javax.realtime
Class MemoryArea

java.lang.Object
  javax.realtime.MemoryArea

Direct Known Subclasses:

Arena, HeapMemory, ImmortalMemory, ImmortalPhysicalMemory, MethodAreaMemory, ScopedMemory

public abstract class MemoryArea

extends Object

MemoryArea is the abstract base class of all classes dealing with the representations of allocatable memory areas, including the immortal memory area, physical memory and scoped memory areas.

Author:

Angelo Corsaro, Morgan Deters

Field Summary

protected Runnable	logic
protected MemoryArea	parent
protected long	sizeInBytes

Constructor Summary

protected	MemoryArea()
protected	MemoryArea(long size) Creates a new MemoryArea instance.
protected	MemoryArea(long size, Runnable logic) Creates a new MemoryArea instance.
protected	MemoryArea(SizeEstimator size) Creates a new MemoryArea instance.
protected	MemoryArea(SizeEstimator size, Runnable logic) Creates a new MemoryArea instance.

Method Summary

void	enter() Associate this memory area to the current real-time thread for the duration of the execution of the run() method of the Runnable passed at construction time.
void	enter(Runnable logic) Associate this memory area to the current real-time thread for the duration of the execution of the run() method of the given Runnable.
void	executeInArea(Runnable logic) Execute the run method from the logic parameter using this memory area as the current allocation context.
protected void	finalize()
static MemoryArea	getMemoryArea(Object object) Returns the MemoryArea in which the given object is located.
protected void	guardedRun(Runnable logic) Run the given logic and, if it exits exceptionally, check to ensure that the thrown exception is valid in the parent scope.
long	memoryConsumed() An exact count, in bytes, of the all of the memory currently used by the system for the allocated objects.
long	memoryRemaining() An approximation to the total amount of memory currently available for future allocated objects, measured in bytes.
Object	newArray(Class type, int number) Allocate an array of T in this memory area.
Object	newInstance(Class type) Allocate an object in this memory area.
Object	newInstance(Constructor ctor, Object[] args) Allocates an object in this memory area.
long	size() Query the size of the memory area.

Methods inherited from class java.lang.Object

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

Field Detail

sizeInBytes

protected long sizeInBytes

logic

protected Runnable logic

parent

protected MemoryArea parent

Constructor Detail

MemoryArea

protected MemoryArea()

MemoryArea

protected MemoryArea(long size)

Creates a new MemoryArea instance.

Parameters:

size - the size of MemoryArea to allocate, in bytes.

Throws:

IllegalArgumentException - if size is less than zero

OutOfMemoryError - if there isn't enough storage available for the backing memory

MemoryArea

protected MemoryArea(long size,
                     Runnable logic)

Creates a new MemoryArea instance.

Parameters:

size - the size of MemoryArea to allocate, in bytes.

logic - The run() method of this object will be called whenever enter() is called.

Throws:

IllegalArgumentException - if size is less than zero

IllegalAssignmentError - if storing logic in this violates referencing rules

OutOfMemoryError - if there isn't enough storage available for the backing memory

MemoryArea

protected MemoryArea(SizeEstimator size)

Creates a new MemoryArea instance.

Parameters:

size - A SizeEstimator object which indicates the amount of memory required by this MemoryArea.

Throws:

IllegalArgumentException - if size is null

OutOfMemoryError - if there isn't enough storage available for the backing memory

MemoryArea

protected MemoryArea(SizeEstimator size,
                     Runnable logic)

Creates a new MemoryArea instance.

Parameters:

size - A SizeEstimator object which indicates the amount of memory required by this MemoryArea.

logic - -The run() method of this object will be called whenever enter() is called.

Throws:

IllegalArgumentException - if size is null

IllegalAssignmentError - if storing logic in this violates referencing rules

OutOfMemoryError - if there isn't enough storage available for the backing memory

Method Detail

enter

public void enter()

Associate this memory area to the current real-time thread for the duration of the execution of the run() method of the Runnable passed at construction time. During this bound period of execution, all objects are allocated from the memory area until another one takes effect, or this enter() method is exited. A runtime exception is thrown if this method is called from thread other than a RealtimeThread or NoHeapRealtimeThread.

Throws:

ScopedCycleException - If entering this ScopedMemory would violate the single parent rule.

enter

public void enter(Runnable logic)

Associate this memory area to the current real-time thread for the duration of the execution of the run() method of the given Runnable. During this bound period of execution, all objects are allocated from the memory area until another one takes effect, or this enter() method is exited. A runtime exception is thrown if this method is called from thread other than a RealtimeThread or NoHeapRealtimeThread.

Parameters:

logic - The Runnable object whose run() method should be invoked.

Throws:

ScopedCycleException - If entering this ScopedMemory would violate the single parent rule.

guardedRun

protected final void guardedRun(Runnable logic)

Run the given logic and, if it exits exceptionally, check to ensure that the thrown exception is valid in the parent scope. If so, rethrow; otherwise, throw a ThrowBoundaryError instead.

Parameters:

logic - The Runnable object whose run() method should be invoked and checked for exceptional exit.

executeInArea

public void executeInArea(Runnable logic)
                   throws InaccessibleAreaException

Execute the run method from the logic parameter using this memory area as the current allocation context. If the memory area is a scoped memory type, this method behaves as if it had moved the allocation context up the scope stack to the occurrence of the memory area. If the memory area is heap or immortal memory, this method behaves as if the run method were running in that memory type with an empty scope stack.

Parameters:

logic - The runnable object whose run() method should be executed.

Throws:

InaccessibleAreaException - The memory area is not in the thread s scope stack.

getMemoryArea

public static MemoryArea getMemoryArea(Object object)

Returns the MemoryArea in which the given object is located.

Parameters:

object - the object for which the associated memory area will be provided.

Returns:

The MemoryArea of the object.

memoryConsumed

public long memoryConsumed()

An exact count, in bytes, of the all of the memory currently used by the system for the allocated objects.

Returns:

The amount of memory consumed in bytes.

memoryRemaining

public long memoryRemaining()

An approximation to the total amount of memory currently available for future allocated objects, measured in bytes.

Returns:

The amount of remaining memory in bytes.

newArray

public Object newArray(Class type,
                       int number)

Allocate an array of T in this memory area.

Parameters:

type - The class of the elements of the new array.

number - The number of elements in the new array.

Returns:

A new array of class type, of number elements.

Throws:

IllegalAccessException - The class or initializer is inaccessible.

InstantiationException - The array cannot be instantiated.

newInstance

public Object newInstance(Class type)
                   throws InstantiationException,
                          IllegalAccessException

Allocate an object in this memory area.

Parameters:

type - The class of which to create a new instance.

Returns:

A new instance of class type.

Throws:

IllegalAccessException - The class or initializer is inaccessible.

InstantiationException - The specified class object could not be instantiated. Possible causes are: it is an interface, it is abstract, it is an array, or an exception was thrown by the constructor.

newInstance

public Object newInstance(Constructor ctor,
                          Object[] args)
                   throws IllegalAccessException,
                          InstantiationException

Allocates an object in this memory area.

Parameters:

ctor - the constructor used to create the new instance.

args - the argument to be passed to the constructor.

Returns:

the object allocated

Throws:

IllegalAccessException - The class or initializer is inaccessible.

InstantiationException - The specified class object could not be instantiated. Possible causes are: it is an interface, it is abstract, it is an array, or an exception was thrown by the constructor.

size

public long size()

Query the size of the memory area. The returned value is the current size. Current size may be larger than initial size for those areas that are allowed to grow.

Returns:

the size of the memory area in bytes.

finalize

protected void finalize()