| /* |
| * Written by Doug Lea with assistance from members of JCP JSR-166 |
| * Expert Group and released to the public domain, as explained at |
| * http://creativecommons.org/publicdomain/zero/1.0/ |
| */ |
| |
| package java.util.concurrent; |
| |
| import java.io.ObjectStreamField; |
| import java.io.Serializable; |
| import java.lang.reflect.ParameterizedType; |
| import java.lang.reflect.Type; |
| import java.util.AbstractMap; |
| import java.util.Arrays; |
| import java.util.Collection; |
| import java.util.ConcurrentModificationException; |
| import java.util.Enumeration; |
| import java.util.HashMap; |
| import java.util.Hashtable; |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.NoSuchElementException; |
| import java.util.Set; |
| import java.util.concurrent.ConcurrentMap; |
| import java.util.concurrent.atomic.AtomicInteger; |
| import java.util.concurrent.locks.LockSupport; |
| import java.util.concurrent.locks.ReentrantLock; |
| |
| // BEGIN android-note |
| // removed link to collections framework docs |
| // removed links to hidden api |
| // END android-note |
| |
| /** |
| * A hash table supporting full concurrency of retrievals and |
| * high expected concurrency for updates. This class obeys the |
| * same functional specification as {@link java.util.Hashtable}, and |
| * includes versions of methods corresponding to each method of |
| * {@code Hashtable}. However, even though all operations are |
| * thread-safe, retrieval operations do <em>not</em> entail locking, |
| * and there is <em>not</em> any support for locking the entire table |
| * in a way that prevents all access. This class is fully |
| * interoperable with {@code Hashtable} in programs that rely on its |
| * thread safety but not on its synchronization details. |
| * |
| * <p>Retrieval operations (including {@code get}) generally do not |
| * block, so may overlap with update operations (including {@code put} |
| * and {@code remove}). Retrievals reflect the results of the most |
| * recently <em>completed</em> update operations holding upon their |
| * onset. (More formally, an update operation for a given key bears a |
| * <em>happens-before</em> relation with any (non-null) retrieval for |
| * that key reporting the updated value.) For aggregate operations |
| * such as {@code putAll} and {@code clear}, concurrent retrievals may |
| * reflect insertion or removal of only some entries. Similarly, |
| * Iterators and Enumerations return elements reflecting the state of |
| * the hash table at some point at or since the creation of the |
| * iterator/enumeration. They do <em>not</em> throw {@link |
| * ConcurrentModificationException}. However, iterators are designed |
| * to be used by only one thread at a time. Bear in mind that the |
| * results of aggregate status methods including {@code size}, {@code |
| * isEmpty}, and {@code containsValue} are typically useful only when |
| * a map is not undergoing concurrent updates in other threads. |
| * Otherwise the results of these methods reflect transient states |
| * that may be adequate for monitoring or estimation purposes, but not |
| * for program control. |
| * |
| * <p>The table is dynamically expanded when there are too many |
| * collisions (i.e., keys that have distinct hash codes but fall into |
| * the same slot modulo the table size), with the expected average |
| * effect of maintaining roughly two bins per mapping (corresponding |
| * to a 0.75 load factor threshold for resizing). There may be much |
| * variance around this average as mappings are added and removed, but |
| * overall, this maintains a commonly accepted time/space tradeoff for |
| * hash tables. However, resizing this or any other kind of hash |
| * table may be a relatively slow operation. When possible, it is a |
| * good idea to provide a size estimate as an optional {@code |
| * initialCapacity} constructor argument. An additional optional |
| * {@code loadFactor} constructor argument provides a further means of |
| * customizing initial table capacity by specifying the table density |
| * to be used in calculating the amount of space to allocate for the |
| * given number of elements. Also, for compatibility with previous |
| * versions of this class, constructors may optionally specify an |
| * expected {@code concurrencyLevel} as an additional hint for |
| * internal sizing. Note that using many keys with exactly the same |
| * {@code hashCode()} is a sure way to slow down performance of any |
| * hash table. To ameliorate impact, when keys are {@link Comparable}, |
| * this class may use comparison order among keys to help break ties. |
| * |
| * <p>This class and its views and iterators implement all of the |
| * <em>optional</em> methods of the {@link Map} and {@link Iterator} |
| * interfaces. |
| * |
| * <p>Like {@link Hashtable} but unlike {@link HashMap}, this class |
| * does <em>not</em> allow {@code null} to be used as a key or value. |
| * |
| * @since 1.5 |
| * @author Doug Lea |
| * @param <K> the type of keys maintained by this map |
| * @param <V> the type of mapped values |
| */ |
| // android-note: removed documentation about hidden newKeySet and newKeySet(int) APIs. |
| // android-note: Added "extends AbstractMap<K, V>. |
| public class ConcurrentHashMap<K,V> extends AbstractMap<K, V> |
| implements ConcurrentMap<K,V>, Serializable { |
| private static final long serialVersionUID = 7249069246763182397L; |
| |
| /* |
| * Overview: |
| * |
| * The primary design goal of this hash table is to maintain |
| * concurrent readability (typically method get(), but also |
| * iterators and related methods) while minimizing update |
| * contention. Secondary goals are to keep space consumption about |
| * the same or better than java.util.HashMap, and to support high |
| * initial insertion rates on an empty table by many threads. |
| * |
| * This map usually acts as a binned (bucketed) hash table. Each |
| * key-value mapping is held in a Node. Most nodes are instances |
| * of the basic Node class with hash, key, value, and next |
| * fields. However, various subclasses exist: TreeNodes are |
| * arranged in balanced trees, not lists. TreeBins hold the roots |
| * of sets of TreeNodes. ForwardingNodes are placed at the heads |
| * of bins during resizing. ReservationNodes are used as |
| * placeholders while establishing values in computeIfAbsent and |
| * related methods. The types TreeBin, ForwardingNode, and |
| * ReservationNode do not hold normal user keys, values, or |
| * hashes, and are readily distinguishable during search etc |
| * because they have negative hash fields and null key and value |
| * fields. (These special nodes are either uncommon or transient, |
| * so the impact of carrying around some unused fields is |
| * insignificant.) |
| * |
| * The table is lazily initialized to a power-of-two size upon the |
| * first insertion. Each bin in the table normally contains a |
| * list of Nodes (most often, the list has only zero or one Node). |
| * Table accesses require volatile/atomic reads, writes, and |
| * CASes. Because there is no other way to arrange this without |
| * adding further indirections, we use intrinsics |
| * (sun.misc.Unsafe) operations. |
| * |
| * We use the top (sign) bit of Node hash fields for control |
| * purposes -- it is available anyway because of addressing |
| * constraints. Nodes with negative hash fields are specially |
| * handled or ignored in map methods. |
| * |
| * Insertion (via put or its variants) of the first node in an |
| * empty bin is performed by just CASing it to the bin. This is |
| * by far the most common case for put operations under most |
| * key/hash distributions. Other update operations (insert, |
| * delete, and replace) require locks. We do not want to waste |
| * the space required to associate a distinct lock object with |
| * each bin, so instead use the first node of a bin list itself as |
| * a lock. Locking support for these locks relies on builtin |
| * "synchronized" monitors. |
| * |
| * Using the first node of a list as a lock does not by itself |
| * suffice though: When a node is locked, any update must first |
| * validate that it is still the first node after locking it, and |
| * retry if not. Because new nodes are always appended to lists, |
| * once a node is first in a bin, it remains first until deleted |
| * or the bin becomes invalidated (upon resizing). |
| * |
| * The main disadvantage of per-bin locks is that other update |
| * operations on other nodes in a bin list protected by the same |
| * lock can stall, for example when user equals() or mapping |
| * functions take a long time. However, statistically, under |
| * random hash codes, this is not a common problem. Ideally, the |
| * frequency of nodes in bins follows a Poisson distribution |
| * (http://en.wikipedia.org/wiki/Poisson_distribution) with a |
| * parameter of about 0.5 on average, given the resizing threshold |
| * of 0.75, although with a large variance because of resizing |
| * granularity. Ignoring variance, the expected occurrences of |
| * list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The |
| * first values are: |
| * |
| * 0: 0.60653066 |
| * 1: 0.30326533 |
| * 2: 0.07581633 |
| * 3: 0.01263606 |
| * 4: 0.00157952 |
| * 5: 0.00015795 |
| * 6: 0.00001316 |
| * 7: 0.00000094 |
| * 8: 0.00000006 |
| * more: less than 1 in ten million |
| * |
| * Lock contention probability for two threads accessing distinct |
| * elements is roughly 1 / (8 * #elements) under random hashes. |
| * |
| * Actual hash code distributions encountered in practice |
| * sometimes deviate significantly from uniform randomness. This |
| * includes the case when N > (1<<30), so some keys MUST collide. |
| * Similarly for dumb or hostile usages in which multiple keys are |
| * designed to have identical hash codes or ones that differs only |
| * in masked-out high bits. So we use a secondary strategy that |
| * applies when the number of nodes in a bin exceeds a |
| * threshold. These TreeBins use a balanced tree to hold nodes (a |
| * specialized form of red-black trees), bounding search time to |
| * O(log N). Each search step in a TreeBin is at least twice as |
| * slow as in a regular list, but given that N cannot exceed |
| * (1<<64) (before running out of addresses) this bounds search |
| * steps, lock hold times, etc, to reasonable constants (roughly |
| * 100 nodes inspected per operation worst case) so long as keys |
| * are Comparable (which is very common -- String, Long, etc). |
| * TreeBin nodes (TreeNodes) also maintain the same "next" |
| * traversal pointers as regular nodes, so can be traversed in |
| * iterators in the same way. |
| * |
| * The table is resized when occupancy exceeds a percentage |
| * threshold (nominally, 0.75, but see below). Any thread |
| * noticing an overfull bin may assist in resizing after the |
| * initiating thread allocates and sets up the replacement array. |
| * However, rather than stalling, these other threads may proceed |
| * with insertions etc. The use of TreeBins shields us from the |
| * worst case effects of overfilling while resizes are in |
| * progress. Resizing proceeds by transferring bins, one by one, |
| * from the table to the next table. However, threads claim small |
| * blocks of indices to transfer (via field transferIndex) before |
| * doing so, reducing contention. A generation stamp in field |
| * sizeCtl ensures that resizings do not overlap. Because we are |
| * using power-of-two expansion, the elements from each bin must |
| * either stay at same index, or move with a power of two |
| * offset. We eliminate unnecessary node creation by catching |
| * cases where old nodes can be reused because their next fields |
| * won't change. On average, only about one-sixth of them need |
| * cloning when a table doubles. The nodes they replace will be |
| * garbage collectable as soon as they are no longer referenced by |
| * any reader thread that may be in the midst of concurrently |
| * traversing table. Upon transfer, the old table bin contains |
| * only a special forwarding node (with hash field "MOVED") that |
| * contains the next table as its key. On encountering a |
| * forwarding node, access and update operations restart, using |
| * the new table. |
| * |
| * Each bin transfer requires its bin lock, which can stall |
| * waiting for locks while resizing. However, because other |
| * threads can join in and help resize rather than contend for |
| * locks, average aggregate waits become shorter as resizing |
| * progresses. The transfer operation must also ensure that all |
| * accessible bins in both the old and new table are usable by any |
| * traversal. This is arranged in part by proceeding from the |
| * last bin (table.length - 1) up towards the first. Upon seeing |
| * a forwarding node, traversals (see class Traverser) arrange to |
| * move to the new table without revisiting nodes. To ensure that |
| * no intervening nodes are skipped even when moved out of order, |
| * a stack (see class TableStack) is created on first encounter of |
| * a forwarding node during a traversal, to maintain its place if |
| * later processing the current table. The need for these |
| * save/restore mechanics is relatively rare, but when one |
