libev/ev.c

/*
 * libev event processing core, watcher management
 *
 * Copyright (c) 2007 Marc Alexander Lehmann <libev@schmorp.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#if EV_USE_CONFIG_H
# include "config.h"
#endif

#include <math.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <stddef.h>

#include <stdio.h>

#include <assert.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <time.h>

#ifndef EV_USE_MONOTONIC
# define EV_USE_MONOTONIC 1
#endif

#ifndef CLOCK_MONOTONIC
# undef EV_USE_MONOTONIC
# define EV_USE_MONOTONIC 0
#endif

#ifndef EV_USE_SELECT
# define EV_USE_SELECT 1
#endif

#ifndef EV_USE_EPOLL
# define EV_USE_EPOLL 0
#endif

#ifndef CLOCK_REALTIME
# define EV_USE_REALTIME 0
#endif
#ifndef EV_USE_REALTIME
# define EV_USE_REALTIME 1 /* posix requirement, but might be slower */
#endif

#define MIN_TIMEJUMP  1. /* minimum timejump that gets detected (if monotonic clock available) */
#define MAX_BLOCKTIME 59.731 /* never wait longer than this time (to detetc time jumps) */
#define PID_HASHSIZE  16 /* size of pid hash table, must be power of two */
#define CLEANUP_INTERVAL (MAX_BLOCKTIME * 5.) /* how often to try to free memory and re-check fds */

#include "ev.h"

typedef struct ev_watcher *W;
typedef struct ev_watcher_list *WL;
typedef struct ev_watcher_time *WT;

static ev_tstamp now, diff; /* monotonic clock */
ev_tstamp ev_now;
int ev_method;

static int have_monotonic; /* runtime */

static ev_tstamp method_fudge; /* stupid epoll-returns-early bug */
static void (*method_modify)(int fd, int oev, int nev);
static void (*method_poll)(ev_tstamp timeout);

/*****************************************************************************/

ev_tstamp
ev_time (void)
{
#if EV_USE_REALTIME
  struct timespec ts;
  clock_gettime (CLOCK_REALTIME, &ts);
  return ts.tv_sec + ts.tv_nsec * 1e-9;
#else
  struct timeval tv;
  gettimeofday (&tv, 0);
  return tv.tv_sec + tv.tv_usec * 1e-6;
#endif
}

static ev_tstamp
get_clock (void)
{
#if EV_USE_MONOTONIC
  if (have_monotonic)
    {
      struct timespec ts;
      clock_gettime (CLOCK_MONOTONIC, &ts);
      return ts.tv_sec + ts.tv_nsec * 1e-9;
    }
#endif

  return ev_time ();
}

#define array_roundsize(base,n) ((n) | 4 & ~3)

#define array_needsize(base,cur,cnt,init)		\
  if ((cnt) > cur)					\
    {							\
      int newcnt = cur;					\
      do						\
        {						\
          newcnt = array_roundsize (base, newcnt << 1);	\
        }						\
      while ((cnt) > newcnt);				\
      							\
      base = realloc (base, sizeof (*base) * (newcnt));	\
      init (base + cur, newcnt - cur);			\
      cur = newcnt;					\
    }

/*****************************************************************************/

typedef struct
{
  struct ev_io *head;
  unsigned char events;
  unsigned char reify;
} ANFD;

static ANFD *anfds;
static int anfdmax;

static void
anfds_init (ANFD *base, int count)
{
  while (count--)
    {
      base->head   = 0;
      base->events = EV_NONE;
      base->reify  = 0;

      ++base;
    }
}

typedef struct
{
  W w;
  int events;
} ANPENDING;

static ANPENDING *pendings;
static int pendingmax, pendingcnt;

static void
event (W w, int events)
{
  if (w->pending)
    {
      pendings [w->pending - 1].events |= events;
      return;
    }

  w->pending = ++pendingcnt;
  array_needsize (pendings, pendingmax, pendingcnt, );
  pendings [pendingcnt - 1].w      = w;
  pendings [pendingcnt - 1].events = events;
}

static void
queue_events (W *events, int eventcnt, int type)
{
  int i;

  for (i = 0; i < eventcnt; ++i)
    event (events [i], type);
}

static void
fd_event (int fd, int events)
{
  ANFD *anfd = anfds + fd;
  struct ev_io *w;

