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。
1 /*
2 * gcc -g -o http-server http-server.c -levent
3 */
4 #include <stdio.h>
5 #include <stdlib.h>
6 #include <string.h>
7
8 #include <sys/types.h>
9 #include <sys/stat.h>
10 #include <sys/socket.h>
11 #include <signal.h>
12 #include <fcntl.h>
13 #include <unistd.h>
14 #include <dirent.h>
15 #include <errno.h>
16
17 #include <event2/event.h>
18 #include <event2/http.h>
19 #include <event2/buffer.h>
20 #include <event2/util.h>
21 #include <event2/keyvalq_struct.h>
22
23 #include <netinet/in.h>
24 #include <arpa/inet.h>
25
26 char uri_root[512];
27
28 static const struct table_entry {
29 const char *extension;
30 const char *content_type;
31 } content_type_table[] = {
32 { "txt", "text/plain" },
33 { "c", "text/plain" },
34 { "h", "text/plain" },
35 { "html", "text/html" },
36 { "htm", "text/html" },
37 { "css", "text/css" },
38 { "gif", "image/gif" },
39 { "jpg", "image/jpg" },
40 { "jpeg", "image/jpeg" },
41 { "png", "image/png" },
42 { "pdf", "application/pdf" },
43 { "ps", "application/postscript" },
44 { NULL, NULL },
45 };
46
47 /* Try to guess a good content-type for 'path' */
48 const char* guess_content_type(const char *path)
49 {
50 const char *last_period, *extension;
51 const struct table_entry *ent;
52 last_period = strrchr(path, '.');
53 if (!last_period || strchr(last_period, '/'))
54 {
55 goto not_found;
56 }
57
58 extension = last_period + 1;
59 for (ent = &content_type_table[0]; ent->extension; ++ent)
60 {
61 if (!evutil_ascii_strcasecmp(ent->extension, extension))
62 {
63 return ent->content_type;
64 }
65 }
66
67 not_found:
68 return "application/misc";
69 }
70
71 /* Callbase used for the /dump URI, and for every non-get request:
72 ** dumps all information to stdout and gives base a trivial 200 ok */
73 void dump_request_cb(struct evhttp_request *req, void *arg)
74 {
75 const char *cmdtype;
76 struct evkeyvalq *headers;
77 struct evkeyval *header;
78 struct evbuffer *buf;
79
80 switch (evhttp_request_get_command(req))
81 {
82 case EVHTTP_REQ_GET:
83 cmdtype = "GET";
84 break;
85 case EVHTTP_REQ_POST:
86 cmdtype = "POST";
87 break;
88 case EVHTTP_REQ_HEAD:
89 cmdtype = "HEAD";
90 break;
91 case EVHTTP_REQ_PUT:
92 cmdtype = "PUT";
93 break;
94 case EVHTTP_REQ_DELETE:
95 cmdtype = "DELETE";
96 break;
97 case EVHTTP_REQ_OPTIONS:
98 cmdtype = "OPTIONS";
99 break;
100 case EVHTTP_REQ_TRACE:
101 cmdtype = "TRACE";
102 break;
103 case EVHTTP_REQ_CONNECT:
104 break;
105 case EVHTTP_REQ_PATCH:
106 cmdtype = "PATCH";
107 break;
108 default:
109 cmdtype = "unknown";
110 break;
111 }
112
113 printf("Received a %s request for %s\nHeader:\n", cmdtype, evhttp_request_get_uri(req));
114
115 headers = evhttp_request_get_input_headers(req);
116 for (header = headers->tqh_first; header; header = header->next.tqe_next)
117 {
118 printf(" %s: %s\n", header->key, header->value);
119 }
120
121 buf = evhttp_request_get_input_buffer(req);
122 puts("Input data: <<<<");
123 while (evbuffer_get_length(buf))
124 {
125 int n;
126 char cbuf[128];
127 n = evbuffer_remove(buf, cbuf, sizeof(cbuf));
128 if (n > 0)
129 {
130 (void)fwrite(cbuf, 1, n, stdout);
131 }
132 }
133 puts(">>>");
134
135 evhttp_send_reply(req, 200, "ok", NULL);
136 }
137
138 /* This callback gets invoked when we get and http request than doesn't match
139 * any other callback. Like any evhttp server callback, it has a simple job:
140 * it must eventually call evhttp_send_error() or evhttp_send_reply().
