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com.tangosol.util
Class SegmentedHashMap

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.SegmentedHashMap

All Implemented Interfaces:

Map

Direct Known Subclasses:

SegmentedConcurrentMap

public class SegmentedHashMap

extends Base

implements Map

An implementation of java.util.Map that is optimized for heavy concurrent use. <p/> Retrieval and update operations to the map (e.g. get, put) are non-blocking and uncontended and will reflect some state of the map. Insert and remove operations to the map (e.g. put, remove) do require internal locking. <p/> The entries in the map are internally segmented so as to permit a high level of concurrent "locked" operations without contention. <p/> Retrievals and updates that run concurrently with bulk operations (e.g. putAll, clear may reflect insertion or removal of only some entries. Iterators on the Map may also reflect concurrent updates made since the Iterator was created. However, Iterators will not throw ConcurrentModificationException.

Since:

Coherence 3.5

Author:

rhl 2008.12.01

Nested Class Summary

protected static class	SegmentedHashMap.ContainsValueAction Action support for containsValue().
protected static class	SegmentedHashMap.Entry A map entry (key-value pair).
protected static interface	SegmentedHashMap.EntryAction An EntryAction encapsulates a logical action to be executed in the context of a key (that may or may not exist in the map).
protected static class	SegmentedHashMap.EntryActionAdapter EntryActionAdapter is a convenience class that provides default implementations for the EntryAction and IterableEntryAction interface methods.
protected class	SegmentedHashMap.EntrySet A set of entries backed by this map.
protected class	SegmentedHashMap.GetEntryAction Action support for getEntryInternal.
protected class	SegmentedHashMap.InsertAction Action support for insert.
protected static interface	SegmentedHashMap.IterableEntryAction IterableEntryAction is an EntryAction that is suitable for applying to all keys in a map.
protected class	SegmentedHashMap.KeySet A set of entries backed by this map.
protected class	SegmentedHashMap.RemoveAction Action support for remove().
protected static class	SegmentedHashMap.Segment Segment metadata.
protected class	SegmentedHashMap.ValuesCollection A collection of values backed by this map.

Field Summary

protected static int	BIGGEST_MODULO Biggest possible modulo.
static float	DEFAULT_GROWTHRATE Using the default growth rate, the bucket array will grow by a factor of four.
static int	DEFAULT_INITIALSIZE Default initial size provides a prime modulo and is large enough that resize is not immediate.
static float	DEFAULT_LOADFACTOR The default load factor is 100%, which means that the hash map will not resize until there is (on average) one entry in every bucket.
protected static long	LOCK_ALL_PENDING The bit-mask used to indicate that a lock-all is pending.
protected static int	LOCK_ALL_PENDING_IDX The mutex number used to indicate that a lock-all is pending.
protected static int	LOCK_COUNT The number of segment-locks.
protected static long	LOCKS_ALL The lock representation used to indicate that all mutexes are locked.
protected static long	LOCKS_NONE The lock representation used to indicate that no locks are set.
protected SegmentedHashMap.ContainsValueAction	m_actionContainsValue The singleton action for containsValue support.
protected SegmentedHashMap.GetEntryAction	m_actionGetEntry The singleton action for getEntryInternal support.
protected SegmentedHashMap.InsertAction	m_actionInsert The singleton action for insert support.
protected SegmentedHashMap.RemoveAction	m_actionRemove The singleton action for remove support.
protected SegmentedHashMap.Entry[]	m_aeBucket The array of hash buckets.
protected SegmentedHashMap.Segment[]	m_aSegment An array of the control-structures for the Map's segments.
protected AtomicCounter	m_atomicLocks The "segment-locks".
protected SegmentedHashMap.ValuesCollection	m_colValues The collection of values backed by this map.
protected int	m_cSegmentCapacity The capacity of each segment (the point at which we should resize).
protected float	m_flGrowthRate The rate of growth as a fraction of the current number of buckets, 0 < n, such that the hash map grows to bucketcount * (1 + growth-rate).
protected float	m_flLoadFactor The determining factor for the hash map capacity given a certain number of buckets, such that capacity = bucketcount * loadfactor.
protected Object	m_oIterActive A holder for active Iterator(s): either WeakReference(<Iterator>) or WeakHashMap(<Iterator>, null)
protected SegmentedHashMap.EntrySet	m_setEntries The set of entries backed by this map.
protected SegmentedHashMap.KeySet	m_setKeys The set of keys backed by this map.
protected static int	MIN_SEGMENT_CAPACITY The minimum segment capacity.
protected static Object	NO_VALUE Object to be used as a value representing that the Entry object is "synthetic" and while logically associated with a key, does not represent a key-value mapping in the Map.
protected static int[]	PRIME_MODULO A list of possible modulos to use.
protected static int	PUTALL_THRESHOLD Size threshold used by the putAll operation.
protected Object	RESIZING When resizing completes, a notification is issued against this object.
protected static int	SEGMENT_COUNT The number of segments to partition the hash buckets into.
protected static int	SEGMENT_LOCK_MAX_SPIN Maximum number of times to spin while trying to acquire a segment lock before waiting.

