Submitted By: Jim Gifford (jim at linuxfromscratch dot org)
Date: 2004-03-15
Initial Package Version: Jim Gifford
Origin: Debian Maintainer of FAM
Description: Dnotify Patch for FAM 2.7.0
 
diff -Naur fam-2.7.0.orig/config.h.in fam-2.7.0/config.h.in
--- fam-2.7.0.orig/config.h.in	2003-01-20 00:40:15.000000000 +0000
+++ fam-2.7.0/config.h.in	2004-03-15 21:31:34.553059530 +0000
@@ -180,3 +180,6 @@
 
 /* Define to `int' if <sys/types.h> doesn't define. */
 #undef uid_t
+
+/* Define to 1 if you have F_NOTIFY fcntl */
+#undef USE_DNOTIFY
diff -Naur fam-2.7.0.orig/configure.ac fam-2.7.0/configure.ac
--- fam-2.7.0.orig/configure.ac	2003-11-26 19:47:59.000000000 +0000
+++ fam-2.7.0/configure.ac	2004-03-15 21:31:34.556058981 +0000
@@ -33,7 +33,26 @@
 AC_HEADER_DIRENT
 AC_CHECK_HEADERS([fcntl.h limits.h linux/imon.h netinet/in.h rpc/rpc.h rpcsvc/mount.h stddef.h stdlib.h string.h syslog.h sys/imon.h sys/param.h sys/select.h sys/statvfs.h sys/syssgi.h sys/time.h sys/types.h sys/un.h unistd.h])
 
