here - OSTA - Optical Storage Technology Association

y all OSTA UDF compliant implementations. The algorithm only applies when
reading an illegal FileIdentifier. The original FileIdentifier name on the media
should not be modified. This algorithm shall be applied by any implementation
that performs some form of FileIdentifier translation to meet operating system file
identifier restrictions.
All OSTA UDF compliant implementations shall support the UDF translation
algorithms, but may support additional algorithms. If multiple algorithms are
supported the user of the implementation shall be provided with a method to
select the UDF translation algorithms. It is recommended that the default
displayable algorithm be the UDF defined algorithm.
The primary goal of these algorithms is to produce a unique file name that meets
the specific operating system restrictions without having to scan the entire
directory in which the file resides.
C source code for the following algorithms may be found in the appendices of this
document.
NOTE: In the definition of the following algorithms anytime a d-character is
specified in quotes, the Unicode hexadecimal value will also be specified. The
following algorithms reference “CS0 Hex representation”, which corresponds to
using the Unicode values #0030 - #0039, and #0041 - #0046 to represent a value
in hex. In addition, the following algorithms reference “CS0 Base41
representation”, which corresponds to augmenting the CS0 Hex representation to
use #0047 - #005A, #0023, #005F, #007E, #002D and #0040 to represent digits
16-40.
The following algorithms could still result in name-collisions being reported to
the user of an implementation. However, the rationale includes the need for
efficient access to the contents of a directory and consistent name translations
across logical volume mounts and file system driver implementations, while
allowing the user to obtain access to any file within the directory (through
possibly renaming a file).
Some name transformations in section 4.2.2.1 result in two namespaces being
visible at once in a given directory – the space of primary names, those which are
physically recorded in a directory; and the space of generated names, those which
are derived from the primary names. This is distinct from transformations that
take an otherwise illegal name and render it into a legal form, the illegal name not
being considered part of the namespace of the directory on that system. For UDF
implementations using such transforms, the implementation should search a
directory in two passes: pass one should match against the primary namespace and
pass two should match against the generated namespace. A match in the primary
namespace should be preferred to a match against the generated namespace.
UDF 2.01
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