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Purpose:
Add H5Zget_filter_info and h5zget_filter_info_f.
Other minor edits.
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HTML
644 lines
25 KiB
HTML
<html>
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<head>
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<title>
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HDF5/H5Z API Specification
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</title>
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<!-- #BeginLibraryItem "/ed_libs/styles_RM.lbi" -->
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<link href="ed_styles/RMelect.css" rel="stylesheet" type="text/css">
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<!-- #BeginLibraryItem "/ed_libs/NavBar_RM.lbi" --><hr>
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<center>
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<table border=0 width=98%>
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<tr><td valign=top align=left>
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<a href="index.html">HDF5 documents and links</a> <br>
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<a href="H5.intro.html">Introduction to HDF5</a> <br>
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<a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User Guide</a> <br>
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<!--
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<a href="Glossary.html">Glossary</a><br>
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-->
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</td>
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<td valign=top align=right>
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And in this document, the
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<a href="RM_H5Front.html">HDF5 Reference Manual</a>
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<br>
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<a href="RM_H5.html">H5</a>
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<a href="RM_H5A.html">H5A</a>
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<a href="RM_H5D.html">H5D</a>
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<a href="RM_H5E.html">H5E</a>
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<a href="RM_H5F.html">H5F</a>
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<a href="RM_H5G.html">H5G</a>
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<a href="RM_H5I.html">H5I</a>
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<a href="RM_H5P.html">H5P</a>
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<br>
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<a href="RM_H5R.html">H5R</a>
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<a href="RM_H5S.html">H5S</a>
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<a href="RM_H5T.html">H5T</a>
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<a href="RM_H5Z.html">H5Z</a>
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<a href="Tools.html">Tools</a>
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<a href="PredefDTypes.html">Datatypes</a>
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</td></tr>
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</table>
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</center>
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<hr><!-- #EndLibraryItem --><center>
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<h1>H5Z: Filter and Compression Interface</h1>
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</center>
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<h2>Filter and Compression API Functions</h2>
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These functions enable the user to configure new filters
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for the local environment.
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<table border=0 width=80%>
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<tr><td valign=top width="30%">
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<ul>
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<li><a href="#Compression-FilterAvail">H5Zfilter_avail</a><br>
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<li><a href="#Compression-GetFilterInfo">H5Zget_filter_info</a>
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</ul>
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</td><td> </td><td valign=top width="30%">
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<ul>
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<li><a href="#Compression-Register">H5Zregister</a>
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</ul>
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</td><td> </td><td valign=top width="30%">
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<ul>
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<li><a href="#Compression-Unregister">H5Zunregister</a>
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</ul>
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</td></tr>
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</table>
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<br>
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<strong>The FORTRAN90 Interfaces:</strong>
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<br>
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In general, each FORTRAN90 subroutine performs exactly the same task
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as the corresponding C function.
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<br>
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<table border=0 width=80%>
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<tr><td valign=top width="30%">
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<ul>
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<li><a href="#Compression-FilterAvail">h5zfilter_avail_f</a>
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</ul>
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</td><td> </td><td valign=top width="30%">
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<ul>
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<!--<li><a href="#Compression-Register">h5zregister_f</a><br> -->
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<li><a href="#Compression-GetFilterInfo">h5zget_filter_info_f</a>
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</ul>
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</td><td> </td><td valign=top width="30%">
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<ul>
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<li><a href="#Compression-Unregister">h5zunregister_f</a>
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</ul>
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</td></tr>
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</table>
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<p>
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HDF5 supports a filter pipeline that provides the capability for standard
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and customized raw data processing during I/O operations.
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HDF5 is distributed with a small set of standard filters such as
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compression (gzip, SZIP, and a shuffling algorithm) and
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error checking (Fletcher32 checksum).
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For further flexibility, the library allows a
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user application to extend the pipeline through the
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creation and registration of customized filters.
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<p>
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The flexibility of the filter pipeline implementation enables the
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definition of additional filters by a user application.
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A filter
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<ul>
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<li>is associated with a dataset when the dataset is created,
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<li>can be used only with chunked data
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(i.e., datasets stored in the <code>H5D_CHUNKED</code>
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storage layout), and
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<li>is applied independently to each chunk of the dataset.
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</ul>
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<p>
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The HDF5 library does not support filters for contiguous datasets
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because of the difficulty of implementing random access for partial I/O.