-if test "$have_sys_imon_h"; then
+# Test for the linux dnotify fcntl
+AC_MSG_CHECKING([for dnotify fcntl support])
+AC_TRY_COMPILE([
+#define _GNU_SOURCE  
+#include <fcntl.h>
+#include <unistd.h>
+],
+[ int fd = 1;
+  fcntl (fd, F_NOTIFY, (DN_MODIFY|DN_CREATE|DN_DELETE|DN_RENAME|DN_ATTRIB)
+                       |DN_MULTISHOT);
+], have_dnotify=yes, have_dnotify=no)
+
+use_dnotify=false
+AC_MSG_RESULT($have_dnotify)
+
+if test "$have_dnotify"; then
+        MONITOR_FUNCS=IMonNone
+        AC_DEFINE([USE_DNOTIFY], [], [Use dnotify])
+	use_dnotify=true
+elif test "$have_sys_imon_h"; then
 	MONITOR_FUNCS=IMonIRIX
 elif test "$have_linux_imon_h"; then
 	MONITOR_FUNCS=IMonLinux
@@ -41,6 +60,7 @@
 	MONITOR_FUNCS=IMonNone
 fi
 AC_SUBST(MONITOR_FUNCS)
+AM_CONDITIONAL(USE_DNOTIFY, $use_dnotify)
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_HEADER_STDBOOL
diff -Naur fam-2.7.0.orig/src/DNotify.c++ fam-2.7.0/src/DNotify.c++
--- fam-2.7.0.orig/src/DNotify.c++	1970-01-01 00:00:00.000000000 +0000
+++ fam-2.7.0/src/DNotify.c++	2004-03-15 21:31:34.542061543 +0000
@@ -0,0 +1,582 @@
+//  Copyright (C) 2001 Red Hat, Inc.  All Rights Reserved.
+//  Copyright (C) 1999 Silicon Graphics, Inc.  All Rights Reserved.
+//  
+//  This program is free software; you can redistribute it and/or modify it
+//  under the terms of version 2 of the GNU General Public License as
+//  published by the Free Software Foundation.
+//
+//  This program is distributed in the hope that it would be useful, but
+//  WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  Further, any
+//  license provided herein, whether implied or otherwise, is limited to
+//  this program in accordance with the express provisions of the GNU
+//  General Public License.  Patent licenses, if any, provided herein do not
+//  apply to combinations of this program with other product or programs, or
+//  any other product whatsoever.  This program is distributed without any
+//  warranty that the program is delivered free of the rightful claim of any
+//  third person by way of infringement or the like.  See the GNU General
+//  Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License along
+//  with this program; if not, write the Free Software Foundation, Inc., 59
+//  Temple Place - Suite 330, Boston MA 02111-1307, USA.
+
+#define _GNU_SOURCE  
+#include <fcntl.h>
+
+#include <string.h>
+#include <signal.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <libgen.h>
+
+#include "DNotify.h"
+
+#include "Interest.h"
+#include "Log.h"
+#include "Scheduler.h"
+#include <memory>
+
+
+int DNotify::pipe_write_fd = -2;
+int DNotify::pipe_read_fd = -2;
+volatile sig_atomic_t DNotify::queue_overflowed = 0;
+volatile sig_atomic_t DNotify::queue_changed = 0;
+int DNotify::change_queue[QUEUESIZE];
+volatile int DNotify::queue_head = 0; // Only modified by read handler
+volatile int DNotify::queue_tail = 0; // Only modified by signal handler
+DNotify::EventHandler DNotify::ehandler;
+
+DNotify::DirWatch *DNotify::dir_hash[DIR_HASHSIZE];
+DNotify::FileWatch *DNotify::file_hash[FILE_HASHSIZE];
+
+struct DNotify::FileWatch
+{
+    DirWatch *dir_watch;
+    dev_t file_dev;
+    ino_t file_ino;
+    FileWatch *next; // The DirWatch.watches list
+    FileWatch *hash_link;
+};
+
+struct DNotify::DirWatch
+{
+    int fd;
+    dev_t dir_dev;
+    ino_t dir_ino;
+    
+    DirWatch *hash_link;
+    FileWatch *watches;
+};
+
+struct DNotify::ChangeEventData
+{
+    dev_t file_dev;
+    ino_t file_ino;
+};    
+
+DNotify::DNotify(EventHandler h)
+{
+    assert(ehandler == NULL);
+    ehandler = h;
+}
+
+DNotify::~DNotify()
+{
+    if (pipe_read_fd >= 0)
+    {
+	//  Tell the scheduler.
+