| * forwarding node is encountered, typically many more will be. |
| * So Traversers use a simple caching scheme to avoid creating so |
| * many new TableStack nodes. (Thanks to Peter Levart for |
| * suggesting use of a stack here.) |
| * |
| * The traversal scheme also applies to partial traversals of |
| * ranges of bins (via an alternate Traverser constructor) |
| * to support partitioned aggregate operations. Also, read-only |
| * operations give up if ever forwarded to a null table, which |
| * provides support for shutdown-style clearing, which is also not |
| * currently implemented. |
| * |
| * Lazy table initialization minimizes footprint until first use, |
| * and also avoids resizings when the first operation is from a |
| * putAll, constructor with map argument, or deserialization. |
| * These cases attempt to override the initial capacity settings, |
| * but harmlessly fail to take effect in cases of races. |
| * |
| * The element count is maintained using a specialization of |
| * LongAdder. We need to incorporate a specialization rather than |
| * just use a LongAdder in order to access implicit |
| * contention-sensing that leads to creation of multiple |
| * CounterCells. The counter mechanics avoid contention on |
| * updates but can encounter cache thrashing if read too |
| * frequently during concurrent access. To avoid reading so often, |
| * resizing under contention is attempted only upon adding to a |
| * bin already holding two or more nodes. Under uniform hash |
| * distributions, the probability of this occurring at threshold |
| * is around 13%, meaning that only about 1 in 8 puts check |
| * threshold (and after resizing, many fewer do so). |
| * |
| * TreeBins use a special form of comparison for search and |
| * related operations (which is the main reason we cannot use |
| * existing collections such as TreeMaps). TreeBins contain |
| * Comparable elements, but may contain others, as well as |
| * elements that are Comparable but not necessarily Comparable for |
| * the same T, so we cannot invoke compareTo among them. To handle |
| * this, the tree is ordered primarily by hash value, then by |
| * Comparable.compareTo order if applicable. On lookup at a node, |
| * if elements are not comparable or compare as 0 then both left |
| * and right children may need to be searched in the case of tied |
| * hash values. (This corresponds to the full list search that |
| * would be necessary if all elements were non-Comparable and had |
| * tied hashes.) On insertion, to keep a total ordering (or as |
| * close as is required here) across rebalancings, we compare |
| * classes and identityHashCodes as tie-breakers. The red-black |
| * balancing code is updated from pre-jdk-collections |
| * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java) |
| * based in turn on Cormen, Leiserson, and Rivest "Introduction to |
| * Algorithms" (CLR). |
| * |
| * TreeBins also require an additional locking mechanism. While |
| * list traversal is always possible by readers even during |
| * updates, tree traversal is not, mainly because of tree-rotations |
| * that may change the root node and/or its linkages. TreeBins |
| * include a simple read-write lock mechanism parasitic on the |
| * main bin-synchronization strategy: Structural adjustments |
| * associated with an insertion or removal are already bin-locked |
| * (and so cannot conflict with other writers) but must wait for |
| * ongoing readers to finish. Since there can be only one such |
| * waiter, we use a simple scheme using a single "waiter" field to |
| * block writers. However, readers need never block. If the root |
| * lock is held, they proceed along the slow traversal path (via |
| * next-pointers) until the lock becomes available or the list is |
| * exhausted, whichever comes first. These cases are not fast, but |
| * maximize aggregate expected throughput. |
| * |
| * Maintaining API and serialization compatibility with previous |
| * versions of this class introduces several oddities. Mainly: We |
| * leave untouched but unused constructor arguments refering to |
| * concurrencyLevel. We accept a loadFactor constructor argument, |
| * but apply it only to initial table capacity (which is the only |
| * time that we can guarantee to honor it.) We also declare an |
| * unused "Segment" class that is instantiated in minimal form |
| * only when serializing. |
| * |
| * Also, solely for compatibility with previous versions of this |
| * class, it extends AbstractMap, even though all of its methods |
| * are overridden, so it is just useless baggage. |
| * |
| * This file is organized to make things a little easier to follow |
| * while reading than they might otherwise: First the main static |
| * declarations and utilities, then fields, then main public |
| * methods (with a few factorings of multiple public methods into |
| * internal ones), then sizing methods, trees, traversers, and |
| * bulk operations. |
| */ |
| |
| |
| /* ---------------- Constants -------------- */ |
| |
| /** |
| * The largest possible table capacity. This value must be |
| * exactly 1<<30 to stay within Java array allocation and indexing |
| * bounds for power of two table sizes, and is further required |
| * because the top two bits of 32bit hash fields are used for |
| * control purposes. |
| */ |
| private static final int MAXIMUM_CAPACITY = 1 << 30; |
| |
| /** |
| * The default initial table capacity. Must be a power of 2 |
| * (i.e., at least 1) and at most MAXIMUM_CAPACITY. |
| */ |
| private static final int DEFAULT_CAPACITY = 16; |
| |
| /** |
| * The largest possible (non-power of two) array size. |
| * Needed by toArray and related methods. |
| */ |
| static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
| |
| /** |
| * The default concurrency level for this table. Unused but |
| * defined for compatibility with previous versions of this class. |
| */ |
| private static final int DEFAULT_CONCURRENCY_LEVEL = 16; |
| |
| /** |
| * The load factor for this table. Overrides of this value in |
| * constructors affect only the initial table capacity. The |
| * actual floating point value isn't normally used -- it is |
| * simpler to use expressions such as {@code n - (n >>> 2)} for |
| * the associated resizing threshold. |
| */ |
| private static final float LOAD_FACTOR = 0.75f; |
| |
| /** |
| * The bin count threshold for using a tree rather than list for a |
| * bin. Bins are converted to trees when adding an element to a |
| * bin with at least this many nodes. The value must be greater |
| * than 2, and should be at least 8 to mesh with assumptions in |
| * tree removal about conversion back to plain bins upon |
| * shrinkage. |
| */ |
| static final int TREEIFY_THRESHOLD = 8; |
| |
| /** |
| * The bin count threshold for untreeifying a (split) bin during a |
| * resize operation. Should be less than TREEIFY_THRESHOLD, and at |
| * most 6 to mesh with shrinkage detection under removal. |
| */ |
| static final int UNTREEIFY_THRESHOLD = 6; |
| |
| /** |
| * The smallest table capacity for which bins may be treeified. |
| * (Otherwise the table is resized if too many nodes in a bin.) |
| * The value should be at least 4 * TREEIFY_THRESHOLD to avoid |
| * conflicts between resizing and treeification thresholds. |
| */ |
| static final int MIN_TREEIFY_CAPACITY = 64; |
| |
| /** |
| * Minimum number of rebinnings per transfer step. Ranges are |
| * subdivided to allow multiple resizer threads. This value |
| * serves as a lower bound to avoid resizers encountering |
| * excessive memory contention. The value should be at least |
| * DEFAULT_CAPACITY. |
| */ |
| private static final int MIN_TRANSFER_STRIDE = 16; |
| |
| /** |
| * The number of bits used for generation stamp in sizeCtl. |
| * Must be at least 6 for 32bit arrays. |
| */ |
| private static int RESIZE_STAMP_BITS = 16; |
| |
| /** |
| * The maximum number of threads that can help resize. |
| * Must fit in 32 - RESIZE_STAMP_BITS bits. |
| */ |
| private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1; |
| |
| /** |
| * The bit shift for recording size stamp in sizeCtl. |
| */ |
| private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS; |
| |
| /* |
| * Encodings for Node hash fields. See above for explanation. |
| */ |
| static final int MOVED = 0x8fffffff; // (-1) hash for forwarding nodes |
| static final int TREEBIN = 0x80000000; // hash for roots of trees |
| static final int RESERVED = 0x80000001; // hash for transient reservations |
| static final int HASH_BITS = 0x7fffffff; // usable bits of normal node hash |
| |
| /** Number of CPUS, to place bounds on some sizings */ |
| static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| |
| /** For serialization compatibility. */ |
| private static final ObjectStreamField[] serialPersistentFields = { |
| new ObjectStreamField("segments", Segment[].class), |
| new ObjectStreamField("segmentMask", Integer.TYPE), |
| new ObjectStreamField("segmentShift", Integer.TYPE) |
| }; |
| |
| /* ---------------- Nodes -------------- */ |
| |
| /** |
| * Key-value entry. This class is never exported out as a |
| * user-mutable Map.Entry (i.e., one supporting setValue; see |
| * MapEntry below), but can be used for read-only traversals used |
| * in bulk tasks. Subclasses of Node with a negative hash field |
| * are special, and contain null keys and values (but are never |
| * exported). Otherwise, keys and vals are never null. |
| */ |
| static class Node<K,V> implements Map.Entry<K,V> { |
| final int hash; |
| final K key; |
| volatile V val; |
| Node<K,V> next; |
| |
| Node(int hash, K key, V val, Node<K,V> next) { |
| this.hash = hash; |
| this.key = key; |
| this.val = val; |
| this.next = next; |
| } |
| |
| public final K getKey() { return key; } |
| public final V getValue() { return val; } |
| public final int hashCode() { return key.hashCode() ^ val.hashCode(); } |
| public final String toString(){ return key + "=" + val; } |
| public final V setValue(V value) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public final boolean equals(Object o) { |
| Object k, v, u; Map.Entry<?,?> e; |
| return ((o instanceof Map.Entry) && |
| (k = (e = (Map.Entry<?,?>)o).getKey()) != null && |
| (v = e.getValue()) != null && |
| (k == key || k.equals(key)) && |
| (v == (u = val) || v.equals(u))); |
| } |
| |
| /** |
| * Virtualized support for map.get(); overridden in subclasses. |
| */ |
| Node<K,V> find(int h, Object k) { |
| Node<K,V> e = this; |
| if (k != null) { |
| do { |
| K ek; |
| if (e.hash == h && |
| ((ek = e.key) == k || (ek != null && k.equals(ek)))) |
| return e; |
| } while ((e = e.next) != null); |
| } |
| return null; |
| } |
| } |
| |
| /* ---------------- Static utilities -------------- */ |
| |
| /** |
| * Spreads (XORs) higher bits of hash to lower and also forces top |
| * bit to 0. Because the table uses power-of-two masking, sets of |
| * hashes that vary only in bits above the current mask will |
| * always collide. (Among known examples are sets of Float keys |
| * holding consecutive whole numbers in small tables.) So we |
| * apply a transform that spreads the impact of higher bits |
| * downward. There is a tradeoff between speed, utility, and |
| * quality of bit-spreading. Because many common sets of hashes |
| * are already reasonably distributed (so don't benefit from |
| * spreading), and because we use trees to handle large sets of |
| * collisions in bins, we just XOR some shifted bits in the |
| * cheapest possible way to reduce systematic lossage, as well as |
| * to incorporate impact of the highest bits that would otherwise |
| * never be used in index calculations because of table bounds. |
| */ |
| static final int spread(int h) { |
| return (h ^ (h >>> 16)) & HASH_BITS; |
| } |
| |
| /** |
| * Returns a power of two table size for the given desired capacity. |
| * See Hackers Delight, sec 3.2 |
| */ |
| private static final int tableSizeFor(int c) { |
| int n = c - 1; |
| n |= n >>> 1; |
| n |= n >>> 2; |
| n |= n >>> 4; |
| n |= n >>> 8; |
| n |= n >>> 16; |
| return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1; |
| } |
| |
| /** |
| * Returns x's Class if it is of the form "class C implements |
| * Comparable<C>", else null. |
| */ |
| static Class<?> comparableClassFor(Object x) { |
| if (x instanceof Comparable) { |
| Class<?> c; Type[] ts, as; Type t; ParameterizedType p; |
| if ((c = x.getClass()) == String.class) // bypass checks |
| return c; |
| if ((ts = c.getGenericInterfaces()) != null) { |
| for (int i = 0; i < ts.length; ++i) { |
| if (((t = ts[i]) instanceof ParameterizedType) && |
| ((p = (ParameterizedType)t).getRawType() == |
| Comparable.class) && |
| (as = p.getActualTypeArguments()) != null && |
| as.length == 1 && as[0] == c) // type arg is c |
| return c; |
| } |
| } |
| } |
| return null; |
| } |
| |
| /** |
| * Returns k.compareTo(x) if x matches kc (k's screened comparable |
| * class), else 0. |
| */ |
| @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable |
| static int compareComparables(Class<?> kc, Object k, Object x) { |
| return (x == null || x.getClass() != kc ? 0 : |
| ((Comparable)k).compareTo(x)); |
| } |
| |
| /* ---------------- Table element access -------------- */ |
