org.jikesrvm.objectmodel

Class FieldLayout

java.lang.Object

org.jikesrvm.objectmodel.FieldLayout

Direct Known Subclasses:

FieldLayoutPacked, FieldLayoutUnpacked

public abstract class FieldLayout
extends Object

This abstract class defines the interface for schemes that layout fields in an object. Not header fields, (scalar) object fields.

The field layout object encapsulates layout state.

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	clusterReferenceFields Lay out reference fields in a block
protected static boolean	DEBUG Enable debugging
private boolean	largeFieldsFirst Whether to lay out 8byte values first in order to avoid some holes

Constructor Summary

Constructors

Constructor and Description
FieldLayout(boolean largeFieldsFirst, boolean clusterReferenceFields)

Method Summary

Modifier and Type	Method and Description
protected abstract FieldLayoutContext	getLayoutContext(RVMClass klass) Return the appropriate layout context object for the given class.
protected void	layoutField(FieldLayoutContext layout, RVMClass klass, RVMField field, int fieldSize) Lay out a given field.
void	layoutInstanceFields(RVMClass klass) This is where a class gets laid out.
protected static int	log2(int x)
protected void	setOffset(RVMClass klass, RVMField field, int offset) Update a field to set its offset within the object.
protected void	updateClass(RVMClass klass, FieldLayoutContext fieldLayout) Updates the RVMClass with context info.

Methods inherited from class java.lang.Object

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

Field Detail

DEBUG

protected static final boolean DEBUG

Enable debugging

See Also:

Constant Field Values

largeFieldsFirst

private final boolean largeFieldsFirst

Whether to lay out 8byte values first in order to avoid some holes

clusterReferenceFields

private final boolean clusterReferenceFields

Lay out reference fields in a block

Constructor Detail

FieldLayout

public FieldLayout(boolean largeFieldsFirst,
                   boolean clusterReferenceFields)

Method Detail

log2

protected static int log2(int x)

Parameters:

x - the integer

Returns:

log base 2 of an integer

getLayoutContext

protected abstract FieldLayoutContext getLayoutContext(RVMClass klass)

Return the appropriate layout context object for the given class.

Parameters:

klass - The class

Returns:

The layout context

layoutInstanceFields

public void layoutInstanceFields(RVMClass klass)

This is where a class gets laid out. Differences in layout strategy are largely encapsulated in the layoutContext object.

Parameters:

klass - The class to lay out.

updateClass

protected void updateClass(RVMClass klass,
                           FieldLayoutContext fieldLayout)

Updates the RVMClass with context info.

Parameters:

klass - the class to update

fieldLayout - the layout for the class

setOffset

protected void setOffset(RVMClass klass,
                         RVMField field,
                         int offset)

Update a field to set its offset within the object.

Parameters:

klass - the class that the field belongs to

field - the field

offset - the new offset for the field

layoutField

protected void layoutField(FieldLayoutContext layout,
                           RVMClass klass,
                           RVMField field,
                           int fieldSize)

Lay out a given field.

Parameters:

layout - State for the layout process

klass - The class whose fields we're laying out.

field - The field we are laying out.

fieldSize - The size of the field in bytes