+	(void) Scheduler::remove_read_handler(pipe_read_fd);
+
+	//  Close the pipe.
+
+	if (close(pipe_read_fd) < 0)
+	    Log::perror("can't pipe read end");
+	else
+	    Log::debug("closed pipe read end");
+	
+	if (close(pipe_write_fd) < 0)
+	    Log::perror("can't pipe write end");
+	else
+	    Log::debug("closed pipe write end");
+	pipe_read_fd = -1;
+    }
+    ehandler = NULL;
+}
+
+void
+DNotify::overflow_signal_handler(int sig, siginfo_t *si, void *data)
+{
+  char c = 'x';
+
+  {
+    char *str = "*************** overflow sigqueue ***********************\n";
+    write (STDERR_FILENO, str, strlen(str));
+  }
+
+  if (!queue_overflowed)
+  {
+      queue_overflowed = 1;
+      // Trigger the read handler
+      write(pipe_write_fd, &c, 1);
+  }
+}
+
+void
+DNotify::signal_handler(int sig, siginfo_t *si, void *data)
+{
+  int left;
+  char c = 'x';
+
+  if (queue_head <= queue_tail)
+    left = (QUEUESIZE + queue_head) - queue_tail;
+  else 
+    left = queue_head - queue_tail;
+  
+  // Must leave at least one item unused to see difference
+  // Betweeen empty and full
+  if (left <= 1)
+  {
+      queue_overflowed = 1;
+      {
+	char *str = "*************** overflow famqueue ****************\n";
+	write (STDERR_FILENO, str, strlen(str));
+      }
+  }
+  else
+  {
+      change_queue[queue_tail] = si->si_fd;
+      queue_tail = (queue_tail + 1) % QUEUESIZE;
+  }
+  
+  if (!queue_changed)
+  {
+      queue_changed = 1;
+      // Trigger the read handler
+      write(pipe_write_fd, &c, 1);
+  }
+}
+
+bool
+DNotify::is_active()
+{
+    if (pipe_read_fd == -2)
+    {
+        int filedes[2];
+	int res;
+	
+	res = pipe (filedes);
+	if (res >= 0)
+	{   Log::debug("opened pipe");
+   	    pipe_read_fd = filedes[0];
+   	    pipe_write_fd = filedes[1];
+
+	    // Setup signal handler:
+	    struct sigaction act;
+	    
+	    act.sa_sigaction = signal_handler;
+	    sigemptyset(&act.sa_mask);
+	    act.sa_flags = SA_SIGINFO;
+	    sigaction(SIGRTMIN, &act, NULL);
+
+	    // When the RT queue overflows we get a SIGIO
+	    act.sa_sigaction = overflow_signal_handler;
+	    sigemptyset(&act.sa_mask);
+	    sigaction(SIGIO, &act, NULL);
+
+	    (void) Scheduler::install_read_handler(pipe_read_fd, read_handler, NULL);
+	}
+    }
+    return pipe_read_fd >= 0;
+}
+
+DNotify::DirWatch *
+DNotify::lookup_dirwatch (int fd)
+{
+  DirWatch **p;
+  DirWatch *w;
+
+  p = dir_hashchain (fd);
+
+  while (*p)
+    {
+      w = *p;
+
+      if (w->fd == fd)
+	return w;
+
+      p = &w->hash_link;
+    }
+  
+  return *p;
+}
+
+// This colud be made faster by using another hash table.
+// But it's not that bad, since it is only used by express/revoke
+DNotify::DirWatch *
+DNotify::lookup_dirwatch (dev_t dir_dev, ino_t dir_ino)
+{
+  DirWatch *p;
+  int i;
+
+  for (i=0;i<DIR_HASHSIZE;i++)
+    {
+      p = dir_hash[i];
+      
+      while (p)
+	{
+	  if (p->dir_dev == dir_dev && p->dir_ino == dir_ino)
+	    return p;
+	  
+	  p = p->hash_link;
+	}
+    }
+  
+  return NULL;
+}
+
+DNotify::FileWatch *
+DNotify::lookup_filewatch (dev_t dev, ino_t ino)
+{
+  FileWatch **p;
+  FileWatch *w;
+
+  p = file_hashchain (dev, ino);
+
+  while (*p)
+    {
+      w = *p;
+
+      if (w->file_dev == dev && w->file_ino == ino)
+	return w;
+
+      p = &w->hash_link;
+    }
+  
+  return *p;
+}
+
+// Make sure w is not already in the hash table before calling
+// this function.
+void
+DNotify::hash_dirwatch(DirWatch *w)
+{
+  DirWatch **p;
+  p = dir_hashchain (w->fd);
+  w->hash_link = *p;
+  *p = w;
+}
+
+// Make sure w is not already in the hash table before calling
+// this function.
+void
+DNotify::hash_filewatch(FileWatch *w)
+{
+  FileWatch **p;
+  p = file_hashchain (w->file_dev, w->file_ino);
