Package org.apache.commons.compress.harmony.unpack200

Class SegmentConstantPoolArrayCache

java.lang.Object

org.apache.commons.compress.harmony.unpack200.SegmentConstantPoolArrayCache

public class SegmentConstantPoolArrayCache
extends Object

The SegmentConstantPool spends a lot of time searching through large arrays of Strings looking for matches. This can be sped up by caching the arrays in HashMaps so the String keys are looked up and resolve to positions in the array rather than iterating through the arrays each time. Because the arrays only grow (never shrink or change) we can use the last known size as a way to determine if the array has changed. Note that this cache must be synchronized externally if it is shared.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected class	SegmentConstantPoolArrayCache.CachedArray	Keeps track of the last known size of an array as well as a HashMap that knows the mapping from element values to the indices of the array which contain that value.

Field Summary

Fields

Modifier and Type	Field	Description
protected IdentityHashMap<String[],SegmentConstantPoolArrayCache.CachedArray>	knownArrays
protected String[]	lastArray
protected List<Integer>	lastIndexes
protected String	lastKey

Constructor Summary

Constructors

Constructor	Description
SegmentConstantPoolArrayCache()

Method Summary

Modifier and Type	Method	Description
protected boolean	arrayIsCached(String[] array)	Tests whether a String array is correctly cached.
protected void	cacheArray(String[] array)	Caches the array passed in as the argument
List<Integer>	indexesForArrayKey(String[] array, String key)	Gets the indices for the given key in the given array.

Methods inherited from class java.lang.Object

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

Field Details

knownArrays

protected IdentityHashMap<String[],SegmentConstantPoolArrayCache.CachedArray> knownArrays

lastIndexes

protected List<Integer> lastIndexes

lastArray

protected String[] lastArray

lastKey

protected String lastKey

Constructor Details

SegmentConstantPoolArrayCache

public SegmentConstantPoolArrayCache()

Method Details

arrayIsCached

protected boolean arrayIsCached(String[] array)

Tests whether a String array is correctly cached. Return false if the array is not cached, or if the array cache is outdated.

Parameters:

array - of String

Returns:

boolean true if up-to-date cache, otherwise false.

cacheArray

protected void cacheArray(String[] array)

Caches the array passed in as the argument

Parameters:

array - String[] to cache

indexesForArrayKey

public List<Integer> indexesForArrayKey(String[] array,
 String key)

Gets the indices for the given key in the given array. If no such key exists in the cached array, answer -1.

Parameters:

array - String[] array to search for the value

key - String value for which to search

Returns:

List collection of index positions in the array