| |
| /* |
| * Volatile access methods are used for table elements as well as |
| * elements of in-progress next table while resizing. All uses of |
| * the tab arguments must be null checked by callers. All callers |
| * also paranoically precheck that tab's length is not zero (or an |
| * equivalent check), thus ensuring that any index argument taking |
| * the form of a hash value anded with (length - 1) is a valid |
| * index. Note that, to be correct wrt arbitrary concurrency |
| * errors by users, these checks must operate on local variables, |
| * which accounts for some odd-looking inline assignments below. |
| * Note that calls to setTabAt always occur within locked regions, |
| * and so do not need full volatile semantics, but still require |
| * ordering to maintain concurrent readability. |
| */ |
| |
| @SuppressWarnings("unchecked") |
| static final <K,V> Node<K,V> tabAt(Node<K,V>[] tab, int i) { |
| return (Node<K,V>)U.getObjectVolatile(tab, ((long)i << ASHIFT) + ABASE); |
| } |
| |
| static final <K,V> boolean casTabAt(Node<K,V>[] tab, int i, |
| Node<K,V> c, Node<K,V> v) { |
| return U.compareAndSwapObject(tab, ((long)i << ASHIFT) + ABASE, c, v); |
| } |
| |
| static final <K,V> void setTabAt(Node<K,V>[] tab, int i, Node<K,V> v) { |
| U.putOrderedObject(tab, ((long)i << ASHIFT) + ABASE, v); |
| } |
| |
| /* ---------------- Fields -------------- */ |
| |
| /** |
| * The array of bins. Lazily initialized upon first insertion. |
| * Size is always a power of two. Accessed directly by iterators. |
| */ |
| transient volatile Node<K,V>[] table; |
| |
| /** |
| * The next table to use; non-null only while resizing. |
| */ |
| private transient volatile Node<K,V>[] nextTable; |
| |
| /** |
| * Base counter value, used mainly when there is no contention, |
| * but also as a fallback during table initialization |
| * races. Updated via CAS. |
| */ |
| private transient volatile long baseCount; |
| |
| /** |
| * Table initialization and resizing control. When negative, the |
| * table is being initialized or resized: -1 for initialization, |
| * else -(1 + the number of active resizing threads). Otherwise, |
| * when table is null, holds the initial table size to use upon |
| * creation, or 0 for default. After initialization, holds the |
| * next element count value upon which to resize the table. |
| */ |
| private transient volatile int sizeCtl; |
| |
| /** |
| * The next table index (plus one) to split while resizing. |
| */ |
| private transient volatile int transferIndex; |
| |
| /** |
| * Spinlock (locked via CAS) used when resizing and/or creating CounterCells. |
| */ |
| private transient volatile int cellsBusy; |
| |
| /** |
| * Table of counter cells. When non-null, size is a power of 2. |
| */ |
| private transient volatile CounterCell[] counterCells; |
| |
| // views |
| private transient KeySetView<K,V> keySet; |
| private transient ValuesView<K,V> values; |
| private transient EntrySetView<K,V> entrySet; |
| |
| |
| /* ---------------- Public operations -------------- */ |
| |
| /** |
| * Creates a new, empty map with the default initial table size (16). |
| */ |
| public ConcurrentHashMap() { |
| } |
| |
| /** |
| * Creates a new, empty map with an initial table size |
| * accommodating the specified number of elements without the need |
| * to dynamically resize. |
| * |
| * @param initialCapacity The implementation performs internal |
| * sizing to accommodate this many elements. |
| * @throws IllegalArgumentException if the initial capacity of |
| * elements is negative |
| */ |
| public ConcurrentHashMap(int initialCapacity) { |
| if (initialCapacity < 0) |
| throw new IllegalArgumentException(); |
| int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ? |
| MAXIMUM_CAPACITY : |
| tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1)); |
| this.sizeCtl = cap; |
| } |
| |
| /** |
| * Creates a new map with the same mappings as the given map. |
| * |
| * @param m the map |
| */ |
| public ConcurrentHashMap(Map<? extends K, ? extends V> m) { |
| this.sizeCtl = DEFAULT_CAPACITY; |
| putAll(m); |
| } |
| |
| /** |
| * Creates a new, empty map with an initial table size based on |
| * the given number of elements ({@code initialCapacity}) and |
| * initial table density ({@code loadFactor}). |
| * |
| * @param initialCapacity the initial capacity. The implementation |
| * performs internal sizing to accommodate this many elements, |
| * given the specified load factor. |
| * @param loadFactor the load factor (table density) for |
| * establishing the initial table size |
| * @throws IllegalArgumentException if the initial capacity of |
| * elements is negative or the load factor is nonpositive |
| * |
| * @since 1.6 |
| */ |
| public ConcurrentHashMap(int initialCapacity, float loadFactor) { |
| this(initialCapacity, loadFactor, 1); |
| } |
| |
| /** |
| * Creates a new, empty map with an initial table size based on |
| * the given number of elements ({@code initialCapacity}), table |
| * density ({@code loadFactor}), and number of concurrently |
| * updating threads ({@code concurrencyLevel}). |
| * |
| * @param initialCapacity the initial capacity. The implementation |
| * performs internal sizing to accommodate this many elements, |
| * given the specified load factor. |
| * @param loadFactor the load factor (table density) for |
| * establishing the initial table size |
| * @param concurrencyLevel the estimated number of concurrently |
| * updating threads. The implementation may use this value as |
| * a sizing hint. |
| * @throws IllegalArgumentException if the initial capacity is |
| * negative or the load factor or concurrencyLevel are |
| * nonpositive |
| */ |
| public ConcurrentHashMap(int initialCapacity, |
| float loadFactor, int concurrencyLevel) { |
| if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0) |
| throw new IllegalArgumentException(); |
| if (initialCapacity < concurrencyLevel) // Use at least as many bins |
| initialCapacity = concurrencyLevel; // as estimated threads |
| long size = (long)(1.0 + (long)initialCapacity / loadFactor); |
| int cap = (size >= (long)MAXIMUM_CAPACITY) ? |
| MAXIMUM_CAPACITY : tableSizeFor((int)size); |
| this.sizeCtl = cap; |
| } |
| |
| // Original (since JDK1.2) Map methods |
| |
| /** |
| * {@inheritDoc} |
| */ |
| public int size() { |
| long n = sumCount(); |
| return ((n < 0L) ? 0 : |
| (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE : |
| (int)n); |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| public boolean isEmpty() { |
| return sumCount() <= 0L; // ignore transient negative values |
| } |
| |
| /** |
| * Returns the value to which the specified key is mapped, |
| * or {@code null} if this map contains no mapping for the key. |
| * |
| * <p>More formally, if this map contains a mapping from a key |
| * {@code k} to a value {@code v} such that {@code key.equals(k)}, |
| * then this method returns {@code v}; otherwise it returns |
| * {@code null}. (There can be at most one such mapping.) |
| * |
| * @throws NullPointerException if the specified key is null |
| */ |
| public V get(Object key) { |
| Node<K,V>[] tab; Node<K,V> e, p; int n, eh; K ek; |
| int h = spread(key.hashCode()); |
| if ((tab = table) != null && (n = tab.length) > 0 && |
| (e = tabAt(tab, (n - 1) & h)) != null) { |
| if ((eh = e.hash) == h) { |
| if ((ek = e.key) == key || (ek != null && key.equals(ek))) |
| return e.val; |
| } |
| else if (eh < 0) |
| return (p = e.find(h, key)) != null ? p.val : null; |
| while ((e = e.next) != null) { |
| if (e.hash == h && |
| ((ek = e.key) == key || (ek != null && key.equals(ek)))) |
| return e.val; |
| } |
| } |
| return null; |
| } |
| |
| /** |
| * Tests if the specified object is a key in this table. |
| * |
| * @param key possible key |
| * @return {@code true} if and only if the specified object |
| * is a key in this table, as determined by the |
| * {@code equals} method; {@code false} otherwise |
| * @throws NullPointerException if the specified key is null |
| */ |
| public boolean containsKey(Object key) { |
| return get(key) != null; |
| } |
| |
| /** |
| * Returns {@code true} if this map maps one or more keys to the |
| * specified value. Note: This method may require a full traversal |
| * of the map, and is much slower than method {@code containsKey}. |
| * |
| * @param value value whose presence in this map is to be tested |
| * @return {@code true} if this map maps one or more keys to the |
| * specified value |
| * @throws NullPointerException if the specified value is null |
| */ |
| public boolean containsValue(Object value) { |
| if (value == null) |
| throw new NullPointerException(); |
| Node<K,V>[] t; |
| if ((t = table) != null) { |
| Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length); |
| for (Node<K,V> p; (p = it.advance()) != null; ) { |
| V v; |
| if ((v = p.val) == value || (v != null && value.equals(v))) |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Maps the specified key to the specified value in this table. |
| * Neither the key nor the value can be null. |
| * |
| * <p>The value can be retrieved by calling the {@code get} method |
| * with a key that is equal to the original key. |
| * |
| * @param key key with which the specified value is to be associated |
| * @param value value to be associated with the specified key |
| * @return the previous value associated with {@code key}, or |
| * {@code null} if there was no mapping for {@code key} |
| * @throws NullPointerException if the specified key or value is null |
| */ |
| public V put(K key, V value) { |
| return putVal(key, value, false); |
| } |
| |
| /** Implementation for put and putIfAbsent */ |
| final V putVal(K key, V value, boolean onlyIfAbsent) { |
| if (key == null || value == null) throw new NullPointerException(); |
| int hash = spread(key.hashCode()); |
| int binCount = 0; |
| for (Node<K,V>[] tab = table;;) { |
| Node<K,V> f; int n, i, fh; |
| if (tab == null || (n = tab.length) == 0) |
| tab = initTable(); |
| else if ((f = tabAt(tab, i = (n - 1) & hash)) == null) { |
| if (casTabAt(tab, i, null, |
| new Node<K,V>(hash, key, value, null))) |
| break; // no lock when adding to empty bin |
| } |
| else if ((fh = f.hash) == MOVED) |
| tab = helpTransfer(tab, f); |
| else { |
| V oldVal = null; |
| synchronized (f) { |
| if (tabAt(tab, i) == f) { |
| if (fh >= 0) { |
| binCount = 1; |
| for (Node<K,V> e = f;; ++binCount) { |
| K ek; |
| if (e.hash == hash && |
| ((ek = e.key) == key || |
| (ek != null && key.equals(ek)))) { |
| oldVal = e.val; |
| if (!onlyIfAbsent) |
| e.val = value; |
| break; |
| } |
| Node<K,V> pred = e; |
| if ((e = e.next) == null) { |
| pred.next = new Node<K,V>(hash, key, |
| value, null); |
| break; |
| } |
| } |
| } |
| else if (f instanceof TreeBin) { |
| Node<K,V> p; |
| binCount = 2; |
| if ((p = ((TreeBin<K,V>)f).putTreeVal(hash, key, |
| value)) != null) { |
| oldVal = p.val; |
| if (!onlyIfAbsent) |
| p.val = value; |
| } |
| } |
| } |
| } |
| if (binCount != 0) { |
| if (binCount >= TREEIFY_THRESHOLD) |
| treeifyBin(tab, i); |
| if (oldVal != null) |
| return oldVal; |
| break; |
| } |
| } |
| } |
| addCount(1L, binCount); |
| return null; |
| } |
| |
| /** |
| * Copies all of the mappings from the specified map to this one. |
| * These mappings replace any mappings that this map had for any of the |
| * keys currently in the specified map. |
| * |
| * @param m mappings to be stored in this map |
| */ |
| public void putAll(Map<? extends K, ? extends V> m) { |
| tryPresize(m.size()); |
| for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
| putVal(e.getKey(), e.getValue(), false); |
| } |
| |
| /** |
| * Removes the key (and its corresponding value) from this map. |
| * This method does nothing if the key is not in the map. |
| * |
| * @param key the key that needs to be removed |
| * @return the previous value associated with {@code key}, or |
| * {@code null} if there was no mapping for {@code key} |
| * @throws NullPointerException if the specified key is null |
| */ |
| public V remove(Object key) { |
| return replaceNode(key, null, null); |
| } |
| |
| /** |
| * Implementation for the four public remove/replace methods: |
| * Replaces node value with v, conditional upon match of cv if |
| * non-null. If resulting value is null, delete. |
| */ |
| final V replaceNode(Object key, V value, Object cv) { |
| int hash = spread(key.hashCode()); |
| for (Node<K,V>[] tab = table;;) { |
| Node<K,V> f; int n, i, fh; |
| if (tab == null || (n = tab.length) == 0 || |
| (f = tabAt(tab, i = (n - 1) & hash)) == null) |
| break; |
| else if ((fh = f.hash) == MOVED) |
| tab = helpTransfer(tab, f); |
| else { |
| V oldVal = null; |
| boolean validated = false; |
| synchronized (f) { |
| if (tabAt(tab, i) == f) { |
| if (fh >= 0) { |
| validated = true; |
| for (Node<K,V> e = f, pred = null;;) { |
| K ek; |
| if (e.hash == hash && |
| ((ek = e.key) == key || |
| (ek != null && key.equals(ek)))) { |
| V ev = e.val; |
| if (cv == null || cv == ev || |
| (ev != null && cv.equals(ev))) { |
| oldVal = ev; |
| if (value != null) |
| e.val = value; |
| else if (pred != null) |
| pred.next = e.next; |
| else |
| setTabAt(tab, i, e.next); |
| } |
| break; |
| } |
| pred = e; |
| if ((e = e.next) == null) |
| break; |
| } |
