package com.gemstone.gemfire.internal.concurrent; | |
/* | |
* CompactConcurrentHashSet2 is derived from the JSR 166 ConcurrentHashMap | |
* class version 1.43 (current as of 27 March 2015). The modifications | |
* made for GemFire turn it into a Set instead of a Map by removing the | |
* map's storage for values and removing the methods that are associated | |
* with values. | |
* | |
* JSR 166 interest web site: | |
* http://gee.cs.oswego.edu/dl/concurrency-interest/ | |
* | |
* File download location: | |
* http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jdk7/java/util/concurrent/CompactConcurrentHashSet2.java?revision=1.43 | |
* | |
* Original licensing notice: | |
* 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/ | |
*/ | |
import java.io.ObjectStreamField; | |
import java.io.Serializable; | |
import java.lang.reflect.Field; | |
import java.lang.reflect.ParameterizedType; | |
import java.lang.reflect.Type; | |
import java.util.AbstractSet; | |
import java.util.Collection; | |
import java.util.Enumeration; | |
import java.util.Iterator; | |
import java.util.NoSuchElementException; | |
import java.util.Set; | |
import java.util.concurrent.atomic.AtomicInteger; | |
import java.util.concurrent.locks.LockSupport; | |
import java.util.concurrent.locks.ReentrantLock; | |
/** | |
* <p>This is the original javadoc describing ConcurrentHashMap. This | |
* class is actually a Set based on Doug Lea's CHM implementation | |
* (see the source file for full attribution). | |
* </p> | |
* A hash map supporting full concurrency of retrievals and | |
* high expected concurrency for updates. This class obeys the | |
* same functional specification as {@link java.util.HashMap}, and | |
* includes versions of methods corresponding to each method of | |
* {@code HashMap}. 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 set | |
* in a way that prevents all access. This class is fully | |
* interoperable with {@code HashMap} in programs that rely on its | |
* thread safety but not on its synchronization details. | |
* | |
* | |
* @since 9.0 | |
* @author Originally Doug Lea | |
* @param <V> the type of values held in the set | |
*/ | |
public class CompactConcurrentHashSet2<V> extends AbstractSet<V> implements Set<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> { | |
final int hash; | |
final K key; | |
Node<K> next; | |
Node(int hash, K key, Node<K> next) { | |
this.hash = hash; | |
this.key = key; | |
this.next = next; | |
} | |
public final K getKey() { return key; } | |
public final int hashCode() { return key.hashCode(); } | |
public final String toString(){ return key.toString(); } | |
public final boolean equals(Object o) { | |
Object k, u; Node<?> e; | |
return ((o instanceof Node) && | |
((k = (e = (Node<?>)o)) != null) && | |
(k == key || k.equals(key))); | |
} | |
/** | |
* Virtualized support for map.get(); overridden in subclasses. | |
*/ | |
Node<K> find(int h, Object k) { | |
Node<K> 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> Node<K> tabAt(Node<K>[] tab, int i) { | |
return (Node<K>)U.getObjectVolatile(tab, ((long)i << ASHIFT) + ABASE); | |
} | |
static final <K> boolean casTabAt(Node<K>[] tab, int i, | |
Node<K> c, Node<K> v) { | |
return U.compareAndSwapObject(tab, ((long)i << ASHIFT) + ABASE, c, v); | |
} | |
static final <K> void setTabAt(Node<K>[] tab, int i, Node<K> 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<V>[] table; | |
/** | |
* The next table to use; non-null only while resizing. | |
*/ | |
private transient volatile Node<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; | |
/* ---------------- Public operations -------------- */ | |
/** | |
* Creates a new, empty map with the default initial table size (16). | |
*/ | |
public CompactConcurrentHashSet2() { | |
} | |
/** | |
* 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 CompactConcurrentHashSet2(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 CompactConcurrentHashSet2(Collection<? extends V> m) { | |
this.sizeCtl = DEFAULT_CAPACITY; | |
addAll(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 9.0 | |
*/ | |
