FsRtlLookupPerFileContext function (ntifs.h)
The FsRtlLookupPerFileContext routine returns a pointer to a FSRTL_PER_FILE_CONTEXT object that is associated with a specified file.
Syntax
PFSRTL_PER_FILE_CONTEXT FsRtlLookupPerFileContext(
[in] PVOID *PerFileContextPointer,
[in, optional] PVOID OwnerId,
[in, optional] PVOID InstanceId
);
Parameters
[in] PerFileContextPointer
A pointer to an opaque pointer that is used by the file system runtime library (FSRTL) package to track file contexts. To retrieve this pointer from a file object, use the FsRtlGetPerFileContextPointer macro.
[in, optional] OwnerId
A pointer to a filter driver-allocated variable that uniquely identifies the owner of the per-file context structure. The format of this variable is filter driver-specific. This parameter is optional, but must be non-NULL if InstanceId is non-NULL.
[in, optional] InstanceId
A pointer to a filter driver-allocated variable that can be used to distinguish among per-file context structures that are created by the same filter driver. The format of this variable is filter driver-specific. This parameter is optional.
Return value
A pointer to the first FSRTL_PER_FILE_CONTEXT structure that matches the OwnerId and InstanceId, if specified, or NULL if no match is found or the file system does not support per-file contexts.
Remarks
By not specifying OwnerID and InstanceId, a filter driver can search for the first context that is associated with a file.
If the file system does not support per-file context objects, NULL is returned. Use the FsRtlSupportsPerFileContexts macro to determine whether a file system supports per-file context objects.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows Vista |
| Target Platform | Universal |
| Header | ntifs.h (include FltKernel.h, Ntifs.h) |
| Library | NtosKrnl.lib |
| DLL | NtosKrnl.exe |
| IRQL | <= APC_LEVEL |
See also
Tracking Per-File Context in a Legacy File System Filter Driver