+  w->hash_link = *p;
+  *p = w;
+}
+
+void
+DNotify::unhash_dirwatch(DirWatch *w)
+{
+  DirWatch **p;
+  
+  p = dir_hashchain (w->fd);
+  
+  while (*p)
+    {
+      if (*p == w)
+	{
+	  *p = w->hash_link;
+	  break;
+	}
+      p = &(*p)->hash_link;
+    }
+  w->hash_link = NULL;
+}
+
+void
+DNotify::unhash_filewatch(FileWatch *w)
+{
+  FileWatch **p;
+  
+  p = file_hashchain (w->file_dev, w->file_ino);
+  
+  while (*p)
+    {
+      if (*p == w)
+	{
+	  *p = w->hash_link;
+	  break;
+	}
+      p = &(*p)->hash_link;
+    }
+  w->hash_link = NULL;
+}
+
+DNotify::Status
+DNotify::watch_dir(const char *notify_dir, dev_t file_dev, ino_t file_ino)
+{
+  struct stat stat;
+  dev_t dir_dev;
+  ino_t dir_ino;
+  DirWatch *dwatch;
+  FileWatch *fw;
+    
+  if (lstat (notify_dir, &stat) == -1)
+      return BAD;
+  
+  dwatch = lookup_dirwatch(stat.st_dev, stat.st_ino);
+  if (!dwatch)
+    {
+      Log::debug ("New DirWatch for %s (%x %x)\n",
+		  notify_dir, (int)stat.st_dev, (int)stat.st_ino);
+      dwatch = new DirWatch;
+      dwatch->watches = NULL;
+      dwatch->hash_link = NULL;
+      dwatch->dir_dev = stat.st_dev;
+      dwatch->dir_ino = stat.st_ino;
+      
+      dwatch->fd = open(notify_dir, O_RDONLY);
+      fcntl (dwatch->fd, F_SETSIG, SIGRTMIN);
+      if (fcntl (dwatch->fd, F_NOTIFY,
+                 (DN_MODIFY|DN_CREATE|DN_DELETE|DN_RENAME|DN_ATTRIB) 
+		  | DN_MULTISHOT) == -1) {
+	      return BAD;
+      }
+      hash_dirwatch (dwatch);
+    }
+
+  fw = lookup_filewatch (file_dev, file_ino);
+  if (fw && fw->dir_watch == dwatch)
+	return OK;
+  
+  // No old FileWatch, need to add one:
+  Log::debug("New FileWatch for %x %x\n", (int)file_dev, (int)file_ino);
+  fw = new FileWatch;
+  fw->next = dwatch->watches;
+  dwatch->watches = fw;
+  fw->file_dev = file_dev;
+  fw->file_ino = file_ino;
+  fw->dir_watch = dwatch;
+  hash_filewatch(fw);
+  return OK;
+}
+
+char *
+dirname_dup (const char *name)
+{
+  char *copy = strdup(name);
+  char *res = dirname(copy);
+  res = strdup(res);
+  free (copy);
+  return res;
+}
+
+DNotify::Status
+DNotify::express(const char *name, struct stat *status)
+{
+    struct stat stat;
+    char *notify_dir;
+    int res;
+    Status s;
+    dev_t dev;
+    ino_t ino;
+
+    Log::debug("express() name: %s\n", name);
+
+    if (!is_active())
+	return BAD;
+
+    if (::lstat (name, &stat) == -1)
+      return BAD;
+
+    dev = stat.st_dev;
+    ino = stat.st_ino;
+    
+    if ((stat.st_mode & S_IFMT) != S_IFDIR)
+	notify_dir = dirname_dup (name);
+    else
+	notify_dir = (char *)name;
+
+    s = watch_dir (notify_dir, dev, ino);
+    if (notify_dir != name)
+        free (notify_dir);
+    if (s)
+      return s;
+
+    // Check for a race condition; if someone removed or changed the
+    // file at the same time that we are expressing interest in it,
+    // revoke the interest so we don't get notifications about changes
+    // to a recycled inode that we don't otherwise care about.
+    //
+    struct stat st;
+    if (status == NULL) {
+	status = &st;
+    }
+    if (::lstat(name, status) == -1) {
+	Log::perror("stat on \"%s\" failed", name);
+	revoke(name, stat.st_dev, stat.st_ino);
+	return BAD;
+    }
+    if (status->st_dev != stat.st_dev
+	|| status->st_ino != stat.st_ino) {
+	Log::error("File \"%s\" changed between express and stat",
+		   name);
+	revoke(name, stat.st_dev, stat.st_ino);
+	return BAD;
+    }	
+
+    Log::debug("told dnotify to monitor \"%s\" = dev %d/%d, ino %d", name,
+	       major(status->st_dev), minor(status->st_dev),
+	       status->st_ino);
+    return OK;
+}
+
+DNotify::Status
+DNotify::revoke(const char *name, dev_t dev, ino_t ino)
+{
