Merge from mainline.

[bpt/emacs.git] / src / w32notify.c

/* Filesystem notifications support for GNU Emacs on the Microsoft Windows API.
   Copyright (C) 2012  Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

GNU Emacs 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */

#include <stddef.h>
#include <errno.h>

/* must include CRT headers *before* config.h */
#include <config.h>

#include <windows.h>

#include "lisp.h"
#include "w32term.h"	/* for enter_crit/leave_crit and WM_EMACS_FILENOTIFY */
#include "w32heap.h"	/* for OS version data */
#include "w32.h"	/* for w32_strerror */
#include "coding.h"
#include "keyboard.h"
#include "frame.h"	/* needed by termhooks.h */
#include "termhooks.h"	/* for FILE_NOTIFY_EVENT */

struct notification {
  BYTE *buf;		/* buffer for ReadDirectoryChangesW */
  OVERLAPPED *io_info;	/* the OVERLAPPED structure for async I/O */
  BOOL subtree;		/* whether to watch subdirectories */
  DWORD filter;		/* bit mask for events to watch */
  char *watchee;	/* the file we are interested in */
  HANDLE dir;		/* handle to the watched directory */
  HANDLE thr;		/* handle to the thread that watches */
  int terminate;	/* if non-zero, request for the thread to terminate */
};

/* FIXME: this needs to be changed to support more that one request at
   a time.  */
static struct notification dirwatch;

/* Used for communicating notifications to the main thread.  */
int notification_buffer_in_use;
BYTE file_notifications[16384];
DWORD notifications_size;
HANDLE notifications_desc;

static Lisp_Object Qfile_name, Qdirectory_name, Qattributes, Qsize;
static Lisp_Object Qlast_write_time, Qlast_access_time, Qcreation_time;
static Lisp_Object Qsecurity_desc, Qsubtree, watch_list;

#if 0
/* FIXME: Debugging code, should be removed eventually.  */
const wchar_t *
format_file_action (DWORD action)
{
  static const wchar_t *action_str[] =
    { L"???", L"Added", L"Removed", L"Modified", L"Renamed from", L"Renamed to" };

  if (action >= sizeof(action_str)/sizeof(action_str[0]))
    action = 0;
  return action_str[action];
}

void
parse_notifications (BYTE *info, DWORD info_size)
{
  BYTE *p = info;
  FILE_NOTIFY_INFORMATION *fni = (PFILE_NOTIFY_INFORMATION)p;
  const DWORD min_size
    = offsetof (FILE_NOTIFY_INFORMATION, FileName) + sizeof(wchar_t);

  if (!info_size)
    {
      printf ("No info in notifications!\n");
      return;
    }

  while (info_size >= min_size)
    {
      wchar_t *fn = alloca (fni->FileNameLength + sizeof(wchar_t));
      const wchar_t *action_str;

      memcpy (fn, fni->FileName, fni->FileNameLength);
      fn[fni->FileNameLength/sizeof(wchar_t)] = 0;
      action_str = format_file_action (fni->Action);
      wprintf (L"%s: %s\n", action_str, fn);
      if (!fni->NextEntryOffset)
	break;
      p += fni->NextEntryOffset;
      fni = (PFILE_NOTIFY_INFORMATION)p;
      info_size -= fni->NextEntryOffset;
    }
}
#endif	/* debugging code */

/* Signal to the main thread that we have file notifications for it to
   process.  */
static void
send_notifications (BYTE *info, DWORD info_size, HANDLE hdir, int *terminate)
{
  int done = 0;
  FRAME_PTR f = SELECTED_FRAME ();

  /* Too bad, but PostMessage will not work in non-GUI sessions.
     FIXME.  */
  if (!FRAME_W32_P (f))
    return;

  /* A single buffer is used to communicate all notifications to the
     main thread.  Since both the main thread and several watcher
     threads could be active at the same time, we use a critical area
     and an "in-use" flag to synchronize them.  A watcher thread can
     only put its notifications in the buffer if it acquires the
     critical area and finds the "in-use" flag reset.  The main thread
     resets the flag after it is done processing notifications.

