1 /* 2 * Copyright (c) 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 java.util.Optional; 29 import java.util.concurrent.Flow; 30 import jdk.incubator.http.internal.common.Log; 31 32 /** 33 * A Publisher which is assumed to run in its own thread. 34 * 35 * acceptData() may therefore block while waiting for subscriber demand 36 */ 37 class BlockingPushPublisher<T> extends AbstractPushPublisher<T> { 38 volatile Subscription subscription; 39 volatile Flow.Subscriber<? super T> subscriber; 40 volatile SubscriptionState state; 41 long demand; 42 43 @Override 44 public void subscribe(Flow.Subscriber<? super T> subscriber) { 45 state = SubscriptionState.OPENED; 46 subscription = new Subscription(subscriber); 47 subscriber.onSubscribe(subscription); 48 } 49 50 /** 51 * Entry point for supplying items to publisher. This call will block 52 * when no demand available. 53 */ 54 @Override 55 public void acceptData(Optional<T> item) throws InterruptedException { 56 SubscriptionState s = this.state; 57 58 // do not use switch(this.state): this.state could be null. 59 if (s == SubscriptionState.CANCELLED) return; 60 if (s == SubscriptionState.DONE) { 61 throw new IllegalStateException("subscription complete"); 62 } 63 64 if (!item.isPresent()) { 65 subscriber.onComplete(); 66 this.state = SubscriptionState.DONE; 67 } else { 68 obtainPermit(); 69 if (this.state == SubscriptionState.CANCELLED) return; 70 subscriber.onNext(item.get()); 71 } 72 } 73 74 /** 75 * Terminates the publisher with given exception. 76 */ 77 @Override 78 public void acceptError(Throwable t) { 79 if (this.state != SubscriptionState.OPENED) { 80 Log.logError(t); 81 return; 82 } 83 subscriber.onError(t); 84 cancel(); 85 } 86 87 private synchronized void obtainPermit() throws InterruptedException { 88 while (demand == 0) { 89 wait(); 90 } 91 if (this.state == SubscriptionState.DONE) { 92 throw new IllegalStateException("subscription complete"); 93 } 94 demand --; 95 } 96 97 synchronized void addPermits(long n) { 98 long old = demand; 99 demand += n; 100 if (old == 0) { 101 notifyAll(); 102 } 103 } 104 105 synchronized void cancel() { 106 this.state = SubscriptionState.CANCELLED; 107 notifyAll(); 108 } 109 110 private class Subscription implements Flow.Subscription { 111 112 Subscription(Flow.Subscriber<? super T> subscriber) { 113 BlockingPushPublisher.this.subscriber = subscriber; 114 } 115 116 @Override 117 public void request(long n) { 118 addPermits(n); 119 } 120 121 @Override 122 public void cancel() { 123 BlockingPushPublisher.this.cancel(); 124 } 125 } 126 }