mirror of
https://github.com/HDFGroup/hdf5.git
synced 2024-12-09 07:32:32 +08:00
652 lines
23 KiB
HTML
652 lines
23 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
|
|
<html>
|
|
<head>
|
|
<title>Reference (H5R) and Identifier Interfaces (H5I)</title>
|
|
|
|
<!-- #BeginLibraryItem "/ed_libs/styles_UG.lbi" -->
|
|
<!--
|
|
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
|
|
* Copyright by the Board of Trustees of the University of Illinois. *
|
|
* All rights reserved. *
|
|
* *
|
|
* This file is part of HDF5. The full HDF5 copyright notice, including *
|
|
* terms governing use, modification, and redistribution, is contained in *
|
|
* the files COPYING and Copyright.html. COPYING can be found at the root *
|
|
* of the source code distribution tree; Copyright.html can be found at the *
|
|
* root level of an installed copy of the electronic HDF5 document set and *
|
|
* is linked from the top-level documents page. It can also be found at *
|
|
* http://hdf.ncsa.uiuc.edu/HDF5/doc/Copyright.html. If you do not have *
|
|
* access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. *
|
|
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
|
|
-->
|
|
|
|
<link href="ed_styles/UGelect.css" rel="stylesheet" type="text/css">
|
|
<!-- #EndLibraryItem --></head>
|
|
|
|
<body bgcolor="#FFFFFF">
|
|
|
|
|
|
<!-- #BeginLibraryItem "/ed_libs/NavBar_UG.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="RM_H5Front.html">HDF5 Reference Manual</a> <br>
|
|
<a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User's Guide for Release 1.6</a> <br>
|
|
<!--
|
|
<a href="Glossary.html">Glossary</a><br>
|
|
-->
|
|
</td>
|
|
<td valign=top align=right>
|
|
And in this document, the
|
|
<a href="H5.user.html"><strong>HDF5 User's Guide from Release 1.4.5:</strong></a>
|
|
<br>
|
|
<a href="Files.html">Files</a>
|
|
<a href="Datasets.html">Datasets</a>
|
|
<a href="Datatypes.html">Datatypes</a>
|
|
<a href="Dataspaces.html">Dataspaces</a>
|
|
<a href="Groups.html">Groups</a>
|
|
<br>
|
|
<a href="References.html">References</a>
|
|
<a href="Attributes.html">Attributes</a>
|
|
<a href="Properties.html">Property Lists</a>
|
|
<a href="Errors.html">Error Handling</a>
|
|
<br>
|
|
<a href="Filters.html">Filters</a>
|
|
<a href="Caching.html">Caching</a>
|
|
<a href="Chunking.html">Chunking</a>
|
|
<a href="MountingFiles.html">Mounting Files</a>
|
|
<br>
|
|
<a href="Performance.html">Performance</a>
|
|
<a href="Debugging.html">Debugging</a>
|
|
<a href="Environment.html">Environment</a>
|
|
<a href="ddl.html">DDL</a>
|
|
</td></tr>
|
|
</table>
|
|
</center>
|
|
<hr>
|
|
<!-- #EndLibraryItem --><h1>The Reference Interface (H5R) and <br> the Identifier Interface (H5I)</h1>
|
|
|
|
<h2>1. Introduction</h2>
|
|
|
|
This document discusses the kinds of references implemented
|
|
(and planned) in HDF5 and the functions implemented (and planned)
|
|
to support them.
|
|
|
|
|
|
<h2>2. References</h2>
|
|
|
|
This section contains an overview of the kinds of references
|
|
implemented, or planned for implementation, in HDF5.
|
|
|
|
<p>
|
|
|
|
<dl>
|
|
<dt>Object reference
|
|
<dd>Reference to an entire object in the current HDF5 file.
|
|
<p>
|
|
An object reference points to an entire object in the
|
|
current HDF5 file by storing the relative file address
|
|
(OID) of the object header for the object pointed to.
