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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<!-- saved from url=(0072)https://gamma.hdfgroup.org/papers/HISS/030515.FileFormat/FileFormat.html -->
<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>HDF5 File Format Discussion</title>
<meta name="author" content="Quincey Koziol">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<style type="text/css">
OL.loweralpha { list-style-type: lower-alpha }
OL.upperroman { list-style-type: upper-roman }
</style>
<style type="text/css">
TD CAPTION EM { color: red }
TD EM { color: blue }
TABLE CAPTION STRONG { font-size: larger }
</style>
<center><h1>HDF5 File Format Discussion</h1></center>
<center><h3>Quincey Koziol<br>
koziol@ncsa.uiuc.edu<br>
May 15, 2003
</h3></center>
<ol class="upperroman">
<li><h3><u>Document's Audience:</u></h3>
<ul>
<li>Current H5 library designers and knowledgeable external developers.</li>
</ul>
</li><li><h3><u>Background Reading:</u></h3>
<dl>
<dt><a href="https://hdfgroup.github.io/hdf5/develop/_s_p_e_c.html">HDF5 File Format Specification</a>
</dt><dd>This describes the current HDF5 file format.
</dd></dl>
</li><li><h3><u>Introduction:</u></h3>
<dl>
<dt><strong>What is this document about?</strong></dt>
<dd>This document attempts to explain the HDF5 file format
specification with a few examples and describes some potential
improvements to the format specification.
</dd> <br>
</dl>
</li><li><h3><u>File Format Examples:</u></h3>
<p>This section has several small programs and describes the format of a file
created with each of them.
</p>
<p>Example program one - <em>Create an empty file</em>:
</p><pre> <code>
#include "hdf5.h"
#include <assert.h>
int main()
{
hid_t fid; /* File ID */
herr_t ret; /* Generic return value */
/* Create the file */
fid=H5Fcreate("example1.h5", H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
assert(fid&gt;=0);
/* Close the file */
ret=H5Fclose(fid);
assert(ret&gt;=0);
return(0);
}
</assert.h></code> </pre>
<center>
<table border="" align="center" cellpadding="4" width="80%">
<caption align="top">
<strong>Super Block</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr>
<tr align="center">
<td>\211</td>
<td>'H'</td>
<td>'D'</td>
<td>'F'</td>
</tr>
<tr align="center">
<td>\r</td>
<td>\n</td>
<td>\032</td>
<td>\n</td>
</tr>
<tr align="center">
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
</tr>
<tr align="center">
<td>0</td>
<td>8</td>
<td>8</td>
<td>0</td>
</tr>
<tr align="center">
<td colspan="2">4</td>
<td colspan="2">16</td>
</tr>
<tr align="center">
<td colspan="4">0x00000003</td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr>
<tr align="center">
<td colspan="4">?</td>
</tr>
<tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr>
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<tbody><tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4"><br>928<br><br></td>
</tr>
<tr align="center">
<td colspan="4">H5G_CACHED_STAB (1)</td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<tbody><tr align="center">
<td colspan="4"><br>384<br><br></td>
</tr>
<tr align="center">
<td colspan="4"><br>96<br><br></td>
</tr>
</tbody></table>
</td>
</tr>
</tbody></table>
</td>
</tr>
</tbody></table>
</center>
<br>
<pre> <code>
%h5debug example1.h5
Reading signature at address 0 (rel)
File Super Block...
File name: example1.h5
File access flags 0x00000000
File open reference count: 1
Address of super block: 0 (abs)
Size of user block: 0 bytes
Super block version number: 0
Free list version number: 0
Root group symbol table entry version number: 0
Shared header version number: 0
Size of file offsets (haddr_t type): 8 bytes
Size of file lengths (hsize_t type): 8 bytes
Symbol table leaf node 1/2 rank: 4
Symbol table internal node 1/2 rank: 16
File consistency flags: 0x00000003
Base address: 0 (abs)
Free list address: UNDEF (rel)
Address of driver information block: UNDEF (rel)
Root group symbol table entry:
Name offset into private heap: 0
Object header address: 928
Dirty: Yes
Cache info type: Symbol Table
Cached information:
B-tree address: 384
Heap address: 96
</code> </pre>
<center>
<table border="" cellpadding="4" width="80%">
<caption align="top">
<strong>Root Group Object Header</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr>
<tr align="center">
<td colspan="1" width="25%">1</td>
<td colspan="1" width="25%">0</td>
<td colspan="2" width="50%">2</td>
</tr>
<tr align="center">
<td colspan="4">1</td>
</tr>
<tr align="center">
<td colspan="4">32</td>
</tr>
<tr align="center">
<td colspan="2">0x0011</td>
<td colspan="2">16</td>
</tr>
<tr align="center">
<td>0x01</td>
<td colspan="3">0</td>
</tr>
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<tbody><tr align="center">
<td colspan="4"><br>384<br><br></td>
</tr>
<tr align="center">
<td colspan="4"><br>96<br><br></td>
</tr>
</tbody></table>
</td>
</tr>
<tr align="center">
<td colspan="2">0</td>
<td colspan="2">0</td>
</tr>
<tr align="center">
<td>0x00</td>
<td colspan="3">0</td>
</tr>
</tbody></table>
</center>
<br>
<pre> <code>
%h5debug example1.h5 928
New address: 928
Reading signature at address 928 (rel)
Object Header...
