FsRtlLookupPerFileContext routine

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_opt_ PVOID OwnerId,
  _In_opt_ PVOID InstanceId
);

Parameters

PerFileContextPointer [in]

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.

OwnerId [in, optional]

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.

InstanceId [in, optional]

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

Target platform

Universal

Version

Available in Windows Vista and later versions of the Windows operating system.

Header

Ntifs.h (include FltKernel.h or Ntifs.h)

Library

NtosKrnl.lib

DLL

NtosKrnl.exe

IRQL

<= APC_LEVEL

See also

FSRTL_PER_FILE_CONTEXT
FsRtlGetPerFileContextPointer
FsRtlInsertPerFileContext
FsRtlRemovePerFileContext
Tracking Per-File Context in a Legacy File System Filter Driver

 

 

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