     FIXME: is there a better way of dealing with this?  */
  while (!done && !*terminate)
    {
      enter_crit ();
      if (!notification_buffer_in_use)
	{
	  if (info_size)
	    memcpy (file_notifications, info, info_size);
	  notifications_size = info_size;
	  notifications_desc = hdir;
	  /* If PostMessage fails, the message queue is full.  If that
	     happens, the last thing they will worry about is file
	     notifications.  So we effectively discard the
	     notification in that case.  */
	  if (PostMessage (FRAME_W32_WINDOW (f), WM_EMACS_FILENOTIFY, 0, 0))
	    notification_buffer_in_use = 1;
	  done = 1;
	  DebPrint (("Announced notifications of %lu bytes\n", info_size));
	}
      leave_crit ();
      if (!done)
	Sleep (5);
    }
}

/* An APC routine to cancel outstanding directory watch.  Invoked by
   the main thread via QueueUserAPC.  This is needed because only the
   thread that issued the ReadDirectoryChangesW call can call CancelIo
   to cancel that.  (CancelIoEx is only available since Vista, so we
   cannot use it on XP.)  */
VOID CALLBACK
watch_end (ULONG_PTR arg)
{
  HANDLE hdir = (HANDLE)arg;

  if (hdir && hdir != INVALID_HANDLE_VALUE)
    {
      CancelIo (hdir);
      CloseHandle (hdir);
    }
}

/* A completion routine (a.k.a. APC function) for handling events read
   by ReadDirectoryChangesW.  Called by the OS when the thread which
   issued the asynchronous ReadDirectoryChangesW call is in the
   "alertable state", i.e. waiting inside SleepEx call.  */
VOID CALLBACK
watch_completion (DWORD status, DWORD bytes_ret, OVERLAPPED *io_info)
{
  struct notification *dirwatch;

  /* Who knows what happened?  Perhaps the OVERLAPPED structure was
     freed by someone already?  In any case, we cannot do anything
     with this request, so just punt and skip it.  FIXME: should we
     raise the 'terminate' flag in this case?  */
  if (!io_info)
    return;

  /* We have a pointer to our dirwatch structure conveniently stashed
     away in the hEvent member of the OVERLAPPED struct.  According to
     MSDN documentation of ReadDirectoryChangesW: "The hEvent member
     of the OVERLAPPED structure is not used by the system, so you can
     use it yourself."  */
  dirwatch = (struct notification *)io_info->hEvent;
  if (status == ERROR_OPERATION_ABORTED)
    {
      /* We've been called because the main thread told us to issue
	 CancelIo on the directory we watch, and watch_end did so.
	 The directory handle is already closed.  We should clean up
	 and exit, signalling to the thread worker routine not to
	 issue another call to ReadDirectoryChangesW.  */
      xfree (dirwatch->buf);
      dirwatch->buf = NULL;
      xfree (dirwatch->io_info);
      dirwatch->io_info = NULL;
      xfree (dirwatch->watchee);
      dirwatch->watchee = NULL;
      dirwatch->terminate = 1;
    }
  else
    {
#if 0	/* debugging code */
      parse_notifications (dirwatch->buf, bytes_ret);
#endif
      /* Tell the main thread we have notifications for it.  */
      send_notifications (dirwatch->buf, bytes_ret, dirwatch->dir,
			  &dirwatch->terminate);
    }
}

/* Worker routine for the watch thread.  */
static DWORD WINAPI
watch_worker (LPVOID arg)
{
  struct notification *dirwatch = (struct notification *)arg;

  do {
    BOOL status;
    DWORD sleep_result;
    DWORD bytes_ret = 0;

