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|
<html>
<head><title>
HDF5/H5T Draft API Specification
</title></head>
<body>
<center>
<h1>H5T: Datatype Interface</h1>
</center>
<h2>Datatype Object API Functions</h2>
These functions create and manipulate the datatype which describes elements
of a dataset.
<table border=0>
<tr><td valign=top>
<ul>
<li><a href="#Datatype-Open">H5Topen</a>
<li><a href="#Datatype-Commit">H5Tcommit</a>
<li><a href="#Datatype-Committed">H5Tcommitted</a>
<li><a href="#Datatype-InsertArray">H5Tinsert_array</a>
<li><a href="#Datatype-Share">H5Tshare</a>
<li><a href="#Datatype-Find">H5Tfind</a>
<li><a href="#Datatype-Convert">H5Tconvert</a>
<li><a href="#Datatype-SetOverflow">H5Tset_overflow</a>
<li><a href="#Datatype-GetOverflow">H5Tget_overflow</a>
<li>
<li><a href="#Datatype-Create">H5Tcreate</a>
<li><a href="#Datatype-Copy">H5Tcopy</a>
<li><a href="#Datatype-Equal">H5Tequal</a>
<li><a href="#Datatype-Lock">H5Tlock</a>
<li><a href="#Datatype-GetClass">H5Tget_class</a>
<li><a href="#Datatype-GetSize">H5Tget_size</a>
<li><a href="#Datatype-SetSize">H5Tset_size</a>
<li><a href="#Datatype-GetOrder">H5Tget_order</a>
<li><a href="#Datatype-SetOrder">H5Tset_order</a>
<li><a href="#Datatype-GetPrecision">H5Tget_precision</a>
<li><a href="#Datatype-SetPrecision">H5Tset_precision</a>
<li><a href="#Datatype-GetOffset">H5Tget_offset</a>
<li><a href="#Datatype-SetOffset">H5Tset_offset</a>
<li><a href="#Datatype-GetPad">H5Tget_pad</a>
</ul>
</td><td> </td><td valign=top>
<ul>
<li><a href="#Datatype-SetPad">H5Tset_pad</a>
<li><a href="#Datatype-GetSign">H5Tget_sign</a>
<li><a href="#Datatype-SetSign">H5Tset_sign</a>
<li><a href="#Datatype-GetFields">H5Tget_fields</a>
<li><a href="#Datatype-SetFields">H5Tset_fields</a>
<li><a href="#Datatype-GetEbias">H5Tget_ebias</a>
<li><a href="#Datatype-SetEbias">H5Tset_ebias</a>
<li><a href="#Datatype-GetNorm">H5Tget_norm</a>
<li><a href="#Datatype-SetNorm">H5Tset_norm</a>
<li><a href="#Datatype-GetInpad">H5Tget_inpad</a>
<li><a href="#Datatype-SetInpad">H5Tset_inpad</a>
<li><a href="#Datatype-GetCset">H5Tget_cset</a>
<li><a href="#Datatype-SetCset">H5Tset_cset</a>
<li><a href="#Datatype-GetStrpad">H5Tget_strpad</a>
</ul>
</td><td> </td><td valign=top>
<ul>
<li><a href="#Datatype-SetStrpad">H5Tset_strpad</a>
<li><a href="#Datatype-GetNmembers">H5Tget_nmembers</a>
<li><a href="#Datatype-GetMemberName">H5Tget_member_name</a>
<li><a href="#Datatype-GetMemberOffset">H5Tget_member_offset</a>
<li><a href="#Datatype-GetMemberDims">H5Tget_member_dims</a>
<li><a href="#Datatype-GetMemberType">H5Tget_member_type</a>
<li><a href="#Datatype-Insert">H5Tinsert</a>
<li><a href="#Datatype-Pack">H5Tpack</a>
<li><a href="#Datatype-RegisterHard">H5Tregister_hard</a>
<li><a href="#Datatype-RegisterSoft">H5Tregister_soft</a>
<li><a href="#Datatype-Unregister">H5Tunregister</a>
<li><a href="#Datatype-Close">H5Tclose</a>
</ul>
</td></tr>
</table>
<p>
The Datatype interface, H5T, provides a mechanism to describe the
storage format of individual data points of a data set and is
hopefully designed in such a way as to allow new features to be
easily added without disrupting applications that use the data
type interface. A dataset (the H5D interface) is composed of a
collection or raw data points of homogeneous type organized
according to the data space (the H5S interface).
<p>
A data type is a collection of data type properties, all of
which can be stored on disk, and which when taken as a whole,
provide complete information for data conversion to or from that
data type. The interface provides functions to set and query
properties of a data type.
<p>
A <em>data point</em> is an instance of a <em>datatype</em>,
which is an instance of a <em>type class</em>. We have defined
a set of type classes and properties which can be extended at a
later time. The atomic type classes are those which describe
types which cannot be decomposed at the data type interface
level; all other classes are compound.
<p>
See <a href="Datatypes.html"><cite>The Datatype Interface (H5T)</cite></a>
in the <cite>HDF5 User's Guide</cite> for further information.
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Open">H5Topen</a>
<dt><strong>Signature:</strong>
<dd><em>hid_t</em><code>H5Topen</code>(<em>hid_t</em> <code>loc_id</code>,
<em>const char *</em> <code>name</code>
)
<dt><strong>Purpose:</strong>
<dd>Opens a named datatype.
<dt><strong>Description:</strong>
<dd><b>From UG:</b> <code>H5Topen</code> opens a named datatype at the location
specified by <code>loc_id</code> and returns an identifier
for the data type. The identifier should eventually be closed
by calling <code>H5Tclose()</code> to release resources.
<code>loc_id</code> is either a file or group identifier.
<p>
<b>From SC:</b> Opens a named datatype.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>loc_id</code>
<dd>A file or group identifier.
<dt><em>const char *</em> <code>name</code>
<dd>A datatype name.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a named datatype identifier if successful;
otherwise FAIL (-1).
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Commit">H5Tcommit</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em><code>H5Tcommit</code>(<em>hid_t</em> <code>loc_id</code>,
<em>const char *</em> <code>name</code>,
<em>hid_t</em> <code>type</code>
)
<dt><strong>Purpose:</strong>
<dd>Commits a transient datatype to a file, creating a new named datatype.
