/*

 * Copyright (c) 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 _WIN32

#include <winsock2.h>

#define WIN32_LEAN_AND_MEAN

#include <windows.h>

#undef WIN32_LEAN_AND_MEAN

#endif

#include <sys/types.h>

#if !defined(_WIN32) && defined(EVENT__HAVE_SYS_TIME_H)

#include <sys/time.h>

#endif

#include <sys/queue.h>

#include <stdio.h>

#include <stdlib.h>

#ifndef _WIN32

#include <unistd.h>

#endif

#include <errno.h>

#include <limits.h>

#include <signal.h>

#include <string.h>

#include <time.h>

#include "event-internal.h"

#include "evmap-internal.h"

#include "mm-internal.h"

#include "changelist-internal.h"

/** An entry for an evmap_io list: notes all the events that want to read or

  write on a given fd, and the number of each.

  */

struct evmap_io {

  struct event_dlist events;

  ev_uint16_t nread;

  ev_uint16_t nwrite;

  ev_uint16_t nclose;

};

/* An entry for an evmap_signal list: notes all the events that want to know

   when a signal triggers. */

struct evmap_signal {

  struct event_dlist events;

};

/* On some platforms, fds start at 0 and increment by 1 as they are

   allocated, and old numbers get used.  For these platforms, we

   implement io maps just like signal maps: as an array of pointers to

   struct evmap_io.  But on other platforms (windows), sockets are not

   0-indexed, not necessarily consecutive, and not necessarily reused.

   There, we use a hashtable to implement evmap_io.

*/

#ifdef EVMAP_USE_HT

struct event_map_entry {

  HT_ENTRY(event_map_entry) map_node;

  evutil_socket_t fd;

  union { /* This is a union in case we need to make more things that can

         be in the hashtable. */

    struct evmap_io evmap_io;

  } ent;

};

/* Helper used by the event_io_map hashtable code; tries to return a good hash

 * of the fd in e->fd. */

static inline unsigned

hashsocket(struct event_map_entry *e)

{

  /* On win32, in practice, the low 2-3 bits of a SOCKET seem not to

   * matter.  Our hashtable implementation really likes low-order bits,

   * though, so let's do the rotate-and-add trick. */

  unsigned h = (unsigned) e->fd;

  h += (h >> 2) | (h << 30);

  return h;

}

/* Helper used by the event_io_map hashtable code; returns true iff e1 and e2

 * have the same e->fd. */

static inline int

eqsocket(struct event_map_entry *e1, struct event_map_entry *e2)

{

  return e1->fd == e2->fd;

}

HT_PROTOTYPE(event_io_map, event_map_entry, map_node, hashsocket, eqsocket)

HT_GENERATE(event_io_map, event_map_entry, map_node, hashsocket, eqsocket,

      0.5, mm_malloc, mm_realloc, mm_free)

#define GET_IO_SLOT(x, map, slot, type)         \

  do {                \

    struct event_map_entry key_, *ent_;     \

    key_.fd = slot;           \

    ent_ = HT_FIND(event_io_map, map, &key_);   \

    (x) = ent_ ? &ent_->ent.type : NULL;      \

  } while (0);

#define GET_IO_SLOT_AND_CTOR(x, map, slot, type, ctor, fdinfo_len)  \

  do {                \

    struct event_map_entry key_, *ent_;     \

    key_.fd = slot;           \

    HT_FIND_OR_INSERT_(event_io_map, map_node, hashsocket, map, \

        event_map_entry, &key_, ptr,      \

        {             \

          ent_ = *ptr;        \

        },              \

        {             \

          ent_ = mm_calloc(1,sizeof(struct event_map_entry)+fdinfo_len); \

          if (EVUTIL_UNLIKELY(ent_ == NULL))    \

            return (-1);      \

          ent_->fd = slot;        \

          (ctor)(&ent_->ent.type);      \

          HT_FOI_INSERT_(map_node, map, &key_, ent_, ptr) \

        });         \

    (x) = &ent_->ent.type;          \

  } while (0)

void evmap_io_initmap_(struct event_io_map *ctx)

{

  HT_INIT(event_io_map, ctx);

}

void evmap_io_clear_(struct event_io_map *ctx)

