package org.apache.lucene.analysis.cjk;
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import org.apache.lucene.analysis.Token;
import org.apache.lucene.analysis.Tokenizer;
import java.io.Reader;
/**
* CJKTokenizer was modified from StopTokenizer which does a decent job for
* most European languages. It performs other token methods for double-byte
* Characters: the token will return at each two charactors with overlap match.<br>
* Example: "java C1C2C3C4" will be segment to: "java" "C1C2" "C2C3" "C3C4" it
* also need filter filter zero length token ""<br>
* for Digit: digit, '+', '#' will token as letter<br>
* for more info on Asia language(Chinese Japanese Korean) text segmentation:
* please search <a
* href="http://www.google.com/search?q=word+chinese+segment">google</a>
*
* @author Che, Dong
*/
public final class CJKTokenizer extends Tokenizer {
//~ Static fields/initializers ---------------------------------------------
/** Max word length */
private static final int MAX_WORD_LEN = 255;
/** buffer size: */
private static final int IO_BUFFER_SIZE = 256;
//~ Instance fields --------------------------------------------------------
/** word offset, used to imply which character(in ) is parsed */
private int offset = 0;
/** the index used only for ioBuffer */
private int bufferIndex = 0;
/** data length */
private int dataLen = 0;
/**
* character buffer, store the characters which are used to compose <br>
* the returned Token
*/
private final char[] buffer = new char[MAX_WORD_LEN];
/**
* I/O buffer, used to store the content of the input(one of the <br>
* members of Tokenizer)
*/
private final char[] ioBuffer = new char[IO_BUFFER_SIZE];
/** word type: single=>ASCII double=>non-ASCII word=>default */
private String tokenType = "word";
/**
* tag: previous character is a cached double-byte character "C1C2C3C4"
* ----(set the C1 isTokened) C1C2 "C2C3C4" ----(set the C2 isTokened)
* C1C2 C2C3 "C3C4" ----(set the C3 isTokened) "C1C2 C2C3 C3C4"
*/
private boolean preIsTokened = false;
//~ Constructors -----------------------------------------------------------
/**
* Construct a token stream processing the given input.
*
* @param in I/O reader
*/
public CJKTokenizer(Reader in) {
input = in;
}
//~ Methods ----------------------------------------------------------------
/**
* Returns the next token in the stream, or null at EOS.
* See http://java.sun.com/j2se/1.3/docs/api/java/lang/Character.UnicodeBlock.html
* for detail.
*
* @return Token
*
* @throws java.io.IOException - throw IOException when read error <br>
* hanppened in the InputStream
*
*/
public final Token next() throws java.io.IOException {
/** how many character(s) has been stored in buffer */
int length = 0;
/** the position used to create Token */
int start = offset;
while (true) {
/** current charactor */
char c;
/** unicode block of current charactor for detail */
Character.UnicodeBlock ub;
offset++;
if (bufferIndex >= dataLen) {
dataLen = input.read(ioBuffer);
bufferIndex = 0;
}
if (dataLen == -1) {
if (length > 0) {
if (preIsTokened == true) {
length = 0;
preIsTokened = false;
}
break;
} else {
return null;
}
} else {
//get current character
c = ioBuffer[bufferIndex++];
//get the UnicodeBlock of the current character
ub = Character.UnicodeBlock.of(c);
}
//if the current character is ASCII or Extend ASCII
if ((ub == Character.UnicodeBlock.BASIC_LATIN)
|| (ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS)
) {
if (ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS) {
/** convert HALFWIDTH_AND_FULLWIDTH_FORMS to BASIC_LATIN */
int i = (int) c;
i = i - 65248;
c = (char) i;
}
// if the current character is a letter or "_" "+" "#"
if (Character.isLetterOrDigit(c)
|| ((c == '_') || (c == '+') || (c == '#'))
) {
if (length == 0) {
// "javaC1C2C3C4linux" <br>
// ^--: the current character begin to token the ASCII
// letter
start = offset - 1;
} else if (tokenType == "double") {
// "javaC1C2C3C4linux" <br>
// ^--: the previous non-ASCII
// : the current character
offset--;
bufferIndex--;
tokenType = "single";
if (preIsTokened == true) {
// there is only one non-ASCII has been stored
length = 0;
preIsTokened = false;
break;
} else {
break;
}
}
// store the LowerCase(c) in the buffer
buffer[length++] = Character.toLowerCase(c);
tokenType = "single";
// break the procedure if buffer overflowed!
if (length == MAX_WORD_LEN) {
break;
}
} else if (length > 0) {
if (preIsTokened == true) {
length = 0;
preIsTokened = false;
} else {
break;
}
}
} else {
// non-ASCII letter, eg."C1C2C3C4"
if (Character.isLetter(c)) {
if (length == 0) {
start = offset - 1;
buffer[length++] = c;
tokenType = "double";
} else {
if (tokenType == "single") {
offset--;
bufferIndex--;
//return the previous ASCII characters
break;
} else {
buffer[length++] = c;
tokenType = "double";
if (length == 2) {
offset--;
bufferIndex--;
preIsTokened = true;
break;
}
}
}
} else if (length > 0) {
if (preIsTokened == true) {
// empty the buffer
length = 0;
preIsTokened = false;
} else {
break;
}
}
}
}
return new Token(new String(buffer, 0, length), start, start + length,
tokenType
);
}
}
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