<dt><strong>Description:</strong>
<dd><b>From UG:</b> <code>H5Tcommit</code> commits a transient datatype (not immutable)
to a file, turned it into a named datatype. The <code>loc_id</code>
is either a file or group identifier which, when combined with
<code>name</code>, refers to a new named data type.
<p>
<b>From SC:</b> Saves a transient data type to a file and turns
the type identifier into a named, immutable type.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>loc_id</code>
<dd>A file or group identifier.
<dt><em>const char *</em> <code>name</code>
<dd>A datatype name.
<dt><em>hid_t</em> <code>type</code>
<dd>A datatype identifier.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns SUCCEED (0) if successful;
otherwise FAIL (-1).
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Committed">H5Tcommitted</a>
<dt><strong>Signature:</strong>
<dd><em>hbool_t</em><code>H5Tcommitted</code>(<em>hid_t</em> <code>type</code>)
<dt><strong>Purpose:</strong>
<dd>Determines whether a datatype is a named type or a transient type.
<dt><strong>Description:</strong>
<dd><b>From UG:</b> <code>H5Tcommitted</code> queries a type to determine whether
it is a named type or a transient type. If this function returns
a positive value, then the type is named (that is, it has been
committed, perhaps by some other application). Datasets which
return committed data types with <code>H5Dget_type()</code> are
able to share the data type with other datasets in the same file.
<p>
<b>From SC:</b> Determines whether a data type is committed.
<dt><strong>Parameters:</strong>
<dl>
<dt>hid_t</em> <code>type</code>
<dd>Datatype identifier.
</dl>
<dt><strong>Returns:</strong>
<dd><b>From UG:</b> Returns a datatype identifier if successful;
otherwise FAIL (-1).
<dd><b>From SC:</b> The successful returns values are TRUE if committed,
else FALSE. Otherwise returns FAIL (-1).
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-InsertArray">H5Tinsert_array</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em><code>H5Tinsert_array</code>(<em>hid_t</em> <code>parent_id</code>,
<em>const char *</em><code>name</code>,
<em>size_t</em> <code>offset</code>,
<em>int</em> <code>ndims</code>,
<em>const size_t *</em><code>dim</code>,
<em>const int *</em><code>perm</code>,
<em>hid_t</em> <code>member_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Adds a new member to a compound data type.
<dt><strong>Description:</strong>
<dd><b>From SC:</b> <code>H5Tinsert_array</code> adds a new member to the
compound data type <code>parent_id</code>. The new member's name,
<code>name</code>, must be unique within the compound data type.
The <code>offset</code> argument defines the start of
the member in an instance of the compound data type and
<code>member_id</code> is the type of the new member.
The member is an array with <code>ndims</code> dimensionality
and the size of the array is </em><code>dim</code>.
The total member size should be relatively small
<dt><strong>Parameters:</strong>
<dl>
<dt>hid_t</em> <code>parent_id</code>
<dd>
<dt><em>const char *</em><code>name</code>
<dd>
<dt><em>size_t</em> <code>offset</code>
<dd>
<dt><em>int</em> <code>ndims</code>
<dd>
<dt><em>const size_t *</em><code>dim</code>
<dd>
<dt><em>const int *</em><code>perm</code>
<dd>
<dt><em>hid_t</em> <code>member_id</code>
<dd>
</dl>
<dt><strong>Returns:</strong>
<dd>Returns SUCCEED (0) if successful;
otherwise FAIL (-1).
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Find">H5Tfind</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_conv_t</em> <code>H5Tfind</code>(<em>hid_t</em> <code>src_id</code>,
<em>hid_t</em> <code>dst_id</code>,
<em>H5T_cdata_t **</em><code>pcdata</code>
)
<dt><strong>Purpose:</strong>
<dd>Finds a conversion function.
<dt><strong>Description:</strong>
<dd><b>From SC:</b> <code>H5Tfind</code> finds a conversion function
that can handle a conversion from type <code>src_id</code> to
type <code>dst_id</code>.
The <code>pcdata</code> argument is a pointer
to a pointer to type conversion data which was created and
initialized by the soft type conversion function of this path
when the conversion function was installed on the path.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>src_id</code>
<dd>
<dt><em>hid_t</em> <code>dst_id</code>
<dd>
<dt><em>H5T_cdata_t **</em><code>pcdata</code>
<dd>
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a pointer to a suitable conversion function if successful.
Otherwise returns FAIL (-1).
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Convert">H5Tconvert</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Tconvert</code>(<em>hid_t</em> <code>src_id</code>,
<em>hid_t</em> <code>dst_id</code>,
<em>size_t</em> <code>nelmts</code>,
<em>void *</em><code>buf</code>,
<em>void *</em><code>background</code>
)
<dt><strong>Purpose:</strong>
<dd>Converts data from between specified datatypes.
<dt><strong>Description:</strong>
<dd><b>From SC:</b> Convert <code>nelmts</code> elements from type
<code>src_id</code> to type <code>dst_id</code>.
The source elements are packed in <code>buf</code> and on return
the destination will be packed in <code>buf</code>.
That is, the conversion is performed in place.
The optional background buffer is an array of <code>nelmts</code>
values of destination type which are merged with the converted
values to fill in cracks (for instance, <code>background</code>
might be an array of structs with the <code>a</code> and
<code>b</code> fields already initialized and the conversion
of <code>buf</code> supplies the <code>c</code> and <code>d</code>
field values).
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>src_id</code>
<dd>
<dt><em>hid_t</em> <code>dst_id</code>
<dd>
<dt><em>size_t</em> <code>nelmts</code>
<dd>
<dt><em>void *</em><code>buf</code>
<dd>
<dt><em>void *</em><code>background</code>
<dd>
</dl>
<dt><strong>Returns:</strong>
<dd>Returns SUCCEED (0) if successful;
otherwise FAIL (-1).
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetOverflow">H5Tset_overflow</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Tset_overflow</code>(<em>H5T_overflow_t</em> <code>func</code>)
<dt><strong>Purpose:</strong>
<dd>Sets the overflow handler to a specified function.
<dt><strong>Description:</strong>
<dd><b>From SC:</b> <code>H5Tset_overflow</code> sets the overflow handler
to be the function specified by <code>func</code>.