{

  struct event_map_entry **ent, **next, *this;

  for (ent = HT_START(event_io_map, ctx); ent; ent = next) {

    this = *ent;

    next = HT_NEXT_RMV(event_io_map, ctx, ent);

    mm_free(this);

  }

  HT_CLEAR(event_io_map, ctx); /* remove all storage held by the ctx. */

}

#endif

/* Set the variable 'x' to the field in event_map 'map' with fields of type

   'struct type *' corresponding to the fd or signal 'slot'.  Set 'x' to NULL

   if there are no entries for 'slot'.  Does no bounds-checking. */

#define GET_SIGNAL_SLOT(x, map, slot, type)     \

  (x) = (struct type *)((map)->entries[slot])

/* As GET_SLOT, but construct the entry for 'slot' if it is not present,

   by allocating enough memory for a 'struct type', and initializing the new

   value by calling the function 'ctor' on it.  Makes the function

   return -1 on allocation failure.

 */

#define GET_SIGNAL_SLOT_AND_CTOR(x, map, slot, type, ctor, fdinfo_len)  \

  do {               \

    if ((map)->entries[slot] == NULL) {     \

      (map)->entries[slot] =        \

          mm_calloc(1,sizeof(struct type)+fdinfo_len); \

      if (EVUTIL_UNLIKELY((map)->entries[slot] == NULL)) \

        return (-1);       \

      (ctor)((struct type *)(map)->entries[slot]);  \

    }              \

    (x) = (struct type *)((map)->entries[slot]);    \

  } while (0)

/* If we aren't using hashtables, then define the IO_SLOT macros and functions

   as thin aliases over the SIGNAL_SLOT versions. */

#ifndef EVMAP_USE_HT

#define GET_IO_SLOT(x,map,slot,type) GET_SIGNAL_SLOT(x,map,slot,type)

#define GET_IO_SLOT_AND_CTOR(x,map,slot,type,ctor,fdinfo_len) \

  GET_SIGNAL_SLOT_AND_CTOR(x,map,slot,type,ctor,fdinfo_len)

#define FDINFO_OFFSET sizeof(struct evmap_io)

void

evmap_io_initmap_(struct event_io_map* ctx)

{

  evmap_signal_initmap_(ctx);

}

void

evmap_io_clear_(struct event_io_map* ctx)

{

  evmap_signal_clear_(ctx);

}

#endif

/** Expand 'map' with new entries of width 'msize' until it is big enough

  to store a value in 'slot'.

 */

static int

evmap_make_space(struct event_signal_map *map, int slot, int msize)

{

  if (map->nentries <= slot) {

    int nentries = map->nentries ? map->nentries : 32;

    void **tmp;

    if (slot > INT_MAX / 2)

      return (-1);

    while (nentries <= slot)

      nentries <<= 1;

    if (nentries > INT_MAX / msize)

      return (-1);

    tmp = (void **)mm_realloc(map->entries, nentries * msize);

    if (tmp == NULL)

      return (-1);

    memset(&tmp[map->nentries], 0,

        (nentries - map->nentries) * msize);

    map->nentries = nentries;

    map->entries = tmp;

  }

  return (0);

}

void

evmap_signal_initmap_(struct event_signal_map *ctx)

{

  ctx->nentries = 0;

  ctx->entries = NULL;

}

void

evmap_signal_clear_(struct event_signal_map *ctx)

{

  if (ctx->entries != NULL) {

    int i;

    for (i = 0; i < ctx->nentries; ++i) {

      if (ctx->entries[i] != NULL)

        mm_free(ctx->entries[i]);

    }

    mm_free(ctx->entries);

    ctx->entries = NULL;

  }

  ctx->nentries = 0;

}

/* code specific to file descriptors */

/** Constructor for struct evmap_io */

static void

evmap_io_init(struct evmap_io *entry)

{

  LIST_INIT(&entry->events);

  entry->nread = 0;

  entry->nwrite = 0;

  entry->nclose = 0;

}

/* return -1 on error, 0 on success if nothing changed in the event backend,

 * and 1 on success if something did. */

int

evmap_io_add_(struct event_base *base, evutil_socket_t fd, struct event *ev)

