org.apache.lucene.analysis.util

Class CharacterUtils

java.lang.Object

org.apache.lucene.analysis.util.CharacterUtils

public abstract class CharacterUtils
extends Object

CharacterUtils provides a unified interface to Character-related operations to implement backwards compatible character operations based on a Version instance.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CharacterUtils.CharacterBuffer A simple IO buffer to use with fill(CharacterBuffer, Reader).

Constructor Summary

Constructors

Constructor and Description
CharacterUtils()

Method Summary

Methods

Modifier and Type	Method and Description
abstract int	codePointAt(char[] chars, int offset, int limit) Returns the code point at the given index of the char array where only elements with index less than the limit are used.
abstract int	codePointAt(CharSequence seq, int offset) Returns the code point at the given index of the CharSequence.
abstract int	codePointCount(CharSequence seq) Return the number of characters in seq.
boolean	fill(CharacterUtils.CharacterBuffer buffer, Reader reader) Convenience method which calls fill(buffer, reader, buffer.buffer.length).
abstract boolean	fill(CharacterUtils.CharacterBuffer buffer, Reader reader, int numChars) Fills the CharacterUtils.CharacterBuffer with characters read from the given reader Reader.
static CharacterUtils	getInstance() Returns a CharacterUtils implementation.
static CharacterUtils	getJava4Instance() Deprecated. Only for n-gram backwards compat
static CharacterUtils.CharacterBuffer	newCharacterBuffer(int bufferSize) Creates a new CharacterUtils.CharacterBuffer and allocates a char[] of the given bufferSize.
abstract int	offsetByCodePoints(char[] buf, int start, int count, int index, int offset) Return the index within buf[start:start+count] which is by offset code points from index.
int	toChars(int[] src, int srcOff, int srcLen, char[] dest, int destOff) Converts a sequence of unicode code points to a sequence of Java characters.
int	toCodePoints(char[] src, int srcOff, int srcLen, int[] dest, int destOff) Converts a sequence of Java characters to a sequence of unicode code points.
void	toLowerCase(char[] buffer, int offset, int limit) Converts each unicode codepoint to lowerCase via Character.toLowerCase(int) starting at the given offset.
void	toUpperCase(char[] buffer, int offset, int limit) Converts each unicode codepoint to UpperCase via Character.toUpperCase(int) starting at the given offset.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CharacterUtils

public CharacterUtils()

Method Detail

getInstance

public static CharacterUtils getInstance()

Returns a CharacterUtils implementation.

Returns:

a CharacterUtils implementation according to the given Version instance.

getJava4Instance

@Deprecated
public static CharacterUtils getJava4Instance()

Deprecated. Only for n-gram backwards compat

explicitly returns a version matching java 4 semantics

codePointAt

public abstract int codePointAt(CharSequence seq,
              int offset)

Returns the code point at the given index of the CharSequence.

Parameters:

seq - a character sequence

offset - the offset to the char values in the chars array to be converted

Returns:

the Unicode code point at the given index

Throws:

NullPointerException - - if the sequence is null.

IndexOutOfBoundsException - - if the value offset is negative or not less than the length of the character sequence.

codePointAt

public abstract int codePointAt(char[] chars,
              int offset,
              int limit)

Returns the code point at the given index of the char array where only elements with index less than the limit are used.

Parameters:

chars - a character array

offset - the offset to the char values in the chars array to be converted

limit - the index afer the last element that should be used to calculate codepoint.

Returns:

the Unicode code point at the given index

Throws:

NullPointerException - - if the array is null.

IndexOutOfBoundsException - - if the value offset is negative or not less than the length of the char array.

codePointCount

public abstract int codePointCount(CharSequence seq)

Return the number of characters in seq.

newCharacterBuffer

public static CharacterUtils.CharacterBuffer newCharacterBuffer(int bufferSize)

Creates a new CharacterUtils.CharacterBuffer and allocates a char[] of the given bufferSize.

Parameters:

bufferSize - the internal char buffer size, must be >= 2

Returns:

a new CharacterUtils.CharacterBuffer instance.

toLowerCase

public final void toLowerCase(char[] buffer,
               int offset,
               int limit)

Converts each unicode codepoint to lowerCase via Character.toLowerCase(int) starting at the given offset.

Parameters:

buffer - the char buffer to lowercase

offset - the offset to start at

limit - the max char in the buffer to lower case

toUpperCase

public final void toUpperCase(char[] buffer,
               int offset,
               int limit)

Converts each unicode codepoint to UpperCase via Character.toUpperCase(int) starting at the given offset.

Parameters:

buffer - the char buffer to UPPERCASE

offset - the offset to start at

limit - the max char in the buffer to lower case

toCodePoints

public final int toCodePoints(char[] src,
               int srcOff,
               int srcLen,
               int[] dest,
               int destOff)

Converts a sequence of Java characters to a sequence of unicode code points.

Returns:

the number of code points written to the destination buffer

toChars

public final int toChars(int[] src,
          int srcOff,
          int srcLen,
          char[] dest,
          int destOff)

Converts a sequence of unicode code points to a sequence of Java characters.

Returns:

the number of chars written to the destination buffer

fill

public abstract boolean fill(CharacterUtils.CharacterBuffer buffer,
           Reader reader,
           int numChars)
                      throws IOException

Fills the CharacterUtils.CharacterBuffer with characters read from the given reader Reader. This method tries to read numChars characters into the CharacterUtils.CharacterBuffer, each call to fill will start filling the buffer from offset 0 up to numChars. In case code points can span across 2 java characters, this method may only fill numChars - 1 characters in order not to split in the middle of a surrogate pair, even if there are remaining characters in the Reader.

This method guarantees that the given CharacterUtils.CharacterBuffer will never contain a high surrogate character as the last element in the buffer unless it is the last available character in the reader. In other words, high and low surrogate pairs will always be preserved across buffer boarders.

A return value of false means that this method call exhausted the reader, but there may be some bytes which have been read, which can be verified by checking whether buffer.getLength() > 0.

Parameters:

buffer - the buffer to fill.

reader - the reader to read characters from.

numChars - the number of chars to read

Returns:

false if and only if reader.read returned -1 while trying to fill the buffer

Throws:

IOException - if the reader throws an IOException.

fill

public final boolean fill(CharacterUtils.CharacterBuffer buffer,
           Reader reader)
                   throws IOException

Convenience method which calls fill(buffer, reader, buffer.buffer.length).

Throws:

IOException

offsetByCodePoints

public abstract int offsetByCodePoints(char[] buf,
                     int start,
                     int count,
                     int index,
                     int offset)

Return the index within buf[start:start+count] which is by offset code points from index.