javax.realtime
Class MemoryArea

java.lang.Object
  javax.realtime.MemoryArea

Direct Known Subclasses:

HeapMemory, ImmortalMemory, ImmortalPhysicalMemory, ScopedMemory

public abstract class MemoryArea
extends Object

Jamaica Real-Time Specification for Java class MemoryArea.

MemoryArea provides the abstract base class for all allocation environments.

In JamaicaVM, application code is not permitted to create instances of user-defined direct subclasses of MemoryArea.

Field Summary

protected static Object

memoryAreaHeapLock Lock to protect alloc() and free() from concurrent execution.

Constructor Summary

protected	MemoryArea(long sizeInBytes) Constructor for a memory area of given size.
protected	MemoryArea(long sizeInBytes, Runnable logic) Constructor for a memory area that of given size in bytes and sets a logic.
protected	MemoryArea(SizeEstimator size) Constructor for a memory area that gets its size from a SizeEstimator.
protected	MemoryArea(SizeEstimator size, Runnable logic) Constructor for a memory area that of given size from a SizeEstimator and sets a logic.

Method Summary

protected void	clearMemory()
protected void	createStackedMemory() Create a new child StackedMemory for this memory area.
void	enter() enter enters this memory area and executes the logic that was passed to this memory area's constructor.
void	enter(Runnable logic) enter enters this memory area and executes the given logic.
void	executeInArea(Runnable logic) executeInArea executes a code sequence given as logic in this memory area.
protected void	freeStacked() frees a StackedMemory child previously created with createStackedMemory()
static MemoryArea	getMemoryArea(Object object) getMemoryArea returns the memory area a given object was allocated in.
long	memoryConsumed() memoryConsumed returns the number of bytes of memory of this memory area that have been consumed.
protected boolean	memoryNeedsToBeCleared()
protected boolean	memoryNeedsToBeFreed()
long	memoryRemaining() memoryRemaining returns the number of available bytes left in this memory area.
Object	newArray(Class<?> type, int number) Allocate a new array with number elements in this memory area.
Object	newInstance(Class<?> type) allocate a new instance of class type in this memory area.
Object	newInstance(Constructor<?> c, Object[] args) newInstance allocates a new instance using the given constructor and passing arguments to this constructor.
long	size() size returns the size of this memory area in bytes.

Methods inherited from class java.lang.Object

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

Field Detail

memoryAreaHeapLock

protected static Object memoryAreaHeapLock

Lock to protect alloc() and free() from concurrent execution.

Constructor Detail

MemoryArea

protected MemoryArea(long sizeInBytes)

Constructor for a memory area of given size.

Parameters:

sizeInBytes - size of the area in bytes.

Throws:

IllegalArgumentException - if sizeInBytes < 0 or this is called by a user-defined subclass that does not know about the memory area implementation details.

OutOfMemoryError - if there is not sufficient memory available for the new MemoryArea.

MemoryArea

protected MemoryArea(SizeEstimator size)

Constructor for a memory area that gets its size from a SizeEstimator.

Parameters:

size - the requested size.

Throws:

IllegalArgumentException - if size is null or this is called by a user-defined subclass that does not know about the memory area implementation details.

OutOfMemoryError - if there is not sufficient memory available for the new MemoryArea.

MemoryArea

protected MemoryArea(long sizeInBytes,
                     Runnable logic)

Constructor for a memory area that of given size in bytes and sets a logic.

Parameters:

sizeInBytes - size of the area in bytes.

logic - the logic to be associated with this memory area. May be null not to set a default logic.

Throws:

IllegalArgumentException - if sizeInBytes < 0 or this is called by a user-defined subclass that does not know about the memory area implementation details.

OutOfMemoryError - if there is not sufficient memory available for the new MemoryArea.

MemoryArea

protected MemoryArea(SizeEstimator size,
                     Runnable logic)

Constructor for a memory area that of given size from a SizeEstimator and sets a logic.

Parameters:

size - size of the area.

logic - the logic to be associated with this memory area.

Throws:

IllegalArgumentException - if size is null or this is called by a user-defined subclass that does not know about the memory area implementation details.

OutOfMemoryError - if there is not sufficient memory available for the new MemoryArea.