public CompactConcurrentHashSet2(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 CompactConcurrentHashSet2(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 | |
} | |
boolean _contains(Object key) { | |
Node<V>[] tab; Node<V> e, p; int n, eh; V ek; | |
if (key == null) { | |
return false; | |
} | |
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 true; | |
} | |
else if (eh < 0) | |
return ((p = e.find(h, key)) != null); | |
while ((e = e.next) != null) { | |
if (e.hash == h && | |
((ek = e.key) == key || (ek != null && key.equals(ek)))) | |
return true; | |
} | |
} | |
return false; | |
} | |
@Override | |
public boolean add(V value) { | |
return putKey(value, false); | |
} | |
/** Implementation for add */ | |
final boolean putKey(V key, boolean onlyIfAbsent) { | |
if (key == null) throw new NullPointerException(); | |
int hash = spread(key.hashCode()); | |
int binCount = 0; | |
for (Node<V>[] tab = table;;) { | |
Node<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<V>(hash, key, null))) | |
break; // no lock when adding to empty bin | |
} | |
else if ((fh = f.hash) == MOVED) | |
tab = helpTransfer(tab, f); | |
else { | |
boolean wasPresent = false; | |
synchronized (f) { | |
if (tabAt(tab, i) == f) { | |
if (fh >= 0) { | |
binCount = 1; | |
for (Node<V> e = f;; ++binCount) { | |
V ek; | |
if (e.hash == hash && | |
((ek = e.key) == key || | |
(ek != null && key.equals(ek)))) { | |
wasPresent = true; | |
break; | |
} | |
Node<V> pred = e; | |
if ((e = e.next) == null) { | |
pred.next = new Node<V>(hash, key, | |
null); | |
break; | |
} | |
} | |
} | |
else if (f instanceof TreeBin) { | |
Node<V> p; | |
binCount = 2; | |
if ((p = ((TreeBin<V>)f).putTreeVal(hash, key | |
)) != null) { | |
wasPresent = true; | |
} | |
} | |
} | |
} | |
if (binCount != 0) { | |
if (binCount >= TREEIFY_THRESHOLD) | |
treeifyBin(tab, i); | |
if (wasPresent) | |
return true; | |
break; | |
} | |
} | |
} | |
addCount(1L, binCount); | |
return false; | |
} | |
/** | |
* 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 addAll(Set<? extends V> m) { | |
tryPresize(m.size()); | |
Iterator<? extends V> it = m.iterator(); | |
while (it.hasNext()) { | |
putKey(it.next(), false); | |
} | |
} | |
@Override | |
public boolean remove(Object key) { | |
return removeNode(key); | |
} | |
final boolean removeNode(Object key) { | |
int hash = spread(key.hashCode()); | |
for (Node<V>[] tab = table;;) { | |
Node<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 { | |
boolean wasPresent = false; | |
boolean validated = false; | |
synchronized (f) { | |
if (tabAt(tab, i) == f) { | |
if (fh >= 0) { | |
validated = true; | |
for (Node<V> e = f, pred = null;;) { | |
V ek; | |
if (e.hash == hash && | |
((ek = e.key) == key || | |
(ek != null && key.equals(ek)))) { | |
wasPresent = true; | |
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<V> t = (TreeBin<V>)f; | |
TreeNode<V> r, p; | |
if ((r = t.root) != null && | |
(p = r.findTreeNode(hash, key, null)) != null) { | |
wasPresent = true; | |
if (t.removeTreeNode(p)) | |
setTabAt(tab, i, untreeify(t.first)); | |
} | |
} | |
} | |
} | |
if (validated) { | |
if (wasPresent) { | |
addCount(-1L, -1); | |
return true; | |
} | |
break; | |
} | |
} | |
} | |
return false; | |
} | |
/** | |
* Removes all of the mappings from this map. | |
*/ | |
public void clear() { | |
long delta = 0L; // negative number of deletions | |
int i = 0; | |
Node<V>[] tab = table; | |
while (tab != null && i < tab.length) { | |
int fh; | |
Node<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<V> p = (fh >= 0 ? f : | |
(f instanceof TreeBin) ? | |
((TreeBin<V>)f).first : null); | |
while (p != null) { | |
--delta; | |
p = p.next; | |
} | |
setTabAt(tab, i++, null); | |
} | |
} | |
} | |
} | |
if (delta != 0L) | |
addCount(delta, -1); | |
} | |
// public int hashCode() { | |
// int h = 0; | |
// Node<V>[] t; | |
// if ((t = table) != null) { | |
// Traverser<V> it = new Traverser<V>(t, t.length, 0, t.length); | |
// for (Node<V> p; (p = it.advance()) != null; ) | |
// h += p.key.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<V>[] t; | |
int f = (t = table) == null ? 0 : t.length; | |
Traverser<V> it = new Traverser<V>(t, f, 0, f); | |
