lib/poll.c

/* Emulation for poll(2)
   Contributed by Paolo Bonzini.

   Copyright 2001-2003, 2006-2026 Free Software Foundation, Inc.

   This file is part of gnulib.

   This file 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 file 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 program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>
#include <alloca.h>

#include <sys/types.h>

/* Specification.  */
#include <poll.h>

#include <errno.h>
#include <limits.h>

#if defined _WIN32 && ! defined __CYGWIN__
# define WINDOWS_NATIVE
# include <winsock2.h>
# include <windows.h>
# include <io.h>
# include <stdio.h>
# include <conio.h>
# if GNULIB_MSVC_NOTHROW
#  include "msvc-nothrow.h"
# else
#  include <io.h>
# endif
#else
# include <sys/time.h>
# include <unistd.h>
#endif

#include <sys/select.h>
#include <sys/socket.h>

#ifdef HAVE_SYS_IOCTL_H
# include <sys/ioctl.h>
#endif
#ifdef HAVE_SYS_FILIO_H
# include <sys/filio.h>
#endif

#include <time.h>

#include "assure.h"

#ifndef INFTIM
# define INFTIM (-1)
#endif

/* BeOS does not have MSG_PEEK.  */
#ifndef MSG_PEEK
# define MSG_PEEK 0
#endif

#ifdef WINDOWS_NATIVE

/* Don't assume that UNICODE is not defined.  */
# undef GetModuleHandle
# define GetModuleHandle GetModuleHandleA
# undef PeekConsoleInput
# define PeekConsoleInput PeekConsoleInputA
# undef CreateEvent
# define CreateEvent CreateEventA
# undef PeekMessage
# define PeekMessage PeekMessageA
# undef DispatchMessage
# define DispatchMessage DispatchMessageA

/* Do *not* use the function WSAPoll
   <https://docs.microsoft.com/en-us/windows/desktop/api/winsock2/nf-winsock2-wsapoll>
   because there is a bug named “Windows 8 Bugs 309411 - WSAPoll does not
   report failed connections” that Microsoft won't fix.
   See Daniel Stenberg: "WASPoll is broken"
   <https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/>.  */

/* Here we need the recv() function from Windows, that takes a SOCKET as
   first argument, not any possible gnulib override.  */
# undef recv

/* Here we need the select() function from Windows, because we pass bit masks
   of SOCKETs, not bit masks of FDs.  */
# undef select

/* Here we need timeval from Windows since this is what the select() function
   from Windows requires.  */
# undef timeval

/* Avoid warnings from gcc -Wcast-function-type.  */
# define GetProcAddress \
   (void *) GetProcAddress

static BOOL IsConsoleHandle (HANDLE h)
{
  DWORD mode;
  return GetConsoleMode (h, &mode) != 0;
}

static BOOL
IsSocketHandle (HANDLE h)
{
  if (IsConsoleHandle (h))
    return FALSE;

  /* Under Wine, it seems that getsockopt returns 0 for pipes too.
     WSAEnumNetworkEvents instead distinguishes the two correctly.  */
  WSANETWORKEVENTS ev;
  ev.lNetworkEvents = 0xDEADBEEF;
  WSAEnumNetworkEvents ((SOCKET) h, NULL, &ev);
  return ev.lNetworkEvents != 0xDEADBEEF;
}

/* Declare data structures for ntdll functions.  */
typedef struct _FILE_PIPE_LOCAL_INFORMATION {
  ULONG NamedPipeType;
  ULONG NamedPipeConfiguration;
  ULONG MaximumInstances;
  ULONG CurrentInstances;
  ULONG InboundQuota;
  ULONG ReadDataAvailable;
  ULONG OutboundQuota;
  ULONG WriteQuotaAvailable;
  ULONG NamedPipeState;
  ULONG NamedPipeEnd;
} FILE_PIPE_LOCAL_INFORMATION, *PFILE_PIPE_LOCAL_INFORMATION;

typedef struct _IO_STATUS_BLOCK
{
  union {
    DWORD Status;
    PVOID Pointer;
  } u;
  ULONG_PTR Information;
} IO_STATUS_BLOCK, *PIO_STATUS_BLOCK;

typedef enum _FILE_INFORMATION_CLASS {
  FilePipeLocalInformation = 24
} FILE_INFORMATION_CLASS, *PFILE_INFORMATION_CLASS;

typedef DWORD (WINAPI *PNtQueryInformationFile)
         (HANDLE, IO_STATUS_BLOCK *, VOID *, ULONG, FILE_INFORMATION_CLASS);