+    FileWatch *fwatch;
+    DirWatch *dwatch;
+    
+    Log::debug("revoke() name: %s, dev: %x, ino: %x\n", name, dev, ino);
+
+    if (!is_active())
+	return BAD;
+
+    // Lookup FileWatch by dev:ino, and its DirWatch.
+    fwatch = lookup_filewatch (dev, ino);
+    if (fwatch == NULL)
+	return BAD;
+    
+    dwatch = fwatch->dir_watch;
+    
+    // delete FileWatch, if last FileWatch: close fd, delete DirWatch
+    Log::debug ("Destroying FileWatch for (%x %x)\n",
+		(int)fwatch->file_dev, (int)fwatch->file_ino);
+    FileWatch **p;
+    for (p=&dwatch->watches; *p; p=&(*p)->next)
+    {
+      if (*p == fwatch)
+	{
+	  *p = (*p)->next;
+	  break;
+	}
+    }
+    unhash_filewatch(fwatch);
+    delete fwatch;
+    if (dwatch->watches == NULL)
+      {
+	Log::debug ("Destroying DirWatch for (%x %x)\n",
+		    (int)dwatch->dir_dev, (int)dwatch->dir_ino);
+	close(dwatch->fd);
+	unhash_dirwatch(dwatch);
+	delete dwatch;
+      }
+  
+    return OK;
+}
+
+
+void
+DNotify::all_watches_changed(void)
+{
+  int i;
+  FileWatch *fw;
+
+  for (i=0; i<FILE_HASHSIZE; i++)
+  {
+      fw = file_hash[i];
+      while (fw)
+      {
+	  (*ehandler)(fw->file_dev, fw->file_ino, CHANGE);
+
+	  fw = fw->hash_link;
+      }
+  }
+}
+
+
+void
+DNotify::read_handler(int fd, void *)
+{
+    static char readbuf[5000];
+    DirWatch *dw;
+    FileWatch *fw;
+    int snap_queue_tail;
+    int last_fd;
+
+    int rc = read(fd, readbuf, sizeof readbuf);
+    queue_changed = 0;
+    if (rc < 0)
+        Log::perror("pipe read");
+    else if (queue_overflowed)
+    {
+	  // There is a *slight* race condition here. Between reading
+	  // the queue_overflow flag and resetting it. But it doesn't
+	  // matter, since I'm gonna handle the overflow after reseting
+	  // anyway.
+	  queue_overflowed = false;
+
+	  // We're soon gonna check all watches anyway, so
+	  // get rid of the current queue
+	  queue_head = queue_tail;
+	  
+	  all_watches_changed ();
+    }
+    else
+    {
+	// Don't read events that happen later than
+	// the initial read. (Otherwise skipping fd's
+	// might miss some changes).
+	snap_queue_tail = queue_tail;
+	last_fd = -1;
+	while (queue_head != snap_queue_tail)
+	{
+	    fd = change_queue[queue_head];
+	    queue_head = (queue_head + 1) % QUEUESIZE;
+
+	    // Skip multiple changes to the same fd
+	    if (fd != last_fd)
+	    {
+		dw = lookup_dirwatch (fd);
+		if (dw)
+		{
+		    int n_watches, i;
+		    ChangeEventData *data;
+		    
+		    Log::debug("dnotify said dev %d/%d, ino %ld changed",
+			       major(dw->dir_dev), minor(dw->dir_dev), dw->dir_ino);
+		    
+		    n_watches = 0;
+		    for (fw=dw->watches; fw; fw=fw->next)
+			n_watches++;
+		    
+		    data = new ChangeEventData[n_watches];
+
+		    i = 0;
+		    for (fw=dw->watches; fw; fw=fw->next)
+		    {
+			data[i].file_dev = fw->file_dev;
+			data[i].file_ino = fw->file_ino;
+			i++;
+		    }
+
+		    for (i = 0; i < n_watches; i++)
+		    {
+			(*ehandler)(data[i].file_dev, data[i].file_ino, CHANGE);
+		    }
+		    
+		    delete[] data;
+		}
+	    }
+	    last_fd = fd;
+	}
+    }
+}
+
diff -Naur fam-2.7.0.orig/src/DNotify.h fam-2.7.0/src/DNotify.h
--- fam-2.7.0.orig/src/DNotify.h	1970-01-01 00:00:00.000000000 +0000
+++ fam-2.7.0/src/DNotify.h	2004-03-15 21:31:34.546060811 +0000
@@ -0,0 +1,98 @@
+//  Copyright (C) 2001 Red Hat, Inc.  All Rights Reserved.
+//  Copyright (C) 1999 Silicon Graphics, Inc.  All Rights Reserved.
+//
+//  This program is free software; you can redistribute it and/or modify it
+//  under the terms of version 2 of the GNU General Public License as
+//  published by the Free Software Foundation.
+//
+//  This program is distributed in the hope that it would be useful, but
