3 * I/O multiplexing support
5 * (c) 1999 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of the mLib utilities library.
12 * mLib is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
17 * mLib is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
22 * You should have received a copy of the GNU Library General Public
23 * License along with mLib; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
35 /*----- Theory lesson -----------------------------------------------------*
37 * Things which are expecting to do I/O or go off at a certain time are
38 * called `selectors'. There are two types of selectors: `file selectors'
39 * wait patiently for a file to become readable or writable; `timeout
40 * selectors' wait for a certain amount of time to elapse. There is also a
41 * `multiplexor' which copes with managing all of this stuff.
43 * Multiplexors aren't actually very interesting. You initialize them with
44 * @sel_init@, and then add and remove selectors as you go. When you want to
45 * wait for something to happen, call @sel_select@.
47 * A file selector can *either* read *or* write. It can't do both. This is
48 * because you quite often want to read a socket but not write it; during
49 * those times you don't want to write, you just don't install a write
52 * File selectors are called when their files are available for reading or
53 * writing as appropriate, and given their file descriptor, the state of the
54 * file, and a pointer that was registered along with the selector.
56 * File selectors are set up in two phases. First, they're `initialized'
57 * with @sel_initfile@. An initialized file selector doesn't do anything.
58 * It needs to be added to a multiplexor using `sel_addfile'. It can later
59 * be removed using `sel_rmfile'. You can carry on adding and removing as
60 * you wish. Just don't try adding it twice in a row.
62 * Timeout selectors are called at a certain time. (Actually, they're called
63 * *after* a certain time.) There's no separate initialization step with
64 * timouts: you just add them and they work. If you decide you don't want a
65 * timeout to go off, then you just remove it. (Adding and removing the
66 * *same* timeout isn't something you do very often. You usually use a
67 * different expiry time each time.)
70 /*----- Header files ------------------------------------------------------*/
72 #include <sys/types.h>
76 /*----- Data structures ---------------------------------------------------*/
78 /* --- A multiplexor --- *
80 * The files are sorted in reverse order of file descriptor number; the
81 * timers are in normal order of occurrence. Thus, the interesting one
82 * is always at the front of the list.
86 SEL_READ
, /* File is ready to read */
87 SEL_WRITE
, /* File is ready to write */
88 SEL_EXC
, /* Something odd has happened */
89 SEL_MODES
/* Number of modes available */
92 typedef struct sel_state
{
93 struct sel_file
*files
[SEL_MODES
]; /* Lists of interesting files */
94 struct sel_timer
*timers
; /* List of timers */
95 struct sel_hook
*hooks
; /* List of hook functions applied */
96 fd_set fd
[SEL_MODES
]; /* Quick reference table for files */
97 struct sel_args
*args
; /* Pointer to arguments */
100 /* --- Listening for a file --- */
102 typedef struct sel_file
{
103 struct sel_file
*next
; /* Next file in the list */
104 struct sel_file
**prev
; /* Previous file in the list */
105 struct sel_state
*s
; /* Pointer to select multiplexor */
106 int fd
; /* File descriptor */
107 unsigned mode
; /* Interesting event for file */
108 void (*func
)(int /*fd*/, unsigned /*mode*/, void */
*p*/
); /* Handler */
109 void *p
; /* Argument for the handler */
110 struct sel_pendfile
*pend
; /* Pending file information */
113 /* --- Waiting for a timeout --- */
115 typedef struct sel_timer
{
116 struct sel_timer
*next
; /* Next timer in the list */
117 struct sel_timer
**prev
; /* Previous timer in the list */
118 struct timeval tv
; /* Real time when timer should go */
119 void (*func
)(struct timeval */
*tv*/
, void */
*p*/
); /* Handler function */
120 void *p
; /* Argument for the handler */
121 struct sel_pendtimer
*pend
; /* Pending timer information */
124 /* --- A select argument block --- */
126 typedef struct sel_args
{
127 int maxfd
; /* Highest-numbered file */
128 fd_set fd
[SEL_MODES
]; /* Bit flags for all the files */
129 struct timeval tv
, *tvp
; /* Time to return */
130 struct timeval now
; /* Current time */
133 /* --- A selector hook --- *
135 * The hooks are called (in arbitrary order) on each select.