Constructor Summary

SegmentedHashMap()
Default constructor.

SegmentedHashMap(int cInitialBuckets, float flLoadFactor, float flGrowthRate)
Construct a thread-safe hash map using the specified settings.

Method Summary

void	clear() Removes all mappings from this map.
boolean	containsKey(Object oKey) Returns true iff this map contains a mapping for the specified key.
boolean	containsValue(Object oValue) Returns true if this map maps one or more keys to the specified value.
protected void	contendForSegment(int nSegment) Wait for a segment to be unlocked.
protected void	ensureLoadFactor(SegmentedHashMap.Segment segment) Check whether or not the specified segment is overloaded and if so, grow the bucket array (which suggests with high probability that the per-segment load will decrease).
protected static SegmentedHashMap.Entry	entryFromBucket(SegmentedHashMap.Entry[] aeBucket, int nBucket) Return the first non-synthetic Entry object contained by in the specified bucket.
Set	entrySet() Returns a set view of the mappings contained in this map.
boolean	equals(Object oThat) Compares the specified object with this map for equality.
Object	get(Object oKey) Returns the value to which this map maps the specified key.
protected int	getBucketIndex(int nHash, int cBuckets) Calculate the bucket number for a particular hash code.
protected SegmentedHashMap.ContainsValueAction	getContainsValueAction() Return the registered action for containsValue().
Map.Entry	getEntry(Object key) Locate an Entry in the this map based on its key.
protected SegmentedHashMap.Entry	getEntryInternal(Object oKey) Locate an Entry in the hash map based on its key.
protected SegmentedHashMap.Entry	getEntryInternal(Object oKey, boolean fSynthetic) Locate an Entry in the hash map based on its key.
protected SegmentedHashMap.GetEntryAction	getGetEntryAction() Return the registered action for getEntryInternal.
protected SegmentedHashMap.InsertAction	getInsertAction() Return the registered action for insert.
protected SegmentedHashMap.RemoveAction	getRemoveAction() Return the registered action for remove().
protected SegmentedHashMap.Segment	getSegmentForKey(Object oKey) Return the Segment object for the specified key.
protected int	getSegmentIndex(int nBucket) Calculate the segment index for the the specified bucket.
protected SegmentedHashMap.Entry[]	getStableBucketArray() Get the bucket array, or if a resize is occurring, wait for the resize to complete and return the new bucket array.
protected void	grow() Resize the bucket array, rehashing all Entries.
protected void	grow(int cNew) Resize the bucket array to the specified size, rehashing all Entries.
int	hashCode() Returns the hash code value for this Map.
protected void	initializeActions() Initialize the EntryAction's for this map.
protected SegmentedHashMap.ContainsValueAction	instantiateContainsValueAction() Factory for ContainsValueAction
protected SegmentedHashMap.Entry	instantiateEntry(Object oKey, Object oValue, int nHash) Factory for Entry.
protected SegmentedHashMap.EntrySet	instantiateEntrySet() Factory for EntrySet
protected SegmentedHashMap.GetEntryAction	instantiateGetEntryAction() Factory for GetEntryAction
protected SegmentedHashMap.InsertAction	instantiateInsertAction() Factory for InsertAction
protected SegmentedHashMap.KeySet	instantiateKeySet() Factory for KeySet.
protected SegmentedHashMap.RemoveAction	instantiateRemoveAction() Factory for RemoveAction
protected SegmentedHashMap.ValuesCollection	instantiateValuesCollection() Factory for ValuesCollection.
