SECTION_OBJECT_POINTERS structure (wdm.h)

The SECTION_OBJECT_POINTERS structure, allocated by a file system or a redirector driver, is used by the memory manager and cache manager to store file-mapping and cache-related information for a file stream.

Syntax

typedef struct _SECTION_OBJECT_POINTERS {
  PVOID DataSectionObject;
  PVOID SharedCacheMap;
  PVOID ImageSectionObject;
} SECTION_OBJECT_POINTERS;

Members

DataSectionObject

Opaque pointer to a data section object (that is, a CONTROL_AREA structure) that is used to track state information for a data file stream. Memory manager sets this member when the operating system first caches the data stream. A NULL value indicates that the data stream is currently not in memory; this value, however, can change at any time.

SharedCacheMap

Opaque pointer to a cache map object (that is, a SHARED_CACHE_MAP structure) that is used to track views that are mapped to the data file stream. Cache manager sets this member when the operating system first caches the stream. A NULL value indicates that the data stream is currently not cached; this value, however, can change at any time.

ImageSectionObject

Opaque pointer to an image section object (that is, a CONTROL_AREA structure) that is used to track state information for an executable file stream. Memory manager sets this member whenever an executable image section is created for the stream. A NULL value indicates that the executable image is currently not in memory; this value, however, can change at any time.

Remarks

The SECTION_OBJECT_POINTERS structure links a file object to a file stream's section object. That is, through its members, the SECTION_OBJECT_POINTERS structure connects a particular file object to virtual memory control structures that keep track of the stream's contents when they are in memory, and allow the operating system to fetch those contents when they are not.

There is a one-to-one relationship between a SECTION_OBJECT_POINTERS structure and a file stream. Multiple file objects can be associated with a particular file stream, each representing an open instance of the stream. However, only one SECTION_OBJECT_POINTERS structure can be associated with a given stream. If there are multiple file objects for a stream, the SectionObjectPointer member for all file objects must point to the same SECTION_OBJECT_POINTERS structure (that is associated with the stream).

For the first file stream open request, the file system or the redirector driver must:

1. Allocate a SECTION_OBJECT_POINTERS structure from a nonpaged pool.

2. Initialize all members of the allocated SECTION_OBJECT_POINTERS structure to NULL.

3. Set the SectionObjectPointer member of the associate file object to point to the initialized SECTION_OBJECT_POINTERS structure.

For subsequent open requests to the same file stream, the file system or the redirector driver must set the SectionObjectPointer member of the associated file object to point to the previously allocated SECTION_OBJECT_POINTERS structure for the file stream.

A file is composed of one or more streams, depending on the file system. For more information, see File Streams, Stream Contexts, and Per-Stream Contexts.

Requirements

See also

CcInitializeCacheMap

DEVICE_OBJECT

FILE_OBJECT

FOBX

FSRTL_ADVANCED_FCB_HEADER

IoGetDeviceObjectPointer

MmFlushImageSection

ObDereferenceObject