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This structure is used by HTTP_FILTER_PROC to obtain information about the current request. This structure is very similar in function to an ISAPI extension's EXTENSION_CONTROL_BLOCK structure.

      DWORD cbSize;
      DWORD Revision;
      PVOID ServerContext;
      DWORD ulReserved;
      BOOL fIsSecurePort;
      PVOID pFilterContext;
      BOOL GetServerVariable;
      BOOL AddResponseHeaders;
      BOOL WriteClient;
      VOID * AllocMem;
      BOOL ServerSupportFunction;


  • cbSize
    The size of this structure, in bytes.

  • Revision
    The revision level of this structure. This is less than or equal to the version of the document, HTTP_FILTER_REVISION.

  • ServerContext
    Reserved for server use.

  • ulReserved
    Reserved for server use.

  • fIsSecurePort
    A value of TRUE indicates that this event is over a secure port. A value of FALSE indicates that the event is not over a secure port.

  • pFilterContext
    Points to any context information that the filter wants to associate with this request. Any memory associated with this request can be safely freed during the SF_NOTIFY_END_OF_NET_SESSION notification.

  • GetServerVariable
    Points to a function that retrieves information about the server and this connection. For some notifications, some variables may not be defined. For example, notifications that occur before PREPROC_HEADERS, such as the READ_RAW_DATA notification, may not be defined.

  • AddResponseHeaders
    Points to the AddResponseHeaders function that adds a header to the HTTP response.

  • WriteClient
    Points to the WriteClient function that sends raw data back to the client.

  • AllocMem
    Points to the AllocMem function used to allocate memory. Any memory allocated with this function will automatically be freed when the session ends.

  • ServerSupportFunction
    Points to the ServerSupportFunction function used to extend the ISAPI filter functions. Parameters are specific to the extensions.


Client: Requires Windows XP Professional, Windows 2000 Professional, or Windows NT Workstation 4.0.

Server: Requires Windows Server 2003, Windows 2000 Server, or Windows NT Server 4.0.

Product: IIS

Header: Declared in httpfilt.h.

See Also