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style='font-size:14.0pt'><span style='mso-tab-count:2'> </span>Data
Conversion <span class=GramE>Of</span> Arithmetic Data Types<o:p></o:p></span></b></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><span
style='mso-tab-count:3'> </span><span
class=SpellE>Quincey</span> <span class=SpellE>Koziol</span> and Raymond Lu<o:p></o:p></b></p>
<p class=MsoNormal><span style='mso-tab-count:4'> </span><st1:date
Year="2005" Day="14" Month="4">April 14, 2005</st1:date></p>
<p class=MsoNormal><span style='mso-tab-count:3'> </span>Revised
on <st1:date Year="2005" Day="12" Month="7">July 12, 2005</st1:date></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.75in;text-indent:0in;mso-list:l0 level1 lfo1;
tab-stops:list .75in'><![if !supportLists]><b style='mso-bidi-font-weight:normal'><span
style='mso-fareast-font-family:"Times New Roman"'><span style='mso-list:Ignore'>I.<span
style='font:7.0pt "Times New Roman"'> </span></span></span></b><![endif]><b
style='mso-bidi-font-weight:normal'>Introduction<o:p></o:p></b></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>This document addresses the HDF5 librarys design and
behaviors of data conversion between arithmetic data types.<span
style='mso-spacerun:yes'> </span>This document is mainly for the HDF5
application users.<span style='mso-spacerun:yes'> </span>It can be also useful
for the HDF5 library developers.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>In this document, the arithmetic data types refer to both
integers and floating-point numbers.<span style='mso-spacerun:yes'> </span>The
integers include all the librarys predefined integers and any user-defined
integers.<span style='mso-spacerun:yes'> </span>The librarys predefined
integers include standard, Intel-specific, Alpha-specific, MIPS-specific, ANSI
C9x-specific, and native data types.<span style='mso-spacerun:yes'> </span>The
<i style='mso-bidi-font-style:normal'>HDF5 Predefined <span class=SpellE>Datatypes</span></i>
section in the <i style='mso-bidi-font-style:normal'>HDF5 Reference Manual</i>
lists all these predefined data types.<span style='mso-spacerun:yes'> </span><span
style='mso-spacerun:yes'></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>For the convenience of discussion in this document, we
repeat all the possible native integers here,</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='mso-tab-count:2'> </span>C
types<span style='mso-tab-count:3'> </span>HDF5
types</p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>char</span><span
style='mso-tab-count:3'> </span><span style='mso-tab-count:1'> </span>H5T_NATIVE_CHAR<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>signed</span> char<span
style='mso-tab-count:3'> </span>H5T_NATIVE_SCHAR<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>unsigned</span> char<span
style='mso-tab-count:2'> </span>H5T_NATIVE_UCHAR<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>short</span><span
style='mso-tab-count:4'> </span>H5T_NATIVE_SHORT<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>unsigned</span>
short<span style='mso-tab-count:2'> </span>H5T_NATIVE_USHORT<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=SpellE><span
class=GramE>int</span></span><span style='mso-tab-count:4'> </span>H5T_NATIVE_INT<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>unsigned</span> <span
class=SpellE>int</span><span style='mso-tab-count:2'> </span>H5T_NATIVE_UINT<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>long</span><span
style='mso-tab-count:4'> </span>H5T_NATIVE_LONG<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>unsigned</span> long<span
style='mso-tab-count:2'> </span>H5T_NATIVE_ULONG<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>long</span> <span
class=SpellE>long</span><span style='mso-tab-count:3'> </span>H5T_NATIVE_LLONG<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>unsigned</span> long
<span class=SpellE>long</span><span style='mso-tab-count:1'> </span>H5T_NATIVE_ULLONG<o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The floating-point numbers include all the librarys
predefined floating-point types and any user-defined types.<span
style='mso-spacerun:yes'> </span>The <i style='mso-bidi-font-style:normal'>HDF5
Reference Manual</i> lists all the predefined types like IEEE, Alpha-specific,
MIPS-specific, and native floating-point data types.<span
style='mso-spacerun:yes'> </span><span style='mso-spacerun:yes'></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Possible native floating-point types are repeated below,</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='mso-tab-count:2'> </span>C
types<span style='mso-tab-count:3'> </span>HDF5
types</p>
<p class=MsoNormal><span style='mso-tab-count:2'> </span><span
class=GramE><span style='font-size:10.0pt;font-family:"Courier New"'>float</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'><span style='mso-tab-count:
4'> </span>H5T_NATIVE_FLOAT<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>double</span><span