# ifndef PIPE_BUF
#  define PIPE_BUF      512
# endif

/* Compute revents values for file handle H.  If some events cannot happen
   for the handle, eliminate them from *P_SOUGHT.  */

static int
windows_compute_revents (HANDLE h, int *p_sought)
{
  static PNtQueryInformationFile NtQueryInformationFile;
  static BOOL once_only;

  switch (GetFileType (h))
    {
    case FILE_TYPE_PIPE:
      if (!once_only)
        {
          NtQueryInformationFile = (PNtQueryInformationFile)
            GetProcAddress (GetModuleHandle ("ntdll.dll"),
                            "NtQueryInformationFile");
          once_only = TRUE;
        }

      {
        int happened = 0;
        DWORD avail;
        if (PeekNamedPipe (h, NULL, 0, NULL, &avail, NULL) != 0)
          {
            if (avail)
              happened |= *p_sought & (POLLIN | POLLRDNORM);
          }
        else if (GetLastError () == ERROR_BROKEN_PIPE)
          happened |= POLLHUP;
        else
          {
            /* It was the write-end of the pipe.  Check if it is writable.
               If NtQueryInformationFile fails, optimistically assume the pipe is
               writable.  This could happen on Windows 9x, where
               NtQueryInformationFile is not available, or if we inherit a pipe
               that doesn't permit FILE_READ_ATTRIBUTES access on the write end
               (I think this should not happen since Windows XP SP2; WINE seems
               fine too).  Otherwise, ensure that enough space is available for
               atomic writes.  */
            IO_STATUS_BLOCK iosb;
            memset (&iosb, 0, sizeof (iosb));
            FILE_PIPE_LOCAL_INFORMATION fpli;
            memset (&fpli, 0, sizeof (fpli));

            if (!NtQueryInformationFile
                || NtQueryInformationFile (h, &iosb, &fpli, sizeof (fpli),
                                           FilePipeLocalInformation)
                || fpli.WriteQuotaAvailable >= PIPE_BUF
                || (fpli.OutboundQuota < PIPE_BUF &&
                    fpli.WriteQuotaAvailable == fpli.OutboundQuota))
              happened |= *p_sought & (POLLOUT | POLLWRNORM | POLLWRBAND);
          }
        return happened;
      }

    case FILE_TYPE_CHAR:
      {
        int ret = WaitForSingleObject (h, 0);
        if (!IsConsoleHandle (h))
          return ret == WAIT_OBJECT_0 ? *p_sought & ~(POLLPRI | POLLRDBAND) : 0;
      }

      DWORD nbuffer = 0;
      if (GetNumberOfConsoleInputEvents (h, &nbuffer))
        {
          /* Input buffer.  */
          *p_sought &= POLLIN | POLLRDNORM;
          if (nbuffer == 0)
            return POLLHUP;
          if (!*p_sought)
            return 0;

          INPUT_RECORD *irbuffer =
            (INPUT_RECORD *) alloca (nbuffer * sizeof (INPUT_RECORD));
          DWORD avail = 0;
          if (! PeekConsoleInput (h, irbuffer, nbuffer, &avail) || avail == 0)
            return POLLHUP;

          for (int i = 0; i < avail; i++)
            if (irbuffer[i].EventType == KEY_EVENT)
              return *p_sought;
          return 0;
        }
      else
        {
          /* Screen buffer.  */
          *p_sought &= POLLOUT | POLLWRNORM | POLLWRBAND;
          return *p_sought;
        }