| } |
| else if (f instanceof TreeBin) { |
| validated = true; |
| TreeBin<K,V> t = (TreeBin<K,V>)f; |
| TreeNode<K,V> r, p; |
| if ((r = t.root) != null && |
| (p = r.findTreeNode(hash, key, null)) != null) { |
| V pv = p.val; |
| if (cv == null || cv == pv || |
| (pv != null && cv.equals(pv))) { |
| oldVal = pv; |
| if (value != null) |
| p.val = value; |
| else if (t.removeTreeNode(p)) |
| setTabAt(tab, i, untreeify(t.first)); |
| } |
| } |
| } |
| } |
| } |
| if (validated) { |
| if (oldVal != null) { |
| if (value == null) |
| addCount(-1L, -1); |
| return oldVal; |
| } |
| break; |
| } |
| } |
| } |
| return null; |
| } |
| |
| /** |
| * Removes all of the mappings from this map. |
| */ |
| public void clear() { |
| long delta = 0L; // negative number of deletions |
| int i = 0; |
| Node<K,V>[] tab = table; |
| while (tab != null && i < tab.length) { |
| int fh; |
| Node<K,V> f = tabAt(tab, i); |
| if (f == null) |
| ++i; |
| else if ((fh = f.hash) == MOVED) { |
| tab = helpTransfer(tab, f); |
| i = 0; // restart |
| } |
| else { |
| synchronized (f) { |
| if (tabAt(tab, i) == f) { |
| Node<K,V> p = (fh >= 0 ? f : |
| (f instanceof TreeBin) ? |
| ((TreeBin<K,V>)f).first : null); |
| while (p != null) { |
| --delta; |
| p = p.next; |
| } |
| setTabAt(tab, i++, null); |
| } |
| } |
| } |
| } |
| if (delta != 0L) |
| addCount(delta, -1); |
| } |
| |
| /** |
| * Returns a {@link Set} view of the keys contained in this map. |
| * The set is backed by the map, so changes to the map are |
| * reflected in the set, and vice-versa. The set supports element |
| * removal, which removes the corresponding mapping from this map, |
| * via the {@code Iterator.remove}, {@code Set.remove}, |
| * {@code removeAll}, {@code retainAll}, and {@code clear} |
| * operations. It does not support the {@code add} or |
| * {@code addAll} operations. |
| * |
| * <p>The view's {@code iterator} is a "weakly consistent" iterator |
| * that will never throw {@link ConcurrentModificationException}, |
| * and guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not guaranteed to) |
| * reflect any modifications subsequent to construction. |
| * |
| * @return the set view |
| */ |
| // android-note : changed KeySetView<K,V> to Set<K> to maintain API compatibility. |
| public Set<K> keySet() { |
| KeySetView<K,V> ks; |
| return (ks = keySet) != null ? ks : (keySet = new KeySetView<K,V>(this, null)); |
| } |
| |
| /** |
| * Returns a {@link Collection} view of the values contained in this map. |
| * The collection is backed by the map, so changes to the map are |
| * reflected in the collection, and vice-versa. The collection |
| * supports element removal, which removes the corresponding |
| * mapping from this map, via the {@code Iterator.remove}, |
| * {@code Collection.remove}, {@code removeAll}, |
| * {@code retainAll}, and {@code clear} operations. It does not |
| * support the {@code add} or {@code addAll} operations. |
| * |
| * <p>The view's {@code iterator} is a "weakly consistent" iterator |
| * that will never throw {@link ConcurrentModificationException}, |
| * and guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not guaranteed to) |
| * reflect any modifications subsequent to construction. |
| * |
| * @return the collection view |
| */ |
| public Collection<V> values() { |
| ValuesView<K,V> vs; |
| return (vs = values) != null ? vs : (values = new ValuesView<K,V>(this)); |
| } |
| |
| /** |
| * Returns a {@link Set} view of the mappings contained in this map. |
| * The set is backed by the map, so changes to the map are |
| * reflected in the set, and vice-versa. The set supports element |
| * removal, which removes the corresponding mapping from the map, |
| * via the {@code Iterator.remove}, {@code Set.remove}, |
| * {@code removeAll}, {@code retainAll}, and {@code clear} |
| * operations. |
| * |
| * <p>The view's {@code iterator} is a "weakly consistent" iterator |
| * that will never throw {@link ConcurrentModificationException}, |
| * and guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not guaranteed to) |
| * reflect any modifications subsequent to construction. |
| * |
| * @return the set view |
| */ |
| public Set<Map.Entry<K,V>> entrySet() { |
| EntrySetView<K,V> es; |
| return (es = entrySet) != null ? es : (entrySet = new EntrySetView<K,V>(this)); |
| } |
| |
| /** |
| * Returns the hash code value for this {@link Map}, i.e., |
| * the sum of, for each key-value pair in the map, |
| * {@code key.hashCode() ^ value.hashCode()}. |
| * |
| * @return the hash code value for this map |
| */ |
| public int hashCode() { |
| int h = 0; |
| Node<K,V>[] t; |
| if ((t = table) != null) { |
| Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length); |
| for (Node<K,V> p; (p = it.advance()) != null; ) |
| h += p.key.hashCode() ^ p.val.hashCode(); |
| } |
| return h; |
| } |
| |
| /** |
| * Returns a string representation of this map. The string |
| * representation consists of a list of key-value mappings (in no |
| * particular order) enclosed in braces ("{@code {}}"). Adjacent |
| * mappings are separated by the characters {@code ", "} (comma |
| * and space). Each key-value mapping is rendered as the key |
| * followed by an equals sign ("{@code =}") followed by the |
| * associated value. |
| * |
| * @return a string representation of this map |
| */ |
| public String toString() { |
| Node<K,V>[] t; |
| int f = (t = table) == null ? 0 : t.length; |
| Traverser<K,V> it = new Traverser<K,V>(t, f, 0, f); |
| StringBuilder sb = new StringBuilder(); |
| sb.append('{'); |
| Node<K,V> p; |
| if ((p = it.advance()) != null) { |
| for (;;) { |
| K k = p.key; |
| V v = p.val; |
| sb.append(k == this ? "(this Map)" : k); |
| sb.append('='); |
| sb.append(v == this ? "(this Map)" : v); |
| if ((p = it.advance()) == null) |
| break; |
| sb.append(',').append(' '); |
| } |
| } |
| return sb.append('}').toString(); |
| } |
| |
| /** |
| * Compares the specified object with this map for equality. |
| * Returns {@code true} if the given object is a map with the same |
| * mappings as this map. This operation may return misleading |
| * results if either map is concurrently modified during execution |
| * of this method. |
| * |
| * @param o object to be compared for equality with this map |
| * @return {@code true} if the specified object is equal to this map |
| */ |
| public boolean equals(Object o) { |
| if (o != this) { |
| if (!(o instanceof Map)) |
| return false; |
| Map<?,?> m = (Map<?,?>) o; |
| Node<K,V>[] t; |
| int f = (t = table) == null ? 0 : t.length; |
| Traverser<K,V> it = new Traverser<K,V>(t, f, 0, f); |
| for (Node<K,V> p; (p = it.advance()) != null; ) { |
| V val = p.val; |
| Object v = m.get(p.key); |
| if (v == null || (v != val && !v.equals(val))) |
| return false; |
| } |
| for (Map.Entry<?,?> e : m.entrySet()) { |
| Object mk, mv, v; |
| if ((mk = e.getKey()) == null || |
| (mv = e.getValue()) == null || |
| (v = get(mk)) == null || |
| (mv != v && !mv.equals(v))) |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /** |
| * Stripped-down version of helper class used in previous version, |
| * declared for the sake of serialization compatibility |
| */ |
| static class Segment<K,V> extends ReentrantLock implements Serializable { |
| private static final long serialVersionUID = 2249069246763182397L; |
| final float loadFactor; |
| Segment(float lf) { this.loadFactor = lf; } |
| } |
| |
| /** |
| * Saves the state of the {@code ConcurrentHashMap} instance to a |
| * stream (i.e., serializes it). |
| * @param s the stream |
| * @serialData |
| * the key (Object) and value (Object) |
| * for each key-value mapping, followed by a null pair. |
| * The key-value mappings are emitted in no particular order. |
| */ |
| private void writeObject(java.io.ObjectOutputStream s) |
| throws java.io.IOException { |
| // For serialization compatibility |
| // Emulate segment calculation from previous version of this class |
| int sshift = 0; |
| int ssize = 1; |
| while (ssize < DEFAULT_CONCURRENCY_LEVEL) { |
| ++sshift; |
| ssize <<= 1; |
| } |
| int segmentShift = 32 - sshift; |
| int segmentMask = ssize - 1; |
| @SuppressWarnings("unchecked") Segment<K,V>[] segments = (Segment<K,V>[]) |
| new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL]; |
| for (int i = 0; i < segments.length; ++i) |
| segments[i] = new Segment<K,V>(LOAD_FACTOR); |
| java.io.ObjectOutputStream.PutField streamFields = s.putFields(); |
| streamFields.put("segments", segments); |
| streamFields.put("segmentShift", segmentShift); |
| streamFields.put("segmentMask", segmentMask); |
| s.writeFields(); |
| |
| Node<K,V>[] t; |
| if ((t = table) != null) { |
| Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length); |
| for (Node<K,V> p; (p = it.advance()) != null; ) { |
| s.writeObject(p.key); |
| s.writeObject(p.val); |
| } |
| } |
| s.writeObject(null); |
| s.writeObject(null); |
| segments = null; // throw away |
| } |
| |
| /** |
| * Reconstitutes the instance from a stream (that is, deserializes it). |
| * @param s the stream |
| */ |
| private void readObject(java.io.ObjectInputStream s) |
| throws java.io.IOException, ClassNotFoundException { |
| /* |
| * To improve performance in typical cases, we create nodes |
| * while reading, then place in table once size is known. |
| * However, we must also validate uniqueness and deal with |
| * overpopulated bins while doing so, which requires |
| * specialized versions of putVal mechanics. |
| */ |
| sizeCtl = -1; // force exclusion for table construction |
| s.defaultReadObject(); |
| long size = 0L; |
| Node<K,V> p = null; |
| for (;;) { |
| @SuppressWarnings("unchecked") K k = (K) s.readObject(); |
| @SuppressWarnings("unchecked") V v = (V) s.readObject(); |
| if (k != null && v != null) { |
| p = new Node<K,V>(spread(k.hashCode()), k, v, p); |
| ++size; |
| } |
| else |
| break; |
| } |
| if (size == 0L) |
| sizeCtl = 0; |
| else { |
| int n; |
| if (size >= (long)(MAXIMUM_CAPACITY >>> 1)) |
| n = MAXIMUM_CAPACITY; |
| else { |
| int sz = (int)size; |
| n = tableSizeFor(sz + (sz >>> 1) + 1); |
| } |
| @SuppressWarnings("unchecked") |
| Node<K,V>[] tab = (Node<K,V>[])new Node<?,?>[n]; |
| int mask = n - 1; |
| long added = 0L; |
| while (p != null) { |
| boolean insertAtFront; |
| Node<K,V> next = p.next, first; |
| int h = p.hash, j = h & mask; |
| if ((first = tabAt(tab, j)) == null) |
| insertAtFront = true; |
| else { |
| K k = p.key; |
| if (first.hash < 0) { |
| TreeBin<K,V> t = (TreeBin<K,V>)first; |
| if (t.putTreeVal(h, k, p.val) == null) |
| ++added; |
| insertAtFront = false; |
| } |
| else { |
| int binCount = 0; |
| insertAtFront = true; |
| Node<K,V> q; K qk; |
| for (q = first; q != null; q = q.next) { |
| if (q.hash == h && |
| ((qk = q.key) == k || |
| (qk != null && k.equals(qk)))) { |
| insertAtFront = false; |
| break; |
| } |
| ++binCount; |
| } |
| if (insertAtFront && binCount >= TREEIFY_THRESHOLD) { |
| insertAtFront = false; |
| ++added; |
| p.next = first; |
| TreeNode<K,V> hd = null, tl = null; |
| for (q = p; q != null; q = q.next) { |
| TreeNode<K,V> t = new TreeNode<K,V> |
| (q.hash, q.key, q.val, null, null); |
| if ((t.prev = tl) == null) |
| hd = t; |
| else |
| tl.next = t; |
| tl = t; |
| } |
| setTabAt(tab, j, new TreeBin<K,V>(hd)); |
| } |
| } |
| } |
| if (insertAtFront) { |
| ++added; |
| p.next = first; |
| setTabAt(tab, j, p); |
| } |
| p = next; |
| } |
| table = tab; |
| sizeCtl = n - (n >>> 2); |
| baseCount = added; |
| } |
| } |
| |
| // ConcurrentMap methods |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @return the previous value associated with the specified key, |
| * or {@code null} if there was no mapping for the key |
| * @throws NullPointerException if the specified key or value is null |
| */ |
| public V putIfAbsent(K key, V value) { |
| return putVal(key, value, true); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @throws NullPointerException if the specified key is null |
| */ |
| public boolean remove(Object key, Object value) { |
| if (key == null) |
| throw new NullPointerException(); |
| return value != null && replaceNode(key, null, value) != null; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @throws NullPointerException if any of the arguments are null |
| */ |
| public boolean replace(K key, V oldValue, V newValue) { |
| if (key == null || oldValue == null || newValue == null) |
| throw new NullPointerException(); |
| return replaceNode(key, newValue, oldValue) != null; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @return the previous value associated with the specified key, |
| * or {@code null} if there was no mapping for the key |
| * @throws NullPointerException if the specified key or value is null |
| */ |
| public V replace(K key, V value) { |
| if (key == null || value == null) |
| throw new NullPointerException(); |
| return replaceNode(key, value, null); |
| } |
| // Hashtable legacy methods |
| |
| /** |
| * Legacy method testing if some key maps into the specified value |
| * in this table. |
| * |
| * This method is identical in functionality to |
| * {@link #containsValue(Object)}, and exists solely to ensure |
| * full compatibility with class {@link java.util.Hashtable}, |
| * which supported this method prior to introduction of the |
