Windows® 2000 Device Driver Book: A Guide for Programmers, Second Edition, The

Code Example: A Filter Driver

This example demonstrates a basic filter driver, called the HIFILTER, that intercepts all requests intended for a lower-level driver (LODRIVER). The purpose of the filter is to hide the lower driver's limited output transfer size. To do this, it breaks large transfer requests into smaller pieces. It also overrides an IOCTL from the lower driver that returns the maximum size of an output buffer. All other major function codes supported by the lower driver are passed through from the filter.

The code for this example is included on the accompanying disk and at the book's Web site: http://www.W2KDriverBook.com.

The DEVICE_EXTENSION Structure

The declarations of the Device Extension for the filter driver are minimal; ...