mirrors/hdf5
2
0
Fork 0
mirror of https://github.com/HDFGroup/hdf5.git synced 2026-09-27 04:09:40 +03:00
Code Issues Packages Projects Releases Wiki Activity
Files
cdad39df49be74671663ccf04631094ee3d93204
hdf5/develop/_l_b_attr_create.html
T
byrnHDF cdad39df49 deploy: 33bb1970b8
2024-02-09 17:39:10 +00:00

249 lines
17 KiB
HTML
Raw Blame History

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=9"/>
<meta name="generator" content="Doxygen 1.10.0"/>
<meta name="viewport" content="width=device-width, initial-scale=1"/>
<title>HDF5: Creating an Attribute</title>
<link href="tabs.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="dynsections.js"></script>
<link href="navtree.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="resize.js"></script>
<script type="text/javascript" src="navtreedata.js"></script>
<script type="text/javascript" src="navtree.js"></script>
<script type="text/javascript" src="cookie.js"></script>
<link href="search/search.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="search/searchdata.js"></script>
<script type="text/javascript" src="search/search.js"></script>
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:d3d9a9a6595521f9666a5e94cc830dab83b65699&amp;dn=expat.txt MIT */
$(function() { init_search(); });
/* @license-end */
</script>
<link href="doxygen.css" rel="stylesheet" type="text/css" />
<link href="hdf5doxy.css" rel="stylesheet" type="text/css">
<!-- <link href="hdf5doxy.css" rel="stylesheet" type="text/css"/>
-->
<script type="text/javascript" src="hdf5_navtree_hacks.js"></script>
</head>
<body>
<div style="background:#FFDDDD;font-size:120%;text-align:center;margin:0;padding:5px">Please, help us to better serve our user community by answering the following short survey: <a href="https://www.hdfgroup.org/website-survey/">https://www.hdfgroup.org/website-survey/</a></div>
<div id="top"><!-- do not remove this div, it is closed by doxygen! -->
<div id="titlearea">
<table cellspacing="0" cellpadding="0">
<tbody>
<tr style="height: 56px;">
<td id="projectlogo"><img alt="Logo" src="HDFG-logo.png"/></td>
<td id="projectalign" style="padding-left: 0.5em;">
<div id="projectname"><a href="https://www.hdfgroup.org">HDF5</a>
&#160;<span id="projectnumber">1.15.0.33bb197</span>
</div>
<div id="projectbrief">API Reference</div>
</td>
<td> <div id="MSearchBox" class="MSearchBoxInactive">
<span class="left">
<span id="MSearchSelect" onmouseover="return searchBox.OnSearchSelectShow()" onmouseout="return searchBox.OnSearchSelectHide()">&#160;</span>
<input type="text" id="MSearchField" value="" placeholder="Search" accesskey="S"
onfocus="searchBox.OnSearchFieldFocus(true)"
onblur="searchBox.OnSearchFieldFocus(false)"
onkeyup="searchBox.OnSearchFieldChange(event)"/>
</span><span class="right">
<a id="MSearchClose" href="javascript:searchBox.CloseResultsWindow()"><img id="MSearchCloseImg" border="0" src="search/close.svg" alt=""/></a>
</span>
</div>
</td>
</tr>
</tbody>
</table>
</div>
<!-- end header part -->
<!-- Generated by Doxygen 1.10.0 -->
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:d3d9a9a6595521f9666a5e94cc830dab83b65699&amp;dn=expat.txt MIT */
var searchBox = new SearchBox("searchBox", "search/",'.html');
/* @license-end */
</script>
</div><!-- top -->
<div id="side-nav" class="ui-resizable side-nav-resizable">
<div id="nav-tree">
<div id="nav-tree-contents">
