/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
*/
/**
* A scalable concurrent {@link ConcurrentNavigableMap} implementation.
* The map is sorted according to the {@linkplain Comparable natural
* ordering} of its keys, or by a {@link Comparator} provided at map
* creation time, depending on which constructor is used.
*
* <p>This class implements a concurrent variant of <a
* href="http://en.wikipedia.org/wiki/Skip_list" target="_top">SkipLists</a>
* providing expected average <i>log(n)</i> time cost for the
* <tt>containsKey</tt>, <tt>get</tt>, <tt>put</tt> and
* <tt>remove</tt> operations and their variants. Insertion, removal,
* update, and access operations safely execute concurrently by
* multiple threads. Iterators are <i>weakly consistent</i>, returning
* elements reflecting the state of the map at some point at or since
* the creation of the iterator. They do <em>not</em> throw {@link
* ConcurrentModificationException}, and may proceed concurrently with
* other operations. Ascending key ordered views and their iterators
* are faster than descending ones.
*
* <p>All <tt>Map.Entry</tt> pairs returned by methods in this class
* and its views represent snapshots of mappings at the time they were
* produced. They do <em>not</em> support the <tt>Entry.setValue</tt>
* method. (Note however that it is possible to change mappings in the
* associated map using <tt>put</tt>, <tt>putIfAbsent</tt>, or
* <tt>replace</tt>, depending on exactly which effect you need.)
*
* <p>Beware that, unlike in most collections, the <tt>size</tt>
* method is <em>not</em> a constant-time operation. Because of the
* asynchronous nature of these maps, determining the current number
* of elements requires a traversal of the elements, and so may report
* inaccurate results if this collection is modified during traversal.
* Additionally, the bulk operations <tt>putAll</tt>, <tt>equals</tt>,
* <tt>toArray</tt>, <tt>containsValue</tt>, and <tt>clear</tt> are
* <em>not</em> guaranteed to be performed atomically. For example, an
* iterator operating concurrently with a <tt>putAll</tt> operation
* might view only some of the added elements.
*
* <p>This class and its views and iterators implement all of the
* <em>optional</em> methods of the {@link Map} and {@link Iterator}
* interfaces. Like most other concurrent collections, this class does
* <em>not</em> permit the use of <tt>null</tt> keys or values because some
* null return values cannot be reliably distinguished from the absence of
* elements.
*
* <p>This class is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @author Doug Lea
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
* @since 1.6
*/
implements ConcurrentNavigableMap<K,V>,
/*
* This class implements a tree-like two-dimensionally linked skip
* list in which the index levels are represented in separate
* nodes from the base nodes holding data. There are two reasons
* for taking this approach instead of the usual array-based
* structure: 1) Array based implementations seem to encounter
* more complexity and overhead 2) We can use cheaper algorithms
* for the heavily-traversed index lists than can be used for the
* base lists. Here's a picture of some of the basics for a
* possible list with 2 levels of index:
*
* Head nodes Index nodes
* +-+ right +-+ +-+
* |2|---------------->| |--------------------->| |->null
* +-+ +-+ +-+
* | down | |
* v v v
* +-+ +-+ +-+ +-+ +-+ +-+
* |1|----------->| |->| |------>| |----------->| |------>| |->null
* +-+ +-+ +-+ +-+ +-+ +-+
* v | | | | |
* Nodes next v v v v v
* +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
* | |->|A|->|B|->|C|->|D|->|E|->|F|->|G|->|H|->|I|->|J|->|K|->null
* +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
*
* The base lists use a variant of the HM linked ordered set
* algorithm. See Tim Harris, "A pragmatic implementation of
* non-blocking linked lists"
* http://www.cl.cam.ac.uk/~tlh20/publications.html and Maged
* Michael "High Performance Dynamic Lock-Free Hash Tables and
* List-Based Sets"
* basic idea in these lists is to mark the "next" pointers of
* deleted nodes when deleting to avoid conflicts with concurrent
* insertions, and when traversing to keep track of triples
* (predecessor, node, successor) in order to detect when and how
* to unlink these deleted nodes.
*
* Rather than using mark-bits to mark list deletions (which can
* be slow and space-intensive using AtomicMarkedReference), nodes
* use direct CAS'able next pointers. On deletion, instead of
* marking a pointer, they splice in another node that can be
* thought of as standing for a marked pointer (indicating this by
* using otherwise impossible field values). Using plain nodes
* acts roughly like "boxed" implementations of marked pointers,
* but uses new nodes only when nodes are deleted, not for every
* link. This requires less space and supports faster
* traversal. Even if marked references were better supported by
* JVMs, traversal using this technique might still be faster
* because any search need only read ahead one more node than
* otherwise required (to check for trailing marker) rather than
* unmasking mark bits or whatever on each read.
*
* This approach maintains the essential property needed in the HM
* algorithm of changing the next-pointer of a deleted node so
* that any other CAS of it will fail, but implements the idea by
* changing the pointer to point to a different node, not by
* marking it. While it would be possible to further squeeze
* isn't worth the extra type-testing overhead. The deletion
* markers are rarely encountered during traversal and are
* normally quickly garbage collected. (Note that this technique
* would not work well in systems without garbage collection.)
*
* In addition to using deletion markers, the lists also use
* nullness of value fields to indicate deletion, in a style
* similar to typical lazy-deletion schemes. If a node's value is
* null, then it is considered logically deleted and ignored even
* though it is still reachable. This maintains proper control of
* concurrent replace vs delete operations -- an attempted replace
* must fail if a delete beat it by nulling field, and a delete
* must return the last non-null value held in the field. (Note:
* Null, rather than some special marker, is used for value fields
* here because it just so happens to mesh with the Map API
* requirement that method get returns null if there is no
* mapping, which allows nodes to remain concurrently readable
* even when deleted. Using any other marker value here would be
* messy at best.)
*
* Here's the sequence of events for a deletion of node n with
* predecessor b and successor f, initially:
*
* +------+ +------+ +------+
* ... | b |------>| n |----->| f | ...
* +------+ +------+ +------+
*
* 1. CAS n's value field from non-null to null.
* From this point on, no public operations encountering
* the node consider this mapping to exist. However, other
* ongoing insertions and deletions might still modify
* n's next pointer.
*
* 2. CAS n's next pointer to point to a new marker node.
* From this point on, no other nodes can be appended to n.
* which avoids deletion errors in CAS-based linked lists.
