2 * UCW Library -- Main Loop
4 * (c) 2004--2011 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"
22 * First of all, let us take a look at the basic operations with main loop contexts.
25 /** The main loop context **/
27 timestamp_t now; /** [*] Current time in milliseconds since the UNIX epoch. See @main_get_time(). **/
28 ucw_time_t now_seconds; /** [*] Current time in seconds since the epoch. **/
29 timestamp_t idle_time; /** [*] Total time in milliseconds spent by waiting for events. **/
30 uns shutdown; /** [*] Setting this to nonzero forces the @main_loop() function to terminate. **/
32 clist file_active_list;
38 #ifdef CONFIG_UCW_EPOLL
39 int epoll_fd; /* File descriptor used for epoll */
40 struct epoll_event *epoll_events;
41 clist file_recalc_list;
43 uns poll_table_obsolete;
44 struct pollfd *poll_table;
45 struct main_file **poll_file_table;
47 struct main_timer **timer_table; /* Growing array containing the heap of timers */
48 sigset_t want_signals;
51 struct main_file *sig_pipe_file;
52 struct main_signal *sigchld_handler;
55 struct main_context *main_new(void); /** Create a new context. **/
58 * Delete a context, assuming it does have any event handlers attached. Does nothing if @m is NULL.
59 * It is allowed to call @main_delete() from a hook function of the same context, but you must
60 * never return to the main loop -- e.g., you can exit() the process instead.
62 void main_delete(struct main_context *m);
65 * Delete a context. If there are any event handlers attached, they are deactivated
66 * (but the responsibility to free the memory there were allocated from lies upon you).
67 * If there are any file handlers, the corresponding file descriptors are closed.
69 void main_destroy(struct main_context *m);
71 /** Switch the current context of the calling thread. Returns the previous current context. **/
72 struct main_context *main_switch_context(struct main_context *m);
74 /** Return the current context. Dies if there is none or if the context has been deleted. **/
75 struct main_context *main_current(void);
77 /** Initialize the main loop module and create a top-level context. **/
80 /** Deinitialize the main loop module, calling @main_delete() on the top-level context. **/
81 void main_cleanup(void);
84 * Deinitialize the main loop module, calling @main_destroy() on the top-level context.
85 * This is especially useful in a freshly forked-off child process.
87 void main_teardown(void);
90 * Start the event loop on the current context.
91 * It will watch the provided objects and call callbacks.
92 * Terminates when someone sets <<var_main_shutdown,`main_shutdown`>>
93 * to nonzero, when all <<hook,hooks>> return
94 * <<enum_main_hook_return,`HOOK_DONE`>> or at last one <<hook,hook>>
95 * returns <<enum_main_hook_return,`HOOK_SHUTDOWN`>>.
99 /** Ask the main loop to terminate at the nearest occasion. **/
100 static inline void main_shut_down(void)
102 main_current()->shutdown = 1;
105 /** Show the current state of a given context (use @main_debug() for the current context). **/
106 void main_debug_context(struct main_context *m);
111 main_debug_context(main_current());
119 * The event loop provides the current time, measured as a 64-bit number
120 * of milliseconds since the system epoch (represented in the type `timestamp_t`).
122 * You can also register timers, which call a handler function at a given moment.
123 * The handler function must either call @timer_del() to delete the timer, or call
124 * @timer_add() with a different expiration time.
128 * Get the current timestamp cached in the current context. It is refreshed in every
129 * iteration of the event loop, or explicitly by calling @main_get_time().
131 static inline timestamp_t main_get_now(void)
133 return main_current()->now;
136 /** An analog of @main_get_now() returning the number of seconds since the system epoch. **/
137 static inline ucw_time_t main_get_now_seconds(void)
139 return main_current()->now_seconds;
143 * This is a description of a timer.
144 * You define the handler function and possibly user-defined data you wish
145 * to pass to the handler, and then you invoke @timer_add().
151 void (*handler)(struct main_timer *tm); /* [*] Function to be called when the timer expires. */
152 void *data; /* [*] Data for use by the handler */
156 * Add a new timer into the main loop to be watched and called
157 * when it expires. It can also be used to modify an already running
158 * timer. It is permitted (and usual) to call this function from the
159 * timer's handler itself if you want the timer to trigger again.
161 * The @expire parameter is absolute, use @timer_add_rel() for a relative version.
163 void timer_add(struct main_timer *tm, timestamp_t expires);
165 /** Like @timer_add(), but the expiration time is relative to the current time. **/
166 void timer_add_rel(struct main_timer *tm, timestamp_t expires_delta);
169 * Removes a timer from the active ones. It is permitted (and common) to call
170 * this function from the timer's handler itself if you want to deactivate
173 void timer_del(struct main_timer *tm);
176 * Forces refresh of the current timestamp cached in the active context.