Dirty: 0
Version: 1
Header size (in bytes): 16
Number of links: 1
Number of messages (allocated): 2 (32)
Number of chunks (allocated): 1 (8)
Chunk 0...
Dirty: 0
Address: 944
Size in bytes: 32
Message 0...
Message ID (sequence number): 0x0011 stab(0)
Shared message: No
Constant: Yes
Raw size in obj header: 16 bytes
Chunk number: 0
Message Information:
B-tree address: 384
Name heap address: 96
Message 1...
Message ID (sequence number): 0x0000 null(0)
Shared message: No
Constant: No
Raw size in obj header: 0 bytes
Chunk number: 0
Message Information:
<no info="" for="" this="" message="">
</no></code> </pre>
<center>
<table border="" cellpadding="4" width="80%">
<caption align="top">
<strong>Root Group Local Heap</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr>
<tr align="center">
<td>'H'</td>
<td>'E'</td>
<td>'A'</td>
<td>'P'</td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4">256</td>
</tr>
<tr align="center">
<td colspan="4">8</td>
</tr>
<tr align="center">
<td colspan="4">128</td>
</tr>
</tbody></table>
</center>
<br>
<pre> <code>
%h5debug example1.h5 96
New address: 96
Reading signature at address 96 (rel)
Local Heap...
Dirty: 0
Header size (in bytes): 32
Address of heap data: 128
Data bytes allocated on disk: 256
Data bytes allocated in core: 256
Free Blocks (offset, size):
Block #0: 8, 248
Percent of heap used: 3.12%
Data follows (`__' indicates free region)...
0: 00 00 00 00 00 00 00 00 __ __ __ __ __ __ __ __ ........
16: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
32: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
48: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
64: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
80: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
96: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
112: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
128: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
144: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
160: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
176: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
192: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
208: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
224: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
240: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
</code> </pre>
<center>
<table border="" cellpadding="4" width="80%">
<caption align="top">
<strong>Root Group B-tree</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr><tr align="center">
<td>'T'</td>
<td>'R'</td>
<td>'E'</td>
<td>'E'</td>
</tr><tr align="center">
<td>0</td>
<td>0</td>
<td colspan="2">0</td>
</tr><tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr><tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr></tbody></table>
</center>
<br>
<pre> <code>
%h5debug example1.h5 384 96
New address: 384
Reading signature at address 384 (rel)
Tree type ID: H5B_SNODE_ID
Size of node: 544
Size of raw (disk) key: 8
Dirty flag: False
Number of initial dirty children: 0
Level: 0
Address of left sibling: UNDEF
Address of right sibling: UNDEF
Number of children (max): 0 (32)
</code> </pre>
<p></p>
<p>Example program two - <em>Create a file with a single dataset in it</em>:
</p><pre> <code>
#include "hdf5.h"
#include <assert.h>
int main()
{
hid_t fid; /* File ID */
hid_t sid; /* Dataspace ID */
hid_t did; /* Dataset ID */
herr_t ret; /* Generic return value */
/* Create the file */
fid=H5Fcreate("example2.h5", H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
assert(fid&gt;=0);
/* Create a scalar dataspace for the dataset */
sid=H5Screate(H5S_SCALAR);
assert(sid&gt;=0);
/* Create a trivial dataset */
did=H5Dcreate(fid, "Dataset", H5T_NATIVE_INT, sid, H5P_DEFAULT);
assert(did&gt;=0);