*
* +------+ +------+ +------+ +------+
* ... | b |------>| n |----->|marker|------>| f | ...
* +------+ +------+ +------+ +------+
*
* 3. CAS b's next pointer over both n and its marker.
* From this point on, no new traversals will encounter n,
* and it can eventually be GCed.
* +------+ +------+
* ... | b |----------------------------------->| f | ...
* +------+ +------+
*
* A failure at step 1 leads to simple retry due to a lost race
* with another operation. Steps 2-3 can fail because some other
* thread noticed during a traversal a node with null value and
* ensures that no thread can become stuck waiting for progress of
* the deleting thread. The use of marker nodes slightly
* complicates helping-out code because traversals must track
* consistent reads of up to four nodes (b, n, marker, f), not
* just (b, n, f), although the next field of a marker is
* immutable, and once a next field is CAS'ed to point to a
* marker, it never again changes, so this requires less care.
*
* Skip lists add indexing to this scheme, so that the base-level
* traversals start close to the locations being found, inserted
* or deleted -- usually base level traversals only traverse a few
* nodes. This doesn't change the basic algorithm except for the
* need to make sure base traversals start at predecessors (here,
* b) that are not (structurally) deleted, otherwise retrying
* after processing the deletion.
*
* Index levels are maintained as lists with volatile next fields,
* using CAS to link and unlink. Races are allowed in index-list
* operations that can (rarely) fail to link in a new index node
* or delete one. (We can't do this of course for data nodes.)
* However, even when this happens, the index lists remain sorted,
* so correctly serve as indices. This can impact performance,
* but since skip lists are probabilistic anyway, the net result
* is that under contention, the effective "p" value may be lower
* than its nominal value. And race windows are kept small enough
* that in practice these failures are rare, even under a lot of
* contention.
*
* The fact that retries (for both base and index lists) are
* relatively cheap due to indexing allows some minor
* simplifications of retry logic. Traversal restarts are
* performed after most "helping-out" CASes. This isn't always
* strictly necessary, but the implicit backoffs tend to help
* reduce other downstream failed CAS's enough to outweigh restart
* cost. This worsens the worst case, but seems to improve even
* highly contended cases.
*
* Unlike most skip-list implementations, index insertion and
* deletion here require a separate traversal pass occuring after
* the base-level action, to add or remove index nodes. This adds
* to single-threaded overhead, but improves contended
* multithreaded performance by narrowing interference windows,
* and allows deletion to ensure that all index nodes will be made
* unreachable upon return from a public remove operation, thus
* avoiding unwanted garbage retention. This is more important
* here than in some other data structures because we cannot null
* out node fields referencing user keys since they might still be
* read by other ongoing traversals.
*
* Indexing uses skip list parameters that maintain good search
* performance while using sparser-than-usual indices: The
* hardwired parameters k=1, p=0.5 (see method randomLevel) mean
* that about one-quarter of the nodes have indices. Of those that
* do, half have one level, a quarter have two, and so on (see
* Pugh's Skip List Cookbook, sec 3.4). The expected total space
* requirement for a map is slightly less than for the current
* implementation of java.util.TreeMap.
*
* Changing the level of the index (i.e, the height of the
* tree-like structure) also uses CAS. The head index has initial
* than the current level adds a level to the head index by
* CAS'ing on a new top-most head. To maintain good performance
* after a lot of removals, deletion methods heuristically try to
* reduce the height if the topmost levels appear to be empty.
* This may encounter races in which it possible (but rare) to
* reduce and "lose" a level just as it is about to contain an
* index (that will then never be encountered). This does no
* structural harm, and in practice appears to be a better option
* than allowing unrestrained growth of levels.
*
* The code for all this is more verbose than you'd like. Most
* operations entail locating an element (or position to insert an
* element). The code to do this can't be nicely factored out
* because subsequent uses require a snapshot of predecessor
* all at once, at least not without creating yet another object
* to hold them -- creating such little objects is an especially
* bad idea for basic internal search operations because it adds
* to GC overhead. (This is one of the few times I've wished Java
* had macros.) Instead, some traversal code is interleaved within
* insertion and removal operations. The control logic to handle
* all the retry conditions is sometimes twisty. Most search is
* broken into 2 parts. findPredecessor() searches index nodes
* only, returning a base-level predecessor of the key. findNode()
* finishes out the base-level search. Even with this factoring,
* there is a fair amount of near-duplication of code to handle
* variants.
*
* For explanation of algorithms sharing at least a couple of
* features with this one, see Mikhail Fomitchev's thesis
* (http://www.cs.yorku.ca/~mikhail/), Keir Fraser's thesis
* (http://www.cl.cam.ac.uk/users/kaf24/), and Hakan Sundell's
* thesis (http://www.cs.chalmers.se/~phs/).
*
* Given the use of tree-like index nodes, you might wonder why
* this doesn't use some kind of search tree instead, which would
* support somewhat faster search operations. The reason is that
* there are no known efficient lock-free insertion and deletion
* algorithms for search trees. The immutability of the "down"
* links of index nodes (as opposed to mutable "left" fields in
* true trees) makes this tractable using only CAS operations.
*
* Notation guide for local variables
* Node: b, n, f for predecessor, node, successor
* Index: q, r, d for index node, right, down.
* t for another index node
* Head: h
* Levels: j
* Keys: k, key
* Values: v, value
* Comparisons: c
*/
/**
* Generates the initial random seed for the cheaper per-instance
* random number generators used in randomLevel.
*/
/**
* Special value used to identify base-level header
*/
/**
* The topmost head index of the skiplist.
*/
/**
* The comparator used to maintain order in this map, or null
* if using natural ordering.
* @serial
*/
/**
* Seed for simple random number generator. Not volatile since it
* doesn't matter too much if different threads don't see updates.
*/
private transient int randomSeed;
/** Lazily initialized key set */
/** Lazily initialized entry set */
/** Lazily initialized values collection */
/** Lazily initialized descending key set */
/**
* Initializes or resets state. Needed by constructors, clone,
* clear, readObject. and ConcurrentSkipListSet.clone.
* (Note that comparator must be separately initialized.)
*/
final void initialize() {
}
/**
* compareAndSet head node
*/
}
/* ---------------- Nodes -------------- */
/**
* Nodes hold keys and values, and are singly linked in sorted
* order, possibly with some intervening marker nodes. The list is
* headed by a dummy node accessible as head.node. The value field
* is declared only as Object because it takes special non-V
* values for marker and header nodes.