protected Object	invokeOnAllKeys(Object oContext, boolean fLock, SegmentedHashMap.IterableEntryAction actionEntry) Perform an action on all Entries in the map.
protected Object	invokeOnKey(Object oKey, Object oContext, boolean fLock, SegmentedHashMap.EntryAction action) Perform an action on the specified key.
protected boolean	isActiveIterator() Determine if there are any active Iterators, which may mean that they are in the middle of iterating over the Map.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
protected void	iteratorActivated(Iterator iter) Register the activation of an Iterator.
Set	keySet() Returns a Set view of the keys contained in this map.
protected void	lockAllBuckets() Lock everything.
protected boolean	lockAllBuckets(int nBucketAlreadyLocked) Lock everything, assuming that the segment for the specified bucket has already been locked.
protected boolean	lockAllSegments(long lLocksHeld) Lock all segments except for the specified segments that have already been locked by the calling thread.
protected boolean	lockBucket(int nBucket) Attempt to lock the segment corresponding to the specified bucket.
protected boolean	lockSegment(int nSegment, boolean fBlock) Attempt to lock the specified segment.
Object	put(Object oKey, Object oValue) Associates the specified value with the specified key in this map.
void	putAll(Map mapOther) Copies all of the mappings from the specified map to this map.
protected Object	putInternal(Object oKey, Object oValue) Associates the specified value with the specified key in this map.
void	releaseIterator(Iterator iter) Release the (formerly-active) Iterator.
Object	remove(Object oKey) Removes the mapping for this key from this map if present.
protected Object	removeInternal(Object oKey) Removes the mapping for this key from this map if present.
protected void	setContainsValueAction(SegmentedHashMap.ContainsValueAction action) Specify the action for containsValue().
protected void	setGetEntryAction(SegmentedHashMap.GetEntryAction action) Specify the action for getEntryInternal.
protected void	setInsertAction(SegmentedHashMap.InsertAction action) Specify the action for insert.
protected void	setRemoveAction(SegmentedHashMap.RemoveAction action) Specify the action for remove().
int	size() Returns the number of key-value mappings in this map.
protected Object[]	toArrayInternal(SegmentedHashMap.IterableEntryAction action, Object[] a) Apply the specified toArray() action to the entries in the map.
String	toString() Returns a String representation of this map.
protected void	unlockAllBuckets() Unlock everything.
protected void	unlockAllBuckets(int nBucketLeaveLocked) Unlock everything, leaving only the segment for the specified bucket locked.
protected void	unlockAllSegments(long lLocksKeep) Unlock all segments, except the segment-locks indicated by the specified bit-vector.
protected void	unlockBucket(int nBucket) Unlock the segment corresponding to the specified bucket that was previously locked using the lockBucket(int) method.
protected void	unlockSegment(int nSegment) Unlock the specified segment previously locked using the lockSegment(int, boolean) method.
Collection	values() Returns a collection view of the values contained in this map.

Field Detail

PRIME_MODULO

protected static final int[] PRIME_MODULO

A list of possible modulos to use.

DEFAULT_INITIALSIZE

public static final int DEFAULT_INITIALSIZE

Default initial size provides a prime modulo and is large enough that resize is not immediate. (A hash map probably uses less than 128 bytes initially.)

BIGGEST_MODULO

protected static final int BIGGEST_MODULO

Biggest possible modulo.

