/* Copyright libuv project contributors. All rights reserved.

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to

 * deal in the Software without restriction, including without limitation the

 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or

 * sell copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 */

#include "uv.h"

#include "internal.h"

/* POSIX defines poll() as a portable way to wait on file descriptors.

 * Here we maintain a dynamically sized array of file descriptors and

 * events to pass as the first argument to poll().

 */

#include <assert.h>

#include <stddef.h>

#include <stdint.h>

#include <errno.h>

#include <unistd.h>

int uv__platform_loop_init(uv_loop_t* loop) {

  loop->poll_fds = NULL;

  loop->poll_fds_used = 0;

  loop->poll_fds_size = 0;

  loop->poll_fds_iterating = 0;

  return 0;

}

void uv__platform_loop_delete(uv_loop_t* loop) {

  uv__free(loop->poll_fds);

  loop->poll_fds = NULL;

}

int uv__io_fork(uv_loop_t* loop) {

  uv__platform_loop_delete(loop);

  return uv__platform_loop_init(loop);

}

/* Allocate or dynamically resize our poll fds array.  */

static void uv__pollfds_maybe_resize(uv_loop_t* loop) {

  size_t i;

  size_t n;

  struct pollfd* p;

  if (loop->poll_fds_used < loop->poll_fds_size)

    return;

  n = loop->poll_fds_size ? loop->poll_fds_size * 2 : 64;

  p = uv__reallocf(loop->poll_fds, n * sizeof(*loop->poll_fds));

  if (p == NULL)

    abort();

  loop->poll_fds = p;

  for (i = loop->poll_fds_size; i < n; i++) {

    loop->poll_fds[i].fd = -1;

    loop->poll_fds[i].events = 0;

    loop->poll_fds[i].revents = 0;

  }

  loop->poll_fds_size = n;

}

/* Primitive swap operation on poll fds array elements.  */

static void uv__pollfds_swap(uv_loop_t* loop, size_t l, size_t r) {

  struct pollfd pfd;

  pfd = loop->poll_fds[l];

  loop->poll_fds[l] = loop->poll_fds[r];

  loop->poll_fds[r] = pfd;

}

/* Add a watcher's fd to our poll fds array with its pending events.  */

static void uv__pollfds_add(uv_loop_t* loop, uv__io_t* w) {

  size_t i;

  struct pollfd* pe;

  /* If the fd is already in the set just update its events.  */

  assert(!loop->poll_fds_iterating);

  for (i = 0; i < loop->poll_fds_used; ++i) {

    if (loop->poll_fds[i].fd == w->fd) {

      loop->poll_fds[i].events = w->pevents;

      return;

    }

  }

  /* Otherwise, allocate a new slot in the set for the fd.  */

  uv__pollfds_maybe_resize(loop);

  pe = &loop->poll_fds[loop->poll_fds_used++];

  pe->fd = w->fd;

  pe->events = w->pevents;

}

/* Remove a watcher's fd from our poll fds array.  */

static void uv__pollfds_del(uv_loop_t* loop, int fd) {

  size_t i;

  assert(!loop->poll_fds_iterating);

  for (i = 0; i < loop->poll_fds_used;) {

    if (loop->poll_fds[i].fd == fd) {

      /* swap to last position and remove */

      --loop->poll_fds_used;

      uv__pollfds_swap(loop, i, loop->poll_fds_used);

      loop->poll_fds[loop->poll_fds_used].fd = -1;

      loop->poll_fds[loop->poll_fds_used].events = 0;

      loop->poll_fds[loop->poll_fds_used].revents = 0;

      /* This method is called with an fd of -1 to purge the invalidated fds,

       * so we may possibly have multiples to remove.

       */

      if (-1 != fd)

        return;

    } else {

      /* We must only increment the loop counter when the fds do not match.

       * Otherwise, when we are purging an invalidated fd, the value just

       * swapped here from the previous end of the array will be skipped.

       */

       ++i;

    }

  }

}

void uv__io_poll(uv_loop_t* loop, int timeout) {

  sigset_t* pset;

  sigset_t set;

  uint64_t time_base;

  uint64_t time_diff;

  QUEUE* q;

  uv__io_t* w;

  size_t i;

  unsigned int nevents;

  int nfds;

  int have_signals;

  struct pollfd* pe;

  int fd;

  int user_timeout;

  int reset_timeout;

  if (loop->nfds == 0) {

    assert(QUEUE_EMPTY(&loop->watcher_queue));

    return;

  }

  /* Take queued watchers and add their fds to our poll fds array.  */

  while (!QUEUE_EMPTY(&loop->watcher_queue)) {

    q = QUEUE_HEAD(&loop->watcher_queue);

    QUEUE_REMOVE(q);

    QUEUE_INIT(q);

    w = QUEUE_DATA(q, uv__io_t, watcher_queue);

    assert(w->pevents != 0);

    assert(w->fd >= 0);

    assert(w->fd < (int) loop->nwatchers);

    uv__pollfds_add(loop, w);

    w->events = w->pevents;

  }

  /* Prepare a set of signals to block around poll(), if any.  */

  pset = NULL;

  if (loop->flags & UV_LOOP_BLOCK_SIGPROF) {

    pset = &set;

    sigemptyset(pset);

    sigaddset(pset, SIGPROF);

  }

  assert(timeout >= -1);

  time_base = loop->time;

  if (uv__get_internal_fields(loop)->flags & UV_METRICS_IDLE_TIME) {

    reset_timeout = 1;

    user_timeout = timeout;

    timeout = 0;

  } else {

    reset_timeout = 0;

  }

  /* Loop calls to poll() and processing of results.  If we get some

   * results from poll() but they turn out not to be interesting to

   * our caller then we need to loop around and poll() again.

