View Javadoc
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.PlatformDependent;
20  import io.netty.util.internal.SystemPropertyUtil;
21  import io.netty.util.internal.UnstableApi;
22  
23  /**
24   * If KQueue is available the JNI resources will be loaded when this class loads.
25   */
26  @UnstableApi
27  public final class KQueue {
28      private static final Throwable UNAVAILABILITY_CAUSE;
29      static  {
30          Throwable cause = null;
31          if (SystemPropertyUtil.getBoolean("io.netty.transport.noNative", false)) {
32              cause = new UnsupportedOperationException(
33                      "Native transport was explicit disabled with -Dio.netty.transport.noNative=true");
34          } else {
35              FileDescriptor kqueueFd = null;
36              try {
37                  kqueueFd = Native.newKQueue();
38              } catch (Throwable t) {
39                  cause = t;
40              } finally {
41                  if (kqueueFd != null) {
42                      try {
43                          kqueueFd.close();
44                      } catch (Exception ignore) {
45                          // ignore
46                      }
47                  }
48              }
49          }
50  
51          if (cause != null) {
52              UNAVAILABILITY_CAUSE = cause;
53          } else {
54              UNAVAILABILITY_CAUSE = PlatformDependent.hasUnsafe()
55                      ? null
56                      : new IllegalStateException(
57                              "sun.misc.Unsafe not available",
58                              PlatformDependent.getUnsafeUnavailabilityCause());
59          }
60      }
61  
62      /**
63       * Returns {@code true} if and only if the
64       * <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-kqueue}</a> is available.
65       */
66      public static boolean isAvailable() {
67          return UNAVAILABILITY_CAUSE == null;
68      }
69  
70      /**
71       * Ensure that <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-kqueue}</a> is
72       * available.
73       *
74       * @throws UnsatisfiedLinkError if unavailable
75       */
76      public static void ensureAvailability() {
77          if (UNAVAILABILITY_CAUSE != null) {
78              throw (Error) new UnsatisfiedLinkError(
79                      "failed to load the required native library").initCause(UNAVAILABILITY_CAUSE);
80          }
81      }
82  
83      /**
84       * Returns the cause of unavailability of
85       * <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-kqueue}</a>.
86       *
87       * @return the cause if unavailable. {@code null} if available.
88       */
89      public static Throwable unavailabilityCause() {
90          return UNAVAILABILITY_CAUSE;
91      }
92  
93      private KQueue() { }
94  }