1 /*
   2  * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.incubator.http;
  27 
  28 import jdk.incubator.http.internal.common.ByteBufferReference;
  29 
  30 import java.io.IOException;
  31 import java.nio.ByteBuffer;
  32 import java.util.function.Consumer;
  33 import java.util.function.Supplier;
  34 
  35 /**
  36  * Implemented by classes that offer an asynchronous interface.
  37  *
  38  * PlainHttpConnection, AsyncSSLConnection AsyncSSLDelegate.
  39  *
  40  * setAsyncCallbacks() is called to set the callback for reading
  41  * and error notification. Reads all happen on the selector thread, which
  42  * must not block.
  43  *
  44  * Writing uses the same write() methods as used in blocking mode.
  45  * Queues are employed on the writing side to buffer data while it is waiting
  46  * to be sent. This strategy relies on HTTP/2 protocol flow control to stop
  47  * outgoing queue from continually growing. Writes can be initiated by the
  48  * calling thread, but if socket becomes full then the queue is emptied by
  49  * the selector thread
  50  */
  51 interface AsyncConnection {
  52 
  53     /**
  54      * Enables asynchronous sending and receiving mode. The given async
  55      * receiver will receive all incoming data. asyncInput() will be called
  56      * to trigger reads. asyncOutput() will be called to drive writes.
  57      *
  58      * The errorReceiver callback must be called when any fatal exception
  59      * occurs. Connection is assumed to be closed afterwards.
  60      */
  61     void setAsyncCallbacks(Consumer<ByteBufferReference> asyncReceiver,
  62                            Consumer<Throwable> errorReceiver,
  63                            Supplier<ByteBufferReference> readBufferSupplier);
  64 
  65 
  66 
  67     /**
  68      * Does whatever is required to start reading. Usually registers
  69      * an event with the selector thread.
  70      */
  71     void startReading();
  72 
  73     /**
  74      * Cancel asynchronous reading. Used to downgrade a HTTP/2 connection to HTTP/1
  75      */
  76     void stopAsyncReading();
  77 
  78     /**
  79      * In async mode, this method puts buffers at the end of the send queue.
  80      * When in async mode, calling this method should later be followed by
  81      * subsequent flushAsync invocation.
  82      * That allows multiple threads to put buffers into the queue while some other
  83      * thread is writing.
  84      */
  85     void writeAsync(ByteBufferReference[] buffers) throws IOException;
  86 
  87     /**
  88      * Re-enable asynchronous reads through the callback
  89      */
  90     void enableCallback();
  91 
  92     /**
  93      * In async mode, this method may put buffers at the beginning of send queue,
  94      * breaking frames sequence and allowing to write these buffers before other
  95      * buffers in the queue.
  96      * When in async mode, calling this method should later be followed by
  97      * subsequent flushAsync invocation.
  98      * That allows multiple threads to put buffers into the queue while some other
  99      * thread is writing.
 100      */
 101     void writeAsyncUnordered(ByteBufferReference[] buffers) throws IOException;
 102 
 103     /**
 104      * This method should be called after any writeAsync/writeAsyncUnordered
 105      * invocation.
 106      * If there is a race to flushAsync from several threads one thread
 107      * (race winner) capture flush operation and write the whole queue content.
 108      * Other threads (race losers) exits from the method (not blocking)
 109      * and continue execution.
 110      */
 111     void flushAsync() throws IOException;
 112 }