libevent

http://senlinzhan.github.io/2017/08/20/libevent-buffer/

#include <event2/listener.h>
#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <arpa/inet.h>
#include <string.h>
#include <iostream>
void echo_read_cb(struct bufferevent *bev, void *ctx)
{
    struct evbuffer *input = bufferevent_get_input(bev);   // 输入缓存区
    struct evbuffer *output = bufferevent_get_output(bev); // 输出缓存区
    // 将输入缓冲区的数据移动到输出缓冲区
    evbuffer_add_buffer(output, input);
}
void echo_event_cb(struct bufferevent *bev, short events, void *ctx)
{
    if (events & BEV_EVENT_ERROR)
    {
        int err = EVUTIL_SOCKET_ERROR();
        std::cerr << "Got an error from bufferevent: "
                  << evutil_socket_error_to_string(err)
                  << std::endl;
    }
    if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR))
    {
        bufferevent_free(bev);
    }
}
void accept_conn_cb(struct evconnlistener *listener, evutil_socket_t fd,
                    struct sockaddr *address, int socklen, void *arg)
{
    // 设置 socket 为非阻塞
    evutil_make_socket_nonblocking(fd);
    auto *base = evconnlistener_get_base(listener);
    auto *b = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
    bufferevent_setcb(b, echo_read_cb, nullptr, echo_event_cb, nullptr);
    bufferevent_enable(b, EV_READ|EV_WRITE);
}
int main()
{
    short port = 8000;
    struct sockaddr_in sin;
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = htonl(INADDR_ANY);
    sin.sin_port = htons(port);
    auto *base = event_base_new();
    auto *listener = evconnlistener_new_bind(
        base, accept_conn_cb, nullptr,
        LEV_OPT_CLOSE_ON_FREE|LEV_OPT_REUSEABLE, -1,
        reinterpret_cast<struct sockaddr *>(&sin), sizeof(sin));
    if (listener == nullptr)
    {
        std::cerr << "Couldn't create listener" << std::endl;
        return 1;
    }
    event_base_dispatch(base);
    return 0;
}