epoll函数

函数epoll

1. 函数epoll_creat: 该函数生成一个epoll专用的文件描述符

int epoll_creae(int size);

分析:

  • size:epoll上能关注的最大描述符数

2. epoll_ctl:用于控制某个epoll文件描述符事件,可以注册、修改、删除

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

参数:

1. efd:epoll_create函数的返回值

2. op:对该监听红黑树所做的操作

  • EPOLL_CTL_ADD:添加新的fd到epfd中
  • EPOLL_CTL_MOD:修改fd在监听红黑树的监听事件
  • EPOLL_CTL_DE:将一个fd从监听红黑树摘下

3. fd:待监听的fd

4. event:本质struct epoll_event 结构体地址

 typedef union epoll_data
{
void* ptr;
int fd; //对应监听的fd
uint32_t u32;
uint64_t u64;
} epoll_data_t; struct epoll_event
{
uint32_t events; /* epoll事件 */
epoll_data_t data; /* 用户数据 */
};

3. 等待IO事件发生 - 可以设置阻塞的函数

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

参数:

  • efds:epoll_create函数的返回值
  • events:传出参数【数组】满足监听条件的哪些fd结构体
  • maxevents:数组元素的总个数(1024) struct epoll_events [1024]:
  • timeout:
  • ET:边缘触发只有数据到来才触发,不管缓冲区是否还有数据(缓冲区剩余未读尽的数据的数据不会导致epoll_wait返回。新的时间满足,才会触发)
  • LT:水平触发 ---默认采用模式(缓冲区剩余未读尽的数据会导致epoll_wait返回。)

1. 测试代码:

 #include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h> #define MAXLINE 10 int main(int argc, char *argv[])
{
int efd, i;
int pfd[];
pid_t pid;
char buf[MAXLINE],ch = 'a';
pipe(pfd);
pid = fork(); if (pid == ) //子写
{
close(pfd[]); //关闭读
while ()
{
for (i = ; i < MAXLINE / ; i++) //aaaa\n
buf[i] = ch;
buf[i - ] = '\n';
ch++; for (; i < MACLINE; i++) //bbbb\n
buf[i] = ch;
buf[i - ] = '\n';
ch++; write(pdf[], buf, sizeof(buf)); //aaaa\nbbbb\n
sleep();
}
close(pfd[]);
}
else if (pid < ) //父进程读
{
struct epoll_event;
struct epoll_event resevent[];
int res, len; close(pfd[]); //关闭写
efd = epoll_create(); //event.events = EPOLLIN | EPOLLET // ET边沿触发
even.events = EPOLLIN; // LT水平触发(默认)
event.data.fd = pfd[];
epoll_ctl(efd, EPOLL_CTL_ADD, pfd[], &event); while ()
{
res = epoll_wait(efd, resevent, , -);
printf("res %d\n", res);
if (resevent[].data.fd == pfd[])
{
len = read(pfd[], buf, MACLINE/);
write(STDOUT_FILENO, buf, len);
}
}
close(pfd[pfd[]);
close(efd);
}
else
{
perror("fork");
exit(-);
}
return ;
}
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h> #define MAXLINE 10 int main(int argc, char *argv[])
{
int efd, i;
int pfd[];
pid_t pid;
char buf[MAXLINE],ch = 'a';
pipe(pfd);
pid = fork(); if (pid == ) //子写
{
close(pfd[]); //关闭读
while ()
{
for (i = ; i < MAXLINE / ; i++) //aaaa\n
buf[i] = ch;
buf[i - ] = '\n';
ch++; for (; i < MACLINE; i++) //bbbb\n
buf[i] = ch;
buf[i - ] = '\n';
ch++; write(pdf[], buf, sizeof(buf)); //aaaa\nbbbb\n
sleep();
}
close(pfd[]);
}
else if (pid < ) //父进程读
{
struct epoll_event;
struct epoll_event resevent[];
int res, len; close(pfd[]); //关闭写
efd = epoll_create(); //event.events = EPOLLIN | EPOLLET // ET边沿触发
even.events = EPOLLIN; // LT水平触发(默认)
event.data.fd = pfd[];
epoll_ctl(efd, EPOLL_CTL_ADD, pfd[], &event); while ()
{
res = epoll_wait(efd, resevent, , -);
printf("res %d\n", res);
if (resevent[].data.fd == pfd[])
{
len = read(pfd[], buf, MACLINE/);
write(STDOUT_FILENO, buf, len);
}
}
close(pfd[pfd[]);
close(efd);
}
else
{
perror("fork");
exit(-);
}
return ;
}
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