<code>func</code> will be called for all data type conversions that
result in an overflow.
<p>
See the definition of <code>H5T_overflow_t</code> in
<code>H5Tpublic.h</code> for documentation
of arguments and return values.
The prototype for <code>H5T_overflow_t</code> is as follows:<br>
<code>herr_t (*H5T_overflow_t)(hid_t src_id, hid_t dst_id,
void *src_buf, void *dst_buf);
</code>
<p>
The NULL pointer may be passed to remove the overflow handler.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>H5T_overflow_t</em> <code>func</code>
<dd>
</dl>
<dt><strong>Returns:</strong>
<dd>Returns SUCCEED (0) if successful;
otherwise FAIL (-1).
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetOverflow">H5Tget_overflow</a>
<dt><strong>Signature:</strong>
H5Tget_overflow ()
<dd><em>H5T_overflow_t</em> <code>H5Tget_overflow</code>(<code>void</code>)
<dt><strong>Purpose:</strong>
<dd>Returns a pointer to the current global overflow function.
<dt><strong>Description:</strong>
<dd><b>From SC:</b> <code>H5Tset_overflow</code> returns a pointer
to the current global overflow function.
This is an application-defined function that is called whenever a
data type conversion causes an overflow.
<dt><strong>Parameters:</strong>
<dl>
<dt>None.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a pointer to an application-defined function if successful.
Otherwise returns NULL; this can happen if no overflow handling
function is registered.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Create">H5Tcreate</a>
<dt><strong>Signature:</strong>
<dd><em>hid_t </em><code>H5Tcreate</code>(<em>H5T_class_t </em><code>class</code>,
<em>size_t</em><code>size</code>
)
<dt><strong>Purpose:</strong>
<dd>Creates a new dataype.
<dt><strong>Description:</strong>
<dd><code>H5Tcreate</code> creates a new dataype of the specified class with the
specified number of bytes. Currently, only the <code>H5T_COMPOUND</code>
datatype class is supported with this function, use <code>H5Tcopy</code>
to create integer or floating-point datatypes. The datatype ID
returned from this function should be released with H5Tclose or resource
leaks will result.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>H5T_class_t</em> <code>class</code>
<dd>Class of datatype to create.
<dt><em>size_t</em> <code>size</code>
<dd>The number of bytes in the datatype to create.
</dl>
<dt><strong>Returns:</strong>
<dd>Datatype ID on success, negative on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Copy">H5Tcopy</a>
<dt><strong>Signature:</strong>
<dd><em>hid_t </em><code>H5Tcopy</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Copies an existing datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tcopy</code> copies an existing datatype. The datatype ID returned
should be released with H5Tclose or resource leaks will occur. Native
datatypes supported by the library are:
<ul> <dl>
<dt>H5T_NATIVE_CHAR
<dd> Native character type, declare dataset array as 'char'
<dt>H5T_NATIVE_UCHAR
<dd> Native unsigned character type, declare dataset array as 'unsigned char'
<dt>H5T_NATIVE_SHORT
<dd> Native short type, declare dataset array as 'short'
<dt>H5T_NATIVE_USHORT
<dd> Native unsigned short type, declare dataset array as 'unsigned short'
<dt>H5T_NATIVE_INT
<dd> Native int type, declare dataset array as 'int'
<dt>H5T_NATIVE_UINT
<dd> Native unsigned int type, declare dataset array as 'unsigned int'
<dt>H5T_NATIVE_LONG
<dd> Native long type, declare dataset array as 'unsigned long'
<dt>H5T_NATIVE_ULONG
<dd> Native unsigned long type, declare dataset array as 'unsigned long'
<dt>H5T_NATIVE_LLONG
<dd> Native long long type, declare dataset array as 'unsigned long long'
<dt>H5T_NATIVE_ULLONG
<dd> Native unsigned long long type, declare dataset array as 'unsigned long long'
<dt>H5T_NATIVE_INT8
<dd> Native signed 8-bit type, declare dataset array as 'int8'
<dt>H5T_NATIVE_UINT8
<dd> Native unsigned 8-bit type, declare dataset array as 'uint8'
<dt>H5T_NATIVE_INT16
<dd> Native signed 16-bit type, declare dataset array as 'int16'
<dt>H5T_NATIVE_UINT16
<dd> Native unsigned 16-bit type, declare dataset array as 'uint16'
<dt>H5T_NATIVE_INT32
<dd> Native signed 32-bit type, declare dataset array as 'int32'
<dt>H5T_NATIVE_UINT32
<dd> Native unsigned 32-bit type, declare dataset array as 'uint32'
<dt>H5T_NATIVE_INT64
<dd> Native signed 64-bit type, declare dataset array as 'uint64'
<dt>H5T_NATIVE_UINT64
<dd> Native unsigned 64-bit type, declare dataset array as 'uint64'
<dt>H5T_NATIVE_FLOAT
<dd> Native single-precision float type, declare dataset array as 'float'
<dt>H5T_NATIVE_DOUBLE
<dd> Native double-precision float type, declare dataset array as 'double'
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to copy.
</dl>
<dt><strong>Returns:</strong>
<dd>Datatype ID on success, negative on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Equal">H5Tequal</a>
<dt><strong>Signature:</strong>
<dd><em>hbool_t </em><code>H5Tequal</code>(<em>hid_t </em><code>type_id1</code>,
<em>hid_t</em><code>type_id2</code>
)
<dt><strong>Purpose:</strong>
<dd>Determines whether two datatype identifiers refer to the same datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tequal</code> determines whether two datatype identifiers
refer to the same datatype.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id1</code>
<dd>ID of datatype to compare.
<dt><em>hid_t</em> <code>type_id2</code>
<dd>ID of datatype to compare.
</dl>
<dt><strong>Returns:</strong>
<dd>TRUE/FALSE/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Lock">H5Tlock</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tlock</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Locks a type.
<dt><strong>Description:</strong>
<dd><code>H5Tlock</code> locks a type, making it read-only and non-destrucible.
This is normally done by the library for predefined data types so the
application doesn't inadvertently change or delete a predefined type.