    default:
      {
        int ret = WaitForSingleObject (h, 0);
        if (ret == WAIT_OBJECT_0)
          return *p_sought & ~(POLLPRI | POLLRDBAND);
      }

      return *p_sought & (POLLOUT | POLLWRNORM | POLLWRBAND);
    }
}

/* Convert fd_sets returned by select into revents values.  */

static int
windows_compute_revents_socket (SOCKET h, int sought, long lNetworkEvents)
{
  int happened = 0;

  if ((lNetworkEvents & (FD_READ | FD_ACCEPT | FD_CLOSE)) == FD_ACCEPT)
    happened |= (POLLIN | POLLRDNORM) & sought;
  else if (lNetworkEvents & (FD_READ | FD_ACCEPT | FD_CLOSE))
    {
      char data[64];
      WSASetLastError (0);
      int r = recv (h, data, sizeof (data), MSG_PEEK);
      int error = WSAGetLastError ();
      WSASetLastError (0);

      happened |= (POLLIN | POLLRDNORM) & sought;

      if (r > 0 || error == WSAENOTCONN)
        {
          /* Do nothing */
        }
      /* Distinguish hung-up sockets from other errors.  */
      else if (r == 0 || error == WSAESHUTDOWN || error == WSAECONNRESET
               || error == WSAECONNABORTED || error == WSAENETRESET)
        happened |= POLLHUP;
      else
        happened |= POLLERR;
    }

  if (lNetworkEvents & (FD_WRITE | FD_CONNECT))
    happened |= (POLLOUT | POLLWRNORM | POLLWRBAND) & sought;

  if (lNetworkEvents & FD_OOB)
    happened |= (POLLPRI | POLLRDBAND) & sought;

  return happened;
}

#else /* !WINDOWS_NATIVE */

/* Convert select(2) returned fd_sets into poll(2) revents values.  */
static int
compute_revents (int fd, int sought, fd_set *rfds, fd_set *wfds, fd_set *efds)
{
  int happened = 0;
  if (FD_ISSET (fd, rfds))
    {
      int r;
      int socket_errno;

# if defined __MACH__ && defined __APPLE__
      /* There is a bug in Mac OS X that causes it to ignore MSG_PEEK
         for some kinds of descriptors.  Detect if this descriptor is a
         connected socket, a server socket, or something else using a
         0-byte recv, and use ioctl(2) to detect POLLHUP.  */
      r = recv (fd, NULL, 0, MSG_PEEK);
      socket_errno = (r < 0) ? errno : 0;
      if (r == 0 || socket_errno == ENOTSOCK)
        ioctl (fd, FIONREAD, &r);
# else
      char data[64];
      r = recv (fd, data, sizeof (data), MSG_PEEK);
      socket_errno = (r < 0) ? errno : 0;
# endif

      happened |= (POLLIN | POLLRDNORM) & sought;

      if (r == 0)
        happened |= POLLHUP;

      /* If the event happened on an unconnected server socket,
         that's fine. */
      else if (r > 0 || ( /* (r == -1) && */ socket_errno == ENOTCONN))
        {
          /* Do nothing */
        }

      /* Distinguish hung-up sockets from other errors.  */
      else if (socket_errno == ESHUTDOWN || socket_errno == ECONNRESET
               || socket_errno == ECONNABORTED || socket_errno == ENETRESET)
        happened |= POLLHUP;

      /* some systems can't use recv() on non-socket, including HP NonStop */
      else if (socket_errno == ENOTSOCK)
        happened |= (POLLIN | POLLRDNORM) & sought;

      else
        happened |= POLLERR;
    }

  if (FD_ISSET (fd, wfds))
    happened |= (POLLOUT | POLLWRNORM | POLLWRBAND) & sought;

  if (FD_ISSET (fd, efds))
    happened |= (POLLPRI | POLLRDBAND) & sought;

  return happened;
}
#endif /* !WINDOWS_NATIVE */

int
poll (struct pollfd *pfd, nfds_t nfd, int timeout)
{
#ifndef WINDOWS_NATIVE
  if (nfd > INT_MAX)
    {
      errno = EINVAL;
      return -1;
    }
  /* Don't check directly for NFD greater than OPEN_MAX.  Any practical use
     of a too-large NFD is caught by one of the other checks below, and
     checking directly for getdtablesize is too much of a portability
     and/or performance and/or correctness hassle.  */

