[svn-r1777] H5.format.html
Technical changes and major additions in B-tree node discussion. New tables and text for enumeration datatypes. Added links to other docs, in the header and footer. Reformatted TOC.
This commit is contained in:
Frank Baker
@@ -6,86 +6,86 @@
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</head>
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<body bgcolor="#FFFFFF">
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<p align=right>
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<font size=-1><a href="index.html" target=_top>(Return to full HDF5 document set.)</a></font>
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</p>
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<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">Other HDF5 documents and links</a> <br>
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<a href="H5.intro.html">Introduction to HDF5</a> <br>
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</td>
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<td> </td>
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<td valign=top align=right>
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<a href="H5.user.html">HDF5 User Guide</a> <br>
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<a href="RM_H5Front.html">HDF5 Reference Manual</a> <br>
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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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<center><h1>HDF5 File Format Specification</h1></center>
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<center>
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<table border=0 width=90%>
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<tr>
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<td valign=top>
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<ol type=I>
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<li><a href="#Intro">
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Introduction</a>
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<li><a href="#BootBlock">
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Disk Format Level 0 - File Signature and Super Block</a>
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<li><a href="#Group">
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Disk Format Level 1 - File Infrastructure</a>
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<li><a href="#Intro">Introduction</a>
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<li><a href="#BootBlock">Disk Format Level 0 - File Signature and Super Block</a>
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<li><a href="#Group">Disk Format Level 1 - File Infrastructure</a>
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<font size=-2>
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<ol type=A>
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<li><a href="#Btrees">
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Disk Format Level 1A - B-link Trees and B-tree Nodes</a>
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<li><a href="#SymbolTable">
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Disk Format Level 1B - Group</a>
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<li><a href="#SymbolTableEntry">
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Disk Format Level 1C - Group Entry</a>
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<li><a href="#LocalHeap">
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Disk Format Level 1D - Local Heaps</a>
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<li><a href="#GlobalHeap">
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Disk Format Level 1E - Global Heap</a>
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<li><a href="#FreeSpaceIndex">
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Disk Format Level 1F - Free-space Index</a>
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<li><a href="#Btrees">Disk Format Level 1A - B-link Trees and B-tree Nodes</a>
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<li><a href="#SymbolTable">Disk Format Level 1B - Group</a>
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<li><a href="#SymbolTableEntry">Disk Format Level 1C - Group Entry</a>
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<li><a href="#LocalHeap">Disk Format Level 1D - Local Heaps</a>
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<li><a href="#GlobalHeap">Disk Format Level 1E - Global Heap</a>
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<li><a href="#FreeSpaceIndex">Disk Format Level 1F - Free-space Index</a>
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</ol>
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<li><a href="#DataObject">
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Disk Format Level 2 - Data Objects</a>
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</font>
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<li><a href="#DataObject">Disk Format Level 2 - Data Objects</a>
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<font size=-2>
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<ol type=A>
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<li><a href="#ObjectHeader">
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Disk Format Level 2a - Data Object Headers</a>
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<li><a href="#ObjectHeader">Disk Format Level 2a - Data Object Headers</a>
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<ol type=1>
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<li><a href="#NILMessage"> <!-- 0x0000 -->
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Name: NIL</a>
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<li><a href="#SimpleDataSpace"> <!-- 0x0001 -->
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Name: Simple Dataspace</a>
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<li><a href="#NILMessage">Name: NIL</a> <!-- 0x0000 -->
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<li><a href="#SimpleDataSpace">Name: Simple Dataspace</a> <!-- 0x0001 -->
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<!--
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<li><a href="#DataSpaceMessage"> --> <!-- 0x0002 --><!--
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Name: Complex Dataspace</a>
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-->
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<li><a href="#DataTypeMessage"> <!-- 0x0003 -->
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Name: Datatype</a>
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<li><a href="#FillValueMessage"> <!-- 0x0004 -->
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Name: Data Storage - Fill Value</a>
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<li><a href="#ReservedMessage_0005"> <!-- 0x0005 -->
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Name: Reserved - not assigned yet</a>
