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      1 /*
      2  * Copyright (c) 2002, 2009, 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     void signalAndWait() {
     86         synchronized (this) {
     87             int u = used;
     88             int n = elts.length;
     89             for (int i = 0; i < n; i++) {
     90                 long th = elts[i];
     91                 if (th == 0)
     92                     continue;
     93                 if (th != -1)
     94                     NativeThread.signal(th);
     95                 if (--u == 0)
     96                     break;
     97             }
     98             waitingToEmpty = true;
     99             boolean interrupted = false;
    100             while (used > 0) {
    101                 try {
    102                     wait();
    103                 } catch (InterruptedException e) {
    104                     interrupted = true;
    105                 }
    106             }
    107             if (interrupted)
    108                 Thread.currentThread().interrupt();
    109         }
    110     }
    111 }
    112