private const int NAME_MAX = 255; // from limits.h
/// <summary>Initializes the instance with all state necessary to operate a watch.</summary>
internal RunningInstance(
FileSystemWatcher watcher, SafeFileHandle inotifyHandle, string directoryPath,
bool includeSubdirectories, Interop.libc.NotifyEvents notifyFilters, CancellationToken cancellationToken)
{
Debug.Assert(watcher != null);
Debug.Assert(inotifyHandle != null && !inotifyHandle.IsInvalid && !inotifyHandle.IsClosed);
Debug.Assert(directoryPath != null);
_weakWatcher = new WeakReference <FileSystemWatcher>(watcher);
_inotifyHandle = inotifyHandle;
_directoryPath = directoryPath;
_buffer = watcher.AllocateBuffer();
Debug.Assert(_buffer != null && _buffer.Length > (c_INotifyEventSize + NAME_MAX + 1));
_includeSubdirectories = includeSubdirectories;
_notifyFilters = notifyFilters;
_cancellationToken = cancellationToken;
FileSystemWatcher.CaseSensitive = true;
// Add a watch for this starting directory. We keep track of the watch descriptor => directory information
// mapping in a dictionary; this is needed in order to be able to determine the containing directory
// for all notifications so that we can reconstruct the full path.
AddDirectoryWatchUnlocked(null, directoryPath);
// Schedule a task to read from the inotify queue and process the events.
Task.Factory.StartNew(obj => ((RunningInstance)obj).ProcessEvents(),
this, CancellationToken.None, TaskCreationOptions.LongRunning, TaskScheduler.Default);
// PERF: As needed, we can look into making this use async I/O rather than burning
// a thread that blocks in the read syscall.
}
private const int NAME_MAX = 255; // from limits.h
/// <summary>Initializes the instance with all state necessary to operate a watch.</summary>
internal RunningInstance(
FileSystemWatcher watcher, SafeFileHandle inotifyHandle, string directoryPath,
bool includeSubdirectories, Interop.libc.NotifyEvents notifyFilters, CancellationToken cancellationToken)
{
Debug.Assert(watcher != null);
Debug.Assert(inotifyHandle != null && !inotifyHandle.IsInvalid && !inotifyHandle.IsClosed);
Debug.Assert(directoryPath != null);
_weakWatcher = new WeakReference<FileSystemWatcher>(watcher);
_inotifyHandle = inotifyHandle;
_directoryPath = directoryPath;
_buffer = watcher.AllocateBuffer();
Debug.Assert(_buffer != null && _buffer.Length > (c_INotifyEventSize + NAME_MAX + 1));
_includeSubdirectories = includeSubdirectories;
_notifyFilters = notifyFilters;
_cancellationToken = cancellationToken;
FileSystemWatcher.CaseSensitive = true;
// Add a watch for this starting directory. We keep track of the watch descriptor => directory information
// mapping in a dictionary; this is needed in order to be able to determine the containing directory
// for all notifications so that we can reconstruct the full path.
AddDirectoryWatchUnlocked(null, directoryPath);
// Schedule a task to read from the inotify queue and process the events.
Task.Factory.StartNew(obj => ((RunningInstance)obj).ProcessEvents(),
this, CancellationToken.None, TaskCreationOptions.LongRunning, TaskScheduler.Default);
// PERF: As needed, we can look into making this use async I/O rather than burning
// a thread that blocks in the read syscall.
}
/// <summary>
/// Main processing loop. This is currently implemented as a synchronous operation that continually
/// reads events and processes them... in the future, this could be changed to use asynchronous processing
/// if the impact of using a thread-per-FileSystemWatcher is too high.
/// </summary>
private void ProcessEvents()
{
// When cancellation is requested, clear out all watches. This should force any active or future reads
// on the inotify handle to return 0 bytes read immediately, allowing us to wake up from the blocking call
// and exit the processing loop and clean up.
var ctr = _cancellationToken.Register(obj => ((RunningInstance)obj).CancellationCallback(), this);
try
{
// Previous event information
string previousEventName = null;
WatchedDirectory previousEventParent = null;
uint previousEventCookie = 0;
// Process events as long as we're not canceled and there are more to read...
NotifyEvent nextEvent;
while (!_cancellationToken.IsCancellationRequested && TryReadEvent(out nextEvent))
{
// Try to get the actual watcher from our weak reference. We maintain a weak reference most of the time
// so as to avoid a rooted cycle that would prevent our processing loop from ever ending
// if the watcher is dropped by the user without being disposed. If we can't get the watcher,
// there's nothing more to do (we can't raise events), so bail.
