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[MS-FSA]: File System Algorithms

2 Algorithm Details

2.1 Object Store Details

2.1.4 Common Algorithms

2.1.4.1 Algorithm for Reporting a Change Notification for a Directory

2.1.4.2 Algorithm for Detecting If Open Files Exist Within a Directory

2.1.4.3 Algorithm for Determining If a Character Is a Wildcard

2.1.4.4 Algorithm for Determining if a FileName Is in an Expression

2.1.4.5 BlockAlign -- Macro to Round a Value Up to the Next Nearest Multiple of Another Value

2.1.4.6 BlockAlignTruncate -- Macro to Round a Value Down to the Next Nearest Multiple of Another Value

2.1.4.7 ClustersFromBytes -- Macro to Determine How Many Clusters a Given Number of Bytes Occupies

2.1.4.8 ClustersFromBytesTruncate -- Macro to Determine How Many Whole Clusters a Given Number of Bytes Occupies

2.1.4.9 SidLength -- Macro to Provide the Length of a SID

2.1.4.10 Algorithm for Determining If a Range Access Conflicts with Byte-Range Locks

2.1.4.11 Algorithm for Posting a USN Change for a File

2.1.4.12 Algorithm to Check for an Oplock Break

2.1.4.13 Algorithm to Recompute the State of a Shared Oplock

2.1.4.14 AccessCheck -- Algorithm to Perform a General Access Check

2.1.4.15 BuildRelativeName -- Algorithm for Building the Relative Path Name for a Link

2.1.4.16 FindAllFiles: Algorithm for Finding All Files Under a Directory

2.1.4.17 Algorithm for Noting That a File Has Been Modified

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2.1.4.11 Algorithm for Posting a USN Change for a File

The inputs for this algorithm are:

File: The file this change occurs on.
Reason: A 32-bit unsigned integer describing the change that occurred to the file, as specified in [MS-FSCC] section 2.3.42.
FileName: The pathname, relative to Volume.RootDirectory, of the file this change occurs on.

The algorithm MUST return at this point without taking any actions under any of the following conditions:

If the object store does not support USN change journals.
If File.Volume.IsUsnJournalActive is FALSE.
If Reason is zero.

Pseudocode for the algorithm is as follows:

Set FileNameLength to the length, in bytes, of FileName.
Set RecordLength to BlockAlign(FieldOffset(USN_RECORD.FileName) + FileNameLength, 8).
Set File.Volume.LastUsn to File.Volume.LastUsn + RecordLength.
Set File.Usn to File.Volume.LastUsn.

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