DEFAULT_LOADFACTOR

public static final float DEFAULT_LOADFACTOR

The default load factor is 100%, which means that the hash map will not resize until there is (on average) one entry in every bucket. The cost of scanning a linked list in a particular bucket is very low, so there is little reason for having this value below 1.0, and the goal is constant order access, so assuming a perfect hash this will provide the optimal access speed relative to size.

See Also:

Constant Field Values

DEFAULT_GROWTHRATE

public static final float DEFAULT_GROWTHRATE

Using the default growth rate, the bucket array will grow by a factor of four. The relatively high growth rate helps to ensure less resize operations, an important consideration in a high-concurrency map.

See Also:

Constant Field Values

MIN_SEGMENT_CAPACITY

protected static final int MIN_SEGMENT_CAPACITY

The minimum segment capacity.

See Also:

Constant Field Values

SEGMENT_COUNT

protected static final int SEGMENT_COUNT

The number of segments to partition the hash buckets into. There is a single lock for each segment. This number is specially chosen as 61 is the largest prime number smaller than 64 (the size of the datatype used to represent the lock).

See Also:

Constant Field Values

LOCK_COUNT

protected static final int LOCK_COUNT

The number of segment-locks. Each segment has its own lock and there is a global "intention" lock.

See Also:

Constant Field Values

LOCKS_NONE

protected static final long LOCKS_NONE

The lock representation used to indicate that no locks are set.

See Also:

Constant Field Values

LOCKS_ALL

protected static final long LOCKS_ALL

The lock representation used to indicate that all mutexes are locked.

See Also:

Constant Field Values

LOCK_ALL_PENDING_IDX

protected static final int LOCK_ALL_PENDING_IDX

The mutex number used to indicate that a lock-all is pending.

See Also:

Constant Field Values

LOCK_ALL_PENDING

protected static final long LOCK_ALL_PENDING

The bit-mask used to indicate that a lock-all is pending.

See Also:

Constant Field Values

SEGMENT_LOCK_MAX_SPIN

protected static final int SEGMENT_LOCK_MAX_SPIN

Maximum number of times to spin while trying to acquire a segment lock before waiting.

See Also:

Constant Field Values

PUTALL_THRESHOLD

protected static final int PUTALL_THRESHOLD

Size threshold used by the putAll operation.

See Also:

Constant Field Values

NO_VALUE

protected static final Object NO_VALUE

Object to be used as a value representing that the Entry object is "synthetic" and while logically associated with a key, does not represent a key-value mapping in the Map.

RESIZING

protected final Object RESIZING

When resizing completes, a notification is issued against this object.

m_atomicLocks

protected final AtomicCounter m_atomicLocks

The "segment-locks". This AtomicCounter is actually used just as an "Atomic Long" value, with each of the first 61 bits being used to represent a segment-lock. In this case, the number of "buckets" is fixed to 61 (the largest prime smaller than 64).

m_aSegment

protected final SegmentedHashMap.Segment[] m_aSegment

An array of the control-structures for the Map's segments.

m_aeBucket

protected volatile SegmentedHashMap.Entry[] m_aeBucket

The array of hash buckets. This field is declared volatile in order to reduce synchronization.

m_cSegmentCapacity

protected int m_cSegmentCapacity

The capacity of each segment (the point at which we should resize).

m_flLoadFactor

protected final float m_flLoadFactor

The determining factor for the hash map capacity given a certain number of buckets, such that capacity = bucketcount * loadfactor.

m_flGrowthRate

protected final float m_flGrowthRate

The rate of growth as a fraction of the current number of buckets, 0 < n, such that the hash map grows to bucketcount * (1 + growth-rate).

m_setEntries

protected SegmentedHashMap.EntrySet m_setEntries

The set of entries backed by this map.

m_setKeys

protected SegmentedHashMap.KeySet m_setKeys

The set of keys backed by this map.

m_colValues

protected SegmentedHashMap.ValuesCollection m_colValues

The collection of values backed by this map.

m_oIterActive

protected Object m_oIterActive

A holder for active Iterator(s): either WeakReference(<Iterator>) or WeakHashMap(<Iterator>, null)

m_actionGetEntry

protected SegmentedHashMap.GetEntryAction m_actionGetEntry

The singleton action for getEntryInternal support.

m_actionInsert

protected SegmentedHashMap.InsertAction m_actionInsert

The singleton action for insert support.

m_actionRemove

protected SegmentedHashMap.RemoveAction m_actionRemove

The singleton action for remove support.

m_actionContainsValue

protected SegmentedHashMap.ContainsValueAction m_actionContainsValue

The singleton action for containsValue support.