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Compact dataset filters are not supported because it would not produce
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significant results.
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<p>
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Filter identifiers for the filters distributed with the HDF5 Library
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are as follows:
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<table align=center border=0>
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<tr valign=top align=left>
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<td>
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<code>H5Z_FILTER_DEFLATE</code></td><td>The gzip compression,
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or deflation, filter
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</td></tr><tr><td>
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<code>H5Z_FILTER_SZIP</code></td><td>The SZIP compression filter
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</td></tr><tr><td>
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<code>H5Z_FILTER_SHUFFLE</code></td><td>The shuffle algorithm filter
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</td></tr><tr><td>
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<code>H5Z_FILTER_FLETCHER32 </code></td><td>The Fletcher32 checksum,
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or error checking, filter
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</td></tr>
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</table>
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Custom filters that have been registered with the library will have
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additional unique identifiers.
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<p>
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See <a href="Datasets.html"><cite>The Dataset Interface (H5D)</cite></a>
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in the <cite>HDF5 User's Guide</cite> for further information regarding
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data compression.
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<!-- NEW PAGE -->
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<!-- NEW PAGE -->
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<!-- HEADER RIGHT "H5Zfilter_avail" -->
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<hr>
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<dl>
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<dt><strong>Name:</strong> <a name="Compression-FilterAvail">H5Zfilter_avail</a>
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<dt><strong>Signature:</strong>
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<dd><em>herr_t</em> <code>H5Zfilter_avail</code>(<em>H5Z_filter_t</em> <code>filter</code>)
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<dt><strong>Purpose:</strong>
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<dd>Determines whether a filter is available.
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<dt><strong>Description:</strong>
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<dd><code>H5Zfilter_avail</code> determines whether the filter
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specified in <code>filter</code> is available to the application.
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<dt><strong>Parameters:</strong>
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<ul><table>
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<tr>
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<td valign="top"><em>H5Z_filter_t</em> <code>filter </code></td>
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<td valign="top">IN: Filter identifier.
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See the introduction to this section of the reference manual
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for a list of valid filter identifiers.</td></tr>
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</table></ul>
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<dt><strong>Returns:</strong>
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<dd>Returns a non-negative value if successful;
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otherwise returns a negative value.
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<dt><strong>Fortran90 Interface:</strong> h5zfilter_avail_f
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<dd>
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<pre>
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SUBROUTINE h5zfilter_avail_f(filter, status, hdferr)
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IMPLICIT NONE
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INTEGER, INTENT(IN) :: filter ! Filter
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! Valid values are:
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! H5Z_FILTER_DEFLATE_F
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! H5Z_FILTER_SHUFFLE_F
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! H5Z_FILTER_FLETCHER32_F
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! H5Z_FILTER_SZIP_F
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LOGICAL, INTENT(OUT) :: status ! Flag indicating whether
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! filter is available:
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! .TRUE.
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! .FALSE.
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END SUBROUTINE h5zfilter_avail_f
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</pre>
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<!--<dt><strong>Non-C API(s):</strong>
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<dd>
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<img src="Graphics/Java.gif">
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<img src="Graphics/C++.gif">
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-->
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</dl>
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<!-- NEW PAGE -->
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<!-- HEADER RIGHT "H5Zget_filter_info" -->
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<hr>
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<dl>
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<dt><strong>Name:</strong> <a name="Compression-GetFilterInfo">H5Zget_filter_info</a>
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<dt><strong>Signature:</strong>
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<dd><em>herr_t</em>
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<code>H5Zget_filter_info</code>(
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<em>H5Z_filter_t</em> <code>filter</code>,
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<em>unsigned int *</em><code>filter_config_flags</code>
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)
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<dt><strong>Purpose:</strong>
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<dd>Retrieves information about a filter.
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<dt><strong>Description:</strong>
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<dd>
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<code>H5Zget_filter_info</code> retrieves information about a filter.
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At present, this means that the function retrieves a
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filter's configuration flags, indicating whether the filter is
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configured to decode data, to encode data, neither, or both.
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<p>
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If <code>filter_config_flags</code> is not set to <small>NULL</small>
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prior to the function call, the returned parameter contains a
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bit field specifying the available filter configuration.
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The configuration flag values can then be determined through
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a series of bitwise <small>AND</small> operations, as described below.