  for (w = anfd->head; w; w = w->next)
    {
      int ev = w->events & events;

      if (ev)
        event ((W)w, ev);
    }
}

/*****************************************************************************/

static int *fdchanges;
static int fdchangemax, fdchangecnt;

static void
fd_reify (void)
{
  int i;

  for (i = 0; i < fdchangecnt; ++i)
    {
      int fd = fdchanges [i];
      ANFD *anfd = anfds + fd;
      struct ev_io *w;

      int events = 0;

      for (w = anfd->head; w; w = w->next)
        events |= w->events;

      anfd->reify = 0;

      if (anfd->events != events)
        {
          method_modify (fd, anfd->events, events);
          anfd->events = events;
        }
    }

  fdchangecnt = 0;
}

static void
fd_change (int fd)
{
  if (anfds [fd].reify || fdchangecnt < 0)
    return;

  anfds [fd].reify = 1;

  ++fdchangecnt;
  array_needsize (fdchanges, fdchangemax, fdchangecnt, );
  fdchanges [fdchangecnt - 1] = fd;
}

/* called on EBADF to verify fds */
static void
fd_recheck (void)
{
  int fd;

  for (fd = 0; fd < anfdmax; ++fd)
    if (anfds [fd].events)
      if (fcntl (fd, F_GETFD) == -1 && errno == EBADF)
        while (anfds [fd].head)
          {
            ev_io_stop (anfds [fd].head);
            event ((W)anfds [fd].head, EV_ERROR | EV_READ | EV_WRITE);
          }
}

/*****************************************************************************/

static struct ev_timer **timers;
static int timermax, timercnt;

static struct ev_periodic **periodics;
static int periodicmax, periodiccnt;

static void
upheap (WT *timers, int k)
{
  WT w = timers [k];

  while (k && timers [k >> 1]->at > w->at)
    {
      timers [k] = timers [k >> 1];
      timers [k]->active = k + 1;
      k >>= 1;
    }

  timers [k] = w;
  timers [k]->active = k + 1;

}

static void
downheap (WT *timers, int N, int k)
{
  WT w = timers [k];

  while (k < (N >> 1))
    {
      int j = k << 1;

      if (j + 1 < N && timers [j]->at > timers [j + 1]->at)
        ++j;

      if (w->at <= timers [j]->at)
        break;

      timers [k] = timers [j];
      timers [k]->active = k + 1;
      k = j;
    }

  timers [k] = w;
  timers [k]->active = k + 1;
}

/*****************************************************************************/

typedef struct
{
  struct ev_signal *head;
  sig_atomic_t volatile gotsig;
} ANSIG;

static ANSIG *signals;
static int signalmax;

static int sigpipe [2];
static sig_atomic_t volatile gotsig;
static struct ev_io sigev;

static void
signals_init (ANSIG *base, int count)
{
  while (count--)
    {
      base->head   = 0;
      base->gotsig = 0;

      ++base;
    }
}

static void
sighandler (int signum)
{
  signals [signum - 1].gotsig = 1;

  if (!gotsig)
    {
      gotsig = 1;
      write (sigpipe [1], &signum, 1);
    }
}

static void
sigcb (struct ev_io *iow, int revents)
{
  struct ev_signal *w;
  int signum;

  read (sigpipe [0], &revents, 1);
  gotsig = 0;

  for (signum = signalmax; signum--; )
    if (signals [signum].gotsig)
      {
        signals [signum].gotsig = 0;

        for (w = signals [signum].head; w; w = w->next)
          event ((W)w, EV_SIGNAL);
      }
}

static void
siginit (void)
{
  fcntl (sigpipe [0], F_SETFD, FD_CLOEXEC);
  fcntl (sigpipe [1], F_SETFD, FD_CLOEXEC);

  /* rather than sort out wether we really need nb, set it */
  fcntl (sigpipe [0], F_SETFL, O_NONBLOCK);
  fcntl (sigpipe [1], F_SETFL, O_NONBLOCK);

  ev_io_set (&sigev, sigpipe [0], EV_READ);
  ev_io_start (&sigev);
}

/*****************************************************************************/

static struct ev_idle **idles;
static int idlemax, idlecnt;

static struct ev_prepare **prepares;
static int preparemax, preparecnt;

static struct ev_check **checks;
static int checkmax, checkcnt;

/*****************************************************************************/

static struct ev_child *childs [PID_HASHSIZE];
static struct ev_signal childev;

