FsRtlInitPerStreamContext macro (ntifs.h)
The FsRtlInitPerStreamContext macro initializes a filter driver context structure.
Syntax
void FsRtlInitPerStreamContext(
_fc,
_owner,
_inst,
_cb
);
Parameters
_fc
Pointer to a caller-allocated FSRTL_PER_STREAM_CONTEXT structure to be used to maintain context information for a file stream. This structure can be used as is or embedded in a driver-defined per-stream context structure. Both structure types are commonly allocated by calling ExAllocatePoolWithTag.
_owner
Pointer to a caller-allocated variable that uniquely identifies the owner of the per-stream context structure. The format of this variable is filter driver − specific. Filter writers should choose a value that is both meaningful and convenient, such as the address of a driver object or device object. Callers must specify a non-NULL value for this parameter.
_inst
Pointer to a filter driver − allocated variable that can be used to distinguish among per-stream context structures created by the same filter driver. The format of this variable is filter driver − specific. Filter writers should choose a value that is both meaningful and convenient, such as the address of the stream context object for the file stream. (To get this address from a file object, use the FsRtlGetPerStreamContextPointer macro.) This parameter is optional and can be NULL.
_cb
Pointer to a callback routine that frees the per-stream context structure. Callers must specify a non-NULL value for this parameter. This routine and its parameters are defined as follows:
typedef
VOID (*PFREE_FUNCTION) (
IN PVOID Buffer
);
|
- Buffer
Pointer to the per-stream context structure to be freed. The FreeCallback routine typically casts this pointer to the appropriate structure pointer type and frees it by calling ExFreePool.
Return value
None
Remarks
A file system filter driver uses the FsRtlInitPerStreamContext macro to initialize a newly allocated per-stream context structure before associating it with a file stream. The initialized context structure can be passed as a parameter to FsRtlInsertPerStreamContext.
FsRtlInitPerStreamContext stores the address of the FreeCallback routine in the FreeCallback member of the FSRTL_PER_STREAM_CONTEXT structure.
The FreeCallback routine is called at IRQL <= APC_LEVEL. Usually, it is called at IRQL PASSIVE_LEVEL.
After the context structure has been associated with a file stream, it can be retrieved by calling FsRtlLookupPerStreamContext or removed by calling FsRtlRemovePerStreamContext.
For more information, see Tracking Per-Stream Context in a Legacy File System Filter Driver.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP; Update Rollup for Windows 2000 Service Pack 4 (SP4) |
| Target Platform | Desktop |
| Header | ntifs.h (include Ntifs.h) |
| IRQL | Any level |
See also
FsRtlGetPerStreamContextPointer