1 /*
2 * Copyright 2015 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.util.internal.PlatformDependent;
19
20 /**
21 * This is an internal datastructure which can be directly passed to epoll_wait to reduce the overhead.
22 *
23 * typedef union epoll_data {
24 * void *ptr;
25 * int fd;
26 * uint32_t u32;
27 * uint64_t u64;
28 * } epoll_data_t;
29 *
30 * struct epoll_event {
31 * uint32_t events; // Epoll events
32 * epoll_data_t data; // User data variable
33 * };
34 *
35 * We use {@code fd} if the {@code epoll_data union} to store the actual file descriptor of an
36 * {@link AbstractEpollChannel} and so be able to map it later.
37 */
38 final class EpollEventArray {
39 // Size of the epoll_event struct
40 private static final int EPOLL_EVENT_SIZE = Native.sizeofEpollEvent();
41 // The offsiet of the data union in the epoll_event struct
42 private static final int EPOLL_DATA_OFFSET = Native.offsetofEpollData();
43
44 private long memoryAddress;
45 private int length;
46
47 EpollEventArray(int length) {
48 if (length < 1) {
49 throw new IllegalArgumentException("length must be >= 1 but was " + length);
50 }
51 this.length = length;
52 memoryAddress = allocate(length);
53 }
54
55 private static long allocate(int length) {
56 return PlatformDependent.allocateMemory(length * EPOLL_EVENT_SIZE);
57 }
58
59 /**
60 * Return the {@code memoryAddress} which points to the start of this {@link EpollEventArray}.
61 */
62 long memoryAddress() {
63 return memoryAddress;
64 }
65
66 /**
67 * Return the length of the {@link EpollEventArray} which represent the maximum number of {@code epoll_events}
68 * that can be stored in it.
69 */
70 int length() {
71 return length;
72 }
73
74 /**
75 * Increase the storage of this {@link EpollEventArray}.
76 */
77 void increase() {
78 // double the size
79 length <<= 1;
80 free();
81 memoryAddress = allocate(length);
82 }
83
84 /**
85 * Free this {@link EpollEventArray}. Any usage after calling this method may segfault the JVM!
86 */
87 void free() {
88 PlatformDependent.freeMemory(memoryAddress);
89 }
90
91 /**
92 * Return the events for the {@code epoll_event} on this index.
93 */
94 int events(int index) {
95 return PlatformDependent.getInt(memoryAddress + index * EPOLL_EVENT_SIZE);
96 }
97
98 /**
99 * Return the file descriptor for the {@code epoll_event} on this index.
100 */
101 int fd(int index) {
102 return PlatformDependent.getInt(memoryAddress + index * EPOLL_EVENT_SIZE + EPOLL_DATA_OFFSET);
103 }
104 }