*/
static final class Node<K,V> {
final K key;
/**
* Creates a new regular node.
*/
}
/**
* Creates a new marker node. A marker is distinguished by
* having its value field point to itself. Marker nodes also
* have null keys, a fact that is exploited in a few places,
* but this doesn't distinguish markers from the base-level
* header node (head.node), which also has a null key.
*/
this.value = this;
}
/**
* compareAndSet value field
*/
}
/**
* compareAndSet next field
*/
}
/**
* Returns true if this node is a marker. This method isn't
* actually called in any current code checking for markers
* because callers will have already read value field and need
* to use that read (not another done here) and so directly
* test if value points to node.
* @param n a possibly null reference to a node
* @return true if this node is a marker node
*/
boolean isMarker() {
return value == this;
}
/**
* Returns true if this node is the header of base-level list.
* @return true if this node is header node
*/
boolean isBaseHeader() {
return value == BASE_HEADER;
}
/**
* Tries to append a deletion marker to this node.
* @param f the assumed current successor of this node
* @return true if successful
*/
}
/**
* Helps out a deletion by appending marker or unlinking from
* predecessor. This is called during traversals when value
* field seen to be null.
* @param b predecessor
* @param f successor
*/
/*
* Rechecking links and then doing only one of the
* help-out stages per call tends to minimize CAS
* interference among helping threads.
*/
appendMarker(f);
else
}
}
/**
* Returns value if this node contains a valid key-value pair,
* else null.
* @return this node's value if it isn't a marker or header or
* is deleted, else null.
*/
V getValidValue() {
if (v == this || v == BASE_HEADER)
return null;
return (V)v;
}
/**
* Creates and returns a new SimpleImmutableEntry holding current
* mapping if this node holds a valid value, else null.
* @return new entry or null
*/
V v = getValidValue();
if (v == null)
return null;
}
// UNSAFE mechanics
private static final long valueOffset;
private static final long nextOffset;
static {
try {
(k.getDeclaredField("value"));
(k.getDeclaredField("next"));
} catch (Exception e) {
throw new Error(e);
}
}
}
/* ---------------- Indexing -------------- */
/**
* Index nodes represent the levels of the skip list. Note that
* even though both Nodes and Indexes have forward-pointing
* fields, they have different types and are handled in different
* ways, that can't nicely be captured by placing field in a
* shared abstract class.
*/
static class Index<K,V> {
/**
* Creates index node with given values.
*/
}
/**
* compareAndSet right field
*/
}
/**
* Returns true if the node this indexes has been deleted.
* @return true if indexed node is known to be deleted
*/
final boolean indexesDeletedNode() {
}
/**
* Tries to CAS newSucc as successor. To minimize races with
* unlink that may lose this index node, if the node being
* indexed is known to be deleted, it doesn't try to link in.
* @param succ the expected current successor
* @param newSucc the new successor
* @return true if successful
*/
}
/**
* Tries to CAS right field to skip over apparent successor
* succ. Fails (forcing a retraversal by caller) if this node
* is known to be deleted.
* @param succ the expected current successor
* @return true if successful
*/
}
// Unsafe mechanics
private static final long rightOffset;
static {
try {
(k.getDeclaredField("right"));
} catch (Exception e) {
throw new Error(e);
}
}
}
/* ---------------- Head nodes -------------- */
/**
* Nodes heading each level keep track of their level.
*/
final int level;
}
}
/* ---------------- Comparison utilities -------------- */
/**
* Represents a key with a comparator as a Comparable.
*
* Because most sorted collections seem to use natural ordering on
* Comparables (Strings, Integers, etc), most internal methods are
* geared to use them. This is generally faster than checking
* per-comparison whether to use comparator or comparable because
* it doesn't require a (Comparable) cast for each comparison.
* (Optimizers can only sometimes remove such redundant checks
* themselves.) When Comparators are used,
* ComparableUsingComparators are created so that they act in the
* same way as natural orderings. This penalizes use of
* Comparators vs Comparables, which seems like the right
* tradeoff.
*/
final K actualKey;
}
}
}
/**
* If using comparator, return a ComparableUsingComparator, else
* cast key as Comparable, which may cause ClassCastException,
* which is propagated back to caller.
*/
throws ClassCastException {
throw new NullPointerException();
if (comparator != null)
else
return (Comparable<? super K>)key;
}
/**
* Compares using comparator or natural ordering. Used when the
* ComparableUsingComparator approach doesn't apply.
*/
else
}
/**
* Returns true if given key greater than or equal to least and
* strictly less than fence, bypassing either test if least or
* fence are null. Needed mainly in submap operations.
*/
throw new NullPointerException();
}
/**
* Returns true if given key greater than or equal to least and less
* or equal to fence. Needed mainly in submap operations.
*/
throw new NullPointerException();
}
/* ---------------- Traversal -------------- */
/**
* Returns a base-level node with key strictly less than given key,
* or the base-level header if there is no such node. Also
* unlinks indexes to deleted nodes found along the way. Callers
* rely on this side-effect of clearing indices to deleted nodes.
* @param key the key
* @return a predecessor of key
*/
throw new NullPointerException(); // don't postpone errors
for (;;) {
for (;;) {
if (r != null) {
K k = n.key;
if (!q.unlink(r))
break; // restart
r = q.right; // reread r
continue;
}
q = r;
r = r.right;
continue;
}
}
if (d != null) {
q = d;
r = d.right;
} else
return q.node;
}
}
}
/**
* Returns node holding key or null if no such, clearing out any
* deleted nodes seen along the way. Repeatedly traverses at
* base-level looking for key starting at predecessor returned
* from findPredecessor, processing base-level deletions as
* encountered. Some callers rely on this side-effect of clearing
* deleted nodes.
*
* Restarts occur, at traversal step centered on node n, if:
*
* (1) After reading n's next field, n is no longer assumed
* predecessor b's current successor, which means that
* we don't have a consistent 3-node snapshot and so cannot
* unlink any subsequent deleted nodes encountered.
*
* (2) n's value field is null, indicating n is deleted, in
* which case we help out an ongoing structural deletion
* before retrying. Even though there are cases where such
* unlinking doesn't require restart, they aren't sorted out
* here because doing so would not usually outweigh cost of
* restarting.
