/* GLIB - Library of useful routines for C programming

 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald

 *

 * gpoll.c: poll(2) abstraction

 * Copyright 1998 Owen Taylor

 * Copyright 2008 Red Hat, Inc.

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 */

/*

 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS

 * file for a list of people on the GLib Team.  See the ChangeLog

 * files for a list of changes.  These files are distributed with

 * GLib at ftp://ftp.gtk.org/pub/gtk/.

 */

/*

 * MT safe

 */

#include "config.h"

#include "glibconfig.h"

#include "giochannel.h"

/* Uncomment the next line (and the corresponding line in gmain.c) to

 * enable debugging printouts if the environment variable

 * G_MAIN_POLL_DEBUG is set to some value.

 */

/* #define G_MAIN_POLL_DEBUG */

#ifdef _WIN32

/* Always enable debugging printout on Windows, as it is more often

 * needed there...

 */

#define G_MAIN_POLL_DEBUG

#endif

#include <sys/types.h>

#include <time.h>

#include <stdlib.h>

#ifdef HAVE_SYS_TIME_H

#include <sys/time.h>

#endif /* HAVE_SYS_TIME_H */

#ifdef HAVE_POLL

#  include <poll.h>

/* The poll() emulation on OS/X doesn't handle fds=NULL, nfds=0,

 * so we prefer our own poll emulation.

 */

#if defined(_POLL_EMUL_H_) || defined(BROKEN_POLL)

#undef HAVE_POLL

#endif

#endif /* GLIB_HAVE_SYS_POLL_H */

#ifdef G_OS_UNIX

#include <unistd.h>

#endif /* G_OS_UNIX */

#include <errno.h>

#ifdef G_OS_WIN32

#define STRICT

#include <windows.h>

#include <process.h>

#endif /* G_OS_WIN32 */

#include "gpoll.h"

#ifdef G_OS_WIN32

#include "gprintf.h"

#endif

#ifdef G_MAIN_POLL_DEBUG

extern gboolean _g_main_poll_debug;

#endif

#ifdef HAVE_POLL

/**

 * g_poll:

 * @fds: file descriptors to poll

 * @nfds: the number of file descriptors in @fds

 * @timeout: amount of time to wait, in milliseconds, or -1 to wait forever

 *

 * Polls @fds, as with the poll() system call, but portably. (On

 * systems that don't have poll(), it is emulated using select().)

 * This is used internally by #GMainContext, but it can be called

 * directly if you need to block until a file descriptor is ready, but

 * don't want to run the full main loop.

 *

 * Each element of @fds is a #GPollFD describing a single file

 * descriptor to poll. The @fd field indicates the file descriptor,

 * and the @events field indicates the events to poll for. On return,

 * the @revents fields will be filled with the events that actually

 * occurred.

 *

 * On POSIX systems, the file descriptors in @fds can be any sort of

 * file descriptor, but the situation is much more complicated on

 * Windows. If you need to use g_poll() in code that has to run on

 * Windows, the easiest solution is to construct all of your

 * #GPollFDs with g_io_channel_win32_make_pollfd().

 *

 * Returns: the number of entries in @fds whose @revents fields

 * were filled in, or 0 if the operation timed out, or -1 on error or

 * if the call was interrupted.

 *

 * Since: 2.20

 **/

gint

g_poll (GPollFD *fds,

  guint    nfds,

  gint     timeout)

{

  return poll ((struct pollfd *)fds, nfds, timeout);

}

#else /* !HAVE_POLL */

#ifdef G_OS_WIN32

static int

poll_rest (GPollFD *msg_fd,

           GPollFD *stop_fd,

           HANDLE  *handles,

           GPollFD *handle_to_fd[],

           gint     nhandles,

           DWORD    timeout_ms)

{

  DWORD ready;

  GPollFD *f;

  int recursed_result;

  if (msg_fd != NULL)

    {

      /* Wait for either messages or handles

       * -> Use MsgWaitForMultipleObjectsEx

       */

      if (_g_main_poll_debug)

  g_print ("  MsgWaitForMultipleObjectsEx(%d, %lu)\n", nhandles, timeout_ms);

      ready = MsgWaitForMultipleObjectsEx (nhandles, handles, timeout_ms,

             QS_ALLINPUT, MWMO_ALERTABLE);

      if (ready == WAIT_FAILED)

  {

    gchar *emsg = g_win32_error_message (GetLastError ());

    g_warning ("MsgWaitForMultipleObjectsEx failed: %s", emsg);

    g_free (emsg);