style='mso-tab-count:1'> </span><span style='mso-tab-count:2'> </span>H5T_NATIVE_DOUBLE<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span><span class=GramE>long</span> double<span
style='mso-tab-count:3'> </span>H5T_NATIVE_LDOUBLE<o:p></o:p></span></p>
<p class=MsoNormal><span style='mso-spacerun:yes'></span></p>
<p class=MsoNormal>For the library, data conversion happens in two
scenarios.<span style='mso-spacerun:yes'> </span>One is when transferring data
between memory and disk through the executions of <span class=GramE><span
style='font-size:10.0pt;font-family:"Courier New"'>H5Dwrite(</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'>) </span>or <span
style='font-size:10.0pt;font-family:"Courier New"'>H5Dread()</span>; another is
when converting data in memory through <span style='font-size:10.0pt;
font-family:"Courier New"'>H5Tconvert()</span>.<span style='mso-spacerun:yes'>
</span>In either case, if the source and destination data types are different,
there will be data conversion.</p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><span
style='mso-spacerun:yes'></span><o:p></o:p></b></p>
<p class=MsoNormal style='margin-left:.75in;text-indent:0in;mso-list:l0 level1 lfo1;
tab-stops:list .75in'><![if !supportLists]><b style='mso-bidi-font-weight:normal'><span
style='mso-fareast-font-family:"Times New Roman"'><span style='mso-list:Ignore'>II.<span
style='font:7.0pt "Times New Roman"'> </span></span></span></b><![endif]><b
style='mso-bidi-font-weight:normal'>Hard and Soft Conversions<o:p></o:p></b></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal>The HDF5 library has two ways of converting data for a given
pair of different data types, hard and soft conversions.<span
style='mso-spacerun:yes'> </span><o:p></o:p></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>Hard vs. Soft Conversions</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>A <i style='mso-bidi-font-style:normal'>hard conversion</i>
is basically a casting done by a compiler, like <span class=SpellE><span
style='font-size:10.0pt;font-family:"Courier New"'>int</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'> a = (<span class=SpellE>int</span><span
class=GramE>)b</span></span>, where <span style='font-size:10.0pt;font-family:
"Courier New"'>b</span> is declared as <span style='font-size:10.0pt;
font-family:"Courier New"'>float</span> type.<span style='mso-spacerun:yes'>
</span>In contrary, a <i style='mso-bidi-font-style:normal'>soft conversion</i>
is done by the HDF5 librarys own conversion functions, where the bit sequence
of the source data are examined and converted into the bit sequence of the
destination data.<span style='mso-spacerun:yes'> </span>The soft conversions tend
to be more rigid although this method is slower than the hard conversions
because of all the bit operations during the conversions.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>During the development of the library, the term <i
style='mso-bidi-font-style:normal'>hardware conversion</i> and <i
style='mso-bidi-font-style:normal'>compiler conversion</i> have been used to
refer to the hard conversion.<span style='mso-spacerun:yes'> </span>The terms <i
style='mso-bidi-font-style:normal'>software conversion</i> and <i
style='mso-bidi-font-style:normal'>library conversion</i> have been used for
the soft conversion.<span style='mso-spacerun:yes'> </span>These terms may be
seen in other documents and the librarys source code.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Internally, the library maintains a list of soft conversion
functions for each pair of source and destination data type classes.<span
style='mso-spacerun:yes'> </span>A data type class is the category to which a
data type belongs.<span style='mso-spacerun:yes'> </span>For example, data type
<span style='font-size:10.0pt;font-family:"Courier New"'>H5T_NATIVE_INT</span>
and <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_NATIVE_LONG</span>
are in the <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_INTEGER</span>
class.<span style='mso-spacerun:yes'> </span>Therefore, soft conversion is
designed to handle any data types in a class including library predefined and
user-defined data types. <span style='mso-spacerun:yes'></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The library also maintains a table of hard conversion
functions for each pair of source and destination data types.<span
style='mso-spacerun:yes'> </span>Function <span style='font-size:10.0pt;
font-family:"Courier New"'>H5T_conv_int_<span class=GramE>float(</span>)</span>
is a hard conversion function.<span style='mso-spacerun:yes'> </span>The
librarys data type conversion path is this table of hard conversion functions,
i.e., hard conversion is always picked first by the library over soft
conversion.<span style='mso-spacerun:yes'> </span>Hard conversion can only
handle native data types because compilers would not recognize any non-native
