Lucene example source code file (FastCharStream.java)

This example Lucene source code file (FastCharStream.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

begintoken, charstream, done, fastcharstream, fastcharstream, getimage, getsuffix, io, ioexception, ioexception, reader, reader, string, string

The Lucene FastCharStream.java source code

// FastCharStream.java
package org.apache.lucene.queryParser.surround.parser;
/**
 * 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.*;

/** An efficient implementation of JavaCC's CharStream interface.  <p>Note that
 * this does not do line-number counting, but instead keeps track of the
 * character position of the token in the input, as required by Lucene's {@link
 * org.apache.lucene.analysis.Token} API. */
public final class FastCharStream implements CharStream {
  char[] buffer = null;

  int bufferLength = 0;				  // end of valid chars
  int bufferPosition = 0;			  // next char to read

  int tokenStart = 0;				  // offset in buffer
  int bufferStart = 0;				  // position in file of buffer

  Reader input;					  // source of chars

  /** Constructs from a Reader. */
  public FastCharStream(Reader r) {
    input = r;
  }

  public final char readChar() throws IOException {
    if (bufferPosition >= bufferLength)
      refill();
    return buffer[bufferPosition++];
  }

  private final void refill() throws IOException {
    int newPosition = bufferLength - tokenStart;

    if (tokenStart == 0) {			  // token won't fit in buffer
      if (buffer == null) {			  // first time: alloc buffer
	buffer = new char[2048];
      } else if (bufferLength == buffer.length) { // grow buffer
	char[] newBuffer = new char[buffer.length*2];
	System.arraycopy(buffer, 0, newBuffer, 0, bufferLength);
	buffer = newBuffer;
      }
    } else {					  // shift token to front
      System.arraycopy(buffer, tokenStart, buffer, 0, newPosition);
    }

    bufferLength = newPosition;			  // update state
    bufferPosition = newPosition;
    bufferStart += tokenStart;
    tokenStart = 0;

    int charsRead =				  // fill space in buffer
      input.read(buffer, newPosition, buffer.length-newPosition);
    if (charsRead == -1)
      throw new IOException("read past eof");
    else
      bufferLength += charsRead;
  }

  public final char BeginToken() throws IOException {
    tokenStart = bufferPosition;
    return readChar();
  }

  public final void backup(int amount) {
    bufferPosition -= amount;
  }

  public final String GetImage() {
    return new String(buffer, tokenStart, bufferPosition - tokenStart);
  }

  public final char[] GetSuffix(int len) {
    char[] value = new char[len];
    System.arraycopy(buffer, bufferPosition - len, value, 0, len);
    return value;
  }

  public final void Done() {
    try {
      input.close();
    } catch (IOException e) {
      System.err.println("Caught: " + e + "; ignoring.");
    }
  }

  public final int getColumn() {
    return bufferStart + bufferPosition;
  }
  public final int getLine() {
    return 1;
  }
  public final int getEndColumn() {
    return bufferStart + bufferPosition;
  }
  public final int getEndLine() {
    return 1;
  }
  public final int getBeginColumn() {
    return bufferStart + tokenStart;
  }
  public final int getBeginLine() {
    return 1;
  }
}