+//  WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  Further, any
+//  license provided herein, whether implied or otherwise, is limited to
+//  this program in accordance with the express provisions of the GNU
+//  General Public License.  Patent licenses, if any, provided herein do not
+//  apply to combinations of this program with other product or programs, or
+//  any other product whatsoever.  This program is distributed without any
+//  warranty that the program is delivered free of the rightful claim of any
+//  third person by way of infringement or the like.  See the GNU General
+//  Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License along
+//  with this program; if not, write the Free Software Foundation, Inc., 59
+//  Temple Place - Suite 330, Boston MA 02111-1307, USA.
+
+#ifndef DNotify_included
+#define DNotify_included
+
+#include "config.h"
+#include "Monitor.h"
+#include <signal.h>
+
+//  DNotify is an object encapsulating the dnotify linux fcntl.
+//  It "emulates" the IMon interface.
+//  There can only be one instantiation of the DNotify object.
+//
+//  The user of this object uses express() and revoke() to
+//  express/revoke interest in a file.  There is also
+//  a callback, the EventHandler.  When an dnotify event comes in,
+//  the EventHandler is called.
+//
+//  The user of the DNotify object is the Interest class.
+
+class DNotify : public Monitor {
+public:
+    DNotify(EventHandler h);
+    ~DNotify();
+
+    static bool is_active();
+
+    virtual Status express(const char *name, struct stat *stat_return);
+    virtual Status revoke(const char *name, dev_t dev, ino_t ino);
+
+private:
+    struct FileWatch;
+    struct DirWatch;
+    struct ChangeEventData;
+  
+    //  Class Variables
+    enum { QUEUESIZE = 1024 };
+    static int pipe_write_fd;
+    static int pipe_read_fd;
+    static int change_queue[QUEUESIZE];
+    static volatile sig_atomic_t DNotify::queue_overflowed;
+    static volatile sig_atomic_t DNotify::queue_changed;
+    static volatile int queue_head; // Only modified by read handler
+    static volatile int queue_tail; // Only modified by signal handler
+    static EventHandler ehandler;
+    static void overflow_signal_handler(int sig, siginfo_t *si, void *data);
+    static void signal_handler(int sig, siginfo_t *si, void *data);
+    static void read_handler(int fd, void *closure);
+ 
+    enum { DIR_HASHSIZE = 367 };
+    static DirWatch *dir_hash[DIR_HASHSIZE];
+    enum { FILE_HASHSIZE = 823 };
+    static FileWatch *file_hash[FILE_HASHSIZE];
+
+    static DirWatch **dir_hashchain(int fd)
+			  { return &dir_hash[(unsigned) (fd) % DIR_HASHSIZE]; }
+    static FileWatch **file_hashchain(dev_t d, ino_t i)
+			  { return &file_hash[(unsigned) (d+i) % FILE_HASHSIZE]; }
+
+    static DirWatch *lookup_dirwatch (int fd);
+    static DirWatch *lookup_dirwatch (dev_t dir_dev, ino_t dir_ino);
+    static FileWatch *lookup_filewatch (dev_t file_dev, ino_t file_ino);
+    static void hash_dirwatch(DirWatch *w);
+    static void hash_filewatch(FileWatch *w);
+    static void unhash_dirwatch(DirWatch *w);
+    static void unhash_filewatch(FileWatch *w);
+    static Status watch_dir(const char *notify_dir, dev_t file_dev, ino_t file_ino);
+
+    static void all_watches_changed(void);
+    
+    DNotify(const DNotify&);			// Do not copy
+    DNotify & operator = (const DNotify&);	//  or assign.
+};
+
+#endif /* !IMon_included */
+
+
diff -Naur fam-2.7.0.orig/src/IMon.h fam-2.7.0/src/IMon.h
--- fam-2.7.0.orig/src/IMon.h	2003-01-18 14:18:12.000000000 +0000
+++ fam-2.7.0/src/IMon.h	2004-03-15 21:31:34.558058615 +0000
@@ -24,10 +24,7 @@
 #define IMon_included
 