*
* (3) n is a marker or n's predecessor's value field is null,
* indicating (among other possibilities) that
* findPredecessor returned a deleted node. We can't unlink
* the node because we don't know its predecessor, so rely
* on another call to findPredecessor to notice and return
* some earlier predecessor, which it will do. This check is
* only strictly needed at beginning of loop, (and the
* b.value check isn't strictly needed at all) but is done
* each iteration to help avoid contention with other
* threads by callers that will fail to be able to change
* links, and so will retry anyway.
*
* The traversal loops in doPut, doRemove, and findNear all
* include the same three kinds of checks. And specialized
* versions appear in findFirst, and findLast and their
* variants. They can't easily share code because each uses the
* reads of fields held in locals occurring in the orders they
* were performed.
*
* @param key the key
* @return node holding key, or null if no such
*/
for (;;) {
for (;;) {
if (n == null)
return null;
if (n != b.next) // inconsistent read
break;
if (v == null) { // n is deleted
n.helpDelete(b, f);
break;
}
break;
if (c == 0)
return n;
if (c < 0)
return null;
b = n;
n = f;
}
}
}
/**
* Gets value for key using findNode.
* @param okey the key
* @return the value, or null if absent
*/
/*
* Loop needed here and elsewhere in case value field goes
* null just as it is about to be returned, in which case we
* lost a race with a deletion, so must retry.
*/
for (;;) {
if (n == null)
return null;
if (v != null)
return (V)v;
}
}
/* ---------------- Insertion -------------- */
/**
* Main insertion method. Adds element if not present, or
* replaces value if present and onlyIfAbsent is false.
* @param kkey the key
* @param value the value that must be associated with key
* @param onlyIfAbsent if should not insert if already present
* @return the old value, or null if newly inserted
*/
for (;;) {
for (;;) {
if (n != null) {
if (n != b.next) // inconsistent read
break;
if (v == null) { // n is deleted
n.helpDelete(b, f);
break;
}
break;
if (c > 0) {
b = n;
n = f;
continue;
}
if (c == 0) {
return (V)v;
else
break; // restart if lost race to replace value
}
// else c < 0; fall through
}
if (!b.casNext(n, z))
break; // restart if lost race to append to b
int level = randomLevel();
if (level > 0)
insertIndex(z, level);
return null;
}
}
}
/**
* Returns a random level for inserting a new node.
* Hardwired to k=1, p=0.5, max 31 (see above and
* Pugh's "Skip List Cookbook", sec 3.4).
*
* This uses the simplest of the generators described in George
* Marsaglia's "Xorshift RNGs" paper. This is not a high-quality
* generator but is acceptable here.
*/
private int randomLevel() {
int x = randomSeed;
x ^= x << 13;
x ^= x >>> 17;
randomSeed = x ^= x << 5;
if ((x & 0x80000001) != 0) // test highest and lowest bits
return 0;
int level = 1;
return level;
}
/**
* Creates and adds index nodes for the given node.
* @param z the node
* @param level the level of the index
*/
for (int i = 1; i <= level; ++i)
} else { // Add a new level
/*
* To reduce interference by other threads checking for
* empty levels in tryReduceLevel, new levels are added
* with initialized right pointers. Which in turn requires
* keeping levels in an array to access them while
* creating new head index nodes from the opposite
* direction.
*/
for (int i = 1; i <= level; ++i)
int k;
for (;;) {
k = level;
break;
}
k = oldLevel;
break;
}
}
}
}
/**
* Adds given index nodes from given level down to 1.
* @param idx the topmost index node being inserted
* @param h the value of head to use to insert. This must be
* snapshotted by callers to provide correct insertion level
* @param indexLevel the level of the index
*/
// Track next level to insert in case of retries
int insertionLevel = indexLevel;
// Similar to findPredecessor, but adding index nodes along
// path to key.
for (;;) {
int j = h.level;
Index<K,V> q = h;
for (;;) {
if (r != null) {
// compare before deletion check avoids needing recheck
if (!q.unlink(r))
break;
r = q.right;
continue;
}
if (c > 0) {
q = r;
r = r.right;
continue;
}
}
if (j == insertionLevel) {
// Don't insert index if node already deleted
if (t.indexesDeletedNode()) {
return;
}
if (!q.link(r, t))
break; // restart
if (--insertionLevel == 0) {
// need final deletion check before return
if (t.indexesDeletedNode())
return;
}
}
if (--j >= insertionLevel && j < indexLevel)
t = t.down;
q = q.down;
r = q.right;
}
}
}
/* ---------------- Deletion -------------- */
/**
* Main deletion method. Locates node, nulls value, appends a
* deletion marker, unlinks predecessor, removes associated index
* nodes, and possibly reduces head index level.
*
* Index nodes are cleared out simply by calling findPredecessor.
* which unlinks indexes to deleted nodes found along path to key,
* which will include the indexes to this node. This is done
* unconditionally. We can't check beforehand whether there are
* index nodes because it might be the case that some or all
* indexes hadn't been inserted yet for this node during initial
* search for it, and we'd like to ensure lack of garbage
* retention, so must call to be sure.
*
* @param okey the key
* @param value if non-null, the value that must be
* associated with key
* @return the node, or null if not found
*/
for (;;) {
for (;;) {
if (n == null)
return null;
if (n != b.next) // inconsistent read
break;
if (v == null) { // n is deleted
n.helpDelete(b, f);
break;
}
break;
if (c < 0)
return null;
if (c > 0) {
b = n;
n = f;
continue;
}
return null;
break;
if (!n.appendMarker(f) || !b.casNext(n, f))
else {
}
return (V)v;
}
}
}
/**
* Possibly reduce head level if it has no nodes. This method can
* (rarely) make mistakes, in which case levels can disappear even
* though they are about to contain index nodes. This impacts
* performance, not correctness. To minimize mistakes as well as
* to reduce hysteresis, the level is reduced by one only if the
* topmost three levels look empty. Also, if the removed level
* looks non-empty after CAS, we try to change it back quick
* before anyone notices our mistake! (This trick works pretty
* well because this method will practically never make mistakes
* unless current thread stalls immediately before first CAS, in
* which case it is very unlikely to stall again immediately
* afterwards, so will recover.)
*
* We put up with all this rather than just let levels grow
* because otherwise, even a small map that has undergone a large
* number of insertions and removals will have a lot of levels,
* slowing down access more than would an occasional unwanted
* reduction.