{

  const struct eventop *evsel = base->evsel;

  struct event_io_map *io = &base->io;

  struct evmap_io *ctx = NULL;

  int nread, nwrite, nclose, retval = 0;

  short res = 0, old = 0;

  struct event *old_ev;

  EVUTIL_ASSERT(fd == ev->ev_fd);

  if (fd < 0)

    return 0;

#ifndef EVMAP_USE_HT

  if (fd >= io->nentries) {

    if (evmap_make_space(io, fd, sizeof(struct evmap_io *)) == -1)

      return (-1);

  }

#endif

  GET_IO_SLOT_AND_CTOR(ctx, io, fd, evmap_io, evmap_io_init,

             evsel->fdinfo_len);

  nread = ctx->nread;

  nwrite = ctx->nwrite;

  nclose = ctx->nclose;

  if (nread)

    old |= EV_READ;

  if (nwrite)

    old |= EV_WRITE;

  if (nclose)

    old |= EV_CLOSED;

  if (ev->ev_events & EV_READ) {

    if (++nread == 1)

      res |= EV_READ;

  }

  if (ev->ev_events & EV_WRITE) {

    if (++nwrite == 1)

      res |= EV_WRITE;

  }

  if (ev->ev_events & EV_CLOSED) {

    if (++nclose == 1)

      res |= EV_CLOSED;

  }

  if (EVUTIL_UNLIKELY(nread > 0xffff || nwrite > 0xffff || nclose > 0xffff)) {

    event_warnx("Too many events reading or writing on fd %d",

        (int)fd);

    return -1;

  }

  if (EVENT_DEBUG_MODE_IS_ON() &&

      (old_ev = LIST_FIRST(&ctx->events)) &&

      (old_ev->ev_events&EV_ET) != (ev->ev_events&EV_ET)) {

    event_warnx("Tried to mix edge-triggered and non-edge-triggered"

        " events on fd %d", (int)fd);

    return -1;

  }

  if (res) {

    void *extra = ((char*)ctx) + sizeof(struct evmap_io);

    /* XXX(niels): we cannot mix edge-triggered and

     * level-triggered, we should probably assert on

     * this. */

    if (evsel->add(base, ev->ev_fd,

      old, (ev->ev_events & EV_ET) | res, extra) == -1)

      return (-1);

    retval = 1;

  }

  ctx->nread = (ev_uint16_t) nread;

  ctx->nwrite = (ev_uint16_t) nwrite;

  ctx->nclose = (ev_uint16_t) nclose;

  LIST_INSERT_HEAD(&ctx->events, ev, ev_io_next);

  return (retval);

}

/* return -1 on error, 0 on success if nothing changed in the event backend,

 * and 1 on success if something did. */

int

evmap_io_del_(struct event_base *base, evutil_socket_t fd, struct event *ev)

{

  const struct eventop *evsel = base->evsel;

  struct event_io_map *io = &base->io;

  struct evmap_io *ctx;

  int nread, nwrite, nclose, retval = 0;

  short res = 0, old = 0;

  if (fd < 0)

    return 0;

  EVUTIL_ASSERT(fd == ev->ev_fd);

#ifndef EVMAP_USE_HT

  if (fd >= io->nentries)

    return (-1);

#endif

  GET_IO_SLOT(ctx, io, fd, evmap_io);

  nread = ctx->nread;

  nwrite = ctx->nwrite;

  nclose = ctx->nclose;

  if (nread)

    old |= EV_READ;

  if (nwrite)

    old |= EV_WRITE;

  if (nclose)

    old |= EV_CLOSED;

  if (ev->ev_events & EV_READ) {

    if (--nread == 0)

      res |= EV_READ;

    EVUTIL_ASSERT(nread >= 0);

  }

  if (ev->ev_events & EV_WRITE) {

    if (--nwrite == 0)

      res |= EV_WRITE;

    EVUTIL_ASSERT(nwrite >= 0);

  }

  if (ev->ev_events & EV_CLOSED) {

    if (--nclose == 0)

      res |= EV_CLOSED;

    EVUTIL_ASSERT(nclose >= 0);

