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authorFrank Baker <fbaker@hdfgroup.org>2004-07-02 22:27:00 (GMT)
committerFrank Baker <fbaker@hdfgroup.org>2004-07-02 22:27:00 (GMT)
commit0f7e7766509bdf92eda32e08f50dc8197a231710 (patch)
tree22b7d93fc630958c5411070bfe571dcb6c6d7e81 /doc/html/RM_H5P.html
parent145fc6d7e7a06429338f7323817bbe9af83ded93 (diff)
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[svn-r8797]
Purpose: To more carefully describe the -- behavior of H5Pset_external -- appropriate usage of H5Pset_shuffle Description: H5Pset_external Add notes that first H5Pset_external call sets the dataset as EXTERNAL and identifies the first file in the series of external files that will hold the dataset; subsequent calls identify additional files; all external files must be declared before the dataset is created; and the library will create files that don't yet exist on the system at the time that H5Dwrite is called to write data to that file. H5Pset_shuffle Added notes regarding usage of H5Pset_shuffle in concert with a compression filter. And, as always, a few copy edits.
Diffstat (limited to 'doc/html/RM_H5P.html')
-rw-r--r--doc/html/RM_H5P.html47
1 files changed, 33 insertions, 14 deletions
diff --git a/doc/html/RM_H5P.html b/doc/html/RM_H5P.html
index 1b15b8a..9897793 100644
--- a/doc/html/RM_H5P.html
+++ b/doc/html/RM_H5P.html
@@ -2328,7 +2328,6 @@ END SUBROUTINE h5pget_class_parent_f
include the following:
<pre>
H5FD_CORE
- H5FD_DPSS
H5FD_FAMILY
H5FD_GASS
H5FD_LOG
@@ -6428,35 +6427,49 @@ END SUBROUTINE h5pset_edc_check_f
<dt><strong>Purpose:</strong>
<dd>Adds an external file to the list of external files.
<dt><strong>Description:</strong>
- <dd><code>H5Pset_external</code> adds an external file to the
- list of external files.
+ <dd>The first call to <code>H5Pset_external</code> sets the
+ <i>external storage</i> property in the property list,
+ thus designating that the dataset will be stored in
+ one or more non-HDF5 file(s) external to the HDF5 file.
+ This call also adds the file <code>name</code> as the
+ first file in the list of external files.
+ Subsequent calls to the function add the named file as
+ the next file in the list.
<p>
- If a dataset is split across multiple files then the files
+ If a dataset is split across multiple files, then the files
should be defined in order. The total size of the dataset is
the sum of the <code>size</code> arguments for all the external files. If
the total size is larger than the size of a dataset then the
dataset can be extended (provided the data space also allows
the extending).
<p>
- The <code>size</code> argument specifies number of bytes reserved
+ The <code>size</code> argument specifies the number of bytes reserved
for data in the external file.
If <code>size</code> is set to <code>H5F_UNLIMITED</code>, the
- external file can be of unlimited size and no more files can be added to
- the external files list.
+ external file can be of unlimited size and no more files can be added
+ to the external files list.
+ <p>
+ All of the external files for a given dataset must be
+ specified with <code>H5Pset_external</code>
+ <i>before</i> <code>H5Dcreate</code> is called to create
+ the dataset.
+ If one these files does not exist on the system when
+ <code>H5Dwrite</code> is called to write data to it,
+ the library will create the file.
<dt><strong>Parameters:</strong>
<ul><table>
<tr>
- <td valign="top"><em>hid_t</em> <code>plist</code></td>
+ <td valign="top"><em>hid_t</em> <code>plist</code></td>
<td valign="top">IN: Identifier of a dataset creation property list.</td></tr>
<tr>
- <td valign="top"><em>const&nbsp;char</em>&nbsp;<code>*name&nbsp;&nbsp;&nbsp;&nbsp;</code></td>
+ <td valign="top"><em>const&nbsp;char</em>&nbsp;<code>*name&nbsp;&nbsp;&nbsp;&nbsp;</code></td>
<td valign="top">IN: Name of an external file.</td></tr>
<tr>
- <td valign="top"><em>off_t</em> <code>offset</code></td>
+ <td valign="top"><em>off_t</em> <code>offset</code></td>
<td valign="top">IN: Offset, in bytes, from the beginning of the file
to the location in the file where the data starts.</td></tr>
<tr>
- <td valign="top"><em>hsize_t</em> <code>size</code></td>
+ <td valign="top"><em>hsize_t</em> <code>size</code></td>
<td valign="top">IN: Number of bytes reserved in the file for the data.</td></tr>
</table></ul>
<dt><strong>Returns:</strong>
@@ -8694,8 +8707,14 @@ END SUBROUTINE h5pset_preserve_f
closely related to each other and putting them together
can increase the compression ratio.
<p>
- This filter is designed to be used in combination with
- a compression filter.
+ As implied above, the primary value of the shuffle filter
+ lies in its coordinated use with a compression filter;
+ it does not provide data compression when used alone.
+ When the shuffle filter is applied to a dataset
+ immediately prior to the use of a compression filter,
+ the compression ratio achieved is often superior to that
+ achieved by the use of a compression filter without
+ the shuffle filter.
<dt><strong>Parameters:</strong>
<ul><table>
<tr>
@@ -9683,7 +9702,7 @@ And in this document, the
Describes HDF5 Release 1.7, the unreleased development branch; working toward HDF5 Release 1.8.0
</address><!-- #EndLibraryItem --><SCRIPT LANGUAGE="JAVASCRIPT">
<!--
-document.writeln("Last modified: 10 March 2004");
+document.writeln("Last modified: 2 July 2004");
-->
</SCRIPT>