data types.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So keep this in mind: soft conversion is for data type
classes while hard conversion is for data types.<span
style='mso-spacerun:yes'> </span>The librarys default conversion between
native data types is hard conversion. <span style='mso-spacerun:yes'></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>Registration and Un-registration of Conversion
Functions</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Users can register their own conversion functions to the
library through the function <span class=GramE><span style='font-size:10.0pt;
font-family:"Courier New"'>H5Tregister(</span></span><span style='font-size:
10.0pt;font-family:"Courier New"'>)</span>.<span style='mso-spacerun:yes'>
</span>These conversion functions can be either soft or hard conversion
functions.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>When a soft conversion function is registered into the
library through function <span class=GramE><span style='font-size:10.0pt;
font-family:"Courier New"'>H5Tregister(</span></span><span style='font-size:
10.0pt;font-family:"Courier New"'>)</span>, it is appended to the list of soft
conversion functions.<span style='mso-spacerun:yes'> </span>It also goes into
the table of hard conversion functions to replace all the conversion functions
which it can apply to.<span style='mso-spacerun:yes'> </span>For example, if a
new soft conversion function <span class=SpellE><span style='font-size:10.0pt;
font-family:"Courier New"'>conv_integer_fp</span></span><span style='font-size:
10.0pt;font-family:"Courier New"'>()</span> which converts any integer to any
floating-point number is registered into the soft list, all hard conversion
functions from any integer to any floating-point types will be replaced by this
soft function.<span style='mso-spacerun:yes'> </span>All <span class=GramE>librarys</span>
conversion paths from integer to floating-point number are updated to this
function.<span style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>When a hard conversion function is registered into the
library, it will go to the table of hard functions and replace existing hard
conversion function.<span style='mso-spacerun:yes'> </span>For example, if a
new function <span class=SpellE><span style='font-size:10.0pt;font-family:"Courier New"'>conv_int_<span
class=GramE>float</span></span></span><span class=GramE><span style='font-size:
10.0pt;font-family:"Courier New"'>(</span></span><span style='font-size:10.0pt;
font-family:"Courier New"'>)</span> which converts data of <span class=SpellE><span
style='font-size:10.0pt;font-family:"Courier New"'>int</span></span> type to <span
style='font-size:10.0pt;font-family:"Courier New"'>float</span> type is
registered as a hard function, it will replace librarys existing conversion
function <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_conv_int_float()</span>.<span
style='mso-spacerun:yes'> </span>The library will use the <span class=SpellE><span
style='font-size:10.0pt;font-family:"Courier New"'>conv_int_<span class=GramE>float</span></span></span><span
class=GramE><span style='font-size:10.0pt;font-family:"Courier New"'>(</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'>)</span> to convert data
from <span class=SpellE><span style='font-size:10.0pt;font-family:"Courier New"'>int</span></span>
to <span style='font-size:10.0pt;font-family:"Courier New"'>float </span>type
if hard conversion is selected.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>On the other hand, if a user wants to un-register some
conversion functions, he or she can use the function <span class=GramE><span
style='font-size:10.0pt;font-family:"Courier New"'>H5Tunregister(</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'>)</span>.<span
style='mso-spacerun:yes'> </span>This function has the same parameters as <span
class=GramE><span style='font-size:10.0pt;font-family:"Courier New"'>H5Tregister(</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'>)</span>. But all of those
parameters are optional.<span style='mso-spacerun:yes'> </span>The missed
parameters will become wild cards, which are used to generalize the criteria.<span
style='mso-spacerun:yes'> </span>For example, if a user wants to disable all
hard conversions to use soft conversions, he or she can simply un-register all
hard conversions by calling</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='mso-tab-count:1'> </span><span
class=GramE><code><span style='font-size:10.0pt'>H5Tunregister</span></code><span
style='font-size:10.0pt;font-family:"Courier New"'>(</span></span><em><span
style='font-size:10.0pt;font-family:"Courier New";font-style:normal;mso-bidi-font-style:
italic'>H5T_PERS_HARD</span></em><i style='mso-bidi-font-style:normal'><span
style='font-size:10.0pt;font-family:"Courier New"'>, </span></i><em><span
style='font-size:10.0pt;font-family:"Courier New";font-style:normal;mso-bidi-font-style:
italic'>NULL</span></em><i style='mso-bidi-font-style:normal'><span