Once a data type is locked it can never be unlocked.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to lock.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetClass">H5Tget_class</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_class_t </em><code>H5Tget_class</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Returns the base class of a datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tget_class</code> returns the base class of a datatype.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Non-negative type class on success, negative on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetSize">H5Tget_size</a>
<dt><strong>Signature:</strong>
<dd><em>size_t </em><code>H5Tget_size</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Returns the size of a datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tget_size</code> returns the size of a datatype in bytes.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Positve size in bytes on success, 0 on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetSize">H5Tset_size</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_size</code>(<em>hid_t </em><code>type_id</code>,
<em>size_t</em><code>size</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the total size for an atomic data type.
<dt><strong>Description:</strong>
<dd><code>H5Tset_size</code> sets the total size in bytes for an
atomic data type (this
operation is not permitted on compound data types). If the size is
decreased so that the significant bits of the data type extend beyond
the edge of the new size, then the `offset' property is decreased
toward zero. If the `offset' becomes zero and the significant
bits of the data type still hang over the edge of the new size, then
the number of significant bits is decreased.
Adjusting the size of an H5T_STRING automatically sets the precision
to 8*size. All data types have a positive size.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to change size.
<dt><em>size_t</em> <code>size</code>
<dd>Size in bytes to modify datatype.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetOrder">H5Tget_order</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_order_t </em><code>H5Tget_order</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Returns the byte order of an atomic datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tget_order</code> returns the byte order of an atomic datatype.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Byte order constant on success, negative on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetOrder">H5Tset_order</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_order</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_order_t</em><code>order</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the byte ordering of an atomic datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tset_order</code> sets the byte ordering of an atomic datatype.
Byte orderings currently supported are:
<ul> <dl>
<dt>H5T_ORDER_LE
<dd> Little-endian byte ordering (default)
<dt>H5T_ORDER_BE
<dd> Big-endian byte ordering
<dt>H5T_ORDER_Vax
<dd> VAX-endianness byte ordering (not currently supported)
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>H5T_order_t</em> <code>order</code>
<dd>Byte ordering constant.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetPrecision">H5Tget_precision</a>
<dt><strong>Signature:</strong>
<dd><em>size_t </em><code>H5Tget_precision</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Returns the precision of an atomic data type.
<dt><strong>Description:</strong>
<dd><code>H5Tget_precision</code> returns the precision of an atomic data type. The
precision is the number of significant bits which, unless padding is
present, is 8 times larger than the value returned by H5Tget_size().
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Number of significant bits on success, 0 on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetPrecision">H5Tset_precision</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_precision</code>(<em>hid_t </em><code>type_id</code>,
<em>size_t</em><code>precision</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the precision of an atomic data type.
<dt><strong>Description:</strong>
<dd><code>H5Tset_precision</code> sets the precision of an atomic data type.
The precision is the number of significant bits which, unless padding
is present, is 8 times larger than the value returned by H5Tget_size().
<P>If the precision is increased then the offset is decreased and then
the size is increased to insure that significant bits do not "hang
over" the edge of the data type.
<P>Changing the precision of an H5T_STRING automatically changes the
size as well. The precision must be a multiple of 8.
<P>When decreasing the precision of a floating point type, set the
locations and sizes of the sign, mantissa, and exponent fields
first.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>size_t</em> <code>precision</code>
<dd>Number of bits of precision for datatype.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetOffset">H5Tget_offset</a>
<dt><strong>Signature:</strong>
<dd><em>size_t </em><code>H5Tget_offset</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the bit offset of the first significant bit.
<dt><strong>Description:</strong>
<dd><code>H5Tget_offset</code> retrieves the bit offset of the first significant bit.
The signficant bits of an atomic datum can be offset from the beginning
of the memory for that datum by an amount of padding. The `offset'
property specifies the number of bits of padding that appear to the
"right of" the value. That is, if we have a 32-bit datum with 16-bits
of precision having the value 0x1122 then it will be layed out in
memory as (from small byte address toward larger byte addresses):
<br>
<br>
<table border align=center cellpadding=4 width="80%">
<tr align=center>
<th width="20%">Byte Position</th>
<th width="20%">Big-Endian Offset=0</th>
<th width="20%">Big-Endian Offset=16</th>
<th width="20%">Little-Endian Offset=0</th>
<th width="20%">Little-Endian Offset=16</th>
</tr>
<tr align=center>
<td>0:</td>
<td>[ pad]</td>
<td>[0x11]</td>
<td>[0x22]</td>
<td>[ pad]</td>
</tr>
<tr align=center>
<td>1:</td>
<td>[ pad]</td>
<td>[0x22]</td>
<td>[0x11]</td>
<td>[ pad]</td>
</tr>
<tr align=center>
<td>2:</td>
<td>[0x11]</td>
<td>[ pad]</td>
<td>[ pad]</td>
<td>[0x22]</td>
</tr>
<tr align=center>
<td>3:</td>
<td>[0x22]</td>
<td>[ pad]</td>
<td>[ pad]</td>
<td>[0x11]</td>
</tr>
</table>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Positive offset value on success, 0 on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetOffset">H5Tset_offset</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_offset</code>(<em>hid_t </em><code>type_id</code>,
<em>size_t</em> <code>offset</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the bit offset of the first significant bit.
<dt><strong>Description:</strong>
<dd><code>H5Tset_offset</code> sets the bit offset of the first significant bit. The
signficant bits of an atomic datum can be offset from the beginning of
the memory for that datum by an amount of padding. The `offset'
property specifies the number of bits of padding that appear to the
"right of" the value. That is, if we have a 32-bit datum with 16-bits
of precision having the value 0x1122 then it will be layed out in
memory as (from small byte address toward larger byte addresses):
<br>
<br>
<table border align=center cellpadding=4 width="80%">
<tr align=center>
<th width="20%">Byte Position</th>
<th width="20%">Big-Endian Offset=0</th>
<th width="20%">Big-Endian Offset=16</th>
<th width="20%">Little-Endian Offset=0</th>
<th width="20%">Little-Endian Offset=16</th>
</tr>
<tr align=center>
<td>0:</td>
<td>[ pad]</td>
<td>[0x11]</td>
<td>[0x22]</td>
<td>[ pad]</td>
</tr>
<tr align=center>
<td>1:</td>
<td>[ pad]</td>
<td>[0x22]</td>
<td>[0x11]</td>
<td>[ pad]</td>
</tr>
<tr align=center>
<td>2:</td>
<td>[0x11]</td>
<td>[ pad]</td>
<td>[ pad]</td>
<td>[0x22]</td>
</tr>
<tr align=center>
<td>3:</td>
<td>[0x22]</td>
<td>[ pad]</td>
<td>[ pad]</td>
<td>[0x11]</td>
</tr>
</table>
<P>If the offset is incremented then the total size is
incremented also if necessary to prevent significant bits of
the value from hanging over the edge of the data type.