#ifndef WCONTINUED
# define WCONTINUED 0
#endif

static void
childcb (struct ev_signal *sw, int revents)
{
  struct ev_child *w;
  int pid, status;

  while ((pid = waitpid (-1, &status, WNOHANG | WUNTRACED | WCONTINUED)) != -1)
    for (w = childs [pid & (PID_HASHSIZE - 1)]; w; w = w->next)
      if (w->pid == pid || !w->pid)
        {
          w->status = status;
          event ((W)w, EV_CHILD);
        }
}

/*****************************************************************************/

#if EV_USE_EPOLL
# include "ev_epoll.c"
#endif
#if EV_USE_SELECT
# include "ev_select.c"
#endif

int
ev_version_major (void)
{
  return EV_VERSION_MAJOR;
}

int
ev_version_minor (void)
{
  return EV_VERSION_MINOR;
}

int ev_init (int flags)
{
  if (!ev_method)
    {
#if EV_USE_MONOTONIC
      {
        struct timespec ts;
        if (!clock_gettime (CLOCK_MONOTONIC, &ts))
          have_monotonic = 1;
      }
#endif

      ev_now = ev_time ();
      now    = get_clock ();
      diff   = ev_now - now;

      if (pipe (sigpipe))
        return 0;

      ev_method = EVMETHOD_NONE;
#if EV_USE_EPOLL
      if (ev_method == EVMETHOD_NONE) epoll_init (flags);
#endif
#if EV_USE_SELECT
      if (ev_method == EVMETHOD_NONE) select_init (flags);
#endif

      if (ev_method)
        {
          ev_watcher_init (&sigev, sigcb);
          siginit ();

          ev_signal_init (&childev, childcb, SIGCHLD);
          ev_signal_start (&childev);
        }
    }

  return ev_method;
}

/*****************************************************************************/

void
ev_fork_prepare (void)
{
  /* nop */
}

void
ev_fork_parent (void)
{
  /* nop */
}

void
ev_fork_child (void)
{
#if EV_USE_EPOLL
  if (ev_method == EVMETHOD_EPOLL)
    epoll_postfork_child ();
#endif

  ev_io_stop (&sigev);
  close (sigpipe [0]);
  close (sigpipe [1]);
  pipe (sigpipe);
  siginit ();
}

/*****************************************************************************/

static void
call_pending (void)
{
  while (pendingcnt)
    {
      ANPENDING *p = pendings + --pendingcnt;

      if (p->w)
        {
          p->w->pending = 0;
          p->w->cb (p->w, p->events);
        }
    }
}

static void
timers_reify (void)
{
  while (timercnt && timers [0]->at <= now)
    {
      struct ev_timer *w = timers [0];

      /* first reschedule or stop timer */
      if (w->repeat)
        {
          assert (("negative ev_timer repeat value found while processing timers", w->repeat > 0.));
          w->at = now + w->repeat;
          downheap ((WT *)timers, timercnt, 0);
        }
      else
        ev_timer_stop (w); /* nonrepeating: stop timer */

      event ((W)w, EV_TIMEOUT);
    }
}

static void
periodics_reify (void)
{
  while (periodiccnt && periodics [0]->at <= ev_now)
    {
      struct ev_periodic *w = periodics [0];

      /* first reschedule or stop timer */
      if (w->interval)
        {
          w->at += floor ((ev_now - w->at) / w->interval + 1.) * w->interval;
          assert (("ev_periodic timeout in the past detected while processing timers, negative interval?", w->at > ev_now));
          downheap ((WT *)periodics, periodiccnt, 0);
        }
      else
        ev_periodic_stop (w); /* nonrepeating: stop timer */

      event ((W)w, EV_PERIODIC);
    }
}

static void
periodics_reschedule (ev_tstamp diff)
{
  int i;

