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  */
  24 
  25 package java.net.http;
  26 
  27 import java.io.Closeable;
  28 import java.io.IOException;
  29 import java.util.LinkedList;
  30 
  31 // Each stream has one of these for input. Each Http2Connection has one
  32 // for output. Can be used blocking or asynchronously.
  33 
  34 class Queue<T> implements Closeable {
  35 
  36     LinkedList<T> q = new LinkedList<>();
  37     volatile boolean closed = false;
  38     Runnable callback;
  39     boolean forceCallback;
  40     int waiters; // true if someone waiting
  41 
  42     synchronized void putAll(T[] objs) throws IOException {
  43         if (closed) {
  44             throw new IOException("stream closed");
  45         }
  46         boolean wasEmpty = q.isEmpty();
  47 
  48         for (T obj : objs) {
  49             q.add(obj);
  50         }
  51 
  52         if (waiters > 0)
  53             notifyAll();
  54 
  55         if (wasEmpty || forceCallback) {
  56             forceCallback = false;
  57             if (callback != null) {
  58                 callback.run();
  59                 return;
  60             }
  61         }
  62     }
  63 
  64     synchronized int size() {
  65         return q.size();
  66     }
  67 
  68     synchronized void put(T obj) throws IOException {
  69         if (closed) {
  70             throw new IOException("stream closed");
  71         }
  72 
  73         q.add(obj);
  74         if (waiters > 0)
  75             notifyAll();
  76 
  77         if (q.size() == 1 || forceCallback) {
  78             forceCallback = false;
  79             if (callback != null) {
  80                 callback.run();
  81                 return;
  82             }
  83         }
  84     }
  85 
  86     /**
  87      * callback is invoked any time put is called where
  88      * the Queue was empty.
  89      *
  90      * @param callback
  91      */
  92     synchronized void registerPutCallback(Runnable callback) {
  93         this.callback = callback;
  94         if (callback != null && q.size() > 0)
  95             callback.run();
  96     }
  97 
  98     @Override
  99     public synchronized void close() {
 100         closed = true;
 101         notifyAll();
 102     }
 103 
 104     synchronized T take() throws IOException {
 105         if (closed) {
 106             throw new IOException("stream closed");
 107         }
 108         try {
 109             while (q.size() == 0) {
 110                 waiters++;
 111                 wait();
 112                 waiters--;
 113             }
 114             T res = q.removeFirst();
 115             return res;
 116         } catch (InterruptedException ex) {
 117             throw new IOException(ex);
 118         }
 119     }
 120 
 121     public synchronized T poll() throws IOException {
 122         if (closed)
 123             throw new IOException("stream closed");
 124 
 125         if (q.isEmpty())
 126             return null;
 127         T res = q.removeFirst();
 128         return res;
 129     }
 130 
 131     public synchronized T[] pollAll(T[] type) throws IOException {
 132         T[] ret = q.toArray(type);
 133         q.clear();
 134         return ret;
 135     }
 136 
 137     public synchronized void pushback(T v) {
 138         forceCallback = true;
 139         q.addFirst(v);
 140     }
 141 
 142     public synchronized void pushbackAll(T[] v) {
 143         forceCallback = true;
 144         for (int i=v.length-1; i>=0; i--) {
 145             q.addFirst(v[i]);
 146         }
 147     }
 148 }