Method Detail

createStackedMemory

protected void createStackedMemory()

Create a new child StackedMemory for this memory area. This is only used to create guest & host children, not for creating root stacked memory!

freeStacked

protected void freeStacked()

frees a StackedMemory child previously created with createStackedMemory()

memoryNeedsToBeFreed

protected boolean memoryNeedsToBeFreed()

memoryNeedsToBeCleared

protected boolean memoryNeedsToBeCleared()

clearMemory

protected void clearMemory()

enter

public void enter()

enter enters this memory area and executes the logic that was passed to this memory area's constructor.

Throws:

IllegalArgumentException - if no logic was provided to the constructor or the logic that was provided was null.

enter

public void enter(Runnable logic)

enter enters this memory area and executes the given logic.

Parameters:

logic - the code to be executed in this memory area.

Throws:

IllegalArgumentException - if logic is null.

getMemoryArea

public static MemoryArea getMemoryArea(Object object)

getMemoryArea returns the memory area a given object was allocated in.

Parameters:

object - the object, must not be null.

Returns:

the memory area object was allocated in HeapMemory.instance() for all objects that were allocated on the normal heap.

memoryConsumed

public long memoryConsumed()

memoryConsumed returns the number of bytes of memory of this memory area that have been consumed. For memory areas that are freed explicitly by the user (e.g., by exiting a scoped memory area), the result is exact. For other memory areas (that may be under the control of the garbage collector), the result may be an estimation. In JamaicaVM, the memoryConsumed() for HeapMemory is amount of allocated (i.e., non-free) memory. It is an upper bound for the amount of reachable memory.

Returns:

number of bytes consumed from this memory area.

memoryRemaining

public long memoryRemaining()

memoryRemaining returns the number of available bytes left in this memory area. This may be an estimation of the amount of available memory. In JamaicaVM, memoryRemaining for HeapMemory is the total heap memory minus memoryConsumed().

Returns:

the number of free bytes in this memory area.

newArray

public Object newArray(Class<?> type,
                       int number)
                throws IllegalArgumentException,
                       OutOfMemoryError,
                       InaccessibleAreaException

Allocate a new array with number elements in this memory area. This method is save to be used concurrently by several threads, it synchronizes on this.

Parameters:

type - the array type

number - the number of elements of the array.

Returns:

the new array object allocated from this memory area.

Throws:

IllegalArgumentException - iff number is negative, type is null or type is Void.TYPE.

throws - OutOfMemoryError iff the space in this memory area is exhausted

InaccessibleAreaException - iff this memory area is not accessible, i.e. not on the current memory area stack.

OutOfMemoryError

newInstance

public Object newInstance(Class<?> type)
                   throws IllegalAccessException,
                          InstantiationException

allocate a new instance of class type in this memory area. Call the constructor with empty argument list. This method is save to be used concurrently by several threads, it synchronizes on this.

Parameters:

type - the type of the new object that is to be allocated.

Returns:

the new instance allocated from this memory area.

Throws:

IllegalAccessException - thrown if class or constructor is inaccessible.

IllegalArgumentException - iff type is null.

InstantiationException - if object could not be instantiated (due to type being abstract or an interface or the constructor caused an exception)

OutOfMemoryError - iff the space in this memory area is exhausted

ExceptionInInitializerError - iff initialization of class type caused an exception.

InaccessibleAreaException - iff this memory area is not accessible, i.e. not on the memory area stack.

newInstance

public Object newInstance(Constructor<?> c,
                          Object[] args)
                   throws IllegalAccessException,
                          InstantiationException,
                          InvocationTargetException

newInstance allocates a new instance using the given constructor and passing arguments to this constructor.

Parameters:

c - the constructor of the new instance

args - the arguments to be passed to the constructor

Returns:

the new instance allocated from this memory area.

Throws:

IllegalAccessException - thrown if type is inaccessible

IllegalArgumentException - iff c is null or args does not contain the number of arguments required by c (args may be null if the arguments list is empty).

InstantiationException - if object could not be instantiated (due to type being abstract or an interface or the constructor caused an exception)

OutOfMemoryError - iff the space in this memory area is exhausted

ExceptionInInitializerError - iff initialization of class type caused an exception.

InaccessibleAreaException - iff this memory area is not accessible, i.e. not on the memory area stack.

InvocationTargetException

size

public long size()

size returns the size of this memory area in bytes.

Returns:

the size in bytes.

executeInArea

public void executeInArea(Runnable logic)
                   throws InaccessibleAreaException

executeInArea executes a code sequence given as logic in this memory area.

Parameters:

logic - the logic whose run method is to be executed in this memory area.

Throws:

InaccessibleAreaException