| * Java Collections framework. |
| * |
| * @param value a value to search for |
| * @return {@code true} if and only if some key maps to the |
| * {@code value} argument in this table as |
| * determined by the {@code equals} method; |
| * {@code false} otherwise |
| * @throws NullPointerException if the specified value is null |
| */ |
| // android-note : removed @deprecated tag from javadoc. |
| public boolean contains(Object value) { |
| // BEGIN android-note |
| // removed deprecation |
| // END android-note |
| return containsValue(value); |
| } |
| |
| /** |
| * Returns an enumeration of the keys in this table. |
| * |
| * @return an enumeration of the keys in this table |
| * @see #keySet() |
| */ |
| public Enumeration<K> keys() { |
| Node<K,V>[] t; |
| int f = (t = table) == null ? 0 : t.length; |
| return new KeyIterator<K,V>(t, f, 0, f, this); |
| } |
| |
| /** |
| * Returns an enumeration of the values in this table. |
| * |
| * @return an enumeration of the values in this table |
| * @see #values() |
| */ |
| public Enumeration<V> elements() { |
| Node<K,V>[] t; |
| int f = (t = table) == null ? 0 : t.length; |
| return new ValueIterator<K,V>(t, f, 0, f, this); |
| } |
| |
| // ConcurrentHashMap-only methods |
| |
| /** |
| * Returns the number of mappings. This method should be used |
| * instead of {@link #size} because a ConcurrentHashMap may |
| * contain more mappings than can be represented as an int. The |
| * value returned is an estimate; the actual count may differ if |
| * there are concurrent insertions or removals. |
| * |
| * @return the number of mappings |
| * @since 1.8 |
| * |
| * @hide |
| */ |
| public long mappingCount() { |
| long n = sumCount(); |
| return (n < 0L) ? 0L : n; // ignore transient negative values |
| } |
| |
| /** |
| * Creates a new {@link Set} backed by a ConcurrentHashMap |
| * from the given type to {@code Boolean.TRUE}. |
| * |
| * @param <K> the element type of the returned set |
| * @return the new set |
| * @since 1.8 |
| * |
| * @hide |
| */ |
| public static <K> KeySetView<K,Boolean> newKeySet() { |
| return new KeySetView<K,Boolean> |
| (new ConcurrentHashMap<K,Boolean>(), Boolean.TRUE); |
| } |
| |
| /** |
| * Creates a new {@link Set} backed by a ConcurrentHashMap |
| * from the given type to {@code Boolean.TRUE}. |
| * |
| * @param initialCapacity The implementation performs internal |
| * sizing to accommodate this many elements. |
| * @param <K> the element type of the returned set |
| * @return the new set |
| * @throws IllegalArgumentException if the initial capacity of |
| * elements is negative |
| * @since 1.8 |
| * |
| * @hide |
| */ |
| public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) { |
| return new KeySetView<K,Boolean> |
| (new ConcurrentHashMap<K,Boolean>(initialCapacity), Boolean.TRUE); |
| } |
| |
| /** |
| * Returns a {@link Set} view of the keys in this map, using the |
| * given common mapped value for any additions (i.e., {@link |
| * Collection#add} and {@link Collection#addAll(Collection)}). |
| * This is of course only appropriate if it is acceptable to use |
| * the same value for all additions from this view. |
| * |
| * @param mappedValue the mapped value to use for any additions |
| * @return the set view |
| * @throws NullPointerException if the mappedValue is null |
| * |
| * @hide |
| */ |
| public KeySetView<K,V> keySet(V mappedValue) { |
| if (mappedValue == null) |
| throw new NullPointerException(); |
| return new KeySetView<K,V>(this, mappedValue); |
| } |
| |
| /* ---------------- Special Nodes -------------- */ |
| |
| /** |
| * A node inserted at head of bins during transfer operations. |
| */ |
| static final class ForwardingNode<K,V> extends Node<K,V> { |
| final Node<K,V>[] nextTable; |
| ForwardingNode(Node<K,V>[] tab) { |
| super(MOVED, null, null, null); |
| this.nextTable = tab; |
| } |
| |
| Node<K,V> find(int h, Object k) { |
| Node<K,V> e; int n; |
| Node<K,V>[] tab = nextTable; |
| if (k != null && tab != null && (n = tab.length) > 0 && |
| (e = tabAt(tab, (n - 1) & h)) != null) { |
| do { |
| int eh; K ek; |
| if ((eh = e.hash) == h && |
| ((ek = e.key) == k || (ek != null && k.equals(ek)))) |
| return e; |
| if (eh < 0) |
| return e.find(h, k); |
| } while ((e = e.next) != null); |
| } |
| return null; |
| } |
| } |
| |
| /** |
| * A place-holder node used in computeIfAbsent and compute |
| */ |
| static final class ReservationNode<K,V> extends Node<K,V> { |
| ReservationNode() { |
| super(RESERVED, null, null, null); |
| } |
| |
| Node<K,V> find(int h, Object k) { |
| return null; |
| } |
| } |
| |
| /* ---------------- Table Initialization and Resizing -------------- */ |
| |
| /** |
| * Returns the stamp bits for resizing a table of size n. |
| * Must be negative when shifted left by RESIZE_STAMP_SHIFT. |
| */ |
| static final int resizeStamp(int n) { |
| return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1)); |
| } |
| |
| /** |
| * Initializes table, using the size recorded in sizeCtl. |
| */ |
| private final Node<K,V>[] initTable() { |
| Node<K,V>[] tab; int sc; |
| while ((tab = table) == null || tab.length == 0) { |
| if ((sc = sizeCtl) < 0) |
| Thread.yield(); // lost initialization race; just spin |
| else if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) { |
| try { |
| if ((tab = table) == null || tab.length == 0) { |
| int n = (sc > 0) ? sc : DEFAULT_CAPACITY; |
| @SuppressWarnings("unchecked") |
| Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n]; |
| table = tab = nt; |
| sc = n - (n >>> 2); |
| } |
| } finally { |
| sizeCtl = sc; |
| } |
| break; |
| } |
| } |
| return tab; |
| } |
| |
| /** |
| * Adds to count, and if table is too small and not already |
| * resizing, initiates transfer. If already resizing, helps |
| * perform transfer if work is available. Rechecks occupancy |
| * after a transfer to see if another resize is already needed |
| * because resizings are lagging additions. |
| * |
| * @param x the count to add |
| * @param check if <0, don't check resize, if <= 1 only check if uncontended |
| */ |
| private final void addCount(long x, int check) { |
| CounterCell[] as; long b, s; |
| if ((as = counterCells) != null || |
| !U.compareAndSwapLong(this, BASECOUNT, b = baseCount, s = b + x)) { |
| CounterHashCode hc; CounterCell a; long v; int m; |
| boolean uncontended = true; |
| if ((hc = threadCounterHashCode.get()) == null || |
| as == null || (m = as.length - 1) < 0 || |
| (a = as[m & hc.code]) == null || |
| !(uncontended = |
| U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))) { |
| fullAddCount(x, hc, uncontended); |
| return; |
| } |
| if (check <= 1) |
| return; |
| s = sumCount(); |
| } |
| if (check >= 0) { |
| Node<K,V>[] tab, nt; int n, sc; |
| while (s >= (long)(sc = sizeCtl) && (tab = table) != null && |
| (n = tab.length) < MAXIMUM_CAPACITY) { |
| int rs = resizeStamp(n); |
| if (sc < 0) { |
| if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| sc == rs + MAX_RESIZERS || (nt = nextTable) == null || |
| transferIndex <= 0) |
| break; |
| if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) |
| transfer(tab, nt); |
| } |
| else if (U.compareAndSwapInt(this, SIZECTL, sc, |
| (rs << RESIZE_STAMP_SHIFT) + 2)) |
| transfer(tab, null); |
| s = sumCount(); |
| } |
| } |
| } |
| |
| /** |
| * Helps transfer if a resize is in progress. |
| */ |
| final Node<K,V>[] helpTransfer(Node<K,V>[] tab, Node<K,V> f) { |
| Node<K,V>[] nextTab; int sc; |
| if (tab != null && (f instanceof ForwardingNode) && |
| (nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) { |
| int rs = resizeStamp(tab.length); |
| while (nextTab == nextTable && table == tab && |
| (sc = sizeCtl) < 0) { |
| if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| sc == rs + MAX_RESIZERS || transferIndex <= 0) |
| break; |
| if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) { |
| transfer(tab, nextTab); |
| break; |
| } |
| } |
| return nextTab; |
| } |
| return table; |
| } |
| |
| /** |
| * Tries to presize table to accommodate the given number of elements. |
| * |
| * @param size number of elements (doesn't need to be perfectly accurate) |
| */ |
| private final void tryPresize(int size) { |
| int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY : |
| tableSizeFor(size + (size >>> 1) + 1); |
| int sc; |
| while ((sc = sizeCtl) >= 0) { |
| Node<K,V>[] tab = table; int n; |
| if (tab == null || (n = tab.length) == 0) { |
| n = (sc > c) ? sc : c; |
| if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) { |
| try { |
| if (table == tab) { |
| @SuppressWarnings("unchecked") |
| Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n]; |
| table = nt; |
| sc = n - (n >>> 2); |
| } |
| } finally { |
| sizeCtl = sc; |
| } |
| } |
| } |
| else if (c <= sc || n >= MAXIMUM_CAPACITY) |
| break; |
| else if (tab == table) { |
| int rs = resizeStamp(n); |
| if (sc < 0) { |
| Node<K,V>[] nt; |
| if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| sc == rs + MAX_RESIZERS || (nt = nextTable) == null || |
| transferIndex <= 0) |
| break; |
| if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) |
| transfer(tab, nt); |
| } |
| else if (U.compareAndSwapInt(this, SIZECTL, sc, |
| (rs << RESIZE_STAMP_SHIFT) + 2)) |
| transfer(tab, null); |
| } |
| } |
| } |
| |
| /** |
| * Moves and/or copies the nodes in each bin to new table. See |
| * above for explanation. |
| */ |
| private final void transfer(Node<K,V>[] tab, Node<K,V>[] nextTab) { |
| int n = tab.length, stride; |
| if ((stride = (NCPU > 1) ? (n >>> 3) / NCPU : n) < MIN_TRANSFER_STRIDE) |
| stride = MIN_TRANSFER_STRIDE; // subdivide range |
| if (nextTab == null) { // initiating |
| try { |
| @SuppressWarnings("unchecked") |
| Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n << 1]; |
| nextTab = nt; |
| } catch (Throwable ex) { // try to cope with OOME |
| sizeCtl = Integer.MAX_VALUE; |
| return; |
| } |
| nextTable = nextTab; |
| transferIndex = n; |
| } |
| int nextn = nextTab.length; |
| ForwardingNode<K,V> fwd = new ForwardingNode<K,V>(nextTab); |
| boolean advance = true; |
| boolean finishing = false; // to ensure sweep before committing nextTab |
| for (int i = 0, bound = 0;;) { |
| Node<K,V> f; int fh; |
| while (advance) { |
| int nextIndex, nextBound; |
| if (--i >= bound || finishing) |
| advance = false; |
| else if ((nextIndex = transferIndex) <= 0) { |
| i = -1; |
| advance = false; |
| } |
| else if (U.compareAndSwapInt |
| (this, TRANSFERINDEX, nextIndex, |
| nextBound = (nextIndex > stride ? |
| nextIndex - stride : 0))) { |
| bound = nextBound; |
| i = nextIndex - 1; |
| advance = false; |
| } |
| } |
| if (i < 0 || i >= n || i + n >= nextn) { |
| int sc; |
| if (finishing) { |
| nextTable = null; |
| table = nextTab; |
| sizeCtl = (n << 1) - (n >>> 1); |
| return; |
| } |
| if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, sc - 1)) { |
| if ((sc - 2) != resizeStamp(n) << RESIZE_STAMP_SHIFT) |
| return; |
| finishing = advance = true; |
| i = n; // recheck before commit |
| } |
| } |
| else if ((f = tabAt(tab, i)) == null) |
| advance = casTabAt(tab, i, null, fwd); |
| else if ((fh = f.hash) == MOVED) |
| advance = true; // already processed |
| else { |
| synchronized (f) { |
| if (tabAt(tab, i) == f) { |
| Node<K,V> ln, hn; |
| if (fh >= 0) { |
| int runBit = fh & n; |
| Node<K,V> lastRun = f; |
| for (Node<K,V> p = f.next; p != null; p = p.next) { |
| int b = p.hash & n; |
| if (b != runBit) { |
| runBit = b; |
| lastRun = p; |
| } |
| } |
| if (runBit == 0) { |
| ln = lastRun; |
| hn = null; |
| } |
| else { |
| hn = lastRun; |
| ln = null; |
| } |
| for (Node<K,V> p = f; p != lastRun; p = p.next) { |
| int ph = p.hash; K pk = p.key; V pv = p.val; |
| if ((ph & n) == 0) |
| ln = new Node<K,V>(ph, pk, pv, ln); |
| else |
| hn = new Node<K,V>(ph, pk, pv, hn); |
| } |
| setTabAt(nextTab, i, ln); |
| setTabAt(nextTab, i + n, hn); |
| setTabAt(tab, i, fwd); |
| advance = true; |
| } |
| else if (f instanceof TreeBin) { |
| TreeBin<K,V> t = (TreeBin<K,V>)f; |
| TreeNode<K,V> lo = null, loTail = null; |
| TreeNode<K,V> hi = null, hiTail = null; |
| int lc = 0, hc = 0; |
| for (Node<K,V> e = t.first; e != null; e = e.next) { |
| int h = e.hash; |
| TreeNode<K,V> p = new TreeNode<K,V> |
| (h, e.key, e.val, null, null); |
| if ((h & n) == 0) { |
| if ((p.prev = loTail) == null) |
| lo = p; |
| else |
| loTail.next = p; |
| loTail = p; |
| ++lc; |
| } |
| else { |
| if ((p.prev = hiTail) == null) |
| hi = p; |
| else |
| hiTail.next = p; |
| hiTail = p; |
| ++hc; |
| } |
| } |
| ln = (lc <= UNTREEIFY_THRESHOLD) ? untreeify(lo) : |
| (hc != 0) ? new TreeBin<K,V>(lo) : t; |
| hn = (hc <= UNTREEIFY_THRESHOLD) ? untreeify(hi) : |
| (lc != 0) ? new TreeBin<K,V>(hi) : t; |
| setTabAt(nextTab, i, ln); |
| setTabAt(nextTab, i + n, hn); |
| setTabAt(tab, i, fwd); |
| advance = true; |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| /* ---------------- Conversion from/to TreeBins -------------- */ |
| |
| /** |
| * Replaces all linked nodes in bin at given index unless table is |
| * too small, in which case resizes instead. |
| */ |
| private final void treeifyBin(Node<K,V>[] tab, int index) { |
| Node<K,V> b; int n, sc; |
| if (tab != null) { |
| if ((n = tab.length) < MIN_TREEIFY_CAPACITY) |
| tryPresize(n << 1); |