<P>The offset of an H5T_STRING cannot be set to anything but
zero.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>size_t</em> <code>offset</code>
<dd>Offset of first significant bit.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetPad">H5Tget_pad</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tget_pad</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_pad_t *</em> <code>lsb</code>,
<em>H5T_pad_t *</em> <code>msb</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the padding type of the least and most-significant bit padding.
<dt><strong>Description:</strong>
<dd><code>H5Tget_pad</code> retrieves the padding type of the least and most-significant
bit padding. Valid types are:
<ul> <dl>
<dt>H5T_PAD_ZERO
<dd>Set background to zeros.
<dt>H5T_PAD_ONE
<dd>Set background to ones.
<dt>H5T_PAD_BACKGROUND
<dd>Leave background alone.
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
<dt><em>H5T_pad_t *</em> <code>lsb</code>
<dd>Pointer to location to return least-significant bit padding type.
<dt><em>H5T_pad_t *</em> <code>msb</code>
<dd>Pointer to location to return most-significant bit padding type.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetPad">H5Tset_pad</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_pad</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_pad_t</em> <code>lsb</code>,
<em>H5T_pad_t</em> <code>msb</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the least and most-significant bits padding types.
<dt><strong>Description:</strong>
<dd><code>H5Tset_pad</code> sets the least and most-significant bits padding types.
<ul> <dl>
<dt>H5T_PAD_ZERO
<dd>Set background to zeros.
<dt>H5T_PAD_ONE
<dd>Set background to ones.
<dt>H5T_PAD_BACKGROUND
<dd>Leave background alone.
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>H5T_pad_t</em> <code>lsb</code>
<dd>Padding type for least-significant bits.
<dt><em>H5T_pad_t</em> <code>msb</code>
<dd>Padding type for most-significant bits.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetSign">H5Tget_sign</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_sign_t </em><code>H5Tget_sign</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the sign type for an integer type.
<dt><strong>Description:</strong>
<dd><code>H5Tget_sign</code> retrieves the sign type for an integer type.
Valid types are:
<ul> <dl>
<dt>H5T_SGN_NONE
<dd>Unsigned integer type.
<dt>H5T_SGN_2
<dd>Two's complement signed integer type.
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Non-negative sign type on success, negative on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetSign">H5Tset_sign</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_sign</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_sign_t</em> <code>sign</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the sign proprety for an integer type.
<dt><strong>Description:</strong>
<dd><code>H5Tset_sign</code> sets the sign proprety for an integer type.
<ul> <dl>
<dt>H5T_SGN_NONE
<dd>Unsigned integer type.
<dt>H5T_SGN_2
<dd>Two's complement signed integer type.
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>H5T_sign_t</em> <code>sign</code>
<dd>Sign type.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetFields">H5Tget_fields</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tget_fields</code>(<em>hid_t </em><code>type_id</code>,
<em>size_t *</em> <code>epos</code>,
<em>size_t *</em> <code>esize</code>,
<em>size_t *</em> <code>mpos</code>,
<em>size_t *</em> <code>msize</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves floating point data type bit field information.
<dt><strong>Description:</strong>
<dd><code>H5Tget_fields</code> retrieves information about the locations of the various
bit fields of a floating point data type. The field positions are bit
positions in the significant region of the data type. Bits are
numbered with the least significant bit number zero.
Any (or even all) of the arguments can be null pointers.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
<dt><em>size_t *</em> <code>epos</code>
<dd>Pointer to location to return exponent bit-position.
<dt><em>size_t *</em> <code>esize</code>
<dd>Pointer to location to return size of exponent in bits.
<dt><em>size_t *</em> <code>mpos</code>
<dd>Pointer to location to return mantissa bit-position.
<dt><em>size_t *</em> <code>msize</code>
<dd>Pointer to location to return size of mantissa in bits.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetFields">H5Tset_fields</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_fields</code>(<em>hid_t </em><code>type_id</code>,
<em>size_t</em> <code>epos</code>,
<em>size_t</em> <code>esize</code>,
<em>size_t</em> <code>mpos</code>,
<em>size_t</em> <code>msize</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets locations and sizes of floating point bit fields.
<dt><strong>Description:</strong>
<dd><code>H5Tset_fields</code> sets the locations and sizes of the various floating
point bit fields. The field positions are bit positions in the
significant region of the data type. Bits are numbered with the least
significant bit number zero.
<P>Fields are not allowed to extend beyond the number of bits of
precision, nor are they allowed to overlap with one another.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>size_t</em> <code>epos</code>
<dd>Exponent bit position.
<dt><em>size_t</em> <code>esize</code>
<dd>Size of exponent in bits.
<dt><em>size_t</em> <code>mpos</code>
<dd>Mantissa bit position.
<dt><em>size_t</em> <code>msize</code>
<dd>Size of mantissa in bits.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetEbias">H5Tget_ebias</a>
<dt><strong>Signature:</strong>
<dd><em>size_t </em><code>H5Tget_ebias</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the exponent bias of a floating-point type.
<dt><strong>Description:</strong>
<dd><code>H5Tget_ebias</code> retrieves the exponent bias of a floating-point type.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Positive value on success, 0 on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetEbias">H5Tset_ebias</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_ebias</code>(<em>hid_t </em><code>type_id</code>,
<em>size_t</em> <code>ebias</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the exponent bias of a floating-point type.