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<li><a href="#CompactDataStorageMessage"> <!-- 0x0006 -->
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Name: Data Storage - Compact</a>
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<li><a href="#ExternalFileListMessage"> <!-- 0x0007 -->
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Name: Data Storage - External Data Files</a>
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<li><a href="#LayoutMessage"> <!-- 0x0008 -->
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Name: Data Storage - Layout</a>
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<li><a href="#ReservedMessage_0009"> <!-- 0x0009 -->
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Name: Reserved - not assigned yet</a>
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<li><a href="#ReservedMessage_000A"> <!-- 0x000a -->
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Name: Reserved - not assigned yet</a>
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<li><a href="#FilterMessage"> <!-- 0x000b -->
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Name: Data Storage - Filter Pipeline</a>
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<li><a href="#AttributeMessage"> <!-- 0x000c -->
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Name: Attribute</a>
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<li><a href="#NameMessage"> <!-- 0x000d -->
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Name: Object Name</a>
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<li><a href="#ModifiedMessage"> <!-- 0x000e -->
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Name: Object Modification Date and Time</a>
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<li><a href="#SharedMessage"> <!-- 0x000f -->
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Name: Shared Object Message</a>
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<li><a href="#ContinuationMessage"> <!-- 0x0010 -->
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Name: Object Header Continuation</a>
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<li><a href="#SymbolTableMessage"> <!-- 0x0011 -->
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Name: Group Message</a>
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<li><a href="#DataSpaceMessage">Name: Complex Dataspace</a> --> <!-- 0x0002 -->
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<li><a href="#DataTypeMessage">Name: Datatype</a> <!-- 0x0003 -->
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<li><a href="#FillValueMessage">Name: Data Storage - Fill Value</a> <!-- 0x0004 -->
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<li><a href="#ReservedMessage_0005">Name: Reserved - not assigned yet</a> <!-- 0x0005 -->
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</ol>
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<li><a href="#SharedObjectHeader">
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Disk Format: Level 2b - Shared Data Object Headers</a>
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<li><a href="#DataStorage">
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Disk Format: Level 2c - Data Object Data Storage</a>
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</ol>
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</ol>
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</font>
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</ol>
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</td><td> </td><td valign=top>
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<ol type=I>
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<li><a href="#DataObject">Disk Format Level 2 - Data Objects</a>
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<font size=-2><i>(Continued)</i>
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<ol type=A>
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<li><a href="#ObjectHeader">Disk Format Level 2a - Data Object Headers</a><i>(Continued)</i>
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<ol type=1>
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<li><a href="#CompactDataStorageMessage">Name: Data Storage - Compact</a> <!-- 0x0006 -->
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<li><a href="#ExternalFileListMessage">Name: Data Storage - External Data Files</a> <!-- 0x0007 -->
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<li><a href="#LayoutMessage">Name: Data Storage - Layout</a> <!-- 0x0008 -->
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<li><a href="#ReservedMessage_0009">Name: Reserved - not assigned yet</a> <!-- 0x0009 -->
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<li><a href="#ReservedMessage_000A">Name: Reserved - not assigned yet</a> <!-- 0x000a -->
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<li><a href="#FilterMessage">Name: Data Storage - Filter Pipeline</a> <!-- 0x000b -->
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<li><a href="#AttributeMessage">Name: Attribute</a> <!-- 0x000c -->
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<li><a href="#NameMessage">Name: Object Name</a> <!-- 0x000d -->
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<li><a href="#ModifiedMessage">Name: Object Modification Date and Time</a> <!-- 0x000e -->
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<li><a href="#SharedMessage">Name: Shared Object Message</a> <!-- 0x000f -->
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<li><a href="#ContinuationMessage">Name: Object Header Continuation</a> <!-- 0x0010 -->
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<li><a href="#SymbolTableMessage">Name: Group Message</a> <!-- 0x0011 -->
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</ol>
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<li><a href="#SharedObjectHeader">Disk Format: Level 2b - Shared Data Object Headers</a>
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<li><a href="#DataStorage">Disk Format: Level 2c - Data Object Data Storage</a>
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</ol>
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</font>
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</ol>
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</td></tr>
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</table>
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<br><br>
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@@ -635,7 +635,7 @@ Elena> "Free-space object"
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<dt>0
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<dd>This tree points to group nodes.
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<dt>1
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<dd>This tree points to a (partial) linear address space.
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<dd>This tree points to a new data chunk.