  /* EFAULT is not necessary to implement, but let's do it in the
     simplest case. */
  if (!pfd && nfd)
    {
      errno = EFAULT;
      return -1;
    }

  /* convert timeout number into a timeval structure */
  struct timeval tv;
  struct timeval *ptv;
  if (timeout == 0)
    {
      ptv = &tv;
      tv = (struct timeval) {0};
    }
  else if (timeout > 0)
    {
      ptv = &tv;
      tv = (struct timeval) {
        .tv_sec = timeout / 1000,
        .tv_usec = (timeout % 1000) * 1000
      };
    }
  else if (timeout == INFTIM)
    /* wait forever */
    ptv = NULL;
  else
    {
      errno = EINVAL;
      return -1;
    }

  /* create fd sets and determine max fd */
  int maxfd = -1;
  fd_set rfds;
  FD_ZERO (&rfds);
  fd_set wfds;
  FD_ZERO (&wfds);
  fd_set efds;
  FD_ZERO (&efds);
  for (int i = 0; i < nfd; i++)
    {
      if (pfd[i].fd >= 0)
        {
          if (maxfd < pfd[i].fd)
            {
              maxfd = pfd[i].fd;
              if (FD_SETSIZE <= maxfd)
                {
                  errno = EINVAL;
                  return -1;
                }
            }
          if (pfd[i].events & (POLLIN | POLLRDNORM))
            FD_SET (pfd[i].fd, &rfds);
          /* see select(2): "the only exceptional condition detectable
             is out-of-band data received on a socket", hence we push
             POLLWRBAND events onto wfds instead of efds. */
          if (pfd[i].events & (POLLOUT | POLLWRNORM | POLLWRBAND))
            FD_SET (pfd[i].fd, &wfds);
          if (pfd[i].events & (POLLPRI | POLLRDBAND))
            FD_SET (pfd[i].fd, &efds);
        }
    }

  /* examine fd sets */
  {
    int rc = select (maxfd + 1, &rfds, &wfds, &efds, ptv);
    if (rc < 0)
      return rc;
  }

  /* establish results */
  int rc = 0;
  for (int i = 0; i < nfd; i++)
    {
      pfd[i].revents = (pfd[i].fd < 0
                        ? 0
                        : compute_revents (pfd[i].fd, pfd[i].events,
                                           &rfds, &wfds, &efds));
      rc += pfd[i].revents != 0;
    }

  return rc;
#else
  static struct timeval tv0;
  static HANDLE hEvent;

  if (nfd > INT_MAX || timeout < -1)
    {
      errno = EINVAL;
      return -1;
    }

  if (!hEvent)
    hEvent = CreateEvent (NULL, FALSE, FALSE, NULL);

  HANDLE handle_array[FD_SETSIZE + 2];

restart:
  handle_array[0] = hEvent;
  DWORD nhandles = 1;
  fd_set rfds;
  FD_ZERO (&rfds);
  fd_set wfds;
  FD_ZERO (&wfds);
  fd_set xfds;
  FD_ZERO (&xfds);

  /* Classify socket handles and create fd sets. */
  for (nfds_t i = 0; i < nfd; i++)
    {
      int sought = pfd[i].events;
      pfd[i].revents = 0;
      if (pfd[i].fd >= 0
          && (sought & (POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM | POLLWRBAND
                        | POLLPRI | POLLRDBAND)))
        {
          HANDLE h = (HANDLE) _get_osfhandle (pfd[i].fd);
          assure (h != NULL);
          if (IsSocketHandle (h))
            {
              int requested = FD_CLOSE;