  }

  if (res) {

    void *extra = ((char*)ctx) + sizeof(struct evmap_io);

    if (evsel->del(base, ev->ev_fd,

      old, (ev->ev_events & EV_ET) | res, extra) == -1) {

      retval = -1;

    } else {

      retval = 1;

    }

  }

  ctx->nread = nread;

  ctx->nwrite = nwrite;

  ctx->nclose = nclose;

  LIST_REMOVE(ev, ev_io_next);

  return (retval);

}

void

evmap_io_active_(struct event_base *base, evutil_socket_t fd, short events)

{

  struct event_io_map *io = &base->io;

  struct evmap_io *ctx;

  struct event *ev;

#ifndef EVMAP_USE_HT

  if (fd < 0 || fd >= io->nentries)

    return;

#endif

  GET_IO_SLOT(ctx, io, fd, evmap_io);

  if (NULL == ctx)

    return;

  LIST_FOREACH(ev, &ctx->events, ev_io_next) {

    if (ev->ev_events & (events & ~EV_ET))

      event_active_nolock_(ev, ev->ev_events & events, 1);

  }

}

/* code specific to signals */

static void

evmap_signal_init(struct evmap_signal *entry)

{

  LIST_INIT(&entry->events);

}

int

evmap_signal_add_(struct event_base *base, int sig, struct event *ev)

{

  const struct eventop *evsel = base->evsigsel;

  struct event_signal_map *map = &base->sigmap;

  struct evmap_signal *ctx = NULL;

  if (sig < 0 || sig >= NSIG)

    return (-1);

  if (sig >= map->nentries) {

    if (evmap_make_space(

      map, sig, sizeof(struct evmap_signal *)) == -1)

      return (-1);

  }

  GET_SIGNAL_SLOT_AND_CTOR(ctx, map, sig, evmap_signal, evmap_signal_init,

      base->evsigsel->fdinfo_len);

  if (LIST_EMPTY(&ctx->events)) {

    if (evsel->add(base, ev->ev_fd, 0, EV_SIGNAL, NULL)

        == -1)

      return (-1);

  }

  LIST_INSERT_HEAD(&ctx->events, ev, ev_signal_next);

  return (1);

}

int

evmap_signal_del_(struct event_base *base, int sig, struct event *ev)

{

  const struct eventop *evsel = base->evsigsel;

  struct event_signal_map *map = &base->sigmap;

  struct evmap_signal *ctx;

  if (sig < 0 || sig >= map->nentries)

    return (-1);

  GET_SIGNAL_SLOT(ctx, map, sig, evmap_signal);

  LIST_REMOVE(ev, ev_signal_next);

  if (LIST_FIRST(&ctx->events) == NULL) {

    if (evsel->del(base, ev->ev_fd, 0, EV_SIGNAL, NULL) == -1)

      return (-1);

  }

  return (1);

}

void

evmap_signal_active_(struct event_base *base, evutil_socket_t sig, int ncalls)

{

  struct event_signal_map *map = &base->sigmap;

  struct evmap_signal *ctx;

  struct event *ev;

  if (sig < 0 || sig >= map->nentries)

    return;

  GET_SIGNAL_SLOT(ctx, map, sig, evmap_signal);

  if (!ctx)

    return;

  LIST_FOREACH(ev, &ctx->events, ev_signal_next)

    event_active_nolock_(ev, EV_SIGNAL, ncalls);

}

void *

evmap_io_get_fdinfo_(struct event_io_map *map, evutil_socket_t fd)

{

  struct evmap_io *ctx;

  GET_IO_SLOT(ctx, map, fd, evmap_io);

  if (ctx)

    return ((char*)ctx) + sizeof(struct evmap_io);

  else

    return NULL;

}

/* Callback type for evmap_io_foreach_fd */

typedef int (*evmap_io_foreach_fd_cb)(

  struct event_base *, evutil_socket_t, struct evmap_io *, void *);

/* Multipurpose helper function: Iterate over every file descriptor event_base

 * for which we could have EV_READ or EV_WRITE events.  For each such fd, call

 * fn(base, signum, evmap_io, arg), where fn is the user-provided

 * function, base is the event_base, signum is the signal number, evmap_io

 * is an evmap_io structure containing a list of events pending on the

 * file descriptor, and arg is the user-supplied argument.