*/
private void tryReduceLevel() {
HeadIndex<K,V> d;
HeadIndex<K,V> e;
if (h.level > 3 &&
casHead(h, d) && // try to set
casHead(d, h); // try to backout
}
/* ---------------- Finding and removing first element -------------- */
/**
* Specialized variant of findNode to get first valid node.
* @return first node or null if empty
*/
for (;;) {
if (n == null)
return null;
return n;
n.helpDelete(b, n.next);
}
}
/**
* Removes first entry; returns its snapshot.
* @return null if empty, else snapshot of first entry
*/
for (;;) {
if (n == null)
return null;
if (n != b.next)
continue;
if (v == null) {
n.helpDelete(b, f);
continue;
}
continue;
if (!n.appendMarker(f) || !b.casNext(n, f))
findFirst(); // retry
}
}
/**
* Clears out index nodes associated with deleted first entry.
*/
private void clearIndexToFirst() {
for (;;) {
for (;;) {
break;
return;
}
}
}
}
/* ---------------- Finding and removing last element -------------- */
/**
* Specialized version of find to get last valid node.
* @return last node or null if empty
*/
/*
* findPredecessor can't be used to traverse index level
* because this doesn't use comparisons. So traversals of
* both levels are folded together.
*/
for (;;) {
Index<K,V> d, r;
if (r.indexesDeletedNode()) {
q.unlink(r);
q = head; // restart
}
else
q = r;
q = d;
} else {
for (;;) {
if (n == null)
return b.isBaseHeader() ? null : b;
if (n != b.next)
break;
if (v == null) { // n is deleted
n.helpDelete(b, f);
break;
}
break;
b = n;
n = f;
}
q = head; // restart
}
}
}
/**
* Specialized variant of findPredecessor to get predecessor of last
* valid node. Needed when removing the last entry. It is possible
* that all successors of returned node will have been deleted upon
* return, in which case this method can be retried.
* @return likely predecessor of last node
*/
for (;;) {
for (;;) {
Index<K,V> d, r;
if (r.indexesDeletedNode()) {
q.unlink(r);
break; // must restart
}
// proceed as far across as possible without overshooting
q = r;
continue;
}
}
q = d;
else
return q.node;
}
}
}
/**
* Removes last entry; returns its snapshot.
* Specialized variant of doRemove.
* @return null if empty, else snapshot of last entry
*/
for (;;) {
Node<K,V> b = findPredecessorOfLast();
if (n == null) {
if (b.isBaseHeader()) // empty
return null;
else
continue; // all b's successors are deleted; retry
}
for (;;) {
if (n != b.next) // inconsistent read
break;
if (v == null) { // n is deleted
n.helpDelete(b, f);
break;
}
break;
if (f != null) {
b = n;
n = f;
continue;
}
break;
if (!n.appendMarker(f) || !b.casNext(n, f))
else {
}
}
}
}
/* ---------------- Relational operations -------------- */
// Control values OR'ed as arguments to findNear
/**
* Utility for ceiling, floor, lower, higher methods.
* @param kkey the key
* @param rel the relation -- OR'ed combination of EQ, LT, GT
* @return nearest node fitting relation, or null if no such
*/
for (;;) {
for (;;) {
if (n == null)
if (n != b.next) // inconsistent read
break;
if (v == null) { // n is deleted
n.helpDelete(b, f);
break;
}
break;
return n;
return b.isBaseHeader() ? null : b;
b = n;
n = f;
}
}
}
/**
* Returns SimpleImmutableEntry for results of findNear.
* @param key the key
* @param rel the relation -- OR'ed combination of EQ, LT, GT
* @return Entry fitting relation, or null if no such
*/
for (;;) {
if (n == null)
return null;
if (e != null)
return e;
}
}
/* ---------------- Constructors -------------- */
/**
* Constructs a new, empty map, sorted according to the
* {@linkplain Comparable natural ordering} of the keys.
*/
public ConcurrentSkipListMap() {
this.comparator = null;
initialize();
}
/**
* Constructs a new, empty map, sorted according to the specified
* comparator.
*
* @param comparator the comparator that will be used to order this map.
* If <tt>null</tt>, the {@linkplain Comparable natural
* ordering} of the keys will be used.
*/
this.comparator = comparator;
initialize();
}
/**
* Constructs a new map containing the same mappings as the given map,
* sorted according to the {@linkplain Comparable natural ordering} of
* the keys.
*
* @param m the map whose mappings are to be placed in this map
* @throws ClassCastException if the keys in <tt>m</tt> are not
* {@link Comparable}, or are not mutually comparable
* @throws NullPointerException if the specified map or any of its keys
* or values are null
*/
this.comparator = null;
initialize();
putAll(m);
}
/**
* Constructs a new map containing the same mappings and using the
* same ordering as the specified sorted map.
*
* @param m the sorted map whose mappings are to be placed in this
* map, and whose comparator is to be used to sort this map
* @throws NullPointerException if the specified sorted map or any of
* its keys or values are null
*/
this.comparator = m.comparator();
initialize();
buildFromSorted(m);
}
/**
* Returns a shallow copy of this <tt>ConcurrentSkipListMap</tt>
* instance. (The keys and values themselves are not cloned.)
*
* @return a shallow copy of this map
*/
try {
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
clone.initialize();
clone.buildFromSorted(this);
return clone;
}
/**
* Streamlined bulk insertion to initialize from elements of
* given sorted map. Call only from constructor or clone
* method.
*/
throw new NullPointerException();
// Track the current rightmost node at each level. Uses an
// ArrayList to avoid committing to initial or maximum level.
// initialize
for (int i = 0; i <= h.level; ++i)
Index<K,V> q = h;
for (int i = h.level; i > 0; --i) {
q = q.down;
}
int j = randomLevel();
K k = e.getKey();
V v = e.getValue();
throw new NullPointerException();
basepred = z;
if (j > 0) {
for (int i = 1; i <= j; ++i) {
if (i > h.level)
} else
}
}
}
head = h;
}
/* ---------------- Serialization -------------- */
/**
* Save the state of this map to a stream.
*
* @serialData The key (Object) and value (Object) for each
* key-value mapping represented by the map, followed by
* <tt>null</tt>. The key-value mappings are emitted in key-order
* (as determined by the Comparator, or by the keys' natural
* ordering if no Comparator).
*/
// Write out the Comparator and any hidden stuff
s.defaultWriteObject();
// Write out keys and values (alternating)
V v = n.getValidValue();
if (v != null) {
s.writeObject(n.key);
s.writeObject(v);
}
}
s.writeObject(null);
}
/**
* Reconstitute the map from a stream.
