1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
<html>
<head>
<title>
HDF5/H5Z API Specification
</title>
</head>
<body bgcolor="#FFFFFF">
<hr>
<center>
<table border=0 width=98%>
<tr><td valign=top align=left>
<a href="H5.intro.html">Introduction to HDF5</a> <br>
<a href="H5.user.html">HDF5 User Guide</a> <br>
<a href="index.html">Other HDF5 documents and links</a> <br>
<!--
<a href="Glossary.html">Glossary</a><br>
-->
</td>
<td valign=top align=right>
And in this document, the
<a href="RM_H5Front.html">HDF5 Reference Manual</a>
<br>
<a href="RM_H5.html">H5</a>
<a href="RM_H5A.html">H5A</a>
<a href="RM_H5D.html">H5D</a>
<a href="RM_H5E.html">H5E</a>
<a href="RM_H5F.html">H5F</a>
<a href="RM_H5G.html">H5G</a>
<a href="RM_H5I.html">H5I</a>
<a href="RM_H5P.html">H5P</a>
<br>
<a href="RM_H5R.html">H5R</a>
<a href="RM_H5S.html">H5S</a>
<a href="RM_H5T.html">H5T</a>
H5Z
<a href="Tools.html">Tools</a>
<a href="PredefDTypes.html">Datatypes</a>
</td></tr>
</table>
</center>
<hr>
<center>
<h1>H5Z: Compression Interface</h1>
</center>
<h2>Compression API Functions</h2>
This function enable the user to configure a new compression
method for the local environment.
<table border=0>
<tr><td valign=top>
<ul>
<li><a href="#Compression-Register">H5Zregister</a>
</ul>
</td><td> </td><td valign=top>
<ul>
</ul>
</td></tr>
</table>
<p>
HDF5 supports compression of raw data by compression methods
built into the library or defined by an application.
A compression method is associated with a dataset when the dataset is
created and is applied independently to each storage chunk of the dataset.
The dataset must use the <code>H5D_CHUNKED</code> storage layout.
<p>
The HDF5 library does not support compression for contiguous datasets
because of the difficulty of implementing random access for partial I/O.
Compact dataset compression is not supported because it would not produce
significant results.
<p>
See <a href="Datasets.html"><cite>The Dataset Interface (H5D)</cite></a>
in the <cite>HDF5 User's Guide</cite> for further information regarding
data compression.
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Compression-Register">H5Zregister</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Zregister</code>(<em>H5Z_method_t</em> <code>method</code>,
<em>const char *</em><code>name</code>,
<em>H5Z_func_t</em> <code>function</code>
)
<dt><strong>Purpose:</strong>
<dd> Registers new compression / uncompression function.
<dt><strong>Description:</strong>
<dd><code>H5Zregister</code> registers a new compression / uncompression
function for the compression method specified by
the method number, <code>method</code>.
<p>
<code>name</code> is used for debugging and may be the null pointer.
<p>
<code>function</code> is a user-defined function providing both
compression and uncompression; it may be the null pointer.
<p>
The statistics associated with a method number are not reset
by this function; they accumulate over the life of the library.
<p><strong>New filters</strong> are defined in two phases. Before a filter can be
linked into the application with <code>H5Zregister</code>,
<code>H5Z_func_t</code> must first be defined as follows:
<dir>
<em>typedef size_t</em> (*<code>H5Z_func_t</code>)
(<em>unsigned int</em> <code>flags</code>,
<em>size_t</em> <code>cd_nelmts</code>,
<em>const unsigned int</em> <code>cd_values[]</code>,
<em>size_t</em> <code>nbytes</code>,
<em>size_t *</em><code>buf_size</code>,
<em>void **</em><code>buf</code>)
</dir>
<p>The parameters <code>flags</code>, <code>cd_nelmts</code>,
and <code>cd_values</code> are the same as for the
<code>H5Pset_filter()</code> function.
The additional flag <code>H5Z_FLAG_REVERSE</code> is set when
the filter is called as part of the input pipeline.
The parameter <code>*buf</code> points to the input buffer
which has a total size of <code>*buf_size</code> bytes,
<code>nbytes</code> of which are valid data.
<p>The filter should perform the transformation in place if
possible and return the number of valid bytes or zero for
failure. If the transformation cannot be done in place,
then the filter should allocate a new buffer with
<code>malloc()</code> and assign it to <code>*buf</code>,
assigning the allocated size of that buffer to
<code>*buf_size</code>.
The old buffer should be freed by calling <code>free()</code>.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>H5Z_method_t</em> <code>method</code>
<dd>IN: Number specifying compression method.
<dt><em>const char *</em><code>name</code>
<dd>IN: Name associated with the method number.
Used for debugging purposes only.
<dt><em>H5Z_func_t</em> <code>function</code>
<dd>IN: Compression / uncompression method.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful;
otherwise returns a negative value.
</dl>
<hr>
<center>
<table border=0 width=98%>
<tr><td valign=top align=left>
<a href="H5.intro.html">Introduction to HDF5</a> <br>
<a href="H5.user.html">HDF5 User Guide</a> <br>
<a href="index.html">Other HDF5 documents and links</a> <br>
<!--
<a href="Glossary.html">Glossary</a><br>
-->
</td>
<td valign=top align=right>
And in this document, the
<a href="RM_H5Front.html">HDF5 Reference Manual</a>
<br>
<a href="RM_H5.html">H5</a>
<a href="RM_H5A.html">H5A</a>
<a href="RM_H5D.html">H5D</a>
<a href="RM_H5E.html">H5E</a>
<a href="RM_H5F.html">H5F</a>
<a href="RM_H5G.html">H5G</a>
<a href="RM_H5I.html">H5I</a>
<a href="RM_H5P.html">H5P</a>
<br>
<a href="RM_H5R.html">H5R</a>
<a href="RM_H5S.html">H5S</a>
<a href="RM_H5T.html">H5T</a>
H5Z
<a href="Tools.html">Tools</a>
<a href="PredefDTypes.html">Datatypes</a>
</td></tr>
</table>
</center>
<hr>
<address>
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
<br>
Last modified: 11 February 2003
<br>
Describes HDF5 Release 1.5, Unreleased Development Branch
</body>
</html>
|
