New file system monitoring component

[pyscripter 825]

Whilst there are many Delphi components for detecting changes to file system folders they suffer from serious limitations:

• typically they only allow you to monitor a single folder
• they do not support the monitoring of specific files
• they rely on the FindFirstChangeNotification API which gives no information about what has changed, requiring an inefficient search.

 

I have created a new file system monitoring library that addresses the above limitations.

 

Features:

• Easy to use, but also suitable for heavy duty monitoring
• Single unit with no external dependencies
• Allows monitoring folders and/or specific files
• Uses the ReadDirectoryChangesW API which provides information about what exactly was changed
• A single instance of the component can handle the monitoring of many folders and/or files
• Uses an I/O completion port for efficient handling of large numbers of requests
• A single thread handles all requests
• A different notification handler can be specified for each request

• You can have multiple handlers for each folder or file

• When you monitor folders you can specify whether you want to also monitor subfolders

 

Installation:

You do not need to install the library. Just download or clone the repo and add the source subdirectory to the Library path.

 

Usage:

procedure TForm1.FormCreate(Sender: TObject);
begin
  // Create the IFileSystemMonitor interface
  FFileSystemMonitor := CreateFileSystemMonitor;
  // Monitor a directory
  FFileSystemMonitor.AddDirectory(TPath.GetTempPath, False, HandleChange);
  // Also monitor a specific file
  FFileSystemMonitor.AddFile('pathtoyourfile',  HandleChange);
end;

procedure TForm1.HandleChange(Sender: TObject; const Path: string;
  ChangeType: TFileChangeType);
begin
  with lvEventList.Items.Add do
  begin
    Caption := GetEnumName(TypeInfo(TFileChangeType), Integer(ChangeType));
    SubItems.Add(Path);
  end;
end;

To stop monitoring a specific file or folder you use the following methods:

    function RemoveDirectory(const Directory: string; OnChange: TMonitorChangeHandler): Boolean;
    function RemoveFile(const FilePath: string; OnChange: TMonitorChangeHandler): Boolean;

 

Edited Tuesday at 09:22 PM by pyscripter

[Tommi Prami 157]

Very nice.  Way better than constant polling for sure.

I think I have no use for this now, but have to think about it, maybe I can think of something.

In previous live used FindFirstChangeNotification  API, did not knoew that there is other API for this.

-Tee-

Edited yesterday at 04:23 AM by Tommi Prami
typo

[Dave Novo 57]

Thanks for all the amazing work you do and contribute to the community!

[mjustin 31]

Sorry for asking, but is polling still necessary if the monitoring application (which uses IFileSystemMonitor) was not running for a while, and during that time changes happened?

Or does IFileSystemMonitor provide ways to detect changes which happened while it was "absent"?

[M.e.l 1]

Hi,

 

It looks simple and good.

Does it work across network or VPN ?

i.e. can a server directory be monitored from an app running your monitoring class on a client PC, connected to the server through network ?

 

Mel