|
|
The relative file address of an object header is
|
|
constant for the life of the object.
|
|
An object reference is of a fixed size in the file.
|
|
<p>
|
|
<dt>Dataset region reference
|
|
<dd>Reference to a specific dataset region.
|
|
<p>
|
|
A dataset region reference points to a region of a
|
|
dataset in the current HDF5 file by storing the OID
|
|
of the dataset and the global heap offset of the
|
|
region referenced. The region referenced is located
|
|
by retrieving the coordinates of the areas in the
|
|
region from the global heap. A dataset region
|
|
reference is of a variable size in the file.
|
|
</dl>
|
|
|
|
|
|
<b>Note:</b> All references are treated as soft links for the
|
|
purposes of reference counting. The library does not keep track of
|
|
reference links and they may dangle if the object they refer to
|
|
is deleted, moved, or not yet available.
|
|
|
|
|
|
<h2>3. Reference Types</h2>
|
|
|
|
Valid HDF5 reference types for use in the H5R functions
|
|
are as follows:
|
|
|
|
<center>
|
|
<table>
|
|
<tr><th align=left>Reference Type</th><th align=left>Value </th><th align=left>Description</th></tr>
|
|
<!-- NOT USER-LEVEL INFORMATION; DELETED FROM HDF5 USER'S GUIDE
|
|
<tr><td><code>H5R_BADTYPE</code></td>
|
|
<td align=right><code>-1 </code></td>
|
|
<td>Invalid reference type</td></tr>
|
|
-->
|
|
<tr><td><code>H5R_OBJECT</code></td>
|
|
<td align=right><code>0 </code></td>
|
|
<td>Object reference</td></tr>
|
|
<tr><td><code>H5R_DATASET_REGION</code></td>
|
|
<td align=right><code>1 </code></td>
|
|
<td>Dataset region reference</td></tr>
|
|
</table>
|
|
</center>
|
|
|
|
|
|
<h2>4. Functions</h2>
|
|
|
|
Five functions, four in the H5R interface and one in the
|
|
H5I interface, have been implemented to support references.
|
|
The H5I function is also useful outside the context of references.
|
|
<p>
|
|
<dl>
|
|
<dt><em>herr_t</em> <code>H5Rcreate(</code><em>void *</em><code>reference,</code>
|
|
<em>hid_t</em> <code>loc_id,</code>
|
|
<em>const char *</em><code>name,</code>
|
|
<em>H5R_type_t</em> <code>type,</code>
|
|
<em>hid_t</em> <code>space_id)</code>
|
|
<dd><code>H5Rcreate</code> creates an object which is a
|
|
particular type of reference (specified with the
|
|
<code>type</code> parameter) to some file object and/or
|
|
location specified with the <code>space_id</code> parameter.
|
|
For dataset region references, the selection specified
|
|
in the dataspace is the portion of the dataset which
|
|
will be referred to.
|
|
<p>
|
|
|
|
<dt><em>hid_t</em> <code>H5Rdereference(</code><em>hid_t</em> <code>dset,</code>
|
|
<em>H5R_type_t</em> <code>rtype,</code>
|
|
<em>void *</em><code>reference)</code>
|
|
<dd><code>H5Rdereference</code> opens the object referenced
|
|
and returns an identifier for that object.
|
|
The parameter <code>reference</code> specifies a reference of
|
|
type <code>rtype</code> that is stored in the dataset
|
|
<code>dset</code>.
|
|
<p>
|
|
|
|
<dt><em>int</em> <code>H5Rget_object_type(</code><em>hid_t</em> <code>obj_id,</code>
|
|
<em>void *</em><code>reference)</code>
|
|
<dd><code>H5Rget_object_type</code> retrieves the type of object
|
|
that an object reference points to.
|
|
The parameter <code>obj_id</code> specifies the dataset
|
|
containing the reference object or the location identifier
|
|
of the object that the dataset is located within.
