http-server例子是libevent提供的一个简单web服务器,实现了对静态网页的处理功能。
- /*
- * gcc -g -o http-server http-server.c -levent
- */
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
-
- #include <sys/types.h>
- #include <sys/stat.h>
- #include <sys/socket.h>
- #include <signal.h>
- #include <fcntl.h>
- #include <unistd.h>
- #include <dirent.h>
- #include <errno.h>
-
- #include <event2/event.h>
- #include <event2/http.h>
- #include <event2/buffer.h>
- #include <event2/util.h>
- #include <event2/keyvalq_struct.h>
-
- #include <netinet/in.h>
- #include <arpa/inet.h>
-
- char uri_root[512];
-
- static const struct table_entry {
- const char *extension;
- const char *content_type;
- } content_type_table[] = {
- { "txt", "text/plain" },
- { "c", "text/plain" },
- { "h", "text/plain" },
- { "html", "text/html" },
- { "htm", "text/html" },
- { "css", "text/css" },
- { "gif", "image/gif" },
- { "jpg", "image/jpg" },
- { "jpeg", "image/jpeg" },
- { "png", "image/png" },
- { "pdf", "application/pdf" },
- { "ps", "application/postscript" },
- { NULL, NULL },
- };
-
- /* Try to guess a good content-type for 'path' */
- const char* guess_content_type(const char *path)
- {
- const char *last_period, *extension;
- const struct table_entry *ent;
- last_period = strrchr(path, '.');
- if (!last_period || strchr(last_period, '/'))
- {
- goto not_found;
- }
-
- extension = last_period + 1;
- for (ent = &content_type_table[0]; ent->extension; ++ent)
- {
- if (!evutil_ascii_strcasecmp(ent->extension, extension))
- {
- return ent->content_type;
- }
- }
-
- not_found:
- return "application/misc";
- }
-
- /* Callbase used for the /dump URI, and for every non-get request:
- ** dumps all information to stdout and gives base a trivial 200 ok */
- void dump_request_cb(struct evhttp_request *req, void *arg)
- {
- const char *cmdtype;
- struct evkeyvalq *headers;
- struct evkeyval *header;
- struct evbuffer *buf;
-
- switch (evhttp_request_get_command(req))
- {
- case EVHTTP_REQ_GET:
- cmdtype = "GET";
- break;
- case EVHTTP_REQ_POST:
- cmdtype = "POST";
- break;
- case EVHTTP_REQ_HEAD:
- cmdtype = "HEAD";
- break;
- case EVHTTP_REQ_PUT:
- cmdtype = "PUT";
- break;
- case EVHTTP_REQ_DELETE:
- cmdtype = "DELETE";
- break;
- case EVHTTP_REQ_OPTIONS:
- cmdtype = "OPTIONS";
- break;
- case EVHTTP_REQ_TRACE:
- cmdtype = "TRACE";
- break;
- case EVHTTP_REQ_CONNECT:
- break;
- case EVHTTP_REQ_PATCH:
- cmdtype = "PATCH";
- break;
- default:
- cmdtype = "unknown";
- break;
- }
-
- printf("Received a %s request for %s\nHeader:\n", cmdtype, evhttp_request_get_uri(req));
-
- headers = evhttp_request_get_input_headers(req);
- for (header = headers->tqh_first; header; header = header->next.tqe_next)
- {
- printf(" %s: %s\n", header->key, header->value);
- }
-
- buf = evhttp_request_get_input_buffer(req);
- puts("Input data: <<<<");
- while (evbuffer_get_length(buf))
- {
- int n;
- char cbuf[128];
- n = evbuffer_remove(buf, cbuf, sizeof(cbuf));
- if (n > 0)
- {
- (void)fwrite(cbuf, 1, n, stdout);
- }
- }
- puts(">>>");
-
- evhttp_send_reply(req, 200, "ok", NULL);
- }
-
- /* This callback gets invoked when we get and http request than doesn't match
- * any other callback. Like any evhttp server callback, it has a simple job:
- * it must eventually call evhttp_send_error() or evhttp_send_reply().
