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1 | /* -*-c-*- |
2 | * |
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3 | * I/O multiplexing support |
4 | * |
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5 | * (c) 1999 Straylight/Edgeware |
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6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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9 | * |
10 | * This file is part of the mLib utilities library. |
11 | * |
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. |
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16 | * |
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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. |
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21 | * |
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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, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
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28 | #ifndef MLIB_SEL_H |
29 | #define MLIB_SEL_H |
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30 | |
31 | #ifdef __cplusplus |
32 | extern "C" { |
33 | #endif |
34 | |
35 | /*----- Theory lesson -----------------------------------------------------* |
36 | * |
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. |
42 | * |
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@. |
46 | * |
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 |
50 | * selector. |
51 | * |
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. |
55 | * |
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. |
61 | * |
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.) |
68 | */ |
69 | |
70 | /*----- Header files ------------------------------------------------------*/ |
71 | |
72 | #include <sys/types.h> |
73 | #include <sys/time.h> |
74 | #include <unistd.h> |
75 | |
76 | /*----- Data structures ---------------------------------------------------*/ |
77 | |
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78 | /* --- A multiplexor --- * |
79 | * |
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. |
83 | */ |
84 | |
85 | enum { |
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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 */ |
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90 | }; |
91 | |
92 | typedef struct sel_state { |
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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 */ |
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98 | } sel_state; |
99 | |
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100 | /* --- Listening for a file --- */ |
101 | |
102 | typedef struct sel_file { |
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103 | struct sel_file *next; /* Next file in the list */ |
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104 | struct sel_file **prev; /* Previous file in the list */ |
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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 */ |
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110 | struct sel_pendfile *pend; /* Pending file information */ |
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111 | } sel_file; |
112 | |
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113 | /* --- Waiting for a timeout --- */ |
114 | |
115 | typedef struct sel_timer { |
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116 | struct sel_timer *next; /* Next timer in the list */ |
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117 | struct sel_timer **prev; /* Previous timer in the list */ |
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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 */ |
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121 | struct sel_pendtimer *pend; /* Pending timer information */ |
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122 | } sel_timer; |
123 | |
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124 | /* --- A select argument block --- */ |
125 | |
126 | typedef struct sel_args { |
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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 */ |
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131 | } sel_args; |
132 | |
133 | /* --- A selector hook --- * |
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134 | * |
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135 | * The hooks are called (in arbitrary order) on each select. |
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136 | */ |
137 | |
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138 | typedef void (*sel_hookfn)(sel_state */*s*/, |
139 | sel_args */*a*/, |
140 | void */*p*/); |
141 | |
142 | typedef struct sel_hook { |
