2 '\" Copyright (c)1996-2006 by Hartmut Brandt
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5 '\" Author: harti@freebsd.org <Hartmut Brandt>
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29 '\" $Begemot: libbegemot/rpoll.man,v 1.4 2004/09/21 15:59:00 brandt Exp $
31 .TH rpoll 3 "8 Dec 2006" "BEGEMOT" "BEGEMOT Library"
33 rpoll - callback functions for file descriptors and timers
36 .B "# include <rpoll.h>"
38 .BR "typedef void (*poll_f)(int " "fd" ", int " "mask" ", void *" "arg" ");"
40 .BR "typedef void (*timer_f)(int " "tid" ", void *" "arg" ");"
42 .BR "int poll_register(int " "fd" ", poll_f "
43 .RB "func" ", void *" "arg" ", int " "mask" ");"
45 .BR "void poll_unregister(int " "handle" ");"
47 .BR "int poll_start_timer(u_int " "msecs" ", int " "repeat" ", timer_f " "func" ","
49 .BR "void *" "arg" ");"
51 .BR "void poll_stop_timer(int " "handle" ");"
53 .BR "int poll_start_utimer(unsigned long long " "usecs" ", int " "repeat" ",
55 .BR "timer_f " "func" ", void *" "arg" ");"
57 .BR "void poll_dispatch(int " "wait" ");"
59 Many programs need to read from several file descriptors at the same time.
60 Typically in these programs one of
65 These calls are however clumsy to use and the usage of one of these calls is
66 probably not portable to other systems - not all systems support both calls.
70 family of functions is designed to overcome these restrictions.
71 They support the well known and understood technique of event driven
72 programing and, in addition to
78 Each event on a file descriptor or each timer event is translated into a call to a user
79 defined callback function. These functions need to be registered.
80 A file descriptor is registered with
83 is the file descriptor to watch,
86 It may be any combination of
88 to get informed when input on the file descriptor is possible,
90 to get informed when output is possible or
92 to get informed when an exceptional condition occures.
93 An example of an exceptional condition is the arrival of urgent data.
94 (Note, that an end of file condition is signaled via POLL_IN).
96 is the user function to be called and
98 is a user supplied argument for this function.
99 The callback functions is called with the file descriptor, a mask
100 describing the actual events (from the set supplied in the registration) and
103 returns a handle, which may be used later to de-register the file descriptor.
104 A file descriptor may be registered more than once, if the function, the user arguments
105 or both differ in the call to
111 are the same, then no new registration is done, instead the event mask of the registration
112 is changed to reflect the new mask.
114 A registered file descriptor may be de-registered by calling
116 with the handle returned by
119 A timer is created with
122 .BR poll_start_utimer .
124 is the number of milliseconds in
128 is the number of microseconds in
129 .BR poll_start_utimer ,
130 after which the timer event will be generated.
131 If the functions use the
135 is rounded to milliseconds and
139 selects one-short behavior (if 0) or a repeatable timer (if not 0). A one-short timer
140 will automatically unregistered after expiry.
142 is the user function which will be called with a timer id and the user supplied
147 return a timer id, which may be used to cancel the timer with
148 .BR poll_stop_timer .
149 A one-short timer should be canceled only if it has not yet fired.
152 must be called to actually dispatch events.
154 is a flag, which should be 0, if only a poll should be done. In this case, the function returns,
155 after polling the registered file descriptors and timers. If
159 waits until an event occures. All events are dispatch (i.e. callback functions called) and
160 .B poll_dispatch returns.
173 .BR poll (2), select (3C)
179 return a handle which may be used to unregister the file descriptor or
189 System call or memory allocation errors are fatal and are handle by calling
191 The one exception is a return of EINTR from
205 in callback functions may probably break the code.
211 Hartmut Brandt, harti@freebsd.org