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  · DriverStudio          Calling WDM Services from Windows 98 VxDs
  · DriverBundle
  · Previews              If you are developing VxDs specifically for Windows
  · Compatibility         98, you might occasionally need to call a WDM service
 [Downloads]  ·           from a VxD. The Windows 98 DDK has some limited
                          support for doing this, although it isn't fully
 Wizards                  documented.
  · Utilities
  · NT source             In subdirectory lib\i386\free\win98 you'll find
 examples                 library wdmvxd.clb. This library gives you linkage to
  · VxD source            most if not all of the WDM entry points provided with
 examples                 Windows 98. Each of the object files loads registers
  · WDM source            and invokes INT 2Eh, which traps to a system
 examples                 dispatcher. Before invoking the called WDM service,
 [Resources]  ·           the dispatcher takes care of ensuring that the stack
 Technical papers         is set up for structured exception handling, which is
  · Useful links          supported in WDM drivers.
  · Technical tips
 [Support]  ·             The library is set up to look like an import library,
                          even though it does not result in any imports being
 Support                  generated. If you use DUMPBIN with the /linkermember
  · Knowledge base        switch, you'll see that the entry points are prefixed
  · Problem               with __imp_. This was done so that you can use
 submission               prototypes directly from wdm.h.
  · Product
 registration             For example, suppose you wanted to call
  · Release notes         RtlInitUnicodeString from a VxD. You would need this
 [Shop NuMega]  ·         prototype from wdm.h:
 Buy it!
  · Price list            NTSYSAPI
  · How to buy            VOID
  · Sales offices         NTAPI
                          RtlInitUnicodeString(
                             PUNICODE_STRING DestinationString,
 [Y2K Compliance]            PCWSTR SourceString
                             );

 [More information]       In addition, you may need these definitions:

                          #define NTSYSAPI __declspec(dllimport)
                          #define NTAPI __stdcall

                          Then it's simply a matter of having the typedef's and
                          linking against wdmvxd.clb.

                          Use wdmvxd.clb only when absolutely necessary, and
                          always with extreme caution. Because IRQL is largely
                          undefined in VxDs, there are numerous ways to get
                          into trouble when making these calls.

                          Back to technical tip start page.

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