|
|
The parameter <code>reference</code> specifies the
|
|
reference being queried.
|
|
<p>
|
|
|
|
<dt><em>H5S_t</em> <code>H5Rget_region(</code><em>H5D_t</em> <code>dataset,</code>
|
|
<em>H5R_type_t</em> <code>type,</code>
|
|
<em>void *</em><code>reference)</code>
|
|
<dd><code>H5Rget_region</code> creates a copy of dataspace of
|
|
the dataset that is pointed to and defines a selection in
|
|
the copy which is the location (or region) pointed to.
|
|
The parameter <code>ref</code> specifies a reference of
|
|
type <code>rtype</code> that is stored in the dataset
|
|
<code>dset</code>.
|
|
<p>
|
|
|
|
<dt><em>H5I_type_t</em> <code>H5Iget_type(</code><em>hid_t</em> <code>id)</code>
|
|
<dd>Returns the type of object referred to by the
|
|
identifier <code>id</code>. Valid return values appear
|
|
in the following list:
|
|
<center>
|
|
<table>
|
|
<tr valign=bottom><td><code>H5I_FILE</code></td>
|
|
<td>File objects</td></tr>
|
|
<tr valign=bottom><td><code>H5I_GROUP</code></td>
|
|
<td>Group objects</td></tr>
|
|
<tr valign=bottom><td><code>H5I_DATATYPE</code></td>
|
|
<td>Datatype objects</td></tr>
|
|
<tr valign=bottom><td><code>H5I_DATASPACE</code></td>
|
|
<td>Dataspace objects</td></tr>
|
|
<tr valign=bottom><td><code>H5I_DATASET</code></td>
|
|
<td>Dataset objects</td></tr>
|
|
<tr valign=bottom><td><code>H5I_ATTR</code></td>
|
|
<td>Attribute objects</td></tr>
|
|
</table>
|
|
</center>
|
|
<p>
|
|
This function was inspired by the need of users to figure
|
|
out which type of object closing function
|
|
(<code>H5Dclose</code>, <code>H5Gclose</code>, etc.)
|
|
to call after a call to <code>H5Rdereference</code>,
|
|
but it is also of general use.
|
|
<p>
|
|
</dl>
|
|
|
|
|
|
|
|
<h2>5. Examples</h2>
|
|
|
|
<b>Object Reference Writing Example</b>
|
|
<br>
|
|
Create a dataset which has links to other datasets as part
|
|
of its raw data and write the dataset to the file.
|
|
<p>
|
|
|
|
<pre>
|
|
{
|
|
hid_t file1;
|
|
hid_t dataset1;
|
|
hid_t datatype, dataspace;
|
|
char buf[128];
|
|
hobj_ref_t link;
|
|
hobj_ref_t data[10][10];
|
|
int rank;
|
|
size_t dimsf[2];
|
|
int i, j;
|
|
|
|
/* Open the file */
|
|
file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT);
|
|
|
|
/* Describe the size of the array and create the data space */
|
|
rank=2;
|
|
dimsf[0] = 10;
|
|
dimsf[1] = 10;
|
|
dataspace = H5Screate_simple(rank, dimsf, NULL);
|
|
|
|
/* Define datatype */
|
|
datatype = H5Tcopy(H5T_STD_REF_OBJ);
|
|
|
|
/* Create a dataset */
|
|
dataset1=H5Dcreate(file1,"Dataset One",datatype,dataspace,H5P_DEFAULT);
|
|
|
|
/* Construct array of OIDs for other datasets in the file */
|
|
/* somewhat hokey and artificial, but demonstrates the point */
|
|
for(i=0; i<10; i++)
|
|
for(j=0; j<10; j++)
|
|
{
|
|
sprintf(buf,"/Group/Linked Set %d-%d",i,j);
|
|
if(H5Rcreate(&link,file1,buf,H5R_OBJECT,-1)>0)
|
|
data[i][j]=link;
|
|
} /* end for */
|
|
|
|
/* Write the data to the dataset using default transfer properties. */
|
|
H5Dwrite(dataset, H5T_STD_REF_OBJ, H5S_ALL, H5S_ALL, H5P_DEFAULT, data);
|
|
|
|
/* Close everything */
|
|
H5Sclose(dataspace);
|
|
H5Tclose(datatype);
|
|
H5Dclose(dataset1);
|
|
H5Fclose(file1);
|
|
}
|
|
</pre>
|
|
|
|
|
|
<b>Object Reference Reading Example</b>
|
|
<br>
|
|
Open a dataset which has links to other datasets as part of
|
|
its raw data and read in those links.
