Callback Functions

Callback functions are used by the filter to communicate with IIS. When IIS calls an ISAPI filter's HttpFilterProc, it receives a pointer to an HTTP_FILTER_CONTEXT structure, which specifies, among other things, a callback function. Callback functions can also be specified from the HTTP_FILTER_PREPROC_HEADERS structure.

This section contains details about the callback functions available to ISAPI filters:

• AddHeader
• AddResponseHeaders
• AllocMem
• GetHeader
• GetServerVariable
• ServerSupportFunction
• SetHeader
• WriteClient

All function declarations and data structures are available in the ISAPI filter header file httpfilt.h.