/* Close the dataset */
ret=H5Dclose(did);
assert(ret&gt;=0);
/* Close the dataspace */
ret=H5Sclose(sid);
assert(ret&gt;=0);
/* Close the file */
ret=H5Fclose(fid);
assert(ret&gt;=0);
return(0);
}
</assert.h></code> </pre>
<center>
<table border="" align="center" cellpadding="4" width="80%">
<caption align="top">
<strong>Super Block</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr>
<tr align="center">
<td>\211</td>
<td>'H'</td>
<td>'D'</td>
<td>'F'</td>
</tr>
<tr align="center">
<td>\r</td>
<td>\n</td>
<td>\032</td>
<td>\n</td>
</tr>
<tr align="center">
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
</tr>
<tr align="center">
<td>0</td>
<td>8</td>
<td>8</td>
<td>0</td>
</tr>
<tr align="center">
<td colspan="2">4</td>
<td colspan="2">16</td>
</tr>
<tr align="center">
<td colspan="4">0x00000003</td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr>
<tr align="center">
<td colspan="4">?</td>
</tr>
<tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr>
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<tbody><tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4"><br>928<br><br></td>
</tr>
<tr align="center">
<td colspan="4">H5G_CACHED_STAB (1)</td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<tbody><tr align="center">
<td colspan="4"><br>384<br><br></td>
</tr>
<tr align="center">
<td colspan="4"><br>96<br><br></td>
</tr>
</tbody></table>
</td>
</tr>
</tbody></table>
</td>
</tr>
</tbody></table>
</center>
<br>
<pre> <code>
%h5debug example2.h5
Reading signature at address 0 (rel)
File Super Block...
File name: example2.h5
File access flags 0x00000000
File open reference count: 1
Address of super block: 0 (abs)
Size of user block: 0 bytes
Super block version number: 0
Free list version number: 0
Root group symbol table entry version number: 0
Shared header version number: 0
Size of file offsets (haddr_t type): 8 bytes
Size of file lengths (hsize_t type): 8 bytes
Symbol table leaf node 1/2 rank: 4
Symbol table internal node 1/2 rank: 16
File consistency flags: 0x00000003
Base address: 0 (abs)
Free list address: UNDEF (rel)
Address of driver information block: UNDEF (rel)
Root group symbol table entry:
Name offset into private heap: 0
Object header address: 928
Dirty: Yes
Cache info type: Symbol Table
Cached entry information:
B-tree address: 384
Heap address: 96
</code> </pre>
<center>
<table border="" cellpadding="4" width="80%">
<caption align="top">
<strong>Root Group Object Header</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr>
<tr align="center">
<td colspan="1" width="25%">1</td>
<td colspan="1" width="25%">0</td>
<td colspan="2" width="50%">2</td>
</tr>
<tr align="center">
<td colspan="4">1</td>
</tr>
<tr align="center">
<td colspan="4">32</td>
</tr>
<tr align="center">
<td colspan="2">0x0011</td>
<td colspan="2">16</td>
</tr>
<tr align="center">
<td>0x01</td>
<td colspan="3">0</td>
</tr>
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<tbody><tr align="center">
<td colspan="4"><br>384<br><br></td>
</tr>
<tr align="center">
<td colspan="4"><br>96<br><br></td>
</tr>
</tbody></table>
</td>
</tr>
<tr align="center">
<td colspan="2">0</td>
<td colspan="2">0</td>
</tr>
<tr align="center">
<td>0x00</td>
<td colspan="3">0</td>
</tr>
</tbody></table>
</center>
<br>
<pre> <code>
%h5debug example2.h5 928
New address: 928
Reading signature at address 928 (rel)
Object Header...
Dirty: 0
Version: 1
Header size (in bytes): 16
Number of links: 1
Number of messages (allocated): 2 (32)
Number of chunks (allocated): 1 (8)
Chunk 0...
Dirty: 0
Address: 944
Size in bytes: 32
Message 0...
Message ID: 0x0011 stab(0)
Shared message: No
Constant: Yes
Raw size in obj header: 16 bytes
Chunk number: 0
Message Information:
B-tree address: 384
Name heap address: 96
Message 1...
