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1   /*
2    * Copyright 2016 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.channel.kqueue;
17  
18  import io.netty.channel.unix.FileDescriptor;
19  import io.netty.util.internal.SystemPropertyUtil;
20  import io.netty.util.internal.UnstableApi;
21  
22  /**
23   * If KQueue is available the JNI resources will be loaded when this class loads.
24   */
25  @UnstableApi
26  public final class KQueue {
27      private static final Throwable UNAVAILABILITY_CAUSE;
28      static  {
29          Throwable cause = null;
30          if (SystemPropertyUtil.getBoolean("io.netty.transport.noNative", false)) {
31              cause = new UnsupportedOperationException(
32                      "Native transport was explicit disabled with -Dio.netty.transport.noNative=true");
33          } else {
34              FileDescriptor kqueueFd = null;
35              try {
36                  kqueueFd = Native.newKQueue();
37              } catch (Throwable t) {
38                  cause = t;
39              } finally {
40                  if (kqueueFd != null) {
41                      try {
42                          kqueueFd.close();
43                      } catch (Exception ignore) {
44                          // ignore
45                      }
46                  }
47              }
48          }
49  
50          UNAVAILABILITY_CAUSE = cause;
51      }
52  
53      /**
54       * Returns {@code true} if and only if the
55       * <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-kqueue}</a> is available.
56       */
57      public static boolean isAvailable() {
58          return UNAVAILABILITY_CAUSE == null;
59      }
60  
61      /**
62       * Ensure that <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-kqueue}</a> is
63       * available.
64       *
65       * @throws UnsatisfiedLinkError if unavailable
66       */
67      public static void ensureAvailability() {
68          if (UNAVAILABILITY_CAUSE != null) {
69              throw (Error) new UnsatisfiedLinkError(
70                      "failed to load the required native library").initCause(UNAVAILABILITY_CAUSE);
71          }
72      }
73  
74      /**
75       * Returns the cause of unavailability of
76       * <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-kqueue}</a>.
77       *
78       * @return the cause if unavailable. {@code null} if available.
79       */
80      public static Throwable unavailabilityCause() {
81          return UNAVAILABILITY_CAUSE;
82      }
83  
84      private KQueue() { }
85  }