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HDF5/H5R API Specification
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<h1>H5R: Reference Interface</h1>
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<h2>Reference API Functions</h2>
The Reference interface allows the user to create references
to specific objects and data regions in an HDF5 file.
<p>
<strong>The C Interfaces:</strong>
<table border=0 width=80%>
<tr><td valign=top width=40%>
<ul>
<li><a href="#Reference-Create">H5Rcreate</a>
<li><a href="#Reference-Dereference">H5Rdereference</a>
</ul>
</td><td valign=top width=40%>
<ul>
<li><a href="#Reference-GetRegion">H5Rget_region</a>
<li><a href="#Reference-GetObjType">H5Rget_obj_type</a>
<li><span class="1_4_compat"><a href="#Reference-GetObjectType">H5Rget_object_type</a></span> *
</ul>
</td><td valign=top width=20%>
<ul>
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</table>
* Functions labelled with an asterisk (*) are provided only for
backwards compatibility with HDF5 Releases 1.4.<i>x</i>.
See further notes in the description of each function.
<p>
<i>Alphabetical Listing</i>
<table border="0">
<tr>
<td valign="top">
<li><a href="#Reference-Create">H5Rcreate</a>
<li><a href="#Reference-Dereference">H5Rdereference</a>
</td>
<td> </td>
<td valign="top">
<li><a href="#Reference-GetObjType">H5Rget_obj_type</a>
<li><a href="#Reference-GetObjectType">H5Rget_object_type</a> *
</td>
<td> </td>
<td valign="top">
<li><a href="#Reference-GetRegion">H5Rget_region</a>
</td>
</tr>
</table>
<p>
<strong>The FORTRAN90 Interfaces:</strong>
<br>
<font size=-1>
<i>In general, each FORTRAN90 subroutine performs exactly the same task
as the corresponding C function. The links below go to the C function
descriptions, which serve as general descriptions for both. A button,
under <strong>Non-C API(s)</strong> at the end of the C function description,
opens an external browser window displaying the FORTRAN90-specific
information. You will probably want to adjust the size and location of
this external window so that both browser windows are visible and to
facilitate moving easily between them.</i>
</font>
<table border=0 width=80%>
<tr><td valign=top width=40%>
<ul>
<li><a href="#Reference-Create">h5rcreate_f</a>
<li><a href="#Reference-Dereference">h5rdereference_f</a>
</ul>
</td><td valign=top width=40%>
<ul>
<li><a href="#Reference-GetRegion">h5rget_region_f</a>
<li><a href="#Reference-GetObjectType">h5rget_object_type_f</a>
</ul>
</td><td valign=top width=20%>
<ul>
</ul>
</td></tr>
</table>
<p>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Reference-Create">H5Rcreate</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Rcreate</code>(<em>void *</em><code>ref</code>,
<em>hid_t</em> <code>loc_id</code>,
<em>const char *</em><code>name</code>,
<em>H5R_type_t</em> <code>ref_type</code>,
<em>hid_t</em> <code>space_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Creates a reference.
<dt><strong>Description:</strong>
<dd><code>H5Rcreate</code> creates the reference, <code>ref</code>,
of the type specified in <code>ref_type</code>, pointing to
the object <code>name</code> located at <code>loc_id</code>.
<p>
The HDF5 library maps the <em>void</em> type specified above
for <code>ref</code> to the type specified in <code>ref_type</code>,
which will be one of those appearing in the first column of
the following table.
The second column of the table lists the HDF5 constant associated
with each reference type.
<dir>
<table border=0>
<tr><td><em>hdset_reg_ref_t</em> </td>
<td><code>H5R_DATASET_REGION</code> </td>
<td>Dataset region reference</td></tr>
<tr><td><em>hobj_ref_t</em></td>
<td><code>H5R_OBJECT</code></td>
<td>Object reference</td></tr>
</table>
</dir>
<p>
The parameters <code>loc_id</code> and <code>name</code> are
used to locate the object.
<p>
The parameter <code>space_id</code> identifies the region
to be pointed to for a dataset region reference.
This parameter is unused with object references.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>void *</em><code>ref</code>
<dd>OUT: Reference created by the function call.
<dt><em>hid_t</em> <code>loc_id</code>
<dd>IN: Location identifier used to locate the object being
pointed to.
<dt><em>const char *</em><code>name</code>
<dd>IN: Name of object at location <code>loc_id</code>.
<dt><em>H5R_type_t</em> <code>ref_type</code>
<dd>IN: Type of reference.
<dt><em>hid_t</em> <code>space_id</code>
<dd>IN: Dataspace identifier with selection.
Used for dataset region references.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5r_FORTRAN.html#h5rcreate_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Reference-Dereference">H5Rdereference</a>
<dt><strong>Signature:</strong>
<dd><em>hid_t</em> <code>H5Rdereference</code>(<em>hid_t</em> <code>dataset</code>,
<em>H5R_type_t</em> <code>ref_type</code>,
<em>void *</em><code>ref</code>
)
<dt><strong>Purpose:</strong>
<dd>Opens the HDF5 object referenced.
<dt><strong>Description:</strong>
<dd>Given a reference to some object, <code>H5Rdereference</code>
opens that object and returns an identifier.
