/*  $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $ */

/*

 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>

 * Copyright 2007-2012 Niels Provos and Nick Mathewson

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. 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.

 * 3. The name of the author may not be used to endorse or promote products

 *    derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.

 */

#include "event2/event-config.h"

#include "evconfig-private.h"

#ifdef EVENT__HAVE_SELECT

#ifdef __APPLE__

/* Apple wants us to define this if we might ever pass more than

 * FD_SETSIZE bits to select(). */

#define _DARWIN_UNLIMITED_SELECT

#endif

#include <sys/types.h>

#ifdef EVENT__HAVE_SYS_TIME_H

#include <sys/time.h>

#endif

#ifdef EVENT__HAVE_SYS_SELECT_H

#include <sys/select.h>

#endif

#include <sys/queue.h>

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <errno.h>

#include "event-internal.h"

#include "evsignal-internal.h"

#include "event2/thread.h"

#include "evthread-internal.h"

#include "log-internal.h"

#include "evmap-internal.h"

#ifndef EVENT__HAVE_FD_MASK

/* This type is mandatory, but Android doesn't define it. */

typedef unsigned long fd_mask;

#endif

#ifndef NFDBITS

#define NFDBITS (sizeof(fd_mask)*8)

#endif

/* Divide positive x by y, rounding up. */

#define DIV_ROUNDUP(x, y)   (((x)+((y)-1))/(y))

/* How many bytes to allocate for N fds? */

#define SELECT_ALLOC_SIZE(n) \

  (DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))

struct selectop {

  int event_fds;    /* Highest fd in fd set */

  int event_fdsz;

  int resize_out_sets;

  fd_set *event_readset_in;

  fd_set *event_writeset_in;

  fd_set *event_readset_out;

  fd_set *event_writeset_out;

};

static void *select_init(struct event_base *);

static int select_add(struct event_base *, int, short old, short events, void*);

static int select_del(struct event_base *, int, short old, short events, void*);

static int select_dispatch(struct event_base *, struct timeval *);

static void select_dealloc(struct event_base *);

const struct eventop selectops = {

  "select",

  select_init,

  select_add,

  select_del,

  select_dispatch,

  select_dealloc,

  1, /* need_reinit. */

  EV_FEATURE_FDS,

  0,

};

static int select_resize(struct selectop *sop, int fdsz);

static void select_free_selectop(struct selectop *sop);

static void *

select_init(struct event_base *base)

{

  struct selectop *sop;

  if (!(sop = mm_calloc(1, sizeof(struct selectop))))

    return (NULL);

  if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {

    select_free_selectop(sop);

    return (NULL);

  }

  if (sigfd_init_(base) < 0)

    evsig_init_(base);

  evutil_weakrand_seed_(&base->weakrand_seed, 0);

  return (sop);

}

#ifdef CHECK_INVARIANTS

static void

check_selectop(struct selectop *sop)

{

  /* nothing to be done here */

}

#else

#define check_selectop(sop) do { (void) sop; } while (0)

#endif

static int

select_dispatch(struct event_base *base, struct timeval *tv)

{

  int res=0, i, j, nfds;

  struct selectop *sop = base->evbase;

  check_selectop(sop);

  if (sop->resize_out_sets) {

    fd_set *readset_out=NULL, *writeset_out=NULL;

    size_t sz = sop->event_fdsz;

    if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))

      return (-1);

    sop->event_readset_out = readset_out;

    if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {

      /* We don't free readset_out here, since it was

       * already successfully reallocated. The next time

       * we call select_dispatch, the realloc will be a

       * no-op. */

      return (-1);

    }

    sop->event_writeset_out = writeset_out;

    sop->resize_out_sets = 0;

  }

  memcpy(sop->event_readset_out, sop->event_readset_in,

         sop->event_fdsz);

  memcpy(sop->event_writeset_out, sop->event_writeset_in,

         sop->event_fdsz);

  nfds = sop->event_fds+1;

  EVBASE_RELEASE_LOCK(base, th_base_lock);

  res = select(nfds, sop->event_readset_out,

      sop->event_writeset_out, NULL, tv);

