fastcharstream.java

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// FastCharStream.java
package org.apache.lucene.analysis.standard;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Lucene" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Lucene", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

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;
  }
}