141 */
142 void send_document_cb(struct evhttp_request *req, void *arg)
143 {
144 struct evbuffer *evb = NULL;
145 const char *docroot = arg;
146 const char *uri = evhttp_request_get_uri(req);
147 struct evhttp_uri *decoded = NULL;
148 const char *path;
149 char *decoded_path;
150 char *whole_path = NULL;
151 size_t len;
152 int fd = -1;
153 struct stat st;
154
155 if (evhttp_request_get_command(req) != EVHTTP_REQ_GET)
156 {
157 dump_request_cb(req, arg);
158 return;
159 }
160
161 printf("Got a GET request for <%s>\n", uri);
162
163 /* Decode the URI */
164 decoded = evhttp_uri_parse(uri);
165 if (!decoded)
166 {
167 printf("It's not a good URI, Sneding BADREQUEST\n");
168 evhttp_send_error(req, HTTP_BADREQUEST, 0);
169 return;
170 }
171
172 /* Let's see what path the user asked for. */
173 path = evhttp_uri_get_path(decoded);
174 if (!path)
175 {
176 path = "/";
177 }
178
179 /* We need to decode it, to see what path the user really wanted */
180 decoded_path = evhttp_uridecode(path, 0, NULL);
181 if (decoded_path == NULL)
182 {
183 goto err;
184 }
185
186 /* Don't allow any ".."'s in the path, to avoid exposing stuff outside
187 * of the docroot. This test is both overzealous and underzealous:
188 * it forbids aceptable paths like "/this/one..here", but it doesn't
189 * do anything to prevent symlink following. */
190 if (strstr(decoded_path, ".."))
191 {
192 goto err;
193 }
194
195 len = strlen(decoded_path) + strlen(docroot) + 2;
196 if (!(whole_path = malloc(len)))
197 {
198 perror("malloc");
199 goto err;
200 }
201 evutil_snprintf(whole_path, len, "%s/%s", docroot, decoded_path);
202
203 if (stat(whole_path, &st) < 0)
204 {
205 goto err;
206 }
207
208 /* This holds the content we're sending */
209 evb = evbuffer_new();
210
211 if (S_ISDIR(st.st_mode))
212 {
213 /* If it's a directory, read the comments and make a little index page */
214 DIR *d;
215 struct dirent *ent;
216 const char *trailing_slash = "";
217
218 if (!strlen(path) || path[strlen(path) - 1] != '/')
219 {
220 trailing_slash = "/";
221 }
222
223 if (!(d = opendir(whole_path)))
224 {
225 goto err;
226 }
227
228 evbuffer_add_printf(evb,
229 "<!DOCTYPE html>\n"
230 "<html>\n "
231 " <head>\n"
232 " <meta charset='utf-8'>\n"
233 " <title>%s</title>\n"
234 " <base href='%s%s'>\n"
235 " </head>\n"
236 " <body>\n"
237 " <h1>%s</h1>\n"
238 " <ul>\n",
239 decoded_path, /* xxx html-escape this. */
240 path, /* xxx html-escape this? */
241 trailing_slash,
242 decoded_path /* xx html-escape this */
243 );
244
245 while ((ent = readdir(d)))
246 {
247 const char *name = ent->d_name;
248 evbuffer_add_printf(evb,
249 " <li><a href=\"%s\">%s</a>\n", name, name);
250 }
251
252 evbuffer_add_printf(evb, "</ul></body></html>\n");
253 closedir(d);
254 evhttp_add_header(evhttp_request_get_output_headers(req),
255 "Content-Type", "text/html");
256 }
257 else
258 {
259 /* Otherwise it's a file; and it to the buffer to get send via sendfile */
260 const char *type = guess_content_type(decoded_path);
261 if ((fd = open(whole_path, O_RDONLY)) < 0)
262 {
263 perror("open");
264 goto err;
265 }
266
267 if (fstat(fd, &st) < 0)
268 {
269 /* Make sure the length still matches, now that we opened the file :/ */
270 perror("fstat");
271 goto err;
272 }
