d586a1adb9
Purpose:
DreamWeaver (DW) adaptation of the HDF5 doc set, introducing the use of
stylesheets and DW libraries.
Stylesheets -- for consistent format management.
DW libraries -- for managing common elements across documents.
Platforms tested:
IE 5 and 6
Netscape
199 lines
6.9 KiB
HTML
199 lines
6.9 KiB
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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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<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: Compression Interface</h1>
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<h2>Compression API Functions</h2>
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This function enable the user to configure a new compression
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method for the local environment.
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<table border=0>
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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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</ul>
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</td></tr>
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</table>
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<p>
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HDF5 supports compression of raw data by compression methods
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built into the library or defined by an application.
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A compression method is associated with a dataset when the dataset is
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created and is applied independently to each storage chunk of the dataset.
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The dataset must use the <code>H5D_CHUNKED</code> storage layout.
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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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<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_method_t</em> <code>method</code>,
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<em>const char *</em><code>name</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 compression / uncompression function.
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<dt><strong>Description:</strong>
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<dd><code>H5Zregister</code> registers a new compression / uncompression
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function for the compression method specified by
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the method number, <code>method</code>.
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<p>
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<code>name</code> is used for debugging and may be the null pointer.
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<p>
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<code>function</code> is a user-defined function providing both
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compression and uncompression; it may be the null pointer.
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<p>
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The statistics associated with a method number 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> are defined in two phases. Before a filter can be
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linked into the application with <code>H5Zregister</code>,
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<code>H5Z_func_t</code> must first be defined as follows:
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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
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<code>H5Pset_filter()</code> 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 total 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_method_t</em> <code>method</code>
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<dd>IN: Number specifying compression method.
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<dt><em>const char *</em><code>name</code>
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<dd>IN: Name associated with the method number.
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Used for debugging purposes only.
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<dt><em>H5Z_func_t</em> <code>function</code>
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<dd>IN: Compression / uncompression method.
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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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</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: 11 February 2003
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