138 typedef void (*sel_hookfn
)(sel_state */
*s*/
,
142 typedef struct sel_hook
{
143 struct sel_hook
*next
; /* Next hook in the list */
144 struct sel_hook
**prev
; /* Previous hook in the list */
145 sel_hookfn before
, after
; /* Hook functions */
146 void *p
; /* Argument for the hook functions */
149 /*----- Functions provided ------------------------------------------------*/
151 /* --- @sel_init@ --- *
153 * Arguments: @sel_state *s@ = pointer to a state block to initialize
157 * Use: Initializes a select state block.
160 extern void sel_init(sel_state */
*s*/
);
162 /* --- @sel_initfile@ --- *
164 * Arguments: @sel_state *s@ = select state to attach to
165 * @sel_file *f@ = pointer to a file block to initialize
166 * @int fd@ = the file descriptor to listen to
167 * @unsigned mode@ = what to listen for
168 * @void (*func)(int fd, unsigned mode, void *p)@ = handler
169 * @void *p@ = argument to pass to handler
173 * Use: Initializes a file block ready for use. The file block
174 * isn't added to the list of things to do until a call to
178 extern void sel_initfile(sel_state */
*s*/
, sel_file */
*f*/
,
179 int /*fd*/, unsigned /*mode*/,
180 void (*/
*func*/
)(int /*fd*/,
185 /* --- @sel_addfile@ --- *
187 * Arguments: @sel_file *f@ = pointer to a file block
191 * Use: Adds a file block into the list of things to listen to.
194 extern void sel_addfile(sel_file */
*f*/
);
196 /* --- @sel_rmfile@ --- *
198 * Arguments: @sel_file *f@ = pointer to a file block
202 * Use: Removes a file block from the list of things to listen to.
205 extern void sel_rmfile(sel_file */
*f*/
);
207 /* --- @sel_force@ --- *
209 * Arguments: @sel_file *f@ = pointer to file selector
213 * Use: Forces a file selector to be considered ready. This is only
214 * useful during a call to @sel_select@. Of particular use is
215 * forcing a write selector when there's something interesting
219 extern void sel_force(sel_file */
*f*/
);
221 /* --- @sel_addtimer@ --- *
223 * Arguments: @sel_state *s@ = pointer to a state block
224 * @sel_timer *t@ = pointer to a timer block
225 * @struct timeval *tv@ = pointer to time to activate
226 * @void *p@ = argument for handler function
230 * Use: Registers and sets up a timer.
233 extern void sel_addtimer(sel_state */
*s*/
, sel_timer */
*t*/
,
234 struct timeval */
*tv*/
,
235 void (*/
*func*/
)(struct timeval */
*tv*/
,
239 /* --- @sel_rmtimer@ --- *
241 * Arguments: @sel_timer *t@ = pointer to timer block
245 * Use: Removes a timer from the list of timers.
248 extern void sel_rmtimer(sel_timer */
*t*/
);
250 /* --- @sel_addhook@ --- *
252 * Arguments: @sel_state *s@ = pointer to state block
253 * @sel_hook *h@ = pointer to hook block
254 * @sel_hookfn before, after@ = hook functions
255 * @void *p@ = pointer argument to pass to hook functions
259 * Use: Registers hook functions to be called on each select call.
262 extern void sel_addhook(sel_state */
*s*/
, sel_hook */
*h*/
,
263 sel_hookfn
/*before*/, sel_hookfn
/*after*/,
266 /* --- @sel_rmhook@ --- *
268 * Arguments: @sel_hook *h@ = pointer to hook block
272 * Use: Removes hook functions.
275 extern void sel_rmhook(sel_hook */
*h*/
);
277 /* --- @sel_fdmerge@ --- *
279 * Arguments: @fd_set *dest@ = destination FD set
280 * @fd_set *fd@ = pointer to set to merge
281 * @int maxfd@ = highest numbered descriptor in @fd@ + 1
283 * Returns: Actual highest numbered descriptor.
285 * Use: Merges file descriptor sets, and returns an accurate @maxfd@
289 extern int sel_fdmerge(fd_set */
*dest*/
, fd_set */
*fd*/
, int /*maxfd*/);
291 /* --- @sel_select@ --- *
293 * Arguments: @sel_state *s@ = pointer to state block
295 * Returns: Zero if all OK, -1 on error.
297 * Use: Does a @select@ call (or equivalent @poll@).
300 extern int sel_select(sel_state */
*s*/
);
302 /*----- That's all, folks -------------------------------------------------*/