Package gov.nasa.worldwind.cache

Class BasicRasterServerCache

java.lang.Object

gov.nasa.worldwind.cache.BasicMemoryCache

gov.nasa.worldwind.cache.BasicRasterServerCache

All Implemented Interfaces:

MemoryCache

public class BasicRasterServerCache
extends BasicMemoryCache

The BasicRasterServerCache is an implementation of the memory cache that is specific to store maximum possible cacheable items, until the heap size allows. Once the memory limit is hit, it will drop ALL cached items. Also, BasicRasterServerCache creates a pruner thread that removes all cached items which were not used for 20 seconds or more. The least recent use timeout is configurable via the setLeastRecentUseTimeout() method. In addition, the BasicRasterServerCache allocates 100MB memory and keeps only a phantom reference to the allocated 100M memory. Once any part of the application needs more memory the phantom referenced memory will be immediately released and the phantom reference will be added to the internal reference queue, which is monitored by an internal MemoryMonitorThread. Once the phantom reference is added to the reference queue, the entire cached content will be released. This approach allows to use almost entire available heap memory to cache rasters and release memory when more memory is needed to the application itself.

Nested Class Summary

Nested classes/interfaces inherited from class gov.nasa.worldwind.cache.BasicMemoryCache

BasicMemoryCache.CacheEntry

Nested classes/interfaces inherited from interface gov.nasa.worldwind.cache.MemoryCache

MemoryCache.CacheListener

Field Summary

Fields

Modifier and Type	Field	Description
protected static int	DEFAULT_INACCESSIBLE_MEMORY_SIZE
protected static long	DEFAULT_LEAST_RECENTLY_USED_TIMEOUT_NSEC
protected static long	DEFAULT_PRUNER_THREAD_TIMEOUT_MSEC
protected java.util.concurrent.atomic.AtomicInteger	inaccessibleMemorySize
protected java.lang.ref.Reference<java.lang.Object>	lowMemorySemaphore
protected java.lang.ref.ReferenceQueue<java.lang.Object>	queue
protected long	timeoutLeastRecentUseInNanoSeconds

Fields inherited from class gov.nasa.worldwind.cache.BasicMemoryCache

capacity, currentUsedCapacity, entries, listeners, lock, lowWater, name

Constructor Summary

Constructors

Constructor	Description
BasicRasterServerCache()	Constructs a new cache which uses entire memory, but will immediately drop all cached entries ones there is a need for more memory by anyone else.
BasicRasterServerCache(int inaccessibleMemorySize)

Method Summary

Modifier and Type	Method	Description
boolean	add(java.lang.Object key, java.lang.Object clientObject, long clientObjectSize)	Adds an object to the cache.
long	getLeastRecentUseTimeout()
protected void	removeExpiredEntries()
void	setLeastRecentUseTimeout(long nanoSeconds)
protected void	updateMemorySemaphore()

Methods inherited from class gov.nasa.worldwind.cache.BasicMemoryCache

add, addCacheListener, clear, contains, getCapacity, getFreeCapacity, getLowWater, getName, getNumObjects, getObject, getUsedCapacity, remove, removeCacheListener, removeEntry, setCapacity, setLowWater, setName, toString

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_INACCESSIBLE_MEMORY_SIZE

protected static final int DEFAULT_INACCESSIBLE_MEMORY_SIZE

See Also:

Constant Field Values

DEFAULT_PRUNER_THREAD_TIMEOUT_MSEC

protected static final long DEFAULT_PRUNER_THREAD_TIMEOUT_MSEC

See Also:

Constant Field Values

DEFAULT_LEAST_RECENTLY_USED_TIMEOUT_NSEC

protected static final long DEFAULT_LEAST_RECENTLY_USED_TIMEOUT_NSEC

See Also:

Constant Field Values

inaccessibleMemorySize

protected java.util.concurrent.atomic.AtomicInteger inaccessibleMemorySize

queue

protected final java.lang.ref.ReferenceQueue<java.lang.Object> queue

lowMemorySemaphore

protected java.lang.ref.Reference<java.lang.Object> lowMemorySemaphore

timeoutLeastRecentUseInNanoSeconds

protected long timeoutLeastRecentUseInNanoSeconds

Constructor Detail

BasicRasterServerCache

public BasicRasterServerCache()

Constructs a new cache which uses entire memory, but will immediately drop all cached entries ones there is a need for more memory by anyone else.

BasicRasterServerCache

public BasicRasterServerCache(int inaccessibleMemorySize)

Method Detail

add

public boolean add(java.lang.Object key,
                   java.lang.Object clientObject,
                   long clientObjectSize)

Description copied from class: BasicMemoryCache

Adds an object to the cache. The add fails if the object or key is null, or if the size is zero, negative or greater than the maximmum capacity.

Specified by:

add in interface MemoryCache

Overrides:

add in class BasicMemoryCache

Parameters:

key - The unique reference key that identifies this object.

clientObject - The actual object to be cached.

clientObjectSize - The size of the object in cache units.

Returns:

returns true if clientObject was added, false otherwise.

updateMemorySemaphore

protected void updateMemorySemaphore()

getLeastRecentUseTimeout

public long getLeastRecentUseTimeout()

setLeastRecentUseTimeout

public void setLeastRecentUseTimeout(long nanoSeconds)

removeExpiredEntries

protected void removeExpiredEntries()