नोट
इस पेज तक पहुँच के लिए प्रमाणन की आवश्यकता होती है. आप साइन इन करने या निर्देशिकाओं को बदलने का प्रयास कर सकते हैं.
इस पेज तक पहुँच के लिए प्रमाणन की आवश्यकता होती है. आप निर्देशिकाओं को बदलने का प्रयास कर सकते हैं.
Use the _Flt_CompletionContext_Outptr_ annotation when you declare the file system minifilter pre-operation callback function PFLT_PRE_OPERATION_CALLBACK. Place this annotation on the CompletionContext parameter. This annotation directs the code analysis tool to check that the CompletionContext is correct for the FLT_PREOP_CALLBACK_STATUS return value.
If a pre-operation callback function (PFLT_PRE_OPERATION_CALLBACK) returns FLT_PREOP_SUCCESS_WITH_CALLBACK or FLT_PREOP_SYNCHRONIZE the CompletionContext might or might not be NULL. For any other FLT_PREOP_CALLBACK_STATUS return value the CompletionContext must be NULL. The CompletionContext is filter-defined state that is passed from the filter’s pre-operation callback to the corresponding post-operation callback function (PFLT_POST_OPERATION_CALLBACK). The post-operation callback is only called if the filter returned FLT_PREOP_SUCCESS_WITH_CALLBACK or FLT_PREOP_SYNCHRONIZE from its pre-operation callback function. If the filter doesn’t pass any state from its pre-operation callback function to its post-operation callback function the CompletionContext is NULL, and therefore CompletionContext in its post-operation callback function will be NULL. Each individual filter decides whether to return state in CompletionContext from a pre-operation callback function, so it is up to each individual filter to know whether or not it should look at CompletionContext in its post-operation callback function.
Example
The following example shows the function prototype for a PFLT_PRE_OPERATION_CALLBACK function called SwapPreReadBuffers. The CompletionContext parameter receives the context that will be passed to the post-operation callback function and it is declared with _Flt_CompletionContext_Outptr_ annotation.
FLT_PREOP_CALLBACK_STATUS
SwapPreReadBuffers(
_Inout_ PFLT_CALLBACK_DATA Data,
_In_ PCFLT_RELATED_OBJECTS FltObjects,
_Flt_CompletionContext_Outptr_ PVOID *CompletionContext
);
The _Flt_CompletionContext_Outptr_ annotation is defined in specstrings.h. Using the annotation can add valuable error checking without adding overhead or complexity to your code.