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58
README
58
README
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@ -2,8 +2,58 @@ libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims
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to be faster and more correct, and also more featureful. Examples:
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- multiple watchers can wait for the same event without deregistering others.
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- fork() is supported and can be handled.
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- timers are handled as a priority queue (faster)
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- watchers use less memory (faster)
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- less calls to epoll_ctl (faster)
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(registering two read events on fd 10 and unregistering one will not
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break the other)
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- fork() is supported and can be handled
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(there is no way to recover from a fork when libevent is active)
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- timers are handled as a priority queue
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(libevent uses a less efficient red-black tree)
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- supports absolute (wallclock-based) timers in addition to relative ones,
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i.e. can schedule timers to occur after n seconds, or at a specific time.
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- timers can be repeating (both absolute and relative ones)
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- detects time jumps and adjusts timers
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(works for both forward and backward time jumps and also for absolute timers)
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- can correctly remove timers while executing callbacks
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(libevent doesn't handle this reliably and can crash)
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- less calls to epoll_ctl
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(stopping and starting an io watcher between two loop iterations will now
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result in spuriois epoll_ctl calls)
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- usually less calls to gettimeofday and clock_gettime
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(libevent calls it on every timer event change, libev twice per iteration)
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- watchers use less memory
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(libevent on amd64: 152 bytes, libev: <= 56 bytes)
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- library uses less memory
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(libevent allocates large data structures wether used or not, libev
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scales all its data structures dynamically)
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- no hardcoded arbitrary limits
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(libevent contains an off-by-one bug and sometimes hardcodes a limit of
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32000 fds)
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- libev separates timer, signal and io watchers from each other
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(libevent combines them, but with libev you can combine them yourself
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by reusing the same callback and still save memory)
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- simpler design, backends are potentially much simpler
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(in libevent, backends have to deal with watchers, thus the problems)
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(epoll backend in libevent: 366 lines, libev: 89 lines, and more features)
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whats missing?
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- evdns, evhttp, bufferevent are missing, libev is only an even library at
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the moment.
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- no priority support at the moment.
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- kqueue, poll (libev currently implements epoll and select).
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166
ev.c
166
ev.c
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@ -3,6 +3,7 @@
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#include <stdio.h>
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#include <assert.h>
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#include <errno.h>
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#include <sys/time.h>
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#include <time.h>
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@ -15,6 +16,7 @@
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#define HAVE_REALTIME 1
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#define HAVE_SELECT 0
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#define MIN_TIMEJUMP 1. /* minimum timejump that gets detected (if monotonic clock available) */
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#define MAX_BLOCKTIME 60.
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#include "ev.h"
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@ -27,6 +29,7 @@ struct ev_watcher_list {
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EV_WATCHER_LIST (ev_watcher_list);
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};
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static ev_tstamp now, diff; /* monotonic clock */
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ev_tstamp ev_now;
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int ev_method;
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@ -131,11 +134,14 @@ fd_event (int fd, int events)
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}
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}
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static struct ev_timer **timers;
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static int timermax, timercnt;
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static struct ev_timer **atimers;
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static int atimermax, atimercnt;
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static struct ev_timer **rtimers;
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static int rtimermax, rtimercnt;
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static void
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upheap (int k)
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upheap (struct ev_timer **timers, int k)
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{
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struct ev_timer *w = timers [k];
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@ -152,15 +158,15 @@ upheap (int k)
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}
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static void
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downheap (int k)
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downheap (struct ev_timer **timers, int N, int k)
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{
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struct ev_timer *w = timers [k];
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while (k < (timercnt >> 1))
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while (k < (N >> 1))
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{
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int j = k << 1;
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if (j + 1 < timercnt && timers [j]->at > timers [j + 1]->at)
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if (j + 1 < N && timers [j]->at > timers [j + 1]->at)
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++j;
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if (w->at <= timers [j]->at)
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@ -176,7 +182,7 @@ downheap (int k)
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}
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static struct ev_signal **signals;
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static int signalmax, signalcnt;