<dt><strong>Description:</strong>
<dd><code>H5Tset_ebias</code> sets the exponent bias of a floating-point type.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>size_t</em> <code>ebias</code>
<dd>Exponent bias value.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetNorm">H5Tget_norm</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_norm_t </em><code>H5Tget_norm</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves mantissa normalization of a floating-point datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tget_norm</code> retrieves the mantissa normalization of a floating-point
datatype. Valid normalization values are:
<ul> <dl>
<dt>H5T_NORM_IMPLIED
<dd>MSB of mantissa isn't stored, always 1
<dt>H5T_NORM_MSBSET
<dd>MSB of mantissa is always 1
<dt>H5T_NORM_NONE
<dd>Mantissa is not normalized
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Non-negative normalization type on success, negative on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetNorm">H5Tset_norm</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_norm</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_norm_t</em> <code>norm</code>
)
<dt><strong>Purpose:</strong>
<dd>Sets the mantissa normalization of a floating-point datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tset_norm</code> sets the mantissa normalization of a floating-point
datatype. Valid normalization values are:
<ul> <dl>
<dt>H5T_NORM_IMPLIED
<dd>MSB of mantissa isn't stored, always 1
<dt>H5T_NORM_MSBSET
<dd>MSB of mantissa is always 1
<dt>H5T_NORM_NONE
<dd>Mantissa is not normalized
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to set.
<dt><em>H5T_norm_t</em> <code>norm</code>
<dd>Mantissa normalization type.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetInpad">H5Tget_inpad</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_pad_t </em><code>H5Tget_inpad</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the internal padding type for unused bits in floating-point datatypes.
<dt><strong>Description:</strong>
<dd><code>H5Tget_inpad</code> retrieves the internal padding type for
unused bits in floating-point datatypes.
Valid padding values are:
<ul> <dl>
<dt>H5T_PAD_ZERO
<dd>Set background to zeros.
<dt>H5T_PAD_ONE
<dd>Set background to ones.
<dt>H5T_PAD_BACKGROUND
<dd>Leave background alone.
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Non-negative padding type on success, negative on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetInpad">H5Tset_inpad</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_inpad</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_pad_t</em> <code>inpad</code>
)
<dt><strong>Purpose:</strong>
<dd>Fills unused internal floating point bits.
<dt><strong>Description:</strong>
<dd>If any internal bits of a floating point type are unused
(that is, those significant bits which are not part of the
sign, exponent, or mantissa), then <code>H5Tset_inpad</code> will be filled
according to the value of the padding value property <code>inpad</code>.
Valid padding values are:
<ul> <dl>
<dt>H5T_PAD_ZERO
<dd>Set background to zeros.
<dt>H5T_PAD_ONE
<dd>Set background to ones.
<dt>H5T_PAD_BACKGROUND
<dd>Leave background alone.
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to modify.
<dt><em>H5T_pad_t</em> <code>pad</code>
<dd>Padding type.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetCset">H5Tget_cset</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_cset_t </em><code>H5Tget_cset</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the character set type of a string datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tget_cset</code> retrieves the character set type of a string datatype.
Valid character set values are:
<ul> <dl>
<dt>H5T_CSET_ASCII
<dd>Character set is US ASCII
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Non-negative character set type on success, negative on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetCset">H5Tset_cset</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_cset</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_cset_t</em> <code>cset</code>
)
<dt><strong>Purpose:</strong>
<dd>
<dt><strong>Description:</strong>
<dd>HDF5 is able to distinguish between character sets of different
nationalities and to convert between them to the extent possible.
Valid character set values are:
<ul> <dl>
<dt>H5T_CSET_ASCII
<dd>Character set is US ASCII
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to modify.
<dt><em>H5T_cset_t</em> <code>cset</code>
<dd>Character set type.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetStrpad">H5Tget_strpad</a>
<dt><strong>Signature:</strong>
<dd><em>H5T_str_t </em><code>H5Tget_strpad</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the string padding method for a string datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tget_strpad</code> retrieves the string padding method for a string datatype.
Valid string padding values are:
<ul> <dl>
<dt>H5T_STR_NULL
<dd>Pad with zeros (as C does)
<dt>H5T_STR_SPACE
<dd>Pad with spaces (as FORTRAN does)
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Non-negative string padding type on success, negative on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-SetStrpad">H5Tset_strpad</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tset_strpad</code>(<em>hid_t </em><code>type_id</code>,
<em>H5T_str_t</em> <code>strpad</code>
)
<dt><strong>Purpose:</strong>
<dd>Defines the storage mechanism for character strings.
<dt><strong>Description:</strong>
<dd>The method used to store character strings differs with the
programming language: C usually null terminates strings while
Fortran left-justifies and space-pads strings.
<code>H5Tset_strpad</code> defines the storage mechanism for the string.
Valid string padding values are:
<ul> <dl>
<dt>H5T_STR_NULL
<dd>Pad with zeros (as C does)
<dt>H5T_STR_SPACE
<dd>Pad with spaces (as FORTRAN does)
</dl> </ul>
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to modify.
<dt><em>H5T_str_t</em> <code>strpad</code>
<dd>String padding type.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetNmembers">H5Tget_nmembers</a>
<dt><strong>Signature:</strong>
<dd><em>intn </em><code>H5Tget_nmembers</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the number of fields in a compound datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tget_nmembers</code> retrieves the number of fields a compound datatype has.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
</dl>
<dt><strong>Returns:</strong>
<dd>Number of members datatype has on success, negative on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetMemberName">H5Tget_member_name</a>
<dt><strong>Signature:</strong>
<dd><em>char *</em> <code>H5Tget_member_name</code>(<em>hid_t </em><code>type_id</code>,
<em>intn</em> <code>fieldno</code>
)
<dt><strong>Purpose:</strong>
<dd>Retrieves the name of a field of a compound data type.
<dt><strong>Description:</strong>
<dd><code>H5Tget_member_name</code> retrieves the name of a field of a compound data type.
Fields are stored in no particular order with numbers 0 through N-1
where N is the value returned by H5Tget_nmembers(). The name of the
field is allocated with malloc() and the caller is responsible for
freeing the memory used by the name.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
<dt><em>intn</em> <code>fieldno</code>
<dd>Field number (indexed from 0) of the field name to retrieve.
</dl>
<dt><strong>Returns:</strong>
<dd>Valid pointer on success, NULL on failure
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetMemberDims">H5Tget_member_dims</a>
<dt><strong>Signature:</strong>
<dd><em>int</em> <code>H5Tget_member_dims</code>(<em>hid_t </em><code>type_id</code>,
<em>intn</em> <code>fieldno</code>,
<em>size_t *</em> <code>dims</code>,
<em>int *</em> <code>perm</code>
)
<dt><strong>Purpose:</strong>
<dd>Returns the dimensionality of the field.
