4c6122a53c
Purpose:
Link in additional Fortran90 functions.
Description:
Linked 68 new Fortran90 functions to the discussions of the corresponding
C functions. Made the corresponding Fortran index changes in the
function listings at the tops of the RM pages.
Fixed formatting and link typos in RM_H5P.html & fortran/h5p_FORTRAN.html.
Platforms tested:
Safari and IE 5
341 lines
12 KiB
HTML
341 lines
12 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" --><link href="ed_styles/RMelect.css" rel="stylesheet" type="text/css"><!-- #EndLibraryItem --></head>
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<body bgcolor="#FFFFFF">
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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="H5.user.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>
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<!-- #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>
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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>
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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><td> </td><td valign=top>
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<ul>
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<li><a href="#Compression-FilterAvail">H5Zfilter_avail</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 and a shuffling algorithm) and
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error checking (Fletcher32 checksum).
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For further flexibility, the library includes tools enabling 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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As mentioned above, one set of filters distributed with HDF5 provides
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built-in methods for raw data compression.
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The flexibility of the filter pipeline implementation enables the
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definition of additional compression methods by a user application.
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A compression method<br>
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—
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is associated with a dataset when the dataset is created,<br>
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—
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can be used only with chunked data (ie., datasets stored in the
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<code>H5D_CHUNKED</code> storage layout), and<br>
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—
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is applied independently to each chunk of the dataset.
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<p>
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The HDF5 library does not support compression 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 compression is not supported because it would not produce
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significant results.
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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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<p>
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<strong>The FORTRAN90 Interfaces:</strong>
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<br>
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<font size=-1>
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<i>In general, each FORTRAN90 subroutine performs exactly the same task
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as the corresponding C function. The links below go to the C function
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descriptions, which serve as general descriptions for both. A button,
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under <strong>Non-C API(s)</strong> at the end of the C function description,
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opens an external browser window displaying the FORTRAN90-specific
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information. You will probably want to adjust the size and location of
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this external window so that both browser windows are visible and to
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facilitate moving easily between them.</i>
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</font>
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<table border=0 width=80%>
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<tr><td valign=top>
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<ul>
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<!--<li><a href="#Compression-Register">h5zregister_f</a> -->
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</ul>
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</td><td> </td><td valign=top>
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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><td> </td><td valign=top>
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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></tr>
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</table>
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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>H5Z_filter_t</em> <code>filter</code>,
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<em>const char *</em><code>comment</code>,
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<em>H5Z_func_t</em> <code>function</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 <span class="termEmphasis">define</span>
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the new filter <code>function</code> as described below.
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This step can be skipped only when the filter is predifined, as is
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the case with the Fletcher32 checksum and shuffle filters that
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are distributed with the HDF5 Library.
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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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<p>
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The new filter is specified by the filter identifier
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<code>filter</code>.
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<p>
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<code>comment</code> is used for debugging and may be
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the null pointer.
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<p>
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<code>function</code> is a user-defined function
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which performs the action 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><strong>New filters.</strong> Before a filter can be
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linked into an application with <code>H5Zregister</code>,
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the filter must be defined as described in the HDF5 Library
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header file <code>H5Zpublic.h</code>:
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<dir>
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<em>typedef size_t</em> (*<code>H5Z_func_t</code>)
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(<em>unsigned int</em> <code>flags</code>,
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<em>size_t</em> <code>cd_nelmts</code>,
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<em>const unsigned int</em> <code>cd_values[]</code>,
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<em>size_t</em> <code>nbytes</code>,
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<em>size_t *</em><code>buf_size</code>,
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<em>void **</em><code>buf</code>)
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</dir>
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<p>The parameters <code>flags</code>, <code>cd_nelmts</code>,
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and <code>cd_values</code> are the same as for the function
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The additional flag <code>H5Z_FLAG_REVERSE</code> is set when
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the filter is called as part of the input pipeline.
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The parameter <code>*buf</code> points to the input buffer
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which has a size of <code>*buf_size</code> bytes,
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<code>nbytes</code> of which are valid data.
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<p>The filter should perform the transformation in place if
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possible and return the number of valid bytes or zero for
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failure. If the transformation cannot be done in place,
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then the filter should allocate a new buffer with
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<code>malloc()</code> and assign it to <code>*buf</code>,
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assigning the allocated size of that buffer to
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<code>*buf_size</code>.
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The old buffer should be freed by calling <code>free()</code>.
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<dt><strong>Parameters:</strong>
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<dl>
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<dt><em>H5Z_filter_t</em> <code>method</code>
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<dd>IN: Filter identifier.
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<dt><em>const char *</em><code>comment</code>
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<dd>IN: String associated with the filter;
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used for debugging purposes only.
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May be the null pointer.
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<dt><em>H5Z_func_t</em> <code>function</code>
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<dd>IN: Filter function.
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</dl>
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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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<!--
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<dt><strong>Non-C API(s):</strong>
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<dd><a href="fortran/h5z_FORTRAN.html#h5zregister_f"
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target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
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--> <!--
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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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<hr>
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<dl>
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<dt><strong>Name:</strong> <a name="Compression-Unregister">H5Zunregister</a>
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<dt><strong>Signature:</strong>
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<dd><em>herr_t</em> <code>H5Zunregister</code>(<em>H5Z_filter_t</em> <code>filter</code>)
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<dt><strong>Purpose:</strong>
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<dd>Unregisters a filter.
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<dt><strong>Description:</strong>
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<dd><code>H5Zunregister</code> unregisters the filter
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specified in <code>filter</code>.
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<p>
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After a call to <code>H5Zunregister</code>, the filter
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specified in <code>filter</code> will no longer be
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available to the application.
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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 be unregistered.
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</dl>
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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>Non-C API(s):</strong>
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<dd><a href="fortran/h5z_FORTRAN.html#h5zunregister_f"
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target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
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<!--
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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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<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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<dl>
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<dt><em>H5Z_filter_t</em> <code>filter</code>
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<dd>IN: Filter identifier.
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</dl>
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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>Non-C API(s):</strong>
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<dd><a href="fortran/h5z_FORTRAN.html#h5zfilter_avail_f"
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target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
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<!--
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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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<!-- #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="H5.user.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>
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<!-- #EndLibraryItem -->
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<!-- #BeginLibraryItem "/ed_libs/Footer.lbi" --><address>
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<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
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<br>
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Describes HDF5 Release 1.5, Unreleased Development Branch
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</address><!-- #EndLibraryItem -->
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Last modified: 8 April 2003
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</body>
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</html>
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