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<p>
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Valid filter configuration flags include the following:
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<table>
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<tr><td><code> </code></td>
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<td><code>H5Z_FILTER_CONFIG_ENCODE_ENABLED</code></td>
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<td>Encoding is enabled for this filter
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</td></tr>
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<tr><td> </td>
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<td><code>H5Z_FILTER_CONFIG_DECODE_ENABLED</code> </td>
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<td>Decoding is enabled for this filter
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</td></tr>
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<tr><td> </td>
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<td colspan="2" align="right"><small>(These flags
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are defined in the HDF5 Library source code file
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<code>H5Zpublic.h</code>.)</small>
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</td></tr>
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</table>
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A bitwise <small>AND</small> of the returned
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<code>filter_config_flags</code> and a valid
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filter configuration flag will reveal whether
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the related configuration option is available.
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For example, if the value of
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<br>
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<code>
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H5Z_FILTER_CONFIG_ENCODE_ENABLED
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&
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filter_config_flags</code>
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<br>
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is true, i.e., greater than <code>0</code> (zero),
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the queried filter is configured to encode data;
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if the value is <code>FALSE</code>,
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i.e., equal to <code>0</code> (zero),
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the filter is not so configured.
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<p>
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If a filter is not encode-enabled, the corresponding
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<code>H5Pset_*</code> function will return an error if the
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filter is added to a dataset creation property list (which is
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required if the filter is to be used to encode that dataset).
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For example, if the <code>H5Z_FILTER_CONFIG_ENCODE_ENABLED</code>
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flag is not returned for the SZIP filter,
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<code>H5Z_FILTER_SZIP</code>, a call to <code>H5Pset_szip</code>
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will fail.
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<p>
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If a filter is not decode-enabled, the application will not be
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able to read an existing file encoded with that filter.
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<p>
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This function should be called, and the returned
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<code>filter_config_flags</code> analyzed, before calling
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any other function, such as <code>H5Pset_szip</code>,
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that might require a particular filter configuration.
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<dt><strong>Parameters:</strong>
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<dl>
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<dt><em>H5Z_filter_t</em> <code>filter</code>
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<dd>IN: Identifier of the filter to query.
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See the introduction to this section of the reference manual
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for a list of valid filter identifiers.
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<dt><em>unsigned int *</em><code>filter_config_flags</code>
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<dd>OUT: A bit field encoding the returned filter information
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</dl>
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<dt><strong>Returns:</strong>
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<dd>Returns a non-negative value on success,
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a negative value on failure.
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<dt><strong>Fortran90 Interface:</strong>
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<dd>
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<pre>
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SUBROUTINE h5zget_filter_info_f(filter, config_flags, hdferr)
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IMPLICIT NONE
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INTEGER, INTENT(IN) :: filter ! Filter, may be one of the
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! following:
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! H5Z_FILTER_DEFLATE_F
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! H5Z_FILTER_SHUFFLE_F
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! H5Z_FILTER_FLETCHER32_F
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! H5Z_FILTER_SZIP_F
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INTEGER, INTENT(OUT) :: config_flags ! Bit field indicating whether
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! a filter's encoder and/or
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! decoder are available
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INTEGER, INTENT(OUT) :: hdferr ! Error code
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END SUBROUTINE h5zfilter_avail_f
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</pre>
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<!--<dt><strong>Non-C API(s):</strong>
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<dd>
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<img src="Graphics/Java.gif">
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<img src="Graphics/C++.gif">
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-->
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</dl>
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<!-- NEW PAGE -->
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<!-- HEADER RIGHT "H5Zregister" -->
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<hr>
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<dl>
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<dt><strong>Name:</strong> <a name="Compression-Register">H5Zregister</a>
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<dt><strong>Signature:</strong>
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<dd><em>herr_t</em> <code>H5Zregister</code>(<em>const H5Z_class_t</em> <code>filter_class</code>)
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)
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<dt><strong>Purpose:</strong>
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<dd>Registers new filter.
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<dt><strong>Description:</strong>
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<dd><code>H5Zregister</code> registers a new filter with the
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HDF5 library.
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<p>
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Making a new filter available to an application is a two-step
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process. The first step is to write
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the three filter callback functions described below:
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<code>can_apply_func</code>, <code>set_local_func</code>, and
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<code>filter_func</code>.
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This call to <code>H5Zregister</code>,
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<span class="termEmphasis">registering</span> the filter with the
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library, is the second step.