FileSystemWatcher watcher;
if (!_weakWatcher.TryGetTarget(out watcher))
{
break;
}
uint mask = nextEvent.mask;
bool addWatch = false;
string expandedName = null;
WatchedDirectory associatedDirectoryEntry = null;
if (nextEvent.wd != -1) // wd is -1 for events like IN_Q_OVERFLOW that aren't tied to a particular watch descriptor
{
// Look up the directory information for the supplied wd
lock (SyncObj)
{
if (!_wdToPathMap.TryGetValue(nextEvent.wd, out associatedDirectoryEntry))
{
// The watch descriptor could be missing from our dictionary if it was removed
// due to cancellation, or if we already removed it and this is a related event
// like IN_IGNORED. In any case, just ignore it... even if for some reason we
// should have the value, there's little we can do about it at this point,
// and there's no more processing of this event we can do without it.
continue;
}
}
expandedName = associatedDirectoryEntry.GetPath(true, nextEvent.name);
}
// Determine whether the affected object is a directory (rather than a file).
// If it is, we may need to do special processing, such as adding a watch for new
// directories if IncludeSubdirectories is enabled. Since we're only watching
// directories, any IN_IGNORED event is also for a directory.
bool isDir = (mask & (uint)(Interop.libc.NotifyEvents.IN_ISDIR | Interop.libc.NotifyEvents.IN_IGNORED)) != 0;
// Renames come in the form of two events: IN_MOVED_FROM and IN_MOVED_TO.
// In general, these should come as a sequence, one immediately after the other.
// So, we delay raising an event for IN_MOVED_FROM until we see what comes next.
if (previousEventName != null && ((mask & (uint)Interop.libc.NotifyEvents.IN_MOVED_TO) == 0 || previousEventCookie != nextEvent.cookie))
{
// IN_MOVED_FROM without an immediately-following corresponding IN_MOVED_TO.
// We have to assume that it was moved outside of our root watch path, which
// should be considered a deletion to match Win32 behavior.
// But since we explicitly added watches on directories, if it's a directory it'll
// still be watched, so we need to explicitly remove the watch.
if (previousEventParent != null && previousEventParent.Children != null)
{
// previousEventParent will be non-null iff the IN_MOVED_FROM
// was for a directory, in which case previousEventParent is that directory's
// parent and previousEventName is the name of the directory to be removed.
foreach (WatchedDirectory child in previousEventParent.Children)
{
if (child.Name == previousEventName)
{
RemoveWatchedDirectory(child);
break;
}
}
}
// Then fire the deletion event, even though the event was IN_MOVED_FROM.
watcher.NotifyFileSystemEventArgs(WatcherChangeTypes.Deleted, previousEventName);
previousEventName = null;
previousEventParent = null;
previousEventCookie = 0;
}
const Interop.libc.NotifyEvents switchMask =
Interop.libc.NotifyEvents.IN_Q_OVERFLOW | Interop.libc.NotifyEvents.IN_IGNORED |
Interop.libc.NotifyEvents.IN_CREATE | Interop.libc.NotifyEvents.IN_DELETE |
Interop.libc.NotifyEvents.IN_ACCESS | Interop.libc.NotifyEvents.IN_MODIFY | Interop.libc.NotifyEvents.IN_ATTRIB |
Interop.libc.NotifyEvents.IN_MOVED_FROM | Interop.libc.NotifyEvents.IN_MOVED_TO;
switch ((Interop.libc.NotifyEvents)(mask & (uint)switchMask))
{
case Interop.libc.NotifyEvents.IN_Q_OVERFLOW:
watcher.NotifyInternalBufferOverflowEvent();
break;
case Interop.libc.NotifyEvents.IN_CREATE:
watcher.NotifyFileSystemEventArgs(WatcherChangeTypes.Created, expandedName);
addWatch = true;
break;
case Interop.libc.NotifyEvents.IN_IGNORED:
// We're getting an IN_IGNORED because a directory watch was removed.
// and we're getting this far in our code because we still have an entry for it
// in our dictionary. So we want to clean up the relevant state, but not clean
// attempt to call back to inotify to remove the watches.
