FltSetInstanceContext function

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NTSTATUS FLTAPI FltSetInstanceContext(
  PFLT_INSTANCE             Instance,
  FLT_SET_CONTEXT_OPERATION Operation,
  PFLT_CONTEXT              NewContext,
  PFLT_CONTEXT              *OldContext
);

Parameters

Instance

Opaque instance pointer for the instance.

Operation

Flag specifying details of the operation to be performed. This parameter must be one of the following:

FLT_SET_CONTEXT_REPLACE_IF_EXISTS

If a context is already set for this Instance, replace it with NewContext. Otherwise, set NewContext as the context for Instance.

FLT_SET_CONTEXT_KEEP_IF_EXISTS

If a context is already set for this Instance, return STATUS_FLT_CONTEXT_ALREADY_DEFINED. Otherwise, set NewContext as the context for Instance.

NewContext

Pointer to the new context to be set for the instance. This parameter is required and cannot be NULL.

OldContext

Pointer to a caller-allocated variable that receives the address of the existing instance context, if one is already set. This parameter is optional and can be NULL. (For more information about this parameter, see the following Remarks section.)

Return value

FltSetInstanceContext returns STATUS_SUCCESS or an appropriate NTSTATUS value such as one of the following:

Remarks

A minifilter driver calls FltSetInstanceContext to attach an instance context to a caller-owned minifilter driver instance or to remove or replace an existing instance context. A minifilter driver can attach only one context to an instance.

A successful call to FltSetInstanceContext increments the reference count on NewContext. If FltSetInstanceContext fails, the reference count remains unchanged. In either case, the filter calling FltSetInstanceContext must call FltReleaseContext to decrement the NewContext object. If FltSetInstanceContext fails and if the OldContext parameter is not NULL and does not point to NULL_CONTEXT then OldContext is a referenced pointer to the context currently associated with the transaction. The filter calling FltSetInstanceContext must call FltReleaseContext for OldContext as well.

Note that the OldContext pointer returned by FltSetInstanceContext must also be released by calling FltReleaseContext when it is no longer needed. For more information, see Setting Contexts and Releasing Contexts.

To get an instance context, call FltGetInstanceContext.

To allocate a new context, call FltAllocateContext.

To delete an instance context, call FltDeleteInstanceContext or FltDeleteContext.

For more information about context reference counting, see Referencing Contexts.

Requirements