Message ID: 0x0000 null(0)
Shared message: No
Constant: No
Raw size in obj header: 0 bytes
Chunk number: 0
Message Information:
<no info="" for="" this="" message="">
</no></code> </pre>
<center>
<table border="" cellpadding="4" width="80%">
<caption align="top">
<strong>Root Group Local Heap</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr>
<tr align="center">
<td>'H'</td>
<td>'E'</td>
<td>'A'</td>
<td>'P'</td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4">256</td>
</tr>
<tr align="center">
<td colspan="4">16</td>
</tr>
<tr align="center">
<td colspan="4">128</td>
</tr>
</tbody></table>
</center>
<br>
<pre> <code>
%h5debug example2.h5 96
New address: 96
Reading signature at address 96 (rel)
Local Heap...
Dirty: 0
Header size (in bytes): 32
Address of heap data: 128
Data bytes allocated on disk: 256
Data bytes allocated in core: 256
Free Blocks (offset, size):
Block #0: 16, 240
Percent of heap used: 6.25%
Data follows (`__' indicates free region)...
0: 00 00 00 00 00 00 00 00 44 61 74 61 73 65 74 00 ........Dataset.
16: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
32: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
48: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
64: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
80: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
96: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
112: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
128: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
144: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
160: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
176: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
192: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
208: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
224: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
240: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
</code> </pre>
<center>
<table border="" cellpadding="4" width="80%">
<caption align="top">
<strong>Root Group B-tree</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr><tr align="center">
<td>'T'</td>
<td>'R'</td>
<td>'E'</td>
<td>'E'</td>
</tr><tr align="center">
<td>0</td>
<td>0</td>
<td colspan="2">1</td>
</tr><tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr><tr align="center">
<td colspan="4"><br>0xffffffffffffffff<br><br></td>
</tr><tr align="center">
<td colspan="4"><br>0<br><br></td>
</tr><tr align="center">
<td colspan="4"><br>1248<br><br></td>
</tr><tr align="center">
<td colspan="4"><br>8<br><br></td>
</tr></tbody></table>
</center>
<br>
<pre> <code>
%h5debug example2.h5 384 96
New address: 384
Reading signature at address 384 (rel)
Tree type ID: H5B_SNODE_ID
Size of node: 544
Size of raw (disk) key: 8
Dirty flag: False
Number of initial dirty children: 0
Level: 0
Address of left sibling: UNDEF
Address of right sibling: UNDEF
Number of children (max): 1 (32)
Child 0...
Address: 1248
Left Key:
Heap offset: 0
Name :
Right Key:
Heap offset: 8
Name : Dataset
</code> </pre>
<center>
<table border="" cellpadding="4" width="80%">
<caption align="top">
<strong>Root Group B-tree Symbol Table Node</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr><tr align="center">
<td>'S'</td>
<td>'N'</td>
<td>'O'</td>
<td>'D'</td>
</tr><tr align="center">
<td>1</td>
<td>0</td>
<td colspan="2">1</td>
</tr><tr align="center">
<td colspan="4">
<table border="" width="100%">
<tbody><tr align="center">
<td colspan="4">8</td>
</tr>
<tr align="center">
<td colspan="4"><br>976<br><br></td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4">0</td>
</tr>
<tr align="center">
<td colspan="4"><br><br>0<br><br><br></td>
</tr>
</tbody></table>
</td>
</tr></tbody></table>
</center>
<br>
<pre> <code>
%h5debug example2.h5 1248 96
New address: 1248
Reading signature at address 1248 (rel)
Symbol Table Node...
