 0 && counter.sum() >= threshold) |
409 |
grow(0); |
410 |
break; |
411 |
} |
412 |
} |
413 |
} |
414 |
if (oldVal == null) |
415 |
counter.increment(); |
416 |
return oldVal; |
417 |
} |
418 |
|
419 |
/** |
420 |
* Covers the four public remove/replace methods: Replaces node |
421 |
* value with v, conditional upon match of cv if non-null. If |
422 |
* resulting value is null, delete. |
423 |
*/ |
424 |
private final Object internalReplace(Object k, Object v, Object cv) { |
425 |
int h = spread(k.hashCode()); |
426 |
Object oldVal = null; |
427 |
Node e; int i; |
428 |
Node[] tab = table; |
429 |
while (tab != null && |
430 |
(e = tabAt(tab, i = (tab.length - 1) & h)) != null) { |
431 |
if (e.hash < 0) |
432 |
tab = (Node[])e.key; |
433 |
else { |
434 |
boolean validated = false; |
435 |
boolean deleted = false; |
436 |
synchronized(e) { |
437 |
Node pred = null; |
438 |
Node first = e; |
439 |
for (;;) { |
440 |
Object ek, ev; |
441 |
if ((ev = e.val) == null) |
442 |
break; |
443 |
if (e.hash == h && (ek = e.key) != null && |
444 |
(k == ek || k.equals(ek))) { |
445 |
if (tabAt(tab, i) == first) { |
446 |
validated = true; |
447 |
if (cv == null || cv == ev || cv.equals(ev)) { |
448 |
oldVal = ev; |
449 |
if ((e.val = v) == null) { |
450 |
deleted = true; |
451 |
Node en = e.next; |
452 |
if (pred != null) |
453 |
pred.next = en; |
454 |
else |
455 |
setTabAt(tab, i, en); |
456 |
} |
457 |
} |
458 |
} |
459 |
break; |
460 |
} |
461 |
pred = e; |
462 |
if ((e = e.next) == null) { |
463 |
if (tabAt(tab, i) == first) |
464 |
validated = true; |
465 |
break; |
466 |
} |
467 |
} |
468 |
} |
469 |
if (validated) { |
470 |
if (deleted) |
471 |
counter.decrement(); |
472 |
break; |
473 |
} |
474 |
} |
475 |
} |
476 |
return oldVal; |
477 |
} |
478 |
|
479 |
/** Implements computeIfAbsent */ |
480 |
@SuppressWarnings("unchecked") |
481 |
private final V computeVal(K k, MappingFunction<? super K, ? extends V> f) { |
482 |
int h = spread(k.hashCode()); |
483 |
V val = null; |
484 |
Node node = null; |
485 |
boolean added = false; |
486 |
boolean validated = false; |
487 |
Node[] tab = table; |
488 |
do { |
489 |
Node e; int i; |
490 |
if (tab == null) |
491 |
tab = grow(0); |
492 |
else if ((e = tabAt(tab, i = (tab.length - 1) & h)) == null) { |
493 |
if (node == null) |
494 |
node = new Node(h, k, null, null); |
495 |
synchronized(node) { |
496 |
if (casTabAt(tab, i, null, node)) { |
497 |
validated = true; |
498 |
try { |
499 |
val = f.map(k); |
500 |
if (val != null) { |
501 |
node.val = val; |
502 |
added = true; |
503 |
} |
504 |
} finally { |
505 |
if (!added) |
506 |
setTabAt(tab, i, null); |
507 |
} |
508 |
} |
509 |
} |
510 |
} |
511 |
else if (e.hash < 0) |
512 |
tab = (Node[])e.key; |
513 |
else { |
514 |
boolean checkSize = false; |
515 |
synchronized(e) { |
516 |
Node first = e; |
517 |
for (;;) { |
518 |
Object ek, ev; |
519 |
if ((ev = e.val) == null) |
520 |
break; |
521 |
if (e.hash == h && (ek = e.key) != null && |
522 |
(k == ek || k.equals(ek))) { |
523 |
if (tabAt(tab, i) == first) { |
524 |
validated = true; |
525 |
val = (V)ev; |
526 |
} |
527 |
break; |
528 |
} |
529 |
Node last = e; |
530 |
if ((e = e.next) == null) { |
531 |
if (tabAt(tab, i) == first) { |
532 |
validated = true; |
533 |
if ((val = f.map(k)) != null) { |
534 |
if (node == null) |
535 |
node = new Node(h, k, val, null); |
536 |
else |
537 |
node.val = val; |
538 |
last.next = node; |
539 |
if (last != first) |
540 |
checkSize = true; |
541 |
added = true; |
542 |
} |
543 |
} |
544 |
break; |
545 |
} |
546 |
} |
547 |
} |
548 |
if (checkSize && tab.length < MAXIMUM_CAPACITY && |
549 |
resizing == 0 && counter.sum() >= threshold) |
550 |
grow(0); |
551 |
} |
552 |
} while (!validated); |
553 |
if (added) |
554 |
counter.increment(); |
555 |
return val; |
556 |
} |
557 |
|
558 |
/* |
559 |
* Reclassifies nodes in each bin to new table. Because we are |
560 |
* using power-of-two expansion, the elements from each bin must |
561 |
* either stay at same index, or move with a power of two |
562 |
* offset. We eliminate unnecessary node creation by catching |
563 |
* cases where old nodes can be reused because their next fields |
564 |
* won't change. Statistically, at the default threshold, only |
565 |
* about one-sixth of them need cloning when a table doubles. The |
566 |
* nodes they replace will be garbage collectable as soon as they |
567 |
* are no longer referenced by any reader thread that may be in |
568 |
* the midst of concurrently traversing table. |
569 |
* |
570 |
* Transfers are done from the bottom up to preserve iterator |
571 |
* traversability. On each step, the old bin is locked, |
572 |
* moved/copied, and then replaced with a forwarding node. |
573 |
*/ |
574 |
private static final void transfer(Node[] tab, Node[] nextTab) { |
575 |
int n = tab.length; |
576 |
int mask = nextTab.length - 1; |
577 |
Node fwd = new Node(MOVED, nextTab, null, null); |
578 |
for (int i = n - 1; i >= 0; --i) { |
579 |
for (Node e;;) { |
580 |
