1 /* 2 * Copyright (c) 2015, 2017, 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.internal.websocket; 27 28 import java.io.IOException; 29 import java.nio.channels.SelectionKey; 30 import java.util.concurrent.atomic.AtomicBoolean; 31 import java.util.function.Consumer; 32 33 import static java.util.Objects.requireNonNull; 34 35 /* 36 * Sends messages one at a time, in an asynchronous and non-blocking fashion. 37 * 38 * No matter whether the message has been fully sent or an error has occurred, 39 * the transmitter reports the outcome to the supplied handler and becomes ready 40 * to accept a new message. Until then, the transmitter is considered "busy" and 41 * an IllegalStateException will be thrown on each attempt to invoke send. 42 */ 43 public class Transmitter { 44 45 /* This flag is used solely for assertions */ 46 private final AtomicBoolean busy = new AtomicBoolean(); 47 private OutgoingMessage message; 48 private Consumer<Exception> completionHandler; 49 private final RawChannel channel; 50 private final RawChannel.RawEvent event; 51 52 public Transmitter(RawChannel channel) { 53 this.channel = channel; 54 this.event = createHandler(); 55 } 56 57 /** 58 * The supplied handler may be invoked in the calling thread. 59 * A {@code StackOverflowError} may thus occur if there's a possibility 60 * that this method is called again by the supplied handler. 61 */ 62 public void send(OutgoingMessage message, 63 Consumer<Exception> completionHandler) 64 { 65 requireNonNull(message); 66 requireNonNull(completionHandler); 67 if (!busy.compareAndSet(false, true)) { 68 throw new IllegalStateException(); 69 } 70 send0(message, completionHandler); 71 } 72 73 public void close() throws IOException { 74 channel.shutdownOutput(); 75 } 76 77 private RawChannel.RawEvent createHandler() { 78 return new RawChannel.RawEvent() { 79 80 @Override 81 public int interestOps() { 82 return SelectionKey.OP_WRITE; 83 } 84 85 @Override 86 public void handle() { 87 // registerEvent(e) happens-before subsequent e.handle(), so 88 // we're fine reading the stored message and the completionHandler 89 send0(message, completionHandler); 90 } 91 }; 92 } 93 94 private void send0(OutgoingMessage message, Consumer<Exception> handler) { 95 boolean b = busy.get(); 96 assert b; // Please don't inline this, as busy.get() has memory 97 // visibility effects and we don't want the program behaviour 98 // to depend on whether the assertions are turned on 99 // or turned off 100 try { 101 boolean sent = message.sendTo(channel); 102 if (sent) { 103 busy.set(false); 104 handler.accept(null); 105 } else { 106 // The message has not been fully sent, the transmitter needs to 107 // remember the message until it can continue with sending it 108 this.message = message; 109 this.completionHandler = handler; 110 try { 111 channel.registerEvent(event); 112 } catch (IOException e) { 113 this.message = null; 114 this.completionHandler = null; 115 busy.set(false); 116 handler.accept(e); 117 } 118 } 119 } catch (IOException e) { 120 busy.set(false); 121 handler.accept(e); 122 } 123 } 124 }