  /* adjust periodics after time jump */
  for (i = 0; i < periodiccnt; ++i)
    {
      struct ev_periodic *w = periodics [i];

      if (w->interval)
        {
          ev_tstamp diff = ceil ((ev_now - w->at) / w->interval) * w->interval;

          if (fabs (diff) >= 1e-4)
            {
              ev_periodic_stop (w);
              ev_periodic_start (w);

              i = 0; /* restart loop, inefficient, but time jumps should be rare */
            }
        }
    }
}

static void
time_update (void)
{
  int i;

  ev_now = ev_time ();

  if (have_monotonic)
    {
      ev_tstamp odiff = diff;

      for (i = 4; --i; ) /* loop a few times, before making important decisions */
        {
          now = get_clock ();
          diff = ev_now - now;

          if (fabs (odiff - diff) < MIN_TIMEJUMP)
            return; /* all is well */

          ev_now = ev_time ();
        }

      periodics_reschedule (diff - odiff);
      /* no timer adjustment, as the monotonic clock doesn't jump */
    }
  else
    {
      if (now > ev_now || now < ev_now - MAX_BLOCKTIME - MIN_TIMEJUMP)
        {
          periodics_reschedule (ev_now - now);

          /* adjust timers. this is easy, as the offset is the same for all */
          for (i = 0; i < timercnt; ++i)
            timers [i]->at += diff;
        }

      now = ev_now;
    }
}

int ev_loop_done;

void ev_loop (int flags)
{
  double block;
  ev_loop_done = flags & (EVLOOP_ONESHOT | EVLOOP_NONBLOCK) ? 1 : 0;

  do
    {
      /* queue check watchers (and execute them) */
      if (preparecnt)
        {
          queue_events ((W *)prepares, preparecnt, EV_PREPARE);
          call_pending ();
        }

      /* update fd-related kernel structures */
      fd_reify ();

      /* calculate blocking time */

      /* we only need this for !monotonic clockor timers, but as we basically
         always have timers, we just calculate it always */
      ev_now = ev_time ();

      if (flags & EVLOOP_NONBLOCK || idlecnt)
        block = 0.;
      else
        {
          block = MAX_BLOCKTIME;

          if (timercnt)
            {
              ev_tstamp to = timers [0]->at - (have_monotonic ? get_clock () : ev_now) + method_fudge;
              if (block > to) block = to;
            }

          if (periodiccnt)
            {
              ev_tstamp to = periodics [0]->at - ev_now + method_fudge;
              if (block > to) block = to;
            }

          if (block < 0.) block = 0.;
        }

      method_poll (block);

      /* update ev_now, do magic */
      time_update ();

      /* queue pending timers and reschedule them */
      timers_reify (); /* relative timers called last */
      periodics_reify (); /* absolute timers called first */

      /* queue idle watchers unless io or timers are pending */
      if (!pendingcnt)
        queue_events ((W *)idles, idlecnt, EV_IDLE);

      /* queue check watchers, to be executed first */
      if (checkcnt)
        queue_events ((W *)checks, checkcnt, EV_CHECK);

      call_pending ();
    }
  while (!ev_loop_done);

  if (ev_loop_done != 2)
    ev_loop_done = 0;
}

/*****************************************************************************/

static void
wlist_add (WL *head, WL elem)
{
  elem->next = *head;
  *head = elem;
}

static void
wlist_del (WL *head, WL elem)
{
  while (*head)
    {
      if (*head == elem)
        {
          *head = elem->next;
          return;
        }

      head = &(*head)->next;
    }
}

static void
ev_clear_pending (W w)
{
  if (w->pending)
    {
      pendings [w->pending - 1].w = 0;
      w->pending = 0;
    }
}

static void
ev_start (W w, int active)
{
  w->active = active;
}

static void
ev_stop (W w)
{
  w->active = 0;
}

/*****************************************************************************/

void
ev_io_start (struct ev_io *w)
{
  int fd = w->fd;

  if (ev_is_active (w))
    return;

  assert (("ev_io_start called with negative fd", fd >= 0));

  ev_start ((W)w, 1);
  array_needsize (anfds, anfdmax, fd + 1, anfds_init);
  wlist_add ((WL *)&anfds[fd].head, (WL)w);

  fd_change (fd);
}

void
ev_io_stop (struct ev_io *w)
{
  ev_clear_pending ((W)w);
  if (!ev_is_active (w))
    return;

  wlist_del ((WL *)&anfds[w->fd].head, (WL)w);
  ev_stop ((W)w);

  fd_change (w->fd);
}

void
ev_timer_start (struct ev_timer *w)
{
  if (ev_is_active (w))
    return;

  w->at += now;

  assert (("ev_timer_start called with negative timer repeat value", w->repeat >= 0.));

  ev_start ((W)w, ++timercnt);
  array_needsize (timers, timermax, timercnt, );