<div id="nav-sync" class="sync"></div>
</div>
</div>
<div id="splitbar" style="-moz-user-select:none;"
class="ui-resizable-handle">
</div>
</div>
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:d3d9a9a6595521f9666a5e94cc830dab83b65699&amp;dn=expat.txt MIT */
$(function(){initNavTree('_l_b_attr_create.html',''); initResizable(); });
/* @license-end */
</script>
<div id="doc-content">
<!-- window showing the filter options -->
<div id="MSearchSelectWindow"
onmouseover="return searchBox.OnSearchSelectShow()"
onmouseout="return searchBox.OnSearchSelectHide()"
onkeydown="return searchBox.OnSearchSelectKey(event)">
</div>
<!-- iframe showing the search results (closed by default) -->
<div id="MSearchResultsWindow">
<div id="MSearchResults">
<div class="SRPage">
<div id="SRIndex">
<div id="SRResults"></div>
<div class="SRStatus" id="Loading">Loading...</div>
<div class="SRStatus" id="Searching">Searching...</div>
<div class="SRStatus" id="NoMatches">No Matches</div>
</div>
</div>
</div>
</div>
<div><div class="header">
<div class="headertitle"><div class="title">Creating an Attribute</div></div>
</div><!--header-->
<div class="contents">
<div class="textblock"><p>Navigate back: <a class="el" href="index.html">Main</a> / <a class="el" href="_getting_started.html">Getting Started with HDF5</a> / <a class="el" href="_learn_basics.html">Learning the Basics</a> </p><hr />
<p>Attributes are small datasets that can be used to describe the nature and/or the intended usage of the object they are attached to. In this section, we show how to create, read, and write an attribute.</p>
<h1><a class="anchor" id="secLBAttrCreate"></a>
Creating an attribute</h1>
<p>Creating an attribute is similar to creating a dataset. To create an attribute, the application must specify the object which the attribute is attached to, the datatype and dataspace of the attribute data, and the attribute creation property list.</p>
<p>The steps to create an attribute are as follows: </p><ol>
<li>
Obtain the object identifier that the attribute is to be attached to. </li>
<li>
Define the characteristics of the attribute and specify the attribute creation property list. <ul>
<li>
Define the datatype. </li>
<li>
Define the dataspace. </li>
<li>
Specify the attribute creation property list. </li>
</ul>
</li>
<li>
Create the attribute. </li>
<li>
Close the attribute and datatype, dataspace, and attribute creation property list, if necessary. </li>
</ol>
<p>To create and close an attribute, the calling program must use <a class="el" href="group___h5_a.html#ga4a76e4e5ab6eb0fd2aa7990d38d55f24">H5Acreate</a> and <a class="el" href="group___h5_a.html#gaef4394b661e2c930879e9868e122bdda" title="Closes the specified attribute.">H5Aclose</a>. For example:</p>
<p><em>C</em> </p><div class="fragment"><div class="line">attr_id = <a class="code hl_define" href="group___h5_a.html#ga4a76e4e5ab6eb0fd2aa7990d38d55f24">H5Acreate</a> (dataset_id, <span class="stringliteral">&quot;Units&quot;</span>, <a class="code hl_define" href="group___p_d_t_s_t_d.html#ga37e8a6be7ee64587c2a282b965019bb8">H5T_STD_I32BE</a>, dataspace_id, <a class="code hl_define" href="_h5_ppublic_8h.html#afa85e97bfbf9bf1c58e39263846c568f">H5P_DEFAULT</a>, <a class="code hl_define" href="_h5_ppublic_8h.html#afa85e97bfbf9bf1c58e39263846c568f">H5P_DEFAULT</a>)</div>
