Native Files

Files on the UOSFS are tracked via a file header, which contains a pointer to an allocation cluster chain. The header holds five extent pointers so that small files don't use extra space for allocation clusters. Further, the number of allocation clusters required can be reduced by increasing the file's cluster size to some multiple of the store's cluster size.

The native file header is a structure matching the following definition:

type TData_Stream = packed record

Name : int64 ;

Pointer : int64 ;

end ;

TUOS_File_Header = packed record

Name : longint ;

Size : int64 ;

EOF : int64 ;

Uncompressed_Size : int64 ;

Clustersize : cardinal ;

Record_Size : cardinal ;

// Dates...

Creation : int64 ;

Last_Modified : int64 ;

Last_Backup : int64 ;

Last_Access : int64 ;

Expiration : int64 ;

Creator : cardinal ;

Owner : cardinal ;

ACL : int64 ;

Flags : int64 ;

Version_Limit : longint ;

Extension : int64 ;

Streams : array[ 0..4 ] of TData_Stream ;

Data_Stream : int64 ;

Clusters : array[ 0..4 ] of int64 ;

Parent : int64 ;

File_System : int64 ;

end ;

The contents of the file header are described in the following table:

Header item	Description
Name	File name index
Size	File size on disk
EOF	Logical end of file offset
Uncompressed_Size	The size of the file when uncompressed
Record_Size	Size for record in record-oriented files
Creation	Creation date
Last_Modified	Date last modified
Last_Backup	Date last backed up
Last_Access	Date last accessed (read or write)
Expiration	Date of file expiration
Creator	ID of the user who created the file
Owner	ID of the user who owns the file
ACL	Pointer to Access Control List
Flags	A set of bit flags. General: FAF_DSM_MASK = Mask for data security mode FAF_PLACED = Placed at a specific location FAF_CONTIGUOUS = Contiguous file data FAF_DELETED = Deleted file FAF_READONLY = Read-only data FAF_LINK = Link to another file FAF_SYSTEM = System file FAF_HIDDEN = Hidden file FAF_DIRECTORY = Directory file FAF_PERMANENT = Non-deletable file FAF_COPYING = In the process of copying Protections: FAF_PROTECTION_OWNER_READ - Owner can read FAF_PROTECTION_OWNER_WRITE - Owner can write FAF_PROTECTION_OWNER_DELETE - Owner can delete FAF_PROTECTION_OWNER_EXECUTE - Owner can execute FAF_PROTECTION_GROUP_READ - Group members can read FAF_PROTECTION_GROUP_WRITE - Group members can write FAF_PROTECTION_GROUP_DELETE - Group members can delete FAF_PROTECTION_GROUP_EXECUTE - Group members can execute FAF_PROTECTION_SYSTEM_READ - System accounts can read FAF_PROTECTION_SYSTEM_WRITE - System accounts can write FAF_PROTECTION_SYSTEM_DELETE - System accounts can delete FAF_PROTECTION_SYSTEM_EXECUTE - System accounts can execute. FAF_PROTECTION_WORLD_READ - Everyone can read FAF_PROTECTION_WORLD_WRITE - Everyone can write FAF_PROTECTION_WORLD_DELETE - Everyone can delete FAF_PROTECTION_WORLD_EXECUTE - Everyone can execute
Version_Limit	Maximum version limit (0=no limit)
Extension	Pointer to header extension (reserved)
Streams	Meta-data stream pointers and names
Data_Stream	Data stream pointer
Clusters	Pointers to first 5 extents
Parent	Parent directory pointer
File_System	Parent directory offset

Data Streams

Files contain data. UOS file can contain meta-data in addition to data. Some meta data is in the file header, but UOSFS allows additional information to be stored in the file, but kept separate from the file's actual data. This is accomplished via "streams". A file can have any number of data streams. Data stream 0 is unnamed and reserved for the file's actual data. All other data streams can be assigned names that indicate what data is being stored in each stream.

Contiguous Files

Contiguous files (FAF_CONTIGUOUS flag) are stored in contiguous clusters. Therefore, allocation chains are not required. Instead, the first extent in Clusters points to the first cluster of the contiguous data.