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143 | struct sel_hook *next; /* Next hook in the list */ |
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144 | struct sel_hook **prev; /* Previous hook in the list */ |
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145 | sel_hookfn before, after; /* Hook functions */ |
146 | void *p; /* Argument for the hook functions */ |
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147 | } sel_hook; |
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148 | |
149 | /*----- Functions provided ------------------------------------------------*/ |
150 | |
151 | /* --- @sel_init@ --- * |
152 | * |
153 | * Arguments: @sel_state *s@ = pointer to a state block to initialize |
154 | * |
155 | * Returns: --- |
156 | * |
157 | * Use: Initializes a select state block. |
158 | */ |
159 | |
160 | extern void sel_init(sel_state */*s*/); |
161 | |
162 | /* --- @sel_initfile@ --- * |
163 | * |
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 |
170 | * |
171 | * Returns: --- |
172 | * |
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 |
175 | * @sel_addfile@. |
176 | */ |
177 | |
178 | extern void sel_initfile(sel_state */*s*/, sel_file */*f*/, |
179 | int /*fd*/, unsigned /*mode*/, |
180 | void (*/*func*/)(int /*fd*/, |
181 | unsigned /*mode*/, |
182 | void */*p*/), |
183 | void */*p*/); |
184 | |
185 | /* --- @sel_addfile@ --- * |
186 | * |
187 | * Arguments: @sel_file *f@ = pointer to a file block |
188 | * |
189 | * Returns: --- |
190 | * |
191 | * Use: Adds a file block into the list of things to listen to. |
192 | */ |
193 | |
194 | extern void sel_addfile(sel_file */*f*/); |
195 | |
196 | /* --- @sel_rmfile@ --- * |
197 | * |
198 | * Arguments: @sel_file *f@ = pointer to a file block |
199 | * |
200 | * Returns: --- |
201 | * |
202 | * Use: Removes a file block from the list of things to listen to. |
203 | */ |
204 | |
205 | extern void sel_rmfile(sel_file */*f*/); |
206 | |
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207 | /* --- @sel_force@ --- * |
208 | * |
209 | * Arguments: @sel_file *f@ = pointer to file selector |
210 | * |
211 | * Returns: --- |
212 | * |
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 |
216 | * ready for it. |
217 | */ |
218 | |
219 | extern void sel_force(sel_file */*f*/); |
220 | |
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221 | /* --- @sel_addtimer@ --- * |
222 | * |
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 |
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226 | * @void *p@ = argument for handler function |
227 | * |
228 | * Returns: --- |
229 | * |
230 | * Use: Registers and sets up a timer. |
231 | */ |
232 | |
233 | extern void sel_addtimer(sel_state */*s*/, sel_timer */*t*/, |
234 | struct timeval */*tv*/, |
235 | void (*/*func*/)(struct timeval */*tv*/, |
236 | void */*p*/), |
237 | void */*p*/); |
238 | |
239 | /* --- @sel_rmtimer@ --- * |
240 | * |
241 | * Arguments: @sel_timer *t@ = pointer to timer block |
242 | * |
243 | * Returns: --- |
244 | * |
245 | * Use: Removes a timer from the list of timers. |
246 | */ |
247 | |
248 | extern void sel_rmtimer(sel_timer */*t*/); |
249 | |
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250 | /* --- @sel_addhook@ --- * |
251 | * |
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 |
256 | * |
257 | * Returns: --- |
258 | * |
259 | * Use: Registers hook functions to be called on each select call. |
260 | */ |
261 | |
262 | extern void sel_addhook(sel_state */*s*/, sel_hook */*h*/, |
263 | sel_hookfn /*before*/, sel_hookfn /*after*/, |
264 | void */*p*/); |
265 | |
266 | /* --- @sel_rmhook@ --- * |
267 | * |
268 | * Arguments: @sel_hook *h@ = pointer to hook block |
269 | * |
270 | * Returns: --- |
271 | * |
272 | * Use: Removes hook functions. |
273 | */ |
274 | |
275 | extern void sel_rmhook(sel_hook */*h*/); |
276 | |
277 | /* --- @sel_fdmerge@ --- * |
278 | * |
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 |
282 | * |
283 | * Returns: Actual highest numbered descriptor. |
284 | * |
285 | * Use: Merges file descriptor sets, and returns an accurate @maxfd@ |
286 | * value. |
287 | */ |
288 | |
289 | extern int sel_fdmerge(fd_set */*dest*/, fd_set */*fd*/, int /*maxfd*/); |
290 | |
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291 | /* --- @sel_select@ --- * |
292 | * |
293 | * Arguments: @sel_state *s@ = pointer to state block |
294 | * |
295 | * Returns: Zero if all OK, -1 on error. |
296 | * |
297 | * Use: Does a @select@ call (or equivalent @poll@). |
298 | */ |
299 | |
300 | extern int sel_select(sel_state */*s*/); |
301 | |
302 | /*----- That's all, folks -------------------------------------------------*/ |
303 | |
304 | #ifdef __cplusplus |
305 | } |
306 | #endif |
307 | |
308 | #endif |