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Apache Hadoop Common
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/**
 * 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.
 */
package org.apache.hadoop.net;

import java.io.FilterInputStream;

import java.io.InputStream;
import java.net.Socket;
import java.net.SocketException;
import java.nio.channels.ReadableByteChannel;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

import org.apache.hadoop.thirdparty.com.google.common.base.Preconditions;

/**
 * A wrapper stream around a socket which allows setting of its timeout. If the
 * socket has a channel, this uses non-blocking IO via the package-private
 * {@link SocketInputStream} implementation. Otherwise, timeouts are managed by
 * setting the underlying socket timeout itself.
 */
@InterfaceAudience.LimitedPrivate("HDFS")
@InterfaceStability.Unstable
public class SocketInputWrapper extends FilterInputStream {
  private final Socket socket;
  private final boolean hasChannel;

  SocketInputWrapper(Socket s, InputStream is) {
    super(is);
    this.socket = s;
    this.hasChannel = s.getChannel() != null;
    if (hasChannel) {
      Preconditions.checkArgument(is instanceof SocketInputStream,
          "Expected a SocketInputStream when there is a channel. " +
          "Got: %s", is);
    }
  }

  /**
   * Set the timeout for reads from this stream.
   * 
   * Note: the behavior here can differ subtly depending on whether the
   * underlying socket has an associated Channel. In particular, if there is no
   * channel, then this call will affect the socket timeout for all
   * readers of this socket. If there is a channel, then this call will affect
   * the timeout only for this stream. As such, it is recommended to
   * only create one {@link SocketInputWrapper} instance per socket.
   * 
   * @param timeoutMs
   *          the new timeout, 0 for no timeout
   * @throws SocketException
   *           if the timeout cannot be set
   */
  public void setTimeout(long timeoutMs) throws SocketException {
    if (hasChannel) {
      ((SocketInputStream)in).setTimeout(timeoutMs);
    } else {
      socket.setSoTimeout((int)timeoutMs);
    }
  }

  /**
   * @return an underlying ReadableByteChannel implementation.
   * @throws IllegalStateException if this socket does not have a channel
   */
  public ReadableByteChannel getReadableByteChannel() {
    Preconditions.checkState(hasChannel,
        "Socket %s does not have a channel",
        this.socket);
    return (SocketInputStream)in;
  }
}