113 lines
7.9 KiB
HTML
113 lines
7.9 KiB
HTML
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<!DOCTYPE html
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<meta name="DC.Title" content="Programming interfaces UDF" />
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<meta name="abstract" content="You can create files or read files on UDF media by using either the Hierarchical File System (HFS) application programming interface (API) or the integrated file system programming interface. There are things specific to the i5/OS implementation of the UDF media format that application developers need to know." />
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<title>Programming interfaces UDF</title>
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</head>
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<body id="rzam4udfproginterfces"><a name="rzam4udfproginterfces"><!-- --></a>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Programming interfaces UDF</h1>
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<div><p>You can create files or read files on UDF media by using either
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the Hierarchical File System (HFS) application programming interface (API)
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or the integrated file system programming interface. There are things specific
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to the i5/OS™ implementation
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of the UDF media format that application developers need to know.</p>
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<dl><dt class="dlterm">National Language Support</dt>
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<dd>The integrated file system interfaces assume that the CCSID (coded character
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set identifier) represents the path in effect for the job. The system then
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converts the path from the job CCSID to an internally used CCSID. The HFS
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API interface makes no assumption about the CCSID of the path; therefore,
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the system performs no character set conversion on the path. This could produce
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undesirable side effects if an application used the two API sets interchangably
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or if the application changed from using one API set to the other.</dd>
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<dd class="ddexpand">You should not create files through HFS and then try to read them by using
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the integrated file system APIs. Depending on the characters that are used
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in the path name, a File not found error could result. This type of problem
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can be avoided if the application uses only invariant characters (for example,
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A-Z 0-9 + = % & ( ) , _ . : ;) for path names. Invariant characters are
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graphic characters that map to the same code point in all character sets. </dd>
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<dd class="ddexpand">Since UDF is an industry-standard media format, NLS compliance could be
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important because of the increased opportunity for media interchange across
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different operating system platforms. This causes the system to limit HFS
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interfaces to UDF media. Additionally, the system uses invariant characters
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to reduce the chance of media interchange problems that are related to file
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names. Assume that an HFS-based application absolutely requires the use of
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variant characters. You can use the Change Optical Attributes (CHGOPTA) CL
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command to allow variant characters through the HFS interface by specifying
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CHGOPTA ALWVRNT(*YES). After the system allows variant characters through
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HFS, there is no guarantee that path names will interchange correctly if accessed
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from another operating system. There is also no guarantee that path names
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will be consistent between the HFS and integrated file system interfaces.</dd>
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</dl>
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<dl><dt class="dlterm">Held optical files</dt>
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<dd>The system does not create held files for UDF media. When a file fails
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to close on UDF, the system signals an error to the application. This error
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then closes the file without writing the data to optical disk. The application
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must rewrite the file (open, write, close) to ensure that the data is on optical
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disk. The exception to this is if the application did a <span class="apiname">Force Buffered
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Data</span> or <span class="apiname">fsync()</span> API (QHFFRCSF) prior to the close
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operation. </dd>
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<dd class="ddexpand">These APIs will force the writing of the data to the optical disk.</dd>
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</dl>
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<dl><dt class="dlterm">File sharing</dt>
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<dd>Multiple jobs or threads can share files for read, but writers are always
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exclusive. If one job or thread is writing to a file on UDF, you cannot use
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any other jobs or threads to open that file. </dd>
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<dd class="ddexpand">Therefore, when using integrated file system open() or open64() APIs,
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the sharing modes O_SHARE_RDONLY, O_SHARE_WRONLY, and O_SHARE_RDWR do not
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provide the requested level of sharing when the access mode is O_RDWR or O_WRONLY.
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When the access method is O_RDWR or O_WRONLY, the resulting sharing mode will
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be equivalent to O_SHARE_NONE.</dd>
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<dd class="ddexpand">When using the HFS Open Stream File API, the lock modes deny none, deny
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write, and deny read do not provide the requested level of sharing when the
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access mode is write only or read/write. When the access method is write only
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or read/write, the resulting lock mode will be deny read/write.</dd>
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</dl>
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<dl><dt class="dlterm">Mixed-case file name</dt>
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<dd>When created through the integrated file system interfaces, files and
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directories created on UDF volumes will preserve the case specified on the
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create. For example, if file Abc is specified on the <span class="apiname">open()</span> API,
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Abc will be created on the media in the mixed-case form. Even though the system
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preserves file case, file searches are case-insensitive meaning that the system
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can read the file that uses any case such as ABC or abc.</dd>
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<dd class="ddexpand">When created through the HFS or save and restore interfaces, the system
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stores files and directories that are created on the UDF volumes in uppercase.
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For example, if you specify file Abc on the Open Stream File API, the system
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creates ABC on the media. Again, file searches are case-insensitive so you
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can specify any case to read the file.</dd>
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<dd class="ddexpand">File searches on UDF volumes created by i5/OS are case-insensitive. For UDF media
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created or updated by another operating system platform, a case sensitive
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search is performed. If no case-sensitive match is found, a case-insensitve
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match is returned if it exists. If multiple case-insensitive matches exist
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on the UDF volume, an error is returned indicating that ambiguous names exist
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on the media.</dd>
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</dl>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzam4universaldiskformat.htm" title="UDF (Universal Disk Format) is the OSTA (Optical Storage Technology Association) supported subset of ISO/IEC 13346.">Universal disk format</a></div>
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</div>
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</div>
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<img src="./deltaend.gif" alt="End of change" /></body>
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</html> |