struct event_base *base;
base = event_base_new();//初始化libevent

struct event *listener_event;
listener_event = event_new(base,  listener, EV_READ|EV_PERSIST, do_accept, (void*)base);

struct event_base *  event_base_new(void)

struct event *  event_new(struct event_base *base, evutil_socket_t fd, short events, void (*cb)(evutil_socket_t, short, void *), void *arg)

int  event_add(struct event *ev, const struct timeval *tv)

int  event_base_dispatch(struct event_base *event_base)

struct fd_state {char buffer[MAX_LINE];//缓冲区的大小size_t buffer_used;//接收到已经使用的buffer大小，每次将接收到的数据字节数相加，当发送的字节数累计相加和buffer_used都相等时候，将它们都置为1size_t n_written;//发送的累加字节数size_t write_upto;//相当于一个临时变量，当遇到换行符的时，将其收到的字节数（换行符除外）赋给该值，当检测到写事件的时候，用已经发送的字节数和该数值做比较，若收到的字节总数小于该值，则发送数据，等于该值，将结构体中3个字节数统计变量都置为1，为什么会置为1呢，因为有一个换行符吧。struct event *read_event;struct event *write_event;
};

//说明，为了使我们的代码兼容win32网络API，我们使用evutil_socket_t代替int，使用evutil_make_socket_nonblocking代替fcntl/* For sockaddr_in */
#include <netinet/in.h>
/* For socket functions */
#include <sys/socket.h>
/* For fcntl */
#include <fcntl.h>#include <event2/event.h>#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>#define MAX_LINE 80void do_read(evutil_socket_t fd, short events, void *arg);
void do_write(evutil_socket_t fd, short events, void *arg);char rot13_char(char c)
{/* We don't want to use isalpha here; setting the locale would change* which characters are considered alphabetical. */if ((c >= 'a' && c <= 'm') || (c >= 'A' && c <= 'M'))return c + 13;else if ((c >= 'n' && c <= 'z') || (c >= 'N' && c <= 'Z'))return c - 13;elsereturn c;
}struct fd_state {char buffer[MAX_LINE];size_t buffer_used;size_t n_written;size_t write_upto;struct event *read_event;struct event *write_event;
};struct fd_state * alloc_fd_state(struct event_base *base, evutil_socket_t fd)
{struct fd_state *state = malloc(sizeof(struct fd_state));if (!state)return NULL;state->read_event = event_new(base, fd, EV_READ|EV_PERSIST, do_read, state);if (!state->read_event){free(state);return NULL;}state->write_event = event_new(base, fd, EV_WRITE|EV_PERSIST, do_write, state);if (!state->write_event){event_free(state->read_event);free(state);return NULL;}state->buffer_used = state->n_written = state->write_upto = 0;assert(state->write_event);return state;
}void free_fd_state(struct fd_state *state)
{event_free(state->read_event);event_free(state->write_event);free(state);
}void do_read(evutil_socket_t fd, short events, void *arg)
{struct fd_state *state = arg;char buf[20];int i;ssize_t result;printf("ncome in do_read: fd: %d, state->buffer_used: %d, sizeof(state->buffer): %dn", fd, state->buffer_used, size
of(state->buffer));while (1){assert(state->write_event);result = recv(fd, buf, sizeof(buf), 0);if (result <= 0)break;printf("recv once, fd: %d, recv size: %d, recv buff: %sn", fd, result, buf);for (i=0; i < result; ++i){if (state->buffer_used < sizeof(state->buffer))//如果读事件的缓冲区还未满，将收到的数据做转换state->buffer[state->buffer_used++] = rot13_char(buf[i]);
//              state->buffer[state->buffer_used++] = buf[i];//接收什么发送什么，不经过转换，测试用if (buf[i] == 'n') //如果遇到换行，添加写事件，并设置写事件的大小{assert(state->write_event);event_add(state->write_event, NULL);state->write_upto = state->buffer_used;printf("遇到换行符，state->write_upto: %d, state->buffer_used: %dn",state->write_upto, state->buffer_use
d);}}printf("recv once, state->buffer_used: %dn", state->buffer_used);
}//判断最后一次接收的字节数if (result == 0){free_fd_state(state);}else if (result < 0){if (errno == EAGAIN) // XXXX use evutil macroreturn;perror("recv");free_fd_state(state);}
}void do_write(evutil_socket_t fd, short events, void *arg)
{struct fd_state *state = arg;printf("ncome in do_write, fd: %d, state->n_written: %d, state->write_upto: %dn",fd, state->n_written, state->write
_upto);while (state->n_written < state->write_upto){ssize_t result = send(fd, state->buffer + state->n_written, state->write_upto - state->n_written, 0);if (result < 0) {if (errno == EAGAIN) // XXX use evutil macroreturn;free_fd_state(state);return;}assert(result != 0);state->n_written += result;printf("send fd: %d, send size: %d, state->n_written: %dn", fd, result, state->n_written);}if (state->n_written == state->buffer_used){printf("state->n_written == state->buffer_used: %dn", state->n_written);state->n_written = state->write_upto = state->buffer_used = 1;printf("state->n_written = state->write_upto = state->buffer_used = 1n");}event_del(state->write_event);
}void do_accept(evutil_socket_t listener, short event, void *arg)
{struct event_base *base = arg;struct sockaddr_storage ss;socklen_t slen = sizeof(ss);int fd = accept(listener, (struct sockaddr*)&ss, &slen);if (fd < 0){ // XXXX eagain??perror("accept");}else if (fd > FD_SETSIZE){close(fd); // XXX replace all closes with EVUTIL_CLOSESOCKET */}else{struct fd_state *state;evutil_make_socket_nonblocking(fd);state = alloc_fd_state(base, fd);assert(state); /*XXX err*/assert(state->write_event);event_add(state->read_event, NULL);}
}void run(void)
{evutil_socket_t listener;struct sockaddr_in sin;struct event_base *base;struct event *listener_event;base = event_base_new();//初始化libeventif (!base)return; /*XXXerr*/sin.sin_family = AF_INET;sin.sin_addr.s_addr = 0;//本机sin.sin_port = htons(8000);listener = socket(AF_INET, SOCK_STREAM, 0);evutil_make_socket_nonblocking(listener);#ifndef WIN32{int one = 1;setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));}
#endifif (bind(listener, (struct sockaddr*)&sin, sizeof(sin)) < 0){perror("bind");return;}if (listen(listener, 16)<0){perror("listen");return;}listener_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);/*XXX check it */event_add(listener_event, NULL);event_base_dispatch(base);}int main(int c, char **v){//    setvbuf(stdout, NULL, _IONBF, 0);run();return 0;}