style='font-size:10.0pt;font-family:"Courier New"'>, </span></i><em><span
style='font-size:10.0pt;font-family:"Courier New";font-style:normal;mso-bidi-font-style:
italic'>-1</span></em><i style='mso-bidi-font-style:normal'><span
style='font-size:10.0pt;font-family:"Courier New"'>, </span></i><em><span
style='font-size:10.0pt;font-family:"Courier New";font-style:normal;mso-bidi-font-style:
italic'>-1</span></em><i style='mso-bidi-font-style:normal'><span
style='font-size:10.0pt;font-family:"Courier New"'>, </span></i><em><span
style='font-size:10.0pt;font-family:"Courier New";font-style:normal;mso-bidi-font-style:
italic'>NULL</span></em><span style='font-size:10.0pt;font-family:"Courier New"'>);
<span style='mso-spacerun:yes'></span><o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>Handling Incorrect Hard Conversions</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>While developing data conversion of the HDF5 library, some
incorrect hard conversions have been discovered.<span
style='mso-spacerun:yes'> </span>Those problems are mainly from compilers
incorrect casting.<span style='mso-spacerun:yes'> </span>We need a good way to
handle these incorrect conversions instead of giving users corrupted data.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Librarys way to handle incorrect hard conversion is to
register no hard conversion function when problematic conversions are detected
during configuration.<span style='mso-spacerun:yes'> </span>In this way, the
librarys conversion path will be the librarys soft conversion function unless
users register their own conversion function.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>To find out whether the library is using a hard or soft
conversion routine for certain pair of source and destination data types, the
function <span style='font-size:10.0pt;font-family:"Courier New"'>H5Tis_hard()</span>
can be used (a proposed reference manual for this new function can be found in
the Appendix of this document).<span style='mso-spacerun:yes'> </span>To find
out the conversion routine that the library is using for certain pair of data
types, the function <span class=GramE><span style='font-size:10.0pt;font-family:
"Courier New"'>H5Tfind(</span></span><span style='font-size:10.0pt;font-family:
"Courier New"'>)</span> should be used.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The table below lists the librarys conversions using soft
routines on some systems and the reason of choosing the soft conversions.<span
style='mso-spacerun:yes'> </span>All the other conversions not listed here are
hard conversions.</p>
<p class=MsoNormal><o:p> </o:p></p>
<table class=MsoTableGrid border=1 cellspacing=0 cellpadding=0
style='border-collapse:collapse;border:none;mso-border-alt:solid windowtext .5pt;
mso-yfti-tbllook:480;mso-padding-alt:0in 5.4pt 0in 5.4pt;mso-border-insideh:
.5pt solid windowtext;mso-border-insidev:.5pt solid windowtext'>
<tr style='mso-yfti-irow:0'>
<td width=197 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>source and
destination data types<o:p></o:p></b></p>
</td>
<td width=197 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>system<o:p></o:p></b></p>
</td>
<td width=197 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>reason<o:p></o:p></b></p>
</td>
</tr>
<tr style='mso-yfti-irow:1'>
<td width=197 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>floating-point to floating-point number</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>all <span class=SpellE>Crays</span></p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span class=GramE>compiler</span> does not support <span
class=SpellE>denormalized</span> values.</p>
</td>
</tr>
<tr style='mso-yfti-irow:2'>
<td width=197 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>all integers to long double</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>all <span class=SpellE>SGIs</span></p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>compiler gives some incorrect conversion</p>
</td>
</tr>
<tr style='mso-yfti-irow:3'>
<td width=197 rowspan=2 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>unsigned (long) long to floating-point number</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>all <span class=SpellE>SGIs</span></p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>compiler gives some incorrect conversion</p>
</td>
</tr>
<tr style='mso-yfti-irow:4'>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>64-bit Solaris</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>compiler does different rounding</p>
</td>
</tr>
<tr style='mso-yfti-irow:5'>
<td width=197 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>unsigned long <span class=SpellE>long</span> to
floating-point number</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>Windows Visual Studio 6</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><o:p> </o:p></p>
</td>
</tr>
<tr style='mso-yfti-irow:6'>