 #include "config.h"
-#include <sys/stat.h>
-#include <sys/types.h>
-
-#include "Boolean.h"
+#include "Monitor.h"
 
 struct stat;
 
@@ -41,25 +38,18 @@
 //
 //  The user of the IMon object is the Interest class.
 
-class IMon {
+class IMon : public Monitor {
 
 public:
-
-    enum Status { OK = 0, BAD = -1 };
-    enum Event { EXEC, EXIT, CHANGE };
-
-    typedef void (*EventHandler)(dev_t, ino_t, int event);
-
     IMon(EventHandler h);
     ~IMon();
 
     static bool is_active();
 
-    Status express(const char *name, struct stat *stat_return);
-    Status revoke(const char *name, dev_t dev, ino_t ino);
+    virtual Status express(const char *name, struct stat *stat_return);
+    virtual Status revoke(const char *name, dev_t dev, ino_t ino);
 
 private:
-
     //  Class Variables
 
     static int imonfd;
diff -Naur fam-2.7.0.orig/src/Interest.c++ fam-2.7.0/src/Interest.c++
--- fam-2.7.0.orig/src/Interest.c++	2003-01-18 14:18:12.000000000 +0000
+++ fam-2.7.0/src/Interest.c++	2004-03-15 21:31:34.550060079 +0000
@@ -42,12 +42,21 @@
 #include "Event.h"
 #include "FileSystem.h"
 #include "IMon.h"
+#include "DNotify.h"
 #include "Log.h"
 #include "Pollster.h"
 #include "timeval.h"
 
 Interest *Interest::hashtable[];
-IMon      Interest::imon(imon_handler);
+
+#ifdef USE_DNOTIFY 
+static DNotify dnotify(Interest::monitor_handler);
+Monitor * Interest::monitor = &dnotify;
+#else
+static IMon imon(Interest::monitor_handler);
+Monitor * Interest::monitor = &imon;
+#endif
+
 bool      Interest::xtab_verification = true;
 
 Interest::Interest(const char *name, FileSystem *fs, in_addr host, ExportVerification ev)
@@ -60,10 +69,10 @@
       mypath_exported_to_host(ev == NO_VERIFY_EXPORTED)
 {
     memset(&old_stat, 0, sizeof(old_stat)); 
-    IMon::Status s = IMon::BAD;
 
-    s = imon.express(name, &old_stat);
-    if (s != IMon::OK)
+    Monitor::Status s = Monitor::BAD;
+    s = monitor->express(name, &old_stat);
+    if (s != Monitor::OK)
     {   int rc = lstat(name, &old_stat);
 	if (rc < 0)
 	{   Log::info("can't lstat %s", name);
@@ -100,7 +109,7 @@
     }
 #endif
 
-    if (exported_to_host()) fs->ll_monitor(this, s == IMon::OK);
+    if (exported_to_host()) fs->ll_monitor(this, s == Monitor::OK);
 }
 
 Interest::~Interest()
@@ -128,7 +137,7 @@
 		pp = &p->hashlink;	// move to next element
 	    }
 	if (!found_same)
-	    (void) imon.revoke(name(), dev, ino);
+	  (void) monitor->revoke(name(), dev, ino);
     }
 }
 
@@ -147,7 +156,7 @@
 
         // Express interest.
         IMon::Status s = IMon::BAD;
-	s = imon.express(name(), NULL);
+	s = monitor->express(name(), NULL);
         if (s != IMon::OK) {
             return true;
         }
@@ -248,23 +257,23 @@
 }
 
 void
-Interest::imon_handler(dev_t device, ino_t inumber, int event)
+Interest::monitor_handler(dev_t device, ino_t inumber, int event)
 {
     assert(device || inumber);
 
     for (Interest *p = *hashchain(device, inumber), *next = p; p; p = next)
     {	next = p->hashlink;
 	if (p->ino == inumber && p->dev == device)
-	{   if (event == IMon::EXEC)
+	  {   if (event == Monitor::EXEC)
 	    {   p->cur_exec_state = EXECUTING;
 		(void) p->report_exec_state();
 	    }
-	    else if (event == IMon::EXIT)
+	    else if (event == Monitor::EXIT)
 	    {   p->cur_exec_state = NOT_EXECUTING;
 		(void) p->report_exec_state();
 	    }
 	    else
-	    {   assert(event == IMon::CHANGE);
+	    {   assert(event == Monitor::CHANGE);
 		p->scan();
 	    }
 	}
diff -Naur fam-2.7.0.orig/src/Interest.h fam-2.7.0/src/Interest.h
--- fam-2.7.0.orig/src/Interest.h	2003-01-18 14:18:12.000000000 +0000
+++ fam-2.7.0/src/Interest.h	2004-03-15 21:31:34.560058249 +0000
@@ -32,7 +32,7 @@
 
 class Event;
 class FileSystem;
-class IMon;
+class Monitor;
 struct stat;
 
