3 * $Id: sel.h,v 1.6 1999/08/31 17:42:22 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 1.6 1999/08/31 17:42:22 mdw
34 * New function `sel_force' to force a descriptor to be `selected'.
36 * Revision 1.5 1999/08/19 18:30:26 mdw
37 * Implement hooks for foreign select-using systems (currently not well
40 * Revision 1.4 1999/05/22 13:39:15 mdw
41 * Change spelling of `multiplexor'. ;-)
43 * Revision 1.3 1999/05/17 20:36:36 mdw
44 * Make the selector type symbols an enumeration rather than a bunch of
47 * Revision 1.2 1999/05/15 10:33:32 mdw
48 * Fix copyright notices.
50 * Revision 1.1 1999/05/14 21:01:15 mdw
51 * Integrated `select' handling bits from the background resolver project.
62 /*----- Theory lesson -----------------------------------------------------*
64 * Things which are expecting to do I/O or go off at a certain time are
65 * called `selectors'. There are two types of selectors: `file selectors'
66 * wait patiently for a file to become readable or writable; `timeout
67 * selectors' wait for a certain amount of time to elapse. There is also a
68 * `multiplexor' which copes with managing all of this stuff.
70 * Multiplexors aren't actually very interesting. You initialize them with
71 * @sel_init@, and then add and remove selectors as you go. When you want to
72 * wait for something to happen, call @sel_select@.
74 * A file selector can *either* read *or* write. It can't do both. This is
75 * because you quite often want to read a socket but not write it; during
76 * those times you don't want to write, you just don't install a write
79 * File selectors are called when their files are available for reading or
80 * writing as appropriate, and given their file descriptor, the state of the
81 * file, and a pointer that was registered along with the selector.
83 * File selectors are set up in two phases. First, they're `initialized'
84 * with @sel_initfile@. An initialized file selector doesn't do anything.
85 * It needs to be added to a multiplexor using `sel_addfile'. It can later
86 * be removed using `sel_rmfile'. You can carry on adding and removing as
87 * you wish. Just don't try adding it twice in a row.
89 * Timeout selectors are called at a certain time. (Actually, they're called
90 * *after* a certain time.) There's no separate initialization step with
91 * timouts: you just add them and they work. If you decide you don't want a
92 * timeout to go off, then you just remove it. (Adding and removing the
93 * *same* timeout isn't something you do very often. You usually use a
94 * different expiry time each time.)
97 /*----- Header files ------------------------------------------------------*/
99 #include <sys/types.h>
100 #include <sys/time.h>
103 /*----- Data structures ---------------------------------------------------*/
105 /* --- A multiplexor --- *
107 * The files are sorted in reverse order of file descriptor number; the
108 * timers are in normal order of occurrence. Thus, the interesting one
109 * is always at the front of the list.
113 SEL_READ
, /* File is ready to read */
114 SEL_WRITE
, /* File is ready to write */
115 SEL_EXC
, /* Something odd has happened */
116 SEL_MODES
/* Number of modes available */
119 typedef struct sel_state
{
120 struct sel_file
*files
[SEL_MODES
]; /* Lists of interesting files */
121 struct sel_timer
*timers
; /* List of timers */
122 struct sel_hook
*hooks
; /* List of hook functions applied */
123 fd_set fd
[SEL_MODES
]; /* Quick reference table for files */
124 struct sel_args
*args
; /* Pointer to arguments */
127 /* --- Listening for a file --- */
129 typedef struct sel_file
{
130 struct sel_file
*next
; /* Next file in the list */
131 struct sel_file
*prev
; /* Previous file in the list */
132 struct sel_state
*s
; /* Pointer to select multiplexor */
133 int fd
; /* File descriptor */
134 unsigned mode
; /* Interesting event for file */
135 void (*func
)(int /*fd*/, unsigned /*mode*/, void */
*p*/
); /* Handler */
136 void *p
; /* Argument for the handler */
139 /* --- Waiting for a timeout --- */
141 typedef struct sel_timer
{
142 struct sel_timer
*next
; /* Next timer in the list */
143 struct sel_timer
*prev
; /* Previous timer in the list */
144 struct timeval tv
; /* Real time when timer should go */
145 void (*func
)(struct timeval */
*tv*/
, void */
*p*/
); /* Handler function */
146 void *p
; /* Argument for the handler */
149 /* --- A select argument block --- */
151 typedef struct sel_args
{
152 int maxfd
; /* Highest-numbered file */
153 fd_set fd
[SEL_MODES
]; /* Bit flags for all the files */
154 struct timeval tv
, *tvp
; /* Time to return */
155 struct timeval now
; /* Current time */
158 /* --- A selector hook --- *
160 * The hooks are called (in arbitrary order) on each select.