RemoveWatchedDirectory(associatedDirectoryEntry, removeInotify: false);
break;
case Interop.libc.NotifyEvents.IN_DELETE:
watcher.NotifyFileSystemEventArgs(WatcherChangeTypes.Deleted, expandedName);
// We don't explicitly RemoveWatchedDirectory here, as that'll be handled
// by IN_IGNORED processing if this is a directory.
break;
case Interop.libc.NotifyEvents.IN_ACCESS:
case Interop.libc.NotifyEvents.IN_MODIFY:
case Interop.libc.NotifyEvents.IN_ATTRIB:
watcher.NotifyFileSystemEventArgs(WatcherChangeTypes.Changed, expandedName);
break;
case Interop.libc.NotifyEvents.IN_MOVED_FROM:
previousEventName = expandedName;
previousEventParent = isDir ? associatedDirectoryEntry : null;
previousEventCookie = nextEvent.cookie;
break;
case Interop.libc.NotifyEvents.IN_MOVED_TO:
if (previousEventName != null)
{
// If the previous name from IN_MOVED_FROM is non-null, then this is a rename.
watcher.NotifyRenameEventArgs(WatcherChangeTypes.Renamed, expandedName, previousEventName);
}
else
{
// If it is null, then we didn't get an IN_MOVED_FROM (or we got it a long time
// ago and treated it as a deletion), in which case this is considered a creation.
watcher.NotifyFileSystemEventArgs(WatcherChangeTypes.Created, expandedName);
}
previousEventName = null;
previousEventParent = null;
previousEventCookie = 0;
addWatch = true; // for either rename or creation, we need to update our state
break;
}
// If the event signaled that there's a new subdirectory and if we're monitoring subdirectories,
// add a watch for it.
if (addWatch && isDir && _includeSubdirectories)
{
AddDirectoryWatch(associatedDirectoryEntry, nextEvent.name);
}
// Drop our strong reference to the watcher now that we're potentially going to block again for another read
watcher = null;
}
}
catch (Exception exc)
{
FileSystemWatcher watcher;
if (_weakWatcher.TryGetTarget(out watcher))
{
watcher.OnError(new ErrorEventArgs(exc));
}
}
finally
{
ctr.Dispose();
_inotifyHandle.Dispose();
}
}
/// <summary>
/// Maps the FileSystemWatcher's NotifyFilters enumeration to the
/// corresponding Interop.libc.NotifyEvents values.
/// </summary>
/// <param name="filters">The filters provided the by user.</param>
/// <returns>The corresponding NotifyEvents values to use with inotify.</returns>
private static Interop.libc.NotifyEvents TranslateFilters(NotifyFilters filters)
{
Interop.libc.NotifyEvents result = 0;
// We always include a few special inotify watch values that configure
// the watch's behavior.
result |=
Interop.libc.NotifyEvents.IN_ONLYDIR | // we only allow watches on directories
Interop.libc.NotifyEvents.IN_EXCL_UNLINK; // we want to stop monitoring unlinked files
// For the Created and Deleted events, we need to always
// register for the created/deleted inotify events, regardless
// of the supplied filters values. We explicitly don't include IN_DELETE_SELF.
// The Windows implementation doesn't include notifications for the root directory,
// and having this for subdirectories results in duplicate notifications, one from
// the parent and one from self.
result |=
Interop.libc.NotifyEvents.IN_CREATE |
Interop.libc.NotifyEvents.IN_DELETE;
// For the Changed event, which inotify events we subscribe to
// are based on the NotifyFilters supplied.
const NotifyFilters filtersForAccess =
NotifyFilters.LastAccess;
const NotifyFilters filtersForModify =
NotifyFilters.LastAccess |
NotifyFilters.LastWrite |
NotifyFilters.Security |
NotifyFilters.Size;
const NotifyFilters filtersForAttrib =
NotifyFilters.Attributes |
NotifyFilters.CreationTime |
NotifyFilters.LastAccess |
NotifyFilters.LastWrite |
NotifyFilters.Security |
NotifyFilters.Size;
if ((filters & filtersForAccess) != 0)
{
result |= Interop.libc.NotifyEvents.IN_ACCESS;
}
if ((filters & filtersForModify) != 0)
{
result |= Interop.libc.NotifyEvents.IN_MODIFY;
}
if ((filters & filtersForAttrib) != 0)
{
result |= Interop.libc.NotifyEvents.IN_ATTRIB;
}
// For the Rename event, we'll register for the corresponding move inotify events if the
// caller's NotifyFilters asks for notications related to names.
const NotifyFilters filtersForMoved =
NotifyFilters.FileName |
NotifyFilters.DirectoryName;
if ((filters & filtersForMoved) != 0)
{
result |=
Interop.libc.NotifyEvents.IN_MOVED_FROM |
Interop.libc.NotifyEvents.IN_MOVED_TO;
}
return(result);
}