if ((e = tabAt(tab, i)) == null) { |
581 |
if (casTabAt(tab, i, e, fwd)) |
582 |
break; |
583 |
} |
584 |
else { |
585 |
boolean validated = false; |
586 |
synchronized(e) { |
587 |
int idx = e.hash & mask; |
588 |
Node lastRun = e; |
589 |
for (Node p = e.next; p != null; p = p.next) { |
590 |
int j = p.hash & mask; |
591 |
if (j != idx) { |
592 |
idx = j; |
593 |
lastRun = p; |
594 |
} |
595 |
} |
596 |
if (tabAt(tab, i) == e) { |
597 |
validated = true; |
598 |
setTabAt(nextTab, idx, lastRun); |
599 |
for (Node p = e; p != lastRun; p = p.next) { |
600 |
int h = p.hash; |
601 |
int j = h & mask; |
602 |
Object pk = p.key, pv = p.val; |
603 |
Node r = tabAt(nextTab, j); |
604 |
setTabAt(nextTab, j, new Node(h, pk, pv, r)); |
605 |
} |
606 |
setTabAt(tab, i, fwd); |
607 |
} |
608 |
} |
609 |
if (validated) |
610 |
break; |
611 |
} |
612 |
} |
613 |
} |
614 |
} |
615 |
|
616 |
/** |
617 |
* If not already resizing, initializes or creates next table and |
618 |
* transfers bins. Rechecks occupancy after a transfer to see if |
619 |
* another resize is already needed because resizings are lagging |
620 |
* additions. |
621 |
* |
622 |
* @param sizeHint overridden capacity target (nonzero only from putAll) |
623 |
* @return current table |
624 |
*/ |
625 |
private final Node[] grow(int sizeHint) { |
626 |
Node[] tab; |
627 |
if (resizing == 0 && |
628 |
UNSAFE.compareAndSwapInt(this, resizingOffset, 0, 1)) { |
629 |
try { |
630 |
for (;;) { |
631 |
int cap, n; |
632 |
if ((tab = table) == null) { |
633 |
int c = initCap; |
634 |
if (c < sizeHint) |
635 |
c = sizeHint; |
636 |
if (c == DEFAULT_CAPACITY) |
637 |
cap = c; |
638 |
else if (c >= MAXIMUM_CAPACITY) |
639 |
cap = MAXIMUM_CAPACITY; |
640 |
else { |
641 |
cap = MINIMUM_CAPACITY; |
642 |
while (cap < c) |
643 |
cap <<= 1; |
644 |
} |
645 |
} |
646 |
else if ((n = tab.length) < MAXIMUM_CAPACITY && |
647 |
(sizeHint <= 0 || n < sizeHint)) |
648 |
cap = n << 1; |
649 |
else |
650 |
break; |
651 |
threshold = (int)(cap * loadFactor) - THRESHOLD_OFFSET; |
652 |
Node[] nextTab = new Node[cap]; |
653 |
if (tab != null) |
654 |
transfer(tab, nextTab); |
655 |
table = nextTab; |
656 |
if (tab == null || counter.sum() < threshold) { |
657 |
tab = nextTab; |
658 |
break; |
659 |
} |
660 |
} |
661 |
} finally { |
662 |
resizing = 0; |
663 |
} |
664 |
} |
665 |
else if ((tab = table) == null) |
666 |
Thread.yield(); // lost initialization race; just spin |
667 |
return tab; |
668 |
} |
669 |
|
670 |
/** |
671 |
* Implements putAll and constructor with Map argument. Tries to |
672 |
* first override initial capacity or grow (once) based on map |
673 |
* size to pre-allocate table space. |
674 |
*/ |
675 |
private final void internalPutAll(Map<? extends K, ? extends V> m) { |
676 |
int s = m.size(); |
677 |
grow((s >= (MAXIMUM_CAPACITY >>> 1))? s : s + (s >>> 1)); |
678 |
for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) { |
679 |
Object k = e.getKey(); |
680 |
Object v = e.getValue(); |
681 |
if (k == null || v == null) |
682 |
throw new NullPointerException(); |
683 |
internalPut(k, v, true); |
684 |
} |
685 |
} |
686 |
|
687 |
/** |
688 |
* Implements clear. Steps through each bin, removing all nodes. |
689 |
*/ |
690 |
private final void internalClear() { |
691 |
long delta = 0L; // negative of number of deletions |
692 |
int i = 0; |
693 |
Node[] tab = table; |
694 |
while (tab != null && i < tab.length) { |
695 |
Node e = tabAt(tab, i); |
696 |
if (e == null) |
697 |
++i; |
698 |
else if (e.hash < 0) |
699 |
tab = (Node[])e.key; |
700 |
else { |
701 |
boolean validated = false; |
702 |
synchronized(e) { |
703 |
if (tabAt(tab, i) == e) { |
704 |
validated = true; |
705 |
do { |
706 |
if (e.val != null) { |
707 |
e.val = null; |
708 |
--delta; |
709 |
} |
710 |
} while ((e = e.next) != null); |
711 |
setTabAt(tab, i, null); |
712 |
} |
713 |
} |
714 |
if (validated) |
715 |
++i; |
716 |
} |
717 |
} |
718 |
counter.add(delta); |
719 |
} |
720 |
|
721 |
/** |
722 |
* Base class for key, value, and entry iterators, plus internal |
723 |
* implementations of public traversal-based methods, to avoid |
724 |
* duplicating traversal code. |
725 |
*/ |
726 |
class HashIterator { |
727 |
private Node next; // the next entry to return |
728 |
private Node[] tab; // current table; updated if resized |
729 |
private Node lastReturned; // the last entry returned, for remove |
730 |
private Object nextVal; // cached value of next |
731 |
private int index; // index of bin to use next |
732 |
private int baseIndex; // current index of initial table |
733 |
private final int baseSize; // initial table size |
734 |
|
735 |
HashIterator() { |
736 |
Node[] t = tab = table; |
737 |
if (t == null) |
738 |
baseSize = 0; |
739 |
else { |
740 |
baseSize = t.length; |
741 |
advance(null); |
742 |
} |
743 |
} |
744 |
|
745 |
public final boolean hasNext() { return next != null; } |
746 |
public final boolean hasMoreElements() { return next != null; } |
747 |
|
748 |
/** |
749 |
* Advances next. Normally, iteration proceeds bin-by-bin |