    if (dirwatch->dir)
      {
	status = ReadDirectoryChangesW (dirwatch->dir, dirwatch->buf, 16384,
					dirwatch->subtree, dirwatch->filter,
					&bytes_ret,
					dirwatch->io_info, watch_completion);
	if (!status)
	  {
	    DebPrint (("watch_worker(1): %lu\n", GetLastError ()));
	    xfree (dirwatch->buf);
	    dirwatch->buf = NULL;
	    xfree (dirwatch->io_info);
	    dirwatch->io_info = NULL;
	    CloseHandle (dirwatch->dir);
	    dirwatch->dir = NULL;
	    xfree (dirwatch->watchee);
	    dirwatch->watchee = NULL;
	    return 1;
	  }
      }
    /* Sleep indefinitely until awoken by the I/O completion, which
       could be either a change notification or a cancellation of the
       watch.  */
    sleep_result = SleepEx (INFINITE, TRUE);
    if (dirwatch->terminate)
      DebPrint (("watch_worker: exiting by request\n"));
  } while (!dirwatch->terminate);

  DebPrint (("watch_worker(2): %lu\n", GetLastError ()));
  return 0;
}

/* Launch a thread to watch changes to FILE in a directory open on
   handle HDIR.  */
static int
start_watching (const char *file, HANDLE hdir, BOOL subdirs, DWORD flags)
{
  dirwatch.buf = xmalloc (16384);
  dirwatch.io_info = xzalloc (sizeof(OVERLAPPED));
  /* Stash a pointer to dirwatch structure for use by the completion
     routine.  According to MSDN documentation of ReadDirectoryChangesW:
     "The hEvent member of the OVERLAPPED structure is not used by the
     system, so you can use it yourself." */
  dirwatch.io_info->hEvent = &dirwatch;
  dirwatch.subtree = subdirs;
  dirwatch.filter = flags;
  dirwatch.watchee = xstrdup (file);
  dirwatch.terminate = 0;
  dirwatch.dir = hdir;

  /* See w32proc.c where it calls CreateThread for the story behind
     the 2nd and 5th argument in the call to CreateThread.  */
  dirwatch.thr = CreateThread (NULL, 64 * 1024, watch_worker,
			       (void *)&dirwatch, 0x00010000, NULL);

  if (!dirwatch.thr)
    {
      dirwatch.terminate = 1;
      xfree (dirwatch.buf);
      dirwatch.buf = NULL;
      xfree (dirwatch.io_info);
      dirwatch.io_info = NULL;
      xfree (dirwatch.watchee);
      dirwatch.watchee = NULL;
      return -1;
    }
  return 0;
}

/* Called from the main thread to start watching FILE in PARENT_DIR,
   subject to FLAGS.  If SUBDIRS is TRUE, watch the subdirectories of
   PARENT_DIR as well.  Value is the handle on which the directory is
   open.  */
static HANDLE *
add_watch (const char *parent_dir, const char *file, BOOL subdirs, DWORD flags)
{
  HANDLE hdir;

  if (!file || !*file)
    return NULL;

  hdir = CreateFile (parent_dir,
		     FILE_LIST_DIRECTORY,
		     /* FILE_SHARE_DELETE doesn't preclude other
			processes from deleting files inside
			parent_dir.  */
		     FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
		     NULL, OPEN_EXISTING,
		     FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
		     NULL);
  if (hdir == INVALID_HANDLE_VALUE)
    return NULL;

  if (start_watching (file, hdir, subdirs, flags) == 0)
    return hdir;

  CloseHandle (hdir);
  return NULL;
}

/* Stop watching a directory specified by its handle HDIR.  */
static int
remove_watch (HANDLE hdir)
{
  if (hdir == dirwatch.dir)
    {
      int i;
      BOOL status;
      DWORD exit_code, err;

