core/src/main/scala/org/apache/spark/util/SerializableBuffer.scala

/*
 * 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.spark.util

import java.io.{EOFException, IOException, ObjectInputStream, ObjectOutputStream}
import java.nio.ByteBuffer
import java.nio.channels.Channels

/**
 * A wrapper around a java.nio.ByteBuffer that is serializable through Java serialization, to make
 * it easier to pass ByteBuffers in case class messages.
 */
private[spark]
class SerializableBuffer(@transient var buffer: ByteBuffer) extends Serializable {
  def value: ByteBuffer = buffer

  private def readObject(in: ObjectInputStream): Unit = Utils.tryOrIOException {
    val length = in.readInt()
    buffer = ByteBuffer.allocate(length)
    var amountRead = 0
    val channel = Channels.newChannel(in)
    while (amountRead < length) {
      val ret = channel.read(buffer)
      if (ret == -1) {
        throw new EOFException("End of file before fully reading buffer")
      }
      amountRead += ret
    }
    buffer.rewind() // Allow us to read it later
  }

  private def writeObject(out: ObjectOutputStream): Unit = Utils.tryOrIOException {
    out.writeInt(buffer.limit())
    if (Channels.newChannel(out).write(buffer) != buffer.limit()) {
      throw new IOException("Could not fully write buffer to output stream")
    }
    buffer.rewind() // Allow us to write it again later
  }
}