3 * $Id: sel.h,v 1.8 2001/06/22 19:35:58 mdw Exp $
5 * I/O multiplexing support
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of the mLib utilities library.
14 * mLib is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU Library General Public License as
16 * published by the Free Software Foundation; either version 2 of the
17 * License, or (at your option) any later version.
19 * mLib is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU Library General Public License for more details.
24 * You should have received a copy of the GNU Library General Public
25 * License along with mLib; if not, write to the Free
26 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
30 /*----- Revision history --------------------------------------------------*
33 * Revision 1.8 2001/06/22 19:35:58 mdw
34 * Fix a large number of bugs.
36 * Revision 1.7 1999/12/10 23:42:04 mdw
37 * Change header file guard names.
39 * Revision 1.6 1999/08/31 17:42:22 mdw
40 * New function `sel_force' to force a descriptor to be `selected'.
42 * Revision 1.5 1999/08/19 18:30:26 mdw
43 * Implement hooks for foreign select-using systems (currently not well
46 * Revision 1.4 1999/05/22 13:39:15 mdw
47 * Change spelling of `multiplexor'. ;-)
49 * Revision 1.3 1999/05/17 20:36:36 mdw
50 * Make the selector type symbols an enumeration rather than a bunch of
53 * Revision 1.2 1999/05/15 10:33:32 mdw
54 * Fix copyright notices.
56 * Revision 1.1 1999/05/14 21:01:15 mdw
57 * Integrated `select' handling bits from the background resolver project.
68 /*----- Theory lesson -----------------------------------------------------*
70 * Things which are expecting to do I/O or go off at a certain time are
71 * called `selectors'. There are two types of selectors: `file selectors'
72 * wait patiently for a file to become readable or writable; `timeout
73 * selectors' wait for a certain amount of time to elapse. There is also a
74 * `multiplexor' which copes with managing all of this stuff.
76 * Multiplexors aren't actually very interesting. You initialize them with
77 * @sel_init@, and then add and remove selectors as you go. When you want to
78 * wait for something to happen, call @sel_select@.
80 * A file selector can *either* read *or* write. It can't do both. This is
81 * because you quite often want to read a socket but not write it; during
82 * those times you don't want to write, you just don't install a write
85 * File selectors are called when their files are available for reading or
86 * writing as appropriate, and given their file descriptor, the state of the
87 * file, and a pointer that was registered along with the selector.
89 * File selectors are set up in two phases. First, they're `initialized'
90 * with @sel_initfile@. An initialized file selector doesn't do anything.
91 * It needs to be added to a multiplexor using `sel_addfile'. It can later
92 * be removed using `sel_rmfile'. You can carry on adding and removing as
93 * you wish. Just don't try adding it twice in a row.
95 * Timeout selectors are called at a certain time. (Actually, they're called
96 * *after* a certain time.) There's no separate initialization step with
97 * timouts: you just add them and they work. If you decide you don't want a
98 * timeout to go off, then you just remove it. (Adding and removing the
99 * *same* timeout isn't something you do very often. You usually use a
100 * different expiry time each time.)
103 /*----- Header files ------------------------------------------------------*/
105 #include <sys/types.h>
106 #include <sys/time.h>
109 /*----- Data structures ---------------------------------------------------*/
111 /* --- A multiplexor --- *
113 * The files are sorted in reverse order of file descriptor number; the
114 * timers are in normal order of occurrence. Thus, the interesting one
115 * is always at the front of the list.
119 SEL_READ, /* File is ready to read */
120 SEL_WRITE, /* File is ready to write */
121 SEL_EXC, /* Something odd has happened */
122 SEL_MODES /* Number of modes available */
125 typedef struct sel_state {
126 struct sel_file *files[SEL_MODES]; /* Lists of interesting files */
127 struct sel_timer *timers; /* List of timers */
128 struct sel_hook *hooks; /* List of hook functions applied */
129 fd_set fd[SEL_MODES]; /* Quick reference table for files */
130 struct sel_args *args; /* Pointer to arguments */
133 /* --- Listening for a file --- */
135 typedef struct sel_file {
136 struct sel_file *next; /* Next file in the list */
137 struct sel_file *prev; /* Previous file in the list */
138 struct sel_state *s; /* Pointer to select multiplexor */
139 int fd; /* File descriptor */
140 unsigned mode; /* Interesting event for file */
141 void (*func)(int /*fd*/, unsigned /*mode*/, void */*p*/); /* Handler */
142 void *p; /* Argument for the handler */
143 struct sel_pendfile *pend; /* Pending file information */
146 /* --- Waiting for a timeout --- */
148 typedef struct sel_timer {
149 struct sel_timer *next; /* Next timer in the list */
150 struct sel_timer *prev; /* Previous timer in the list */
151 struct timeval tv; /* Real time when timer should go */
152 void (*func)(struct timeval */*tv*/, void */*p*/); /* Handler function */
153 void *p; /* Argument for the handler */
154 struct sel_pendtimer *pend; /* Pending timer information */
157 /* --- A select argument block --- */
159 typedef struct sel_args {
160 int maxfd; /* Highest-numbered file */
161 fd_set fd[SEL_MODES]; /* Bit flags for all the files */
162 struct timeval tv, *tvp; /* Time to return */
163 struct timeval now; /* Current time */
166 /* --- A selector hook --- *
168 * The hooks are called (in arbitrary order) on each select.
