1 /*
   2  * Copyright (c) 2002, 2012, 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 sun.nio.ch;
  27 
  28 
  29 // Special-purpose data structure for sets of native threads
  30 
  31 
  32 class NativeThreadSet {
  33 
  34     private long[] elts;
  35     private int used = 0;
  36     private boolean waitingToEmpty;
  37 
  38     NativeThreadSet(int n) {
  39         elts = new long[n];
  40     }
  41 
  42     // Adds the current native thread to this set, returning its index so that
  43     // it can efficiently be removed later.
  44     //
  45     int add() {
  46         long th = NativeThread.current();
  47         // 0 and -1 are treated as placeholders, not real thread handles
  48         if (th == 0)
  49             th = -1;
  50         synchronized (this) {
  51             int start = 0;
  52             if (used >= elts.length) {
  53                 int on = elts.length;
  54                 int nn = on * 2;
  55                 long[] nelts = new long[nn];
  56                 System.arraycopy(elts, 0, nelts, 0, on);
  57                 elts = nelts;
  58                 start = on;
  59             }
  60             for (int i = start; i < elts.length; i++) {
  61                 if (elts[i] == 0) {
  62                     elts[i] = th;
  63                     used++;
  64                     return i;
  65                 }
  66             }
  67             assert false;
  68             return -1;
  69         }
  70     }
  71 
  72     // Removes the thread at the given index.
  73     //
  74     void remove(int i) {
  75         synchronized (this) {
  76             elts[i] = 0;
  77             used--;
  78             if (used == 0 && waitingToEmpty)
  79                 notifyAll();
  80         }
  81     }
  82 
  83     // Signals all threads in this set.
  84     //
  85     synchronized void signalAndWait() {
  86         boolean interrupted = false;
  87         while (used > 0) {
  88             int u = used;
  89             int n = elts.length;
  90             for (int i = 0; i < n; i++) {
  91                 long th = elts[i];
  92                 if (th == 0)
  93                     continue;
  94                 if (th != -1)
  95                     NativeThread.signal(th);
  96                 if (--u == 0)
  97                     break;
  98             }
  99             waitingToEmpty = true;
 100             try {
 101                 wait(50);
 102             } catch (InterruptedException e) {
 103                 interrupted = true;
 104             } finally {
 105                 waitingToEmpty = false;
 106             }
 107         }
 108         if (interrupted)
 109             Thread.currentThread().interrupt();
 110     }
 111 }