Constructor Detail

SegmentedHashMap

public SegmentedHashMap()

Default constructor.

SegmentedHashMap

public SegmentedHashMap(int cInitialBuckets,
                        float flLoadFactor,
                        float flGrowthRate)

Construct a thread-safe hash map using the specified settings.

Parameters:

cInitialBuckets - the initial number of hash buckets, 0 < n

flLoadFactor - the acceptable load factor before resizing occurs, 0 < n, such that a load factor of 1.0 causes resizing when the number of entries exceeds the number of buckets

flGrowthRate - the rate of bucket growth when a resize occurs, 0 < n, such that a growth rate of 1.0 will double the number of buckets: bucketcount = bucketcount * (1 + growthrate)

Method Detail

getInsertAction

protected SegmentedHashMap.InsertAction getInsertAction()

Return the registered action for insert.

Returns:

the registered action for insert

setInsertAction

protected void setInsertAction(SegmentedHashMap.InsertAction action)

Specify the action for insert.

Parameters:

action - the action for insert

getGetEntryAction

protected SegmentedHashMap.GetEntryAction getGetEntryAction()

Return the registered action for getEntryInternal.

Returns:

the registered action for getEntryInternal

setGetEntryAction

protected void setGetEntryAction(SegmentedHashMap.GetEntryAction action)

Specify the action for getEntryInternal.

Parameters:

action - the action for getEntryInternal

getRemoveAction

protected SegmentedHashMap.RemoveAction getRemoveAction()

Return the registered action for remove().

Returns:

the registered action for remove()

setRemoveAction

protected void setRemoveAction(SegmentedHashMap.RemoveAction action)

Specify the action for remove().

Parameters:

action - the action for remove()

getContainsValueAction

protected SegmentedHashMap.ContainsValueAction getContainsValueAction()

Return the registered action for containsValue().

Returns:

the registered action for containsValue()

setContainsValueAction

protected void setContainsValueAction(SegmentedHashMap.ContainsValueAction action)

Specify the action for containsValue().

Parameters:

action - the action for containsValue()

equals

public boolean equals(Object oThat)

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps t1 and t2 represent the same mappings if t1.keySet().equals(t2.keySet()) and for every key k in t1.keySet(), (t1.get(k)==null ? t2.get(k)==null : t1.get(k).equals(t2.get(k))) . This ensures that the equals method works properly across different implementations of the map interface.

Specified by:

equals in interface Map

Parameters:

oThat - object to be compared for equality with this Map

Returns:

true if the specified object is equal to this Map

hashCode

public int hashCode()

Returns the hash code value for this Map. The hash code of a Map is defined to be the sum of the hash codes of each entry in the Map's entrySet() view. This ensures that t1.equals(t2) implies that t1.hashCode()==t2.hashCode() for any two maps t1 and t2, as required by the general contract of Object.hashCode.

Specified by:

hashCode in interface Map

Returns:

the hash code value for this Map

See Also:

Map.Entry.hashCode(), Object.hashCode(), Object.equals(Object), Map.equals(Object)

toString

public String toString()

Returns a String representation of this map.

Returns:

a String representation of this map

size

public int size()

Returns the number of key-value mappings in this map. <p/> Note: Unlike some Map implementations, the size() operation on this map may be relatively expensive.

Specified by:

size in interface Map

Returns:

the number of key-value mappings in this map

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface Map

Returns:

true if this map contains no key-value mappings

containsKey

public boolean containsKey(Object oKey)

Returns true iff this map contains a mapping for the specified key.

