只要接觸過c/c++網路編程人都可能會知道select io 模式，網絡書籍都說 fd_set {int num; SOCKET arr[64]} 有所限制，因為數組的長度只有64，那么超過64你就不能放，要么你就是用多線程分別實用select.。
后來，自己看到了libevent的源代碼發現他也用的是select。。看別人說這個庫，輕輕松松處理上萬個套接字，我就在想select不是有限制嗎？？他是怎么做到。。。。。。
};
這個就是新定義結構體，跟原來稍微有點變化只是把64改為1，有些同學可能見多很多這樣的寫法，這種寫法我也在一些項目使用了。這種寫法可以fd_array動態變化。
win_fd_set * Set = (win_fd_set*)malloc(sizeof(win_fd_set) + sizoef(SCOEKT) * 10);
Set->fd_array 可以放11 個 SOCKET，因為我的內存大小足夠放11個SOCKET。
請記住內存是沒有數據格式，只要足夠大小，隨便你怎么放。數據格式只是方便我們管理和處理數據而已。
這樣就解決64個大小限制。。我其實一直很好奇為什么中國書籍都是一樣的，libevent已經出來好久了，但也沒有看到有人說這一點，可能是高手們都不屑。
現在漸漸喜歡看開源的代碼，不喜歡看書籍了，喜歡在代碼中學習他們是怎么組織一個好項目。
有時候感慨：
高手用c 寫著漂亮的c++代碼，而我等菜鳥卻用c++ 寫丑陋的c代碼。。
我順便把他整個定義結構和函數給大家貼出來，免大家還要自己去下libevent，不過推薦沒有看過libevent同學，可以稍微看一下。
1 volatile double SIGFPE_REQ = 0.0f;
2
3 struct idx_info {
4 int read_pos_plus1;
5 int write_pos_plus1;
6 };
7
8 struct win32op {
9 unsigned num_fds_in_fd_sets;
10 int resize_out_sets;
11 struct win_fd_set *readset_in;
12 struct win_fd_set *writeset_in;
13 struct win_fd_set *readset_out;
14 struct win_fd_set *writeset_out;
15 struct win_fd_set *exset_out;
16 unsigned signals_are_broken : 1;
17 };
18
19 static void *win32_init(struct event_base *);
20 static int win32_add(struct event_base *, evutil_socket_t, short old, short events, void *_idx);
21 static int win32_del(struct event_base *, evutil_socket_t, short old, short events, void *_idx);
22 static int win32_dispatch(struct event_base *base, struct timeval *);
23 static void win32_dealloc(struct event_base *);
24
25 struct eventop win32ops = {
26 "win32",
27 win32_init,
28 win32_add,
29 win32_del,
30 win32_dispatch,
31 win32_dealloc,
32 0, /* doesn't need reinit */
33 0, /* No features supported. */
34 sizeof(struct idx_info),
35 };
36
37 #define FD_SET_ALLOC_SIZE(n) ((sizeof(struct win_fd_set) + ((n)-1)*sizeof(SOCKET)))
38
39 static int
40 grow_fd_sets(struct win32op *op, unsigned new_num_fds)
41 {
42 size_t size;
43
44 EVUTIL_ASSERT(new_num_fds >= op->readset_in->fd_count &&
45 new_num_fds >= op->writeset_in->fd_count);
46 EVUTIL_ASSERT(new_num_fds >= 1);
47
48 size = FD_SET_ALLOC_SIZE(new_num_fds);
49 if (!(op->readset_in = mm_realloc(op->readset_in, size)))
50 return (-1);
51 if (!(op->writeset_in = mm_realloc(op->writeset_in, size)))
52 return (-1);
53 op->resize_out_sets = 1;
54 op->num_fds_in_fd_sets = new_num_fds;
55 return (0);
56 }
57
58 static int
59 do_fd_set(struct win32op *op, struct idx_info *ent, evutil_socket_t s, int read)
60 {
61 struct win_fd_set *set = read ? op->readset_in : op->writeset_in;
62 if (read) {
63 if (ent->read_pos_plus1 > 0)
64 return (0);
65 } else {
66 if (ent->write_pos_plus1 > 0)
67 return (0);
68 }
69 if (set->fd_count == op->num_fds_in_fd_sets) {
70 if (grow_fd_sets(op, op->num_fds_in_fd_sets*2))
71 return (-1);
72 /* set pointer will have changed and needs reiniting! */
73 set = read ? op->readset_in : op->writeset_in;
74 }
75 set->fd_array[set->fd_count] = s;
76 if (read)
77 ent->read_pos_plus1 = set->fd_count+1;
78 else
79 ent->write_pos_plus1 = set->fd_count+1;
80 return (set->fd_count++);
81 }
82
83 static int
84 do_fd_clear(struct event_base *base,
85 struct win32op *op, struct idx_info *ent, int read)
86 {
87 int i;
