core/src/main/java/com/google/net/stubby/transport/StreamListener.java

/*
 * Copyright 2014, Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
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 *
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 * notice, this list of conditions and the following disclaimer.
 *    * 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
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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package com.google.net.stubby.transport;

import com.google.common.util.concurrent.ListenableFuture;

import java.io.InputStream;

import javax.annotation.Nullable;

/**
 * An observer of {@link Stream} events. It is guaranteed to only have one concurrent callback at a
 * time.
 */
public interface StreamListener {
  /**
   * Called upon receiving a message from the remote end-point. The {@link InputStream} is
   * non-blocking and contains the entire message.
   *
   * <p>The method optionally returns a future that can be observed by flow control to determine
   * when the message has been processed by the application. If {@code null} is returned, processing
   * of this message is assumed to be complete upon returning from this method.
   *
   * <p>The {@code message} {@link InputStream} will be closed when the returned future completes.
   * If no future is returned, the stream will be closed immediately after returning from this
   * method.
   *
   * <p>This method should return quickly, as the same thread may be used to process other streams.
   *
   * @param message the bytes of the message.
   * @param length the length of the message {@link InputStream}.
   * @return a processing completion future, or {@code null} to indicate that processing of the
   *         message is immediately complete.
   */
  @Nullable
  ListenableFuture<Void> messageRead(InputStream message, int length);
}