|
|
<p>
|
|
|
|
<pre>
|
|
{
|
|
hid_t file1;
|
|
hid_t dataset1, tmp_dset;
|
|
href_t data[10][10];
|
|
int i, j;
|
|
|
|
/* Open the file */
|
|
file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT);
|
|
|
|
/* Open the dataset */
|
|
dataset1=H5Dopen(file1,"Dataset One",H5P_DEFAULT);
|
|
|
|
/*
|
|
* Read the data to the dataset using default transfer properties.
|
|
* (we are assuming the dataset is the same and not querying the
|
|
* dimensions, etc.)
|
|
*/
|
|
H5Dread(dataset, H5T_STD_REF_OBJ, H5S_ALL, H5S_ALL, H5P_DEFAULT, data);
|
|
|
|
/* Analyze array of OIDs of linked datasets in the file */
|
|
/* somewhat hokey and artificial, but demonstrates the point */
|
|
for(i=0; i<10; i++)
|
|
for(j=0; j<10; i++)
|
|
{
|
|
if((tmp_dset=H5Rdereference(dataset, H5T_STD_REF_OBJ, data[i][j]))>0)
|
|
{
|
|
<perform operations on linked dataset>
|
|
} /* end if */
|
|
H5Dclose(tmp_dset);
|
|
} /* end for */
|
|
|
|
|
|
/* Close everything */
|
|
H5Dclose(dataset1);
|
|
H5Fclose(file1);
|
|
}
|
|
</pre>
|
|
|
|
|
|
<b>Dataset Region Reference Writing Example</b>
|
|
<br>
|
|
Create a dataset which has links to other dataset regions
|
|
(single elements in this case) as part of its raw data and
|
|
write the dataset to the file.
|
|
<p>
|
|
|
|
<pre>
|
|
{
|
|
hid_t file1;
|
|
hid_t dataset1, dataset2;
|
|
hid_t datatype, dataspace1, dataspace2;
|
|
char buf[128];
|
|
href_t link;
|
|
href_t data[10][10]; /* HDF5 reference type */
|
|
int rank;
|
|
size_t dimsf[2];
|
|
hssize_t start[3],count[3];
|
|
int i, j;
|
|
|
|
/* Open the file */
|
|
file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT);
|
|
|
|
/* Describe the size of the array and create the data space */
|
|
rank=2;
|
|
dimsf[0] = 10;
|
|
dimsf[1] = 10;
|
|
dataspace1 = H5Screate_simple(rank, dimsf, NULL);
|
|
|
|
/* Define Dataset Region Reference datatype */
|
|
datatype = H5Tcopy(H5T_STD_REF_DATAREG);
|
|
|
|
/* Create a dataset */
|
|
dataset1=H5Dcreate(file1,"Dataset One",datatype,dataspace1,H5P_DEFAULT);
|
|
|
|
/* Construct array of OIDs for other datasets in the file */
|
|
/* (somewhat artificial, but demonstrates the point) */
|
|
for(i=0; i<10; i++)
|
|
for(j=0; j<10; i++)
|
|
{
|
|
sprintf(buf,"/Group/Linked Set %d-%d",i,j);
|
|
|
|
/* Get the dataspace for the object to point to */
|
|
dataset2=H5Dopen(file1,buf,H5P_DEFAULT);
|
|
dataspace2=H5Dget_space(dataspace2);
|
|
|
|
/* Select the region to point to */
|
|
/* (could be different region for each pointer) */
|
|
start[0]=5; start[1]=4; start[2]=3;
|
|
count[0]=2; count[1]=4; count[2]=1;
|
|
H5Sselect_hyperslab(dataspace2,H5S_SELECT_SET,start,NULL,count,NULL);
|
|
|
|
if(H5Rcreate(&link,file1,buf,H5R_REF_DATAREG,dataspace2)>0)
|
|
/* Store the reference */
|
|
data[i][j]=link;
|
|
|
|
H5Sclose(dataspace2);
