org.jscience.linguistics.search
Class BoyerMooreHorspool

java.lang.Object
  org.jscience.linguistics.search.StringSearch
      org.jscience.linguistics.search.BoyerMooreHorspool

Direct Known Subclasses:

BoyerMooreHorspoolRaita

public class BoyerMooreHorspool
extends StringSearch

An implementation of Horspool's improved version of the Boyer-Moore String searching algorithm. See "Practical fast searching in strings" (appeared in Software - Practice & Experience, 10(6):501-506). Unfortunately, there seems to be no on-line version of his paper.

This is the second fastest algorithm in this library for the searchChars and searchString. Except for very short patterns (< 5 characters), it is always faster than any other algorithm except BoyerMooreHorspoolRaita and faster than String.indexOf(java.lang.String) by more than 5 times for patterns longer than 24 characters. It's searchBytes methods are slightly faster than in the BoyerMooreHorspoolRaita algorithm.

This implementation is based on Ricardo Baeza-Yates' implementation.

Preprocessing: O(m + ∑) time

 Processing   : O(mn) worst case

Nested Class Summary

Nested classes/interfaces inherited from class org.jscience.linguistics.search.StringSearch

StringSearch.Dispatch, StringSearch.ReflectionDispatch

Field Summary

Fields inherited from class org.jscience.linguistics.search.StringSearch

activeDispatch, useNative

Constructor Summary

BoyerMooreHorspool()
Constructor for BoyerMooreHorspool.

Method Summary

java.lang.Object	processBytes(byte[] pattern) Returns a int array.
java.lang.Object	processChars(char[] pattern) Returns a CharIntMap.
int	searchBytes(byte[] text, int textStart, int textEnd, byte[] pattern, java.lang.Object processed) Returns the position in the text at which the pattern was found.
int	searchChars(char[] text, int textStart, int textEnd, char[] pattern, java.lang.Object processed) Returns the index of the pattern in the text using the pre-processed Object.

Methods inherited from class org.jscience.linguistics.search.StringSearch

createCharIntMap, createCharIntMap, equals, hashCode, index, processString, searchBytes, searchBytes, searchBytes, searchBytes, searchBytes, searchChars, searchChars, searchChars, searchChars, searchChars, searchString, searchString, searchString, searchString, searchString, searchString, toString, toStringBuffer, usesNative, usesReflection

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

BoyerMooreHorspool

public BoyerMooreHorspool()

Constructor for BoyerMooreHorspool. Note that it is not required to create multiple instances.

Method Detail

processBytes

public java.lang.Object processBytes(byte[] pattern)

Returns a int array.

Specified by:

processBytes in class StringSearch

Parameters:

pattern - the byte array containing the pattern, may not be null

Returns:

an Object

See Also:

StringSearch.processBytes(byte[])

processChars

public java.lang.Object processChars(char[] pattern)

Returns a CharIntMap.

Specified by:

processChars in class StringSearch

Parameters:

pattern - a char array containing the pattern, may not be null

Returns:

an Object

See Also:

StringSearch.processChars(char[])

searchBytes

public int searchBytes(byte[] text,
                       int textStart,
                       int textEnd,
                       byte[] pattern,
                       java.lang.Object processed)

Description copied from class: StringSearch

Returns the position in the text at which the pattern was found. Returns -1 if the pattern was not found.

Specified by:

searchBytes in class StringSearch

Parameters:

text - text the byte array containing the text, may not be null

textStart - at which position in the text the comparing should start

textEnd - at which position in the text comparing should stop

pattern - the pattern to search for, may not be null

processed - an Object as returned from StringSearch.processBytes(byte[]), may not be null

Returns:

the position in the text or -1 if the pattern was not found

See Also:

StringSearch.searchBytes(byte[], int,int,byte[],java.lang.Object)

searchChars

public int searchChars(char[] text,
                       int textStart,
                       int textEnd,
                       char[] pattern,
                       java.lang.Object processed)

Description copied from class: StringSearch

Returns the index of the pattern in the text using the pre-processed Object. Returns -1 if the pattern was not found.

Specified by:

searchChars in class StringSearch

Parameters:

text - the String containing the text, may not be null

textStart - at which position in the text the comparing should start

textEnd - at which position in the text comparing should stop

pattern - the pattern to search for, may not be null

processed - an Object as returned from StringSearch.processChars(char[]) or StringSearch.processString(String), may not be null

Returns:

the position in the text or -1 if the pattern was not found

See Also:

StringSearch.searchChars(char[], int,int,char[],Object)