750 |
* traversing lists. However, if the table has been resized, |
751 |
* then all future steps must traverse both the bin at the |
752 |
* current index as well as at (index + baseSize); and so on |
753 |
* for further resizings. To paranoically cope with potential |
754 |
* (improper) sharing of iterators across threads, table reads |
755 |
* are bounds-checked. |
756 |
*/ |
757 |
final void advance(Node e) { |
758 |
for (;;) { |
759 |
Node[] t; int i; // for bounds checks |
760 |
if (e != null) { |
761 |
Object ek = e.key, ev = e.val; |
762 |
if (ev != null && ek != null) { |
763 |
nextVal = ev; |
764 |
next = e; |
765 |
break; |
766 |
} |
767 |
e = e.next; |
768 |
} |
769 |
else if (baseIndex < baseSize && (t = tab) != null && |
770 |
t.length > (i = index) && i >= 0) { |
771 |
if ((e = tabAt(t, i)) != null && e.hash < 0) { |
772 |
tab = (Node[])e.key; |
773 |
e = null; |
774 |
} |
775 |
else if (i + baseSize < t.length) |
776 |
index += baseSize; // visit forwarded upper slots |
777 |
else |
778 |
index = ++baseIndex; |
779 |
} |
780 |
else { |
781 |
next = null; |
782 |
break; |
783 |
} |
784 |
} |
785 |
} |
786 |
|
787 |
final Object nextKey() { |
788 |
Node e = next; |
789 |
if (e == null) |
790 |
throw new NoSuchElementException(); |
791 |
Object k = e.key; |
792 |
advance((lastReturned = e).next); |
793 |
return k; |
794 |
} |
795 |
|
796 |
final Object nextValue() { |
797 |
Node e = next; |
798 |
if (e == null) |
799 |
throw new NoSuchElementException(); |
800 |
Object v = nextVal; |
801 |
advance((lastReturned = e).next); |
802 |
return v; |
803 |
} |
804 |
|
805 |
final WriteThroughEntry nextEntry() { |
806 |
Node e = next; |
807 |
if (e == null) |
808 |
throw new NoSuchElementException(); |
809 |
WriteThroughEntry entry = |
810 |
new WriteThroughEntry(e.key, nextVal); |
811 |
advance((lastReturned = e).next); |
812 |
return entry; |
813 |
} |
814 |
|
815 |
public final void remove() { |
816 |
if (lastReturned == null) |
817 |
throw new IllegalStateException(); |
818 |
ConcurrentHashMapV8.this.remove(lastReturned.key); |
819 |
lastReturned = null; |
820 |
} |
821 |
|
822 |
/** Helper for serialization */ |
823 |
final void writeEntries(java.io.ObjectOutputStream s) |
824 |
throws java.io.IOException { |
825 |
Node e; |
826 |
while ((e = next) != null) { |
827 |
s.writeObject(e.key); |
828 |
s.writeObject(nextVal); |
829 |
advance(e.next); |
830 |
} |
831 |
} |
832 |
|
833 |
/** Helper for containsValue */ |
834 |
final boolean containsVal(Object value) { |
835 |
if (value != null) { |
836 |
Node e; |
837 |
while ((e = next) != null) { |
838 |
Object v = nextVal; |
839 |
if (value == v || value.equals(v)) |
840 |
return true; |
841 |
advance(e.next); |
842 |
} |
843 |
} |
844 |
return false; |
845 |
} |
846 |
|
847 |
/** Helper for Map.hashCode */ |
848 |
final int mapHashCode() { |
849 |
int h = 0; |
850 |
Node e; |
851 |
while ((e = next) != null) { |
852 |
h += e.key.hashCode() ^ nextVal.hashCode(); |
853 |
advance(e.next); |
854 |
} |
855 |
return h; |
856 |
} |
857 |
|
858 |
/** Helper for Map.toString */ |
859 |
final String mapToString() { |
860 |
Node e = next; |
861 |
if (e == null) |
862 |
return "{}"; |
863 |
StringBuilder sb = new StringBuilder(); |
864 |
sb.append('{'); |
865 |
for (;;) { |
866 |
sb.append(e.key == this ? "(this Map)" : e.key); |
867 |
sb.append('='); |
868 |
sb.append(nextVal == this ? "(this Map)" : nextVal); |
869 |
advance(e.next); |
870 |
if ((e = next) != null) |
871 |
sb.append(',').append(' '); |
872 |
else |
873 |
return sb.append('}').toString(); |
874 |
} |
875 |
} |
876 |
} |
877 |
|
878 |
/* ---------------- Public operations -------------- */ |
879 |
|
880 |
/** |
881 |
* Creates a new, empty map with the specified initial |
882 |
* capacity, load factor and concurrency level. |
883 |
* |
884 |
* @param initialCapacity the initial capacity. The implementation |
885 |
* performs internal sizing to accommodate this many elements. |
886 |
* @param loadFactor the load factor threshold, used to control resizing. |
887 |
* Resizing may be performed when the average number of elements per |
888 |
* bin exceeds this threshold. |
889 |
* @param concurrencyLevel the estimated number of concurrently |
890 |
* updating threads. The implementation may use this value as |
891 |
* a sizing hint. |
892 |
* @throws IllegalArgumentException if the initial capacity is |
893 |
* negative or the load factor or concurrencyLevel are |
894 |
* nonpositive. |
895 |
*/ |
896 |
public ConcurrentHashMapV8(int initialCapacity, |
897 |
float loadFactor, int concurrencyLevel) { |
898 |
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0) |
899 |
throw new IllegalArgumentException(); |
900 |
this.initCap = initialCapacity; |
901 |
this.loadFactor = loadFactor; |
902 |
this.counter = new LongAdder(); |
903 |
} |
904 |
|
905 |
/** |
906 |
* Creates a new, empty map with the specified initial capacity |
907 |
* and load factor and with the default concurrencyLevel (16). |
908 |
