Pay-Per-View Authorization Component Sample

The Pay-per-View Authorization Component Sample, written in C++, provides a working example of how to write a Windows Media Services authorization plug-in component. The source code can be found in the C:\Program Files\Windows Media Components\SDK\Source\Authorization\ directory.

You can build the sample component either in Microsoft® Visual Studio® 98 (by opening NSMemberPPV.dsw workspace file and then, on the Tools menu, clicking Build).

Note If you are using Microsoft® Visual Studio® 97 to run this sample, you must download Microsoft® Active Directory Service Interfaces (ADSI) version 2.0 from the ADSI page at the Microsoft Web site.

This Pay-per-View Authorization Component implements a business logic to grant permission for a client to view a Windows Media Services title if the user is a member of the specified group and has paid for that title. Authorization is performed against the information available in the connected database.

The time frame in which the user is allowed to view the title is determined by entries in the database that have been set when the user paid.

The main class is CPayPerView, which implements the INSSEventNotification and INSSEventAuthorization interfaces for Windows Media Services event notification and authorization. The CPayPerView class handles initialization of the plug-in component, and all the communications to and from the server running Windows Media Services.

• The server calls the Initialize method to perform the following tasks:
  • Allow the server to pass in its information to the plug-in component through a pointer that points to the Server Context Object (*pServer). This informs lets the plug-in component know about attributes of the server.
    
    
  • Allow the plug-in component to specify a parameter, *dwHeartBeatPeriod, and to pass this parameter bach to the server. Later, the server calls the OnHeartBeat method of the plug-in component at the interval specified in this parameter.
    
    
  • Allow the plug-in component to get the LDAP database information from the registry and to bind to the LDAP server.
    
    
  • Allow the plug-in component to retrieve the initialization of objects that implement all customized policies for authorization. In this sample, two policies have been implemented: group policy and payment policy. A client who may view a title must be a member of the group and have a sufficient balance to pay for the title.
• The server calls the GetHandledEvents method to perform the following tasks:
  • Allow the component to specify a list of events that trigger a call to the OnEvent method.
    
    
  • Allow the component to pass back those events to the server.
• The server calls the GetAuthorizedEvents method to perform the following tasks:
  • Allow the component to specify a list of events that must be authorized, and trigger a call to the AuthorizeEvent method.
    
    
  • Allow the component to pass back those events to the server.
• The server calls the OnEvent method to inform the component that an event specified in the parameter rgHandledEvent occurs, which is specified in the GetHandledEvents method.
  
  
• The server calls the AuthorizeEvent method to request authorization when an event is specified in the parameter *pEvents, which is specified in the GetAuthorizedEvents method.
  
  
• After the component receives an AuthorizeEvent call, it notifies the server of the result of authorization by invoking the OnEventAuthorized callback method.

Calls to AuthorizeEvent return asynchronously (to avoid monopolizing a server thread for too long). As a result, most of the actual work involved in authorization and event notification is passed to separate worker threads through a 2000 I/O completion port in Microsoft® Windows NT® Server.

The CPayPerView class uses the CLDAPAccess class to maintain a connection to an ADO/ODBC data source for executing database queries and updates. It also uses the CSGroups class to implement the authorization policy. The CpayPerView, CLDAPAccess and CSGroups classes are contained in the PayPerView.cpp, LDAPAccess.cpp and Sgroups.cpp files, respectively.