If an application does not handle extended names successfully,
examine the application for any the following:
o Does the application access and interpret the contents of
directory files directly? If so, the application may fail when
it encounters a directory that contains extended file names.
Recommendation: Modify the application to use the search
functions provided with the RMS or QIO interface, or with
LIBRTL routines such as LIB$FIND_FILE.
o Does the application attempt to parse or assume knowledge
of the syntax of a file specification? For example, the
application might search for a bracket ([) to locate the
beginning of a directory specification, or for a space
character to mark the end of a file specification.
Recommendation: The application should rely on RMS to
determine whether a file specification is legal rather than
pretesting the actual name. Use the NAM$L_NODE, NAM$L_DEV,
NAM$L_DIR, NAM$L_TYPE, and NAM$L_VER fields of the NAM block
or SYS$FILESCAN to retrieve this information.
o Does the application depend on the NAM$V_DIR_LVLS bits in the
NAM$L_FNB field to determine how many directory levels there
are in the current file specification? Because there are only
three bits in this field, it can only specify a maximum of
eight levels. Applications seldom use these bits; they are
mainly used by RMS when a NAM is specified as a related file
specification.
Recommendation: Starting with OpenVMS Version 7.2, there is
a new larger field available in both the NAM and the NAML
blocks, NAM$W_LONG_DIR_LEVELS. Use this field to locate the
correct number of directory levels.
o Does the application rely on the NAM$V_WILD_UFD and SFD1 -
SFD7 bits to determine where there are wildcard directories?
Because there are only eight of these bits they can only
report wildcards in the first eight directory levels.
Applications seldom use these bits; they are mainly used by
RMS when a NAM is specified as a related file specification.
Recommendation: Starting with OpenVMS Version 7.2, there is
a new field available in both the NAM and NAML block, NAML$W_
FIRST_WILD_DIR. Use this field to locate the highest directory
level where a wildcard is to be found.
o Does the application use the QIO interface to the file system
and specify or request a file name from QIO directly? The
QIO interface requires that an application specify explicitly
that it understands extended file names before it will accept
or return the names. In addition, the file name format for
extended file names is not identical between RMS and the QIO
interface. Additionally, some file names may be specified in
2-byte Unicode (UCS-2) characters. Your application must be
capable of dealing with 1 character that spans 2 bytes.
Recommendations: Most applications that use the QIO interface
also use RMS to parse file specifications and retrieve the
file and directory ID for the file. They then use these ID
values to access the file with the QIO interface. This method
of access continues to work with extended names. DIGITAL
recommends changing to this method to fix problem.
You can also obtain the name that the QIO system uses from
the NAML$L_FILESYS_NAME field of a NAML block, or use the new
system service (SYS$CVT_FILENAME) to convert between the RMS
and the QIO file name. In this case, you will also need to
provide an expanded FIB block to the QIO service to specify
that your application understands extended names, expand your
buffers to the maximum size, and prepare to deal with 2-byte
Unicode characters.