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<html>
<head><title>
HDF5/H5Z Draft API Specification
</title></head>
<body>
<hr>
<center>
<a href="RM_H5Front.html">HDF5 Reference Manual</a>
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H5Z
<a href="Glossary.html">Glossary</a>
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<hr>
<center>
<h1>H5Z: Compression Interface</h1>
</center>
<h2>Compression API Functions</h2>
This function enable the user to configure a new compression
method for the local environment.
<table border=0>
<tr><td valign=top>
<ul>
<li><a href="#Compression-Register">H5Zregister</a>
</ul>
</td><td> </td><td valign=top>
<ul>
</ul>
</td></tr>
</table>
<p>
HDF5 supports compression of raw data by compression methods
built into the library or defined by an application.
A compression method is associated with a dataset when the dataset is
created and is applied independently to each storage chunk of the dataset.
The dataset must use the <code>H5D_CHUNKED</code> storage layout.
<p>
The HDF5 library does not support compression for contiguous datasets
because of the difficulty of implementing random access for partial I/O.
Compact dataset compression is not supported because it would not produce
significant results.
<p>
See <a href="Compression.html"><cite>Compression</cite></a> in the
<cite>HDF5 User's Guide</cite> for further information.
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Compression-Register">H5Zregister</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Zregister</code>(<em>H5Z_method_t</em> <code>method</code>,
<em>const char *</em><code>name</code>,
<em>H5Z_func_t</em><code>cfunc</code>,
<em>H5Z_func_t</em> <code>ufunc</code>
)
<dt><strong>Purpose:</strong>
<dd> Registers new compression and uncompression functions for a
method specified by a method number.
<dt><strong>Description:</strong>
<dd><code>H5Zregister</code> registers new compression and uncompression
functions for a method specified by a method number, <code>method</code>.
<code>name</code> is used for debugging and may be the null pointer.
Either or both of <code>cfunc</code> (the compression function) and
<code>ufunc</code> (the uncompression method) may be null pointers.
<p>
The statistics associated with a method number are not reset
by this function; they accumulate over the life of the library.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>H5Z_method_t</em> <code>method</code>
<dd>Number specifying compression method.
<dt><em>const char *</em><code>name</code>
<dd>Name associated with the method number.
<dt><em>H5Z_func_t</em> <code>cfunc</code>
<dd>Compression method.
<dt><em>H5Z_func_t</em> <code>ufunc</code>
<dd>Uncompression method.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns SUCCEED (0) if successful;
otherwise FAIL (-1).
</dl>
<hr>
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H5Z
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<address>
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
<br>
Last modified: 14 July 1998
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