Linux函数学习 epoll

1、Linux epoll函数

1.1、创建epoll实例

int epoll_create1(int flag);

返回值：-1 失败，非负数成功

flag ：默认传入0

1.2、管理epoll对象

int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);

epfd ：epoll 对象文件句柄

op ：epoll操作动作，添加，修改，删除

fd ：需要轮询的文件句柄

event ：需要监听的epoll事件

1.3、等待epoll事件

int epoll_wait(int epfd, struct epoll_event *events,
int maxevents, int timeout);

epfd ：epoll 对象文件句柄

events ：epoll事件上报

maxevents ：最大处理epoll事件数量

timeout ：超时时间

2、函数实例

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/input.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <string.h>

#define MAX_EVENT 1

static char * eventTypeToString(__u16 type){
	switch(type){
		case EV_SYN:
			return "EV_SYN";
		case EV_KEY:
			return "EV_KEY";
		case EV_REL:
			return "EV_REL";
		case EV_ABS:
			return "EV_ABS";
		case EV_MSC:
			return "EV_MSC";
		case EV_SW:
			return "EV_SW";
		default:
			return "UNKOWN";
	}
}

static char * eventCodeToString(__u16 code){
	switch(code){
		case KEY_ESC:
			return "KEY_ESC";
		case KEY_POWER:
			return "KEY_POWER";
		default:
			return "UNKOWN";
	}
}

int main (int argc, char ** argv){

	int fd; 
	int mEpollFd;
	int ret;

	struct input_event event;
	struct epoll_event ep_event;

	struct epoll_event pending_event[MAX_EVENT];

	if(argc != 2){
		printf("Usage: %s <dev> \n", argv[0]);
	}
	
	fd = open(argv[1], O_RDWR | O_NONBLOCK);
	if(fd < 0){
		printf("open %s err \n", argv[1]);
	} else {
		printf("open %s success \n",argv[1]);
	}

	/*创建EpollFd*/
	mEpollFd = epoll_create1(0);
	if(mEpollFd <0){
		printf("epoll create err = %s \n", strerror(errno));
	} else {
		printf("epoll create success \n");
	}

	/*添加监听*/
	ep_event.events = EPOLLIN;
    ep_event.data.fd = fd;
	ret = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, &ep_event);
	if(ret < 0){
		printf("epoll_ctl err = %s \n", strerror(errno));
	} else {
		printf("epoll_ctl success \n");
	}
	
	/*等待文件字符变化*/
	while(1){
		ret = epoll_wait(mEpollFd, pending_event, MAX_EVENT, 5);
		if(ret > 0){
			if(pending_event[0].data.fd == fd){
				if (pending_event[0].events & EPOLLIN) {
					while(read(fd, &event, sizeof(event)) == sizeof(event)){
						printf("epoll get event: type =0x%x, Code = 0x%x value = 0x%x \n",event.type, event.code, event.value);
						printf("epoll get event: type = %s, Code = %s value = 0x%x \n",eventTypeToString(event.type), eventCodeToString(event.code), event.value);
					}
				}
			}
		} else if (ret == 0){
			//printf("epoll_wait time out \n");
		} else {
			perror("epoll_wait error \n");
		}
	}

	return 0;
}