UDF 2.00 - OSTA - Optical Storage Technology Association

2.3.4.3 struct long_ad ICB
The Implementation Use bytes of the long_ad in all File Identifier Descriptors
shall be used to store the UDF Unique ID for the file and directory namespace.
UDF Unique ID
RBP Length Name Contents
0 2 Reserved bytes (= #00)
2 4 UDF Unique ID Uint32
Section 3.2.1Logical Volume Header Descriptor describes how UDF Unique ID
field in Implementation Use bytes of the long_ad in the File Identifier Descriptor
and the UniqueID field in the File Entry and Extended File Entry are set.
2.3.4.4 Uint16 LengthofImplementationUse
$ Shall specify the length of the ImplementationUse field.
? Shall specify the length of the ImplementationUse field. This field may be
ZERO, indicating that the ImplementationUse field has not been used.
When writing a File Identifier Descriptor to write-once media, to ensure that the
Descriptor Tag field of the next FID will never span a block boundary, if there are
less than 16 bytes remaining in the current block after the FID, the length of the
FID shall be increased (using the Implementation Use field) enough to prevent this.
The CRC length may be set to less than the size of the FID minus 16 (to not
include the Implementation Use area).
2.3.4.5 byte ImplementationUse
$ If the LengthofImplementationUse field is non ZERO then the first 32
bytes of this field shall be interpreted as specifying the implementation
identifier EntityID of the implementation which last modified the File
Identifier Descriptor.
? If the LengthofImplementationUse field is non ZERO then the first 32
bytes of this field shall be set to the implementation identifier EntityID of
the current implementation.
NOTE: For additional information on the proper handling of this field refer to the
section on Entity Identifier.
This field allows an implementation to identify which implementation last created
and/or modified a specific File Identifier Descriptor .
UDF 2.00 April 3, 1998
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