 *

 * If fn returns 0, continue on to the next signal. Otherwise, return the same

 * value that fn returned.

 *

 * Note that there is no guarantee that the file descriptors will be processed

 * in any particular order.

 */

static int

evmap_io_foreach_fd(struct event_base *base,

    evmap_io_foreach_fd_cb fn,

    void *arg)

{

  evutil_socket_t fd;

  struct event_io_map *iomap = &base->io;

  int r = 0;

#ifdef EVMAP_USE_HT

  struct event_map_entry **mapent;

  HT_FOREACH(mapent, event_io_map, iomap) {

    struct evmap_io *ctx = &(*mapent)->ent.evmap_io;

    fd = (*mapent)->fd;

#else

  for (fd = 0; fd < iomap->nentries; ++fd) {

    struct evmap_io *ctx = iomap->entries[fd];

    if (!ctx)

      continue;

#endif

    if ((r = fn(base, fd, ctx, arg)))

      break;

  }

  return r;

}

/* Callback type for evmap_signal_foreach_signal */

typedef int (*evmap_signal_foreach_signal_cb)(

  struct event_base *, int, struct evmap_signal *, void *);

/* Multipurpose helper function: Iterate over every signal number in the

 * event_base for which we could have signal events.  For each such signal,

 * call fn(base, signum, evmap_signal, arg), where fn is the user-provided

 * function, base is the event_base, signum is the signal number, evmap_signal

 * is an evmap_signal structure containing a list of events pending on the

 * signal, and arg is the user-supplied argument.

 *

 * If fn returns 0, continue on to the next signal. Otherwise, return the same

 * value that fn returned.

 */

static int

evmap_signal_foreach_signal(struct event_base *base,

    evmap_signal_foreach_signal_cb fn,

    void *arg)

{

  struct event_signal_map *sigmap = &base->sigmap;

  int r = 0;

  int signum;

  for (signum = 0; signum < sigmap->nentries; ++signum) {

    struct evmap_signal *ctx = sigmap->entries[signum];

    if (!ctx)

      continue;

    if ((r = fn(base, signum, ctx, arg)))

      break;

  }

  return r;

}

/* Helper for evmap_reinit_: tell the backend to add every fd for which we have

 * pending events, with the appropriate combination of EV_READ, EV_WRITE, and

 * EV_ET. */

static int

evmap_io_reinit_iter_fn(struct event_base *base, evutil_socket_t fd,

    struct evmap_io *ctx, void *arg)

{

  const struct eventop *evsel = base->evsel;

  void *extra;

  int *result = arg;

  short events = 0;

  struct event *ev;

  EVUTIL_ASSERT(ctx);

  extra = ((char*)ctx) + sizeof(struct evmap_io);

  if (ctx->nread)

    events |= EV_READ;

  if (ctx->nwrite)

    events |= EV_WRITE;

  if (ctx->nclose)

    events |= EV_CLOSED;

  if (evsel->fdinfo_len)

    memset(extra, 0, evsel->fdinfo_len);

  if (events &&

      (ev = LIST_FIRST(&ctx->events)) &&

      (ev->ev_events & EV_ET))

    events |= EV_ET;

  if (evsel->add(base, fd, 0, events, extra) == -1)

    *result = -1;

  return 0;

}

/* Helper for evmap_reinit_: tell the backend to add every signal for which we

 * have pending events.  */

static int

evmap_signal_reinit_iter_fn(struct event_base *base,

    int signum, struct evmap_signal *ctx, void *arg)

{

  const struct eventop *evsel = base->evsigsel;

  int *result = arg;

  if (!LIST_EMPTY(&ctx->events)) {

    if (evsel->add(base, signum, 0, EV_SIGNAL, NULL) == -1)

      *result = -1;

  }

  return 0;

}

int

evmap_reinit_(struct event_base *base)

{

  int result = 0;

  evmap_io_foreach_fd(base, evmap_io_reinit_iter_fn, &result);

  if (result < 0)

    return -1;

  evmap_signal_foreach_signal(base, evmap_signal_reinit_iter_fn, &result);

  if (result < 0)

    return -1;

  return 0;