- */
- void send_document_cb(struct evhttp_request *req, void *arg)
- {
- struct evbuffer *evb = NULL;
- const char *docroot = arg;
- const char *uri = evhttp_request_get_uri(req);
- struct evhttp_uri *decoded = NULL;
- const char *path;
- char *decoded_path;
- char *whole_path = NULL;
- size_t len;
- int fd = -1;
- struct stat st;
-
- if (evhttp_request_get_command(req) != EVHTTP_REQ_GET)
- {
- dump_request_cb(req, arg);
- return;
- }
-
- printf("Got a GET request for <%s>\n", uri);
-
- /* Decode the URI */
- decoded = evhttp_uri_parse(uri);
- if (!decoded)
- {
- printf("It's not a good URI, Sneding BADREQUEST\n");
- evhttp_send_error(req, HTTP_BADREQUEST, 0);
- return;
- }
-
- /* Let's see what path the user asked for. */
- path = evhttp_uri_get_path(decoded);
- if (!path)
- {
- path = "/";
- }
-
- /* We need to decode it, to see what path the user really wanted */
- decoded_path = evhttp_uridecode(path, 0, NULL);
- if (decoded_path == NULL)
- {
- goto err;
- }
-
- /* Don't allow any ".."'s in the path, to avoid exposing stuff outside
- * of the docroot. This test is both overzealous and underzealous:
- * it forbids aceptable paths like "/this/one..here", but it doesn't
- * do anything to prevent symlink following. */
- if (strstr(decoded_path, ".."))
- {
- goto err;
- }
-
- len = strlen(decoded_path) + strlen(docroot) + 2;
- if (!(whole_path = malloc(len)))
- {
- perror("malloc");
- goto err;
- }
- evutil_snprintf(whole_path, len, "%s/%s", docroot, decoded_path);
-
- if (stat(whole_path, &st) < 0)
- {
- goto err;
- }
-
- /* This holds the content we're sending */
- evb = evbuffer_new();
-
- if (S_ISDIR(st.st_mode))
- {
- /* If it's a directory, read the comments and make a little index page */
- DIR *d;
- struct dirent *ent;
- const char *trailing_slash = "";
-
- if (!strlen(path) || path[strlen(path) - 1] != '/')
- {
- trailing_slash = "/";
- }
-
- if (!(d = opendir(whole_path)))
- {
- goto err;
- }
-
- evbuffer_add_printf(evb,
- "<!DOCTYPE html>\n"
- "<html>\n "
- " <head>\n"
- " <meta charset='utf-8'>\n"
- " <title>%s</title>\n"
- " <base href='%s%s'>\n"
- " </head>\n"
- " <body>\n"
- " <h1>%s</h1>\n"
- " <ul>\n",
- decoded_path, /* xxx html-escape this. */
- path, /* xxx html-escape this? */
- trailing_slash,
- decoded_path /* xx html-escape this */
- );
-
- while ((ent = readdir(d)))
- {
- const char *name = ent->d_name;
- evbuffer_add_printf(evb,
- " <li><a href=\"%s\">%s</a>\n", name, name);
- }
-
- evbuffer_add_printf(evb, "</ul></body></html>\n");
- closedir(d);
- evhttp_add_header(evhttp_request_get_output_headers(req),
- "Content-Type", "text/html");
- }
- else
- {
- /* Otherwise it's a file; and it to the buffer to get send via sendfile */
- const char *type = guess_content_type(decoded_path);
- if ((fd = open(whole_path, O_RDONLY)) < 0)
- {
- perror("open");
- goto err;
- }
-
- if (fstat(fd, &st) < 0)
- {
- /* Make sure the length still matches, now that we opened the file :/ */
- perror("fstat");
- goto err;
- }
- evhttp_add_header(evhttp_request_get_output_headers(req),
- "Content-Type", type);
- evbuffer_add_file(evb, fd, 0, st.st_size);
- }
-
- evhttp_send_reply(req, 200, "OK", evb);
- goto done;
-
- err:
- evhttp_send_error(req, 404, "Document was not found");