StringBuilder sb = new StringBuilder(); | |
sb.append('{'); | |
Node<V> p; | |
if ((p = it.advance()) != null) { | |
for (;;) { | |
V k = p.key; | |
sb.append(k == this ? "(this Set)" : k); | |
if ((p = it.advance()) == null) | |
break; | |
sb.append(',').append(' '); | |
} | |
} | |
return sb.append('}').toString(); | |
} | |
// public boolean equals(Object o) { | |
// if (o != this) { | |
// if (!(o instanceof Set)) | |
// return false; | |
// Set<?> m = (Set<?>) o; | |
// Node<V>[] t; | |
// int f = (t = table) == null ? 0 : t.length; | |
// Traverser<V> it = new Traverser<V>(t, f, 0, f); | |
// for (Node<V> p; (p = it.advance()) != null; ) { | |
// if (!m.contains(p.key)) { | |
// return false; | |
// } | |
// } | |
// Iterator<?> itr = m.iterator(); | |
// while (itr.hasNext()) { | |
// if (!contains(itr.next())) { | |
// 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> 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 CompactConcurrentHashSet2} 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<V>[] segments = (Segment<V>[]) | |
new Segment<?>[DEFAULT_CONCURRENCY_LEVEL]; | |
for (int i = 0; i < segments.length; ++i) | |
segments[i] = new Segment<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<V>[] t; | |
if ((t = table) != null) { | |
Traverser<V> it = new Traverser<V>(t, t.length, 0, t.length); | |
for (Node<V> p; (p = it.advance()) != null; ) { | |
s.writeObject(p.key); | |
} | |
} | |
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<V> p = null; | |
for (;;) { | |
@SuppressWarnings("unchecked") V k = (V) s.readObject(); | |
if (k != null) { | |
p = new Node<V>(spread(k.hashCode()), k, 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<V>[] tab = (Node<V>[])new Node<?>[n]; | |
int mask = n - 1; | |
long added = 0L; | |
while (p != null) { | |
boolean insertAtFront; | |
Node<V> next = p.next, first; | |
int h = p.hash, j = h & mask; | |
if ((first = tabAt(tab, j)) == null) | |
insertAtFront = true; | |
else { | |
V k = p.key; | |
if (first.hash < 0) { | |
TreeBin<V> t = (TreeBin<V>)first; | |
if (t.putTreeVal(h, k) == null) | |
++added; | |
insertAtFront = false; | |
} | |
else { | |
int binCount = 0; | |
insertAtFront = true; | |
Node<V> q; V 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<V> hd = null, tl = null; | |
for (q = p; q != null; q = q.next) { | |
TreeNode<V> t = new TreeNode<V> | |
(q.hash, q.key, null, null); | |
if ((t.prev = tl) == null) | |
hd = t; | |
else | |
tl.next = t; | |
tl = t; | |
} | |
setTabAt(tab, j, new TreeBin<V>(hd)); | |
} | |
} | |
} | |
if (insertAtFront) { | |
++added; | |
p.next = first; | |
setTabAt(tab, j, p); | |
} | |
p = next; | |
} | |
table = tab; | |
sizeCtl = n - (n >>> 2); | |
baseCount = added; | |
} | |
} | |
@Override | |
public boolean contains(Object value) { | |
return _contains(value); | |
} | |
@Override | |
public Iterator<V> iterator() { | |
Node<V>[] t; | |
CompactConcurrentHashSet2<V> m = this; | |
int f = (t = m.table) == null ? 0 : t.length; | |
return new KeyIterator<V>(t, f, 0, f, m); | |
} | |
// CompactConcurrentHashSet2-only methods | |
/** | |
* Returns the number of mappings. This method should be used | |
* instead of {@link #size} because a CompactConcurrentHashSet2 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 9.0 | |
*/ | |
public long mappingCount() { | |
long n = sumCount(); | |
return (n < 0L) ? 0L : n; // ignore transient negative values | |
} | |
/* ---------------- Special Nodes -------------- */ | |
/** | |
* A node inserted at head of bins during transfer operations. | |
*/ | |
static final class ForwardingNode<K> extends Node<K> { | |
final Node<K>[] nextTable; | |
ForwardingNode(Node<K>[] tab) { | |
super(MOVED, null, null); | |
this.nextTable = tab; | |
} | |
Node<K> find(int h, Object k) { | |
Node<K> e; int n; | |
Node<K>[] 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> extends Node<K> { | |
ReservationNode() { | |
super(RESERVED, null, null); | |
} | |
Node<K> 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<V>[] initTable() { | |
Node<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<V>[] nt = (Node<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<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<V>[] helpTransfer(Node<V>[] tab, Node<V> f) { | |