Specified by:

containsKey in interface Map

Parameters:

oKey - key whose presence in this map is to be tested

Returns:

true iff this map contains a mapping for the specified key

containsValue

public boolean containsValue(Object oValue)

Returns true if this map maps one or more keys to the specified value.

Specified by:

containsValue in interface Map

Parameters:

oValue - value whose presence in this map is to be tested

Returns:

true if this map maps one or more keys to the specified value

get

public Object get(Object oKey)

Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key. A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Specified by:

get in interface Map

Parameters:

oKey - key whose associated value is to be returned

Returns:

the value to which this map maps the specified key, or null if the map contains no mapping for this key

See Also:

Map.containsKey(Object)

getEntry

public Map.Entry getEntry(Object key)

Locate an Entry in the this map based on its key.

Parameters:

key - the key object to search for

Returns:

the Entry or null if the entry does not exist

put

public Object put(Object oKey,
                  Object oValue)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.

Specified by:

put in interface Map

Parameters:

oKey - key with which the specified value is to be associated

oValue - value to be associated with the specified key

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key

putAll

public void putAll(Map mapOther)

Copies all of the mappings from the specified map to this map. putAll is semantically equivalent to:

 for (Iterator iter = mapOther.entrySet().iterator(); iter.hasNext(); )
     {
     Map.Entry entry = (Map.Entry) iter.next();
     put(entry.getKey(), entry.getValue());
     }
 

Specified by:

putAll in interface Map

Parameters:

mapOther - mappings to be stored in this map

remove

public Object remove(Object oKey)

Removes the mapping for this key from this map if present.

Specified by:

remove in interface Map

Parameters:

oKey - key whose mapping is to be removed from the map

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key

clear

public void clear()

Removes all mappings from this map.

Specified by:

clear in interface Map

entrySet

public Set entrySet()

Returns a set view of the mappings contained in this map. Each element in the returned set is a Map.Entry. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Specified by:

entrySet in interface Map

Returns:

a set view of the mappings contained in this map.

keySet

public Set keySet()

Returns a Set view of the keys contained in this map. The Set is backed by the map, so changes to the map are reflected in the Set, and vice-versa. (If the map is modified while an iteration over the Set is in progress, the results of the iteration are undefined.) The Set supports element removal, which removes the corresponding entry from the map, via the Iterator.remove, Set.remove, removeAll retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

keySet in interface Map

Returns:

a Set view of the keys contained in this map

values

public Collection values()

Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress, the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Specified by:

values in interface Map

Returns:

a collection view of the values contained in this map

initializeActions

protected void initializeActions()

Initialize the EntryAction's for this map.

getEntryInternal

protected SegmentedHashMap.Entry getEntryInternal(Object oKey)

Locate an Entry in the hash map based on its key.

Parameters:

oKey - the key object to search for

Returns:

the Entry or null

getEntryInternal

protected SegmentedHashMap.Entry getEntryInternal(Object oKey,
                                                  boolean fSynthetic)

Locate an Entry in the hash map based on its key.

Parameters:

oKey - the key object to search for

fSynthetic - include synthetic Entry objects representing keys that are not contained in the map

Returns:

the Entry or null

putInternal

protected Object putInternal(Object oKey,
                             Object oValue)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.

Parameters:

oKey - key with which the specified value is to be associated

oValue - value to be associated with the specified key

Returns:

previous value associated with specified key, or NO_VALUE if there was no mapping for key. A null return indicates that the map previously associated null with the specified key

removeInternal

protected Object removeInternal(Object oKey)

Removes the mapping for this key from this map if present.

Parameters:

oKey - key whose mapping is to be removed from the map

Returns:

previous value associated with specified key, or NO_VALUE if there was no mapping for key. A null return indicates that the map previously associated null with the specified key.

toArrayInternal

protected Object[] toArrayInternal(SegmentedHashMap.IterableEntryAction action,
                                   Object[] a)

Apply the specified toArray() action to the entries in the map. The toArray() action is not applied under any segment lock and is expected to accept a List instance as a context.

