package org.apache.lucene.analysis;
/**
* 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 java.io.IOException;
import java.io.Reader;
/** An abstract base class for simple, character-oriented tokenizers.*/
public abstract class CharTokenizer extends Tokenizer {
public CharTokenizer(Reader input) {
super(input);
}
private int offset = 0, bufferIndex = 0, dataLen = 0;
private static final int MAX_WORD_LEN = 255;
private static final int IO_BUFFER_SIZE = 1024;
private final char[] buffer = new char[MAX_WORD_LEN];
private final char[] ioBuffer = new char[IO_BUFFER_SIZE];
/** Returns true iff a character should be included in a token. This
* tokenizer generates as tokens adjacent sequences of characters which
* satisfy this predicate. Characters for which this is false are used to
* define token boundaries and are not included in tokens. */
protected abstract boolean isTokenChar(char c);
/** Called on each token character to normalize it before it is added to the
* token. The default implementation does nothing. Subclasses may use this
* to, e.g., lowercase tokens. */
protected char normalize(char c) {
return c;
}
/** Returns the next token in the stream, or null at EOS. */
public final Token next() throws IOException {
int length = 0;
int start = offset;
while (true) {
final char c;
offset++;
if (bufferIndex >= dataLen) {
dataLen = input.read(ioBuffer);
bufferIndex = 0;
}
;
if (dataLen == -1) {
if (length > 0)
break;
else
return null;
} else
c = ioBuffer[bufferIndex++];
if (isTokenChar(c)) { // if it's a token char
if (length == 0) // start of token
start = offset - 1;
buffer[length++] = normalize(c); // buffer it, normalized
if (length == MAX_WORD_LEN) // buffer overflow!
break;
} else if (length > 0) // at non-Letter w/ chars
break; // return 'em
}
return new Token(new String(buffer, 0, length), start, start + length);
}
}
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