<dt><strong>Description:</strong>
<dd><code>H5Tget_member_dims</code> returns the dimensionality of the field. The dimensions
and permuation vector are returned through arguments <code>dims</code>
and <code>perm</code>, both arrays of at least four elements. Either
(or even both) may be null pointers.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
<dt><em>intn</em> <code>fieldno</code>
<dd>Field number (indexed from 0) of the field dims to retrieve.
<dt><em>size_t *</em> <code>dims</code>
<dd>Pointer to buffer to store the dimensions of the field.
<dt><em>int *</em> <code>perm</code>
<dd>Pointer to buffer to store the permutation vector of the field.
</dl>
<dt><strong>Returns:</strong>
<dd>Number of dimensions on success, negative on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-GetMemberType">H5Tget_member_type</a>
<dt><strong>Signature:</strong>
<dd><em>hid_t</em> <code>H5Tget_member_type</code>(<em>hid_t </em><code>type_id</code>,
<em>intn</em> <code>fieldno</code>
)
<dt><strong>Purpose:</strong>
<dd>Returns the data type of the specified member.
<dt><strong>Description:</strong>
<dd><code>H5Tget_member_type</code> returns the data type of the specified member. The caller
should invoke H5Tclose() to release resources associated with the type.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to query.
<dt><em>intn</em> <code>fieldno</code>
<dd>Field number (indexed from 0) of the field type to retrieve.
</dl>
<dt><strong>Returns:</strong>
<dd>The ID of a copy of the datatype of the field, negative on failure.
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Insert">H5Tinsert</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Tinsert</code>(<em>hid_t </em><code>type_id</code>,
<em>const char *</em> <code>name</code>,
<em>off_t</em> <code>offset</code>,
<em>hid_t</em> <code>field_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Adds a new member to a compound data type.
<dt><strong>Description:</strong>
<dd><code>H5Tinsert</code> adds another member to the compound data type
<code>type_id</code>. The new member has a <code>name</code> which
must be unique within the compound data type. The <code>offset</code>
argument defines the start of the member in an instance of the compound
data type, and <code>field_id</code> is the type of the new member.
<P>Note: All members of a compound data type must be atomic; a
compound data type cannot have a member which is a compound data
type.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of compound datatype to modify.
<dt><em>const char *</em> <code>name</code>
<dd>Name of the field to insert.
<dt><em>off_t</em> <code>offset</code>
<dd>Offset in memory structure of the field to insert.
<dt><em>hid_t</em> <code>field_id</code>
<dd>Datatype ID of the field to insert.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Pack">H5Tpack</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Tpack</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Recursively removes padding from within a compound datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tpack</code> recursively removes padding from within a compound
datatype to make it more efficient (space-wise) to store that data.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to modify.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-RegisterHard">H5Tregister_hard</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Tregister_hard</code>(<em>const char
*</em> <code>name</code>, <em>hid_t </em><code>src_id</code>,
<em>hid_t</em> <code>dst_id</code>,
<em>H5T_conv_t</em> <code>func</code>
)
<dt><strong>Purpose:</strong>
<dd>Registers a hard conversion function.
<dt><strong>Description:</strong>
<dd><code>H5Tregister_hard</code> registers a hard conversion function for a data type
conversion path. The path is specified by the source and destination
datatypes <code>src_id</code> and <code>dst_id</code>. A conversion
path can only have one hard function, so <code>func</code> replaces any
previous hard function.
<P>If <code>func</code> is the null pointer then any hard function
registered for this path is removed from this path. The soft functions
are then used when determining which conversion function is appropriate
for this path. The <code>name</code> argument is used only
for debugging and should be a short identifier for the function.
<P>The type of the conversion function pointer is declared as:
typedef herr_t (*H5T_conv_t) (hid_t src_id, hid_t dst_id, H5T_cdata_t *cdata,
size_t nelmts, void *buf, void *bkg);
<dt><strong>Parameters:</strong>
<dl>
<dt><em>const char *</em> <code>name</code>
<dd>Name displayed in diagnostic output.
<dt><em>hid_t</em> <code>src_id</code>
<dd>ID of source datatype.
<dt><em>hid_t</em> <code>dst_id</code>
<dd>ID of destination datatype.
<dt><em>H5T_conv_t</em> <code>func</code>
<dd>Function to convert between source and destination datatypes.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-RegisterSoft">H5Tregister_soft</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Tregister_soft</code>(<em>const char
*</em> <code>name</code>, <em>hid_t </em><code>src_id</code>,
<em>hid_t</em> <code>dst_id</code>,
<em>H5T_conv_t</em> <code>func</code>
)
<dt><strong>Purpose:</strong>
<dd>Registers a soft conversion function.
<dt><strong>Description:</strong>
<dd><code>H5Tregister_soft</code> registers a soft conversion function by adding it to the
end of the master soft list and replacing the soft function in all
applicable existing conversion paths. The <code>name</code>
is used only for debugging and should be a short identifier
for the function.
<P>The type of the conversion function pointer is declared as:
typedef herr_t (*H5T_conv_t) (hid_t src_id, hid_t dst_id, H5T_cdata_t *cdata,
size_t nelmts, void *buf, void *bkg);
<dt><strong>Parameters:</strong>
<dl>
<dt><em>const char *</em> <code>name</code>
<dd>Name displayed in diagnostic output.
<dt><em>hid_t</em> <code>src_id</code>
<dd>ID of source datatype.
<dt><em>hid_t</em> <code>dst_id</code>
<dd>ID of destination datatype.
<dt><em>H5T_conv_t</em> <code>func</code>
<dd>Function to convert between source and destination datatypes.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Unregister">H5Tunregister</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5Tunregister</code>(<em>H5T_conv_t</em> <code>func</code>
)
<dt><strong>Purpose:</strong>
<dd>Removes a conversion function from all conversion paths.
<dt><strong>Description:</strong>
<dd><code>H5Tunregister</code> removes a conversion function from all conversion paths.