Node<V>[] nextTab; int sc; | |
if (tab != null && (f instanceof ForwardingNode) && | |
(nextTab = ((ForwardingNode<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<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<V>[] nt = (Node<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<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<V>[] tab, Node<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<V>[] nt = (Node<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<V> fwd = new ForwardingNode<V>(nextTab); | |
boolean advance = true; | |
boolean finishing = false; // to ensure sweep before committing nextTab | |
for (int i = 0, bound = 0;;) { | |
Node<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<V> ln, hn; | |
if (fh >= 0) { | |
int runBit = fh & n; | |
Node<V> lastRun = f; | |
for (Node<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<V> p = f; p != lastRun; p = p.next) { | |
int ph = p.hash; V pk = p.key; | |
if ((ph & n) == 0) | |
ln = new Node<V>(ph, pk, ln); | |
else | |
hn = new Node<V>(ph, pk, hn); | |
} | |
setTabAt(nextTab, i, ln); | |
setTabAt(nextTab, i + n, hn); | |
setTabAt(tab, i, fwd); | |
advance = true; | |
} | |
else if (f instanceof TreeBin) { | |
TreeBin<V> t = (TreeBin<V>)f; | |
TreeNode<V> lo = null, loTail = null; | |
TreeNode<V> hi = null, hiTail = null; | |
int lc = 0, hc = 0; | |
for (Node<V> e = t.first; e != null; e = e.next) { | |
int h = e.hash; | |
TreeNode<V> p = new TreeNode<V> | |
(h, e.key, 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<V>(lo) : t; | |
hn = (hc <= UNTREEIFY_THRESHOLD) ? untreeify(hi) : | |
(lc != 0) ? new TreeBin<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<V>[] tab, int index) { | |
Node<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<V> hd = null, tl = null; | |
for (Node<V> e = b; e != null; e = e.next) { | |
TreeNode<V> p = | |
new TreeNode<V>(e.hash, e.key, | |
null, null); | |
if ((p.prev = tl) == null) | |
hd = p; | |
else | |
tl.next = p; | |
tl = p; | |
} | |
setTabAt(tab, index, new TreeBin<V>(hd)); | |
} | |
} | |
} | |
} | |
} | |
/** | |
* Returns a list on non-TreeNodes replacing those in given list. | |
*/ | |
static <K> Node<K> untreeify(Node<K> b) { | |
Node<K> hd = null, tl = null; | |
for (Node<K> q = b; q != null; q = q.next) { | |
Node<K> p = new Node<K>(q.hash, q.key, 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> extends Node<K> { | |
TreeNode<K> parent; // red-black tree links | |
TreeNode<K> left; | |
TreeNode<K> right; | |
TreeNode<K> prev; // needed to unlink next upon deletion | |
boolean red; | |
TreeNode(int hash, K key, Node<K> next, | |
TreeNode<K> parent) { | |
super(hash, key, next); | |
this.parent = parent; | |
} | |
Node<K> 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> findTreeNode(int h, Object k, Class<?> kc) { | |
if (k != null) { | |
TreeNode<K> p = this; | |
do { | |
int ph, dir; K pk; TreeNode<K> q; | |
TreeNode<K> 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> extends Node<K> { | |
TreeNode<K> root; | |
volatile TreeNode<K> 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> b) { | |
super(TREEBIN, null, null); | |
this.first = b; | |
TreeNode<K> r = null; | |
for (TreeNode<K> x = b, next; x != null; x = next) { | |
next = (TreeNode<K>)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> 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> 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> find(int h, Object k) { | |
if (k != null) { | |
for (Node<K> 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> 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> putTreeVal(int h, K k) { | |
Class<?> kc = null; | |
boolean searched = false; | |
for (TreeNode<K> p = root;;) { | |
int dir, ph; K pk; | |
if (p == null) { | |
first = root = new TreeNode<K>(h, k, 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> 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> xp = p; | |
if ((p = (dir <= 0) ? p.left : p.right) == null) { | |
TreeNode<K> x, f = first; | |
first = x = new TreeNode<K>(h, k, 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> p) { | |
