SF_REQ_SET_NEXT_READ_SIZE callback function

Applies to: desktop apps only

The SF_REQ_SET_NEXT_READ_SIZE form of the ServerSupportFunction callback function is used by raw-read Web filters to set the number of bytes that will be read during the next read event.


BOOL WINAPI * ServerSupportFunction(
  _In_  struct _HTTP_FILTER_CONTEXT *pfc,
  _In_  enum SF_REQ_TYPE sfReq,
  _In_  PVOID pData,
  _In_  DWORD ul1,
  DWORD ul2


pfc [in]

Pointer to the HTTP_FILTER_CONTEXT data structure that is associated with the current, active HTTP session. Pass the filter context in this parameter.

sfReq [in]

Specifies the particular support function that is to be executed by the Forefront TMG Web filter, in this case, SF_REQ_SET_NEXT_READ_SIZE.

pData [in]

Unused in this support function.

ul1 [in]

Specifies the maximum size, in bytes, that will be read during the next read event.


Unused in this support function.

Return value

This callback function returns TRUE if the call is successful; otherwise, it returns FALSE. To obtain extended error information, call GetLastError.


This support function is meaningful only for filters that respond to raw-read notifications and that return the status code SF_STATUS_REQ_READ_NEXT from their entry-point function HttpFilterProc.

This support function is not relevant to the implementation of ISAPI in Forefront TMG. It is provided for compatibility with Internet Information Services (IIS). If you use it in a Forefront TMG Web filter, you should not assume that the number of bytes read during the subsequent read operation will not exceed the value set in the ul1 parameter.

For more information about the types of event notifications that are sent to Web filters, see Event Notifications.


Minimum supported client

None supported

Minimum supported server

Windows Server 2008 R2, Windows Server 2008 with SP2 (64-bit only)


Forefront Threat Management Gateway (TMG) 2010



See also




Build date: 7/12/2010