libevent http多线程c++

libevent是一个事件驱动的网络编程库，它提供了高效的事件处理机制和多线程支持。在libevent中，HTTP服务器可以使用多线程来处理并发请求。下面是一个简单的HTTP服务器的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <event2/event.h>
#include <event2/http.h>
#include <event2/buffer.h>

static void http_handler(struct evhttp_request *req, void *arg)
{
    struct evbuffer *buf = evbuffer_new();
    if (buf == NULL) {
        fprintf(stderr, "failed to create response buffer\n");
        evhttp_send_error(req, HTTP_INTERNAL, "Internal server error");
        return;
    }

    evbuffer_add_printf(buf, "Hello, world!");

    evhttp_add_header(evhttp_request_get_output_headers(req),
                      "Content-Type", "text/plain");
    evhttp_send_reply(req, HTTP_OK, "OK", buf);
    evbuffer_free(buf);
}

int main(int argc, char **argv)
{
    struct event_base *base;
    struct evhttp *http;
    struct evhttp_bound_socket *handle;

    base = event_base_new();
    if (base == NULL) {
        fprintf(stderr, "failed to create event base\n");
        return 1;
    }

    http = evhttp_new(base);
    if (http == NULL) {
        fprintf(stderr, "failed to create HTTP server\n");
        return 1;
    }

    evhttp_set_cb(http, "/", http_handler, NULL);

    handle = evhttp_bind_socket_with_handle(http, "127.0.0.1", 8080);
    if (handle == NULL) {
        fprintf(stderr, "failed to bind socket\n");
        return 1;
    }

    event_base_loop(base, 0);

    evhttp_free(http);
    event_base_free(base);

    return 0;
}

在这个示例中，我们创建了一个event_base和一个evhttp结构体，并将HTTP请求处理函数注册到evhttp中。然后，使用evhttp_bind_socket_with_handle函数绑定一个监听地址和端口，并进入事件循环。当有新的HTTP请求到达时，事件循环将自动调用我们注册的处理函数进行处理。

如果需要支持多线程，我们可以使用event_base_new_with_config函数创建一个带有配置的event_base，然后使用event_config_set_num_cpus_hint函数指定处理事件的线程数。例如，我们可以将处理事件的线程数设置为CPU核心数的两倍：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <event2/event.h>
#include <event2/http.h>
#include <event2/buffer.h>

static void http_handler(struct evhttp_request *req, void *arg)
{
    struct evbuffer *buf = evbuffer_new();
    if (buf == NULL) {
        fprintf(stderr, "failed to create response buffer\n");
        evhttp_send_error(req, HTTP_INTERNAL, "Internal server error");
        return;
    }

    evbuffer_add_printf(buf, "Hello, world!");

    evhttp_add_header(evhttp_request_get_output_headers(req),
                      "Content-Type", "text/plain");
    evhttp_send_reply(req, HTTP_OK, "OK", buf);
    evbuffer_free(buf);
}

int main(int argc, char **argv)
{
    struct event_base *base;
    struct event_config *config;
    struct evhttp *http;
    struct evhttp_bound_socket *handle;

    config = event_config_new();
    if (config == NULL) {
        fprintf(stderr, "failed to create event config\n");
        return 1;
    }

    event_config_set_num_cpus_hint(config, sysconf(_SC_NPROCESSORS_ONLN) * 2);

    base = event_base_new_with_config(config);
    if (base == NULL) {
        fprintf(stderr, "failed to create event base\n");
        return 1;
    }

    http = evhttp_new(base);
    if (http == NULL) {
        fprintf(stderr, "failed to create HTTP server\n");
        return 1;
    }

    evhttp_set_cb(http, "/", http_handler, NULL);

    handle = evhttp_bind_socket_with_handle(http, "127.0.0.1", 8080);
    if (handle == NULL) {
        fprintf(stderr, "failed to bind socket\n");
        return 1;
    }

    event_base_loop(base, 0);

    evhttp_free(http);
    event_base_free(base);

    return 0;
}

在这个示例中，我们使用event_config_new函数创建一个event_config结构体，并使用event_config_set_num_cpus_hint函数设置处理事件的线程数。然后，使用event_base_new_with_config函数创建一个带有配置的event_base，其他部分与之前的示例相同。