- if (fd >= 0)
- {
- close(fd);
- }
-
- done:
- if (decoded)
- {
- evhttp_uri_free(decoded);
- }
-
- if (decoded_path)
- {
- free(decoded_path);
- }
-
- if (whole_path)
- {
- free(whole_path);
- }
-
- if (evb)
- {
- evbuffer_free(evb);
- }
- }
-
- void syntax(void)
- {
- fprintf(stdout, "Syntax: http-server <docroot>\n");
- }
-
- int main(int argc, char **argv)
- {
- struct event_base *base;
- struct evhttp *http;
- struct evhttp_bound_socket *handle;
- int port = 0;
-
- if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
- {
- printf("signal error, errno[%d], error[%s]", errno, strerror(errno));
- return -1;
- }
-
- if (argc < 2)
- {
- syntax();
- return -1;
- }
-
- base = event_base_new();
- if (!base)
- {
- printf("Couldn't create an event_base:exiting\n");
- return -1;
- }
-
- /* Create a new http oject to handle request */
- http = evhttp_new(base);
- if (!http)
- {
- printf("Couldn't create evhttp.Exiting\n");
- return -1;
- }
-
- /* The /dump URI will dump all requests to stdout and say 200 ok */
- evhttp_set_cb(http, "/dump", dump_request_cb, NULL);
-
- /* We want to accept arbitrary requests, so we need to set a "generic" cb
- * We can also add callbacks for specific paths */
- evhttp_set_gencb(http, send_document_cb, argv[1]);
-
- /* Now we teel the evhttp what port to listen on */
- handle = evhttp_bind_socket_with_handle(http, "0.0.0.0", port);
- if (!handle)
- {
- printf("Couldn't bind to port[%d], exiting\n", port);
- return -1;
- }
-
- {
- /* Extract and display the address we're listening on. */
- struct sockaddr_storage ss;
- evutil_socket_t fd;
- ev_socklen_t socklen = sizeof(ss);
- char addrbuf[128];
- void *inaddr;
- const char *addr;
- int got_port = -1;
- fd = evhttp_bound_socket_get_fd(handle);
- memset(&ss, 0, sizeof(ss));
- if (getsockname(fd, (struct sockaddr *)&ss, &socklen))
- {
- perror("getsockname() failed");
- return -1;
- }
-
- if (ss.ss_family == AF_INET)
- {
- got_port = ntohs(((struct sockaddr_in*)&ss)->sin_port);
- inaddr = &((struct sockaddr_in*)&ss)->sin_addr;
- }
- else if (ss.ss_family == AF_INET6)
- {
- got_port = ntohs(((struct sockaddr_in6*)&ss)->sin6_port);
- inaddr = &((struct sockaddr_in6*)&ss)->sin6_addr;
- }
- else
- {
- printf("Weird address family\n");
- return 1;
- }
-
- addr = evutil_inet_ntop(ss.ss_family, inaddr, addrbuf, sizeof(addrbuf));
- if (addr)
- {
- printf("Listening on %s:%d\n", addr, got_port);
- evutil_snprintf(uri_root, sizeof(uri_root), "http://%s:%d", addr, got_port);
- }
- else
- {
- printf("evutil_inet_ntop failed\n");
- return -1;
- }
- }
- event_base_dispatch(base);
-
- return 0;
- }
下面就通过分析这个例子来理解evhttp对象的使用与实现:
1、首先介绍一个这段代码里面的几个函数及其作用:
1)guess_content_type:传入请求的路径,返回文件类型(根据请求资源的后缀名返回响应的MIME类型)
2)dump_requese_cb:这个函数是当uri为/dump时的回调,操作是打印全部的请求信息。
3)send_document_cb:这个函数是通用uri的回调函数,就是将请求的资源发送给客户端(浏览器)。
4)syntax:打印用法的函数
5)main:主函数
2、调用event_base_new函数得到一个event base对象。
3、调用evhttp_new函数得到一个evhttp对象。
4、调用evhttp_set_cb、evthttp_set_gencb设置回调函数和通用回调函数。
5、调用evhttp_bind_socket_with_handle函数设置监听端口。
6、打印监听端口信息。
7、调用event_base_dispatch进入事件循环。
这里使用了一个新的类evhttp,这个也是对基本函数更高层次的封装,方便编写http相关的程序,关于这个类会在后面详细的分析,这里略过。
到这里就分析完http-server了,可以发现使用libevent提供的函数来编写一个http-server服务器是多么的简单。