com.alibaba.rocketmq.shade.io.netty.channel.epoll.EpollEventArray Maven / Gradle / Ivy
/*
* Copyright 2015 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.channel.epoll;
import io.netty.util.internal.PlatformDependent;
/**
* This is an internal datastructure which can be directly passed to epoll_wait to reduce the overhead.
*
* typedef union epoll_data {
* void *ptr;
* int fd;
* uint32_t u32;
* uint64_t u64;
* } epoll_data_t;
*
* struct epoll_event {
* uint32_t events; // Epoll events
* epoll_data_t data; // User data variable
* };
*
* We use {@code fd} if the {@code epoll_data union} to store the actual file descriptor of an
* {@link AbstractEpollChannel} and so be able to map it later.
*/
final class EpollEventArray {
// Size of the epoll_event struct
private static final int EPOLL_EVENT_SIZE = Native.sizeofEpollEvent();
// The offsiet of the data union in the epoll_event struct
private static final int EPOLL_DATA_OFFSET = Native.offsetofEpollData();
private long memoryAddress;
private int length;
EpollEventArray(int length) {
if (length < 1) {
throw new IllegalArgumentException("length must be >= 1 but was " + length);
}
this.length = length;
memoryAddress = allocate(length);
}
private static long allocate(int length) {
return PlatformDependent.allocateMemory(length * EPOLL_EVENT_SIZE);
}
/**
* Return the {@code memoryAddress} which points to the start of this {@link EpollEventArray}.
*/
long memoryAddress() {
return memoryAddress;
}
/**
* Return the length of the {@link EpollEventArray} which represent the maximum number of {@code epoll_events}
* that can be stored in it.
*/
int length() {
return length;
}
/**
* Increase the storage of this {@link EpollEventArray}.
*/
void increase() {
// double the size
length <<= 1;
free();
memoryAddress = allocate(length);
}
/**
* Free this {@link EpollEventArray}. Any usage after calling this method may segfault the JVM!
*/
void free() {
PlatformDependent.freeMemory(memoryAddress);
}
/**
* Return the events for the {@code epoll_event} on this index.
*/
int events(int index) {
return PlatformDependent.getInt(memoryAddress + index * EPOLL_EVENT_SIZE);
}
/**
* Return the file descriptor for the {@code epoll_event} on this index.
*/
int fd(int index) {
return PlatformDependent.getInt(memoryAddress + index * EPOLL_EVENT_SIZE + EPOLL_DATA_OFFSET);
}
}