}

/* Helper for evmap_delete_all_: delete every event in an event_dlist. */

static int

delete_all_in_dlist(struct event_dlist *dlist)

{

  struct event *ev;

  while ((ev = LIST_FIRST(dlist)))

    event_del(ev);

  return 0;

}

/* Helper for evmap_delete_all_: delete every event pending on an fd. */

static int

evmap_io_delete_all_iter_fn(struct event_base *base, evutil_socket_t fd,

    struct evmap_io *io_info, void *arg)

{

  return delete_all_in_dlist(&io_info->events);

}

/* Helper for evmap_delete_all_: delete every event pending on a signal. */

static int

evmap_signal_delete_all_iter_fn(struct event_base *base, int signum,

    struct evmap_signal *sig_info, void *arg)

{

  return delete_all_in_dlist(&sig_info->events);

}

void

evmap_delete_all_(struct event_base *base)

{

  evmap_signal_foreach_signal(base, evmap_signal_delete_all_iter_fn, NULL);

  evmap_io_foreach_fd(base, evmap_io_delete_all_iter_fn, NULL);

}

/** Per-fd structure for use with changelists.  It keeps track, for each fd or

 * signal using the changelist, of where its entry in the changelist is.

 */

struct event_changelist_fdinfo {

  int idxplus1; /* this is the index +1, so that memset(0) will make it

           * a no-such-element */

};

void

event_changelist_init_(struct event_changelist *changelist)

{

  changelist->changes = NULL;

  changelist->changes_size = 0;

  changelist->n_changes = 0;

}

/** Helper: return the changelist_fdinfo corresponding to a given change. */

static inline struct event_changelist_fdinfo *

event_change_get_fdinfo(struct event_base *base,

    const struct event_change *change)

{

  char *ptr;

  if (change->read_change & EV_CHANGE_SIGNAL) {

    struct evmap_signal *ctx;

    GET_SIGNAL_SLOT(ctx, &base->sigmap, change->fd, evmap_signal);

    ptr = ((char*)ctx) + sizeof(struct evmap_signal);

  } else {

    struct evmap_io *ctx;

    GET_IO_SLOT(ctx, &base->io, change->fd, evmap_io);

    ptr = ((char*)ctx) + sizeof(struct evmap_io);

  }

  return (void*)ptr;

}

/** Callback helper for event_changelist_assert_ok */

static int

event_changelist_assert_ok_foreach_iter_fn(

  struct event_base *base,

  evutil_socket_t fd, struct evmap_io *io, void *arg)

{

  struct event_changelist *changelist = &base->changelist;

  struct event_changelist_fdinfo *f;

  f = (void*)

      ( ((char*)io) + sizeof(struct evmap_io) );

  if (f->idxplus1) {

    struct event_change *c = &changelist->changes[f->idxplus1 - 1];

    EVUTIL_ASSERT(c->fd == fd);

  }

  return 0;

}

/** Make sure that the changelist is consistent with the evmap structures. */

static void

event_changelist_assert_ok(struct event_base *base)

{

  int i;

  struct event_changelist *changelist = &base->changelist;

  EVUTIL_ASSERT(changelist->changes_size >= changelist->n_changes);

  for (i = 0; i < changelist->n_changes; ++i) {

    struct event_change *c = &changelist->changes[i];

    struct event_changelist_fdinfo *f;

    EVUTIL_ASSERT(c->fd >= 0);

    f = event_change_get_fdinfo(base, c);

    EVUTIL_ASSERT(f);

    EVUTIL_ASSERT(f->idxplus1 == i + 1);

  }

  evmap_io_foreach_fd(base,

      event_changelist_assert_ok_foreach_iter_fn,

      NULL);

}

#ifdef DEBUG_CHANGELIST

#define event_changelist_check(base)  event_changelist_assert_ok((base))

#else

#define event_changelist_check(base)  ((void)0)

#endif

void

event_changelist_remove_all_(struct event_changelist *changelist,

    struct event_base *base)

{

  int i;

  event_changelist_check(base);

  for (i = 0; i < changelist->n_changes; ++i) {

    struct event_change *ch = &changelist->changes[i];

    struct event_changelist_fdinfo *fdinfo =

        event_change_get_fdinfo(base, ch);