| else if ((b = tabAt(tab, index)) != null && b.hash >= 0) { |
| synchronized (b) { |
| if (tabAt(tab, index) == b) { |
| TreeNode<K,V> hd = null, tl = null; |
| for (Node<K,V> e = b; e != null; e = e.next) { |
| TreeNode<K,V> p = |
| new TreeNode<K,V>(e.hash, e.key, e.val, |
| null, null); |
| if ((p.prev = tl) == null) |
| hd = p; |
| else |
| tl.next = p; |
| tl = p; |
| } |
| setTabAt(tab, index, new TreeBin<K,V>(hd)); |
| } |
| } |
| } |
| } |
| } |
| |
| /** |
| * Returns a list on non-TreeNodes replacing those in given list. |
| */ |
| static <K,V> Node<K,V> untreeify(Node<K,V> b) { |
| Node<K,V> hd = null, tl = null; |
| for (Node<K,V> q = b; q != null; q = q.next) { |
| Node<K,V> p = new Node<K,V>(q.hash, q.key, q.val, null); |
| if (tl == null) |
| hd = p; |
| else |
| tl.next = p; |
| tl = p; |
| } |
| return hd; |
| } |
| |
| /* ---------------- TreeNodes -------------- */ |
| |
| /** |
| * Nodes for use in TreeBins |
| */ |
| static final class TreeNode<K,V> extends Node<K,V> { |
| TreeNode<K,V> parent; // red-black tree links |
| TreeNode<K,V> left; |
| TreeNode<K,V> right; |
| TreeNode<K,V> prev; // needed to unlink next upon deletion |
| boolean red; |
| |
| TreeNode(int hash, K key, V val, Node<K,V> next, |
| TreeNode<K,V> parent) { |
| super(hash, key, val, next); |
| this.parent = parent; |
| } |
| |
| Node<K,V> find(int h, Object k) { |
| return findTreeNode(h, k, null); |
| } |
| |
| /** |
| * Returns the TreeNode (or null if not found) for the given key |
| * starting at given root. |
| */ |
| final TreeNode<K,V> findTreeNode(int h, Object k, Class<?> kc) { |
| if (k != null) { |
| TreeNode<K,V> p = this; |
| do { |
| int ph, dir; K pk; TreeNode<K,V> q; |
| TreeNode<K,V> pl = p.left, pr = p.right; |
| if ((ph = p.hash) > h) |
| p = pl; |
| else if (ph < h) |
| p = pr; |
| else if ((pk = p.key) == k || (pk != null && k.equals(pk))) |
| return p; |
| else if (pl == null) |
| p = pr; |
| else if (pr == null) |
| p = pl; |
| else if ((kc != null || |
| (kc = comparableClassFor(k)) != null) && |
| (dir = compareComparables(kc, k, pk)) != 0) |
| p = (dir < 0) ? pl : pr; |
| else if ((q = pr.findTreeNode(h, k, kc)) != null) |
| return q; |
| else |
| p = pl; |
| } while (p != null); |
| } |
| return null; |
| } |
| } |
| |
| |
| /* ---------------- TreeBins -------------- */ |
| |
| /** |
| * TreeNodes used at the heads of bins. TreeBins do not hold user |
| * keys or values, but instead point to list of TreeNodes and |
| * their root. They also maintain a parasitic read-write lock |
| * forcing writers (who hold bin lock) to wait for readers (who do |
| * not) to complete before tree restructuring operations. |
| */ |
| static final class TreeBin<K,V> extends Node<K,V> { |
| TreeNode<K,V> root; |
| volatile TreeNode<K,V> first; |
| volatile Thread waiter; |
| volatile int lockState; |
| // values for lockState |
| static final int WRITER = 1; // set while holding write lock |
| static final int WAITER = 2; // set when waiting for write lock |
| static final int READER = 4; // increment value for setting read lock |
| |
| /** |
| * Tie-breaking utility for ordering insertions when equal |
| * hashCodes and non-comparable. We don't require a total |
| * order, just a consistent insertion rule to maintain |
| * equivalence across rebalancings. Tie-breaking further than |
| * necessary simplifies testing a bit. |
| */ |
| static int tieBreakOrder(Object a, Object b) { |
| int d; |
| if (a == null || b == null || |
| (d = a.getClass().getName(). |
| compareTo(b.getClass().getName())) == 0) |
| d = (System.identityHashCode(a) <= System.identityHashCode(b) ? |
| -1 : 1); |
| return d; |
| } |
| |
| /** |
| * Creates bin with initial set of nodes headed by b. |
| */ |
| TreeBin(TreeNode<K,V> b) { |
| super(TREEBIN, null, null, null); |
| this.first = b; |
| TreeNode<K,V> r = null; |
| for (TreeNode<K,V> x = b, next; x != null; x = next) { |
| next = (TreeNode<K,V>)x.next; |
| x.left = x.right = null; |
| if (r == null) { |
| x.parent = null; |
| x.red = false; |
| r = x; |
| } |
| else { |
| K k = x.key; |
| int h = x.hash; |
| Class<?> kc = null; |
| for (TreeNode<K,V> p = r;;) { |
| int dir, ph; |
| K pk = p.key; |
| if ((ph = p.hash) > h) |
| dir = -1; |
| else if (ph < h) |
| dir = 1; |
| else if ((kc == null && |
| (kc = comparableClassFor(k)) == null) || |
| (dir = compareComparables(kc, k, pk)) == 0) |
| dir = tieBreakOrder(k, pk); |
| TreeNode<K,V> xp = p; |
| if ((p = (dir <= 0) ? p.left : p.right) == null) { |
| x.parent = xp; |
| if (dir <= 0) |
| xp.left = x; |
| else |
| xp.right = x; |
| r = balanceInsertion(r, x); |
| break; |
| } |
| } |
| } |
| } |
| this.root = r; |
| assert checkInvariants(root); |
| } |
| |
| /** |
| * Acquires write lock for tree restructuring. |
| */ |
| private final void lockRoot() { |
| if (!U.compareAndSwapInt(this, LOCKSTATE, 0, WRITER)) |
| contendedLock(); // offload to separate method |
| } |
| |
| /** |
| * Releases write lock for tree restructuring. |
| */ |
| private final void unlockRoot() { |
| lockState = 0; |
| } |
| |
| /** |
| * Possibly blocks awaiting root lock. |
| */ |
| private final void contendedLock() { |
| boolean waiting = false; |
| for (int s;;) { |
| if (((s = lockState) & ~WAITER) == 0) { |
| if (U.compareAndSwapInt(this, LOCKSTATE, s, WRITER)) { |
| if (waiting) |
| waiter = null; |
| return; |
| } |
| } |
| else if ((s & WAITER) == 0) { |
| if (U.compareAndSwapInt(this, LOCKSTATE, s, s | WAITER)) { |
| waiting = true; |
| waiter = Thread.currentThread(); |
| } |
| } |
| else if (waiting) |
| LockSupport.park(this); |
| } |
| } |
| |
| /** |
| * Returns matching node or null if none. Tries to search |
| * using tree comparisons from root, but continues linear |
| * search when lock not available. |
| */ |
| final Node<K,V> find(int h, Object k) { |
| if (k != null) { |
| for (Node<K,V> e = first; e != null; ) { |
| int s; K ek; |
| if (((s = lockState) & (WAITER|WRITER)) != 0) { |
| if (e.hash == h && |
| ((ek = e.key) == k || (ek != null && k.equals(ek)))) |
| return e; |
| e = e.next; |
| } |
| else if (U.compareAndSwapInt(this, LOCKSTATE, s, |
| s + READER)) { |
| TreeNode<K,V> r, p; |
| try { |
| p = ((r = root) == null ? null : |
| r.findTreeNode(h, k, null)); |
| } finally { |
| |
| Thread w; |
| int ls; |
| do {} while (!U.compareAndSwapInt |
| (this, LOCKSTATE, |
| ls = lockState, ls - READER)); |
| if (ls == (READER|WAITER) && (w = waiter) != null) |
| LockSupport.unpark(w); |
| } |
| return p; |
| } |
| } |
| } |
| return null; |
| } |
| |
| /** |
| * Finds or adds a node. |
| * @return null if added |
| */ |
| /** |
| * Finds or adds a node. |
| * @return null if added |
| */ |
| final TreeNode<K,V> putTreeVal(int h, K k, V v) { |
| Class<?> kc = null; |
| boolean searched = false; |
| for (TreeNode<K,V> p = root;;) { |
| int dir, ph; K pk; |
| if (p == null) { |
| first = root = new TreeNode<K,V>(h, k, v, null, null); |
| break; |
| } |
| else if ((ph = p.hash) > h) |
| dir = -1; |
| else if (ph < h) |
| dir = 1; |
| else if ((pk = p.key) == k || (pk != null && k.equals(pk))) |
| return p; |
| else if ((kc == null && |
| (kc = comparableClassFor(k)) == null) || |
| (dir = compareComparables(kc, k, pk)) == 0) { |
| if (!searched) { |
| TreeNode<K,V> q, ch; |
| searched = true; |
| if (((ch = p.left) != null && |
| (q = ch.findTreeNode(h, k, kc)) != null) || |
| ((ch = p.right) != null && |
| (q = ch.findTreeNode(h, k, kc)) != null)) |
| return q; |
| } |
| dir = tieBreakOrder(k, pk); |
| } |
| |
| TreeNode<K,V> xp = p; |
| if ((p = (dir <= 0) ? p.left : p.right) == null) { |
| TreeNode<K,V> x, f = first; |
| first = x = new TreeNode<K,V>(h, k, v, f, xp); |
| if (f != null) |
| f.prev = x; |
| if (dir <= 0) |
| xp.left = x; |
| else |
| xp.right = x; |
| if (!xp.red) |
| x.red = true; |
| else { |
| lockRoot(); |
| try { |
| root = balanceInsertion(root, x); |
| } finally { |
| unlockRoot(); |
| } |
| } |
| break; |
| } |
| } |
| assert checkInvariants(root); |
| return null; |
| } |
| |
| /** |
| * Removes the given node, that must be present before this |
| * call. This is messier than typical red-black deletion code |
| * because we cannot swap the contents of an interior node |
| * with a leaf successor that is pinned by "next" pointers |
| * that are accessible independently of lock. So instead we |
| * swap the tree linkages. |
| * |
| * @return true if now too small, so should be untreeified |
| */ |
| final boolean removeTreeNode(TreeNode<K,V> p) { |
| TreeNode<K,V> next = (TreeNode<K,V>)p.next; |
| TreeNode<K,V> pred = p.prev; // unlink traversal pointers |
| TreeNode<K,V> r, rl; |
| if (pred == null) |
| first = next; |
| else |
| pred.next = next; |
| if (next != null) |
| next.prev = pred; |
| if (first == null) { |
| root = null; |
| return true; |
| } |
| if ((r = root) == null || r.right == null || // too small |
| (rl = r.left) == null || rl.left == null) |
| return true; |
| lockRoot(); |
| try { |
| TreeNode<K,V> replacement; |
| TreeNode<K,V> pl = p.left; |
| TreeNode<K,V> pr = p.right; |
| if (pl != null && pr != null) { |
| TreeNode<K,V> s = pr, sl; |
| while ((sl = s.left) != null) // find successor |
| s = sl; |
| boolean c = s.red; s.red = p.red; p.red = c; // swap colors |
| TreeNode<K,V> sr = s.right; |
| TreeNode<K,V> pp = p.parent; |
| if (s == pr) { // p was s's direct parent |
| p.parent = s; |
| s.right = p; |
| } |
| else { |
| TreeNode<K,V> sp = s.parent; |
| if ((p.parent = sp) != null) { |
| if (s == sp.left) |
| sp.left = p; |
| else |
| sp.right = p; |
| } |
| if ((s.right = pr) != null) |
| pr.parent = s; |
| } |
| p.left = null; |
| if ((p.right = sr) != null) |
| sr.parent = p; |
| if ((s.left = pl) != null) |
| pl.parent = s; |
| if ((s.parent = pp) == null) |
| r = s; |
| else if (p == pp.left) |
| pp.left = s; |
| else |
| pp.right = s; |
| if (sr != null) |
| replacement = sr; |
| else |
| replacement = p; |
| } |
| else if (pl != null) |
| replacement = pl; |
| else if (pr != null) |
| replacement = pr; |
| else |
| replacement = p; |
| if (replacement != p) { |
| TreeNode<K,V> pp = replacement.parent = p.parent; |
| if (pp == null) |
| r = replacement; |
| else if (p == pp.left) |
| pp.left = replacement; |
| else |
| pp.right = replacement; |
| p.left = p.right = p.parent = null; |
| } |
| |
| root = (p.red) ? r : balanceDeletion(r, replacement); |
| |
| if (p == replacement) { // detach pointers |
| TreeNode<K,V> pp; |
| if ((pp = p.parent) != null) { |
| if (p == pp.left) |
| pp.left = null; |
| else if (p == pp.right) |
| pp.right = null; |
| p.parent = null; |
| } |
| } |
| } finally { |
| unlockRoot(); |
| } |
| assert checkInvariants(root); |
| return false; |
| } |
| |
| /* ------------------------------------------------------------ */ |
| // Red-black tree methods, all adapted from CLR |
| |
| static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root, |
| TreeNode<K,V> p) { |
| TreeNode<K,V> r, pp, rl; |
| if (p != null && (r = p.right) != null) { |
| if ((rl = p.right = r.left) != null) |
| rl.parent = p; |
| if ((pp = r.parent = p.parent) == null) |
| (root = r).red = false; |
| else if (pp.left == p) |
| pp.left = r; |
| else |
| pp.right = r; |
| r.left = p; |
| p.parent = r; |
| } |
| return root; |
| } |
| |
| static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root, |
| TreeNode<K,V> p) { |
| TreeNode<K,V> l, pp, lr; |
| if (p != null && (l = p.left) != null) { |
| if ((lr = p.left = l.right) != null) |
| lr.parent = p; |
| if ((pp = l.parent = p.parent) == null) |
| (root = l).red = false; |
| else if (pp.right == p) |
| pp.right = l; |
| else |
| pp.left = l; |
| l.right = p; |
| p.parent = l; |
| } |
| return root; |
| } |
| |
| static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root, |
| TreeNode<K,V> x) { |
| x.red = true; |
| for (TreeNode<K,V> xp, xpp, xppl, xppr;;) { |
| if ((xp = x.parent) == null) { |
| x.red = false; |
| return x; |
| } |
| else if (!xp.red || (xpp = xp.parent) == null) |
| return root; |
| if (xp == (xppl = xpp.left)) { |
| if ((xppr = xpp.right) != null && xppr.red) { |
| xppr.red = false; |
| xp.red = false; |
| xpp.red = true; |
| x = xpp; |
| } |
| else { |
| if (x == xp.right) { |
| root = rotateLeft(root, x = xp); |
| xpp = (xp = x.parent) == null ? null : xp.parent; |
| } |
| if (xp != null) { |
| xp.red = false; |
| if (xpp != null) { |
| xpp.red = true; |
| root = rotateRight(root, xpp); |
| } |
| } |
| } |
| } |
| else { |
| if (xppl != null && xppl.red) { |
| xppl.red = false; |
| xp.red = false; |
| xpp.red = true; |
| x = xpp; |
| } |
| else { |
| if (x == xp.left) { |
| root = rotateRight(root, x = xp); |
| xpp = (xp = x.parent) == null ? null : xp.parent; |
| } |
| if (xp != null) { |
| xp.red = false; |
| if (xpp != null) { |
| xpp.red = true; |
| root = rotateLeft(root, xpp); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root, |
| TreeNode<K,V> x) { |
| for (TreeNode<K,V> xp, xpl, xpr;;) { |
| if (x == null || x == root) |
| return root; |
| else if ((xp = x.parent) == null) { |
| x.red = false; |
| return x; |
| } |
| else if (x.red) { |
| x.red = false; |
| return root; |
| } |
| else if ((xpl = xp.left) == x) { |
| if ((xpr = xp.right) != null && xpr.red) { |
| xpr.red = false; |
| xp.red = true; |
| root = rotateLeft(root, xp); |
| xpr = (xp = x.parent) == null ? null : xp.right; |