* |
909 |
* @param initialCapacity The implementation performs internal |
910 |
* sizing to accommodate this many elements. |
911 |
* @param loadFactor the load factor threshold, used to control resizing. |
912 |
* Resizing may be performed when the average number of elements per |
913 |
* bin exceeds this threshold. |
914 |
* @throws IllegalArgumentException if the initial capacity of |
915 |
* elements is negative or the load factor is nonpositive |
916 |
* |
917 |
* @since 1.6 |
918 |
*/ |
919 |
public ConcurrentHashMapV8(int initialCapacity, float loadFactor) { |
920 |
this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL); |
921 |
} |
922 |
|
923 |
/** |
924 |
* Creates a new, empty map with the specified initial capacity, |
925 |
* and with default load factor (0.75) and concurrencyLevel (16). |
926 |
* |
927 |
* @param initialCapacity the initial capacity. The implementation |
928 |
* performs internal sizing to accommodate this many elements. |
929 |
* @throws IllegalArgumentException if the initial capacity of |
930 |
* elements is negative. |
931 |
*/ |
932 |
public ConcurrentHashMapV8(int initialCapacity) { |
933 |
this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
934 |
} |
935 |
|
936 |
/** |
937 |
* Creates a new, empty map with a default initial capacity (16), |
938 |
* load factor (0.75) and concurrencyLevel (16). |
939 |
*/ |
940 |
public ConcurrentHashMapV8() { |
941 |
this(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
942 |
} |
943 |
|
944 |
/** |
945 |
* Creates a new map with the same mappings as the given map. |
946 |
* The map is created with a capacity of 1.5 times the number |
947 |
* of mappings in the given map or 16 (whichever is greater), |
948 |
* and a default load factor (0.75) and concurrencyLevel (16). |
949 |
* |
950 |
* @param m the map |
951 |
*/ |
952 |
public ConcurrentHashMapV8(Map<? extends K, ? extends V> m) { |
953 |
this(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
954 |
if (m == null) |
955 |
throw new NullPointerException(); |
956 |
internalPutAll(m); |
957 |
} |
958 |
|
959 |
/** |
960 |
* Returns {@code true} if this map contains no key-value mappings. |
961 |
* |
962 |
* @return {@code true} if this map contains no key-value mappings |
963 |
*/ |
964 |
public boolean isEmpty() { |
965 |
return counter.sum() == 0L; |
966 |
} |
967 |
|
968 |
/** |
969 |
* Returns the number of key-value mappings in this map. If the |
970 |
* map contains more than {@code Integer.MAX_VALUE} elements, returns |
971 |
* {@code Integer.MAX_VALUE}. |
972 |
* |
973 |
* @return the number of key-value mappings in this map |
974 |
*/ |
975 |
public int size() { |
976 |
long n = counter.sum(); |
977 |
return n >= Integer.MAX_VALUE ? Integer.MAX_VALUE : (int)n; |
978 |
} |
979 |
|
980 |
/** |
981 |
* Returns the value to which the specified key is mapped, |
982 |
* or {@code null} if this map contains no mapping for the key. |
983 |
* |
984 |
* <p>More formally, if this map contains a mapping from a key |
985 |
* {@code k} to a value {@code v} such that {@code key.equals(k)}, |
986 |
* then this method returns {@code v}; otherwise it returns |
987 |
* {@code null}. (There can be at most one such mapping.) |
988 |
* |
989 |
* @throws NullPointerException if the specified key is null |
990 |
*/ |
991 |
@SuppressWarnings("unchecked") |
992 |
public V get(Object key) { |
993 |
if (key == null) |
994 |
throw new NullPointerException(); |
995 |
return (V)internalGet(key); |
996 |
} |
997 |
|
998 |
/** |
999 |
* Tests if the specified object is a key in this table. |
1000 |
* |
1001 |
* @param key possible key |
1002 |
* @return {@code true} if and only if the specified object |
1003 |
* is a key in this table, as determined by the |
1004 |
* {@code equals} method; {@code false} otherwise. |
1005 |
* @throws NullPointerException if the specified key is null |
1006 |
*/ |
1007 |
public boolean containsKey(Object key) { |
1008 |
if (key == null) |
1009 |
throw new NullPointerException(); |
1010 |
return internalGet(key) != null; |
1011 |
} |
1012 |
|
1013 |
/** |
1014 |
* Returns {@code true} if this map maps one or more keys to the |
1015 |
* specified value. Note: This method requires a full internal |
1016 |
* traversal of the hash table, and so is much slower than |
1017 |
* method {@code containsKey}. |
1018 |
* |
1019 |
* @param value value whose presence in this map is to be tested |
1020 |
* @return {@code true} if this map maps one or more keys to the |
1021 |
* specified value |
1022 |
* @throws NullPointerException if the specified value is null |
1023 |
*/ |
1024 |
public boolean containsValue(Object value) { |
1025 |
if (value == null) |
1026 |
throw new NullPointerException(); |
1027 |
return new HashIterator().containsVal(value); |
1028 |
} |
1029 |
|
1030 |
/** |
1031 |
* Legacy method testing if some key maps into the specified value |
1032 |
* in this table. This method is identical in functionality to |
1033 |
* {@link #containsValue}, and exists solely to ensure |
1034 |