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The <code>can_apply_func</code> and <code>set_local_func</code>
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fields can be set to <code>NULL</code>
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if they are not required for the filter being registered.
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<p>
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<code>H5Zregister</code> accepts a single parameter,
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the <code>filter_class</code> data structure,
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which is defined as follows:
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<pre>
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typedef struct H5Z_class_t {
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H5Z_filter_t filter_id;
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const char *comment;
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H5Z_can_apply_func_t can_apply_func;
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H5Z_set_local_func_t set_local_func;
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H5Z_func_t filter_func;
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} H5Z_class_t;
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</pre>
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<p>
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<code>filter_id</code> is the identifier for the new filter.
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This is a user-defined value between
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<code>H5Z_FILTER_RESERVED</code> and <code>H5Z_FILTER_MAX</code>,
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both of which are defined in the HDF5 source file
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<code>H5Zpublic.h</code>.
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<p>
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<code>comment</code> is used for debugging,
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may contain a descriptive name for the filter,
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and may be the null pointer.
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<p>
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<code>can_apply_func</code>, described in detail below,
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is a user-defined callback function which determines whether
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the combination of the dataset creation property list values,
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the datatype, and the dataspace represent a valid combination
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to apply this filter to.
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<p>
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<code>set_local_func</code>, described in detail below,
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is a user-defined callback function which sets any parameters that
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are specific to this dataset, based on the combination of the
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dataset creation property list values, the datatype, and the
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dataspace.
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<p>
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<code>filter_func</code>, described in detail below,
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is a user-defined callback function which performs the action
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of the filter.
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<p>
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The statistics associated with a filter are not reset
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by this function; they accumulate over the life of the library.
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<p>
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<strong>The callback functions</strong>
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<br>
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Before <code>H5Zregister</code> can link a filter into an
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application, three callback functions must be defined
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as described in the HDF5 Library header file <code>H5Zpublic.h</code>.
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<p>
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<u>The <i>can apply</i> callback function</u> is defined as follows:<br>
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<dir>
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<em>typedef herr_t</em> (*<code>H5Z_can_apply_func_t</code>)
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(<em>hid_t</em> <code>dcpl_id</code>,
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<em>hid_t</em> <code>type_id</code>,
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<em>hid_t</em> <code>space_id</code>)
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</dir>
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<p>
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Before a dataset is created, the <i>can apply</i> callbacks for
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any filters used in the dataset creation property list are called
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with the dataset's dataset creation property list, <code>dcpl_id</code>,
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the dataset's datatype, <code>type_id</code>, and
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a dataspace describing a chunk, <code>space_id</code>,
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(for chunked dataset storage).
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<p>
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This callback must determine whether the combination of the
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dataset creation property list settings, the datatype, and the
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dataspace represent a valid combination to which to apply this filter.
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For example, an invalid combination may involve
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the filter not operating correctly on certain datatypes,
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on certain datatype sizes, or on certain sizes of the chunk dataspace.
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<p>
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This callback can be the <code>NULL</code> pointer, in which case
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the library will assume that the filter can be applied to a dataset with
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any combination of dataset creation property list values, datatypes,
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and dataspaces.
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<p>
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The <i>can apply</i> callback function must return
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a positive value for a valid combination,
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zero for an invalid combination, and
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a negative value for an error.
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<p>
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<u>The <i>set local</i> callback function</u> is defined as follows:<br>
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<dir>
|
||
<em>typedef herr_t</em> (*<code>H5Z_set_local_func_t</code>)
|
||
(<em>hid_t</em> <code>dcpl_id</code>,
|
||
<em>hid_t</em> <code>type_id</code>,
|
||
<em>hid_t</em> <code>space_id</code>)
|
||
</dir>
|
||
<p>
|
||
After the <i>can apply</i> callbacks are checked for a new dataset,
|
||
the <i>set local</i> callback functions for any filters used in the
|
||
dataset creation property list are called.
|
||
These callbacks receive
|
||
<code>dcpl_id</code>, the dataset's private copy of the dataset
|
||
creation property list passed in to <code>H5Dcreate</code>
|
||
(i.e. not the actual property list passed in to <code>H5Dcreate</code>);
|
||
<code>type_id</code>, the datatype identifier passed in to
|
||
<code>H5Dcreate</code>,
|
||
which is not copied and should not be modified; and
|
||
<code>space_id</code>, a dataspace describing the chunk
|
||
(for chunked dataset storage), which should also not be modified.
