com.sleepycat.je.cleaner

Class OffsetList

java.lang.Object

com.sleepycat.je.cleaner.OffsetList

public class OffsetList
extends java.lang.Object

List of LSN offsets as a linked list of segments. The reasons for using a list of this type and not a java.util.List are:

• Segements reduce memory overhead by storing long primitives rather than Long objects. Many longs per segment reduce link overhead.
• Memory is only allocated for new segments, reducing the number of calls to update the memory budget.
• This is an append-only list that supports a single appender thread and multiple unsynchronized reader threads. The caller is responsible for synchronizing such that only one thread calls add() at one time. The reader threads see data as it is changing but do not see inconsistent data (corrupt longs) and do not require synchronization for thread safety.

The algorithms here use traversal of the list segments rather than recursion to avoid using a lot of stack space.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	OffsetList.Segment One segment of a OffsetList containing at most SEGMENT_CAPACITY values.

Constructor Summary

Constructors

Constructor and Description
OffsetList()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	add(long value, boolean checkDupOffsets) Adds the given value and returns whether a new segment was allocated.
int	size()
long[]	toArray() Returns an array of all values as longs.

Methods inherited from class java.lang.Object

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

Constructor Detail

OffsetList

public OffsetList()

Method Detail

add

public boolean add(long value,
          boolean checkDupOffsets)

Adds the given value and returns whether a new segment was allocated.

size

public int size()

toArray

public long[] toArray()

Returns an array of all values as longs. If a writer thread is appending to the list while this method is excuting, some values may be missing from the returned array, but the operation is safe.