TreeNode<K> next = (TreeNode<K>)p.next; | |
TreeNode<K> pred = p.prev; // unlink traversal pointers | |
TreeNode<K> 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> replacement; | |
TreeNode<K> pl = p.left; | |
TreeNode<K> pr = p.right; | |
if (pl != null && pr != null) { | |
TreeNode<K> 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> sr = s.right; | |
TreeNode<K> pp = p.parent; | |
if (s == pr) { // p was s's direct parent | |
p.parent = s; | |
s.right = p; | |
} | |
else { | |
TreeNode<K> 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> 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> 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> TreeNode<K> rotateLeft(TreeNode<K> root, | |
TreeNode<K> p) { | |
TreeNode<K> 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> TreeNode<K> rotateRight(TreeNode<K> root, | |
TreeNode<K> p) { | |
TreeNode<K> 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> TreeNode<K> balanceInsertion(TreeNode<K> root, | |
TreeNode<K> x) { | |
x.red = true; | |
for (TreeNode<K> 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> TreeNode<K> balanceDeletion(TreeNode<K> root, | |
TreeNode<K> x) { | |
for (TreeNode<K> 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> 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> 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> boolean checkInvariants(TreeNode<K> t) { | |
TreeNode<K> tp = t.parent, tl = t.left, tr = t.right, | |
tb = t.prev, tn = (TreeNode<K>)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 { | |
Field f = sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); | |
f.setAccessible(true); | |
U = (sun.misc.Unsafe) f.get(null); | |
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> { | |
int length; | |
int index; | |
Node<K>[] tab; | |
TableStack<K> 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> { | |
Node<K>[] tab; // current table; updated if resized | |
Node<K> next; // the next entry to use | |
TableStack<K> 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>[] 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> advance() { | |
Node<K> e; | |
if ((e = next) != null) | |
e = e.next; | |
for (;;) { | |
Node<K>[] 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>)e).nextTable; | |
e = null; | |
pushState(t, i, n); | |
continue; | |
} | |
else if (e instanceof TreeBin) | |
e = ((TreeBin<K>)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>[] t, int i, int n) { | |
TableStack<K> s = spare; // reuse if possible | |
if (s != null) | |
spare = s.next; | |
else | |
s = new TableStack<K>(); | |
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> 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> 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> extends Traverser<K> { | |
final CompactConcurrentHashSet2<K> set; | |
Node<K> lastReturned; | |
BaseIterator(Node<K>[] tab, int size, int index, int limit, | |
CompactConcurrentHashSet2<K> map) { | |
super(tab, size, index, limit); | |
this.set = map; | |
advance(); | |
} | |
public final boolean hasNext() { return next != null; } | |
public final boolean hasMoreElements() { return next != null; } | |
public final void remove() { | |
Node<K> p; | |
if ((p = lastReturned) == null) | |
throw new IllegalStateException(); | |
lastReturned = null; | |
set.removeNode(p.key); | |
} | |
} | |
static final class KeyIterator<K> extends BaseIterator<K> | |
implements Iterator<K>, Enumeration<K> { | |
KeyIterator(Node<K>[] tab, int index, int size, int limit, | |
CompactConcurrentHashSet2<K> map) { | |
super(tab, index, size, limit, map); | |
} | |
public final K next() { | |
Node<K> p; | |
if ((p = next) == null) | |
throw new NoSuchElementException(); | |
K k = p.key; | |
lastReturned = p; | |
advance(); | |
return k; | |
} | |
public final K nextElement() { return next(); } | |
} | |
/* ---------------- 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 { | |
Field f = sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); | |
f.setAccessible(true); | |
U = (sun.misc.Unsafe) f.get(null); | |
Class<?> k = CompactConcurrentHashSet2.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; | |
} | |
} |