/*
* Compile with:
* cc -I/usr/local/include -o event-test event-test.c -L/usr/local/lib -levent
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/queue.h>
#include <unistd.h>
#include <sys/time.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <event.h>
void fifo_read(int fd, short event, void *arg)
{
char buf[255];
int len;
struct event *ev = arg;
static int count = 0;
fprintf(stderr, "fifo_read called with fd: %d, event: %d, arg: %p\n",
fd, event, arg);
if (++count == 20){
len = read(fd, buf, sizeof(buf) - 1);
if (len == -1) {
perror("read");
return;
} else if (len == 0) {
fprintf(stderr, "Connection closed\n");
return;
}
buf[len] = '\0';
fprintf(stdout, "Read: %s\n", buf);
}
printf("over...\n");
}
int main (int argc, char **argv)
{
struct event evfifo;
struct stat st;
char *fifo = "event.fifo";
int socket;
if (lstat (fifo, &st) == 0) {
if (S_ISREG(st.st_mode)){
errno = EEXIST;
perror("lstat");
exit (1);
}
}
unlink (fifo);
if (mkfifo (fifo, 0600) == -1) {
perror("mkfifo");
exit (1);
}
/* Linux pipes are broken, we need O_RDWR instead of O_RDONLY */
socket = open (fifo, O_RDWR | O_NONBLOCK, 0);
if (socket == -1) {
perror("open");
exit (1);
}
fprintf(stderr, "Write data to %s\n", fifo);
/* Initalize the event library */
event_init();
/* Initalize one event */
event_set(&evfifo, socket, EV_READ | EV_PERSIST, fifo_read, &evfifo);
/* Add it to the active events, without a timeout */
event_add(&evfifo, NULL);
event_dispatch();
return (0);
}
//设置持久事件后，只要用echo "a">event.fifo 哪怕只写入一个Byte, 程序也会进入读事件循环，直到数据被读出！所以这个测试程序可以会一致打印20个over后再停止。memcached的状态机（drive_machine）就是利用这个EV_PERSIST来实现的。
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