2 * UCW Library -- Main Loop
4 * (c) 2004--2005 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
31 * This part allows you to get the current time and request
32 * to have your function called when the time comes.
35 extern timestamp_t main_now; /** Current time in milliseconds since the UNIX epoch. See @main_get_time(). **/
36 extern ucw_time_t main_now_seconds; /** Current time in seconds since the epoch. **/
37 extern clist main_timer_list, main_file_list, main_hook_list, main_process_list;
40 * This is a description of a timer.
41 * You fill in a handler function, any user-defined data you wish to pass
42 * to the handler, and then you invoke @timer_add().
44 * The handler() function must either call @timer_del() to delete the timer,
45 * or call @timer_add() with a different expiration time.
50 void (*handler)(struct main_timer *tm); /* [*] Function to be called when the timer expires. */
51 void *data; /* [*] Data for use by the handler */
55 * Adds a new timer into the mainloop to be watched and called
56 * when it expires. It can also be used to modify an already running
57 * timer. It is permitted (and usual) to call this function from the
58 * timer's handler itself if you want the timer to trigger again.
60 * The @expire parameter is absolute, just add <<var_main_now,`main_now`>> if you need a relative timer.
62 void timer_add(struct main_timer *tm, timestamp_t expires);
64 * Removes a timer from the active ones. It is permitted (and usual) to call
65 * this function from the timer's handler itself if you want to deactivate
68 void timer_del(struct main_timer *tm);
71 * Forces refresh of <<var_main_now,`main_now`>>. You do not usually
72 * need to call this, since it is called every time the loop polls for
73 * changes. It is here if you need extra precision or some of the
74 * hooks takes a long time.
76 void main_get_time(void);
80 * Activity on file descriptors
81 * ----------------------------
83 * You can let the mainloop watch over a set of file descriptors
86 * It supports two ways of use. With the first one, you provide
87 * low-level handlers for reading and writing (`read_handler` and
88 * `write_handler`). They will be called every time the file descriptor
89 * is ready to be read or written.
91 * Return non-zero if you want to get the handler called again right now (you
92 * handled a block of data and expect more). If you return `0`, it will
93 * be called again in the next iteration, if it is still ready to be read/written.
95 * This way is suitable for listening sockets, interactive connections, where
96 * you need to parse everything that comes right away and similar.
98 * The second way is to ask mainloop to read or write a buffer of data. You
99 * provide a `read_done` or `write_done` handler respectively and call @file_read()
100 * or @file_write(). This is handy for data connections where you need to transfer
101 * data between two endpoints or for binary connections where the size of message
104 * It is possible to combine both methods, but it may be tricky to do it right.
106 * Both ways use `error_handler` to notify you about errors.
110 * If you want mainloop to watch a file descriptor, fill at last `fd` into this
111 * structure. To get any useful information from the mainloop, provide some handlers
114 * After that, insert it into the mainloop by calling @file_add().
118 int fd; /* [*] File descriptor */
119 int (*read_handler)(struct main_file *fi); /* [*] To be called when ready for reading/writing; must call file_chg() afterwards */
120 int (*write_handler)(struct main_file *fi);
121 void (*error_handler)(struct main_file *fi, int cause); /* [*] Handler to call on errors */
122 void *data; /* [*] Data for use by the handlers */
123 byte *rbuf; /* Read/write pointers for use by file_read/write */
127 void (*read_done)(struct main_file *fi); /* [*] Called when file_read is finished; rpos < rlen if EOF */
128 void (*write_done)(struct main_file *fi); /* [*] Called when file_write is finished */
129 struct main_timer timer;
130 struct pollfd *pollfd;
134 * Specifies when or why an error happened. This is passed to the error handler.
135 * `errno` is still set to the original source of error. The only exception
136 * is `MFERR_TIMEOUT`, in which case `errno` is not set and the only possible
137 * cause of it is timeout on the file descriptor (see @file_set_timeout).
139 enum main_file_err_cause {
146 * Inserts a <<struct_main_file,`main_file`>> structure into the mainloop to be
147 * watched for activity. You can call this at any time, even inside a handler
148 * (of course for a different file descriptor than the one of the handler).
150 void file_add(struct main_file *fi);
152 * Tells the mainloop the file has changed it's state. Call it whenever you
153 * change any of the handlers.
155 void file_chg(struct main_file *fi);
157 * Removes a file from the watched set. You have to call this on closed files
158 * too, since the mainloop does not handle close in any way.
160 * Can be called from a handler.
162 void file_del(struct main_file *fi);
164 * Asks the mainloop to read @len bytes of data from @fi into @buf.
165 * It cancels any previous unfinished read requested this way and overwrites
168 * When the read is done, read_done() handler is called. If an EOF occurred,
169 * `rpos < rlen` (eg. not all data were read).
171 * Can be called from a handler.
173 * You can use a call with zero @len to cancel current read, but all read data
174 * will be thrown away.