| } |
| if (xpr == null) |
| x = xp; |
| else { |
| TreeNode<K,V> sl = xpr.left, sr = xpr.right; |
| if ((sr == null || !sr.red) && |
| (sl == null || !sl.red)) { |
| xpr.red = true; |
| x = xp; |
| } |
| else { |
| if (sr == null || !sr.red) { |
| if (sl != null) |
| sl.red = false; |
| xpr.red = true; |
| root = rotateRight(root, xpr); |
| xpr = (xp = x.parent) == null ? |
| null : xp.right; |
| } |
| if (xpr != null) { |
| xpr.red = (xp == null) ? false : xp.red; |
| if ((sr = xpr.right) != null) |
| sr.red = false; |
| } |
| if (xp != null) { |
| xp.red = false; |
| root = rotateLeft(root, xp); |
| } |
| x = root; |
| } |
| } |
| } |
| else { // symmetric |
| if (xpl != null && xpl.red) { |
| xpl.red = false; |
| xp.red = true; |
| root = rotateRight(root, xp); |
| xpl = (xp = x.parent) == null ? null : xp.left; |
| } |
| if (xpl == null) |
| x = xp; |
| else { |
| TreeNode<K,V> sl = xpl.left, sr = xpl.right; |
| if ((sl == null || !sl.red) && |
| (sr == null || !sr.red)) { |
| xpl.red = true; |
| x = xp; |
| } |
| else { |
| if (sl == null || !sl.red) { |
| if (sr != null) |
| sr.red = false; |
| xpl.red = true; |
| root = rotateLeft(root, xpl); |
| xpl = (xp = x.parent) == null ? |
| null : xp.left; |
| } |
| if (xpl != null) { |
| xpl.red = (xp == null) ? false : xp.red; |
| if ((sl = xpl.left) != null) |
| sl.red = false; |
| } |
| if (xp != null) { |
| xp.red = false; |
| root = rotateRight(root, xp); |
| } |
| x = root; |
| } |
| } |
| } |
| } |
| } |
| |
| /** |
| * Recursive invariant check |
| */ |
| static <K,V> boolean checkInvariants(TreeNode<K,V> t) { |
| TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right, |
| tb = t.prev, tn = (TreeNode<K,V>)t.next; |
| if (tb != null && tb.next != t) |
| return false; |
| if (tn != null && tn.prev != t) |
| return false; |
| if (tp != null && t != tp.left && t != tp.right) |
| return false; |
| if (tl != null && (tl.parent != t || tl.hash > t.hash)) |
| return false; |
| if (tr != null && (tr.parent != t || tr.hash < t.hash)) |
| return false; |
| if (t.red && tl != null && tl.red && tr != null && tr.red) |
| return false; |
| if (tl != null && !checkInvariants(tl)) |
| return false; |
| if (tr != null && !checkInvariants(tr)) |
| return false; |
| return true; |
| } |
| |
| private static final sun.misc.Unsafe U; |
| private static final long LOCKSTATE; |
| static { |
| try { |
| U = sun.misc.Unsafe.getUnsafe(); |
| Class<?> k = TreeBin.class; |
| LOCKSTATE = U.objectFieldOffset |
| (k.getDeclaredField("lockState")); |
| } catch (Exception e) { |
| throw new Error(e); |
| } |
| } |
| } |
| |
| /* ----------------Table Traversal -------------- */ |
| |
| /** |
| * Records the table, its length, and current traversal index for a |
| * traverser that must process a region of a forwarded table before |
| * proceeding with current table. |
| */ |
| static final class TableStack<K,V> { |
| int length; |
| int index; |
| Node<K,V>[] tab; |
| TableStack<K,V> next; |
| } |
| |
| /** |
| * Encapsulates traversal for methods such as containsValue; also |
| * serves as a base class for other iterators and spliterators. |
| * |
| * Method advance visits once each still-valid node that was |
| * reachable upon iterator construction. It might miss some that |
| * were added to a bin after the bin was visited, which is OK wrt |
| * consistency guarantees. Maintaining this property in the face |
| * of possible ongoing resizes requires a fair amount of |
| * bookkeeping state that is difficult to optimize away amidst |
| * volatile accesses. Even so, traversal maintains reasonable |
| * throughput. |
| * |
| * Normally, iteration proceeds bin-by-bin traversing lists. |
| * However, if the table has been resized, then all future steps |
| * must traverse both the bin at the current index as well as at |
| * (index + baseSize); and so on for further resizings. To |
| * paranoically cope with potential sharing by users of iterators |
| * across threads, iteration terminates if a bounds checks fails |
| * for a table read. |
| */ |
| static class Traverser<K,V> { |
| Node<K,V>[] tab; // current table; updated if resized |
| Node<K,V> next; // the next entry to use |
| TableStack<K,V> stack, spare; // to save/restore on ForwardingNodes |
| int index; // index of bin to use next |
| int baseIndex; // current index of initial table |
| int baseLimit; // index bound for initial table |
| final int baseSize; // initial table size |
| |
| Traverser(Node<K,V>[] tab, int size, int index, int limit) { |
| this.tab = tab; |
| this.baseSize = size; |
| this.baseIndex = this.index = index; |
| this.baseLimit = limit; |
| this.next = null; |
| } |
| |
| /** |
| * Advances if possible, returning next valid node, or null if none. |
| */ |
| final Node<K,V> advance() { |
| Node<K,V> e; |
| if ((e = next) != null) |
| e = e.next; |
| for (;;) { |
| Node<K,V>[] t; int i, n; // must use locals in checks |
| if (e != null) |
| return next = e; |
| if (baseIndex >= baseLimit || (t = tab) == null || |
| (n = t.length) <= (i = index) || i < 0) |
| return next = null; |
| if ((e = tabAt(t, i)) != null && e.hash < 0) { |
| if (e instanceof ForwardingNode) { |
| tab = ((ForwardingNode<K,V>)e).nextTable; |
| e = null; |
| pushState(t, i, n); |
| continue; |
| } |
| else if (e instanceof TreeBin) |
| e = ((TreeBin<K,V>)e).first; |
| else |
| e = null; |
| } |
| if (stack != null) |
| recoverState(n); |
| else if ((index = i + baseSize) >= n) |
| index = ++baseIndex; // visit upper slots if present |
| } |
| } |
| |
| /** |
| * Saves traversal state upon encountering a forwarding node. |
| */ |
| private void pushState(Node<K,V>[] t, int i, int n) { |
| TableStack<K,V> s = spare; // reuse if possible |
| if (s != null) |
| spare = s.next; |
| else |
| s = new TableStack<K,V>(); |
| s.tab = t; |
| s.length = n; |
| s.index = i; |
| s.next = stack; |
| stack = s; |
| } |
| |
| /** |
| * Possibly pops traversal state. |
| * |
| * @param n length of current table |
| */ |
| private void recoverState(int n) { |
| TableStack<K,V> s; int len; |
| while ((s = stack) != null && (index += (len = s.length)) >= n) { |
| n = len; |
| index = s.index; |
| tab = s.tab; |
| s.tab = null; |
| TableStack<K,V> next = s.next; |
| s.next = spare; // save for reuse |
| stack = next; |
| spare = s; |
| } |
| if (s == null && (index += baseSize) >= n) |
| index = ++baseIndex; |
| } |
| } |
| |
| /** |
| * Base of key, value, and entry Iterators. Adds fields to |
| * Traverser to support iterator.remove. |
| */ |
| static class BaseIterator<K,V> extends Traverser<K,V> { |
| final ConcurrentHashMap<K,V> map; |
| Node<K,V> lastReturned; |
| BaseIterator(Node<K,V>[] tab, int size, int index, int limit, |
| ConcurrentHashMap<K,V> map) { |
| super(tab, size, index, limit); |
| this.map = map; |
| advance(); |
| } |
| |
| public final boolean hasNext() { return next != null; } |
| public final boolean hasMoreElements() { return next != null; } |
| |
| public final void remove() { |
| Node<K,V> p; |
| if ((p = lastReturned) == null) |
| throw new IllegalStateException(); |
| lastReturned = null; |
| map.replaceNode(p.key, null, null); |
| } |
| } |
| |
| static final class KeyIterator<K,V> extends BaseIterator<K,V> |
| implements Iterator<K>, Enumeration<K> { |
| KeyIterator(Node<K,V>[] tab, int index, int size, int limit, |
| ConcurrentHashMap<K,V> map) { |
| super(tab, index, size, limit, map); |
| } |
| |
| public final K next() { |
| Node<K,V> p; |
| if ((p = next) == null) |
| throw new NoSuchElementException(); |
| K k = p.key; |
| lastReturned = p; |
| advance(); |
| return k; |
| } |
| |
| public final K nextElement() { return next(); } |
| } |
| |
| static final class ValueIterator<K,V> extends BaseIterator<K,V> |
| implements Iterator<V>, Enumeration<V> { |
| ValueIterator(Node<K,V>[] tab, int index, int size, int limit, |
| ConcurrentHashMap<K,V> map) { |
| super(tab, index, size, limit, map); |
| } |
| |
| public final V next() { |
| Node<K,V> p; |
| if ((p = next) == null) |
| throw new NoSuchElementException(); |
| V v = p.val; |
| lastReturned = p; |
| advance(); |
| return v; |
| } |
| |
| public final V nextElement() { return next(); } |
| } |
| |
| static final class EntryIterator<K,V> extends BaseIterator<K,V> |
| implements Iterator<Map.Entry<K,V>> { |
| EntryIterator(Node<K,V>[] tab, int index, int size, int limit, |
| ConcurrentHashMap<K,V> map) { |
| super(tab, index, size, limit, map); |
| } |
| |
| public final Map.Entry<K,V> next() { |
| Node<K,V> p; |
| if ((p = next) == null) |
| throw new NoSuchElementException(); |
| K k = p.key; |
| V v = p.val; |
| lastReturned = p; |
| advance(); |
| return new MapEntry<K,V>(k, v, map); |
| } |
| } |
| |
| /** |
| * Exported Entry for EntryIterator |
| */ |
| static final class MapEntry<K,V> implements Map.Entry<K,V> { |
| final K key; // non-null |
| V val; // non-null |
| final ConcurrentHashMap<K,V> map; |
| MapEntry(K key, V val, ConcurrentHashMap<K,V> map) { |
| this.key = key; |
| this.val = val; |
| this.map = map; |
| } |
| public K getKey() { return key; } |
| public V getValue() { return val; } |
| public int hashCode() { return key.hashCode() ^ val.hashCode(); } |
| public String toString() { return key + "=" + val; } |
| |
| public boolean equals(Object o) { |
| Object k, v; Map.Entry<?,?> e; |
| return ((o instanceof Map.Entry) && |
| (k = (e = (Map.Entry<?,?>)o).getKey()) != null && |
| (v = e.getValue()) != null && |
| (k == key || k.equals(key)) && |
| (v == val || v.equals(val))); |
| } |
| |
| /** |
| * Sets our entry's value and writes through to the map. The |
| * value to return is somewhat arbitrary here. Since we do not |
| * necessarily track asynchronous changes, the most recent |
| * "previous" value could be different from what we return (or |
| * could even have been removed, in which case the put will |
| * re-establish). We do not and cannot guarantee more. |
| */ |
| public V setValue(V value) { |
| if (value == null) throw new NullPointerException(); |
| V v = val; |
| val = value; |
| map.put(key, value); |
| return v; |
| } |
| } |
| |
| /* ----------------Views -------------- */ |
| |
| /** |
| * Base class for views. |
| */ |
| abstract static class CollectionView<K,V,E> |
| implements Collection<E>, java.io.Serializable { |
| private static final long serialVersionUID = 7249069246763182397L; |
| final ConcurrentHashMap<K,V> map; |
| CollectionView(ConcurrentHashMap<K,V> map) { this.map = map; } |
| |
| /** |
| * Returns the map backing this view. |
| * |
| * @return the map backing this view |
| */ |
| public ConcurrentHashMap<K,V> getMap() { return map; } |
| |
| /** |
| * Removes all of the elements from this view, by removing all |
| * the mappings from the map backing this view. |
| */ |
| public final void clear() { map.clear(); } |
| public final int size() { return map.size(); } |
| public final boolean isEmpty() { return map.isEmpty(); } |
| |
| // implementations below rely on concrete classes supplying these |
| // abstract methods |
| /** |
| * Returns a "weakly consistent" iterator that will never |
| * throw {@link ConcurrentModificationException}, and |
| * guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not |
| * guaranteed to) reflect any modifications subsequent to |
| * construction. |
| */ |
| public abstract Iterator<E> iterator(); |
| public abstract boolean contains(Object o); |
| public abstract boolean remove(Object o); |
| |
| private static final String oomeMsg = "Required array size too large"; |
| |
| public final Object[] toArray() { |
| long sz = map.mappingCount(); |
| if (sz > MAX_ARRAY_SIZE) |
| throw new OutOfMemoryError(oomeMsg); |
| int n = (int)sz; |
| Object[] r = new Object[n]; |
| int i = 0; |
| for (E e : this) { |
| if (i == n) { |
| if (n >= MAX_ARRAY_SIZE) |
| throw new OutOfMemoryError(oomeMsg); |
| if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1) |
| n = MAX_ARRAY_SIZE; |
| else |
| n += (n >>> 1) + 1; |
| r = Arrays.copyOf(r, n); |
| } |
| r[i++] = e; |
| } |
| return (i == n) ? r : Arrays.copyOf(r, i); |
| } |
| |
| @SuppressWarnings("unchecked") |
| public final <T> T[] toArray(T[] a) { |
| long sz = map.mappingCount(); |
| if (sz > MAX_ARRAY_SIZE) |
| throw new OutOfMemoryError(oomeMsg); |
| int m = (int)sz; |
| T[] r = (a.length >= m) ? a : |
| (T[])java.lang.reflect.Array |
| .newInstance(a.getClass().getComponentType(), m); |
| int n = r.length; |
| int i = 0; |
| for (E e : this) { |
| if (i == n) { |
| if (n >= MAX_ARRAY_SIZE) |
| throw new OutOfMemoryError(oomeMsg); |
| if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1) |
| n = MAX_ARRAY_SIZE; |
| else |
| n += (n >>> 1) + 1; |
| r = Arrays.copyOf(r, n); |
| } |
| r[i++] = (T)e; |
| } |
| if (a == r && i < n) { |
| r[i] = null; // null-terminate |
| return r; |
| } |
| return (i == n) ? r : Arrays.copyOf(r, i); |
| } |
| |
| /** |
| * Returns a string representation of this collection. |
| * The string representation consists of the string representations |
| * of the collection's elements in the order they are returned by |
| * its iterator, enclosed in square brackets ({@code "[]"}). |
| * Adjacent elements are separated by the characters {@code ", "} |
| * (comma and space). Elements are converted to strings as by |
| * {@link String#valueOf(Object)}. |