<p>
The parameter <code>ref_type</code> specifies the reference type
of <code>ref</code>.
<code>ref_type</code> may contain either of the following values:
<ul>
<li><code>H5R_OBJECT</code> (<code>0</code>)
<li><code>H5R_DATASET_REGION</code> (<code>1</code>)
</ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>dataset</code>
<dd>IN: Dataset containing reference object.
<dt><em>H5R_type_t</em> <code>ref_type</code>
<dd>IN: The reference type of <code>ref</code>.
<dt><em>void *</em><code>ref</code>
<dd>IN: Reference to open.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns valid identifier if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5r_FORTRAN.html#h5rdereference_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Reference-GetRegion">H5Rget_region</a>
<dt><strong>Signature:</strong>
<dd><em>hid_t</em> <code>H5Rget_region</code>(<em>hid_t</em> <code>dataset</code>,
<em>H5R_type_t</em> <code>ref_type</code>,
<em>void *</em><code>ref</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves a dataspace with the specified region selected.
<dt><strong>Description:</strong>
<dd>Given a reference to an object <code>ref</code>,
<code>H5Rget_region</code> creates a copy of the dataspace
of the dataset pointed to and defines a selection in the copy
which is the region pointed to.
<p>
The parameter <code>ref_type</code> specifies the reference type
of <code>ref</code>.
<code>ref_type</code> may contain the following value:
<ul>
<li><code>H5R_DATASET_REGION</code> (<code>1</code>)
</ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>dataset</code>,
<dd>IN: Dataset containing reference object.
<dt><em>H5R_type_t</em> <code>ref_type</code>,
<dd>IN: The reference type of <code>ref</code>.
<dt><em>void *</em><code>ref</code>
<dd>IN: Reference to open.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a valid identifier if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5r_FORTRAN.html#h5rget_region_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Reference-GetObjType">H5Rget_obj_type</a>
<dt><strong>Signature:</strong>
<dd><em>H5G_obj_t</em> <code>H5Rget_obj_type</code>(<em>hid_t</em> <code>id</code>,
<em>H5R_type_t</em> <code>ref_type</code>,
<em>void *</em><code>ref</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the type of object that an object reference points to.
<dt><strong>Description:</strong>
<dd>Given type of object reference, <code>ref_type</code>,
and a reference to an object, <code>ref</code>,
<code>H5Rget_obj_type</code>
returns the type of the referenced object.
<p>
Valid object reference types, to pass in as <code>ref_type</code>,
include the following:
<table border="0">
<tr align=left valign=top><td> </td><td>
<code>H5R_OBJECT</code></td><td>
Reference is an object reference.
</td></tr>
<tr align=left valign=top><td> </td><td>
<code>H5R_DATASET_REGION </code></td><td>
Reference is a dataset region reference.
</td></tr>
</table>
<p>
Valid object type return values include the following:
<table border="0">
<tr align=left valign=top><td> </td><td>
<code>H5G_LINK</code></td><td>
Object is a symbolic link.
</td></tr>
<tr align=left valign=top><td> </td><td>
<code>H5G_GROUP</code></td><td>
Object is a group.
</td></tr>
<tr align=left valign=top><td> </td><td>
<code>H5G_DATASET </code></td><td>
Object is a dataset.
</td></tr>
<tr align=left valign=top><td> </td><td>
<code>H5G_TYPE</code></td><td>
Object is a named datatype.
</td></tr>
</table>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>id</code>,
<dd>IN: The dataset containing the reference object or
the location identifier of the object that the
dataset is located within.
<dt><em>H5R_type_t</em> <code>ref_type</code>
<dd>IN: Type of reference to query.
<dt><em>void *</em><code>ref</code>
<dd>IN: Reference to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns an object type as defined in <code>H5Gpublic.h</code> if successful;
otherwise returns <code>H5G_UNKNOWN</code>.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5r_FORTRAN.html#h5rget_object_type_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Reference-GetObjectType">H5Rget_object_type</a>
<dt><strong>Signature:</strong>
<dd><em>int</em> <code>H5Rget_object_type</code>(<em>hid_t</em> <code>id</code>,
<em>void *</em><code>ref</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the type of object that an object reference points to.
<dt><strong>Description:</strong>
<dd>[<strong>NOTE:</strong>
<span class="1_4_compat">
This function is provided only to enable backward compatibility
with HDF5 Releases 1.4.<i>x</i>.
This function is enabled only if the HDF5 library is configured
with the flag <code>H5_WANT_H5_V1_4_COMPAT</code> and is not
enabled in the binaries distributed by NCSA.
This function has been replaced in Release 1.6 by the function
<a href="#Reference-GetObjType"><code>H5Rget_obj_type</code></a>
and will eventually be deleted from the HDF5 distribution.</span>]
<p>
</p>Given a reference to an object <code>ref</code>,
<code>H5Rget_object_type</code> returns the
type of the object pointed to.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>id</code>,
<dd>IN: The dataset containing the reference object or
the location identifier of the object that the dataset
is located within.
<dt><em>void *</em><code>ref</code>
<dd>IN: Reference to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns an object type as defined in <code>H5Gpublic.h</code>;
otherwise returns <code>H5G_UNKNOWN</code>.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5r_FORTRAN.html#h5rget_object_type_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
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