  }

    }

  else if (nhandles == 0)

    {

      /* No handles to wait for, just the timeout */

      if (timeout_ms == INFINITE)

  ready = WAIT_FAILED;

      else

        {

          /* Wait for the current process to die, more efficient than SleepEx(). */

          WaitForSingleObjectEx (GetCurrentProcess (), timeout_ms, TRUE);

          ready = WAIT_TIMEOUT;

        }

    }

  else

    {

      /* Wait for just handles

       * -> Use WaitForMultipleObjectsEx

       */

      if (_g_main_poll_debug)

  g_print ("  WaitForMultipleObjectsEx(%d, %lu)\n", nhandles, timeout_ms);

      ready = WaitForMultipleObjectsEx (nhandles, handles, FALSE, timeout_ms, TRUE);

      if (ready == WAIT_FAILED)

  {

    gchar *emsg = g_win32_error_message (GetLastError ());

    g_warning ("WaitForMultipleObjectsEx failed: %s", emsg);

    g_free (emsg);

  }

    }

  if (_g_main_poll_debug)

    g_print ("  wait returns %ld%s\n",

       ready,

       (ready == WAIT_FAILED ? " (WAIT_FAILED)" :

        (ready == WAIT_TIMEOUT ? " (WAIT_TIMEOUT)" :

         (msg_fd != NULL && ready == WAIT_OBJECT_0 + nhandles ? " (msg)" : ""))));

  if (ready == WAIT_FAILED)

    return -1;

  else if (ready == WAIT_TIMEOUT ||

     ready == WAIT_IO_COMPLETION)

    return 0;

  else if (msg_fd != NULL && ready == WAIT_OBJECT_0 + nhandles)

    {

      msg_fd->revents |= G_IO_IN;

      /* If we have a timeout, or no handles to poll, be satisfied

       * with just noticing we have messages waiting.

       */

      if (timeout_ms != 0 || nhandles == 0)

  return 1;

      /* If no timeout and handles to poll, recurse to poll them,

       * too.

       */

      recursed_result = poll_rest (NULL, stop_fd, handles, handle_to_fd, nhandles, 0);

      return (recursed_result == -1) ? -1 : 1 + recursed_result;

    }

  else if (ready < WAIT_OBJECT_0 + nhandles)

    {

      int retval;

      f = handle_to_fd[ready - WAIT_OBJECT_0];

      f->revents = f->events;

      if (_g_main_poll_debug)

        g_print ("  got event %p\n", (HANDLE) f->fd);

      /* Do not count the stop_fd */

      retval = (f != stop_fd) ? 1 : 0;

      /* If no timeout and polling several handles, recurse to poll

       * the rest of them.

       */

      if (timeout_ms == 0 && nhandles > 1)

        {

          /* Poll the handles with index > ready */

          HANDLE *shorter_handles;

          GPollFD **shorter_handle_to_fd;

          gint shorter_nhandles;

          shorter_handles = &handles[ready - WAIT_OBJECT_0 + 1];

          shorter_handle_to_fd = &handle_to_fd[ready - WAIT_OBJECT_0 + 1];

          shorter_nhandles = nhandles - (ready - WAIT_OBJECT_0 + 1);

          recursed_result = poll_rest (NULL, stop_fd, shorter_handles, shorter_handle_to_fd, shorter_nhandles, 0);

          return (recursed_result == -1) ? -1 : retval + recursed_result;

        }

      return retval;

    }

  return 0;

}

typedef struct

{

  HANDLE handles[MAXIMUM_WAIT_OBJECTS];

  GPollFD *handle_to_fd[MAXIMUM_WAIT_OBJECTS];

  GPollFD *msg_fd;

  GPollFD *stop_fd;

  gint nhandles;

  DWORD    timeout_ms;

} GWin32PollThreadData;

static gint

poll_single_thread (GWin32PollThreadData *data)

{

  int retval;

  /* Polling for several things? */

  if (data->nhandles > 1 || (data->nhandles > 0 && data->msg_fd != NULL))

    {

      /* First check if one or several of them are immediately

       * available

       */

      retval = poll_rest (data->msg_fd, data->stop_fd, data->handles, data->handle_to_fd, data->nhandles, 0);

      /* If not, and we have a significant timeout, poll again with

       * timeout then. Note that this will return indication for only

       * one event, or only for messages.