      /* Only the thread that issued the outstanding I/O call can call
	 CancelIo on it.  (CancelIoEx is available only since Vista.)
	 So we need to queue an APC for the worker thread telling it
	 to terminate.  */
      if (!QueueUserAPC (watch_end, dirwatch.thr, (ULONG_PTR)dirwatch.dir))
	DebPrint (("QueueUserAPC failed (%lu)!\n", GetLastError ()));
      /* We also set the terminate flag, for when the thread is
	 waiting on the critical section that never gets acquired.
	 FIXME: is there a cleaner method?  Using SleepEx there is a
	 no-no, as that will lead to recursive APC invocations and
	 stack overflow.  */
      dirwatch.terminate = 1;
      /* Wait for the thread to exit.  FIXME: is there a better method
	 that is not overly complex?  */
      for (i = 0; i < 50; i++)
	{
	  if (!((status = GetExitCodeThread (dirwatch.thr, &exit_code))
		&& exit_code == STILL_ACTIVE))
	    break;
	  Sleep (10);
	}
      if ((status == FALSE && (err = GetLastError ()) == ERROR_INVALID_HANDLE)
	  || exit_code == STILL_ACTIVE)
	{
	  if (!(status == FALSE && err == ERROR_INVALID_HANDLE))
	    TerminateThread (dirwatch.thr, 0);
	}

      /* Clean up.  */
      if (dirwatch.thr)
	{
	  CloseHandle (dirwatch.thr);
	  dirwatch.thr = NULL;
	}
      return 0;
    }
  else if (!dirwatch.dir)
    {
      DebPrint (("Directory handle already closed!\n"));
      return 0;
    }
  else
    {
      DebPrint (("Unknown directory handle!\n"));
      return -1;
    }
}

static DWORD
filter_list_to_flags (Lisp_Object filter_list)
{
  DWORD flags = 0;

  if (NILP (filter_list))
    return flags;

  if (!NILP (Fmember (Qfile_name, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_FILE_NAME;
  if (!NILP (Fmember (Qdirectory_name, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_DIR_NAME;
  if (!NILP (Fmember (Qattributes, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_ATTRIBUTES;
  if (!NILP (Fmember (Qsize, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_SIZE;
  if (!NILP (Fmember (Qlast_write_time, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_LAST_WRITE;
  if (!NILP (Fmember (Qlast_access_time, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_LAST_ACCESS;
  if (!NILP (Fmember (Qcreation_time, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_CREATION;
  if (!NILP (Fmember (Qsecurity_desc, filter_list)))
    flags |= FILE_NOTIFY_CHANGE_SECURITY;

  return flags;
}

DEFUN ("w32notify-add-watch", Fw32notify_add_watch,
       Sw32notify_add_watch, 3, 3, 0,
       doc: /* Add a watch for filesystem events pertaining to FILE.

This arranges for filesystem events pertaining to FILE to be reported
to Emacs.  Use `w32notify-rm-watch' to cancel the watch.

Value is a descriptor for the added watch, or nil if the file
cannot be watched.

FILTER is a list of conditions for reporting an event.  It can include
the following symbols:

  'file-name'          -- report file creation, deletion, or renaming
  'directory-name'     -- report directory creation, deletion, or renaming
  'attributes'         -- report changes in attributes
  'size'               -- report changes in file-size
  'last-write-time'    -- report changes in last-write time
  'last-access-time'   -- report changes in last-access time
  'creation-time'      -- report changes in creation time
  'security-desc'      -- report changes in security descriptor

If FILE is a directory, and FILTER includes 'subtree', then all the
subdirectories will also be watched and changes in them reported.

When any event happens that satisfies the conditions specified by
FILTER, Emacs will call the CALLBACK function passing it a single
argument EVENT, which is of the form

  (DESCRIPTOR ACTION FILE)

DESCRIPTOR is the same object as the one returned by this function.
ACTION is the description of the event.  It could be any one of the
following:

  'added'        -- FILE was added
  'removed'      -- FILE was deleted
  'modified'     -- FILE's contents or its attributes were modified
  'renamed-from' -- a file was renamed whose old name was FILE
  'renamed-to'   -- a file was renamed and its new name is FILE

FILE is the name of the file whose event is being reported.  */)
  (Lisp_Object file, Lisp_Object filter, Lisp_Object callback)
{
  Lisp_Object encoded_file, watch_object, watch_descriptor;
  char parent_dir[MAX_PATH], *basename;
  size_t fn_len;
  HANDLE hdir;
  DWORD flags;
  BOOL subdirs = FALSE;
  Lisp_Object lisp_errstr;
  char *errstr;

  CHECK_LIST (filter);

