Module openj9.dtfj

Package com.ibm.dtfj.phd

Class PHDJavaObject

java.lang.Object

com.ibm.dtfj.phd.PHDJavaObject

All Implemented Interfaces:

JavaObject

public class PHDJavaObject
extends Object
implements JavaObject

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	PHDJavaObject.Builder	The constructors for PHDJavaObject used to take up to 11 arguments, many of which were ints.

Field Summary

Fields

Modifier and Type	Field	Description
static final long	UNSPECIFIED_INSTANCE_SIZE	instance size is an unsigned int in the datastream, so -1L is a value that cannot collide

Constructor Summary

Constructors

Constructor	Description
PHDJavaObject(PHDJavaObject.Builder builder)

Method Summary

Modifier and Type	Method	Description
void	arraycopy(int srcStart, Object dst, int dstStart, int length)	Copies data from the image array into a local Java array.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
int	getArraySize()	Get the number of elements in this array.
long	getHashcode()	Fetch the basic hash code for the object.
JavaHeap	getHeap()	Gets the heap where this object is located.
ImagePointer	getID()	The ID of an object is a unique address is memory which identifies the object.
JavaClass	getJavaClass()	Get the JavaClass instance which represents the class of this object.
long	getPersistentHashcode()	Fetch the basic hash code of the object in the image.
Iterator<JavaReference>	getReferences()	Get the set of references from this object.
Iterator<ImageSection>	getSections()	An object is represented in the Java runtime by one or more regions of memory.
long	getSize()	Get the number of bytes of memory occupied by this object on the heap.
int	hashCode()	Answers an integer hash code for the receiver.
boolean	isArray()	Is this object an array?

Methods declared in class java.lang.Object

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

Field Details

UNSPECIFIED_INSTANCE_SIZE

public static final long UNSPECIFIED_INSTANCE_SIZE

instance size is an unsigned int in the datastream, so -1L is a value that cannot collide

See Also:

• Constant Field Values

Constructor Details

PHDJavaObject

public PHDJavaObject(PHDJavaObject.Builder builder)

Method Details

arraycopy

public void arraycopy(int srcStart,
 Object dst,
 int dstStart,
 int length)
               throws CorruptDataException,
MemoryAccessException

Description copied from interface: JavaObject

Copies data from the image array into a local Java array. The dst object must be an array of the appropriate type -- a base type array for base types, or a JavaObject array for reference arrays.

Specified by:

arraycopy in interface JavaObject

Parameters:

srcStart - index in the receiver to start copying from

dst - the destination array

dstStart - index in the destination array to start copying into

length - the number of elements to be copied

Throws:

CorruptDataException

MemoryAccessException

getArraySize

public int getArraySize()
                 throws CorruptDataException

Description copied from interface: JavaObject

Get the number of elements in this array.

Specified by:

getArraySize in interface JavaObject

Returns:

the number of elements in this array

Throws:

CorruptDataException

getHashcode

public long getHashcode()
                 throws DataUnavailable,
CorruptDataException

Description copied from interface: JavaObject

Fetch the basic hash code for the object. This is the hash code which would be returned if a Java thread had requested it. Typically the hash code is based on the address of an object, and may change if the object is moved by a garbage collection cycle.

Specified by:

getHashcode in interface JavaObject

Returns:

the basic hash code of the object in the image

Throws:

DataUnavailable - if the hash code cannot be determined

CorruptDataException

See Also:

• JavaObject.getPersistentHashcode()

getHeap

public JavaHeap getHeap()
                 throws CorruptDataException,
DataUnavailable

Description copied from interface: JavaObject

Gets the heap where this object is located.

Specified by:

getHeap in interface JavaObject

Returns:

the JavaHeap instance representing the heap where this object is stored in memory

Throws:

CorruptDataException - if the heap information for this object is corrupt

DataUnavailable - if the heap information for this object is not available

See Also:

• JavaHeap

getID

public ImagePointer getID()

Description copied from interface: JavaObject

The ID of an object is a unique address is memory which identifies the object. The data at this memory is implementation defined. The object may be non-contiguous. Portions of the object may appear below or above this address.

Specified by:

getID in interface JavaObject

Returns:

the runtime-wide unique identifier for the object

getJavaClass

public JavaClass getJavaClass()
                       throws CorruptDataException

Description copied from interface: JavaObject

Get the JavaClass instance which represents the class of this object.

Specified by:

getJavaClass in interface JavaObject

Returns:

the JavaClass instance which represents the class of this object

Throws:

CorruptDataException

getPersistentHashcode

public long getPersistentHashcode()
                           throws DataUnavailable,
CorruptDataException

Description copied from interface: JavaObject

Fetch the basic hash code of the object in the image. This hash code is guaranteed to be persistent between multiple snapshots of the same Image. If the hash code cannot be determined, or if the hash code for this object could change between snapshots, an exception is thrown.

If the VM uses a 'hasBeenHashed' bit, the value of this bit can be inferred by calling getPersistentHashcode(). If the persistent hash code is not available, then the 'hasBeenHashed' bit has not been set, and the hash of the object could change if the object moves between snapshots

Specified by:

getPersistentHashcode in interface JavaObject

Returns:

the basic hash code of the object in the image

Throws:

DataUnavailable - if a hash code cannot be determined, or if the hash code could change between successive snapshots

CorruptDataException

See Also:

• JavaObject.getHashcode()

getReferences

public Iterator<JavaReference> getReferences()

Description copied from interface: JavaObject

Get the set of references from this object. Corrupt references will be returned as CorruptData objects by the Iterator.

Specified by:

getReferences in interface JavaObject

Returns:

an iterator of JavaReference and CorruptData objects

See Also:

• JavaReference
• CorruptData

getSections

public Iterator<ImageSection> getSections()

Description copied from interface: JavaObject

An object is represented in the Java runtime by one or more regions of memory. These include the object's header and the data in the object. In certain allocation strategies, an object's header and data may be allocated contiguously. In this case, this method may return an iterator for a single section. In other schemes, the header may be separate from the data or the data may be broken up into multiple regions. Additionally, this function does not guarantee that the memory used by this object is not also shared by one or more other objects. Callers should not make any assumptions about the contents of the memory.

Specified by:

getSections in interface JavaObject

Returns:

a collection of sections that make up this object

See Also:

• ImageSection
• CorruptData

getSize

public long getSize()
             throws CorruptDataException

Description copied from interface: JavaObject

Get the number of bytes of memory occupied by this object on the heap. The memory may not necessarily be contiguous.

Specified by:

getSize in interface JavaObject

Throws:

CorruptDataException

isArray

public boolean isArray()
                throws CorruptDataException

Description copied from interface: JavaObject

Is this object an array?

Specified by:

isArray in interface JavaObject

Returns:

true if the receiver represents an instance of an array, or false otherwise

Throws:

CorruptDataException

equals

public boolean equals(Object o)

Description copied from interface: JavaObject

Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison. The implementation in Object answers true only if the argument is the exact same object as the receiver (==).

Specified by:

equals in interface JavaObject

Overrides:

equals in class Object

Parameters:

o - Object the object to compare with this object.

Returns:

boolean true if the object is the same as this object false if it is different from this object.

See Also:

• Object.hashCode()

hashCode

public int hashCode()

Description copied from interface: JavaObject

Answers an integer hash code for the receiver. Any two objects which answer true when passed to .equals must answer the same value for this method.

Specified by:

hashCode in interface JavaObject

Overrides:

hashCode in class Object

Returns:

the receiver's hash.

See Also:

• Object.equals(java.lang.Object)