IHttpRequest::GetHeaderChanges Method

Retrieves the changes to the server headers for the current request.

Syntax

virtual HRESULT GetHeaderChanges(  
   IN DWORD dwOldChangeNumber,  
   OUT DWORD* pdwNewChangeNumber,  
   IN OUT PCSTR knownHeaderSnapshot [HttpHeaderRequestMaximum],  
   IN OUT DWORD* pdwUnknownHeaderSnapShot,  
   IN OUT PCSTR** ppUnknownHeaderNameSnapShot,  
   IN OUT PCSTR** ppUnknownHeaderValueSnapShot,  
   __out_ecount(HttpHeaderRequestMaximum+1) DWORD diffedKnownHeaderIndices [HttpHeaderRequestMaximum+1],  
   OUT DWORD* pdwDiffedUnknownHeaders,  
   OUT DWORD** ppDiffedUnknownHeaderIndices  
) = 0;  

Parameters

dwOldChangeNumber
[IN] A DWORD that contains the old change number.

pdwNewChangeNumber
[OUT] A pointer to a DWORD that contains the new change number.

knownHeaderSnapshot
[IN][OUT] A pointer to a string array that contains the snapshot of all known headers. (The array will contain the new headers when calling, and it will contain the old headers when returning.)

pdwUnknownHeaderSnapShot
[IN][OUT] A pointer to a DWORD that contains the number of unknown headers in the snapshot.

ppUnknownHeaderNameSnapShot
[IN][OUT] A pointer to the address of a string array that contains the names of all unknown headers. (The array will contain the new headers when calling, and it will contain the old headers when returning.)

ppUnknownHeaderValueSnapShot
[IN][OUT] A pointer to the address of a string array that contains a list of all header values in the snapshot.

diffedKnownHeaderIndices
[OUT] An array of DWORD values, terminated by a –1 value, that contain the indexes of headers that have changed in the list of known headers.

pdwDiffedUnknownHeaders
[OUT] A pointer to a DWORD value that contains number of unknown headers that have changed.

ppDiffedUnknownHeaderIndices
[OUT] A pointer to the address of an array of DWORD values, terminated by a –1 value, that contain the indexes of headers that have changed in the list of unknown headers.

Return Value

An HRESULT. Possible values include, but are not limited to, those in the following table.

Value	Description
S_OK	Indicates that the operation was successful.
ERROR_NOT_ENOUGH_MEMORY	Indicates that there is insufficient memory to perform the operation.

Remarks

IIS uses the GetHeaderChanges method to test for changes to the HTTP headers since the last time the headers were examined.

Note

IIS uses the GetHeaderChanges method to internally synchronize the headers between calls to native and managed code. You should not use the GetHeaderChanges method when you create an HTTP module.

Requirements

Type	Description
Client	- IIS 7.0 on Windows Vista - IIS 7.5 on Windows 7 - IIS 8.0 on Windows 8 - IIS 10.0 on Windows 10
Server	- IIS 7.0 on Windows Server 2008 - IIS 7.5 on Windows Server 2008 R2 - IIS 8.0 on Windows Server 2012 - IIS 8.5 on Windows Server 2012 R2 - IIS 10.0 on Windows Server 2016
Product	- IIS 7.0, IIS 7.5, IIS 8.0, IIS 8.5, IIS 10.0 - IIS Express 7.5, IIS Express 8.0, IIS Express 10.0
Header	Httpserv.h

See Also

IHttpRequest Interface
IHttpRequest::GetHeader Method
IHttpResponse::GetHeader Method
IHttpResponse::GetHeaderChanges Method