WMI SDK Sample - HiPerfProvider

Windows Management Instrumentation SDK Sample

HiPerfProvider

The HiPerfProvider sample demonstrates the basic framework of a high performance provider. The WMI high performance API is only supported on Windows 2000 platforms.

In an attempt to model a real world environment, this sample contains a data-source object (CSampleDataSource) that maintains 5 instances (CSampleInstance) of a hypothetical object which has 5 counter values that will each contain some contrived value. When a refresh is requested, the WMI objects are updated from this virtual data-source, just as they would be in a real world scenario. Note that the only time that HiPerfProvider updates the WMI objects is during a refresh.

The CHiPerfProvider class implements both the IWbemProviderInit and IWbemHiPerfProvider interfaces. The IWbemProviderInit interface is the basic interface that all providers must implement. The IWbemHiPerfProvider interface contains a set of methods that create and manage refreshers.

The CRefresher class is the class that implements the IWbemRefresher interface. The refresher maintains a list of up to 10 enumerators that have been added to the refresher as well as a mapping of ID’s to WMI object instances. When either an enumerator or an instance has been added to the refresher, it is assigned an ID for future reference. For a refresher, the ID is the first available element in the m_apEnumerator array. The ID of an instance is generated incrementally starting from a value greater than the maximum value that an enumerator ID can be. The ID is then mapped to a WMI object within the refresher and the mapping is stored in the m_apInstMap array. When an instance is removed from the refresher, the mapping is simply removed.

The only COM method in IWbemRefresher other than the standard set of COM methods is Refresh. This method is called when the client has requested that the instances within a refresher are to be updated and represents the only time that the value of a WMI object within a refresher may be modified. The remaining functions of CRefresher are primarily used for managing the refresher’s contents.

NOTE: The HiPerfProvider sample has been designed to work with the HiPerfClient sample. Please see the HiPerfClient sample documentation for instructions on building and using the client sample.

Building the Provider DLL

The DLL can be built from the command line using NMAKE, or it can be built using Microsoft Visual C++.

From the command line in the sample installation directory, type the following:

NMAKE /f "Makefile"

From Microsoft Visual C++:

1. Select File + Open Workspace

2. Select the BasicHiPerf.DSP file

Registering the DLL and Class

1. The DLL must be registered with COM. From the command line in the sample installation directory, type the following:

REGSVR32 BasicHiPerf.dll

2. You must also compile the MOF in order to make the WMI CIMOM aware of the class. From the command line in the sample installation directory, type the following:

MOFCOMP BasicHiPerf.MOF

At this point, you should be able to exercise the provider using the HiPerfClient sample.

General Notes

Things to remember when you're building your own WMI provider:

1. WMI interfaces are defined in wbemcli.h and wbemprov.h found in the wmi\include directory. You may #include both these files by including just wbemidl.h located in the same directory.

2. WMI interface CLSIDs are defined in wbemuuid.lib. If you get unresolved externals in interfaces and CLSIDs, this is what is missing.

3. You'll need to link with oleaut32.lib and ole32.lib to get the needed COM support.

4. In the Link|Output settings, specify 'wWinMainCRTStartup' as the entry point. This is per the Unicode programming instructions.

5. If you're using the makefiles, don't forget to set the Visual C++ environment variables. This is done by running VCVARS32.BAT.