Even with the resources available, such as the Microsoft IFS Kit, developing file systems is certainly a challenge. Many projects, however, can be accomplished by implementing a file system filter driver rather than a full file system. Because Windows provides the facilities needed to layer one driver on top of another, a filter driver can be built so that it intercepts and processes requests both before and after the file system handles them For many projects this is precisely what is required. Of course, some projects may require development of a completely new file system, in which case the OSR File Systems Development Kit should be used.

There are several available "examples" of how to build a file system filter driver on Windows. These samples all suffer from the same problem - namely, that they are merely passive filters. In other words, simple monitoring examples. Once you begin to modify the examples to change the flow of operations, they become active filters and suddenly you begin to find new and interesting behavior problems when filtering underlying file systems.

To simplify your development and to provide you with a robust and well-tested file system filter driver that works with all versions and patch releases of the Windows NT "family" of operating systems supported by Microsoft, OSR offers the file system Filter Driver Development Kit (FDDK) which provides a complete, modular environment for building active file system filters.

This product is best suited for development teams that need to get their product to market quickly and with a minimal number of bugs. Why? Because the FDDK has been shipping to OSR customers since 1996. It is included in nearly three dozen commercial applications, on a variety of platforms, and under a variety of conditions. Because of this, you can be assured that the FDDK will provide a high quality base for your project. Plus, you have the peace of mind of knowing that the OSR technical team will be there to answer your questions and resolve any problems that arise in the future.

The FDDK provides all the features needed to provide file system filtering services for Windows, including:

• Support for dynamic file system recognition. Windows does not load file systems at boot time. Rather, they are loaded during the normal course of system execution. The FDDK includes a "recognizer" component which handles these dynamic file system load events.
  
• Support for removable media. Windows creates "device objects" for each file system instance. When media is changed in a drive supporting such operations, the old "device object" is deleted and a new "device object" is created for the new media. The filtering component of the FDDK includes support for such media change events.
  
• Support for fast I/O, including the fast I/O entry points. Windows allows file systems to support "fast I/O" entry points. The FDDK includes full support for all entries in the fast I/O entry table to ensure proper compatibility with other Windows kernel components (such as the LanManager server, SRV) which rely upon this behavior.
  
• Support for Paging I/O. Since Windows file systems must support paging I/O, the FDDK passes all I/O, including paging I/O, to the functionality driver. The functionality driver is responsible for handling paging I/O.
  
• Support for user-written Functionality Drivers. As supplied, the FDDK will call a separate user-written Functionality Driver whenever an I/O Request Packet of the desired type is passed to a file system that is being filtered. Several example Functionality Drivers are supplied with the FDDK to help get you started.
  
• The FDDK only requires the Windows DDK, available as part of the Microsoft Software Developer's Network subscription and the Microsoft Visual C/C++ V4.2 (or later) compiler. No additional development kit of any kind is needed from Microsoft.
  
• Full portability. The source code in the FDDK is written in C with no assembly language and no architectural dependencies. It can be used on the x86 platform without requiring code changes.
  

The FDDK is completely compatible with Windows NT 4.0, Windows 2000 and Windows XP on both the Workstation and Server platforms, including all variants and patch releases.

Your investment in the FDDK is sure to be a valuable one. In addition to OSR's own internal testing, the FDDK is actively in use in numerous commercial products. Thus, you have the benefit of basing your project on a solid base. Further, you are protected against both bugs and obsolescence in the FDDK with one full year of support by OSR's world-class technical staff.

Contact OSR for more information, or for questions regarding the FDDK.