171 typedef void (*sel_hookfn)(sel_state */*s*/,
175 typedef struct sel_hook {
176 struct sel_hook *next; /* Next hook in the list */
177 struct sel_hook *prev; /* Previous hook in the list */
178 sel_hookfn before, after; /* Hook functions */
179 void *p; /* Argument for the hook functions */
182 /*----- Functions provided ------------------------------------------------*/
184 /* --- @sel_init@ --- *
186 * Arguments: @sel_state *s@ = pointer to a state block to initialize
190 * Use: Initializes a select state block.
193 extern void sel_init(sel_state */*s*/);
195 /* --- @sel_initfile@ --- *
197 * Arguments: @sel_state *s@ = select state to attach to
198 * @sel_file *f@ = pointer to a file block to initialize
199 * @int fd@ = the file descriptor to listen to
200 * @unsigned mode@ = what to listen for
201 * @void (*func)(int fd, unsigned mode, void *p)@ = handler
202 * @void *p@ = argument to pass to handler
206 * Use: Initializes a file block ready for use. The file block
207 * isn't added to the list of things to do until a call to
211 extern void sel_initfile(sel_state */*s*/, sel_file */*f*/,
212 int /*fd*/, unsigned /*mode*/,
213 void (*/*func*/)(int /*fd*/,
218 /* --- @sel_addfile@ --- *
220 * Arguments: @sel_file *f@ = pointer to a file block
224 * Use: Adds a file block into the list of things to listen to.
227 extern void sel_addfile(sel_file */*f*/);
229 /* --- @sel_rmfile@ --- *
231 * Arguments: @sel_file *f@ = pointer to a file block
235 * Use: Removes a file block from the list of things to listen to.
238 extern void sel_rmfile(sel_file */*f*/);
240 /* --- @sel_force@ --- *
242 * Arguments: @sel_file *f@ = pointer to file selector
246 * Use: Forces a file selector to be considered ready. This is only
247 * useful during a call to @sel_select@. Of particular use is
248 * forcing a write selector when there's something interesting
252 extern void sel_force(sel_file */*f*/);
254 /* --- @sel_addtimer@ --- *
256 * Arguments: @sel_state *s@ = pointer to a state block
257 * @sel_timer *t@ = pointer to a timer block
258 * @struct timeval *tv@ = pointer to time to activate
259 * @void *p@ = argument for handler function
263 * Use: Registers and sets up a timer.
266 extern void sel_addtimer(sel_state */*s*/, sel_timer */*t*/,
267 struct timeval */*tv*/,
268 void (*/*func*/)(struct timeval */*tv*/,
272 /* --- @sel_rmtimer@ --- *
274 * Arguments: @sel_timer *t@ = pointer to timer block
278 * Use: Removes a timer from the list of timers.
281 extern void sel_rmtimer(sel_timer */*t*/);
283 /* --- @sel_addhook@ --- *
285 * Arguments: @sel_state *s@ = pointer to state block
286 * @sel_hook *h@ = pointer to hook block
287 * @sel_hookfn before, after@ = hook functions
288 * @void *p@ = pointer argument to pass to hook functions
292 * Use: Registers hook functions to be called on each select call.
295 extern void sel_addhook(sel_state */*s*/, sel_hook */*h*/,
296 sel_hookfn /*before*/, sel_hookfn /*after*/,
299 /* --- @sel_rmhook@ --- *
301 * Arguments: @sel_hook *h@ = pointer to hook block
305 * Use: Removes hook functions.
308 extern void sel_rmhook(sel_hook */*h*/);
310 /* --- @sel_fdmerge@ --- *
312 * Arguments: @fd_set *dest@ = destination FD set
313 * @fd_set *fd@ = pointer to set to merge
314 * @int maxfd@ = highest numbered descriptor in @fd@ + 1
316 * Returns: Actual highest numbered descriptor.
318 * Use: Merges file descriptor sets, and returns an accurate @maxfd@
322 extern int sel_fdmerge(fd_set */*dest*/, fd_set */*fd*/, int /*maxfd*/);
324 /* --- @sel_select@ --- *
326 * Arguments: @sel_state *s@ = pointer to state block
328 * Returns: Zero if all OK, -1 on error.
330 * Use: Does a @select@ call (or equivalent @poll@).
333 extern int sel_select(sel_state */*s*/);
335 /*----- That's all, folks -------------------------------------------------*/