Dirty: No
Size of Node (in bytes): 328
Number of Symbols: 1 of 8
Symbol 0:
Name: `Dataset'
Name offset into private heap: 8
Object header address: 976
Dirty: No
Cache info type: Nothing Cached
</code> </pre>
<center>
<table border="" cellpadding="4" width="90%">
<caption align="top">
<strong>'/Dataset' Object Header</strong>
</caption>
<tbody><tr align="center">
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
<th width="25%">byte</th>
</tr>
<tr align="center">
<td colspan="1"><em>Version:</em> 1</td>
<td colspan="1"><em>Reserved:</em> 0</td>
<td colspan="2"><em>Number of Header Messages:</em> 6</td>
</tr>
<tr align="center">
<td colspan="4"><em>Object Reference Count:</em> 1</td>
</tr>
<tr align="center">
<td colspan="4"><em>Total Object Header Size:</em> 256</td>
</tr>
<!-- Fill Value Header Message -->
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<caption align="top" color="#80FFFF">
<em>Fill Value Header Message</em>
</caption>
<tbody><tr align="center">
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
</tr>
<tr align="center">
<!-- Object Header Message Type -->
<td colspan="2"><em>Message Type:</em> 0x0005</td>
<!-- Object Header Message Length -->
<td colspan="2"><em>Message Data Size:</em> 8</td>
</tr>
<tr align="center">
<!-- Object Header Message Flags -->
<td colspan="1"><em>Flags:</em> 0x01</td>
<!-- Reserved -->
<td colspan="3"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Version -->
<td colspan="1"><em>Version:</em> 1</td>
<!-- Space Allocation Time -->
<td colspan="1"><em>Space Allocation Time:</em> 2 (Late)</td>
<!-- Fill Value Writing Time -->
<td colspan="1"><em>Fill Value Writing Time:</em> 0 (At allocation)</td>
<!-- Fill Value Defined -->
<td colspan="1"><em>Fill Value Defined:</em> 0 (Undefined)</td>
</tr>
<tr align="center">
<!-- Fill Value Datatype Size -->
<td colspan="4"><em>Fill Value Datatype Size:</em> 0 (Use dataset's datatype for fill-value datatype)</td>
</tr>
</tbody></table>
</td>
</tr>
<!-- Datatype Header Message -->
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<caption align="top">
<em>Datatype Header Message</em>
</caption>
<tbody><tr align="center">
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
</tr>
<tr align="center">
<!-- Object Header Message Type -->
<td colspan="2"><em>Message Type:</em> 0x0003</td>
<!-- Object Header Message Length -->
<td colspan="2"><em>Message Data Size:</em> 16</td>
</tr>
<tr align="center">
<!-- Object Header Message Flags -->
<td colspan="1"><em>Flags:</em> 0x01</td>
<!-- Reserved -->
<td colspan="3"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Type Class and Version -->
<td colspan="1">
<table border="" width="100%">
<tbody><tr align="center">
<td width="50%"><em>Version:</em> 0x1</td>
<td><em>Class:</em> 0x0 (Fixed-Point)</td>
</tr>
</tbody></table>
</td>
<!-- Class Bit Field -->
<td colspan="3"><em>Fixed-Point Bit-Field:</em> 0x08 (Little-endian, No padding, Signed)</td>
</tr>
<tr align="center">
<!-- Type Size (in bytes) -->
<td colspan="4"><em>Size:</em> 4</td>
</tr>
<tr align="center">
<!-- Bit Offset -->
<td colspan="2"><em>Bit Offset:</em> 0</td>
<!-- Bit Precision -->
<td colspan="2"><em>Bit Precision:</em> 32</td>
</tr>
<tr align="center">
<!-- Message alignment filler -->
<td colspan="4"><em>Message Alignment Filler:</em> -</td>
</tr>
</tbody></table>
</td>
</tr>
<!-- Dataspace Header Message -->
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<caption align="top">
<em>Dataspace Header Message</em>
</caption>
<tbody><tr align="center">
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
</tr>
<tr align="center">
<!-- Object Header Message Type -->
<td colspan="2"><em>Message Type:</em> 0x0001</td>
<!-- Object Header Message Length -->
<td colspan="2"><em>Message Data Size:</em> 8</td>
</tr>
<tr align="center">
<!-- Object Header Message Flags -->
<td colspan="1"><em>Flags:</em> 0x00</td>
<!-- Reserved -->
<td colspan="3"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Version -->
<td colspan="1"><em>Version:</em> 1</td>
<!-- Rank -->
<td colspan="1"><em>Rank:</em> 0 (Scalar)</td>
<!-- Flags -->
<td colspan="1"><em>Flags:</em> 0x00 (No maximum dimensions, no permutation information)</td>
<!-- Reserved -->
<td colspan="1"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Reserved -->
<td colspan="4"><em>Reserved:</em> 0</td>
</tr>
</tbody></table>
</td>
</tr>
<!-- Layout Header Message -->
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<caption align="top">
<em>Layout Header Message</em>