*/
// Read in the Comparator and any hidden stuff
s.defaultReadObject();
// Reset transients
initialize();
/*
* This is nearly identical to buildFromSorted, but is
* distinct because readObject calls can't be nicely adapted
* as the kind of iterator needed by buildFromSorted. (They
* of adaptor classes.) It is simpler to just adapt the code.
*/
for (int i = 0; i <= h.level; ++i)
Index<K,V> q = h;
for (int i = h.level; i > 0; --i) {
q = q.down;
}
for (;;) {
Object k = s.readObject();
if (k == null)
break;
Object v = s.readObject();
if (v == null)
throw new NullPointerException();
K key = (K) k;
V val = (V) v;
int j = randomLevel();
basepred = z;
if (j > 0) {
for (int i = 1; i <= j; ++i) {
if (i > h.level)
} else
}
}
}
head = h;
}
/* ------ Map API methods ------ */
/**
* Returns <tt>true</tt> if this map contains a mapping for the specified
* key.
*
* @param key key whose presence in this map is to be tested
* @return <tt>true</tt> if this map contains a mapping for the specified key
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if the specified key is null
*/
}
/**
* 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} compares
* equal to {@code k} according to the map's ordering, then this
* method returns {@code v}; otherwise it returns {@code null}.
* (There can be at most one such mapping.)
*
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if the specified key is null
*/
}
/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for the key, the old
* value is replaced.
*
* @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 the specified key, or
* <tt>null</tt> if there was no mapping for the key
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if the specified key or value is null
*/
throw new NullPointerException();
}
/**
* Removes the mapping for the specified key from this map if present.
*
* @param key key for which mapping should be removed
* @return the previous value associated with the specified key, or
* <tt>null</tt> if there was no mapping for the key
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if the specified key is null
*/
}
/**
* Returns <tt>true</tt> if this map maps one or more keys to the
* specified value. This operation requires time linear in the
* map size. Additionally, it is possible for the map to change
* during execution of this method, in which case the returned
* result may be inaccurate.
*
* @param value value whose presence in this map is to be tested
* @return <tt>true</tt> if a mapping to <tt>value</tt> exists;
* <tt>false</tt> otherwise
* @throws NullPointerException if the specified value is null
*/
throw new NullPointerException();
V v = n.getValidValue();
return true;
}
return false;
}
/**
* Returns the number of key-value mappings in this map. If this map
* contains more than <tt>Integer.MAX_VALUE</tt> elements, it
* returns <tt>Integer.MAX_VALUE</tt>.
*
* <p>Beware that, unlike in most collections, this method is
* <em>NOT</em> a constant-time operation. Because of the
* asynchronous nature of these maps, determining the current
* number of elements requires traversing them all to count them.
* Additionally, it is possible for the size to change during
* execution of this method, in which case the returned result
* will be inaccurate. Thus, this method is typically not very
* useful in concurrent applications.
*
* @return the number of elements in this map
*/
public int size() {
long count = 0;
if (n.getValidValue() != null)
++count;
}
}
/**
* Returns <tt>true</tt> if this map contains no key-value mappings.
* @return <tt>true</tt> if this map contains no key-value mappings
*/
public boolean isEmpty() {
}
/**
* Removes all of the mappings from this map.
*/
public void clear() {
initialize();
}
/* ---------------- View methods -------------- */
/*
* Note: Lazy initialization works for views because view classes
* more than one is created (which will only rarely happen). Even
* so, the following idiom conservatively ensures that the method
* returns the one it created if it does so, not one created by
* another racing thread.
*/
/**
* Returns a {@link NavigableSet} view of the keys contained in this map.
* The set's iterator returns the keys in ascending order.
* 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. 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.
*
* <p>This method is equivalent to method {@code navigableKeySet}.
*
* @return a navigable set view of the keys in this map
*/
}
}
/**
* Returns a {@link Collection} view of the values contained in this map.
* The collection's iterator returns the values in ascending order
* of the corresponding keys.
* 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 the map, via the <tt>Iterator.remove</tt>,
* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
* <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
* support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> 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.
*/
}
/**
* Returns a {@link Set} view of the mappings contained in this map.
* The set's iterator returns the entries in ascending key order.
* 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 <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt> and <tt>clear</tt>
* operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* <p>The view's <tt>iterator</tt> 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.
*
* <p>The <tt>Map.Entry</tt> elements returned by
* <tt>iterator.next()</tt> do <em>not</em> support the
* <tt>setValue</tt> operation.
*
* @return a set view of the mappings contained in this map,
* sorted in ascending key order
*/
}
}
return descendingMap().navigableKeySet();
}
/* ---------------- AbstractMap Overrides -------------- */
/**
* Compares the specified object with this map for equality.
* Returns <tt>true</tt> if the given object is also a map and the
* two maps represent the same mappings. More formally, two maps
* <tt>m1</tt> and <tt>m2</tt> represent the same mappings if
* <tt>m1.entrySet().equals(m2.entrySet())</tt>. 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 <tt>true</tt> if the specified object is equal to this map
*/
if (o == this)
return true;
if (!(o instanceof Map))
return false;
try {
return false;
return false;
}
return true;
} catch (ClassCastException unused) {
return false;
} catch (NullPointerException unused) {
return false;
}
}
/* ------ ConcurrentMap API methods ------ */
/**
* {@inheritDoc}
*
* @return the previous value associated with the specified key,
* or <tt>null</tt> if there was no mapping for the key
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if the specified key or value is null
*/
throw new NullPointerException();
}
/**
* {@inheritDoc}
*
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if the specified key is null
*/
throw new NullPointerException();
return false;
}
/**
* {@inheritDoc}
*
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if any of the arguments are null
*/
throw new NullPointerException();
for (;;) {
if (n == null)
return false;
if (v != null) {
return false;
return true;
}
}
}
/**
* {@inheritDoc}
*
* @return the previous value associated with the specified key,
* or <tt>null</tt> if there was no mapping for the key
* @throws ClassCastException if the specified key cannot be compared
* with the keys currently in the map
* @throws NullPointerException if the specified key or value is null
*/
throw new NullPointerException();
for (;;) {
if (n == null)
return null;
return (V)v;
}
}
/* ------ SortedMap API methods ------ */
return comparator;
}
/**
* @throws NoSuchElementException {@inheritDoc}
*/
public K firstKey() {
if (n == null)
throw new NoSuchElementException();
return n.key;
}
/**
* @throws NoSuchElementException {@inheritDoc}
*/
public K lastKey() {
if (n == null)
throw new NoSuchElementException();
return n.key;
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromKey} or {@code toKey} is null
* @throws IllegalArgumentException {@inheritDoc}
*/
boolean fromInclusive,
K toKey,
boolean toInclusive) {
throw new NullPointerException();
return new SubMap<K,V>
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code toKey} is null
* @throws IllegalArgumentException {@inheritDoc}
*/
boolean inclusive) {
throw new NullPointerException();
return new SubMap<K,V>
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromKey} is null
* @throws IllegalArgumentException {@inheritDoc}
*/
boolean inclusive) {
throw new NullPointerException();
return new SubMap<K,V>
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromKey} or {@code toKey} is null
* @throws IllegalArgumentException {@inheritDoc}
*/
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code toKey} is null
* @throws IllegalArgumentException {@inheritDoc}
*/
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromKey} is null
* @throws IllegalArgumentException {@inheritDoc}
*/
}
/* ---------------- Relational operations -------------- */
/**
* Returns a key-value mapping associated with the greatest key
* strictly less than the given key, or <tt>null</tt> if there is
* no such key. The returned entry does <em>not</em> support the
* <tt>Entry.setValue</tt> method.
