FieldLayout (Jikes RVM API)

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org.jikesrvm.objectmodel
Class FieldLayout

java.lang.Object
  org.jikesrvm.objectmodel.FieldLayout

All Implemented Interfaces:: SizeConstants

Direct Known Subclasses:: FieldLayoutPacked, FieldLayoutUnpacked

public abstract class FieldLayout
extends Object
implements SizeConstants
extends Object
implements SizeConstants

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
`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

Fields inherited from interface org.jikesrvm.SizeConstants
BITS_IN_ADDRESS, BITS_IN_BOOLEAN, BITS_IN_BYTE, BITS_IN_CHAR, BITS_IN_DOUBLE, BITS_IN_EXTENT, BITS_IN_FLOAT, BITS_IN_INT, BITS_IN_LONG, BITS_IN_OFFSET, BITS_IN_PAGE, BITS_IN_SHORT, BITS_IN_WORD, BYTES_IN_ADDRESS, BYTES_IN_BOOLEAN, BYTES_IN_BYTE, BYTES_IN_CHAR, BYTES_IN_DOUBLE, BYTES_IN_EXTENT, BYTES_IN_FLOAT, BYTES_IN_INT, BYTES_IN_LONG, BYTES_IN_OFFSET, BYTES_IN_PAGE, BYTES_IN_SHORT, BYTES_IN_WORD, LOG_BITS_IN_ADDRESS, LOG_BITS_IN_BOOLEAN, LOG_BITS_IN_BYTE, LOG_BITS_IN_CHAR, LOG_BITS_IN_DOUBLE, LOG_BITS_IN_EXTENT, LOG_BITS_IN_FLOAT, LOG_BITS_IN_INT, LOG_BITS_IN_LONG, LOG_BITS_IN_OFFSET, LOG_BITS_IN_PAGE, LOG_BITS_IN_SHORT, LOG_BITS_IN_WORD, LOG_BYTES_IN_ADDRESS, LOG_BYTES_IN_BOOLEAN, LOG_BYTES_IN_BYTE, LOG_BYTES_IN_CHAR, LOG_BYTES_IN_DOUBLE, LOG_BYTES_IN_EXTENT, LOG_BYTES_IN_FLOAT, LOG_BYTES_IN_INT, LOG_BYTES_IN_LONG, LOG_BYTES_IN_OFFSET, LOG_BYTES_IN_PAGE, LOG_BYTES_IN_SHORT, LOG_BYTES_IN_WORD

Fields inherited from interface org.jikesrvm.SizeConstants

BITS_IN_ADDRESS, BITS_IN_BOOLEAN, BITS_IN_BYTE, BITS_IN_CHAR, BITS_IN_DOUBLE, BITS_IN_EXTENT, BITS_IN_FLOAT, BITS_IN_INT, BITS_IN_LONG, BITS_IN_OFFSET, BITS_IN_PAGE, BITS_IN_SHORT, BITS_IN_WORD, BYTES_IN_ADDRESS, BYTES_IN_BOOLEAN, BYTES_IN_BYTE, BYTES_IN_CHAR, BYTES_IN_DOUBLE, BYTES_IN_EXTENT, BYTES_IN_FLOAT, BYTES_IN_INT, BYTES_IN_LONG, BYTES_IN_OFFSET, BYTES_IN_PAGE, BYTES_IN_SHORT, BYTES_IN_WORD, LOG_BITS_IN_ADDRESS, LOG_BITS_IN_BOOLEAN, LOG_BITS_IN_BYTE, LOG_BITS_IN_CHAR, LOG_BITS_IN_DOUBLE, LOG_BITS_IN_EXTENT, LOG_BITS_IN_FLOAT, LOG_BITS_IN_INT, LOG_BITS_IN_LONG, LOG_BITS_IN_OFFSET, LOG_BITS_IN_PAGE, LOG_BITS_IN_SHORT, LOG_BITS_IN_WORD, LOG_BYTES_IN_ADDRESS, LOG_BYTES_IN_BOOLEAN, LOG_BYTES_IN_BYTE, LOG_BYTES_IN_CHAR, LOG_BYTES_IN_DOUBLE, LOG_BYTES_IN_EXTENT, LOG_BYTES_IN_FLOAT, LOG_BYTES_IN_INT, LOG_BYTES_IN_LONG, LOG_BYTES_IN_OFFSET, LOG_BYTES_IN_PAGE, LOG_BYTES_IN_SHORT, LOG_BYTES_IN_WORD

Constructor Summary
`FieldLayout(boolean largeFieldsFirst, boolean clusterReferenceFields)`

Method Summary
`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)` Log base 2 of an integer
`protected static int`	`max(int x, int y)` Maximum of two integers
`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)` Update 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

max

protected static int max(int x,
                         int y)

Maximum of two integers

log2

protected static int log2(int x)

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)

Update the RVMClass with context info.

Parameters:: klass -; fieldLayout -

setOffset

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

Update a field to set its offset within the object.

Parameters:: klass -; field -; offset -

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.