|
|
H5Dclose(dataspace2);
|
|
} /* end for */
|
|
|
|
/* Write the data to the dataset using default transfer properties. */
|
|
H5Dwrite(dataset, H5T_STD_REF_DATAREG, H5S_ALL, H5S_ALL, H5P_DEFAULT, data);
|
|
|
|
/* Close everything */
|
|
H5Sclose(dataspace);
|
|
H5Tclose(datatype);
|
|
H5Dclose(dataset1);
|
|
H5Fclose(file1);
|
|
}
|
|
</pre>
|
|
|
|
|
|
<b>Dataset Region Reference Reading Example</b>
|
|
<br>
|
|
Open a dataset which has links to other datasets regions
|
|
(single elements in this case) as part of its raw data and
|
|
read in those links.
|
|
<p>
|
|
|
|
<pre>
|
|
{
|
|
hid_t file1;
|
|
hid_t dataset1, tmp_dset;
|
|
hid_t dataspace;
|
|
href_t data[10][10]; /* HDF5 reference type */
|
|
int i, j;
|
|
|
|
/* Open the file */
|
|
file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT);
|
|
|
|
/* Open the dataset */
|
|
dataset1=H5Dopen(file1,"Dataset One",H5P_DEFAULT);
|
|
|
|
/*
|
|
* Read the data to the dataset using default transfer properties.
|
|
* (we are assuming the dataset is the same and not querying the
|
|
* dimensions, etc.)
|
|
*/
|
|
H5Dread(dataset, H5T_STD_REF_DATAREG, H5S_ALL, H5S_ALL, H5P_DEFAULT, data);
|
|
|
|
/* Analyze array of OIDs of linked datasets in the file */
|
|
/* (somewhat artificial, but demonstrates the point) */
|
|
for(i=0; i<10; i++)
|
|
for(j=0; j<10; i++)
|
|
{
|
|
if((tmp_dset=H5Rdereference(dataset, H5D_STD_REF_DATAREG,data[i][j]))>0)
|
|
{
|
|
/* Get the dataspace with the pointed to region selected */
|
|
dataspace=H5Rget_space(data[i][j]);
|
|
|
|
<perform operation on linked dataset region>
|
|
|
|
H5Sclose(dataspace);
|
|
} /* end if */
|
|
H5Dclose(tmp_dset);
|
|
} /* end for */
|
|
|
|
|
|
/* Close everything */
|
|
H5Dclose(dataset1);
|
|
H5Fclose(file1);
|
|
}
|
|
</pre>
|
|
<!--
|
|
|
|
<h1>Material to Be Omitted!!!</h1>
|
|
|
|
Additional material above will also need to be deleted or
|
|
commented out.
|
|
<p>
|
|
|
|
<h2>"Kinds of Reference" Information</h2>
|
|
|
|
<dl>
|
|
<dt>Dataset Offset Reference
|
|
<dd>Reference to a specific byte sequence in a dataset (3)
|
|
<dt>Disk Offset Reference
|
|
<dd>Reference to a specific byte sequence in a file (3)
|
|
<dt>External Object Reference
|
|
<dd>Reference to an entire object in another HDF5 file (3)
|
|
<dt>External Dataset Region Reference
|
|
<dd>Reference an a specific dataset region in another HDF5 file (3)
|
|
<dt>External Dataset Offset Reference
|
|
<dd>Reference to a specific byte sequence in a dataset in
|
|
another HDF5 file (3)
|
|
<dt>External Disk Offset Reference
|
|
<dd>Reference to a specific byte sequence in another HDF5 file (3)
|
|
<dt>Generic Reference
|
|
<dd>A reference which may be any of the types defined above. (3)
|
|
</dl>
|
|
|
|
Notes:
|
|
<ul>
|
|
<li>1 - Planned for in final release.