   */

  for (;;) {

    /* Only need to set the provider_entry_time if timeout != 0. The function

     * will return early if the loop isn't configured with UV_METRICS_IDLE_TIME.

     */

    if (timeout != 0)

      uv__metrics_set_provider_entry_time(loop);

    if (pset != NULL)

      if (pthread_sigmask(SIG_BLOCK, pset, NULL))

        abort();

    nfds = poll(loop->poll_fds, (nfds_t)loop->poll_fds_used, timeout);

    if (pset != NULL)

      if (pthread_sigmask(SIG_UNBLOCK, pset, NULL))

        abort();

    /* Update loop->time unconditionally. It's tempting to skip the update when

     * timeout == 0 (i.e. non-blocking poll) but there is no guarantee that the

     * operating system didn't reschedule our process while in the syscall.

     */

    SAVE_ERRNO(uv__update_time(loop));

    if (nfds == 0) {

      if (reset_timeout != 0) {

        timeout = user_timeout;

        reset_timeout = 0;

        if (timeout == -1)

          continue;

        if (timeout > 0)

          goto update_timeout;

      }

      assert(timeout != -1);

      return;

    }

    if (nfds == -1) {

      if (errno != EINTR)

        abort();

      if (reset_timeout != 0) {

        timeout = user_timeout;

        reset_timeout = 0;

      }

      if (timeout == -1)

        continue;

      if (timeout == 0)

        return;

      /* Interrupted by a signal. Update timeout and poll again. */

      goto update_timeout;

    }

    /* Tell uv__platform_invalidate_fd not to manipulate our array

     * while we are iterating over it.

     */

    loop->poll_fds_iterating = 1;

    /* Initialize a count of events that we care about.  */

    nevents = 0;

    have_signals = 0;

    /* Loop over the entire poll fds array looking for returned events.  */

    for (i = 0; i < loop->poll_fds_used; i++) {

      pe = loop->poll_fds + i;

      fd = pe->fd;

      /* Skip invalidated events, see uv__platform_invalidate_fd.  */

      if (fd == -1)

        continue;

      assert(fd >= 0);

      assert((unsigned) fd < loop->nwatchers);

      w = loop->watchers[fd];

      if (w == NULL) {

        /* File descriptor that we've stopped watching, ignore.  */

        uv__platform_invalidate_fd(loop, fd);

        continue;

      }

      /* Filter out events that user has not requested us to watch

       * (e.g. POLLNVAL).

       */

      pe->revents &= w->pevents | POLLERR | POLLHUP;

      if (pe->revents != 0) {

        /* Run signal watchers last.  */

        if (w == &loop->signal_io_watcher) {

          have_signals = 1;

        } else {

          uv__metrics_update_idle_time(loop);

          w->cb(loop, w, pe->revents);

        }

        nevents++;

      }

    }

    if (reset_timeout != 0) {

      timeout = user_timeout;

      reset_timeout = 0;

    }

    if (have_signals != 0) {

      uv__metrics_update_idle_time(loop);

      loop->signal_io_watcher.cb(loop, &loop->signal_io_watcher, POLLIN);

    }

    loop->poll_fds_iterating = 0;

    /* Purge invalidated fds from our poll fds array.  */

    uv__pollfds_del(loop, -1);

    if (have_signals != 0)

      return;  /* Event loop should cycle now so don't poll again. */

    if (nevents != 0)

      return;

    if (timeout == 0)

      return;

    if (timeout == -1)

      continue;

update_timeout:

    assert(timeout > 0);

    time_diff = loop->time - time_base;

    if (time_diff >= (uint64_t) timeout)

      return;

    timeout -= time_diff;

  }

}

/* Remove the given fd from our poll fds array because no one

 * is interested in its events anymore.

 */

void uv__platform_invalidate_fd(uv_loop_t* loop, int fd) {

  size_t i;

  assert(fd >= 0);

  if (loop->poll_fds_iterating) {

    /* uv__io_poll is currently iterating.  Just invalidate fd.  */

    for (i = 0; i < loop->poll_fds_used; i++)

      if (loop->poll_fds[i].fd == fd) {

        loop->poll_fds[i].fd = -1;

        loop->poll_fds[i].events = 0;

        loop->poll_fds[i].revents = 0;

      }

  } else {

    /* uv__io_poll is not iterating.  Delete fd from the set.  */

    uv__pollfds_del(loop, fd);

  }

}

/* Check whether the given fd is supported by poll().  */

int uv__io_check_fd(uv_loop_t* loop, int fd) {

  struct pollfd p[1];

  int rv;

  p[0].fd = fd;

  p[0].events = POLLIN;

  do

    rv = poll(p, 1, 0);

  while (rv == -1 && (errno == EINTR || errno == EAGAIN));

  if (rv == -1)

    return UV__ERR(errno);

  if (p[0].revents & POLLNVAL)

    return UV_EINVAL;

  return 0;

}