273 evhttp_add_header(evhttp_request_get_output_headers(req),
274 "Content-Type", type);
275 evbuffer_add_file(evb, fd, 0, st.st_size);
276 }
277
278 evhttp_send_reply(req, 200, "OK", evb);
279 goto done;
280
281 err:
282 evhttp_send_error(req, 404, "Document was not found");
283 if (fd >= 0)
284 {
285 close(fd);
286 }
287
288 done:
289 if (decoded)
290 {
291 evhttp_uri_free(decoded);
292 }
293
294 if (decoded_path)
295 {
296 free(decoded_path);
297 }
298
299 if (whole_path)
300 {
301 free(whole_path);
302 }
303
304 if (evb)
305 {
306 evbuffer_free(evb);
307 }
308 }
309
310 void syntax(void)
311 {
312 fprintf(stdout, "Syntax: http-server <docroot>\n");
313 }
314
315 int main(int argc, char **argv)
316 {
317 struct event_base *base;
318 struct evhttp *http;
319 struct evhttp_bound_socket *handle;
320 int port = 0;
321
322 if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
323 {
324 printf("signal error, errno[%d], error[%s]", errno, strerror(errno));
325 return -1;
326 }
327
328 if (argc < 2)
329 {
330 syntax();
331 return -1;
332 }
333
334 base = event_base_new();
335 if (!base)
336 {
337 printf("Couldn't create an event_base:exiting\n");
338 return -1;
339 }
340
341 /* Create a new http oject to handle request */
342 http = evhttp_new(base);
343 if (!http)
344 {
345 printf("Couldn't create evhttp.Exiting\n");
346 return -1;
347 }
348
349 /* The /dump URI will dump all requests to stdout and say 200 ok */
350 evhttp_set_cb(http, "/dump", dump_request_cb, NULL);
351
352 /* We want to accept arbitrary requests, so we need to set a "generic" cb
353 * We can also add callbacks for specific paths */
354 evhttp_set_gencb(http, send_document_cb, argv[1]);
355
356 /* Now we teel the evhttp what port to listen on */
357 handle = evhttp_bind_socket_with_handle(http, "0.0.0.0", port);
358 if (!handle)
359 {
360 printf("Couldn't bind to port[%d], exiting\n", port);
361 return -1;
362 }
363
364 {
365 /* Extract and display the address we're listening on. */
366 struct sockaddr_storage ss;
367 evutil_socket_t fd;
368 ev_socklen_t socklen = sizeof(ss);
369 char addrbuf[128];
370 void *inaddr;
371 const char *addr;
372 int got_port = -1;
373 fd = evhttp_bound_socket_get_fd(handle);
374 memset(&ss, 0, sizeof(ss));
375 if (getsockname(fd, (struct sockaddr *)&ss, &socklen))
376 {
377 perror("getsockname() failed");
378 return -1;
379 }
380
381 if (ss.ss_family == AF_INET)
382 {
383 got_port = ntohs(((struct sockaddr_in*)&ss)->sin_port);
384 inaddr = &((struct sockaddr_in*)&ss)->sin_addr;
385 }
386 else if (ss.ss_family == AF_INET6)
387 {
388 got_port = ntohs(((struct sockaddr_in6*)&ss)->sin6_port);
389 inaddr = &((struct sockaddr_in6*)&ss)->sin6_addr;
390 }
391 else
392 {
393 printf("Weird address family\n");
394 return 1;
395 }
396
397 addr = evutil_inet_ntop(ss.ss_family, inaddr, addrbuf, sizeof(addrbuf));
398 if (addr)
399 {
400 printf("Listening on %s:%d\n", addr, got_port);
401 evutil_snprintf(uri_root, sizeof(uri_root), "http://%s:%d", addr, got_port);
402 }
403 else
404 {
405 printf("evutil_inet_ntop failed\n");
406 return -1;
407 }
408 }
409 event_base_dispatch(base);
410
411 return 0;
412 }
View Code
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。
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