3 * $Id: sel.h,v 1.2 1999/05/15 10:33:32 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 1.2 1999/05/15 10:33:32 mdw
34 * Fix copyright notices.
36 * Revision 1.1 1999/05/14 21:01:15 mdw
37 * Integrated `select' handling bits from the background resolver project.
48 /*----- Theory lesson -----------------------------------------------------*
50 * Things which are expecting to do I/O or go off at a certain time are
51 * called `selectors'. There are two types of selectors: `file selectors'
52 * wait patiently for a file to become readable or writable; `timeout
53 * selectors' wait for a certain amount of time to elapse. There is also a
54 * `multiplexor' which copes with managing all of this stuff.
56 * Multiplexors aren't actually very interesting. You initialize them with
57 * @sel_init@, and then add and remove selectors as you go. When you want to
58 * wait for something to happen, call @sel_select@.
60 * A file selector can *either* read *or* write. It can't do both. This is
61 * because you quite often want to read a socket but not write it; during
62 * those times you don't want to write, you just don't install a write
65 * File selectors are called when their files are available for reading or
66 * writing as appropriate, and given their file descriptor, the state of the
67 * file, and a pointer that was registered along with the selector.
69 * File selectors are set up in two phases. First, they're `initialized'
70 * with @sel_initfile@. An initialized file selector doesn't do anything.
71 * It needs to be added to a multiplexor using `sel_addfile'. It can later
72 * be removed using `sel_rmfile'. You can carry on adding and removing as
73 * you wish. Just don't try adding it twice in a row.
75 * Timeout selectors are called at a certain time. (Actually, they're called
76 * *after* a certain time.) There's no separate initialization step with
77 * timouts: you just add them and they work. If you decide you don't want a
78 * timeout to go off, then you just remove it. (Adding and removing the
79 * *same* timeout isn't something you do very often. You usually use a
80 * different expiry time each time.)
83 /*----- Header files ------------------------------------------------------*/
85 #include <sys/types.h>
89 /*----- Data structures ---------------------------------------------------*/
91 /* --- Listening for a file --- */
93 typedef struct sel_file {
94 struct sel_file *next;
95 struct sel_file *prev;
99 void (*func)(int /*fd*/, unsigned /*mode*/, void */*p*/);
108 /* --- Waiting for a timeout --- */
110 typedef struct sel_timer {
111 struct sel_timer *next;
112 struct sel_timer *prev;
114 void (*func)(struct timeval *tv, void *p);
118 /* --- A multiplexer --- *
120 * The files are sorted in reverse order of file descriptor number; the
121 * timers are in normal order of occurrence. Thus, the interesting one
122 * is always at the front of the list.
125 typedef struct sel_state {
126 struct sel_file *files;
127 struct sel_timer *timers;
128 fd_set fd[SEL_MODES];
132 /*----- Functions provided ------------------------------------------------*/
134 /* --- @sel_init@ --- *
136 * Arguments: @sel_state *s@ = pointer to a state block to initialize
140 * Use: Initializes a select state block.
143 extern void sel_init(sel_state */*s*/);
145 /* --- @sel_initfile@ --- *
147 * Arguments: @sel_state *s@ = select state to attach to
148 * @sel_file *f@ = pointer to a file block to initialize
149 * @int fd@ = the file descriptor to listen to
150 * @unsigned mode@ = what to listen for
151 * @void (*func)(int fd, unsigned mode, void *p)@ = handler
152 * @void *p@ = argument to pass to handler
156 * Use: Initializes a file block ready for use. The file block
157 * isn't added to the list of things to do until a call to
161 extern void sel_initfile(sel_state */*s*/, sel_file */*f*/,
162 int /*fd*/, unsigned /*mode*/,
163 void (*/*func*/)(int /*fd*/,
168 /* --- @sel_addfile@ --- *
170 * Arguments: @sel_file *f@ = pointer to a file block
174 * Use: Adds a file block into the list of things to listen to.
177 extern void sel_addfile(sel_file */*f*/);
179 /* --- @sel_rmfile@ --- *
181 * Arguments: @sel_file *f@ = pointer to a file block
185 * Use: Removes a file block from the list of things to listen to.
188 extern void sel_rmfile(sel_file */*f*/);
190 /* --- @sel_addtimer@ --- *
192 * Arguments: @sel_state *s@ = pointer to a state block
193 * @sel_timer *t@ = pointer to a timer block
194 * @struct timeval *tv@ = pointer to time to activate
195 * @void (*func)(struct timeval *tv, void *p)@ = handler
196 * @void *p@ = argument for handler function
200 * Use: Registers and sets up a timer.
203 extern void sel_addtimer(sel_state */*s*/, sel_timer */*t*/,
204 struct timeval */*tv*/,
205 void (*/*func*/)(struct timeval */*tv*/,
209 /* --- @sel_rmtimer@ --- *
211 * Arguments: @sel_timer *t@ = pointer to timer block
215 * Use: Removes a timer from the list of timers.
218 extern void sel_rmtimer(sel_timer */*t*/);
220 /* --- @sel_select@ --- *
222 * Arguments: @sel_state *s@ = pointer to state block
224 * Returns: Zero if all OK, -1 on error.
226 * Use: Does a @select@ call (or equivalent @poll@).
229 extern int sel_select(sel_state */*s*/);
231 /*----- That's all, folks -------------------------------------------------*/