<td width=197 rowspan=2 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>long double to all integers</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>all <span class=SpellE>SGIs</span></p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>compiler does some incorrect conversion</p>
</td>
</tr>
<tr style='mso-yfti-irow:7'>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>HP-UX 11.00</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>Compiler generates floating exception</p>
</td>
</tr>
<tr style='mso-yfti-irow:8;mso-yfti-lastrow:yes'>
<td width=197 valign=top style='width:2.05in;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>floating-point to unsigned long <span class=SpellE>long</span></p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>PGI compiler</p>
</td>
<td width=197 valign=top style='width:2.05in;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>compiler round-up when the fraction part is greater than
0.5</p>
</td>
</tr>
</table>
<p class=MsoNormal><span style='mso-spacerun:yes'></span></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal style='margin-left:.75in;text-indent:0in;mso-list:l0 level1 lfo1;
tab-stops:list .75in'><![if !supportLists]><b style='mso-bidi-font-weight:normal'><span
style='mso-fareast-font-family:"Times New Roman"'><span style='mso-list:Ignore'>III.<span
style='font:7.0pt "Times New Roman"'> </span></span></span></b><![endif]><b
style='mso-bidi-font-weight:normal'>Handling Exception<o:p></o:p></b></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>How to handle exceptions</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The library has provided the users with the ability to
handle exceptions during data conversion.<span style='mso-spacerun:yes'>
</span>Through the property list function <span style='font-size:10.0pt;
font-family:"Courier New"'>H5Pset_type_conv_<span class=GramE>cb(</span>)</span>,
users callback function can be registered with the library.<span
style='mso-spacerun:yes'> </span>This gives users the control over data values
whenever an exception happens. </p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The following piece of code shows how to register an
exception callback function <span class=SpellE><span style='font-size:10.0pt;
font-family:"Courier New"'>except_<span class=GramE>func</span></span></span><span
class=GramE><span style='font-size:10.0pt;font-family:"Courier New"'>(</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'>) </span>to the library,</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-spacerun:yes'> </span><span class=GramE>if(</span>H5Pset_type_conv_cb(<span
class=SpellE>dxpl_id</span>, <span class=SpellE>except_func</span>, &<span
class=SpellE>fill_value</span>)<0)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-spacerun:yes'> </span><span class=SpellE><span
class=GramE>goto</span></span> error;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-spacerun:yes'> </span><span class=GramE>if(</span>H5Pget_type_conv_cb(<span
class=SpellE>dxpl_id</span>, &op, &<span class=SpellE>user_data</span>)<0)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-spacerun:yes'> </span><span class=SpellE><span
class=GramE>goto</span></span> error;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-spacerun:yes'> </span><span class=GramE>if(</span>op != <span
class=SpellE>except_func</span> || *(<span class=SpellE>int</span>*)<span
class=SpellE>user_data</span> != <span class=SpellE>fill_value</span>)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-spacerun:yes'> </span><span class=SpellE><span
class=GramE>goto</span></span> error;<o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>It also uses <span style='font-size:10.0pt;font-family:"Courier New"'>H5Pget_type_conv_<span
class=GramE>cb(</span>)</span> to verify that the callback function has been
registered successfully.<span style='mso-spacerun:yes'> </span>The library define
the prototype of the conversion exception callback to be</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:45.0pt'><span class=SpellE><span
class=GramE><code><span style='font-size:10.0pt'>typedef</span></code></span></span>
<em>H5T_conv_ret_t</em> (<code><span style='font-size:10.0pt'>H5Z_conv_except_func_t</span></code>)
(<span class=SpellE><em>int</em></span> <span class=SpellE><code><span
style='font-size:10.0pt'>except_type</span></code></span>, <span class=SpellE><em>hid_t</em></span><em>
*</em><span class=SpellE><code><span style='font-size:10.0pt'>src_id</span></code></span>,
<span class=SpellE><em>hid_t</em></span> *<span class=SpellE><code><span
style='font-size:10.0pt'>dst_id</span></code></span>, <em>void *</em><span
class=SpellE><code><span style='font-size:10.0pt'>src_buf</span></code></span><code><span
style='font-size:10.0pt'>, </span></code><em>void *</em><span class=SpellE><code><span
style='font-size:10.0pt'>dst_buf</span></code></span><code><span
style='font-size:10.0pt'>, </span></code><em>void *</em><span class=SpellE><code><span
style='font-size:10.0pt'>op_data</span></code></span>) <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So somewhere in the code, the function <span class=SpellE><span
