2 * UCW Library -- Main Loop
4 * (c) 2004--2010 Martin Mares <mj@ucw.cz>
6 * This software may be freely distributed and used according to the terms
7 * of the GNU Lesser General Public License.
10 #ifndef _UCW_MAINLOOP_H
11 #define _UCW_MAINLOOP_H
13 #include "ucw/clists.h"
20 * The descriptions of structures contain some fields marked with `[*]`.
21 * These are the only ones that are intended to be manipulated by the user.
22 * The remaining fields serve for internal use only and you must initialize them
25 * FIXME: The documentation is outdated.
29 timestamp_t now; /** [*] Current time in milliseconds since the UNIX epoch. See @main_get_time(). **/
30 ucw_time_t now_seconds; /** [*] Current time in seconds since the epoch. **/
31 timestamp_t idle_time; /** [*] Total time in milliseconds spent by waiting for events. **/
32 uns shutdown; /** [*] Setting this to nonzero forces the @main_loop() function to terminate. **/
38 uns poll_table_obsolete;
40 struct pollfd *poll_table;
41 struct main_timer **timer_table; /* Growing array containing the heap of timers */
44 struct main_context *main_new(void);
45 void main_delete(struct main_context *m);
46 struct main_context *main_switch_context(struct main_context *m);
47 struct main_context *main_current(void);
50 void main_cleanup(void);
54 * It will watch the provided objects and call callbacks.
55 * Terminates when someone sets <<var_main_shutdown,`main_shutdown`>>
56 * to nonzero, when all <<hook,hooks>> return
57 * <<enum_main_hook_return,`HOOK_DONE`>> or at last one <<hook,hook>>
58 * returns <<enum_main_hook_return,`HOOK_SHUTDOWN`>>.
62 void main_debug_context(struct main_context *m);
67 main_debug_context(main_current());
75 * This part allows you to get the current time and request
76 * to have your function called when the time comes.
79 static inline timestamp_t
82 return main_current()->now;
85 static inline ucw_time_t
86 main_get_now_seconds(void)
88 return main_current()->now_seconds;
94 main_current()->shutdown = 1;
98 * This is a description of a timer.
99 * You fill in a handler function, any user-defined data you wish to pass
100 * to the handler, and then you invoke @timer_add().
102 * The handler() function must either call @timer_del() to delete the timer,
103 * or call @timer_add() with a different expiration time.
109 void (*handler)(struct main_timer *tm); /* [*] Function to be called when the timer expires. */
110 void *data; /* [*] Data for use by the handler */
114 * Adds a new timer into the mainloop to be watched and called
115 * when it expires. It can also be used to modify an already running
116 * timer. It is permitted (and usual) to call this function from the
117 * timer's handler itself if you want the timer to trigger again.
119 * The @expire parameter is absolute, just add <<var_main_now,`main_now`>> if you need a relative timer.
121 void timer_add(struct main_timer *tm, timestamp_t expires);
123 * Removes a timer from the active ones. It is permitted (and usual) to call
124 * this function from the timer's handler itself if you want to deactivate
127 void timer_del(struct main_timer *tm);
130 * Forces refresh of <<var_main_now,`main_now`>>. You do not usually
131 * need to call this, since it is called every time the loop polls for
132 * changes. It is here if you need extra precision or some of the
133 * hooks takes a long time.
135 void main_get_time(void);
139 * Activity on file descriptors
140 * ----------------------------
142 * You can let the mainloop watch over a set of file descriptors
145 * It supports two ways of use. With the first one, you provide
146 * low-level handlers for reading and writing (`read_handler` and
147 * `write_handler`). They will be called every time the file descriptor
148 * is ready to be read from or written to.
150 * Return non-zero if you want to get the handler called again right now (you
151 * handled a block of data and expect more). If you return `0`, the hook will
152 * be called again in the next iteration, if it is still ready to be read/written.
154 * This way is suitable for listening sockets, interactive connections, where
155 * you need to parse everything that comes right away and similar cases.
157 * The second way is to ask mainloop to read or write a buffer of data. You
158 * provide a `read_done` or `write_done` handler respectively and call @file_read()
159 * or @file_write(). This is handy for data connections where you need to transfer
160 * data between two endpoints or for binary connections where the size of message
161 * is known in advance.
163 * It is possible to combine both methods, but it may be tricky to do it right.
165 * Both ways use `error_handler` to notify you about errors.
169 * If you want mainloop to watch a file descriptor, fill at last `fd` into this
170 * structure. To get any useful information from the mainloop, provide some handlers
173 * After that, insert it into the mainloop by calling @file_add().
177 int fd; /* [*] File descriptor */
178 int (*read_handler)(struct main_file *fi); /* [*] To be called when ready for reading/writing; must call file_chg() afterwards */
179 int (*write_handler)(struct main_file *fi);
180 void (*error_handler)(struct main_file *fi, int cause); /* [*] Handler to call on errors */
181 void *data; /* [*] Data for use by the handlers */
182 byte *rbuf; /* Read/write pointers for use by file_read/write */
186 void (*read_done)(struct main_file *fi); /* [*] Called when file_read is finished; rpos < rlen if EOF */
187 void (*write_done)(struct main_file *fi); /* [*] Called when file_write is finished */
188 struct main_timer timer;
189 struct pollfd *pollfd;
193 * Specifies when or why an error happened. This is passed to the error handler.
