package org.apache.lucene.util.encoding;

import java.io.IOException;
import java.io.InputStream;

/**
 * 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.
 */

/**
 * Decodes integers from a set {@link InputStream}. For re-usability, the
 * decoder's input stream can be set by ({@link #reInit(InputStream)}).
 * By design, Decoders are NOT thread-safe.
 * 
 * @lucene.experimental
 */
public abstract class IntDecoder {
  
  /** A special long value which is used to indicate end-of-stream has reached. */
  public static final long EOS = 0x100000000L;

  /** Input stream from which the encoded bytes are read */
  protected InputStream in;

  /** Sets the input stream from which the encoded data is read. */
  public void reInit(InputStream in) {
    this.in = in;
  }
  
  /**
   * Decodes data received from the input stream, and returns one decoded
   * integer. If end of stream is reached, {@link #EOS} is returned.
   * 
   * @return one decoded integer as long or {@link #EOS} if end-of-stream
   *         reached.
   * @throws IOException if an I/O error occurs
   */
  public abstract long decode() throws IOException;

}