<div class="line">status = <a class="code hl_function" href="group___h5_a.html#gaef4394b661e2c930879e9868e122bdda">H5Aclose</a> (attr_id);</div>
<div class="ttc" id="a_h5_ppublic_8h_html_afa85e97bfbf9bf1c58e39263846c568f"><div class="ttname"><a href="_h5_ppublic_8h.html#afa85e97bfbf9bf1c58e39263846c568f">H5P_DEFAULT</a></div><div class="ttdeci">#define H5P_DEFAULT</div><div class="ttdef"><b>Definition</b> H5Ppublic.h:102</div></div>
<div class="ttc" id="agroup___h5_a_html_ga4a76e4e5ab6eb0fd2aa7990d38d55f24"><div class="ttname"><a href="group___h5_a.html#ga4a76e4e5ab6eb0fd2aa7990d38d55f24">H5Acreate</a></div><div class="ttdeci">#define H5Acreate</div><div class="ttdef"><b>Definition</b> H5version.h:868</div></div>
<div class="ttc" id="agroup___h5_a_html_gaef4394b661e2c930879e9868e122bdda"><div class="ttname"><a href="group___h5_a.html#gaef4394b661e2c930879e9868e122bdda">H5Aclose</a></div><div class="ttdeci">herr_t H5Aclose(hid_t attr_id)</div><div class="ttdoc">Closes the specified attribute.</div></div>
<div class="ttc" id="agroup___p_d_t_s_t_d_html_ga37e8a6be7ee64587c2a282b965019bb8"><div class="ttname"><a href="group___p_d_t_s_t_d.html#ga37e8a6be7ee64587c2a282b965019bb8">H5T_STD_I32BE</a></div><div class="ttdeci">#define H5T_STD_I32BE</div><div class="ttdef"><b>Definition</b> H5Tpublic.h:305</div></div>
</div><!-- fragment --><p><em>Fortran</em> </p><div class="fragment"><div class="line">CALL h5acreate_f (dset_id, attr_nam, type_id, space_id, attr_id, &amp;</div>
<div class="line"> hdferr, creation_prp=creat_plist_id)</div>
<div class="line">or</div>
<div class="line">CALL h5acreate_f (dset_id, attr_nam, type_id, space_id, attr_id, hdferr)</div>
<div class="line"> </div>
<div class="line">CALL h5aclose_f (attr_id, hdferr)</div>
</div><!-- fragment --><h1><a class="anchor" id="secLBAttrCreateRW"></a>
Reading/Writing an attribute</h1>
<p>Attributes may only be read or written as an entire object; no partial I/O is supported. Therefore, to perform I/O operations on an attribute, the application needs only to specify the attribute and the attribute's memory datatype.</p>
<p>The steps to read or write an attribute are as follows. </p><ol>
<li>
Obtain the attribute identifier. </li>
<li>
Specify the attribute's memory datatype. </li>
<li>
Perform the desired operation. </li>
<li>
Close the memory datatype if necessary. </li>
</ol>
<p>To read and/or write an attribute, the calling program must contain the <a class="el" href="group___h5_a.html#gaacb27a997f7c98e8a833d0fd63b58f1c" title="Reads the value of an attribute.">H5Aread</a> and/or <a class="el" href="group___h5_a.html#gab70871e205d57450c83efd9912be2b5c" title="Writes data to an attribute.">H5Awrite</a> routines. For example:</p>
<p><em>C</em> </p><div class="fragment"><div class="line">status = <a class="code hl_function" href="group___h5_a.html#gaacb27a997f7c98e8a833d0fd63b58f1c">H5Aread</a> (attr_id, mem_type_id, buf);</div>
<div class="line">status = <a class="code hl_function" href="group___h5_a.html#gab70871e205d57450c83efd9912be2b5c">H5Awrite</a> (attr_id, mem_type_id, buf);</div>
<div class="ttc" id="agroup___h5_a_html_gaacb27a997f7c98e8a833d0fd63b58f1c"><div class="ttname"><a href="group___h5_a.html#gaacb27a997f7c98e8a833d0fd63b58f1c">H5Aread</a></div><div class="ttdeci">herr_t H5Aread(hid_t attr_id, hid_t type_id, void *buf)</div><div class="ttdoc">Reads the value of an attribute.</div></div>