Parameters:

action - the toArray() action

a - the array into which the elements of the Collection are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose

Returns:

an array containing the elements returned by the specified action

Throws:

ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of the elements returned by the specified action

ensureLoadFactor

protected void ensureLoadFactor(SegmentedHashMap.Segment segment)

Check whether or not the specified segment is overloaded and if so, grow the bucket array (which suggests with high probability that the per-segment load will decrease).

Parameters:

segment - the segment to ensure the load-factor for

grow

protected void grow()

Resize the bucket array, rehashing all Entries. <p/> Note: caller of this method is expected to hold locks on all segments of the map while making this call.

grow

protected void grow(int cNew)

Resize the bucket array to the specified size, rehashing all Entries. <p/> Note: caller of this method is expected to hold locks on all segments of the map while making this call.

Parameters:

cNew - the minimum size to attempt to grow to

invokeOnAllKeys

protected Object invokeOnAllKeys(Object oContext,
                                 boolean fLock,
                                 SegmentedHashMap.IterableEntryAction actionEntry)

Perform an action on all Entries in the map. The action is provided as an EntryAction and (if the fLock is specified) it are invoked while holding the locks for all segments. <p/> The semantics of invokeOnAllKeys are equivalent to:

 for (Iterator iter = entrySet().iterator(); iter.hasNext(); )
     {
     Entry entry = (Entry) iter.next();
     actionEntry.invokeFound(...);
     }
 return oContext;
 

Except that if fLock is specified, it is performed atomically while holding all segment-locks.

Parameters:

oContext - opaque context for the specified action

fLock - true if all segment-locks should be acquired before invoking the specified action

actionEntry - the action to perform for each entry

Returns:

the specified opaque context

invokeOnKey

protected Object invokeOnKey(Object oKey,
                             Object oContext,
                             boolean fLock,
                             SegmentedHashMap.EntryAction action)

Perform an action on the specified key. The action operation is provided as an EntryAction and (if fLock is specified), is invoked while holding the appropriate segment lock for the key. <p/> The semantics of invokeOnKey are equivalent to:

 Object oResult;
 if (containsKey(oKey))
     {
     oResult = action.invokeFound(...);
     }
 else
     {
     oResult = action.invokeNotFound(...);
     }
 return oResult;
 

Except that if fLock is specified, it is performed atomically while holding the segment-lock.

Parameters:

oKey - the key to act on

oContext - opaque context for the specified action

fLock - true iff the segment should be locked before invoking the specified action

action - the action to invoke

Returns:

the result of performing the action

getBucketIndex

protected int getBucketIndex(int nHash,
                             int cBuckets)

Calculate the bucket number for a particular hash code.

Parameters:

nHash - the hash code

cBuckets - the number of buckets

Returns:

the bucket index for the specified hash code

getSegmentIndex

protected int getSegmentIndex(int nBucket)

Calculate the segment index for the the specified bucket.

Parameters:

nBucket - the bucket number

Returns:

the segment index

getSegmentForKey

protected SegmentedHashMap.Segment getSegmentForKey(Object oKey)

Return the Segment object for the specified key.

Parameters:

oKey - the key

Returns:

the Segment for the specified key

getStableBucketArray

protected SegmentedHashMap.Entry[] getStableBucketArray()

Get the bucket array, or if a resize is occurring, wait for the resize to complete and return the new bucket array.

Returns:

the latest bucket array

iteratorActivated

protected void iteratorActivated(Iterator iter)

Register the activation of an Iterator. <p/> Note: The map will not grow while there are any active iterators.

Parameters:

iter - the activated iterator

releaseIterator

public void releaseIterator(Iterator iter)

Release the (formerly-active) Iterator. <p/> Note: This method could be used to accelerate the destruction of unexhausted iterators.

Parameters:

iter - the iterator to be released

isActiveIterator

protected boolean isActiveIterator()

Determine if there are any active Iterators, which may mean that they are in the middle of iterating over the Map.

Returns:

true iff there is at least one active Iterator

lockBucket

protected boolean lockBucket(int nBucket)

Attempt to lock the segment corresponding to the specified bucket.

