FltSupportsFileContextsEx function (fltkernel.h)

Article
10/21/2021

The FltSupportsFileContextsEx routine determines whether the file system or the filter manager support file contexts for a given file.

Syntax

BOOLEAN FLTAPI FltSupportsFileContextsEx(
  [in]           PFILE_OBJECT  FileObject,
  [in, optional] PFLT_INSTANCE Instance
);

Parameters

[in] FileObject

Pointer to the file object that represents the file whose file context support is being queried. This parameter is required and cannot be NULL.

[in, optional] Instance

Opaque instance pointer for the caller. This parameter is optional and can be NULL. For more information about this parameter, see the Remarks section of this page.

Return value

FltSupportsFileContextsEx returns TRUE if the file system or filter manager supports file contexts for the file; FALSE otherwise.

Remarks

Minifilter drivers can call the FltSupportsFileContextsEx routine to determine whether the underlying file system or the filter manager supports file contexts for the file represented by FileObject without having to allocate a context and attempt to set it. If a context type isn't supported on a file, then the minifilter cannot attach a context to that file.

For file systems (such as FAT) that support only a single data stream per file, file contexts are equivalent to stream contexts. Such file systems usually support stream contexts but do not support file contexts. Instead, the filter manager provides file context support, using the file system's existing support for stream contexts. For minifilter instances attached to these file systems, FltSupportsFileContexts returns FALSE, while FltSupportsFileContextsEx returns TRUE (when a valid non-NULL value is passed for the Instance parameter).

If a non-NULL value is supplied for the Instance parameter, FltSupportsFileContextsEx returns TRUE if the file system or the filter manager supports file contexts for the file; FALSE otherwise.

If the Instance parameter is NULL, FltSupportsFileContextsEx returns TRUE only if the file system supports file contexts for the file. Otherwise, it returns FALSE, even if the filter manager supports file contexts for the file.

Note that a file system might support file contexts for some types of files but not for others. For example, NTFS and FAT do not support file contexts for paging files.

For more information about contexts, see About minifilter contexts.

Requirements

Requirement	Value
Minimum supported client	This routine is available on Windows Vista and later.
Target Platform	Universal
Header	fltkernel.h (include Fltkernel.h)
Library	FltMgr.lib
DLL	Fltmgr.sys
IRQL	<= APC_LEVEL