163 typedef void (*sel_hookfn
)(sel_state */
*s*/
,
167 typedef struct sel_hook
{
168 struct sel_hook
*next
; /* Next hook in the list */
169 struct sel_hook
*prev
; /* Previous hook in the list */
170 sel_hookfn before
, after
; /* Hook functions */
171 void *p
; /* Argument for the hook functions */
174 /*----- Functions provided ------------------------------------------------*/
176 /* --- @sel_init@ --- *
178 * Arguments: @sel_state *s@ = pointer to a state block to initialize
182 * Use: Initializes a select state block.
185 extern void sel_init(sel_state */
*s*/
);
187 /* --- @sel_initfile@ --- *
189 * Arguments: @sel_state *s@ = select state to attach to
190 * @sel_file *f@ = pointer to a file block to initialize
191 * @int fd@ = the file descriptor to listen to
192 * @unsigned mode@ = what to listen for
193 * @void (*func)(int fd, unsigned mode, void *p)@ = handler
194 * @void *p@ = argument to pass to handler
198 * Use: Initializes a file block ready for use. The file block
199 * isn't added to the list of things to do until a call to
203 extern void sel_initfile(sel_state */
*s*/
, sel_file */
*f*/
,
204 int /*fd*/, unsigned /*mode*/,
205 void (*/
*func*/
)(int /*fd*/,
210 /* --- @sel_addfile@ --- *
212 * Arguments: @sel_file *f@ = pointer to a file block
216 * Use: Adds a file block into the list of things to listen to.
219 extern void sel_addfile(sel_file */
*f*/
);
221 /* --- @sel_rmfile@ --- *
223 * Arguments: @sel_file *f@ = pointer to a file block
227 * Use: Removes a file block from the list of things to listen to.
230 extern void sel_rmfile(sel_file */
*f*/
);
232 /* --- @sel_force@ --- *
234 * Arguments: @sel_file *f@ = pointer to file selector
238 * Use: Forces a file selector to be considered ready. This is only
239 * useful during a call to @sel_select@. Of particular use is
240 * forcing a write selector when there's something interesting
244 extern void sel_force(sel_file */
*f*/
);
246 /* --- @sel_addtimer@ --- *
248 * Arguments: @sel_state *s@ = pointer to a state block
249 * @sel_timer *t@ = pointer to a timer block
250 * @struct timeval *tv@ = pointer to time to activate
251 * @void *p@ = argument for handler function
255 * Use: Registers and sets up a timer.
258 extern void sel_addtimer(sel_state */
*s*/
, sel_timer */
*t*/
,
259 struct timeval */
*tv*/
,
260 void (*/
*func*/
)(struct timeval */
*tv*/
,
264 /* --- @sel_rmtimer@ --- *
266 * Arguments: @sel_timer *t@ = pointer to timer block
270 * Use: Removes a timer from the list of timers.
273 extern void sel_rmtimer(sel_timer */
*t*/
);
275 /* --- @sel_addhook@ --- *
277 * Arguments: @sel_state *s@ = pointer to state block
278 * @sel_hook *h@ = pointer to hook block
279 * @sel_hookfn before, after@ = hook functions
280 * @void *p@ = pointer argument to pass to hook functions
284 * Use: Registers hook functions to be called on each select call.
287 extern void sel_addhook(sel_state */
*s*/
, sel_hook */
*h*/
,
288 sel_hookfn
/*before*/, sel_hookfn
/*after*/,
291 /* --- @sel_rmhook@ --- *
293 * Arguments: @sel_hook *h@ = pointer to hook block
297 * Use: Removes hook functions.
300 extern void sel_rmhook(sel_hook */
*h*/
);
302 /* --- @sel_fdmerge@ --- *
304 * Arguments: @fd_set *dest@ = destination FD set
305 * @fd_set *fd@ = pointer to set to merge
306 * @int maxfd@ = highest numbered descriptor in @fd@ + 1
308 * Returns: Actual highest numbered descriptor.
310 * Use: Merges file descriptor sets, and returns an accurate @maxfd@
314 extern int sel_fdmerge(fd_set */
*dest*/
, fd_set */
*fd*/
, int /*maxfd*/);
316 /* --- @sel_select@ --- *
318 * Arguments: @sel_state *s@ = pointer to state block
320 * Returns: Zero if all OK, -1 on error.
322 * Use: Does a @select@ call (or equivalent @poll@).
325 extern int sel_select(sel_state */
*s*/
);
327 /*----- That's all, folks -------------------------------------------------*/