|
|
<li>2 - Most useful reference types to tackle next
|
|
<li>3 - Optional reference types.
|
|
</ul>
|
|
|
|
<h2>Comments</h2>
|
|
<pre>
|
|
Reference types are atomic types and may be included as fields in compound
|
|
datatypes.
|
|
|
|
There are (at least) three levels of reference strength:
|
|
Weak - We allow the user to store any type of reference in an array
|
|
of references. (u.e., the array of references in the example above
|
|
could be a mix of Object, Dataset Region and Internal references)
|
|
Medium - We force the user to stick with a particular type of
|
|
reference within a dataset, but the datasets pointed to (with
|
|
Object and Dataset Region references) may be of any datatype
|
|
or dataspace.
|
|
Strong - We force the user to stick with a particular type of
|
|
reference and Object and Dataset Region references must point to
|
|
datasets with the same datatype.
|
|
Extra Strong - We force the user to stick with a particular type of
|
|
reference and Object and Dataset Region references must point to
|
|
datasets with the same datatype <i>and</i> dataspace.
|
|
|
|
The library is currently implemented with "medium" strength references.
|
|
</pre>
|
|
|
|
|
|
<h2>Reference Type</h2>
|
|
|
|
<center>
|
|
<table>
|
|
<tr><td><code>H5R_MAXTYPE</code></td>
|
|
<td align=right><code>3 </code></td>
|
|
<td>Highest type in group (invalid as true type)</td></tr>
|
|
</table>
|
|
</center>
|
|
|
|
|
|
<h2>Information Regarding Specific Kinds of References</h2>
|
|
|
|
<dl>
|
|
<dt>Dataset Offset Reference
|
|
<dd>Points to a sequence of bytes within a dataset in
|
|
the current HDF5 file by storing the OID of the dataset and the byte
|
|
length and offset of the sequence within the dataset. The offset is
|
|
the logical byte offset within the dataset, meaning that the data is
|
|
de-compressed before returning the sequence of bytes requested. No
|
|
interpretation of the data at that location is provided. However,
|
|
if the dataset is extendible and the size of the dimensions are changed,
|
|
the element(s) that the sequence is located within may vary. Fixed size
|
|
in file.
|
|
|
|
<dt>Disk Offset Reference
|
|
<dd>Points to a sequence of bytes in the current
|
|
HDF5 file by storing the byte length and offset of the sequence within
|
|
the file, relative to the super block (as are all the other high-level
|
|
addresses used in the file). The offset is the absolute byte offset
|
|
within the file, no interpretation of the data at that location is
|
|
provided. Fixed size in file.
|
|
|
|
<dt>External Object Reference
|
|
<dd>Points to an entire object in another HDF5 file by
|
|
storing a global heap offset which points to the URL of the external
|
|
file and the OID of the object pointed to. Variable size in file.
|
|
|
|
<dt>External Dataset Region Reference
|
|
<dd>Points to a region of a dataset in
|
|
another HDF5 file by storing a global heap offset which points to the
|
|
URL of the external file, OID of the dataset and the coordinates of the
|
|
region. Variable size in file.
|
|
|
|
<dt>External Dataset Offset Reference
|
|
<dd>Points to a sequence of bytes within a
|
|
dataset in another HDF5 file by storing a global heap offset which
|
|
points to the URL of the external file, the OID of the dataset and the
|
|
byte length and offset of the sequence within the dataset. The offset
|
|
is the logical byte offset within the dataset, meaning that the data is
|
|
de-compressed before returning the sequence of bytes requested.