* full compatibility with class {@link java.util.Hashtable}, |
1035 |
* which supported this method prior to introduction of the |
1036 |
* Java Collections framework. |
1037 |
* |
1038 |
* @param value a value to search for |
1039 |
* @return {@code true} if and only if some key maps to the |
1040 |
* {@code value} argument in this table as |
1041 |
* determined by the {@code equals} method; |
1042 |
* {@code false} otherwise |
1043 |
* @throws NullPointerException if the specified value is null |
1044 |
*/ |
1045 |
public boolean contains(Object value) { |
1046 |
return containsValue(value); |
1047 |
} |
1048 |
|
1049 |
/** |
1050 |
* Maps the specified key to the specified value in this table. |
1051 |
* Neither the key nor the value can be null. |
1052 |
* |
1053 |
* <p> The value can be retrieved by calling the {@code get} method |
1054 |
* with a key that is equal to the original key. |
1055 |
* |
1056 |
* @param key key with which the specified value is to be associated |
1057 |
* @param value value to be associated with the specified key |
1058 |
* @return the previous value associated with {@code key}, or |
1059 |
* {@code null} if there was no mapping for {@code key} |
1060 |
* @throws NullPointerException if the specified key or value is null |
1061 |
*/ |
1062 |
@SuppressWarnings("unchecked") |
1063 |
public V put(K key, V value) { |
1064 |
if (key == null || value == null) |
1065 |
throw new NullPointerException(); |
1066 |
return (V)internalPut(key, value, true); |
1067 |
} |
1068 |
|
1069 |
/** |
1070 |
* {@inheritDoc} |
1071 |
* |
1072 |
* @return the previous value associated with the specified key, |
1073 |
* or {@code null} if there was no mapping for the key |
1074 |
* @throws NullPointerException if the specified key or value is null |
1075 |
*/ |
1076 |
@SuppressWarnings("unchecked") |
1077 |
public V putIfAbsent(K key, V value) { |
1078 |
if (key == null || value == null) |
1079 |
throw new NullPointerException(); |
1080 |
return (V)internalPut(key, value, false); |
1081 |
} |
1082 |
|
1083 |
/** |
1084 |
* Copies all of the mappings from the specified map to this one. |
1085 |
* These mappings replace any mappings that this map had for any of the |
1086 |
* keys currently in the specified map. |
1087 |
* |
1088 |
* @param m mappings to be stored in this map |
1089 |
*/ |
1090 |
public void putAll(Map<? extends K, ? extends V> m) { |
1091 |
if (m == null) |
1092 |
throw new NullPointerException(); |
1093 |
internalPutAll(m); |
1094 |
} |
1095 |
|
1096 |
/** |
1097 |
* If the specified key is not already associated with a value, |
1098 |
* computes its value using the given mappingFunction, and if |
1099 |
* non-null, enters it into the map. This is equivalent to |
1100 |
* |
1101 |
* <pre> |
1102 |
* if (map.containsKey(key)) |
1103 |
* return map.get(key); |
1104 |
* value = mappingFunction.map(key); |
1105 |
* if (value != null) |
1106 |
* return map.put(key, value); |
1107 |
* else |
1108 |
* return null; |
1109 |
* </pre> |
1110 |
* |
1111 |
* except that the action is performed atomically. Some attempted |
1112 |
* operations on this map by other threads may be blocked while |
1113 |
* computation is in progress. Because this function is invoked |
1114 |
* within atomicity control, the computation should be short and |
1115 |
* simple, and must not attempt to update any other mappings of |
1116 |
* this Map. The most common usage is to construct a new object |
1117 |
* serving as an initial mapped value, or memoized result. |
1118 |
* |
1119 |
* @param key key with which the specified value is to be associated |
1120 |
* @param mappingFunction the function to compute a value |
1121 |
* @return the current (existing or computed) value associated with |
1122 |
* the specified key, or {@code null} if the computation |
1123 |
* returned {@code null}. |
1124 |
* @throws NullPointerException if the specified key or mappingFunction |
1125 |
* is null, |
1126 |
* @throws RuntimeException or Error if the mappingFunction does so, |
1127 |
* in which case the mapping is left unestablished. |
1128 |
*/ |
1129 |
public V computeIfAbsent(K key, MappingFunction<? super K, ? extends V> mappingFunction) { |
1130 |
if (key == null || mappingFunction == null) |
1131 |
throw new NullPointerException(); |
1132 |
return computeVal(key, mappingFunction); |
1133 |
} |
1134 |
|
1135 |
/** |
1136 |
* Removes the key (and its corresponding value) from this map. |
1137 |
* This method does nothing if the key is not in the map. |
1138 |
* |
1139 |
* @param key the key that needs to be removed |
1140 |
* @return the previous value associated with {@code key}, or |
1141 |
* {@code null} if there was no mapping for {@code key} |
1142 |
* @throws NullPointerException if the specified key is null |
1143 |
*/ |
1144 |
@SuppressWarnings("unchecked") |
1145 |
public V remove(Object key) { |
1146 |
if (key == null) |
1147 |
throw new NullPointerException(); |
1148 |
return (V)internalReplace(key, null, null); |
1149 |
} |
1150 |
|
1151 |
