Module org.apache.lucene.analysis.common

Package org.apache.lucene.analysis.reverse

Class ReverseStringFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.analysis.reverse.ReverseStringFilter

All Implemented Interfaces:

Closeable, AutoCloseable, Unwrappable<TokenStream>

public final class ReverseStringFilter
extends TokenFilter

Reverse token string, for example "country" => "yrtnuoc".

If marker is supplied, then tokens will be also prepended by that character. For example, with a marker of \u0001, "country" => "\u0001yrtnuoc". This is useful when implementing efficient leading wildcards search.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.State

Field Summary

Fields

Modifier and Type	Field	Description
static final char	INFORMATION_SEPARATOR_MARKER	Example marker character: U+001F (INFORMATION SEPARATOR ONE)
private final char	marker
private static final char	NOMARKER
static final char	PUA_EC00_MARKER	Example marker character: U+EC00 (PRIVATE USE AREA: EC00)
static final char	RTL_DIRECTION_MARKER	Example marker character: U+200F (RIGHT-TO-LEFT MARK)
static final char	START_OF_HEADING_MARKER	Example marker character: U+0001 (START OF HEADING)
private final CharTermAttribute	termAtt

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	Description
ReverseStringFilter(TokenStream in)	Create a new ReverseStringFilter that reverses all tokens in the supplied TokenStream.
ReverseStringFilter(TokenStream in, char marker)	Create a new ReverseStringFilter that reverses and marks all tokens in the supplied TokenStream.

Method Summary

Modifier and Type	Method	Description
boolean	incrementToken()	Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
static void	reverse(char[] buffer)	Reverses the given input buffer in-place
static void	reverse(char[] buffer, int len)	Partially reverses the given input buffer in-place from offset 0 up to the given length.
static void	reverse(char[] buffer, int start, int len)	Partially reverses the given input buffer in-place from the given offset up to the given length.
static String	reverse(String input)	Reverses the given input string

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

close, end, reset, unwrap

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

Field Details

termAtt

private final CharTermAttribute termAtt

marker

private final char marker

NOMARKER

private static final char NOMARKER

See Also:

• Constant Field Values

START_OF_HEADING_MARKER

public static final char START_OF_HEADING_MARKER

Example marker character: U+0001 (START OF HEADING)

See Also:

• Constant Field Values

INFORMATION_SEPARATOR_MARKER

public static final char INFORMATION_SEPARATOR_MARKER

Example marker character: U+001F (INFORMATION SEPARATOR ONE)

See Also:

• Constant Field Values

PUA_EC00_MARKER

public static final char PUA_EC00_MARKER

Example marker character: U+EC00 (PRIVATE USE AREA: EC00)

See Also:

• Constant Field Values

RTL_DIRECTION_MARKER

public static final char RTL_DIRECTION_MARKER

Example marker character: U+200F (RIGHT-TO-LEFT MARK)

See Also:

• Constant Field Values

Constructor Details

ReverseStringFilter

public ReverseStringFilter(TokenStream in)

Create a new ReverseStringFilter that reverses all tokens in the supplied TokenStream.

The reversed tokens will not be marked.

Parameters:

in - TokenStream to filter

ReverseStringFilter

public ReverseStringFilter(TokenStream in,
 char marker)

Create a new ReverseStringFilter that reverses and marks all tokens in the supplied TokenStream.

The reversed tokens will be prepended (marked) by the marker character.

Parameters:

in - TokenStream to filter

marker - A character used to mark reversed tokens

Method Details

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

reverse

public static String reverse(String input)

Reverses the given input string

Parameters:

input - the string to reverse

Returns:

the given input string in reversed order

reverse

public static void reverse(char[] buffer)

Reverses the given input buffer in-place

Parameters:

buffer - the input char array to reverse

reverse

public static void reverse(char[] buffer,
 int len)

Partially reverses the given input buffer in-place from offset 0 up to the given length.

Parameters:

buffer - the input char array to reverse

len - the length in the buffer up to where the buffer should be reversed

reverse

public static void reverse(char[] buffer,
 int start,
 int len)

Partially reverses the given input buffer in-place from the given offset up to the given length.

Parameters:

buffer - the input char array to reverse

start - the offset from where to reverse the buffer

len - the length in the buffer up to where the buffer should be reversed