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</dl>
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</td>
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</tr>
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@@ -693,22 +693,110 @@ Elena> "Free-space object"
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<td>The format and size of the key values is determined by
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the type of data to which this tree points. The keys are
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ordered and are boundaries for the contents of the child
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pointer. That is, the key values represented by child
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pointer; that is, the key values represented by child
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<em>N</em> fall between Key <em>N</em> and Key
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<em>N</em>+1. Whether the interval is open or closed on
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each end is determined by the type of data to which the
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tree points.</td>
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tree points.
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<p>
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The format of the key depends on the node type.
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For nodes of node type 1, the key is formatted as follows:
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<center>
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<table>
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<tr valign=top align=left>
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<td width=40%>Bytes 1-4</td>
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<td>Size of chunk in bytes.</td>
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<tr valign=top align=left></tr>
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<td>Bytes 4-8</td>
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<td>Filter mask, a 32-bit bitfield indicating which
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filters have been applied to that chunk.</td>
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</tr><tr valign=top align=left>
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<td><i>N</i> fields of 8 bytes each</td>
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<td>A 64-bit index indicating the offset of the
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chunk within the dataset where <i>N</i> is the number
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of dimensions of the dataset. For example, if
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a chunk in a 3-dimensional dataset begins at the
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position <code>[5,5,5]</code>, there will be three
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such 8-bit indices, each with the value of
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<code>5</code>.</td>
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</tr>
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</table>
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</center>
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<p>
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For nodes of node type 0, the key is formatted as follows:
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<center>
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<table>
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<tr valign=top align=left>
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<td width=40%>A single field of <i>Size of Lengths</i>
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bytes</td>
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<td>Indicates the byte offset into the local heap
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for the first object name in the subtree which
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that key describes.</td>
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</tr>
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</table>
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</center>
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</td>
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</tr>
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<tr valign=top>
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<td>Child Pointers</td>
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<td>The tree node contains file addresses of subtrees or
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data depending on the node level (0 implies data
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addresses).</td>
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data depending on the node level. Nodes at Level 0 point
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to data addresses, either data chunk or group nodes.
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Nodes at non-zero levels point to other nodes of the
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same B-tree.</td>
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</tr>
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</table>
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</center>
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<p>
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Each B-tree node looks like this:
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<center>
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<table>
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<tr valign=top align=center>
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<td>key[0]</td><td> </td>
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<td>child[0]</td><td> </td>
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<td>key[1]</td><td> </td>
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<td>child[1]</td><td> </td>
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<td>key[2]</td><td> </td>
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<td>...</td><td> </td>
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<td>...</td><td> </td>
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<td>key[<i>N</i>-1]</td><td> </td>
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<td>child[<i>N</i>-1]</td><td> </td>
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<td>key[<i>N</i>]</td>
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</tr>
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</table>
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</center>
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where child[<i>i</i>] is a pointer to a sub-tree (at a level
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above Level 0) or to data (at Level 0).
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Each key[<i>i</i>] describes an <i>item</i> stored by the B-tree
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(a chunk or an object of a group node). The range of values
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represented by child[<i>i</i>] are indicated by key[<i>i</i>]
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and key[<i>i</i>+1].
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<p>The following question must next be answered:
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"Is the value described by key[<i>i</i>] contained in
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child[<i>i</i>-1] or in child[<i>i</i>]?"
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The answer depends on the type of tree.
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In trees for groups (node type 0) the object described by
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key[<i>i</i>] is the greatest object contained in
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child[<i>i</i>-1] while in chunk trees (node type 1) the
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chunk described by key[<i>i</i>] is the least chunk in
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child[<i>i</i>].
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<p>That means that key[0] for group trees is sometimes unused;
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it points to offset zero in the heap, which is always the
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empty string and compares as "less-than" any valid object name.
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<p>And key[<i>N</i>] for chunk trees is sometimes unused;
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it contains a chunk offset which compares as "greater-than"
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any other chunk offset and has a chunk byte size of zero
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to indicate that it is not actually allocated.