style='font-size:10.0pt;font-family:"Courier New"'>except_<span class=GramE>func</span></span></span><span
class=GramE><span style='font-size:10.0pt;font-family:"Courier New"'>(</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'>)</span> is defined as</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'>H5T_conv_ret_t <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span class=SpellE><span
style='font-size:10.0pt;font-family:"Courier New"'>except_<span class=GramE>func</span></span></span><span
class=GramE><span style='font-size:10.0pt;font-family:"Courier New"'>(</span></span><span
class=SpellE><span style='font-size:10.0pt;font-family:"Courier New"'>int</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'> <span class=SpellE>except_type</span>,
<span class=SpellE>hid_t</span> <span class=SpellE>src_id</span>, <span
class=SpellE>hid_t</span> <span class=SpellE>dst_id</span>, void *<span
class=SpellE>src_buf</span>, void *<span class=SpellE>dst_buf</span>, void *<span
class=SpellE>user_data</span>)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'>{<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'>
</span>H5T_conv_ret_t<span style='mso-spacerun:yes'> </span>ret =
H5T_CONV_HANDLED;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>if(</span><span class=SpellE>except_type</span> ==
H5T_CONV_EXCEPT_RANGE_HI) <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>/*only
test integer case*/<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>*(<span
class=SpellE>int</span>*<span class=GramE>)<span class=SpellE>dst</span></span><span
class=SpellE>_buf</span> = *(<span class=SpellE>int</span>*)<span class=SpellE>user_data</span>;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>else</span> if(<span class=SpellE>except_type</span> ==
H5T_CONV_EXCEPT_RANGE_LOW)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>/*only
test integer case*/<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>*(<span
class=SpellE>int</span>*<span class=GramE>)<span class=SpellE>dst</span></span><span
class=SpellE>_buf</span> = *(<span class=SpellE>int</span>*)<span class=SpellE>user_data</span>;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>else</span> if(<span class=SpellE>except_type</span> ==
H5T_CONV_EXCEPT_TRUNCATE)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>ret</span> = H5T_CONV_UNHANDLED; <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>else</span> if(<span class=SpellE>except_type</span> ==
H5T_CONV_EXCEPT_PRECISION)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>ret</span> = H5T_CONV_UNHANDLED; <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>else</span> if(<span class=SpellE>except_type</span> ==
H5T_CONV_EXCEPT_PINF) <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>/*only
test integer case*/<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>*(<span
class=SpellE>int</span>*<span class=GramE>)<span class=SpellE>dst</span></span><span
class=SpellE>_buf</span> = *(<span class=SpellE>int</span>*)<span class=SpellE>user_data</span>;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>else</span> if(<span class=SpellE>except_type</span> ==
H5T_CONV_EXCEPT_NINF)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>/*only
test integer case*/<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>*(<span
class=SpellE>int</span>*<span class=GramE>)<span class=SpellE>dst</span></span><span
class=SpellE>_buf</span> = *(<span class=SpellE>int</span>*)<span class=SpellE>user_data</span>;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>else</span> if(<span class=SpellE>except_type</span> ==
H5T_CONV_EXCEPT_NAN)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>/*only
test integer case*/<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>*(<span
class=SpellE>int</span>*<span class=GramE>)<span class=SpellE>dst</span></span><span
class=SpellE>_buf</span> = *(<span class=SpellE>int</span>*)<span class=SpellE>user_data</span>;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span><span
class=GramE>return</span> ret;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'>}</span> </p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>This example only handles the cases in which the destination
data type is integer.<span style='mso-spacerun:yes'> </span>The source data
type can be either integer or floating-point number.<span
style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>Cases of Exceptions</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>A number of exceptions may happen during conversion.<span
style='mso-spacerun:yes'> </span>These exceptions are</p>
<p style='margin-left:45.0pt'><span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_<span
class=GramE>HI<span style='font-size:12.0pt;font-family:"Times New Roman"'> :</span></span></span><span
style='mso-spacerun:yes'> </span>source value is positive and is too big to
the destination.<span style='mso-spacerun:yes'> </span>Overflow happens.<span
