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//libevent的http服务器简单实现方式
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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//for struct evkeyvalq
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#include <sys/queue.h>
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#include <event.h>
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#include <event2/http.h>
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#include <event2/http_struct.h>
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#include <event2/http_compat.h>
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#include <event2/util.h>
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#include <signal.h>
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#define LOG_INFO    printf
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#define LOG_DBG    printf
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#define LOG_ERR    printf
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#define MYHTTPD_SIGNATURE   "httpd v 0.0.1"
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//处理模块
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void httpd_handler(struct evhttp_request *req, void *arg) {
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    char output[2048] = "\0";
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    char tmp[1024];
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    //获取客户端请求的URI(使用evhttp_request_uri或直接req->uri)
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    const char *uri;
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    uri = evhttp_request_uri(req);
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    sprintf(tmp, "uri=%s\n", uri);
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    strcat(output, tmp);
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    sprintf(tmp, "uri=%s\n", req->uri);
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    strcat(output, tmp);
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    //decoded uri
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    char *decoded_uri;
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    decoded_uri = evhttp_decode_uri(uri);
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    sprintf(tmp, "decoded_uri=%s\n", decoded_uri);
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    strcat(output, tmp);
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    //解析URI的参数(即GET方法的参数)
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    struct evkeyvalq params;
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    //将URL数据封装成key-value格式,q=value1, s=value2
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    evhttp_parse_query(decoded_uri, &params);
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    //得到q所对应的value
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    sprintf(tmp, "q=%s\n", evhttp_find_header(&params, "q"));
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    strcat(output, tmp);
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    //得到s所对应的value
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    sprintf(tmp, "s=%s\n", evhttp_find_header(&params, "s"));
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    strcat(output, tmp);
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    free(decoded_uri);
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    //获取POST方法的数据
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    char *post_data = (char *) EVBUFFER_DATA(req->input_buffer);
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    sprintf(tmp, "post_data=%s\n", post_data);
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    strcat(output, tmp);
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    /* 输出到客户端 */
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    //HTTP header
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    evhttp_add_header(req->output_headers, "Server", MYHTTPD_SIGNATURE);
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    evhttp_add_header(req->output_headers, "Content-Type", "text/plain; charset=UTF-8");
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    evhttp_add_header(req->output_headers, "Connection", "close");
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    //输出的内容
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    struct evbuffer *buf;
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    buf = evbuffer_new();
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    evbuffer_add_printf(buf, "It works!\n%s\n", output);
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    evhttp_send_reply(req, HTTP_OK, "OK", buf);
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    evbuffer_free(buf);
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}
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void show_help() {
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    char *help = "http://localhost:8080\n"
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        "-l <ip_addr> interface to listen on, default is 0.0.0.0\n"
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        "-p <num>     port number to listen on, default is 1984\n"
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        "-d           run as a deamon\n"
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        "-t <second>  timeout for a http request, default is 120 seconds\n"
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        "-h           print this help and exit\n"
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        "\n";
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    fprintf(stderr,"%s",help);
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}
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//当向进程发出SIGTERM/SIGHUP/SIGINT/SIGQUIT的时候，终止event的事件侦听循环
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void signal_handler(int sig) {
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    switch (sig) {
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        case SIGTERM:
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        case SIGHUP:
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        case SIGQUIT:
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        case SIGINT:
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            event_loopbreak();  //终止侦听event_dispatch()的事件侦听循环，执行之后的代码
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            break;
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    }
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}
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int main(int argc, char *argv[]) {
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    //自定义信号处理函数
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    signal(SIGHUP   , signal_handler);
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    signal(SIGTERM  , signal_handler);
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    signal(SIGINT   , signal_handler);
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    signal(SIGQUIT  , signal_handler);
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    //默认参数
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    char *httpd_option_listen = "0.0.0.0";
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    int httpd_option_port = 8080;
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    int httpd_option_daemon = 0;
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    int httpd_option_timeout = 120; //in seconds
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    LOG_INFO("http server start %s:%d\n", httpd_option_listen, httpd_option_port);
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    //获取参数
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    int c;
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    while ((c = getopt(argc, argv, "l:p:dt:h")) != -1) {
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        switch (c) {
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            case 'l' :
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                httpd_option_listen = optarg;
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                break;
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            case 'p' :
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                httpd_option_port = atoi(optarg);
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                break;
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            case 'd' :
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                httpd_option_daemon = 1;
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                break;
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            case 't' :
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                httpd_option_timeout = atoi(optarg);
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                break;
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            case 'h' :
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            default :
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                show_help();
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                exit(EXIT_SUCCESS);
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        }
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    }
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    //判断是否设置了-d，以daemon运行
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    if (httpd_option_daemon) {
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        pid_t pid;
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        pid = fork();
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        if (pid < 0) {
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            perror("fork failed");
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            exit(EXIT_FAILURE);
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        }
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        if (pid > 0) {
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            //生成子进程成功，退出父进程
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            exit(EXIT_SUCCESS);
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        }
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    }
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    /* 使用libevent创建HTTP Server */
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    //初始化event API
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    event_init();
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    //创建一个http server
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    struct evhttp *httpd;
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    httpd = evhttp_start(httpd_option_listen, httpd_option_port);
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    evhttp_set_timeout(httpd, httpd_option_timeout);
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    //指定generic callback
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    evhttp_set_gencb(httpd, httpd_handler, NULL);
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    //也可以为特定的URI指定callback
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    //evhttp_set_cb(httpd, "/", specific_handler, NULL);
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    //开始事件监听，分发
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    event_dispatch();
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    //释放资源
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    evhttp_free(httpd);
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    return 0;
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}