194 * `errno` is still set to the original source of error. The only exception
195 * is `MFERR_TIMEOUT`, in which case `errno` is not set and the only possible
196 * cause of it is timeout on the file descriptor (see @file_set_timeout).
198 enum main_file_err_cause {
205 * Inserts a <<struct_main_file,`main_file`>> structure into the mainloop to be
206 * watched for activity. You can call this at any time, even inside a handler
207 * (of course for a different file descriptor than the one of the handler).
209 void file_add(struct main_file *fi);
211 * Tells the mainloop the file has changed its state. Call it whenever you
212 * change any of the handlers.
214 * Can be called only on active files (only the ones added by @file_add()).
216 void file_chg(struct main_file *fi);
218 * Removes a file from the watched set. You have to call this on closed files
219 * too, since the mainloop does not handle close in any way.
221 * Can be called from a handler.
223 void file_del(struct main_file *fi);
225 * Asks the mainloop to read @len bytes of data from @fi into @buf.
226 * It cancels any previous unfinished read requested this way and overwrites
229 * When the read is done, read_done() handler is called. If an EOF occurred,
230 * `rpos < rlen` (eg. not all data were read).
232 * Can be called from a handler.
234 * You can use a call with zero @len to cancel current read, but all read data
235 * will be thrown away.
237 void file_read(struct main_file *fi, void *buf, uns len);
239 * Requests that the mainloop writes @len bytes of data from @buf to @fi.
240 * Cancels any previous unfinished write and overwrites `write_handler`.
242 * When it is written, write_done() handler is called.
244 * Can be called from a handler.
246 * If you call it with zero @len, it will cancel the previous write, but note
247 * some data may already be written.
249 void file_write(struct main_file *fi, void *buf, uns len);
251 * Sets a timer for a file @fi. If the timer is not overwritten or disabled
252 * until @expires, the file timeouts and error_handler() is called with
253 * <<enum_main_file_err_cause,`MFERR_TIMEOUT`>>.
255 * The mainloop does not disable or reset it, when something happens, it just
256 * bundles a timer with the file. If you want to watch for inactivity, it is
257 * your task to reset it whenever your handler is called.
259 * The @expires parameter is absolute (add <<var_main_now,`main_now`>> if you
260 * need relative). The call and overwrites previously set timeout. Value of `0`
261 * disables the timeout (the <<enum_main_file_err_cause,`MFERR_TIMEOUT`>> will
264 * The use-cases for this are mainly sockets or pipes, when:
266 * - You want to drop inactive connections (no data come or go for a given time, not
267 * incomplete messages).
268 * - You want to enforce answer in a given time (for example authentication).
269 * - You give maximum time for a whole connection.
271 void file_set_timeout(struct main_file *fi, timestamp_t expires);
273 * Closes all file descriptors known to mainloop. Often used between fork()
276 void file_close_all(void);
283 * The hooks are called whenever the mainloop perform an iteration.
284 * You can shutdown the mainloop from within them or request an iteration
285 * to happen without sleeping (just poll, no waiting for events).
289 * A hook. It contains the function to call and some user data.
291 * The handler() must return one value from
292 * <<enum_main_hook_return,`main_hook_return`>>.
294 * Fill with the hook and data and pass it to @hook_add().
298 int (*handler)(struct main_hook *ho); /* [*] Hook function; returns HOOK_xxx */
299 void *data; /* [*] For use by the handler */
303 * Return value of the hook handler().
304 * Specifies what should happen next.
306 * - `HOOK_IDLE` -- Let the loop sleep until something happens, call after that.
307 * - `HOOK_RETRY` -- Force the loop to perform another iteration without sleeping.
308 * This will cause calling of all the hooks again soon.
309 * - `HOOK_DONE` -- The loop will terminate if all hooks return this.
310 * - `HOOK_SHUTDOWN` -- Shuts down the loop.
312 enum main_hook_return {
320 * Inserts a new hook into the loop.
321 * The hook will be scheduled at least once before next sleep.
322 * May be called from inside a hook handler too.
324 void hook_add(struct main_hook *ho);
326 * Removes an existing hook from the loop.
327 * May be called from inside a hook handler (to delete itself or other hook).
329 void hook_del(struct main_hook *ho);
336 * The main loop can watch child processes and notify you,
337 * when some of them terminates.
341 * Description of a watched process.
342 * You fill in the handler() and `data`.
343 * The rest is set with @process_fork().
345 struct main_process {
347 int pid; /* Process id (0=not running) */
348 int status; /* Exit status (-1=fork failed) */
349 char status_msg[EXIT_STATUS_MSG_SIZE];
350 void (*handler)(struct main_process *mp); /* [*] Called when the process exits; process_del done automatically */
351 void *data; /* [*] For use by the handler */
355 * Asks the mainloop to watch this process.
356 * As it is done automatically in @process_fork(), you need this only
357 * if you removed the process previously by @process_del().
359 void process_add(struct main_process *mp);
361 * Removes the process from the watched set. This is done
362 * automatically, when the process terminates, so you need it only
363 * when you do not want to watch a running process any more.
365 void process_del(struct main_process *mp);
367 * Forks and fills the @mp with information about the new process.
369 * If the fork() succeeds, it:
371 * - Returns 0 in the child.
372 * - Returns 1 in the parent and calls @process_add() on it.
374 * In the case of unsuccessful fork(), it:
376 * - Fills in the `status_msg` and sets `status` to -1.
377 * - Calls the handler() as if the process terminated.
380 int process_fork(struct main_process *mp);