       */

      if (retval == 0 && (data->timeout_ms == INFINITE || data->timeout_ms > 0))

        retval = poll_rest (data->msg_fd, data->stop_fd, data->handles, data->handle_to_fd, data->nhandles, data->timeout_ms);

    }

  else

    {

      /* Just polling for one thing, so no need to check first if

       * available immediately

       */

      retval = poll_rest (data->msg_fd, data->stop_fd, data->handles, data->handle_to_fd, data->nhandles, data->timeout_ms);

    }

  return retval;

}

static void

fill_poll_thread_data (GPollFD              *fds,

                       guint                 nfds,

                       DWORD                 timeout_ms,

                       GPollFD              *stop_fd,

                       GWin32PollThreadData *data)

{

  GPollFD *f;

  data->timeout_ms = timeout_ms;

  if (stop_fd != NULL)

    {

      if (_g_main_poll_debug)

        g_print (" Stop FD: %p", (HANDLE) stop_fd->fd);

      g_assert (data->nhandles < MAXIMUM_WAIT_OBJECTS);

      data->stop_fd = stop_fd;

      data->handle_to_fd[data->nhandles] = stop_fd;

      data->handles[data->nhandles++] = (HANDLE) stop_fd->fd;

    }

  for (f = fds; f < &fds[nfds]; ++f)

    {

      if ((data->nhandles == MAXIMUM_WAIT_OBJECTS) ||

          (data->msg_fd != NULL && (data->nhandles == MAXIMUM_WAIT_OBJECTS - 1)))

        {

          g_warning ("Too many handles to wait for!");

          break;

        }

      if (f->fd == G_WIN32_MSG_HANDLE && (f->events & G_IO_IN))

        {

          if (_g_main_poll_debug && data->msg_fd == NULL)

            g_print (" MSG");

          data->msg_fd = f;

        }

      else if (f->fd > 0)

        {

          if (_g_main_poll_debug)

            g_print (" %p", (HANDLE) f->fd);

          data->handle_to_fd[data->nhandles] = f;

          data->handles[data->nhandles++] = (HANDLE) f->fd;

        }

      f->revents = 0;

    }

}

static guint __stdcall

poll_thread_run (gpointer user_data)

{

  GWin32PollThreadData *data = user_data;

  /* Docs say that it is safer to call _endthreadex by our own:

   * https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/endthread-endthreadex

   */

  _endthreadex (poll_single_thread (data));

  g_assert_not_reached ();

  return 0;

}

/* One slot for a possible msg object or the stop event */

#define MAXIMUM_WAIT_OBJECTS_PER_THREAD (MAXIMUM_WAIT_OBJECTS - 1)

gint

g_poll (GPollFD *fds,

  guint    nfds,

  gint     timeout)

{

  guint nthreads, threads_remain;

  HANDLE thread_handles[MAXIMUM_WAIT_OBJECTS];

  GWin32PollThreadData *threads_data;

  GPollFD stop_event = { 0, };

  GPollFD *f;

  guint i, fds_idx = 0;

  DWORD ready;

  DWORD thread_retval;

  int retval;

  GPollFD *msg_fd = NULL;

  if (timeout == -1)

    timeout = INFINITE;

  /* Simple case without extra threads */

  if (nfds <= MAXIMUM_WAIT_OBJECTS)

    {

      GWin32PollThreadData data = { 0, };

      if (_g_main_poll_debug)

        g_print ("g_poll: waiting for");

      fill_poll_thread_data (fds, nfds, timeout, NULL, &data);

      if (_g_main_poll_debug)

        g_print ("\n");

      retval = poll_single_thread (&data);

      if (retval == -1)

        for (f = fds; f < &fds[nfds]; ++f)

          f->revents = 0;

      return retval;

    }

  if (_g_main_poll_debug)

    g_print ("g_poll: polling with threads\n");

  nthreads = nfds / MAXIMUM_WAIT_OBJECTS_PER_THREAD;

  threads_remain = nfds % MAXIMUM_WAIT_OBJECTS_PER_THREAD;

  if (threads_remain > 0)

    nthreads++;

  if (nthreads > MAXIMUM_WAIT_OBJECTS_PER_THREAD)

    {

      g_warning ("Too many handles to wait for in threads!");

      nthreads = MAXIMUM_WAIT_OBJECTS_PER_THREAD;

    }

#if GLIB_SIZEOF_VOID_P == 8

  stop_event.fd = (gint64)CreateEventW (NULL, TRUE, FALSE, NULL);

#else

  stop_event.fd = (gint)CreateEventW (NULL, TRUE, FALSE, NULL);