<div class="ttc" id="agroup___h5_a_html_gab70871e205d57450c83efd9912be2b5c"><div class="ttname"><a href="group___h5_a.html#gab70871e205d57450c83efd9912be2b5c">H5Awrite</a></div><div class="ttdeci">herr_t H5Awrite(hid_t attr_id, hid_t type_id, const void *buf)</div><div class="ttdoc">Writes data to an attribute.</div></div>
</div><!-- fragment --><p><em>Fortran</em> </p><div class="fragment"><div class="line">CALL h5awrite_f (attr_id, mem_type_id, buf, dims, hdferr) </div>
<div class="line">CALL h5aread_f (attr_id, mem_type_id, buf, dims, hdferr)</div>
</div><!-- fragment --><h1><a class="anchor" id="secLBAttrCreateHL"></a>
High Level APIs</h1>
<p>The High Level <a class="el" href="group___h5_l_t.html">HDF5 Lite APIs (H5LT,H5LD)</a> include functions that simplify and condense the steps for creating and reading datasets. Please be sure to review them, in addition to this tutorial.</p>
<h1><a class="anchor" id="secLBAttrCreateRWEx"></a>
Programming Example</h1>
<h2><a class="anchor" id="secLBAttrCreateRWExDesc"></a>
Description</h2>
<p>See <a class="el" href="_l_b_examples.html">Examples from Learning the Basics</a> for the examples used in the <a class="el" href="_learn_basics.html">Learning the Basics</a> tutorial.</p>
<p>The example shows how to create and write a dataset attribute. It opens an existing file <code style="background-color:whitesmoke;">dset.h5</code> in C (<code style="background-color:whitesmoke;">dsetf.h5</code> in FORTRAN), obtains the identifier of the dataset <code style="background-color:whitesmoke;">/dset</code>, defines the attribute's dataspace, creates the dataset attribute, writes the attribute, and then closes the attribute's dataspace, attribute, dataset, and file.</p>
<p>For details on compiling an HDF5 application: [ <a class="el" href="_l_b_compiling.html">Compiling HDF5 Applications</a> ]</p>
<h2><a class="anchor" id="secLBAttrCreateRWExRem"></a>
Remarks</h2>
<p><a class="el" href="group___h5_a.html#ga4a76e4e5ab6eb0fd2aa7990d38d55f24">H5Acreate</a> creates an attribute which is attached to the object specified by the first parameter, and returns an identifier.</p>
<p><a class="el" href="group___h5_a.html#gab70871e205d57450c83efd9912be2b5c" title="Writes data to an attribute.">H5Awrite</a> writes the entire attribute, and returns the status of the write.</p>
<p>When an attribute is no longer accessed by a program, <a class="el" href="group___h5_a.html#gaef4394b661e2c930879e9868e122bdda" title="Closes the specified attribute.">H5Aclose</a> must be called to release the attribute from use. An <a class="el" href="group___h5_a.html#gaef4394b661e2c930879e9868e122bdda" title="Closes the specified attribute.">H5Aclose</a>/h5aclose_f call is mandatory.</p>
<h2><a class="anchor" id="secLBAttrCreateRWExCont"></a>
File Contents</h2>
<p>Shown below is the contents and the attribute definition of <code style="background-color:whitesmoke;">dset.h5</code> (created by the C program).</p>
<p><em>dset.h5 in DDL</em> </p><div class="fragment"><div class="line">HDF5 <span class="stringliteral">&quot;dset.h5&quot;</span> {</div>
<div class="line">GROUP <span class="stringliteral">&quot;/&quot;</span> {</div>
<div class="line">DATASET <span class="stringliteral">&quot;dset&quot;</span> {</div>
<div class="line">DATATYPE { <a class="code hl_define" href="group___p_d_t_s_t_d.html#ga37e8a6be7ee64587c2a282b965019bb8">H5T_STD_I32BE</a> }</div>