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static int signalmax;
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static void
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signals_init (struct ev_signal **base, int count)
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@ -203,6 +209,8 @@ int ev_init (int flags)
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#endif
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ev_now = ev_time ();
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now = get_clock ();
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diff = ev_now - now;
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#if HAVE_EPOLL
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if (epoll_init (flags))
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@ -252,32 +260,77 @@ call_pending ()
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}
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static void
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timer_reify (void)
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timers_reify (struct ev_timer **timers, int timercnt, ev_tstamp now)
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{
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while (timercnt && timers [0]->at <= ev_now)
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while (timercnt && timers [0]->at <= now)
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{
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struct ev_timer *w = timers [0];
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/* first reschedule timer */
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/* first reschedule or stop timer */
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if (w->repeat)
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{
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if (w->is_abs)
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w->at += ceil ((ev_now - w->at) / w->repeat + 1.) * w->repeat;
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w->at += floor ((now - w->at) / w->repeat + 1.) * w->repeat;
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else
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w->at = ev_now + w->repeat;
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w->at = now + w->repeat;
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downheap (0);
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assert (w->at > now);
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downheap (timers, timercnt, 0);
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}
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else
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evtimer_stop (w); /* nonrepeating: stop timer */
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{
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evtimer_stop (w); /* nonrepeating: stop timer */
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--timercnt; /* maybe pass by reference instead? */
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}
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event ((struct ev_watcher *)w, EV_TIMEOUT);
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}
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}
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static void
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time_update ()
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{
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int i;
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ev_now = ev_time ();
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if (have_monotonic)
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{
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ev_tstamp odiff = diff;
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/* detecting time jumps is much more difficult */
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for (i = 2; --i; ) /* loop a few times, before making important decisions */
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{
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now = get_clock ();
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diff = ev_now - now;
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if (fabs (odiff - diff) < MIN_TIMEJUMP)
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return; /* all is well */
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ev_now = ev_time ();
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}
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/* time jump detected, reschedule atimers */
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for (i = 0; i < atimercnt; ++i)
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{
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struct ev_timer *w = atimers [i];
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w->at += ceil ((ev_now - w->at) / w->repeat + 1.) * w->repeat;
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}
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}
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else
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{
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if (now > ev_now || now < ev_now - MAX_BLOCKTIME - MIN_TIMEJUMP)
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/* time jump detected, adjust rtimers */
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for (i = 0; i < rtimercnt; ++i)
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rtimers [i]->at += ev_now - now;
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now = ev_now;
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}
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}
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int ev_loop_done;
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int ev_loop (int flags)
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void ev_loop (int flags)
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{
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double block;
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ev_loop_done = flags & EVLOOP_ONESHOT;
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@ -288,25 +341,38 @@ int ev_loop (int flags)
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method_reify (); fdchangecnt = 0;
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/* calculate blocking time */
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ev_now = ev_time ();
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if (flags & EVLOOP_NONBLOCK)
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block = 0.;
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else if (!timercnt)
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block = MAX_BLOCKTIME;
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else
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{
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block = timers [0]->at - ev_now + method_fudge;
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block = MAX_BLOCKTIME;
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if (rtimercnt)
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{
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ev_tstamp to = rtimers [0]->at - get_clock () + method_fudge;
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if (block > to) block = to;
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}
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if (atimercnt)
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{
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ev_tstamp to = atimers [0]->at - ev_time () + method_fudge;
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if (block > to) block = to;
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}
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if (block < 0.) block = 0.;
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else if (block > MAX_BLOCKTIME) block = MAX_BLOCKTIME;
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}
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method_poll (block);
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/* put pending timers into pendign queue and reschedule them */
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timer_reify ();
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/* update ev_now, do magic */
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time_update ();
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/* put pending timers into pendign queue and reschedule them */
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/* absolute timers first */
