[ViewVC] Diff of: cvs/libev/ev.3

Comparing libev/ev.3 (file contents):
Revision 1.27 by root, Tue Nov 27 20:15:01 2007 UTC vs.
Revision 1.32 by root, Wed Nov 28 17:32:24 2007 UTC

 .\}
 .rm #[ #] #H #V #F C
 .\" ========================================================================
 .\"
 .IX Title ""<STANDARD INPUT>" 1"
-.TH "<STANDARD INPUT>" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH "<STANDARD INPUT>" 1 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation"
 .SH "NAME"
 libev \- a high performance full\-featured event loop written in C
 .SH "SYNOPSIS"
 .IX Header "SYNOPSIS"
+.Vb 1
+\&  #include <ev.h>
+.Ve
+.SH "EXAMPLE PROGRAM"
+.IX Header "EXAMPLE PROGRAM"
+.Vb 1
+\&  #include <ev.h>
+.Ve
+.PP
 .Vb 2
-\&  /* this is the only header you need */
-\&  #include <ev.h>
-.Ve
-.PP
-.Vb 3
-\&  /* what follows is a fully working example program */
 \&  ev_io stdin_watcher;
 \&  ev_timer timeout_watcher;
 .Ve
 .PP
 .Vb 8
 watchers\fR, which are relatively small C structures you initialise with the
 details of the event, and then hand it over to libev by \fIstarting\fR the
 watcher.
 .SH "FEATURES"
 .IX Header "FEATURES"
-Libev supports select, poll, the linux-specific epoll and the bsd-specific
+Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
-kqueue mechanisms for file descriptor events, relative timers, absolute
+BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
-timers with customised rescheduling, signal events, process status change
+for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
-events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event
+(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
-loop mechanism itself (idle, prepare and check watchers). It also is quite
+with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
-fast (see this benchmark comparing
+(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
-it to libevent for example).
+watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
+\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
+file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
+(\f(CW\*(C`ev_fork\*(C'\fR).
+.PP
+It also is quite fast (see this
+benchmark comparing it to libevent
+for example).
 .SH "CONVENTIONS"
 .IX Header "CONVENTIONS"
-Libev is very configurable. In this manual the default configuration
+Libev is very configurable. In this manual the default configuration will
-will be described, which supports multiple event loops. For more info
+be described, which supports multiple event loops. For more info about
-about various configuration options please have a look at the file
+various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
-\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without
+this manual. If libev was configured without support for multiple event
-support for multiple event loops, then all functions taking an initial
+loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
-argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR)
+(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
-will not have this argument.
 .SH "TIME REPRESENTATION"
 .IX Header "TIME REPRESENTATION"
 Libev represents time as a single floating point number, representing the
 (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
 the beginning of 1970, details are complicated, don't ask). This type is
 Usually, it's a good idea to terminate if the major versions mismatch,
 as this indicates an incompatible change.  Minor versions are usually
 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 .Sp
-Example: make sure we haven't accidentally been linked against the wrong
+Example: Make sure we haven't accidentally been linked against the wrong
-version:
+version.
 .Sp
 .Vb 3
 \&  assert (("libev version mismatch",
 \&           ev_version_major () == EV_VERSION_MAJOR
 \&           && ev_version_minor () >= EV_VERSION_MINOR));
 might be supported on the current system, you would need to look at
 \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
 recommended ones.
 .Sp
 See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
-.IP "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" 4
+.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
-.IX Item "ev_set_allocator (void *(*cb)(void *ptr, size_t size))"
+.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
-Sets the allocation function to use (the prototype and semantics are
+Sets the allocation function to use (the prototype is similar \- the
-identical to the realloc C function). It is used to allocate and free
+semantics is identical \- to the realloc C function). It is used to
-memory (no surprises here). If it returns zero when memory needs to be
+allocate and free memory (no surprises here). If it returns zero when
-allocated, the library might abort or take some potentially destructive
+memory needs to be allocated, the library might abort or take some
-action. The default is your system realloc function.
+potentially destructive action. The default is your system realloc
+function.
 .Sp
 You could override this function in high-availability programs to, say,
 free some memory if it cannot allocate memory, to use a special allocator,
 or even to sleep a while and retry until some memory is available.
 .Sp
-Example: replace the libev allocator with one that waits a bit and then
+Example: Replace the libev allocator with one that waits a bit and then
-retries: better than mine).
+retries).
 .Sp
 .Vb 6
 \&   static void *
 \&   persistent_realloc (void *ptr, size_t size)
 \&   {
 callback is set, then libev will expect it to remedy the sitution, no
 matter what, when it returns. That is, libev will generally retry the
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 .Sp
-Example: do the same thing as libev does internally:
+Example: This is basically the same thing that libev does internally, too.
 .Sp
 .Vb 6
 \&   static void
 \&   fatal_error (const char *msg)
 \&   {
 Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
 always distinct from the default loop. Unlike the default loop, it cannot