Parameters:

nBucket - the bucket index

Returns:

true iff the segment was successfully locked

lockSegment

protected boolean lockSegment(int nSegment,
                              boolean fBlock)

Attempt to lock the specified segment.

Parameters:

nSegment - the segment to lock

fBlock - should we block on trying to lock the segment

Returns:

true iff the segment was successfully locked

unlockBucket

protected void unlockBucket(int nBucket)

Unlock the segment corresponding to the specified bucket that was previously locked using the lockBucket(int) method.

Parameters:

nBucket - the bucket to unlock

unlockSegment

protected void unlockSegment(int nSegment)

Unlock the specified segment previously locked using the lockSegment(int, boolean) method.

Parameters:

nSegment - the segment to unlock

contendForSegment

protected void contendForSegment(int nSegment)

Wait for a segment to be unlocked.

Parameters:

nSegment - the segment-lock to be waited for

lockAllBuckets

protected void lockAllBuckets()

Lock everything. This method will not return until the lock is placed. It must not be called on a thread that could already hold a lock.

lockAllBuckets

protected boolean lockAllBuckets(int nBucketAlreadyLocked)

Lock everything, assuming that the segment for the specified bucket has already been locked.

Parameters:

nBucketAlreadyLocked - the bucket that was already locked.

Returns:

false if the operation failed because another thread was also trying to lock everything (indicating potential deadlock)

unlockAllBuckets

protected void unlockAllBuckets()

Unlock everything.

unlockAllBuckets

protected void unlockAllBuckets(int nBucketLeaveLocked)

Unlock everything, leaving only the segment for the specified bucket locked.

Parameters:

nBucketLeaveLocked - the bucket that was already locked

lockAllSegments

protected boolean lockAllSegments(long lLocksHeld)

Lock all segments except for the specified segments that have already been locked by the calling thread.

Parameters:

lLocksHeld - the bit-mask representing all segment-locks that the calling thread already holds

Returns:

false if the operation failed because another thread was also trying to lock everything (indicating potential deadlock)

unlockAllSegments

protected void unlockAllSegments(long lLocksKeep)

Unlock all segments, except the segment-locks indicated by the specified bit-vector. This method must only be called by a thread if that thread has successfully called lockAllSegments(long).

Parameters:

lLocksKeep - the segment-locks to keep locked

instantiateGetEntryAction

protected SegmentedHashMap.GetEntryAction instantiateGetEntryAction()

Factory for GetEntryAction

instantiateInsertAction

protected SegmentedHashMap.InsertAction instantiateInsertAction()

Factory for InsertAction

instantiateRemoveAction

protected SegmentedHashMap.RemoveAction instantiateRemoveAction()

Factory for RemoveAction

instantiateContainsValueAction

protected SegmentedHashMap.ContainsValueAction instantiateContainsValueAction()

Factory for ContainsValueAction

instantiateEntry

protected SegmentedHashMap.Entry instantiateEntry(Object oKey,
                                                  Object oValue,
                                                  int nHash)

Factory for Entry.

Returns:

a new instance of the Entry class (or a subclass thereof)

entryFromBucket

protected static SegmentedHashMap.Entry entryFromBucket(SegmentedHashMap.Entry[] aeBucket,
                                                        int nBucket)

Return the first non-synthetic Entry object contained by in the specified bucket.

Parameters:

aeBucket - the array of hash buckets

nBucket - the bucket index

Returns:

the first non-synthetic Entry in the specified bucket or null

instantiateEntrySet

protected SegmentedHashMap.EntrySet instantiateEntrySet()

Factory for EntrySet

Returns:

a new instance of the EntrySet class (or a subclass thereof)

instantiateKeySet

protected SegmentedHashMap.KeySet instantiateKeySet()

Factory for KeySet.

Returns:

a new instance of the KeySet class (or subclass thereof)

instantiateValuesCollection

protected SegmentedHashMap.ValuesCollection instantiateValuesCollection()

Factory for ValuesCollection.

Returns:

a new instance of the ValuesCollection class (or subclass thereof)

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