1 /*
2 * Copyright 2014 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.epoll;
17
18 import io.netty.channel.unix.FileDescriptor;
19 import io.netty.util.internal.PlatformDependent;
20
21 /**
22 * Tells if <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a> is supported.
23 */
24 public final class Epoll {
25
26 private static final Throwable UNAVAILABILITY_CAUSE;
27
28 static {
29 Throwable cause = null;
30 FileDescriptor epollFd = null;
31 FileDescriptor eventFd = null;
32 try {
33 epollFd = Native.newEpollCreate();
34 eventFd = Native.newEventFd();
35 } catch (Throwable t) {
36 cause = t;
37 } finally {
38 if (epollFd != null) {
39 try {
40 epollFd.close();
41 } catch (Exception ignore) {
42 // ignore
43 }
44 }
45 if (eventFd != null) {
46 try {
47 eventFd.close();
48 } catch (Exception ignore) {
49 // ignore
50 }
51 }
52 }
53
54 if (cause != null) {
55 UNAVAILABILITY_CAUSE = cause;
56 } else {
57 UNAVAILABILITY_CAUSE = PlatformDependent.hasUnsafe()
58 ? null
59 : new IllegalStateException(
60 "sun.misc.Unsafe not available",
61 PlatformDependent.getUnsafeUnavailabilityCause());
62 }
63 }
64
65 /**
66 * Returns {@code true} if and only if the
67 * <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a> is available.
68 */
69 public static boolean isAvailable() {
70 return UNAVAILABILITY_CAUSE == null;
71 }
72
73 /**
74 * Ensure that <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a> is
75 * available.
76 *
77 * @throws UnsatisfiedLinkError if unavailable
78 */
79 public static void ensureAvailability() {
80 if (UNAVAILABILITY_CAUSE != null) {
81 throw (Error) new UnsatisfiedLinkError(
82 "failed to load the required native library").initCause(UNAVAILABILITY_CAUSE);
83 }
84 }
85
86 /**
87 * Returns the cause of unavailability of
88 * <a href="http://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a>.
89 *
90 * @return the cause if unavailable. {@code null} if available.
91 */
92 public static Throwable unavailabilityCause() {
93 return UNAVAILABILITY_CAUSE;
94 }
95
96 private Epoll() { }
97 }