1 /*

     2  * Copyright (c) 2017, 2018, 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.internal.net.http.common;

    27 

    28 import java.util.concurrent.Flow;

    29 import java.util.concurrent.atomic.AtomicBoolean;

    30 import java.util.function.Consumer;

    31 

    32 /**

    33  * Maintains subscription counter and provides primitives for:

    34  * - accessing window

    35  * - reducing window when delivering items externally

    36  * - resume delivery when window was zero previously

    37  */

    38 public class SubscriptionBase implements Flow.Subscription {

    39 

    40     final Demand demand = new Demand();

    41 

    42     final SequentialScheduler scheduler; // when window was zero and is opened, run this

    43     final Runnable cancelAction; // when subscription cancelled, run this

    44     final AtomicBoolean cancelled;

    45     final Consumer<Throwable> onError;

    46 

    47     public SubscriptionBase(SequentialScheduler scheduler, Runnable cancelAction) {

    48         this(scheduler, cancelAction, null);

    49     }

    50 

    51     public SubscriptionBase(SequentialScheduler scheduler,

    52                             Runnable cancelAction,

    53                             Consumer<Throwable> onError) {

    54         this.scheduler = scheduler;

    55         this.cancelAction = cancelAction;

    56         this.cancelled = new AtomicBoolean(false);

    57         this.onError = onError;

    58     }

    59 

    60     @Override

    61     public void request(long n) {

    62         try {

    63             if (demand.increase(n))

    64                 scheduler.runOrSchedule();

    65         } catch(Throwable t) {

    66             if (onError != null) {

    67                 if (cancelled.getAndSet(true))

    68                     return;

    69                 onError.accept(t);

    70             } else throw t;

    71         }

    72     }

    73 

    74     @Override

    75     public synchronized String toString() {

    76         return "SubscriptionBase: window = " + demand.get() +

    77                 " cancelled = " + cancelled.toString();

    78     }

    79 

    80     /**

    81      * Returns true if the window was reduced by 1. In that case

    82      * items must be supplied to subscribers and the scheduler run

    83      * externally. If the window could not be reduced by 1, then false

    84      * is returned and the scheduler will run later when the window is updated.

    85      */

    86     public boolean tryDecrement() {

    87         return demand.tryDecrement();

    88     }

    89 

    90     public long window() {

    91         return demand.get();

    92     }

    93 

    94     @Override

    95     public void cancel() {

    96         if (cancelled.getAndSet(true))

    97             return;

    98         scheduler.stop();

    99         cancelAction.run();

   100     }

   101 }