  EVBASE_ACQUIRE_LOCK(base, th_base_lock);

  check_selectop(sop);

  if (res == -1) {

    if (errno != EINTR) {

      event_warn("select");

      return (-1);

    }

    return (0);

  }

  event_debug(("%s: select reports %d", __func__, res));

  check_selectop(sop);

  i = evutil_weakrand_range_(&base->weakrand_seed, nfds);

  for (j = 0; j < nfds; ++j) {

    if (++i >= nfds)

      i = 0;

    res = 0;

    if (FD_ISSET(i, sop->event_readset_out))

      res |= EV_READ;

    if (FD_ISSET(i, sop->event_writeset_out))

      res |= EV_WRITE;

    if (res == 0)

      continue;

    evmap_io_active_(base, i, res);

  }

  check_selectop(sop);

  return (0);

}

static int

select_resize(struct selectop *sop, int fdsz)

{

  fd_set *readset_in = NULL;

  fd_set *writeset_in = NULL;

  if (sop->event_readset_in)

    check_selectop(sop);

  if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)

    goto error;

  sop->event_readset_in = readset_in;

  if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {

    /* Note that this will leave event_readset_in expanded.

     * That's okay; we wouldn't want to free it, since that would

     * change the semantics of select_resize from "expand the

     * readset_in and writeset_in, or return -1" to "expand the

     * *set_in members, or trash them and return -1."

     */

    goto error;

  }

  sop->event_writeset_in = writeset_in;

  sop->resize_out_sets = 1;

  memset((char *)sop->event_readset_in + sop->event_fdsz, 0,

      fdsz - sop->event_fdsz);

  memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,

      fdsz - sop->event_fdsz);

  sop->event_fdsz = fdsz;

  check_selectop(sop);

  return (0);

 error:

  event_warn("malloc");

  return (-1);

}

static int

select_add(struct event_base *base, int fd, short old, short events, void *p)

{

  struct selectop *sop = base->evbase;

  (void) p;

  EVUTIL_ASSERT((events & EV_SIGNAL) == 0);

  check_selectop(sop);

  /*

   * Keep track of the highest fd, so that we can calculate the size

   * of the fd_sets for select(2)

   */

  if (sop->event_fds < fd) {

    int fdsz = sop->event_fdsz;

    if (fdsz < (int)sizeof(fd_mask))

      fdsz = (int)sizeof(fd_mask);

    /* In theory we should worry about overflow here.  In

     * reality, though, the highest fd on a unixy system will

     * not overflow here. XXXX */

    while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))

      fdsz *= 2;

    if (fdsz != sop->event_fdsz) {

      if (select_resize(sop, fdsz)) {

        check_selectop(sop);

        return (-1);

      }

    }

    sop->event_fds = fd;

  }

  if (events & EV_READ)

    FD_SET(fd, sop->event_readset_in);

  if (events & EV_WRITE)

    FD_SET(fd, sop->event_writeset_in);

  check_selectop(sop);

  return (0);

}

/*

 * Nothing to be done here.

 */

static int

select_del(struct event_base *base, int fd, short old, short events, void *p)

{

  struct selectop *sop = base->evbase;

  (void)p;

  EVUTIL_ASSERT((events & EV_SIGNAL) == 0);

  check_selectop(sop);

  if (sop->event_fds < fd) {

    check_selectop(sop);

    return (0);

  }

  if (events & EV_READ)

    FD_CLR(fd, sop->event_readset_in);

  if (events & EV_WRITE)

    FD_CLR(fd, sop->event_writeset_in);

  check_selectop(sop);

  return (0);

}

static void

select_free_selectop(struct selectop *sop)

{

  if (sop->event_readset_in)

    mm_free(sop->event_readset_in);

  if (sop->event_writeset_in)

    mm_free(sop->event_writeset_in);

  if (sop->event_readset_out)

    mm_free(sop->event_readset_out);

  if (sop->event_writeset_out)

    mm_free(sop->event_writeset_out);

  memset(sop, 0, sizeof(struct selectop));

  mm_free(sop);

}

static void

select_dealloc(struct event_base *base)

{

  evsig_dealloc_(base);

  select_free_selectop(base->evbase);

}

#endif /* EVENT__HAVE_SELECT */