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<h3><a name="SymbolTable">Disk Format: Level 1B - Group and Symbol Nodes</a></h3>
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<p>A group is an object internal to the file that allows
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@@ -856,7 +944,7 @@ Elena> "Free-space object"
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<tr valign=top>
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<td>Name Offset</td>
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<td>This is the byte offset into the group local
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heap for the name of the symbol. The name is null
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heap for the name of the object. The name is null
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terminated.</td>
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</tr>
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@@ -1655,7 +1743,7 @@ Elena> "Free-space object"
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must use the <em>Complex Dataspace</em> message for expressing
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the space the dataset inhabits.
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<i>(Note: The <em>Complex Dataspace</em> functionality is
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not yet implemented, as of HDF5 Release 1.2. It is not described
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not yet implemented (as of HDF5 Release 1.2). It is not described
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in this document.)</i>
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<p>
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@@ -2544,6 +2632,81 @@ Elena> "Free-space object"
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</table>
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</center>
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<p>
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<center>
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<table border cellpadding=4 width="80%">
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<caption align=top>
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<b>Bit Field for Enumeration types (Class 8)</b>
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</caption>
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<tr align=center>
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<th width="10%">Bits</th>
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<th width="90%">Meaning</th>
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</tr>
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<tr valign=top>
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<td>0-15</td>
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<td><b>Number of Members.</b> The number of name/value
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pairs defined for the enumeration type.</td>
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</tr>
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<tr valign=top>
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<td>16-23</td>
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<td>Reserved (zero).</td>
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</tr>
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</table>
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</center>
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<p>
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<center>
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<table border cellpadding=4 width="80%">
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<caption align=top>
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<b>Properties for Enumeration types (Class 8)</b>
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</caption>
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<tr align=center>
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<th width="25%">Byte</th>
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<th width="25%">Byte</th>
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<th width="25%">Byte</th>
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<th width="25%">Byte</th>
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</tr>
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<tr align=center>
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<td colspan=4><br>Parent Type<br><br></td>
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</tr>
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<tr align=center>
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<td colspan=4><br>Names<br><br></td>
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</tr>
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<tr align=center>
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<td colspan=4><br>Values<br><br></td>
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</tr>
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</table>
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</center>
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<center>
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<table border=0 cellpadding=4 width="80%">
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<tr align=left valign=top>
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<td valign=top width=20%>Parent Type:</td>
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<td valign=top>Each enumeration type is based on some parent type,
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usually an integer. The information for that parent type is
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described recursively by this field.</td>
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</tr><tr align=left valign=top>
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<td valign=top>Names:</td>
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<td valign=top>The name for each name/value pair. Each name is
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stored as a null terminated ASCII string in a multiple of
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eight bytes. The names are in no particular order.</td>
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</tr><tr align=left valign=top>
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<td valign=top>Values:</td>
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<td valign=top>The list of values in the same order as the names.
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The values are packed (no inter-value padding) and the
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size of each value is determined by the parent type.</td>
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</tr>
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</table>
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</center>
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<!--
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<p>Datatype examples are <a href="Datatypes.html">here</a>.
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-->
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@@ -3688,18 +3851,28 @@ for the last field).
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in the structure, with each item formatted according to its datatype.
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<hr>
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<p align=right>
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<font size=-1><a href="index.html" target=_top>(Return to full HDF5 document set.)</a></font>
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</p>
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||||
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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">Other HDF5 documents and links</a> <br>
|
||||
<a href="H5.intro.html">Introduction to HDF5</a> <br>
|
||||
</td>
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||||
<td> </td>
|
||||
<td valign=top align=right>
|
||||
<a href="H5.user.html">HDF5 User Guide</a> <br>
|
||||
<a href="RM_H5Front.html">HDF5 Reference Manual</a> <br>
|
||||
</td></tr>
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||||
</table>
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||||
</center>
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||||
<hr>
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||||
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||||
<!--
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||||
<address><a href="mailto:koziol@ncsa.uiuc.edu">Quincey Koziol</a></address>
|
||||
<address><a href="mailto:matzke@llnl.gov">Robb Matzke</a></address>
|
||||
-->
|
||||
<address><a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a></address>
|
||||
<!-- hhmts start -->
|
||||
Last modified: 11 October 1999
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||||
Last modified: 18 October 1999
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||||
<!-- hhmts end -->
|
||||
</body>
|
||||
</html>
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||||
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||||
Reference in New Issue
Block a user