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
26package jdk.incubator.http;
27
28import java.util.Iterator;
29import java.util.concurrent.Flow;
30
31/**
32 * A Publisher that is expected to run in same thread as subscriber.
33 * Items are obtained from Iterable. Each new subscription gets a new Iterator.
34 */
35class PullPublisher<T> implements Flow.Publisher<T> {
36
37    private final Iterable<T> iterable;
38
39    PullPublisher(Iterable<T> iterable) {
40        this.iterable = iterable;
41    }
42
43    @Override
44    public void subscribe(Flow.Subscriber<? super T> subscriber) {
45        subscriber.onSubscribe(new Subscription(subscriber, iterable.iterator()));
46    }
47
48    private class Subscription implements Flow.Subscription {
49
50        private final Flow.Subscriber<? super T> subscriber;
51        private final Iterator<T> iter;
52        private boolean done = false;
53        private long demand = 0;
54        private int recursion = 0;
55
56        Subscription(Flow.Subscriber<? super T> subscriber, Iterator<T> iter) {
57            this.subscriber = subscriber;
58            this.iter = iter;
59        }
60
61        @Override
62        public void request(long n) {
63            if (done) {
64                subscriber.onError(new IllegalArgumentException("request(" + n + ")"));
65            }
66            demand += n;
67            recursion ++;
68            if (recursion > 1) {
69                return;
70            }
71            while (demand > 0) {
72                done = !iter.hasNext();
73                if (done) {
74                    subscriber.onComplete();
75                    recursion --;
76                    return;
77                }
78                subscriber.onNext(iter.next());
79                demand --;
80            }
81        }
82
83        @Override
84        public void cancel() {
85            done = true;
86        }
87
88    }
89}
90