org.mmtk.policy
Class MarkCompactCollector.RegionCursor

java.lang.Object
  org.mmtk.policy.MarkCompactCollector.RegionCursor

Direct Known Subclasses:

MarkCompactCollector.FromCursor, MarkCompactCollector.ToCursor

Enclosing class:

MarkCompactCollector

private abstract static class MarkCompactCollector.RegionCursor
extends Object

Both the 'compact' and 'calculate' phases can be thought of as sweeping a pair of cursors across a linked list of regions. Each cursor requires maintaining pointers to the current region, the current address and the end of the region. The regionCursor class maintains these 3 pointers, while the subclasses ToCursor and FromCursor provide methods specific to the read and write pointers.

name

private final String name

Name of the cursor - for debugging messages

region

protected Address region

The current region, or zero if the cursor is invalid (eg after advancing past the end of the current work list

limit

protected Address limit

The limit of the current region. When reading a populated region, this is the address of the last used byte. When writing to a fresh region, this is the last byte in the region.

cursor

protected Address cursor

The current address

MarkCompactCollector.RegionCursor

public MarkCompactCollector.RegionCursor(String name)

Parameters:

name - The name of the region - for debugging messages.

init

abstract void init(Address region)

Hook to allow subclasses to initialize the cursor in different ways.

Parameters:

region - The region to be processed.

assertCursorInBounds

protected void assertCursorInBounds()

Assert that the cursor is within the bounds of the region. Calls to this must be guarded by if (VM.VERIFY_ASSERTIONS)

inc

void inc(int size)

Increment the cursor.

Parameters:

size - Bytes to increment by

incTo

public void incTo(Address cursor)

Increment the cursor to a specific address

Parameters:

cursor - Destination address

sameRegion

boolean sameRegion(MarkCompactCollector.RegionCursor other)

Parameters:

other - Other region

Returns:

true if this cursor points to the same region as other

isAvailable

boolean isAvailable(int size)

Parameters:

size - Size in bytes

Returns:

true if size bytes are available in the current region

get

public Address get()

Returns:

The current cursor

getRegion

public Address getRegion()

Returns:

The current region pointer

getLimit

public Address getLimit()

Returns:

The current region limit

advanceToNextRegion

void advanceToNextRegion()

Follow the linked-list of regions to the next region.

isValid

boolean isValid()

Returns:

true if we haven't advanced beyond the end of the region list

isInRegion

boolean isInRegion(ObjectReference ref)

Parameters:

ref - The object in question

Returns:

true if the object's start address is in this region

print

void print()

Print the cursor - for debugging