/** |
1152 |
* {@inheritDoc} |
1153 |
* |
1154 |
* @throws NullPointerException if the specified key is null |
1155 |
*/ |
1156 |
public boolean remove(Object key, Object value) { |
1157 |
if (key == null) |
1158 |
throw new NullPointerException(); |
1159 |
if (value == null) |
1160 |
return false; |
1161 |
return internalReplace(key, null, value) != null; |
1162 |
} |
1163 |
|
1164 |
/** |
1165 |
* {@inheritDoc} |
1166 |
* |
1167 |
* @throws NullPointerException if any of the arguments are null |
1168 |
*/ |
1169 |
public boolean replace(K key, V oldValue, V newValue) { |
1170 |
if (key == null || oldValue == null || newValue == null) |
1171 |
throw new NullPointerException(); |
1172 |
return internalReplace(key, newValue, oldValue) != null; |
1173 |
} |
1174 |
|
1175 |
/** |
1176 |
* {@inheritDoc} |
1177 |
* |
1178 |
* @return the previous value associated with the specified key, |
1179 |
* or {@code null} if there was no mapping for the key |
1180 |
* @throws NullPointerException if the specified key or value is null |
1181 |
*/ |
1182 |
@SuppressWarnings("unchecked") |
1183 |
public V replace(K key, V value) { |
1184 |
if (key == null || value == null) |
1185 |
throw new NullPointerException(); |
1186 |
return (V)internalReplace(key, value, null); |
1187 |
} |
1188 |
|
1189 |
/** |
1190 |
* Removes all of the mappings from this map. |
1191 |
*/ |
1192 |
public void clear() { |
1193 |
internalClear(); |
1194 |
} |
1195 |
|
1196 |
/** |
1197 |
* Returns a {@link Set} view of the keys contained in this map. |
1198 |
* The set is backed by the map, so changes to the map are |
1199 |
* reflected in the set, and vice-versa. The set supports element |
1200 |
* removal, which removes the corresponding mapping from this map, |
1201 |
* via the {@code Iterator.remove}, {@code Set.remove}, |
1202 |
* {@code removeAll}, {@code retainAll}, and {@code clear} |
1203 |
* operations. It does not support the {@code add} or |
1204 |
* {@code addAll} operations. |
1205 |
* |
1206 |
* <p>The view's {@code iterator} is a "weakly consistent" iterator |
1207 |
* that will never throw {@link ConcurrentModificationException}, |
1208 |
* and guarantees to traverse elements as they existed upon |
1209 |
* construction of the iterator, and may (but is not guaranteed to) |
1210 |
* reflect any modifications subsequent to construction. |
1211 |
*/ |
1212 |
public Set<K> keySet() { |
1213 |
Set<K> ks = keySet; |
1214 |
return (ks != null) ? ks : (keySet = new KeySet()); |
1215 |
} |
1216 |
|
1217 |
/** |
1218 |
* Returns a {@link Collection} view of the values contained in this map. |
1219 |
* The collection is backed by the map, so changes to the map are |
1220 |
* reflected in the collection, and vice-versa. The collection |
1221 |
* supports element removal, which removes the corresponding |
1222 |
* mapping from this map, via the {@code Iterator.remove}, |
1223 |
* {@code Collection.remove}, {@code removeAll}, |
1224 |
* {@code retainAll}, and {@code clear} operations. It does not |
1225 |
* support the {@code add} or {@code addAll} operations. |
1226 |
* |
1227 |
* <p>The view's {@code iterator} is a "weakly consistent" iterator |
1228 |
* that will never throw {@link ConcurrentModificationException}, |
1229 |
* and guarantees to traverse elements as they existed upon |
1230 |
* construction of the iterator, and may (but is not guaranteed to) |
1231 |
* reflect any modifications subsequent to construction. |
1232 |
*/ |
1233 |
public Collection<V> values() { |
1234 |
Collection<V> vs = values; |
1235 |
return (vs != null) ? vs : (values = new Values()); |
1236 |
} |
1237 |
|
1238 |
/** |
1239 |
* Returns a {@link Set} view of the mappings contained in this map. |
1240 |
* The set is backed by the map, so changes to the map are |
1241 |
* reflected in the set, and vice-versa. The set supports element |
1242 |
* removal, which removes the corresponding mapping from the map, |
1243 |
* via the {@code Iterator.remove}, {@code Set.remove}, |
1244 |
* {@code removeAll}, {@code retainAll}, and {@code clear} |
1245 |
* operations. It does not support the {@code add} or |
1246 |
* {@code addAll} operations. |
1247 |
* |
1248 |
* <p>The view's {@code iterator} is a "weakly consistent" iterator |
1249 |
* that will never throw {@link ConcurrentModificationException}, |
1250 |
* and guarantees to traverse elements as they existed upon |
1251 |
* construction of the iterator, and may (but is not guaranteed to) |
1252 |
* reflect any modifications subsequent to construction. |
1253 |
*/ |
1254 |
public Set<Map.Entry<K,V>> entrySet() { |
1255 |
Set<Map.Entry<K,V>> es = entrySet; |
1256 |
return (es != null) ? es : (entrySet = new EntrySet()); |
1257 |
} |
1258 |
|
1259 |
/** |
1260 |
* Returns an enumeration of the keys in this table. |
1261 |
* |
1262 |
* @return an enumeration of the keys in this table |
1263 |
* @see #keySet() |
1264 |
*/ |
1265 |
public Enumeration<K> keys() { |
1266 |
return new KeyIterator(); |
1267 |
} |
1268 |
|
1269 |
/** |
1270 |