177 * You usually do not need to call this, since it is called every time the
178 * loop polls for events. It is here if you need extra precision or some of the
179 * hooks takes a long time.
181 void main_get_time(void);
185 * Activity on file descriptors
186 * ----------------------------
188 * You can ask the main loop to watch a set of file descriptors for activity.
189 * (This is a generalization of the select() and poll() system calls. Internally,
190 * it uses either poll() or the more efficient epoll().)
192 * You create a <<struct_main_file,`struct main_file`>>, fill in a file descriptor
193 * and pointers to handler functions to be called when the descriptor becomes
194 * ready for reading and/or writing, and call @file_add(). When you need to
195 * modify the handlers (e.g., to set them to NULL if you are no longer interested
196 * in a given event), you should call @file_chg() to notify the main loop about
199 * From within the handler functions, you are allowed to call @file_chg() and even
202 * The return value of a handler function should be either `HOOK_RETRY` or `HOOK_IDLE`.
203 * `HOOK_RETRY` signals that the function would like to consume more data immediately
204 * (i.e., it wants to be called again soon, but the event loop can postpone it after
205 * processing other events to avoid starvation). `HOOK_IDLE` tells that the handler
206 * wants to be called when the descriptor becomes ready again.
208 * For backward compatibility, 0 can be used instead of `HOOK_IDLE` and 1 for `HOOK_RETRY`.
210 * If you want to read/write fixed-size blocks of data asynchronously, the
211 * <<blockio,Asynchronous block I/O>> interface could be more convenient.
215 * This structure describes a file descriptor to be watched and the handlers
216 * to be called when the descriptor is ready for reading and/or writing.
220 int fd; /* [*] File descriptor */
221 int (*read_handler)(struct main_file *fi); /* [*] To be called when ready for reading/writing; must call file_chg() afterwards */
222 int (*write_handler)(struct main_file *fi);
223 void *data; /* [*] Data for use by the handlers */
225 #ifdef CONFIG_UCW_EPOLL
226 uns last_want_events;
228 struct pollfd *pollfd;
233 * Insert a <<struct_main_file,`main_file`>> structure into the main loop to be
234 * watched for activity. You can call this at any time, even inside a handler
235 * (of course for a different file descriptor than the one of the handler).
237 * The file descriptor is automatically set to the non-blocking mode.
239 void file_add(struct main_file *fi);
241 * Tell the main loop that the file structure has changed. Call it whenever you
242 * change any of the handlers.
244 * Can be called only on active files (only the ones added by @file_add()).
246 void file_chg(struct main_file *fi);
248 * Removes a file from the watched set. If you want to close a descriptor,
249 * please use this function first.
251 * Can be called from a handler.
253 void file_del(struct main_file *fi);
257 * Asynchronous block I/O
258 * ----------------------
260 * If you are reading or writing fixed-size blocks of data, you can let the
261 * block I/O interface handle the boring routine of handling partial reads
262 * and writes for you.
264 * You just create <<struct_main_block_io,`struct main_block_io`>> and call
265 * @block_io_add() on it, which sets up some `main_file`s internally.
266 * Then you can just call @block_io_read() or @block_io_write() to ask for
267 * reading or writing of a given block. When the operation is finished,
268 * your handler function is called.
270 * Additionally, the block I/O is equipped with a timer, which can be used
271 * to detect communication timeouts. The timer is not touched internally
272 * (except that it gets added and deleted at the right places), feel free
273 * to adjust it from your handler functions by @block_io_set_timeout().
274 * When the timer expires, the error handler is automatically called with
278 /** The block I/O structure. **/
279 struct main_block_io {
280 struct main_file file;
281 byte *rbuf; /* Read/write pointers for use by file_read/write */
285 void (*read_done)(struct main_block_io *bio); /* [*] Called when file_read is finished; rpos < rlen if EOF */
286 void (*write_done)(struct main_block_io *bio); /* [*] Called when file_write is finished */
287 void (*error_handler)(struct main_block_io *bio, int cause); /* [*] Handler to call on errors */
288 struct main_timer timer;
289 void *data; /* [*] Data for use by the handlers */
292 /** Activate a block I/O structure. **/
293 void block_io_add(struct main_block_io *bio, int fd);
295 /** Deactivate a block I/O structure. **/
296 void block_io_del(struct main_block_io *bio);
299 * Specifies when or why an error happened. This is passed to the error handler.
