private async Task SetDirectoryHandle()
{
await Task.Run(() =>
{
var directoryHandle = WindowsFacade.CreateFile(
Config.PathToWatch,
FileSystemConstants.FileListDirectory, // access (read-write) mode
FileSystemConstants.FileShareRead | FileSystemConstants.FileShareDelete |
FileSystemConstants.FileShareWrite, // share mode
null, // security descriptor
FileSystemConstants.OpenExisting, // how to create
FileSystemConstants.FileFlagBackupSemantics | FileSystemConstants.FileFlagOverlapped,
// file attributes
new SafeFileHandle(IntPtr.Zero, false) // file with attributes to copy
);
if (!directoryHandle.IsHandleValid())
{
throw new ApplicationException(
$"Swatcher failed to start because it couldn't access the folder path provided in configuration.");
}
DirectoryHandle = directoryHandle;
})
.ConfigureAwait(false);
}
private unsafe void SignalWorkerThreadsToStop()
{
Observable.Interval(TimeSpan.FromMilliseconds(25))
.TakeWhile(_ => _runningThreads > 0)
.Select(_ =>
{
var result = new SwatcherAsyncResult {
Buffer = new byte[0]
};
var overlapped = new Overlapped {
AsyncResult = result
};
//the first parameter is null because we're not using IO completion callbacks; they're too slow.
//we're taking the byte array from our empty byte array and passing that as user data to the overlapped.
var overlappedPointer = overlapped.UnsafePack(null, result.Buffer);
//when using IOCPs, we can send our own custom messages to the GetQueuedCompletionStatus
//method by call PostQueuedCompletionStatus. In this case, we want to stop the threads that are
//waiting on change events, so we will send a custom completion key "StopIocpThreads".
WindowsFacade.PostQueuedCompletionStatus(CompletionPortHandle, 0, StopIocpThreads, overlappedPointer);
return(Unit.Default);
})
.AsCompletion()
.Where(_ => Config.LoggingEnabled)
.Subscribe(_ =>
{
Disposables.Dispose();
Logger.Info("Swatcher has stopped");
});
}
private async Task SetCompletionPortHandle(int completionKey)
{
await Task.Run(() =>
{
//if the completion port doesn't exist yet, this call will create it.
//if it already exists, this call will bind the directory handle to the completion port,
//whilst retaining any other directory handles that were previously bound.
//passing 0 to the last parameter uses the default number of concurrent threads, which
//is the number of CPUs on the machine.
var pointer = WindowsFacade.CreateIoCompletionPort(
DirectoryHandle, SafeLocalMemHandle.Empty,
(uint)completionKey, (uint)Environment.ProcessorCount);
CompletionPortHandle = new SafeLocalMemHandle(pointer);
})
.ConfigureAwait(false);
}
