com.icesoft.pdf.util
Class MemoryManager

java.lang.Object
  com.icesoft.pdf.util.MemoryManager

public class MemoryManager

extends Object

The MemoryManager class is a utility to help manage the amount of memory available to the application. When memory intensive operations are about occur, the MemoryManager is asked if it can allocate the needed amount of memory. If there is not enough memory available, the MemoryManager will purge the cache to try and free the requested amount of memory.

Field Summary

protected long	cumulativeDurationManagingMemory
protected long	cumulativeDurationNotManagingMemory
protected ArrayList	delegates
protected ArrayList	leastRecentlyUsed
protected WeakHashMap	locked
protected long	maxMemory The maximum amount of memory allocated to the JVM.
protected int	maxSize If a memory-based ceiling, like maxMemory, is not sufficient, then you can use maxSize to specify the maximum number of items that may be opened before purging commences.
protected long	minMemory The minimum amount of free memory at which the memory manager will force a purge of the cached pageTree.
protected int	percentageDurationManagingMemory
protected long	previousTimestampManagedMemory
protected int	purgeSize When we decide to reduce our memory footprint, this is how many items we purge at once.
protected Runtime	runtime Runtime object responsible for returning VM memory use information

Constructor Summary

protected

MemoryManager() Creates a new instance of a MemoryManager.

Method Summary

boolean	checkMemory(int memoryNeeded)
long	getFreeMemory() Get runtime free memory.
static MemoryManager	getInstance() Get an instance of the MemoryManager.
long	getMaxMemory() Get maximum amount of jvm heap.
long	getMinMemory() Get the minimum amount of memory
protected boolean	isLocked(MemoryManageable mm)
boolean	isLowMemory() Check whether the runtime is low on memory.
void	lock(Object user, MemoryManageable mm)
protected boolean	reduceMemory()
protected int	reduceMemory(int numToDo)
protected boolean	reduceMemoryWithDelegates(boolean aggressively)
void	registerMemoryManagerDelegate(MemoryManagerDelegate delegate)
void	release(Object user, MemoryManageable mm)
void	releaseAllByLibrary(Library library)
static void	setInstance(MemoryManager memoryMangaer) Sets an existing MemoryManager object to this MemoryManager object.
void	setMaxMemory(long m) Set the maximum amount of JVM heap.
void	setMinMemory(long m) Set the minimum amount of memory.

Methods inherited from class java.lang.Object

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

Field Detail

runtime

protected final Runtime runtime

Runtime object responsible for returning VM memory use information

minMemory

protected long minMemory

The minimum amount of free memory at which the memory manager will force a purge of the cached pageTree. This value can be set by the system property com.icesoft.pdf.minMemory

maxMemory

protected long maxMemory

The maximum amount of memory allocated to the JVM. There is a new method in JDK 1.4 getMaxMemory which will return this value automatically, but is not available in JDK 1.3. This value should be set to the same value of the system property -Xmx. The default value of 63MB can be set using the system property com.icesoft.pdf.maxMemory

purgeSize

protected int purgeSize

When we decide to reduce our memory footprint, this is how many items we purge at once.

maxSize

protected int maxSize

If a memory-based ceiling, like maxMemory, is not sufficient, then you can use maxSize to specify the maximum number of items that may be opened before purging commences. A value of 0 (zero) means it will not be used

locked

protected WeakHashMap locked

leastRecentlyUsed

protected ArrayList leastRecentlyUsed

cumulativeDurationManagingMemory

protected long cumulativeDurationManagingMemory

cumulativeDurationNotManagingMemory

protected long cumulativeDurationNotManagingMemory

previousTimestampManagedMemory

protected long previousTimestampManagedMemory

percentageDurationManagingMemory

protected int percentageDurationManagingMemory

delegates

protected ArrayList delegates

Constructor Detail

MemoryManager

protected MemoryManager()

Creates a new instance of a MemoryManager.

Method Detail

setInstance

public static void setInstance(MemoryManager memoryMangaer)

Sets an existing MemoryManager object to this MemoryManager object.

Parameters:

memoryMangaer - MemoryManager object to point to.

getInstance

public static MemoryManager getInstance()

Get an instance of the MemoryManager. If there is not a MemoryManager initiated, a new MemoryManager is is created and returned.

Returns:

the current MemoryManager object com.icesoft.pdf.minMemory

lock

public void lock(Object user,
                 MemoryManageable mm)

release

public void release(Object user,
                    MemoryManageable mm)

registerMemoryManagerDelegate

public void registerMemoryManagerDelegate(MemoryManagerDelegate delegate)

releaseAllByLibrary

public void releaseAllByLibrary(Library library)

reduceMemory

protected boolean reduceMemory()

Returns:

If potentially reduced some memory

reduceMemory

protected int reduceMemory(int numToDo)

isLocked

protected boolean isLocked(MemoryManageable mm)

reduceMemoryWithDelegates

protected boolean reduceMemoryWithDelegates(boolean aggressively)

setMinMemory

public void setMinMemory(long m)

Set the minimum amount of memory. Basically, if the amount of free heap is under this value, the browser will go into the error recovery mode.

getMinMemory

public long getMinMemory()

Get the minimum amount of memory

setMaxMemory

public void setMaxMemory(long m)

Set the maximum amount of JVM heap. This should be the same value as you give to jvm (normally with -mx parameter). The MemoryManager will use this number to determine whether it is low on memory. The manager also uses Runtime.freeMemory() call but that call returns the free memory with only the current heap size, not the maximum heap size.

getMaxMemory

public long getMaxMemory()

Get maximum amount of jvm heap.

getFreeMemory

public long getFreeMemory()

Get runtime free memory.

Returns:

free memory in bytes.

isLowMemory

public boolean isLowMemory()

Check whether the runtime is low on memory. All well behaved browser components (pilots and scripters) should call this method before (during) attempts to allocate resources. If this method returns true, such a component should stop its operation and free up the memory it has allocated.

checkMemory

public boolean checkMemory(int memoryNeeded)

Parameters:

memoryNeeded -

Returns:

true if it's sure we can allocate memoryNeeded number of bytes