</caption>
<tbody><tr align="center">
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
</tr>
<tr align="center">
<!-- Object Header Message Type -->
<td colspan="2"><em>Message Type:</em> 0x0008</td>
<!-- Object Header Message Length -->
<td colspan="2"><em>Message Data Size:</em> 24</td>
</tr>
<tr align="center">
<!-- Object Header Message Flags -->
<td colspan="1"><em>Flags:</em> 0x00</td>
<!-- Reserved -->
<td colspan="3"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Version -->
<td colspan="1"><em>Version:</em> 1</td>
<!-- Rank -->
<td colspan="1"><em>Rank:</em> 1 (Dataspace rank+1)</td>
<!-- Class -->
<td colspan="1"><em>Class:</em> 1 (Contiguous)</td>
<!-- Reserved -->
<td colspan="1"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Reserved -->
<td colspan="4"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Address -->
<td colspan="4"><br><em>Address:</em> 0xffffffffffffffff (Undefined)<br><br></td>
</tr>
<tr align="center">
<!-- Layout Dimensions -->
<td colspan="4"><em>Dimension 0 Size:</em> 4 (Datatype size)</td>
</tr>
<tr align="center">
<!-- Message alignment filler -->
<td colspan="4"><em>Message Alignment Filler:</em> -</td>
</tr>
</tbody></table>
</td>
</tr>
<!-- Modification Date & Time Header Message -->
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<caption align="top">
<em>Modification Date &amp; Time Header Message</em>
</caption>
<tbody><tr align="center">
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
</tr>
<tr align="center">
<!-- Object Header Message Type -->
<td colspan="2"><em>Message Type:</em> 0x0012</td>
<!-- Object Header Message Length -->
<td colspan="2"><em>Message Data Size:</em> 8</td>
</tr>
<tr align="center">
<!-- Object Header Message Flags -->
<td colspan="1"><em>Flags:</em> 0x00</td>
<!-- Reserved -->
<td colspan="3"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Version -->
<td colspan="1"><em>Version:</em> 1</td>
<!-- Reserved -->
<td colspan="3"><em>Reserved:</em> 0</td>
</tr>
<tr align="center">
<!-- Modification time -->
<td colspan="4"><em>Seconds Since Epoch:</em> 1052401700 (2003-05-08 08:48:20 CDT)</td>
</tr>
</tbody></table>
</td>
</tr>
<!-- Null Header Message -->
<tr align="center">
<td colspan="4">
<table border="" width="100%">
<caption align="top">
<em>Null Header Message</em>
</caption>
<tbody><tr align="center">
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
<th width="25%"></th>
</tr>
<tr align="center">
<td colspan="2"><em>Message Type:</em> 0x0000</td>
<td colspan="2"><em>Message Data Size:</em> 144</td>
</tr>
<tr align="center">
<td colspan="1"><em>Flags:</em> 0x00</td>
<td colspan="3"><em>Reserved:</em> 0</td>
</tr>
</tbody></table>
</td>
</tr>
</tbody></table>
</center>
<br>
<pre> <code>
%h5debug example2.h5 976
New address: 976
Reading signature at address 976 (rel)
Object Header...
Dirty: 0
Version: 1
Header size (in bytes): 16
Number of links: 1
Number of messages (allocated): 6 (32)
Number of chunks (allocated): 1 (8)
Chunk 0...
Dirty: 0
Address: 992
Size in bytes: 256
Message 0...
Message ID (sequence number): 0x0005 `fill_new' (0)
Shared: No
Constant: Yes
Raw size in obj header: 8 bytes
Chunk number: 0
Message Information:
Version: 1
Space Allocation Time: Late
Fill Time: On Allocation
Fill Value Defined: Undefined
Size: 0
Data type: <dataset type="">
Message 1...
Message ID (sequence number): 0x0003 data_type(0)
Shared message: No
Constant: Yes
Raw size in obj header: 16 bytes
Chunk number: 0
Message Information:
Type class: integer
Size: 4 bytes
Byte order: little endian
Precision: 32 bits
Offset: 0 bits
Low pad type: zero
High pad type: zero
Sign scheme: 2's comp
Message 2...
Message ID (sequence number): 0x0001 simple_dspace(0)
Shared message: No
Constant: No
Raw size in obj header: 8 bytes
Chunk number: 0
Message Information:
Rank: 0
Message 3...
Message ID (sequence number): 0x0008 layout(0)
Shared message: No
Constant: No
Raw size in obj header: 24 bytes
Chunk number: 0
Message Information:
Data address: UNDEF
Number of dimensions: 1
Size: {4}
Message 4...
Message ID (sequence number): 0x0012 mtime_new(0)
Shared message: No
Constant: No
Raw size in obj header: 8 bytes
Chunk number: 0
Message Information:
Time: 2003-03-05 14:52:00 CST
Message 5...
Message ID (sequence number): 0x0000 null(0)
Shared message: No
Constant: No
Raw size in obj header: 144 bytes
Chunk number: 0
Message Information:
<no info="" for="" this="" message="">
</no></dataset></code> </pre>
<p></p>
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