|
|
However, if the dataset is not stored contiguously and the size of the
|
|
dimensions are changed, the element(s) that the sequence is located
|
|
within may vary. Variable size in file.
|
|
|
|
<dt>External Disk Offset Reference
|
|
<dd>Points to a sequence of bytes in another
|
|
HDF5 file by storing a global heap reference which points to the URL
|
|
of the external file and the byte length and offset of the sequence
|
|
within the file. The offset is the absolute byte offset within the
|
|
file, no interpretation of the data at that location is provided.
|
|
Variable size in file.
|
|
|
|
<dt>Generic Reference
|
|
<dd>A reference which may contain any of the other
|
|
references defined above. (Mostly useful for implementing "weak"
|
|
strength pointers within the medium strength model we are using)
|
|
Variable size in file.
|
|
|
|
</dl>
|
|
|
|
<h2>Implementation Details</h2>
|
|
|
|
<dl>
|
|
<dt>File Storage
|
|
<dd>In order to efficiently index an array, each element must be the
|
|
same size when stored in the dataset on disk. Fixed-sized references
|
|
will be stored directly in the dataset array on disk; variable-sized
|
|
references will have a fixed-size head offset stored in the array on
|
|
disk with a file heap used to store the actual variable-sized
|
|
information stored in the heap.
|
|
|
|
<dt>Memory Storage
|
|
<dd>Each <code>href_t</code> object in memory is a struct containing
|
|
a pointer type and union of information required for each
|
|
pointer type.
|
|
Information in this structure is not designed for users to view.
|
|
Non-C APIs may have to mangle this structure in some way, in order
|
|
to provide users with access to references in a language-appropriate
|
|
way.
|
|
</dl>
|
|
|
|
-->
|
|
|
|
|
|
<!-- #BeginLibraryItem "/ed_libs/NavBar_UG.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="RM_H5Front.html">HDF5 Reference Manual</a> <br>
|
|
<a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User's Guide for Release 1.6</a> <br>
|
|
<!--
|
|
<a href="Glossary.html">Glossary</a><br>
|
|
-->
|
|
</td>
|
|
<td valign=top align=right>
|
|
And in this document, the
|
|
<a href="H5.user.html"><strong>HDF5 User's Guide from Release 1.4.5:</strong></a>
|
|
<br>
|
|
<a href="Files.html">Files</a>
|
|
<a href="Datasets.html">Datasets</a>
|
|
<a href="Datatypes.html">Datatypes</a>
|
|
<a href="Dataspaces.html">Dataspaces</a>
|
|
<a href="Groups.html">Groups</a>
|
|
<br>
|
|
<a href="References.html">References</a>
|
|
<a href="Attributes.html">Attributes</a>
|
|
<a href="Properties.html">Property Lists</a>
|
|
<a href="Errors.html">Error Handling</a>
|
|
<br>
|
|
<a href="Filters.html">Filters</a>
|
|
<a href="Caching.html">Caching</a>
|
|
<a href="Chunking.html">Chunking</a>
|
|
<a href="MountingFiles.html">Mounting Files</a>
|
|
<br>
|
|
<a href="Performance.html">Performance</a>
|
|
<a href="Debugging.html">Debugging</a>
|
|
<a href="Environment.html">Environment</a>
|
|
<a href="ddl.html">DDL</a>
|
|
</td></tr>
|
|
</table>
|
|
</center>
|
|
<hr>
|
|
<!-- #EndLibraryItem --><!-- #BeginLibraryItem "/ed_libs/Footer.lbi" --><address>
|
|
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
|
|
<br>
|
|
Describes HDF5 Release 1.4.5, February 2003
|
|
</address><!-- #EndLibraryItem -->
|
|
|
|
Last modified: 2 August 2004
|
|
|
|
</body>
|
|
</html>
|