 handle signal and child watchers, and attempts to do so will be greeted by
 undefined behaviour (or a failed assertion if assertions are enabled).
 .Sp
-Example: try to create a event loop that uses epoll and nothing else.
+Example: Try to create a event loop that uses epoll and nothing else.
 .Sp
 .Vb 3
 \&  struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
 \&  if (!epoller)
 \&    fatal ("no epoll found here, maybe it hides under your chair");
 \&     be handled here by queueing them when their watcher gets executed.
 \&   - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
 \&     were used, return, otherwise continue with step *.
 .Ve
 .Sp
-Example: queue some jobs and then loop until no events are outsanding
+Example: Queue some jobs and then loop until no events are outsanding
 anymore.
 .Sp
 .Vb 4
 \&   ... queue jobs here, make sure they register event watchers as long
 \&   ... as they still have work to do (even an idle watcher will do..)
 visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
 no event watchers registered by it are active. It is also an excellent
 way to do this for generic recurring timers or from within third-party
 libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
 .Sp
-Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
+Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
 running when nothing else is active.
 .Sp
 .Vb 4
-\&  struct dv_signal exitsig;
+\&  struct ev_signal exitsig;
 \&  ev_signal_init (&exitsig, sig_cb, SIGINT);
-\&  ev_signal_start (myloop, &exitsig);
+\&  ev_signal_start (loop, &exitsig);
-\&  evf_unref (myloop);
+\&  evf_unref (loop);
 .Ve
 .Sp
-Example: for some weird reason, unregister the above signal handler again.
+Example: For some weird reason, unregister the above signal handler again.
 .Sp
 .Vb 2
-\&  ev_ref (myloop);
+\&  ev_ref (loop);
-\&  ev_signal_stop (myloop, &exitsig);
+\&  ev_signal_stop (loop, &exitsig);
 .Ve
 .SH "ANATOMY OF A WATCHER"
 .IX Header "ANATOMY OF A WATCHER"
 A watcher is a structure that you create and register to record your
 interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
 Returns a true value iff the watcher is pending, (i.e. it has outstanding
 events but its callback has not yet been invoked). As long as a watcher
 is pending (but not active) you must not call an init function on it (but
 \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
 libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
-.IP "callback = ev_cb (ev_TYPE *watcher)" 4
+.IP "callback ev_cb (ev_TYPE *watcher)" 4
-.IX Item "callback = ev_cb (ev_TYPE *watcher)"
+.IX Item "callback ev_cb (ev_TYPE *watcher)"
 Returns the callback currently set on the watcher.
 .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
 .IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
 Change the callback. You can change the callback at virtually any time
 (modulo threads).
 \&    struct my_io *w = (struct my_io *)w_;
 \&    ...
 \&  }
 .Ve
 .PP
-More interesting and less C\-conformant ways of catsing your callback type
+More interesting and less C\-conformant ways of casting your callback type
-have been omitted....
+instead have been omitted.
+.PP
+Another common scenario is having some data structure with multiple
+watchers:
+.PP
+.Vb 6
+\&  struct my_biggy
+\&  {
+\&    int some_data;
+\&    ev_timer t1;
+\&    ev_timer t2;
+\&  }
+.Ve
+.PP
+In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
+you need to use \f(CW\*(C`offsetof\*(C'\fR:
+.PP
+.Vb 1
+\&  #include <stddef.h>
+.Ve
+.PP
+.Vb 6
+\&  static void
+\&  t1_cb (EV_P_ struct ev_timer *w, int revents)
+\&  {
+\&    struct my_biggy big = (struct my_biggy *
+\&      (((char *)w) - offsetof (struct my_biggy, t1));
+\&  }
+.Ve
+.PP
+.Vb 6
+\&  static void
+\&  t2_cb (EV_P_ struct ev_timer *w, int revents)
+\&  {
+\&    struct my_biggy big = (struct my_biggy *
+\&      (((char *)w) - offsetof (struct my_biggy, t2));
+\&  }
+.Ve
 .SH "WATCHER TYPES"
 .IX Header "WATCHER TYPES"
 This section describes each watcher in detail, but will not repeat
 information given in the last section. Any initialisation/set macros,
 functions and members specific to the watcher type are explained.
 The file descriptor being watched.
 .IP "int events [read\-only]" 4
 .IX Item "int events [read-only]"
 The events being watched.
 .PP
-Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
+Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
 readable, but only once. Since it is likely line\-buffered, you could
-attempt to read a whole line in the callback:
+attempt to read a whole line in the callback.
 .PP
 .Vb 6
 \&  static void
 \&  stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
 \&  {
 .IX Item "ev_tstamp repeat [read-write]"
 The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
 or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
 which is also when any modifications are taken into account.
 .PP
-Example: create a timer that fires after 60 seconds.
+Example: Create a timer that fires after 60 seconds.
 .PP
 .Vb 5
 \&  static void
 \&  one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
 \&  {
 \&  struct ev_timer mytimer;
 \&  ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
 \&  ev_timer_start (loop, &mytimer);
 .Ve
 .PP
-Example: create a timeout timer that times out after 10 seconds of
+Example: Create a timeout timer that times out after 10 seconds of
 inactivity.
 .PP
 .Vb 5
 \&  static void
 \&  timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
 .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
 The current reschedule callback, or \f(CW0\fR, if this functionality is
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
 .PP
-Example: call a callback every hour, or, more precisely, whenever the
+Example: Call a callback every hour, or, more precisely, whenever the
 system clock is divisible by 3600. The callback invocation times have
 potentially a lot of jittering, but good long-term stability.
 .PP
 .Vb 5
 \&  static void