|
||
<p>
|
||
The <i>set local</i> callback must set any filter parameters that are
|
||
specific to this dataset, based on the combination of the
|
||
dataset creation property list values, the datatype, and the dataspace.
|
||
For example, some filters perform different actions based on
|
||
different datatypes, datatype sizes, numbers of dimensions,
|
||
or dataspace sizes.
|
||
<p>
|
||
The <i>set local</i> callback may be the <code>NULL</code> pointer,
|
||
in which case, the library will assume that there are
|
||
no dataset-specific settings for this filter.
|
||
<p>
|
||
The <i>set local</i> callback function must return
|
||
a non-negative value on success and
|
||
a negative value for an error.
|
||
|
||
<p>
|
||
<u>The <i>filter operation</i> callback function</u>,
|
||
defining the filter's operation on the data, is defined as follows:
|
||
<dir>
|
||
<em>typedef size_t</em> (*<code>H5Z_func_t</code>)
|
||
(<em>unsigned int</em> <code>flags</code>,
|
||
<em>size_t</em> <code>cd_nelmts</code>,
|
||
<em>const unsigned int</em> <code>cd_values[]</code>,
|
||
<em>size_t</em> <code>nbytes</code>,
|
||
<em>size_t *</em><code>buf_size</code>,
|
||
<em>void **</em><code>buf</code>)
|
||
</dir>
|
||
|
||
<p>
|
||
The parameters <code>flags</code>, <code>cd_nelmts</code>,
|
||
and <code>cd_values</code> are the same as for the function
|
||
<a href="RM_H5P.html#Property-SetFilter"><code>H5Pset_filter</code></a>.
|
||
The one exception is that an additional flag,
|
||
<code>H5Z_FLAG_REVERSE</code>, is set when
|
||
the filter is called as part of the input pipeline.
|
||
<p>
|
||
The parameter <code>*buf</code> points to the input buffer
|
||
which has a size of <code>*buf_size</code> bytes,
|
||
<code>nbytes</code> of which are valid data.
|
||
<p>
|
||
The filter should perform the transformation in place if
|
||
possible. If the transformation cannot be done in place,
|
||
then the filter should allocate a new buffer with
|
||
<code>malloc()</code> and assign it to <code>*buf</code>,
|
||
assigning the allocated size of that buffer to
|
||
<code>*buf_size</code>.
|
||
The old buffer should be freed by calling <code>free()</code>.
|
||
<p>
|
||
If successful, the <i>filter operation</i> callback function
|
||
returns the number of valid bytes of data contained in <code>*buf</code>.
|
||
In the case of failure, the return value is <code>0</code> (zero)
|
||
and all pointer arguments are left unchanged.
|
||
<dt><strong>Note:</strong>
|
||
<dd>The <code>H5Zregister</code> interface is substantially revised
|
||
from the HDF5 Release 1.4.x series.
|
||
The <code>H5Z_class_t</code> struct and
|
||
the <i>set local</i> and <i>can apply</i> callback functions
|
||
first appeared in HDF5 Release 1.6.
|
||
<dt><strong>Parameters:</strong>
|
||
<ul><table>
|
||
<tr>
|
||
<td valign="top"><em>const H5Z_class_t</em> <code>filter_class </code></td>
|
||
<td valign="top">IN: Struct containing filter-definition information.</td></tr>
|
||
</table></ul>
|
||
<dt><strong>Returns:</strong>
|
||
<dd>Returns a non-negative value if successful;
|
||
otherwise returns a negative value.
|
||
<dt><strong>Fortran90 Interface:</strong>
|
||
<dd>None.
|
||
<!--
|
||
<pre>
|
||
|
||
</pre>
|
||
-->
|
||
|
||
<!--<dt><strong>Non-C API(s):</strong>
|
||
<dd>
|
||
|
||
<img src="Graphics/Java.gif">
|
||
<img src="Graphics/C++.gif">
|
||
-->
|
||
</dl>
|
||
|
||
<!-- NEW PAGE -->
|
||
<!-- HEADER RIGHT "H5Zunregister" -->
|
||
<hr>
|
||
<dl>
|
||
<dt><strong>Name:</strong> <a name="Compression-Unregister">H5Zunregister</a>
|
||
<dt><strong>Signature:</strong>
|
||
<dd><em>herr_t</em> <code>H5Zunregister</code>(<em>H5Z_filter_t</em> <code>filter</code>)
|
||
<dt><strong>Purpose:</strong>
|
||
<dd>Unregisters a filter.