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* Returns a key-value mapping associated with the greatest key
* less than or equal to the given key, or <tt>null</tt> if there
* is no such key. The returned entry does <em>not</em> support
* the <tt>Entry.setValue</tt> method.
*
* @param key the key
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* @param key the key
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* Returns a key-value mapping associated with the least key
* greater than or equal to the given key, or <tt>null</tt> if
* there is no such entry. The returned entry does <em>not</em>
* support the <tt>Entry.setValue</tt> method.
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* Returns a key-value mapping associated with the least key
* strictly greater than the given key, or <tt>null</tt> if there
* is no such key. The returned entry does <em>not</em> support
* the <tt>Entry.setValue</tt> method.
*
* @param key the key
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* @param key the key
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
}
/**
* Returns a key-value mapping associated with the least
* key in this map, or <tt>null</tt> if the map is empty.
* The returned entry does <em>not</em> support
* the <tt>Entry.setValue</tt> method.
*/
for (;;) {
if (n == null)
return null;
if (e != null)
return e;
}
}
/**
* Returns a key-value mapping associated with the greatest
* key in this map, or <tt>null</tt> if the map is empty.
* The returned entry does <em>not</em> support
* the <tt>Entry.setValue</tt> method.
*/
for (;;) {
if (n == null)
return null;
if (e != null)
return e;
}
}
/**
* Removes and returns a key-value mapping associated with
* the least key in this map, or <tt>null</tt> if the map is empty.
* The returned entry does <em>not</em> support
* the <tt>Entry.setValue</tt> method.
*/
return doRemoveFirstEntry();
}
/**
* Removes and returns a key-value mapping associated with
* the greatest key in this map, or <tt>null</tt> if the map is empty.
* The returned entry does <em>not</em> support
* the <tt>Entry.setValue</tt> method.
*/
return doRemoveLastEntry();
}
/* ---------------- Iterators -------------- */
/**
* Base of iterator classes:
*/
/** the last node returned by next() */
/** the next node to return from next(); */
/** Cache of next value field to maintain weak consistency */
V nextValue;
/** Initializes ascending iterator for entire range. */
Iter() {
for (;;) {
break;
nextValue = (V) x;
break;
}
}
}
public final boolean hasNext() {
}
/** Advances next to higher entry. */
final void advance() {
throw new NoSuchElementException();
lastReturned = next;
for (;;) {
break;
nextValue = (V) x;
break;
}
}
}
public void remove() {
Node<K,V> l = lastReturned;
if (l == null)
throw new IllegalStateException();
// It would not be worth all of the overhead to directly
// unlink from here. Using remove is fast enough.
lastReturned = null;
}
}
public V next() {
V v = nextValue;
advance();
return v;
}
}
public K next() {
advance();
return n.key;
}
}
V v = nextValue;
advance();
}
}
// Factory methods for iterators needed by ConcurrentSkipListSet etc
return new KeyIterator();
}
return new ValueIterator();
}
return new EntryIterator();
}
/* ---------------- View Classes -------------- */
/*
* View classes are static, delegating to a ConcurrentNavigableMap
* to allow use by SubMaps, which outweighs the ugliness of
* needing type-tests for Iterator methods.
*/
// Using size() here would be a pessimization.
for (E e : c)
return list;
}
static final class KeySet<E>
extends AbstractSet<E> implements NavigableSet<E> {
private final ConcurrentNavigableMap<E,Object> m;
public E pollFirst() {
}
public E pollLast() {
}
if (m instanceof ConcurrentSkipListMap)
else
}
if (o == this)
return true;
if (!(o instanceof Set))
return false;
Collection<?> c = (Collection<?>) o;
try {
return containsAll(c) && c.containsAll(this);
} catch (ClassCastException unused) {
return false;
} catch (NullPointerException unused) {
return false;
}
}
return descendingSet().iterator();
}
boolean fromInclusive,
E toElement,
boolean toInclusive) {
toElement, toInclusive));
}
}
}
}
}
return tailSet(fromElement, true);
}
return new KeySet(m.descendingMap());
}
}
private final ConcurrentNavigableMap<Object, E> m;
m = map;
}
if (m instanceof ConcurrentSkipListMap)
else
}
public boolean isEmpty() {
return m.isEmpty();
}
public int size() {
return m.size();
}
return m.containsValue(o);
}
public void clear() {
m.clear();
}
}
m = map;
}
if (m instanceof ConcurrentSkipListMap)
else
}
return false;
}
return false;
e.getValue());
}
public boolean isEmpty() {
return m.isEmpty();
}
public int size() {
return m.size();
}
public void clear() {
m.clear();
}
if (o == this)
return true;
if (!(o instanceof Set))
return false;
Collection<?> c = (Collection<?>) o;
try {
return containsAll(c) && c.containsAll(this);
} catch (ClassCastException unused) {
return false;
} catch (NullPointerException unused) {
return false;
}
}
}
/**
* Submaps returned by {@link ConcurrentSkipListMap} submap operations
* represent a subrange of mappings of their underlying
* maps. Instances of this class support all methods of their
* underlying maps, differing in that mappings outside their range are
* ignored, and attempts to add mappings outside their ranges result
* in {@link IllegalArgumentException}. Instances of this class are
* constructed only using the <tt>subMap</tt>, <tt>headMap</tt>, and
* <tt>tailMap</tt> methods of their underlying maps.