* Returns an enumeration of the values in this table. |
1271 |
* |
1272 |
* @return an enumeration of the values in this table |
1273 |
* @see #values() |
1274 |
*/ |
1275 |
public Enumeration<V> elements() { |
1276 |
return new ValueIterator(); |
1277 |
} |
1278 |
|
1279 |
/** |
1280 |
* {@inheritDoc} |
1281 |
*/ |
1282 |
public int hashCode() { |
1283 |
return new HashIterator().mapHashCode(); |
1284 |
} |
1285 |
|
1286 |
/** |
1287 |
* {@inheritDoc} |
1288 |
*/ |
1289 |
public String toString() { |
1290 |
return new HashIterator().mapToString(); |
1291 |
} |
1292 |
|
1293 |
/** |
1294 |
* {@inheritDoc} |
1295 |
*/ |
1296 |
public boolean equals(Object o) { |
1297 |
if (o == this) |
1298 |
return true; |
1299 |
if (!(o instanceof Map)) |
1300 |
return false; |
1301 |
Map<?,?> m = (Map<?,?>) o; |
1302 |
try { |
1303 |
for (Map.Entry<K,V> e : this.entrySet()) |
1304 |
if (! e.getValue().equals(m.get(e.getKey()))) |
1305 |
return false; |
1306 |
for (Map.Entry<?,?> e : m.entrySet()) { |
1307 |
Object k = e.getKey(); |
1308 |
Object v = e.getValue(); |
1309 |
if (k == null || v == null || !v.equals(get(k))) |
1310 |
return false; |
1311 |
} |
1312 |
return true; |
1313 |
} catch (ClassCastException unused) { |
1314 |
return false; |
1315 |
} catch (NullPointerException unused) { |
1316 |
return false; |
1317 |
} |
1318 |
} |
1319 |
|
1320 |
/** |
1321 |
* Custom Entry class used by EntryIterator.next(), that relays |
1322 |
* setValue changes to the underlying map. |
1323 |
*/ |
1324 |
final class WriteThroughEntry extends AbstractMap.SimpleEntry<K,V> { |
1325 |
@SuppressWarnings("unchecked") |
1326 |
WriteThroughEntry(Object k, Object v) { |
1327 |
super((K)k, (V)v); |
1328 |
} |
1329 |
|
1330 |
/** |
1331 |
* Sets our entry's value and writes through to the map. The |
1332 |
* value to return is somewhat arbitrary here. Since a |
1333 |
* WriteThroughEntry does not necessarily track asynchronous |
1334 |
* changes, the most recent "previous" value could be |
1335 |
* different from what we return (or could even have been |
1336 |
* removed in which case the put will re-establish). We do not |
1337 |
* and cannot guarantee more. |
1338 |
*/ |
1339 |
public V setValue(V value) { |
1340 |
if (value == null) throw new NullPointerException(); |
1341 |
V v = super.setValue(value); |
1342 |
ConcurrentHashMapV8.this.put(getKey(), value); |
1343 |
return v; |
1344 |
} |
1345 |
} |
1346 |
|
1347 |
final class KeyIterator extends HashIterator |
1348 |
implements Iterator<K>, Enumeration<K> { |
1349 |
@SuppressWarnings("unchecked") |
1350 |
public final K next() { return (K)super.nextKey(); } |
1351 |
@SuppressWarnings("unchecked") |
1352 |
public final K nextElement() { return (K)super.nextKey(); } |
1353 |
} |
1354 |
|
1355 |
final class ValueIterator extends HashIterator |
1356 |
implements Iterator<V>, Enumeration<V> { |
1357 |
@SuppressWarnings("unchecked") |
1358 |
public final V next() { return (V)super.nextValue(); } |
1359 |
@SuppressWarnings("unchecked") |
1360 |
public final V nextElement() { return (V)super.nextValue(); } |
1361 |
} |
1362 |
|
1363 |
final class EntryIterator extends HashIterator |
1364 |
implements Iterator<Entry<K,V>> { |
1365 |
public final Map.Entry<K,V> next() { return super.nextEntry(); } |
1366 |
} |
1367 |
|
1368 |
final class KeySet extends AbstractSet<K> { |
1369 |
public int size() { |
1370 |
return ConcurrentHashMapV8.this.size(); |
1371 |
} |
1372 |
public boolean isEmpty() { |
1373 |
return ConcurrentHashMapV8.this.isEmpty(); |
1374 |
} |
1375 |
public void clear() { |
1376 |
ConcurrentHashMapV8.this.clear(); |
1377 |
} |
1378 |
public Iterator<K> iterator() { |
1379 |
return new KeyIterator(); |
1380 |
} |
1381 |
public boolean contains(Object o) { |
1382 |
return ConcurrentHashMapV8.this.containsKey(o); |
1383 |
} |
1384 |
public boolean remove(Object o) { |
1385 |
return ConcurrentHashMapV8.this.remove(o) != null; |
1386 |
} |
1387 |
} |
1388 |
|
1389 |
final class Values extends AbstractCollection<V> { |
1390 |
public int size() { |
1391 |
return ConcurrentHashMapV8.this.size(); |
1392 |
} |
1393 |
public boolean isEmpty() { |
1394 |
return ConcurrentHashMapV8.this.isEmpty(); |
1395 |
} |
1396 |
public void clear() { |
1397 |
ConcurrentHashMapV8.this.clear(); |
1398 |
} |
1399 |
public Iterator<V> iterator() { |
1400 |
return new ValueIterator(); |
1401 |
} |
1402 |
public boolean contains(Object o) { |
1403 |
return ConcurrentHashMapV8.this.containsValue(o); |
1404 |
} |
1405 |
} |
1406 |
|
1407 |
final class EntrySet extends AbstractSet<Map.Entry<K,V>> { |
1408 |
public int size() { |
1409 |
return ConcurrentHashMapV8.this.size(); |
1410 |
} |
1411 |
public boolean isEmpty() { |
1412 |
return ConcurrentHashMapV8.this.isEmpty(); |
1413 |
} |
1414 |
public void clear() { |
1415 |
ConcurrentHashMapV8.this.clear(); |
1416 |
} |
1417 |
public Iterator<Map.Entry<K,V>> iterator() { |
1418 |
return new EntryIterator(); |
1419 |
} |
1420 |
public boolean contains(Object o) { |
1421 |
if (!(o instanceof Map.Entry)) |