style='mso-spacerun:yes'>
</span><span style='mso-spacerun:yes'></span></p>
<p style='margin-left:45.0pt'><span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_LOW:</span>
source value is negative and its magnitude is too big to the destination.<span
style='mso-spacerun:yes'> </span>Overflow happens. </p>
<p style='margin-left:45.0pt'><span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_TRUNCATE:</span>
source is floating-point type and destination is integer.<span
style='mso-spacerun:yes'> </span>The floating-point number has fractional
part. </p>
<p style='margin-left:45.0pt'><span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_PRECISION:</span>
source is integer and destination is floating-point type.<span
style='mso-spacerun:yes'> </span>The mantissa of floating-point type is not
big enough to hold all the digits of the integer. </p>
<p style='margin-left:45.0pt'><span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_PINF:</span>
source is floating-point type and the value is positive infinity.</p>
<p style='margin-left:45.0pt'><span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_NINF:</span>
source is floating-point type and the value is negative infinity.<span
style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal style='margin-left:45.0pt'><span style='font-size:10.0pt;
font-family:"Courier New"'>H5T_CONV_EXCEPT_NAN:</span> source is floating-point
type and the value is <st1:place><span class=SpellE><span class=GramE>NaN</span></span></st1:place><span
class=GramE>(</span>not a number, including <span class=SpellE>QNaN</span> and <span
class=SpellE>SNaN</span>).</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Valid return values of the exception handling callback
function are <code><span style='font-size:10.0pt'>H5T_CONV_ABORT</span></code>,
<span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_UNHANDLED</span>
and <code><span style='font-size:10.0pt'>H5T_CONV_HANDLED</span></code>. <o:p></o:p></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal style='margin-left:.75in;text-indent:0in;mso-list:l0 level1 lfo1;
tab-stops:list .75in'><![if !supportLists]><b style='mso-bidi-font-weight:normal'><span
style='mso-fareast-font-family:"Times New Roman"'><span style='mso-list:Ignore'>IV.<span
style='font:7.0pt "Times New Roman"'> </span></span></span></b><![endif]><b
style='mso-bidi-font-weight:normal'>Soft Data Conversions<o:p></o:p></b></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal>This section is mainly for advanced users or library
developers who want to know the librarys behavior in performing soft data
conversion.<span style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>Understanding Bit Patterns of Arithmetic Data
Types</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>In order to understand data conversion, it will be helpful
for us to know about the bit patterns of arithmetic data types.<span
style='mso-spacerun:yes'> </span>Integers generally have simple bit
patterns.<span style='mso-spacerun:yes'> </span>Using the twos-complement
notation, a signed integer of <span style='font-size:10.0pt;font-family:"Courier New"'>n</span>
bits in size will have a range from -2<sup>n-1</sup> to 2<sup>n-1</sup>
1.<span style='mso-spacerun:yes'> </span>The high-order bit is the sign
bit.<span style='mso-spacerun:yes'> </span>There are <span style='font-size:
10.0pt;font-family:"Courier New"'>n-1</span> data bits.<span
style='mso-spacerun:yes'> </span>For unsigned integers, the high-order bit
becomes a data bit.<span style='mso-spacerun:yes'> </span>All the <span
style='font-size:10.0pt;font-family:"Courier New"'>n</span> bits are data
bits.<span style='mso-spacerun:yes'> </span>So an unsigned integer of <span
style='font-size:10.0pt;font-family:"Courier New"'>n</span> bit in size has a
range from <span style='font-size:10.0pt;font-family:"Courier New"'>0</span> to
<span style='font-size:10.0pt;font-family:"Courier New"'>2<sup>n</sup>1</span>.<span
style='mso-spacerun:yes'> </span>An example bit sequence of <span
style='font-size:10.0pt;font-family:"Courier New"'>(signed) char</span> of 1
byte long is like <span style='font-size:10.0pt;font-family:"Courier New"'>10010111</span>.<span
style='mso-spacerun:yes'> </span>The high-order (leftmost) bit is set to 1,
meaning the value is negative.<span style='mso-spacerun:yes'> </span>If the same
bit sequence represents an <span style='font-size:10.0pt;font-family:"Courier New"'>unsigned
char</span>, the high-order bit becomes a data bit, making the value be 151.<span
style='mso-spacerun:yes'> </span>Any implementation of C language has the
ranges of the native integer types documented in the header file <span
class=SpellE><span style='font-size:10.0pt;font-family:"Courier New"'>limits.h</span></span>.<span
style='mso-spacerun:yes'> </span>For example, the ranges of <span
style='font-size:10.0pt;font-family:"Courier New"'>short</span> type are <span
style='font-size:10.0pt;font-family:"Courier New"'>SHRT_MAX = 32,767</span> and