|
||
<dt><strong>Description:</strong>
|
||
<dd><code>H5Zunregister</code> unregisters the filter
|
||
specified in <code>filter</code>. <20>
|
||
<p>
|
||
After a call to <code>H5Zunregister</code>, the filter
|
||
specified in <code>filter</code> will no longer be
|
||
available to the application.
|
||
<dt><strong>Parameters:</strong>
|
||
<ul><table>
|
||
<tr>
|
||
<td valign="top"><em>H5Z_filter_t</em> <code>filter </code></td>
|
||
<td valign="top">IN: Identifier of the filter to be unregistered.
|
||
See the introduction to this section of the reference manual
|
||
for a list of identifiers for standard filters
|
||
distributed with the HDF5 Library.</td></tr>
|
||
</table></ul>
|
||
<dt><strong>Returns:</strong>
|
||
<dd>Returns a non-negative value if successful;
|
||
otherwise returns a negative value.
|
||
<dt><strong>Fortran90 Interface:</strong> h5zunregister_f
|
||
<dd>
|
||
<pre>
|
||
SUBROUTINE h5zunregister_f(filter, hdferr)
|
||
IMPLICIT NONE
|
||
INTEGER, INTENT(IN) :: filter ! Filter; one of the possible values:
|
||
! H5Z_FILTER_DEFLATE_F
|
||
! H5Z_FILTER_SHUFFLE_F
|
||
! H5Z_FILTER_FLETCHER32_F
|
||
! H5Z_FILTER_SZIP_F
|
||
INTEGER, INTENT(OUT) :: hdferr ! Error code
|
||
! 0 on success, and -1 on failure
|
||
END SUBROUTINE h5zunregister_f
|
||
</pre>
|
||
|
||
<!--<dt><strong>Non-C API(s):</strong>
|
||
<dd>
|
||
|
||
<img src="Graphics/Java.gif">
|
||
<img src="Graphics/C++.gif">
|
||
-->
|
||
</dl>
|
||
|
||
<!-- HEADER RIGHT " " -->
|
||
|
||
<!-- #BeginLibraryItem "/ed_libs/NavBar_RM.lbi" --><hr>
|
||
<center>
|
||
<table border=0 width=98%>
|
||
<tr><td valign=top align=left>
|
||
<a href="index.html">HDF5 documents and links</a> <br>
|
||
<a href="H5.intro.html">Introduction to HDF5</a> <br>
|
||
<a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User Guide</a> <br>
|
||
<!--
|
||
<a href="Glossary.html">Glossary</a><br>
|
||
-->
|
||
</td>
|
||
<td valign=top align=right>
|
||
And in this document, the
|
||
<a href="RM_H5Front.html">HDF5 Reference Manual</a>
|
||
<br>
|
||
<a href="RM_H5.html">H5</a>
|
||
<a href="RM_H5A.html">H5A</a>
|
||
<a href="RM_H5D.html">H5D</a>
|
||
<a href="RM_H5E.html">H5E</a>
|
||
<a href="RM_H5F.html">H5F</a>
|
||
<a href="RM_H5G.html">H5G</a>
|
||
<a href="RM_H5I.html">H5I</a>
|
||
<a href="RM_H5P.html">H5P</a>
|
||
<br>
|
||
<a href="RM_H5R.html">H5R</a>
|
||
<a href="RM_H5S.html">H5S</a>
|
||
<a href="RM_H5T.html">H5T</a>
|
||
<a href="RM_H5Z.html">H5Z</a>
|
||
<a href="Tools.html">Tools</a>
|
||
<a href="PredefDTypes.html">Datatypes</a>
|
||
</td></tr>
|
||
</table>
|
||
</center>
|
||
<hr><!-- #EndLibraryItem --><!-- #BeginLibraryItem "/ed_libs/Footer.lbi" --><address>
|
||
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
|
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<br>
|
||
Describes HDF5 Release 1.7, the unreleased development branch; working toward HDF5 Release 1.8.0
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</address><!-- #EndLibraryItem --><SCRIPT LANGUAGE="JAVASCRIPT">
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