| * |
| * @return a string representation of this collection |
| */ |
| public final String toString() { |
| StringBuilder sb = new StringBuilder(); |
| sb.append('['); |
| Iterator<E> it = iterator(); |
| if (it.hasNext()) { |
| for (;;) { |
| Object e = it.next(); |
| sb.append(e == this ? "(this Collection)" : e); |
| if (!it.hasNext()) |
| break; |
| sb.append(',').append(' '); |
| } |
| } |
| return sb.append(']').toString(); |
| } |
| |
| public final boolean containsAll(Collection<?> c) { |
| if (c != this) { |
| for (Object e : c) { |
| if (e == null || !contains(e)) |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| public final boolean removeAll(Collection<?> c) { |
| boolean modified = false; |
| for (Iterator<E> it = iterator(); it.hasNext();) { |
| if (c.contains(it.next())) { |
| it.remove(); |
| modified = true; |
| } |
| } |
| return modified; |
| } |
| |
| public final boolean retainAll(Collection<?> c) { |
| boolean modified = false; |
| for (Iterator<E> it = iterator(); it.hasNext();) { |
| if (!c.contains(it.next())) { |
| it.remove(); |
| modified = true; |
| } |
| } |
| return modified; |
| } |
| |
| } |
| |
| /** |
| * A view of a ConcurrentHashMap as a {@link Set} of keys, in |
| * which additions may optionally be enabled by mapping to a |
| * common value. This class cannot be directly instantiated. |
| * See {@link #keySet() keySet()}, |
| * {@link #keySet(Object) keySet(V)}, |
| * |
| * @since 1.8 |
| * |
| * @hide |
| */ |
| // android-note: removed references to hidden APIs. |
| public static class KeySetView<K,V> extends CollectionView<K,V,K> |
| implements Set<K>, java.io.Serializable { |
| private static final long serialVersionUID = 7249069246763182397L; |
| private final V value; |
| KeySetView(ConcurrentHashMap<K,V> map, V value) { // non-public |
| super(map); |
| this.value = value; |
| } |
| |
| /** |
| * Returns the default mapped value for additions, |
| * or {@code null} if additions are not supported. |
| * |
| * @return the default mapped value for additions, or {@code null} |
| * if not supported |
| */ |
| public V getMappedValue() { return value; } |
| |
| /** |
| * {@inheritDoc} |
| * @throws NullPointerException if the specified key is null |
| */ |
| public boolean contains(Object o) { return map.containsKey(o); } |
| |
| /** |
| * Removes the key from this map view, by removing the key (and its |
| * corresponding value) from the backing map. This method does |
| * nothing if the key is not in the map. |
| * |
| * @param o the key to be removed from the backing map |
| * @return {@code true} if the backing map contained the specified key |
| * @throws NullPointerException if the specified key is null |
| */ |
| public boolean remove(Object o) { return map.remove(o) != null; } |
| |
| /** |
| * @return an iterator over the keys of the backing map |
| */ |
| public Iterator<K> iterator() { |
| Node<K,V>[] t; |
| ConcurrentHashMap<K,V> m = map; |
| int f = (t = m.table) == null ? 0 : t.length; |
| return new KeyIterator<K,V>(t, f, 0, f, m); |
| } |
| |
| /** |
| * Adds the specified key to this set view by mapping the key to |
| * the default mapped value in the backing map, if defined. |
| * |
| * @param e key to be added |
| * @return {@code true} if this set changed as a result of the call |
| * @throws NullPointerException if the specified key is null |
| * @throws UnsupportedOperationException if no default mapped value |
| * for additions was provided |
| */ |
| public boolean add(K e) { |
| V v; |
| if ((v = value) == null) |
| throw new UnsupportedOperationException(); |
| return map.putVal(e, v, true) == null; |
| } |
| |
| /** |
| * Adds all of the elements in the specified collection to this set, |
| * as if by calling {@link #add} on each one. |
| * |
| * @param c the elements to be inserted into this set |
| * @return {@code true} if this set changed as a result of the call |
| * @throws NullPointerException if the collection or any of its |
| * elements are {@code null} |
| * @throws UnsupportedOperationException if no default mapped value |
| * for additions was provided |
| */ |
| public boolean addAll(Collection<? extends K> c) { |
| boolean added = false; |
| V v; |
| if ((v = value) == null) |
| throw new UnsupportedOperationException(); |
| for (K e : c) { |
| if (map.putVal(e, v, true) == null) |
| added = true; |
| } |
| return added; |
| } |
| |
| public int hashCode() { |
| int h = 0; |
| for (K e : this) |
| h += e.hashCode(); |
| return h; |
| } |
| |
| public boolean equals(Object o) { |
| Set<?> c; |
| return ((o instanceof Set) && |
| ((c = (Set<?>)o) == this || |
| (containsAll(c) && c.containsAll(this)))); |
| } |
| |
| } |
| |
| /** |
| * A view of a ConcurrentHashMap as a {@link Collection} of |
| * values, in which additions are disabled. This class cannot be |
| * directly instantiated. See {@link #values()}. |
| */ |
| static final class ValuesView<K,V> extends CollectionView<K,V,V> |
| implements Collection<V>, java.io.Serializable { |
| private static final long serialVersionUID = 2249069246763182397L; |
| ValuesView(ConcurrentHashMap<K,V> map) { super(map); } |
| public final boolean contains(Object o) { |
| return map.containsValue(o); |
| } |
| |
| public final boolean remove(Object o) { |
| if (o != null) { |
| for (Iterator<V> it = iterator(); it.hasNext();) { |
| if (o.equals(it.next())) { |
| it.remove(); |
| return true; |
| } |
| } |
| } |
| return false; |
| } |
| |
| public final Iterator<V> iterator() { |
| ConcurrentHashMap<K,V> m = map; |
| Node<K,V>[] t; |
| int f = (t = m.table) == null ? 0 : t.length; |
| return new ValueIterator<K,V>(t, f, 0, f, m); |
| } |
| |
| public final boolean add(V e) { |
| throw new UnsupportedOperationException(); |
| } |
| public final boolean addAll(Collection<? extends V> c) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| } |
| |
| /** |
| * A view of a ConcurrentHashMap as a {@link Set} of (key, value) |
| * entries. This class cannot be directly instantiated. See |
| * {@link #entrySet()}. |
| */ |
| static final class EntrySetView<K,V> extends CollectionView<K,V,Map.Entry<K,V>> |
| implements Set<Map.Entry<K,V>>, java.io.Serializable { |
| private static final long serialVersionUID = 2249069246763182397L; |
| EntrySetView(ConcurrentHashMap<K,V> map) { super(map); } |
| |
| public boolean contains(Object o) { |
| Object k, v, r; Map.Entry<?,?> e; |
| return ((o instanceof Map.Entry) && |
| (k = (e = (Map.Entry<?,?>)o).getKey()) != null && |
| (r = map.get(k)) != null && |
| (v = e.getValue()) != null && |
| (v == r || v.equals(r))); |
| } |
| |
| public boolean remove(Object o) { |
| Object k, v; Map.Entry<?,?> e; |
| return ((o instanceof Map.Entry) && |
| (k = (e = (Map.Entry<?,?>)o).getKey()) != null && |
| (v = e.getValue()) != null && |
| map.remove(k, v)); |
| } |
| |
| /** |
| * @return an iterator over the entries of the backing map |
| */ |
| public Iterator<Map.Entry<K,V>> iterator() { |
| ConcurrentHashMap<K,V> m = map; |
| Node<K,V>[] t; |
| int f = (t = m.table) == null ? 0 : t.length; |
| return new EntryIterator<K,V>(t, f, 0, f, m); |
| } |
| |
| public boolean add(Entry<K,V> e) { |
| return map.putVal(e.getKey(), e.getValue(), false) == null; |
| } |
| |
| public boolean addAll(Collection<? extends Entry<K,V>> c) { |
| boolean added = false; |
| for (Entry<K,V> e : c) { |
| if (add(e)) |
| added = true; |
| } |
| return added; |
| } |
| |
| public final int hashCode() { |
| int h = 0; |
| Node<K,V>[] t; |
| if ((t = map.table) != null) { |
| Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length); |
| for (Node<K,V> p; (p = it.advance()) != null; ) { |
| h += p.hashCode(); |
| } |
| } |
| return h; |
| } |
| |
| public final boolean equals(Object o) { |
| Set<?> c; |
| return ((o instanceof Set) && |
| ((c = (Set<?>)o) == this || |
| (containsAll(c) && c.containsAll(this)))); |
| } |
| |
| } |
| |
| |
| /* ---------------- Counters -------------- */ |
| |
| // Adapted from LongAdder and Striped64. |
| // See their internal docs for explanation. |
| |
| // A padded cell for distributing counts |
| static final class CounterCell { |
| volatile long p0, p1, p2, p3, p4, p5, p6; |
| volatile long value; |
| volatile long q0, q1, q2, q3, q4, q5, q6; |
| CounterCell(long x) { value = x; } |
| } |
| |
| /** |
| * Holder for the thread-local hash code determining which |
| * CounterCell to use. The code is initialized via the |
| * counterHashCodeGenerator, but may be moved upon collisions. |
| */ |
| static final class CounterHashCode { |
| int code; |
| } |
| |
| /** |
| * Generates initial value for per-thread CounterHashCodes. |
| */ |
| static final AtomicInteger counterHashCodeGenerator = new AtomicInteger(); |
| |
| /** |
| * Increment for counterHashCodeGenerator. See class ThreadLocal |
| * for explanation. |
| */ |
| static final int SEED_INCREMENT = 0x61c88647; |
| |
| /** |
| * Per-thread counter hash codes. Shared across all instances. |
| */ |
| static final ThreadLocal<CounterHashCode> threadCounterHashCode = |
| new ThreadLocal<CounterHashCode>(); |
| |
| final long sumCount() { |
| CounterCell[] as = counterCells; CounterCell a; |
| long sum = baseCount; |
| if (as != null) { |
| for (int i = 0; i < as.length; ++i) { |
| if ((a = as[i]) != null) |
| sum += a.value; |
| } |
| } |
| return sum; |
| } |
| |
| // See LongAdder version for explanation |
| private final void fullAddCount(long x, CounterHashCode hc, |
| boolean wasUncontended) { |
| int h; |
| if (hc == null) { |
| hc = new CounterHashCode(); |
| int s = counterHashCodeGenerator.addAndGet(SEED_INCREMENT); |
| h = hc.code = (s == 0) ? 1 : s; // Avoid zero |
| threadCounterHashCode.set(hc); |
| } |
| else |
| h = hc.code; |
| boolean collide = false; // True if last slot nonempty |
| for (;;) { |
| CounterCell[] as; CounterCell a; int n; long v; |
| if ((as = counterCells) != null && (n = as.length) > 0) { |
| if ((a = as[(n - 1) & h]) == null) { |
| if (cellsBusy == 0) { // Try to attach new Cell |
| CounterCell r = new CounterCell(x); // Optimistic create |
| if (cellsBusy == 0 && |
| U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) { |
| boolean created = false; |
| try { // Recheck under lock |
| CounterCell[] rs; int m, j; |
| if ((rs = counterCells) != null && |
| (m = rs.length) > 0 && |
| rs[j = (m - 1) & h] == null) { |
| rs[j] = r; |
| created = true; |
| } |
| } finally { |
| cellsBusy = 0; |
| } |
| if (created) |
| break; |
| continue; // Slot is now non-empty |
| } |
| } |
| collide = false; |
| } |
| else if (!wasUncontended) // CAS already known to fail |
| wasUncontended = true; // Continue after rehash |
| else if (U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x)) |
| break; |
| else if (counterCells != as || n >= NCPU) |
| collide = false; // At max size or stale |
| else if (!collide) |
| collide = true; |
| else if (cellsBusy == 0 && |
| U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) { |
| try { |
| if (counterCells == as) {// Expand table unless stale |
| CounterCell[] rs = new CounterCell[n << 1]; |
| for (int i = 0; i < n; ++i) |
| rs[i] = as[i]; |
| counterCells = rs; |
| } |
| } finally { |
| cellsBusy = 0; |
| } |
| collide = false; |
| continue; // Retry with expanded table |
| } |
| h ^= h << 13; // Rehash |
| h ^= h >>> 17; |
| h ^= h << 5; |
| } |
| else if (cellsBusy == 0 && counterCells == as && |
| U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) { |
| boolean init = false; |
| try { // Initialize table |
| if (counterCells == as) { |
| CounterCell[] rs = new CounterCell[2]; |
| rs[h & 1] = new CounterCell(x); |
| counterCells = rs; |
| init = true; |
| } |
| } finally { |
| cellsBusy = 0; |
| } |
| if (init) |
| break; |
| } |
| else if (U.compareAndSwapLong(this, BASECOUNT, v = baseCount, v + x)) |
| break; // Fall back on using base |
| } |
| hc.code = h; // Record index for next time |
| } |
| |
| // Unsafe mechanics |
| private static final sun.misc.Unsafe U; |
| private static final long SIZECTL; |
| private static final long TRANSFERINDEX; |
| private static final long BASECOUNT; |
| private static final long CELLSBUSY; |
| private static final long CELLVALUE; |
| private static final long ABASE; |
| private static final int ASHIFT; |
| |
| static { |
| try { |
| U = sun.misc.Unsafe.getUnsafe(); |
| Class<?> k = ConcurrentHashMap.class; |
| SIZECTL = U.objectFieldOffset |
| (k.getDeclaredField("sizeCtl")); |
| TRANSFERINDEX = U.objectFieldOffset |
| (k.getDeclaredField("transferIndex")); |
| BASECOUNT = U.objectFieldOffset |
| (k.getDeclaredField("baseCount")); |
| CELLSBUSY = U.objectFieldOffset |
| (k.getDeclaredField("cellsBusy")); |
| Class<?> ck = CounterCell.class; |
| CELLVALUE = U.objectFieldOffset |
| (ck.getDeclaredField("value")); |
| Class<?> ak = Node[].class; |
| ABASE = U.arrayBaseOffset(ak); |
| int scale = U.arrayIndexScale(ak); |
| if ((scale & (scale - 1)) != 0) |
| throw new Error("data type scale not a power of two"); |
| ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); |
| } catch (Exception e) { |
| throw new Error(e); |
| } |
| |
| // Reduce the risk of rare disastrous classloading in first call to |
| // LockSupport.park: https://bugs.openjdk.java.net/browse/JDK-8074773 |
| Class<?> ensureLoaded = LockSupport.class; |
| } |
| |
| } |