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//+-------------------------------------------------------------------------
//
// Copyright (C) 1992, Microsoft Corporation.
//
// File: fcbsup.h
//
// Contents: Declarations for DFS_FCB lookup support functions.
//
// History: 20 Feb 1993 Alanw Created
//
//--------------------------------------------------------------------------
#ifndef __FCBSUP_H__
#define __FCBSUP_H__
//
// In order to avoid modifying file objects which are passed
// through the DFS and used by other file systems, DFS_FCB records
// used by DFS are not directly attached to the file object
// through one of the fscontext fields, they are instead
// associated with the file object, and looked up as needed.
//
// A hashing mechanism is used for the lookup. Since the
// file object being looked up is just a pointer, the hash
// function is just a simple combination of a few of the low-
// order bits of the pointer's address.
//
//
// Declaration of the hash table. The hash table can be variably
// sized, with the hash table size being a parameter of the hash
// function.
//
typedef struct _FCB_HASH_TABLE {
//
// The type and size of this record (must be DSFS_NTC_FCB_HASH)
//
NODE_TYPE_CODE NodeTypeCode;
NODE_BYTE_SIZE NodeByteSize;
//
// Mask value for the hash function. The hash table size is
// assumed to be a power of two; the mask is the size - 1.
//
ULONG HashMask;
//
// A spinlock to protect access to the hash bucket lists.
//
KSPIN_LOCK HashListSpinLock;
//
// An array of list heads for the hash table chains. There
// are actually N of these where N is the hash table size.
//
LIST_ENTRY HashBuckets[1];
} FCB_HASH_TABLE, *PFCB_HASH_TABLE;
NTSTATUS
DfsInitFcbs(
IN ULONG n
);
PDFS_FCB
DfsLookupFcb(
IN PFILE_OBJECT pFile
);
VOID
DfsAttachFcb(
IN PFILE_OBJECT pFileObj,
IN PDFS_FCB pFCB
);
VOID
DfsDetachFcb(
IN PFILE_OBJECT pFileObj,
IN PDFS_FCB pFCB
);
#endif // __FCBSUP_H__
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