300 * `errno` is still set to the original source of error. The only exception
301 * is `BIO_ERR_TIMEOUT`, in which case `errno` is not set and the only possible
302 * cause of it is timeout of the timer associated with the block_io
303 * (see @block_io_set_timeout()).
305 enum block_io_err_cause {
312 * Ask the main loop to read @len bytes of data from @bio into @buf.
313 * It cancels any previous unfinished read requested in this way.
315 * When the read is done, the read_done() handler is called. If an EOF occurred,
316 * `rpos < rlen` (eg. not all data were read).
318 * Can be called from a handler.
320 * You can use a call with zero @len to cancel the current read, but all read data
321 * will be thrown away.
323 void block_io_read(struct main_block_io *bio, void *buf, uns len);
326 * Request that the main loop writes @len bytes of data from @buf to @bio.
327 * Cancels any previous unfinished write and overwrites `write_handler`.
329 * When it is written, the write_done() handler is called.
331 * Can be called from a handler.
333 * If you call it with zero @len, it will cancel the previous write, but note
334 * that some data may already be written.
336 void block_io_write(struct main_block_io *bio, void *buf, uns len);
339 * Sets a timer for a file @bio. If the timer is not overwritten or disabled
340 * until @expires_delta milliseconds, the file timeouts and error_handler() is called with
341 * <<enum_block_io_err_cause,`BIO_ERR_TIMEOUT`>>. A value of `0` stops the timer.
343 * Previous setting of the timeout on the same file will be overwritten.
345 * The use-cases for this are mainly sockets or pipes, when:
347 * - You want to drop inactive connections (no data comes in or out for a given time, not
348 * incomplete messages).
349 * - You want to enforce answer in a given time (for example authentication).
350 * - Watching maximum time for a whole connection.
352 void block_io_set_timeout(struct main_block_io *bio, timestamp_t expires_delta);
359 * The hooks are called whenever the main loop performs an iteration.
360 * You can shutdown the main loop from within them or request an iteration
361 * to happen without sleeping (just poll, no waiting for events).
365 * A hook. It contains the function to call and some user data.
367 * The handler() must return one value from
368 * <<enum_main_hook_return,`main_hook_return`>>.
370 * Fill with the hook and data and pass it to @hook_add().
374 int (*handler)(struct main_hook *ho); /* [*] Hook function; returns HOOK_xxx */
375 void *data; /* [*] For use by the handler */
379 * Return value of the hook handler().
380 * Specifies what should happen next.
382 * - `HOOK_IDLE` -- Let the loop sleep until something happens, call after that.
383 * - `HOOK_RETRY` -- Force the loop to perform another iteration without sleeping.
384 * This will cause calling of all the hooks again soon.
385 * - `HOOK_DONE` -- The loop will terminate if all hooks return this.
386 * - `HOOK_SHUTDOWN` -- Shuts down the loop.
388 enum main_hook_return {
396 * Inserts a new hook into the loop.
397 * The hook will be scheduled at least once before next sleep.
398 * May be called from inside a hook handler too.
400 void hook_add(struct main_hook *ho);
402 * Removes an existing hook from the loop.
403 * May be called from inside a hook handler (to delete itself or other hook).
405 void hook_del(struct main_hook *ho);
412 * The main loop can watch child processes and notify you,
413 * when some of them terminates.
417 * Description of a watched process.
418 * You fill in the handler() and `data`.
419 * The rest is set with @process_fork().
421 struct main_process {
423 int pid; /* Process id (0=not running) */
424 int status; /* Exit status (-1=fork failed) */
425 char status_msg[EXIT_STATUS_MSG_SIZE];
426 void (*handler)(struct main_process *mp); /* [*] Called when the process exits; process_del done automatically */
427 void *data; /* [*] For use by the handler */
431 * Asks the main loop to watch this process.
432 * As it is done automatically in @process_fork(), you need this only
433 * if you removed the process previously by @process_del().
435 void process_add(struct main_process *mp);
437 * Removes the process from the watched set. This is done
438 * automatically, when the process terminates, so you need it only
439 * when you do not want to watch a running process any more.
441 void process_del(struct main_process *mp);
443 * Forks and fills the @mp with information about the new process.
445 * If the fork() succeeds, it:
447 * - Returns 0 in the child.
448 * - Returns 1 in the parent and calls @process_add() on it.
450 * In the case of unsuccessful fork(), it:
452 * - Fills in the `status_msg` and sets `status` to -1.
453 * - Calls the handler() as if the process terminated.
456 int process_fork(struct main_process *mp);
463 void (*handler)(struct main_signal *ms);
467 void signal_add(struct main_signal *ms);
468 void signal_del(struct main_signal *ms);