 //  Interest -- abstract base class for filesystem entities of interest.
@@ -74,7 +74,7 @@
 
     //  Public Class Method
 
-    static void imon_handler(dev_t, ino_t, int event);
+    static void monitor_handler(dev_t, ino_t, int event);
 
     static void enable_xtab_verification(bool enable);
 
@@ -121,7 +121,7 @@
 
     //  Class Variables
 
-    static IMon imon;
+    static Monitor *monitor;
     static Interest *hashtable[HASHSIZE];
     static bool xtab_verification;
 
diff -Naur fam-2.7.0.orig/src/Makefile.am fam-2.7.0/src/Makefile.am
--- fam-2.7.0.orig/src/Makefile.am	2003-01-19 12:00:17.000000000 +0000
+++ fam-2.7.0/src/Makefile.am	2004-03-15 21:31:34.562057882 +0000
@@ -71,7 +71,11 @@
   main.c++ \
   timeval.c++ \
   timeval.h \
-  @MONITOR_FUNCS@.c++
+  Monitor.h \
+  DNotify.h \
+  DNotify.c++ \
+  @MONITOR_FUNCS@.c++ 
 
-EXTRA_famd_SOURCES = IMonIrix.c++ IMonLinux.c++ IMonNone.c++
+EXTRA_famd_SOURCES = IMonIrix.c++ IMonLinux.c++ IMonNone.c++ DNotify.c++ \
+  DNotify.h Monitor.h
 
diff -Naur fam-2.7.0.orig/src/Monitor.h fam-2.7.0/src/Monitor.h
--- fam-2.7.0.orig/src/Monitor.h	1970-01-01 00:00:00.000000000 +0000
+++ fam-2.7.0/src/Monitor.h	2004-03-15 21:31:34.564057516 +0000
@@ -0,0 +1,57 @@
+//  Copyright (C) 2001 Red Hat, Inc.  All Rights Reserved.
+//  Copyright (C) 1999 Silicon Graphics, Inc.  All Rights Reserved.
+//  
+//  This program is free software; you can redistribute it and/or modify it
+//  under the terms of version 2 of the GNU General Public License as
+//  published by the Free Software Foundation.
+//
+//  This program is distributed in the hope that it would be useful, but
+//  WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  Further, any
+//  license provided herein, whether implied or otherwise, is limited to
+//  this program in accordance with the express provisions of the GNU
+//  General Public License.  Patent licenses, if any, provided herein do not
+//  apply to combinations of this program with other product or programs, or
+//  any other product whatsoever.  This program is distributed without any
+//  warranty that the program is delivered free of the rightful claim of any
+//  third person by way of infringement or the like.  See the GNU General
+//  Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License along
+//  with this program; if not, write the Free Software Foundation, Inc., 59
+//  Temple Place - Suite 330, Boston MA 02111-1307, USA.
+
+#ifndef Monitor_included
+#define Monitor_included
+
+#include "config.h"
+#include <sys/stat.h>
+#include <sys/types.h>
+
+struct stat;
+
+//  Monitor is an abstract baseclass for differend file monitoring
+//  systems. The original system used was IMon, and the Montor API
+//  is heavily influenced by that.
+//  There can only be one instantiation of the Monitor object.
+//
+//  The user of this object uses express() and revoke() to
+//  express/revoke interest in a file to imon.  There is also
+//  a callback, the EventHandler.  When an event comes in,
+//  the EventHandler is called.
+//
+//  The main implementers of the Monitor class is IMon and DNotify
+
+class Monitor {
+public:
+
+    enum Status { OK = 0, BAD = -1 };
+    enum Event { EXEC, EXIT, CHANGE };
+
+    typedef void (*EventHandler)(dev_t, ino_t, int event);
+
+    virtual Status express(const char *name, struct stat *stat_return) = 0;
+    virtual Status revoke(const char *name, dev_t dev, ino_t ino) = 0;
+};
+
+#endif /* !Monitor_included */