176 void file_read(struct main_file *fi, void *buf, uns len);
178 * Requests that the mainloop writes @len bytes of data from @buf to @fi.
179 * Cancels any previous unfinished write and overwrites `write_handler`.
181 * When it is written, write_done() handler is called.
183 * Can be called from a handler.
185 * If you call it with zero @len, it will cancel the previous write, but note
186 * some data may already be written.
188 void file_write(struct main_file *fi, void *buf, uns len);
190 * Sets a timer for a file @fi. If the timer is not overwritten or disabled
191 * until @expires, the file timeouts and error_handler() is called with
192 * <<enum_main_file_err_cause,`MFERR_TIMEOUT`>>.
194 * The mainloop does not disable or reset it, when something happens, it just
195 * bundles a timer with the file. If you want to watch for inactivity, it is
196 * your task to reset it whenever your handler is called.
198 * The @expires parameter is absolute (add <<var_main_now,`main_now`>> if you
199 * need relative). The call and overwrites previously set timeout. Value of `0`
200 * disables the timeout (the <<enum_main_file_err_cause,`MFERR_TIMEOUT`>> will
203 * The use-cases for this are mainly sockets or pipes, when:
205 * - You want to drop inactive connections (no data com or go).
206 * - You want to enforce answer in given time (for example authentication).
207 * - You give maximum time for a whole connection.
209 void file_set_timeout(struct main_file *fi, timestamp_t expires);
211 * Closes all file descriptors known to mainloop. Often used between fork()
214 void file_close_all(void);
221 * The hooks are called whenever the mainloop perform an iteration.
222 * You can shutdown the mainloop from within them or request an iteration
223 * to happen without sleeping (just poll, no waiting for events).
227 * A hook. It contains the function to call and some user data.
229 * The handler() must return one value from
230 * <<enum_main_hook_return,`main_hook_return`>>.
232 * Fill with the hook and data and pass it to @hook_add().
236 int (*handler)(struct main_hook *ho); /* [*] Hook function; returns HOOK_xxx */
237 void *data; /* [*] For use by the handler */
241 * Return value of the hook handler().
242 * Specifies what should happen next.
244 * - `HOOK_IDLE` -- Let the loop sleep until something happens, call after that.
245 * - `HOOK_RETRY` -- Force the loop to perform another iteration without sleeping.
246 * This will cause calling of all the hooks again soon.
247 * - `HOOK_DONE` -- The loop will terminate if all hooks return this.
248 * - `HOOK_SHUTDOWN` -- Shuts down the loop.
250 enum main_hook_return {
258 * Inserts a new hook into the loop.
259 * May be called from inside a hook handler too.
261 void hook_add(struct main_hook *ho);
263 * Removes an existing hook from the loop.
264 * May be called from inside a hook handler (to delete itself or other hook).
266 void hook_del(struct main_hook *ho);
273 * The main loop can watch child processes and notify you,
274 * when some of them terminates.
278 * Description of a watched process.
279 * You fill in the handler() and `data`.
280 * The rest is set with @process_fork().
282 struct main_process {
284 int pid; /* Process id (0=not running) */
285 int status; /* Exit status (-1=fork failed) */
286 char status_msg[EXIT_STATUS_MSG_SIZE];
287 void (*handler)(struct main_process *mp); /* [*] Called when the process exits; process_del done automatically */
288 void *data; /* [*] For use by the handler */
292 * Asks the mainloop to watch this process.
293 * As it is done automatically in @process_fork(), you need this only
294 * if you removed the process previously by @process_del().
296 void process_add(struct main_process *mp);
298 * Removes the process from the watched set. This is done
299 * automatically, when the process terminates, so you need it only
300 * when you do not want to watch a running process any more.
302 void process_del(struct main_process *mp);
304 * Forks and fills the @mp with information about the new process.
306 * If the fork() succeeds, it:
308 * - Returns 0 in the child.
309 * - Returns 1 in the parent and calls @process_add() on it.
311 * In the case of unsuccessful fork(), it:
313 * - Fills in the `status_msg` and sets `status` to -1.
314 * - Calls the handler() as if the process terminated.
317 int process_fork(struct main_process *mp);
321 * Control of the mainloop
322 * -----------------------
324 * These functions control the mainloop as a whole.
327 extern uns main_shutdown; /** Setting this to nonzero forces the @main_loop() function to terminate. **/
328 void main_init(void); /** Initializes the mainloop structures. Call before any `*_add` function. **/
330 * Start the mainloop.
331 * It will watch the provided objects and call callbacks.
332 * Terminates when someone sets <<var_main_shutdown,`main_shutdown`>>
333 * to nonzero, when all <<hook,hooks>> return
334 * <<enum_main_hook_return,`HOOK_DONE`>> or at last one <<hook,hook>>
335 * returns <<enum_main_hook_return,`HOOK_SHUTDOWN`>>.
337 void main_loop(void);
338 void main_debug(void); /** Prints a lot of debug information about current status of the mainloop. **/