88 struct win_fd_set *set = read ? op->readset_in : op->writeset_in;
89 if (read) {
90 i = ent->read_pos_plus1 - 1;
91 ent->read_pos_plus1 = 0;
92 } else {
93 i = ent->write_pos_plus1 - 1;
94 ent->write_pos_plus1 = 0;
95 }
96 if (i < 0)
97 return (0);
98 if (--set->fd_count != (unsigned)i) {
99 struct idx_info *ent2;
100 SOCKET s2;
101 s2 = set->fd_array[i] = set->fd_array[set->fd_count];
102
103 ent2 = evmap_io_get_fdinfo(&base->io, s2);
104
105 if (!ent2) /* This indicates a bug. */
106 return (0);
107 if (read)
108 ent2->read_pos_plus1 = i+1;
109 else
110 ent2->write_pos_plus1 = i+1;
111 }
112 return (0);
113 }
114
115 #define NEVENT 32
116 void *
117 win32_init(struct event_base *_base)
118 {
119 struct win32op *winop;
120 size_t size;
121 if (!(winop = mm_calloc(1, sizeof(struct win32op))))
122 return NULL;
123 winop->num_fds_in_fd_sets = NEVENT;
124 size = FD_SET_ALLOC_SIZE(NEVENT);
125 if (!(winop->readset_in = mm_malloc(size)))
126 goto err;
127 if (!(winop->writeset_in = mm_malloc(size)))
128 goto err;
129 if (!(winop->readset_out = mm_malloc(size)))
130 goto err;
131 if (!(winop->writeset_out = mm_malloc(size)))
132 goto err;
133 if (!(winop->exset_out = mm_malloc(size)))
134 goto err;
135 winop->readset_in->fd_count = winop->writeset_in->fd_count = 0;
136 winop->readset_out->fd_count = winop->writeset_out->fd_count
137 = winop->exset_out->fd_count = 0;
138
139 if (evsig_init(_base) < 0)
140 winop->signals_are_broken = 1;
141
142 return (winop);
143 err:
144 XFREE(winop->readset_in);
145 XFREE(winop->writeset_in);
146 XFREE(winop->readset_out);
147 XFREE(winop->writeset_out);
148 XFREE(winop->exset_out);
149 XFREE(winop);
150 return (NULL);
151 }
152
153 int
154 win32_add(struct event_base *base, evutil_socket_t fd,
155 short old, short events, void *_idx)
156 {
157 struct win32op *win32op = base->evbase;
158 struct idx_info *idx = _idx;
159
160 if ((events & EV_SIGNAL) && win32op->signals_are_broken)
161 return (-1);
162
163 if (!(events & (EV_READ|EV_WRITE)))
164 return (0);
165
166 event_debug(("%s: adding event for %d", __func__, (int)fd));
167 if (events & EV_READ) {
168 if (do_fd_set(win32op, idx, fd, 1)<0)
169 return (-1);
170 }
171 if (events & EV_WRITE) {
172 if (do_fd_set(win32op, idx, fd, 0)<0)
173 return (-1);
174 }
175 return (0);
176 }
177
178 int
179 win32_del(struct event_base *base, evutil_socket_t fd, short old, short events,
180 void *_idx)
181 {
182 struct win32op *win32op = base->evbase;
183 struct idx_info *idx = _idx;
184
185 event_debug(("%s: Removing event for "EV_SOCK_FMT,
186 __func__, EV_SOCK_ARG(fd)));
187 if (events & EV_READ)
188 do_fd_clear(base, win32op, idx, 1);
189 if (events & EV_WRITE)
190 do_fd_clear(base, win32op, idx, 0);
191
192 return 0;
193 }
194
195 static void
196 fd_set_copy(struct win_fd_set *out, const struct win_fd_set *in)
197 {
198 out->fd_count = in->fd_count;
199 memcpy(out->fd_array, in->fd_array, in->fd_count * (sizeof(SOCKET)));
200 }
201
202 /*
203 static void dump_fd_set(struct win_fd_set *s)
204 {
205 unsigned int i;
206 printf("[ ");
207 for(i=0;i<s->fd_count;++i)
208 printf("%d ",(int)s->fd_array[i]);
209 printf("]\n");
210 }
211 */
212
213 int