#endif

  stop_event.events = G_IO_IN;

  threads_data = g_new0 (GWin32PollThreadData, nthreads);

  for (i = 0; i < nthreads; i++)

    {

      guint thread_fds;

      guint ignore;

      if (i == (nthreads - 1) && threads_remain > 0)

        thread_fds = threads_remain;

      else

        thread_fds = MAXIMUM_WAIT_OBJECTS_PER_THREAD;

      fill_poll_thread_data (fds + fds_idx, thread_fds, timeout, &stop_event, &threads_data[i]);

      fds_idx += thread_fds;

      /* We must poll for messages from the same thread, so poll it along with the threads */

      if (threads_data[i].msg_fd != NULL)

        {

          msg_fd = threads_data[i].msg_fd;

          threads_data[i].msg_fd = NULL;

        }

      thread_handles[i] = (HANDLE) _beginthreadex (NULL, 0, poll_thread_run, &threads_data[i], 0, &ignore);

    }

  /* Wait for at least one thread to return */

  if (msg_fd != NULL)

    ready = MsgWaitForMultipleObjectsEx (nthreads, thread_handles, timeout,

                                         QS_ALLINPUT, MWMO_ALERTABLE);

  else

    ready = WaitForMultipleObjects (nthreads, thread_handles, FALSE, timeout);

  /* Signal the stop in case any of the threads did not stop yet */

  if (!SetEvent ((HANDLE)stop_event.fd))

    {

      gchar *emsg = g_win32_error_message (GetLastError ());

      g_warning ("gpoll: failed to signal the stop event: %s", emsg);

      g_free (emsg);

    }

  /* Wait for the rest of the threads to finish */

  WaitForMultipleObjects (nthreads, thread_handles, TRUE, INFINITE);

  /* The return value of all the threads give us all the fds that changed state */

  retval = 0;

  if (msg_fd != NULL && ready == WAIT_OBJECT_0 + nthreads)

    {

      msg_fd->revents |= G_IO_IN;

      retval = 1;

    }

  for (i = 0; i < nthreads; i++)

    {

      if (GetExitCodeThread (thread_handles[i], &thread_retval))

        retval = (retval == -1) ? -1 : ((thread_retval == (DWORD) -1) ? -1 : (int) (retval + thread_retval));

      CloseHandle (thread_handles[i]);

    }

  if (retval == -1)

    for (f = fds; f < &fds[nfds]; ++f)

      f->revents = 0;

  g_free (threads_data);

  CloseHandle ((HANDLE)stop_event.fd);

  return retval;

}

#else  /* !G_OS_WIN32 */

/* The following implementation of poll() comes from the GNU C Library.

 * Copyright (C) 1994, 1996, 1997 Free Software Foundation, Inc.

 */

#include <string.h> /* for bzero on BSD systems */

#ifdef HAVE_SYS_SELECT_H

#include <sys/select.h>

#endif /* HAVE_SYS_SELECT_H */

gint

g_poll (GPollFD *fds,

  guint    nfds,

  gint     timeout)

{

  struct timeval tv;

  fd_set rset, wset, xset;

  GPollFD *f;

  int ready;

  int maxfd = 0;

  FD_ZERO (&rset);

  FD_ZERO (&wset);

  FD_ZERO (&xset);

  for (f = fds; f < &fds[nfds]; ++f)

    if (f->fd >= 0)

      {

  if (f->events & G_IO_IN)

    FD_SET (f->fd, &rset);

  if (f->events & G_IO_OUT)

    FD_SET (f->fd, &wset);

  if (f->events & G_IO_PRI)

    FD_SET (f->fd, &xset);

  if (f->fd > maxfd && (f->events & (G_IO_IN|G_IO_OUT|G_IO_PRI)))

    maxfd = f->fd;

      }

  tv.tv_sec = timeout / 1000;

  tv.tv_usec = (timeout % 1000) * 1000;

  ready = select (maxfd + 1, &rset, &wset, &xset,

      timeout == -1 ? NULL : &tv);

  if (ready > 0)

    for (f = fds; f < &fds[nfds]; ++f)

      {

  f->revents = 0;

  if (f->fd >= 0)

    {

      if (FD_ISSET (f->fd, &rset))

        f->revents |= G_IO_IN;

      if (FD_ISSET (f->fd, &wset))

        f->revents |= G_IO_OUT;

      if (FD_ISSET (f->fd, &xset))

        f->revents |= G_IO_PRI;

    }

      }

  return ready;

}

#endif /* !G_OS_WIN32 */

#endif  /* !HAVE_POLL */