org.apache.lucene.analysis.miscellaneous
Class ASCIIFoldingFilter

java.lang.Object
  extended by org.apache.lucene.util.AttributeSource
      extended by org.apache.lucene.analysis.TokenStream
          extended by org.apache.lucene.analysis.TokenFilter
              extended by org.apache.lucene.analysis.miscellaneous.ASCIIFoldingFilter
All Implemented Interfaces:
Closeable

public final class ASCIIFoldingFilter
extends TokenFilter

This class converts alphabetic, numeric, and symbolic Unicode characters which are not in the first 127 ASCII characters (the "Basic Latin" Unicode block) into their ASCII equivalents, if one exists. Characters from the following Unicode blocks are converted; however, only those characters with reasonable ASCII alternatives are converted:

See: http://en.wikipedia.org/wiki/Latin_characters_in_Unicode For example, 'à' will be replaced by 'a'.


Nested Class Summary
 
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
 
Field Summary
 
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
 
Constructor Summary
ASCIIFoldingFilter(TokenStream input)
           
ASCIIFoldingFilter(TokenStream input, boolean preserveOriginal)
          Create a new ASCIIFoldingFilter.
 
Method Summary
 void foldToASCII(char[] input, int length)
          Converts characters above ASCII to their ASCII equivalents.
static int foldToASCII(char[] input, int inputPos, char[] output, int outputPos, int length)
          Converts characters above ASCII to their ASCII equivalents.
 boolean incrementToken()
           
 boolean isPreserveOriginal()
          Does the filter preserve the original tokens?
 void reset()
           
 
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end
 
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

ASCIIFoldingFilter

public ASCIIFoldingFilter(TokenStream input)

ASCIIFoldingFilter

public ASCIIFoldingFilter(TokenStream input,
                          boolean preserveOriginal)
Create a new ASCIIFoldingFilter.

Parameters:
input - TokenStream to filter
preserveOriginal - should the original tokens be kept on the input stream with a 0 position increment from the folded tokens?
Method Detail

isPreserveOriginal

public boolean isPreserveOriginal()
Does the filter preserve the original tokens?


incrementToken

public boolean incrementToken()
                       throws IOException
Specified by:
incrementToken in class TokenStream
Throws:
IOException

reset

public void reset()
           throws IOException
Overrides:
reset in class TokenFilter
Throws:
IOException

foldToASCII

public void foldToASCII(char[] input,
                        int length)
Converts characters above ASCII to their ASCII equivalents. For example, accents are removed from accented characters.

Parameters:
input - The string to fold
length - The number of characters in the input string

foldToASCII

public static final int foldToASCII(char[] input,
                                    int inputPos,
                                    char[] output,
                                    int outputPos,
                                    int length)
Converts characters above ASCII to their ASCII equivalents. For example, accents are removed from accented characters.

Parameters:
input - The characters to fold
inputPos - Index of the first character to fold
output - The result of the folding. Should be of size >= length * 4.
outputPos - Index of output where to put the result of the folding
length - The number of characters to fold
Returns:
length of output
NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.


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