    EVUTIL_ASSERT(fdinfo->idxplus1 == i + 1);

    fdinfo->idxplus1 = 0;

  }

  changelist->n_changes = 0;

  event_changelist_check(base);

}

void

event_changelist_freemem_(struct event_changelist *changelist)

{

  if (changelist->changes)

    mm_free(changelist->changes);

  event_changelist_init_(changelist); /* zero it all out. */

}

/** Increase the size of 'changelist' to hold more changes. */

static int

event_changelist_grow(struct event_changelist *changelist)

{

  int new_size;

  struct event_change *new_changes;

  if (changelist->changes_size < 64)

    new_size = 64;

  else

    new_size = changelist->changes_size * 2;

  new_changes = mm_realloc(changelist->changes,

      new_size * sizeof(struct event_change));

  if (EVUTIL_UNLIKELY(new_changes == NULL))

    return (-1);

  changelist->changes = new_changes;

  changelist->changes_size = new_size;

  return (0);

}

/** Return a pointer to the changelist entry for the file descriptor or signal

 * 'fd', whose fdinfo is 'fdinfo'.  If none exists, construct it, setting its

 * old_events field to old_events.

 */

static struct event_change *

event_changelist_get_or_construct(struct event_changelist *changelist,

    evutil_socket_t fd,

    short old_events,

    struct event_changelist_fdinfo *fdinfo)

{

  struct event_change *change;

  if (fdinfo->idxplus1 == 0) {

    int idx;

    EVUTIL_ASSERT(changelist->n_changes <= changelist->changes_size);

    if (changelist->n_changes == changelist->changes_size) {

      if (event_changelist_grow(changelist) < 0)

        return NULL;

    }

    idx = changelist->n_changes++;

    change = &changelist->changes[idx];

    fdinfo->idxplus1 = idx + 1;

    memset(change, 0, sizeof(struct event_change));

    change->fd = fd;

    change->old_events = old_events;

  } else {

    change = &changelist->changes[fdinfo->idxplus1 - 1];

    EVUTIL_ASSERT(change->fd == fd);

  }

  return change;

}

int

event_changelist_add_(struct event_base *base, evutil_socket_t fd, short old, short events,

    void *p)

{

  struct event_changelist *changelist = &base->changelist;

  struct event_changelist_fdinfo *fdinfo = p;

  struct event_change *change;

  ev_uint8_t evchange = EV_CHANGE_ADD | (events & (EV_ET|EV_PERSIST|EV_SIGNAL));

  event_changelist_check(base);

  change = event_changelist_get_or_construct(changelist, fd, old, fdinfo);

  if (!change)

    return -1;

  /* An add replaces any previous delete, but doesn't result in a no-op,

   * since the delete might fail (because the fd had been closed since

   * the last add, for instance. */

  if (events & (EV_READ|EV_SIGNAL))

    change->read_change = evchange;

  if (events & EV_WRITE)

    change->write_change = evchange;

  if (events & EV_CLOSED)

    change->close_change = evchange;

  event_changelist_check(base);

  return (0);

}

int

event_changelist_del_(struct event_base *base, evutil_socket_t fd, short old, short events,

    void *p)

{

  struct event_changelist *changelist = &base->changelist;

  struct event_changelist_fdinfo *fdinfo = p;

  struct event_change *change;

  ev_uint8_t del = EV_CHANGE_DEL | (events & EV_ET);

  event_changelist_check(base);

  change = event_changelist_get_or_construct(changelist, fd, old, fdinfo);

  event_changelist_check(base);

  if (!change)

    return -1;

  /* A delete on an event set that doesn't contain the event to be

     deleted produces a no-op.  This effectively emoves any previous

     uncommitted add, rather than replacing it: on those platforms where

     "add, delete, dispatch" is not the same as "no-op, dispatch", we

     want the no-op behavior.

     If we have a no-op item, we could remove it it from the list

     entirely, but really there's not much point: skipping the no-op

     change when we do the dispatch later is far cheaper than rejuggling

     the array now.

     As this stands, it also lets through deletions of events that are

     not currently set.

   */

  if (events & (EV_READ|EV_SIGNAL)) {