org.apache.lucene.analysis.miscellaneous

Class ASCIIFoldingFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.analysis.miscellaneous.ASCIIFoldingFilter

All Implemented Interfaces:

Closeable, AutoCloseable

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:

• C1 Controls and Latin-1 Supplement: http://www.unicode.org/charts/PDF/U0080.pdf
• Latin Extended-A: http://www.unicode.org/charts/PDF/U0100.pdf
• Latin Extended-B: http://www.unicode.org/charts/PDF/U0180.pdf
• Latin Extended Additional: http://www.unicode.org/charts/PDF/U1E00.pdf
• Latin Extended-C: http://www.unicode.org/charts/PDF/U2C60.pdf
• Latin Extended-D: http://www.unicode.org/charts/PDF/UA720.pdf
• IPA Extensions: http://www.unicode.org/charts/PDF/U0250.pdf
• Phonetic Extensions: http://www.unicode.org/charts/PDF/U1D00.pdf
• Phonetic Extensions Supplement: http://www.unicode.org/charts/PDF/U1D80.pdf
• General Punctuation: http://www.unicode.org/charts/PDF/U2000.pdf
• Superscripts and Subscripts: http://www.unicode.org/charts/PDF/U2070.pdf
• Enclosed Alphanumerics: http://www.unicode.org/charts/PDF/U2460.pdf
• Dingbats: http://www.unicode.org/charts/PDF/U2700.pdf
• Supplemental Punctuation: http://www.unicode.org/charts/PDF/U2E00.pdf
• Alphabetic Presentation Forms: http://www.unicode.org/charts/PDF/UFB00.pdf
• Halfwidth and Fullwidth Forms: http://www.unicode.org/charts/PDF/UFF00.pdf

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.State

Field Summary

Fields inherited from class org.apache.lucene.analysis.TokenFilter

input

Fields inherited from class org.apache.lucene.analysis.TokenStream

DEFAULT_TOKEN_ATTRIBUTE_FACTORY

Constructor Summary

Constructors

Constructor and Description
ASCIIFoldingFilter(TokenStream input)
ASCIIFoldingFilter(TokenStream input, boolean preserveOriginal) Create a new ASCIIFoldingFilter.

Method Summary

Modifier and Type	Method and Description
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, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, 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.