<P>The type of the conversion function pointer is declared as:
typedef herr_t (*H5T_conv_t) (hid_t src_id, hid_t dst_id, H5T_cdata_t *cdata,
size_t nelmts, void *buf, void *bkg);
<dt><strong>Parameters:</strong>
<dl>
<dt><em>H5T_conv_t</em> <code>func</code>
<dd>Function to remove from conversion paths.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Datatype-Close">H5Tclose</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t </em><code>H5Tclose</code>(<em>hid_t </em><code>type_id</code>
)
<dt><strong>Purpose:</strong>
<dd>Releases a datatype.
<dt><strong>Description:</strong>
<dd><code>H5Tclose</code> releases a datatype. Further access through the datatype
ID is illegal. Failure to release a datatype with this call will
result in resource leaks.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>hid_t</em> <code>type_id</code>
<dd>ID of datatype to release.
</dl>
<dt><strong>Returns:</strong>
<dd>zero/negative
</dl>
<hr>
<hr>
<b>Aha!! And here is the reference to sharing and that command that had us
so buffaloed, <code>H5Tshare</code>!</b><br>
To quote Quincy: "The H5Tshare() and H5Tis_shared() will be removed. Data types
will not be stored in the global heap. A new type of shared
message header will be added to the object headers that points to
another object header instead of the global heap..."
<hr>
<hr>
</b>UNUSED PORTIONS OF EMAIL NOTES.</b>
<br>
<code>....</code> in left margin indicates where material was
pulled out for inclusion above.
<HR>
<HR>
<pre>
Elena> Datatype Interface:
Elena> Do we have description of the named datatypes somewhere?
>From Datatypes.html...
html> 7. Sharing Data Types among Datasets
html>
html> If a file has lots of datasets which have a common data type
html> then the file could be made smaller by having all the datasets
html> share a single data type. Instead of storing a copy of the data
html> type in each dataset object header, a single data type is stored
html> and the object headers point to it. The space savings is
html> probably only significant for datasets with a compound data type
html> since the simple data types can be described with just a few
html> bytes anyway.
html>
html> To create a bunch of datasets that share a single data type just
html> create the datasets with a committed (named) data type.
html>
html> To create two datasets that share a common data type one just
html> commits the data type, giving it a name, and then uses that
html> data type to create the datasets.
html>
html> hid_t t1 = ...some transient type...;
html> H5Tcommit (file, "shared_type", t1);
html> hid_t dset1 = H5Dcreate (file, "dset1", t1, space, H5P_DEFAULT);
html> hid_t dset2 = H5Dcreate (file, "dset2", t1, space, H5P_DEFAULT);
html>
html>
html> And to create two additional datasets later which share the
html> same type as the first two datasets:
html>
html> hid_t dset1 = H5Dopen (file, "dset1");
html> hid_t t2 = H5Dget_type (dset1);
html> hid_t dset3 = H5Dcreate (file, "dset3", t2, space, H5P_DEFAULT);
html> hid_t dset4 = H5Dcreate (file, "dset4", t2, space, H5P_DEFAULT);
html>
html>
html> Example: Shared Types
Mail from Quincey summarizing shared data types:
Quincey> Hi Robb,
Quincey> Everything looks good, I just have a couple of minor comments below:
Quincey>
Quincey> > A very quick data types summary (so I can remember it next week :-)
Quincey> >
Quincey> > * Handles to named types are immutable.
Quincey> >
Quincey> > * A transient type handle can be converted to a named type handle
Quincey> > by calling H5Tcommit(). This can only be called for transient
Quincey> > types which are not locked or predefined.
Quincey> >
Quincey> > * H5Topen() returns a handle to a named immutable type.
Quincey> >
Quincey> > * H5Tcopy() returns a handle to a transient type.
Quincey> H5Tcreate also returns a handle to a transient type.
Quincey>
Quincey> > * Using a named type in H5Dcreate() causes the dataset object
Quincey> > header to point to the named type (shared). The link count on
Quincey> > the named type is incremented.
Quincey> >
Quincey> > * Using a transient type in H5Dcreate() causes the type to be
Quincey> > copied and stored in the dataset header (unshared).
Quincey> >
Quincey> > * Type handles returned from H5Dget_type() are immutable.
Quincey> >
Quincey> > * If the dataset is using a shared type (dataset object header
Quincey> > points to some other object header with a type message, e.g., a
Quincey> > named type) then H5Dget_type() returns a handle to that named
Quincey> > type.
Quincey> >
Quincey> > * If the dataset has a private type (data type is stored in the
Quincey> > dataset object header) then H5Dget_type() returns a handle to a
Quincey> > transient immutable type.
Quincey> >
Quincey> > * The name of a data type can be removed from a group, but unless
Quincey> > the reference count becomes zero the type continues to exist.
Quincey> > (Other objects work this way too).
Quincey> >
Quincey> > * H5Tcopy() applied to a dataset returns a transient, modifiable
Quincey> > copy of that dataset's data type.
Quincey> >
Quincey> > * H5Topen() applied to a dataset returns either a transient
Quincey> > immutable or named immutable data type depending on whether the
Quincey> > dataset has a shared data type.
Quincey> Hmm, do we want to allow this? It makes a certain amount of sense, but
Quincey> is a little unusual... :-)
Quincey>
Elena, we decided not not to allow H5Topen() on a dataset.
Quincey>
Quincey> > * The H5Tshare() and H5Tis_shared() will be removed. Data types
Quincey> > will not be stored in the global heap. A new type of shared
Quincey> > message header will be added to the object headers that points to
Quincey> > another object header instead of the global heap
Quincey>
Quincey> > * Still to discuss: Attributes on named data types?
Quincey> I think we should all them.
Quincey>
Elena, attributes work for named data types just like they do for
datasets.
Quincey>
Quincey> > * Still to discuss: compound types whose members point to other types.
Quincey> I like this concept a lot and this we should figure out a way to do it.
Quincey> This allows the "is a" relationship to be used very nicely for named datatypes.
Quincey>
Quincey> > * Still to discuss: datasets that point to data types in other
Quincey> > files by symbolic link.
Quincey> Probably a good idea also, just ugly to implement.
Quincey>
</pre>
<hr>
<hr>
<hr>
<address>
<a href="mailto:fbaker@ncsa.uiuc.edu">Frank Baker</a>
<br>
<a href="mailto:h5docs@ncsa.uiuc.edu">HDF5 Documentation</a>
<br>
Last modified: 9 July 1998
</body>
</html>
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