              /* see above; socket handles are mapped onto select.  */
              if (sought & (POLLIN | POLLRDNORM))
                {
                  requested |= FD_READ | FD_ACCEPT;
                  FD_SET ((SOCKET) h, &rfds);
                }
              if (sought & (POLLOUT | POLLWRNORM | POLLWRBAND))
                {
                  requested |= FD_WRITE | FD_CONNECT;
                  FD_SET ((SOCKET) h, &wfds);
                }
              if (sought & (POLLPRI | POLLRDBAND))
                {
                  requested |= FD_OOB;
                  FD_SET ((SOCKET) h, &xfds);
                }

              if (requested)
                WSAEventSelect ((SOCKET) h, hEvent, requested);
            }
          else
            {
              /* Poll now.  If we get an event, do not poll again.  Also,
                 screen buffer handles are waitable, and they'll block until
                 a character is available.  windows_compute_revents eliminates
                 bits for the "wrong" direction. */
              pfd[i].revents = windows_compute_revents (h, &sought);
              if (sought)
                handle_array[nhandles++] = h;
              if (pfd[i].revents)
                timeout = 0;
            }
        }
    }

  BOOL poll_again;
  DWORD wait_timeout;
  if (select (0, &rfds, &wfds, &xfds, &tv0) > 0)
    {
      /* Do MsgWaitForMultipleObjects anyway to dispatch messages, but
         no need to call select again.  */
      poll_again = FALSE;
      wait_timeout = 0;
    }
  else
    {
      poll_again = TRUE;
      if (timeout == INFTIM)
        wait_timeout = INFINITE;
      else
        wait_timeout = timeout;
    }

  for (;;)
    {
      DWORD ret = MsgWaitForMultipleObjects (nhandles, handle_array, FALSE,
                                             wait_timeout, QS_ALLINPUT);

      if (ret == WAIT_OBJECT_0 + nhandles)
        {
          /* new input of some other kind */
          MSG msg;
          while (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE) != 0)
            {
              TranslateMessage (&msg);
              DispatchMessage (&msg);
            }
        }
      else
        break;
    }

  if (poll_again)
    select (0, &rfds, &wfds, &xfds, &tv0);

  int rc = 0;

  /* Place a sentinel at the end of the array.  */
  handle_array[nhandles] = NULL;
  nhandles = 1;
  for (nfds_t i = 0; i < nfd; i++)
    {
      int happened;

      if (pfd[i].fd >= 0
          && (pfd[i].events & (POLLIN | POLLRDNORM |
                               POLLOUT | POLLWRNORM | POLLWRBAND)))
        {
          HANDLE h = (HANDLE) _get_osfhandle (pfd[i].fd);
          if (h != handle_array[nhandles])
            {
              /* It's a socket.  */
              WSANETWORKEVENTS ev;
              WSAEnumNetworkEvents ((SOCKET) h, NULL, &ev);
              WSAEventSelect ((SOCKET) h, 0, 0);

              /* If we're lucky, WSAEnumNetworkEvents already provided a way
                 to distinguish FD_READ and FD_ACCEPT; this saves a recv later.  */
              if (FD_ISSET ((SOCKET) h, &rfds)
                  && !(ev.lNetworkEvents & (FD_READ | FD_ACCEPT)))
                ev.lNetworkEvents |= FD_READ | FD_ACCEPT;
              if (FD_ISSET ((SOCKET) h, &wfds))
                ev.lNetworkEvents |= FD_WRITE | FD_CONNECT;
              if (FD_ISSET ((SOCKET) h, &xfds))
                ev.lNetworkEvents |= FD_OOB;

              happened = windows_compute_revents_socket ((SOCKET) h, pfd[i].events,
                                                         ev.lNetworkEvents);
            }
          else
            {
              /* Not a socket.  */
              int sought = pfd[i].events;
              happened = windows_compute_revents (h, &sought);
              nhandles++;
            }

          if ((pfd[i].revents |= happened) != 0)
            rc++;
        }
    }

  if (!rc && timeout == INFTIM)
    {
      SleepEx (1, TRUE);
      goto restart;
    }

  return rc;
#endif
}