1422 |
return false; |
1423 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1424 |
V v = ConcurrentHashMapV8.this.get(e.getKey()); |
1425 |
return v != null && v.equals(e.getValue()); |
1426 |
} |
1427 |
public boolean remove(Object o) { |
1428 |
if (!(o instanceof Map.Entry)) |
1429 |
return false; |
1430 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1431 |
return ConcurrentHashMapV8.this.remove(e.getKey(), e.getValue()); |
1432 |
} |
1433 |
} |
1434 |
|
1435 |
/* ---------------- Serialization Support -------------- */ |
1436 |
|
1437 |
/** |
1438 |
* Helper class used in previous version, declared for the sake of |
1439 |
* serialization compatibility |
1440 |
*/ |
1441 |
static class Segment<K,V> extends java.util.concurrent.locks.ReentrantLock |
1442 |
implements Serializable { |
1443 |
private static final long serialVersionUID = 2249069246763182397L; |
1444 |
final float loadFactor; |
1445 |
Segment(float lf) { this.loadFactor = lf; } |
1446 |
} |
1447 |
|
1448 |
/** |
1449 |
* Saves the state of the {@code ConcurrentHashMapV8} instance to a |
1450 |
* stream (i.e., serializes it). |
1451 |
* @param s the stream |
1452 |
* @serialData |
1453 |
* the key (Object) and value (Object) |
1454 |
* for each key-value mapping, followed by a null pair. |
1455 |
* The key-value mappings are emitted in no particular order. |
1456 |
*/ |
1457 |
@SuppressWarnings("unchecked") |
1458 |
private void writeObject(java.io.ObjectOutputStream s) |
1459 |
throws java.io.IOException { |
1460 |
if (segments == null) { // for serialization compatibility |
1461 |
segments = (Segment<K,V>[]) |
1462 |
new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL]; |
1463 |
for (int i = 0; i < segments.length; ++i) |
1464 |
segments[i] = new Segment<K,V>(loadFactor); |
1465 |
} |
1466 |
s.defaultWriteObject(); |
1467 |
new HashIterator().writeEntries(s); |
1468 |
s.writeObject(null); |
1469 |
s.writeObject(null); |
1470 |
segments = null; // throw away |
1471 |
} |
1472 |
|
1473 |
/** |
1474 |
* Reconstitutes the instance from a |
1475 |
* stream (i.e., deserializes it). |
1476 |
* @param s the stream |
1477 |
*/ |
1478 |
@SuppressWarnings("unchecked") |
1479 |
private void readObject(java.io.ObjectInputStream s) |
1480 |
throws java.io.IOException, ClassNotFoundException { |
1481 |
s.defaultReadObject(); |
1482 |
// find load factor in a segment, if one exists |
1483 |
if (segments != null && segments.length != 0) |
1484 |
this.loadFactor = segments[0].loadFactor; |
1485 |
else |
1486 |
this.loadFactor = DEFAULT_LOAD_FACTOR; |
1487 |
this.initCap = DEFAULT_CAPACITY; |
1488 |
LongAdder ct = new LongAdder(); // force final field write |
1489 |
UNSAFE.putObjectVolatile(this, counterOffset, ct); |
1490 |
this.segments = null; // unneeded |
1491 |
|
1492 |
// Read the keys and values, and put the mappings in the table |
1493 |
for (;;) { |
1494 |
K key = (K) s.readObject(); |
1495 |
V value = (V) s.readObject(); |
1496 |
if (key == null) |
1497 |
break; |
1498 |
put(key, value); |
1499 |
} |
1500 |
} |
1501 |
|
1502 |
// Unsafe mechanics |
1503 |
private static final sun.misc.Unsafe UNSAFE; |
1504 |
private static final long counterOffset; |
1505 |
private static final long resizingOffset; |
1506 |
private static final long ABASE; |
1507 |
private static final int ASHIFT; |
1508 |
|
1509 |
static { |
1510 |
int ss; |
1511 |
try { |
1512 |
UNSAFE = getUnsafe(); |
1513 |
Class<?> k = ConcurrentHashMapV8.class; |
1514 |
counterOffset = UNSAFE.objectFieldOffset |
1515 |
(k.getDeclaredField("counter")); |
1516 |
resizingOffset = UNSAFE.objectFieldOffset |
1517 |
(k.getDeclaredField("resizing")); |
1518 |
Class<?> sc = Node[].class; |
1519 |
ABASE = UNSAFE.arrayBaseOffset(sc); |
1520 |
ss = UNSAFE.arrayIndexScale(sc); |
1521 |
} catch (Exception e) { |
1522 |
throw new Error(e); |
1523 |
} |
1524 |
if ((ss & (ss-1)) != 0) |
1525 |
throw new Error("data type scale not a power of two"); |
1526 |
ASHIFT = 31 - Integer.numberOfLeadingZeros(ss); |
1527 |
} |
1528 |
|
1529 |
/** |
1530 |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1531 |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1532 |
* into a jdk. |
1533 |
* |
1534 |
* @return a sun.misc.Unsafe |
1535 |
*/ |
1536 |
private static sun.misc.Unsafe getUnsafe() { |
1537 |
try { |
1538 |
return sun.misc.Unsafe.getUnsafe(); |
1539 |
} catch (SecurityException se) { |
1540 |
try { |
1541 |
return java.security.AccessController.doPrivileged |
1542 |
(new java.security |
1543 |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1544 |
public sun.misc.Unsafe run() throws Exception { |
1545 |
java.lang.reflect.Field f = sun.misc |
1546 |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1547 |
f.setAccessible(true); |
1548 |
return (sun.misc.Unsafe) f.get(null); |
1549 |
}}); |
1550 |
} catch (java.security.PrivilegedActionException e) { |
1551 |
throw new RuntimeException("Could not initialize intrinsics", |
1552 |
e.getCause()); |
1553 |
} |
1554 |
} |
1555 |
} |
1556 |
|
1557 |
} |