*
* @serial include
*/
implements ConcurrentNavigableMap<K,V>, Cloneable,
/** Underlying map */
private final ConcurrentSkipListMap<K,V> m;
/** lower bound key, or null if from start */
private final K lo;
/** upper bound key, or null if to end */
private final K hi;
/** inclusion flag for lo */
private final boolean loInclusive;
/** inclusion flag for hi */
private final boolean hiInclusive;
/** direction */
private final boolean isDescending;
// Lazily initialized view holders
/**
* Creates a new submap, initializing all fields
*/
K fromKey, boolean fromInclusive,
K toKey, boolean toInclusive,
boolean isDescending) {
throw new IllegalArgumentException("inconsistent range");
this.m = map;
this.loInclusive = fromInclusive;
this.hiInclusive = toInclusive;
this.isDescending = isDescending;
}
/* ---------------- Utilities -------------- */
return true;
}
return false;
}
return true;
}
return false;
}
}
throw new NullPointerException();
throw new IllegalArgumentException("key out of range");
}
/**
* Returns true if node key is less than upper bound of range
*/
if (n == null)
return false;
return true;
K k = n.key;
if (k == null) // pass by markers and headers
return true;
return false;
return true;
}
/**
* Returns lowest node. This node might not be in range, so
* most usages need to check bounds
*/
return m.findFirst();
else if (loInclusive)
else
}
/**
* Returns highest node. This node might not be in range, so
* most usages need to check bounds
*/
return m.findLast();
else if (hiInclusive)
else
}
/**
* Returns lowest absolute key (ignoring directonality)
*/
private K lowestKey() {
if (isBeforeEnd(n))
return n.key;
else
throw new NoSuchElementException();
}
/**
* Returns highest absolute key (ignoring directonality)
*/
private K highestKey() {
if (n != null) {
return last;
}
throw new NoSuchElementException();
}
for (;;) {
if (!isBeforeEnd(n))
return null;
if (e != null)
return e;
}
}
for (;;) {
return null;
if (e != null)
return e;
}
}
for (;;) {
if (n == null)
return null;
K k = n.key;
if (!inBounds(k))
return null;
if (v != null)
return new AbstractMap.SimpleImmutableEntry<K,V>(k, v);
}
}
for (;;) {
if (n == null)
return null;
K k = n.key;
if (!inBounds(k))
return null;
if (v != null)
return new AbstractMap.SimpleImmutableEntry<K,V>(k, v);
}
}
/**
* Submap version of ConcurrentSkipListMap.getNearEntry
*/
if (isDescending) { // adjust relation for direction
else
}
for (;;) {
return null;
K k = n.key;
V v = n.getValidValue();
if (v != null)
return new AbstractMap.SimpleImmutableEntry<K,V>(k, v);
}
}
// Almost the same as getNearEntry, except for keys
if (isDescending) { // adjust relation for direction
else
}
if (isBeforeEnd(n))
return n.key;
}
return null;
}
if (n != null) {
return last;
}
}
return null;
}
for (;;) {
return null;
K k = n.key;
V v = n.getValidValue();
if (v != null)
return k;
}
}
/* ---------------- Map API methods -------------- */
K k = (K)key;
return inBounds(k) && m.containsKey(k);
}
K k = (K)key;
}
}
K k = (K)key;
}
public int size() {
long count = 0;
isBeforeEnd(n);
n = n.next) {
if (n.getValidValue() != null)
++count;
}
}
public boolean isEmpty() {
return !isBeforeEnd(loNode());
}
throw new NullPointerException();
isBeforeEnd(n);
n = n.next) {
V v = n.getValidValue();
return true;
}
return false;
}
public void clear() {
isBeforeEnd(n);
n = n.next) {
if (n.getValidValue() != null)
}
}
/* ---------------- ConcurrentMap API methods -------------- */
}
K k = (K)key;
}
}
}
/* ---------------- SortedMap API methods -------------- */
if (isDescending)
else
return cmp;
}
/**
* Utility to create submaps, where given bounds override
*/
boolean fromInclusive,
K toKey,
boolean toInclusive) {
if (isDescending) { // flip senses
boolean ti = fromInclusive;
toInclusive = ti;
}
}
else {
throw new IllegalArgumentException("key out of range");
}
}
}
else {
throw new IllegalArgumentException("key out of range");
}
}
}
boolean fromInclusive,
K toKey,
boolean toInclusive) {
throw new NullPointerException();
}
boolean inclusive) {
throw new NullPointerException();
}
boolean inclusive) {
throw new NullPointerException();
}
}
}
}
}
/* ---------------- Relational methods -------------- */
}
}
}
}
}
}
}
}
public K firstKey() {
}
public K lastKey() {
}
}
}
}
}
/* ---------------- Submap Views -------------- */
}
}
}
}
return descendingMap().navigableKeySet();
}
return new SubMapKeyIterator();
}
return new SubMapValueIterator();
}
return new SubMapEntryIterator();
}
/**
* Variant of main Iter class to traverse through submaps.
*/
/** the last node returned by next() */
/** the next node to return from next(); */
/** Cache of next value field to maintain weak consistency */
V nextValue;
SubMapIter() {
for (;;) {
break;
else
nextValue = (V) x;
break;
}
}
}
public final boolean hasNext() {
}
final void advance() {
throw new NoSuchElementException();
lastReturned = next;
if (isDescending)
descend();
else
ascend();
}
private void ascend() {
for (;;) {
break;
else
nextValue = (V) x;
break;
}
}
}
private void descend() {
for (;;) {
break;
else
nextValue = (V) x;
break;
}
}
}
public void remove() {
Node<K,V> l = lastReturned;
if (l == null)
throw new IllegalStateException();
lastReturned = null;
}
}
public V next() {
V v = nextValue;
advance();
return v;
}
}
public K next() {
advance();
return n.key;
}
}
V v = nextValue;
advance();
}
}
}
// Unsafe mechanics
private static final long headOffset;
static {
try {
Class k = ConcurrentSkipListMap.class;
(k.getDeclaredField("head"));
} catch (Exception e) {
throw new Error(e);
}
}
}