 \&  struct ev_periodic hourly_tick;
 \&  ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
 \&  ev_periodic_start (loop, &hourly_tick);
 .Ve
 .PP
-Example: the same as above, but use a reschedule callback to do it:
+Example: The same as above, but use a reschedule callback to do it:
 .PP
 .Vb 1
 \&  #include <math.h>
 .Ve
 .PP
 .PP
 .Vb 1
 \&  ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 .Ve
 .PP
-Example: call a callback every hour, starting now:
+Example: Call a callback every hour, starting now:
 .PP
 .Vb 4
 \&  struct ev_periodic hourly_tick;
 \&  ev_periodic_init (&hourly_tick, clock_cb,
 \&                    fmod (ev_now (loop), 3600.), 3600., 0);
 .IP "int rstatus [read\-write]" 4
 .IX Item "int rstatus [read-write]"
 The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
 \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
 .PP
-Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
+Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
 .PP
 .Vb 5
 \&  static void
 \&  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
 \&  {
 not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
 otherwise always forced to be at least one) and all the other fields of
 the stat buffer having unspecified contents.
 .PP
 Since there is no standard to do this, the portable implementation simply
-calls \f(CW\*(C`stat (2)\*(C'\fR regulalry on the path to see if it changed somehow. You
+calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
 can specify a recommended polling interval for this case. If you specify
 a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
 unspecified default\fR value will be used (which you can expect to be around
 five seconds, although this might change dynamically). Libev will also
 impose a minimum interval which is currently around \f(CW0.1\fR, but thats
 .PP
 This watcher type is not meant for massive numbers of stat watchers,
 as even with OS-supported change notifications, this can be
 resource\-intensive.
 .PP
-At the time of this writing, no specific \s-1OS\s0 backends are implemented, but
+At the time of this writing, only the Linux inotify interface is
-if demand increases, at least a kqueue and inotify backend will be added.
+implemented (implementing kqueue support is left as an exercise for the
+reader). Inotify will be used to give hints only and should not change the
+semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
+to fall back to regular polling again even with inotify, but changes are
+usually detected immediately, and if the file exists there will be no
+polling.
 .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
 .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
 .PD 0
 .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
 .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
 .IX Item "ev_idle_init (ev_signal *, callback)"
 Initialises and configures the idle watcher \- it has no parameters of any
 kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
 believe me.
 .PP
-Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the
+Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
-callback, free it. Alos, use no error checking, as usual.
+callback, free it. Also, use no error checking, as usual.
 .PP
 .Vb 7
 \&  static void
 \&  idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
 \&  {
 otherwise another method will be used as fallback. This is the preferred
 backend for Solaris 10 systems.
 .IP "\s-1EV_USE_DEVPOLL\s0" 4
 .IX Item "EV_USE_DEVPOLL"
 reserved for future expansion, works like the \s-1USE\s0 symbols above.
+.IP "\s-1EV_USE_INOTIFY\s0" 4
+.IX Item "EV_USE_INOTIFY"
+If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
+interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
+be detected at runtime.
 .IP "\s-1EV_H\s0" 4
 .IX Item "EV_H"
 The name of the \fIev.h\fR header file used to include it. The default if
 undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
 can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
 .IP "\s-1EV_PID_HASHSIZE\s0" 4
 .IX Item "EV_PID_HASHSIZE"
 \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
 pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
 than enough. If you need to manage thousands of children you might want to
-increase this value.
+increase this value (\fImust\fR be a power of two).
+.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
+.IX Item "EV_INOTIFY_HASHSIZE"
+\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
+inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
+usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
+watchers you might want to increase this value (\fImust\fR be a power of
+two).
 .IP "\s-1EV_COMMON\s0" 4
 .IX Item "EV_COMMON"
 By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
 this macro to a something else you can include more and other types of
 members. You have to define it each time you include one of the files,
 .IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
 .IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
 .IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
 .IP "Stopping check/prepare/idle watchers: O(1)" 4
 .IX Item "Stopping check/prepare/idle watchers: O(1)"
-.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" 4
+.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
-.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))"
+.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
 .IP "Finding the next timer per loop iteration: O(1)" 4
 .IX Item "Finding the next timer per loop iteration: O(1)"
 .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
 .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
 .IP "Activating one watcher: O(1)" 4

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Comparing libev/ev.3 (file contents): Revision 1.27 by root, Tue Nov 27 20:15:01 2007 UTC vs. Revision 1.32 by root, Wed Nov 28 17:32:24 2007 UTC

Diff Legend

Comparing libev/ev.3 (file contents):
Revision 1.27 by root, Tue Nov 27 20:15:01 2007 UTC vs.
Revision 1.32 by root, Wed Nov 28 17:32:24 2007 UTC