org.apache.lucene.analysis
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.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 The set of character conversions supported by this class is a superset of those supported by Lucene's ISOLatin1AccentFilter which strips accents from Latin1 characters. 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)
           
 
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()
          Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
 
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, reset
 
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)
Method Detail

incrementToken

public boolean incrementToken()
                       throws IOException
Description copied from class: TokenStream
Consumers (i.e., IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate AttributeImpls with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use AttributeSource.captureState() to create a copy of the current attribute state.

This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to AttributeSource.addAttribute(Class) and AttributeSource.getAttribute(Class), references to all AttributeImpls that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in TokenStream.incrementToken().

Specified by:
incrementToken in class TokenStream
Returns:
false for end of stream; true otherwise
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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