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timers_reify (atimers, atimercnt, ev_now);
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/* relative timers second */
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timers_reify (rtimers, rtimercnt, now);
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ev_now = ev_time ();
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call_pending ();
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}
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while (!ev_loop_done);
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@ -393,14 +459,22 @@ evtimer_start (struct ev_timer *w)
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/* this formula differs from the one in timer_reify becuse we do not round up */
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if (w->repeat)
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w->at += ceil ((ev_now - w->at) / w->repeat) * w->repeat;
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ev_start ((struct ev_watcher *)w, ++atimercnt);
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array_needsize (atimers, atimermax, atimercnt, );
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atimers [atimercnt - 1] = w;
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upheap (atimers, atimercnt - 1);
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}
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else
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w->at += ev_now;
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{
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w->at += now;
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ev_start ((struct ev_watcher *)w, ++rtimercnt);
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array_needsize (rtimers, rtimermax, rtimercnt, );
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rtimers [rtimercnt - 1] = w;
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upheap (rtimers, rtimercnt - 1);
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}
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ev_start ((struct ev_watcher *)w, ++timercnt);
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array_needsize (timers, timermax, timercnt, );
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timers [timercnt - 1] = w;
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upheap (timercnt - 1);
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}
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void
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if (!ev_is_active (w))
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return;
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if (w->active < timercnt--)
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if (w->is_abs)
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{
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timers [w->active - 1] = timers [timercnt];
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downheap (w->active - 1);
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if (w->active < atimercnt--)
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{
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atimers [w->active - 1] = atimers [atimercnt];
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downheap (atimers, atimercnt, w->active - 1);
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}
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}
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else
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{
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if (w->active < rtimercnt--)
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{
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rtimers [w->active - 1] = rtimers [rtimercnt];
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downheap (rtimers, rtimercnt, w->active - 1);
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}
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}
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ev_stop ((struct ev_watcher *)w);
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static void
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ocb (struct ev_timer *w, int revents)
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{
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fprintf (stderr, "timer %f,%f (%x) (%f) d%p\n", w->at, w->repeat, revents, w->at - ev_time (), w->data);
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//fprintf (stderr, "timer %f,%f (%x) (%f) d%p\n", w->at, w->repeat, revents, w->at - ev_time (), w->data);
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evtimer_stop (w);
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evtimer_start (w);
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}
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int main (void)
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evio_set (&sin, 0, EV_READ);
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evio_start (&sin);
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struct ev_timer t[1000];
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struct ev_timer t[10000];
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#if 1
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int i;
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for (i = 0; i < 1000; ++i)
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for (i = 0; i < 10000; ++i)
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{
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struct ev_timer *w = t + i;
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evw_init (w, ocb, i);
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evtimer_set_rel (w, drand48 (), 0);
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evtimer_set_abs (w, drand48 (), 0.99775533);
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evtimer_start (w);
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if (drand48 () < 0.5)
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evtimer_stop (w);
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}
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#endif
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struct ev_timer t1;
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evw_init (&t1, ocb, 0);
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evtimer_set_abs (&t1, 5, 10);
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evtimer_start (&t1);
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ev_loop (0);
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7
ev.h
7
ev.h
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@ -26,9 +26,9 @@ struct ev_timer
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{
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EV_WATCHER_LIST (ev_timer);
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ev_tstamp at; /* ro */
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ev_tstamp at; /* private */
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ev_tstamp repeat; /* rw */
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unsigned char is_abs; /* rw */
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unsigned char is_abs; /* ro */
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};
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struct ev_io
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#define EVLOOP_NONBLOCK 1 /* do not block/wait */
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#define EVLOOP_ONESHOT 2 /* block *once* only */
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int ev_loop (int flags);
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void ev_loop (int flags);
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extern int ev_loop_done; /* set to 1 to break out of event loop */
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/* these may evaluate ev multiple times, and the other arguments at most once */
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#define evw_init(ev,cb_,data_) do { (ev)->active = 0; (ev)->cb = (cb_); (ev)->data = (void *)data_; } while (0)
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#define evio_set(ev,fd_,events_) do { (ev)->fd = (fd_); (ev)->events = (events_); } while (0)
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#define evtimer_set_rel(ev,after_,repeat_) do { (ev)->at = (after_); (ev)->repeat = (repeat_); (ev)->is_abs = 0; } while (0)
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#define evtimer_set_abs(ev,at_,repeat_) do { (ev)->at = (at_); (ev)->repeat = (repeat_); (ev)->is_abs = 1; } while (0)
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