  /* The underlying features are available only since XP.  */
  if (os_subtype == OS_9X
      || (w32_major_version == 5 && w32_major_version < 1))
    {
      errno = ENOSYS;
      report_file_error ("Watching filesystem events is not supported",
			 Qnil);
    }

  /* We needa full absolute file name of FILE, and we need to remove
     any trailing slashes from it, so that GetFullPathName below gets
     the basename part correctly.  */
  file = Fdirectory_file_name (Fexpand_file_name (file, Qnil));
  encoded_file = ENCODE_FILE (file);

  fn_len = GetFullPathName (SDATA (encoded_file), MAX_PATH, parent_dir,
			    &basename);
  if (!fn_len)
    {
      errstr = w32_strerror (0);
      errno = EINVAL;
      if (!NILP (Vlocale_coding_system))
	lisp_errstr
	  = code_convert_string_norecord (build_unibyte_string (errstr),
					  Vlocale_coding_system, 0);
      else
	lisp_errstr = build_string (errstr);
      report_file_error ("GetFullPathName failed",
			 Fcons (lisp_errstr, Fcons (file, Qnil)));
    }
  /* We need the parent directory without the slash that follows it.
     If BASENAME is NULL, the argument was the root directory on its
     drive.  */
  if (basename)
    basename[-1] = '\0';
  else
    subdirs = TRUE;

  if (!NILP (Fmember (Qsubtree, filter)))
    subdirs = TRUE;

  flags = filter_list_to_flags (filter);

  hdir = add_watch (parent_dir, basename, subdirs, flags);
  if (!hdir)
    {
      DWORD err = GetLastError ();

      errno = EINVAL;
      if (err)
	{
	  errstr = w32_strerror (err);
	  if (!NILP (Vlocale_coding_system))
	    lisp_errstr
	      = code_convert_string_norecord (build_unibyte_string (errstr),
					      Vlocale_coding_system, 0);
	  else
	    lisp_errstr = build_string (errstr);
	  report_file_error ("Cannot watch file",
			     Fcons (lisp_errstr, Fcons (file, Qnil)));
	}
      else
	report_file_error ("Cannot watch file", Fcons (file, Qnil));
    }
  /* Store watch object in watch list. */
  watch_descriptor = make_number (hdir);
  watch_object = Fcons (watch_descriptor, callback);
  watch_list = Fcons (watch_object, watch_list);

  return watch_descriptor;
}

DEFUN ("w32notify-rm-watch", Fw32notify_rm_watch,
       Sw32notify_rm_watch, 1, 1, 0,
       doc: /* Remove an existing watch specified by its WATCH-DESCRIPTOR.

WATCH-DESCRIPTOR should be an object returned by `w32notify-add-watch'.  */)
     (Lisp_Object watch_descriptor)
{
  Lisp_Object watch_object;
  HANDLE hdir = (HANDLE)XINT (watch_descriptor);

  if (remove_watch (hdir) == -1)
    report_file_error ("Could not remove watch", Fcons (watch_descriptor,
							Qnil));

  /* Remove watch descriptor from watch list. */
  watch_object = Fassoc (watch_descriptor, watch_list);
  if (!NILP (watch_object))
    watch_list = Fdelete (watch_object, watch_list);

  return Qnil;
}

Lisp_Object
get_watch_object (Lisp_Object desc)
{
  return Fassoc (desc, watch_list);
}

void
syms_of_w32notify (void)
{
  DEFSYM (Qfile_name, "file-name");
  DEFSYM (Qdirectory_name, "directory-name");
  DEFSYM (Qattributes, "attributes");
  DEFSYM (Qsize, "size");
  DEFSYM (Qlast_write_time, "last-write-time");
  DEFSYM (Qlast_access_time, "last-access-time");
  DEFSYM (Qcreation_time, "creation-time");
  DEFSYM (Qsecurity_desc, "security-desc");
  DEFSYM (Qsubtree, "subtree");

  defsubr (&Sw32notify_add_watch);
  defsubr (&Sw32notify_rm_watch);

  staticpro (&watch_list);

  Fprovide (intern_c_string ("w32notify"), Qnil);
}