214 win32_dispatch(struct event_base *base, struct timeval *tv)
215 {
216 struct win32op *win32op = base->evbase;
217 int res = 0;
218 unsigned j, i;
219 int fd_count;
220 SOCKET s;
221
222 if (win32op->resize_out_sets) {
223 size_t size = FD_SET_ALLOC_SIZE(win32op->num_fds_in_fd_sets);
224 if (!(win32op->readset_out = mm_realloc(win32op->readset_out, size)))
225 return (-1);
226 if (!(win32op->exset_out = mm_realloc(win32op->exset_out, size)))
227 return (-1);
228 if (!(win32op->writeset_out = mm_realloc(win32op->writeset_out, size)))
229 return (-1);
230 win32op->resize_out_sets = 0;
231 }
232
233 fd_set_copy(win32op->readset_out, win32op->readset_in);
234 fd_set_copy(win32op->exset_out, win32op->writeset_in);
235 fd_set_copy(win32op->writeset_out, win32op->writeset_in);
236
237 fd_count =
238 (win32op->readset_out->fd_count > win32op->writeset_out->fd_count) ?
239 win32op->readset_out->fd_count : win32op->writeset_out->fd_count;
240
241 if (!fd_count) {
242 long msec = tv ? evutil_tv_to_msec(tv) : LONG_MAX;
243 /* Sleep's DWORD argument is unsigned long */
244 if (msec < 0)
245 msec = LONG_MAX;
246 /* Windows doesn't like you to call select() with no sockets */
247 Sleep(msec);
248 return (0);
249 }
250
251 EVBASE_RELEASE_LOCK(base, th_base_lock);
252
253 res = select(fd_count,
254 (struct fd_set*)win32op->readset_out,
255 (struct fd_set*)win32op->writeset_out,
256 (struct fd_set*)win32op->exset_out, tv);
257
258 EVBASE_ACQUIRE_LOCK(base, th_base_lock);
259
260 event_debug(("%s: select returned %d", __func__, res));
261
262 if (res <= 0) {
263 return res;
264 }
265
266 if (win32op->readset_out->fd_count) {
267 i = rand() % win32op->readset_out->fd_count;
268 for (j=0; j<win32op->readset_out->fd_count; ++j) {
269 if (++i >= win32op->readset_out->fd_count)
270 i = 0;
271 s = win32op->readset_out->fd_array[i];
272 evmap_io_active(base, s, EV_READ);
273 }
274 }
275 if (win32op->exset_out->fd_count) {
276 i = rand() % win32op->exset_out->fd_count;
277 for (j=0; j<win32op->exset_out->fd_count; ++j) {
278 if (++i >= win32op->exset_out->fd_count)
279 i = 0;
280 s = win32op->exset_out->fd_array[i];
281 evmap_io_active(base, s, EV_WRITE);
282 }
283 }
284 if (win32op->writeset_out->fd_count) {
285 SOCKET s;
286 i = rand() % win32op->writeset_out->fd_count;
287 for (j=0; j<win32op->writeset_out->fd_count; ++j) {
288 if (++i >= win32op->writeset_out->fd_count)
289 i = 0;
290 s = win32op->writeset_out->fd_array[i];
291 evmap_io_active(base, s, EV_WRITE);
292 }
293 }
294 return (0);
295 }
296
297 void
298 win32_dealloc(struct event_base *_base)
299 {
300 struct win32op *win32op = _base->evbase;
301
302 evsig_dealloc(_base);
303 if (win32op->readset_in)
304 mm_free(win32op->readset_in);
305 if (win32op->writeset_in)
306 mm_free(win32op->writeset_in);
307 if (win32op->readset_out)
308 mm_free(win32op->readset_out);
309 if (win32op->writeset_out)
310 mm_free(win32op->writeset_out);
311 if (win32op->exset_out)
312 mm_free(win32op->exset_out);
313 /* XXXXX free the tree. */
314
315 memset(win32op, 0, sizeof(win32op));
316 mm_free(win32op);
317 }
posted on 2013-12-10 14:20
小魚兒 閱讀(6965)
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