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`
  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)`
  Given a String array, answer true if the array is correctly cached.
  `protected void`
  `cacheArray(String[] array)`
  Cache the array passed in as the argument
  `List<Integer>`
  `indexesForArrayKey(String[] array, String key)`
  Answer 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)
    Given a String array, answer true if the array is correctly cached. Answer 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)
    Cache the array passed in as the argument
    Parameters:
      `array` - String[] to cache

  - ### indexesForArrayKey

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