<div class="line">DATASPACE { SIMPLE ( 4, 6 ) / ( 4, 6 ) }</div>
<div class="line">DATA {</div>
<div class="line"> 1, 2, 3, 4, 5, 6,</div>
<div class="line"> 7, 8, 9, 10, 11, 12,</div>
<div class="line"> 13, 14, 15, 16, 17, 18,</div>
<div class="line"> 19, 20, 21, 22, 23, 24</div>
<div class="line">}</div>
<div class="line">ATTRIBUTE <span class="stringliteral">&quot;attr&quot;</span> {</div>
<div class="line"> DATATYPE { <a class="code hl_define" href="group___p_d_t_s_t_d.html#ga37e8a6be7ee64587c2a282b965019bb8">H5T_STD_I32BE</a> }</div>
<div class="line"> DATASPACE { SIMPLE ( 2 ) / ( 2 ) }</div>
<div class="line"> DATA {</div>
<div class="line"> 100, 200</div>
<div class="line"> }</div>
<div class="line">}</div>
<div class="line">}</div>
<div class="line">}</div>
<div class="line">}</div>
</div><!-- fragment --><p>Shown below is the contents and the attribute definition of <code style="background-color:whitesmoke;">dsetf.h5</code> (created by the FORTRAN program).</p>
<p><em>dsetf.h5 in DDL</em> </p><div class="fragment"><div class="line">HDF5 <span class="stringliteral">&quot;dsetf.h5&quot;</span> {</div>
<div class="line">GROUP <span class="stringliteral">&quot;/&quot;</span> {</div>
<div class="line">DATASET <span class="stringliteral">&quot;dset&quot;</span> {</div>
<div class="line">DATATYPE { <a class="code hl_define" href="group___p_d_t_s_t_d.html#ga37e8a6be7ee64587c2a282b965019bb8">H5T_STD_I32BE</a> }</div>
<div class="line">DATASPACE { SIMPLE ( 6, 4 ) / ( 6, 4 ) }</div>
<div class="line">DATA {</div>
<div class="line"> 1, 7, 13, 19,</div>
<div class="line"> 2, 8, 14, 20,</div>
<div class="line"> 3, 9, 15, 21,</div>
<div class="line"> 4, 10, 16, 22,</div>
<div class="line"> 5, 11, 17, 23,</div>
<div class="line"> 6, 12, 18, 24</div>
<div class="line">}</div>
<div class="line">ATTRIBUTE <span class="stringliteral">&quot;attr&quot;</span> {</div>
<div class="line"> DATATYPE { <a class="code hl_define" href="group___p_d_t_s_t_d.html#ga37e8a6be7ee64587c2a282b965019bb8">H5T_STD_I32BE</a> }</div>
<div class="line"> DATASPACE { SIMPLE ( 2 ) / ( 2 ) }</div>
<div class="line"> DATA {</div>
<div class="line"> 100, 200</div>
<div class="line"> }</div>
<div class="line">}</div>
<div class="line">}</div>
<div class="line">}</div>
<div class="line">}</div>
</div><!-- fragment --><h2><a class="anchor" id="secLBAttrCreateRWExDDL"></a>
Attribute Definition in DDL</h2>
<p><em>HDF5 Attribute Definition</em> </p><div class="fragment"><div class="line">&lt;attribute&gt; ::= ATTRIBUTE <span class="stringliteral">&quot;&lt;attr_name&gt;&quot;</span> { &lt;datatype&gt;</div>
<div class="line"> &lt;dataspace&gt;</div>
<div class="line"> &lt;data&gt; }</div>
</div><!-- fragment --><hr />
<p> Navigate back: <a class="el" href="index.html">Main</a> / <a class="el" href="_getting_started.html">Getting Started with HDF5</a> / <a class="el" href="_learn_basics.html">Learning the Basics</a> </p>
</div></div><!-- contents -->
</div><!-- PageDoc -->
</div><!-- doc-content -->
<!-- start footer part -->
<div id="nav-path" class="navpath"><!-- id is needed for treeview function! -->
<ul>
<li class="footer">Generated by
<a href="http://www.doxygen.org/index.html">
<img class="footer" src="doxygen.png" alt="doxygen"/></a> 1.10.0 </li>
</ul>
</div>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink