YodaDrive

YodaDrive is a WebDAV client for Windows, allowing the user to mount a remove WebDAV server as a local drive. YodaDrive is derived from KS2.Drive written by Francois Karam, and depends on WinFsp written by Bill Zissimopoulos.

YodaDrive is a C# Visual Studio project, making use of the WebDAVClient library written by Itay Sagui (originally by Kees van den Broek).

YodaDrive has been optimized for iRODS servers accessed via davrods, but can be used for any WebDAV server.

Limitations

Since the remote file system is WebDAV, changes that originate elsewhere are not visible until the user refreshes the view. YodaDrive does not implement WebDAV locking.

Mode of operation

After a remote filesystem has been mounted, calls are made from Windows via WinFsp to Open, Create, Read, Write or Close files. YodaDrive handles Read and Write asynchronously, and all other calls synchronously.

For asynchronous Read and Write calls, YodaDrive returns STATUS_PENDING and later performs a callback when the Read or Write completes. Closing a file with pending Write calls will wait for all scheduled writes to complete, before the Close call returns.

YodaDrive uses one connection for downloads, and at most two connections for uploads.

Read

Downloads for all files in a remote filesystem are all managed on the same connection, with interleaved blocks for Read calls. Each Read call is translated into a separate GET request.

Write

Uploads are captured in a single PUT request if possible, as long as all Write calls address consecutive blocks. Each PUT request uses chunked mode, and blocks written are appended as chunks. The initial Write call does not have to address a block at the beginning of the file.

At most two uploads can be active at one time. Since consecutive writes are captured in a single PUT request, uploading two large files will prevent any other uploads for the duration. This is handled by postponing Create and Write calls until an upload connection becomes available; Create will pretend to succeed and Write will not have a callback until the actual block could be appended.

ReadDirectory

ReadDirectory is performed synchronously, but makes use of the download connection and can be blocked by pending asynchronous Read calls. Note that WinFsp permits ReadDirectory itself to be asynchronous, but we do not implement it as such.

State Diagrams