<span style='font-size:10.0pt;font-family:"Courier New"'>SHRT_MIN = -32,767</span>.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The floating-point number representation is more
complicated.<span style='mso-spacerun:yes'> </span>A more thorough description
of IEEE standard floating-point numbers can be found in the <i
style='mso-bidi-font-style:normal'>IEEE Standard 754</i> document.<span
style='mso-spacerun:yes'> </span>For IEEE standard floating-point numbers, there
are three components for a floating-point number, the sign, the exponent, and
the mantissa.<span style='mso-spacerun:yes'> </span>The diagram below shows
the layouts of IEEE <span style='font-size:10.0pt;font-family:"Courier New"'>float</span>
and <span style='font-size:10.0pt;font-family:"Courier New"'>double</span>
types.</p>
<p class=MsoNormal><o:p> </o:p></p>
<table class=MsoTableGrid border=1 cellspacing=0 cellpadding=0
style='margin-left:23.4pt;border-collapse:collapse;border:none;mso-border-alt:
solid windowtext .5pt;mso-yfti-tbllook:480;mso-padding-alt:0in 5.4pt 0in 5.4pt;
mso-border-insideh:.5pt solid windowtext;mso-border-insidev:.5pt solid windowtext'>
<tr style='mso-yfti-irow:0'>
<td width=87 valign=top style='width:65.15pt;border:solid windowtext 1.0pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Type<o:p></o:p></b></p>
</td>
<td width=118 valign=top style='width:88.55pt;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Sign<o:p></o:p></b></p>
</td>
<td width=118 valign=top style='width:88.55pt;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Exponent<o:p></o:p></b></p>
</td>
<td width=118 valign=top style='width:88.55pt;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Mantissa<o:p></o:p></b></p>
</td>
<td width=87 valign=top style='width:65.2pt;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Bias<o:p></o:p></b></p>
</td>
</tr>
<tr style='mso-yfti-irow:1'>
<td width=87 valign=top style='width:65.15pt;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>float<o:p></o:p></span></p>
</td>
<td width=118 valign=top style='width:88.55pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>1[31]</p>
</td>
<td width=118 valign=top style='width:88.55pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>8[30-23]</p>
</td>
<td width=118 valign=top style='width:88.55pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>23[22-00]</p>
</td>
<td width=87 valign=top style='width:65.2pt;border-top:none;border-left:none;
border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>127</p>
</td>
</tr>
<tr style='mso-yfti-irow:2;mso-yfti-lastrow:yes'>
<td width=87 valign=top style='width:65.15pt;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>double<o:p></o:p></span></p>
</td>
<td width=118 valign=top style='width:88.55pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>1[63]</p>
</td>
<td width=118 valign=top style='width:88.55pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>11[62-52]</p>
</td>
<td width=118 valign=top style='width:88.55pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>52[51-00]</p>
</td>
<td width=87 valign=top style='width:65.2pt;border-top:none;border-left:none;
border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>1023</p>
</td>
</tr>
</table>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The numbers are the size of each component.<span
style='mso-spacerun:yes'> </span>The bit index is in the square brackets.<span
style='mso-spacerun:yes'> </span>To calculate the true exponent value, the
bias has to be subtracted from the value represented by the bits of
exponent.<span style='mso-spacerun:yes'> </span>The mantissa represents the
precision bits.<span style='mso-spacerun:yes'> </span>The leading bit has been
implied.<span style='mso-spacerun:yes'> </span>When the true precision is
calculated, this implicit bit will be restored.<span style='mso-spacerun:yes'>
</span>Consider this bit sequence for float in little-endian order,</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><span
style='mso-tab-count:2'> </span>Byte 3<span style='mso-tab-count:
1'> </span>byte 2<span style='mso-tab-count:1'> </span>byte 1<span
style='mso-tab-count:1'> </span>byte 0<o:p></o:p></span></p>
<p class=MsoNormal style='text-indent:.5in'><span style='font-size:10.0pt;
font-family:"Courier New"'><span style='mso-spacerun:yes'> </span>11000011<span
style='mso-tab-count:1'> </span>11110000<span style='mso-tab-count:1'> </span>00000000<span
style='mso-tab-count:1'> </span>00000000</span> </p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The high-order (leftmost) bit is the sign bit.<span
style='mso-spacerun:yes'> </span>It is set to indicate the number is
negative.<span style='mso-spacerun:yes'> </span>The eight bits after the sign
bit, <span class=GramE><span style='font-size:10.0pt;font-family:"Courier New"'>10000111</span>
in <span style='font-size:10.0pt;font-family:"Courier New"'>byte 3</span> and <span
style='font-size:10.0pt;font-family:"Courier New"'>2</span>,</span> is the
exponent.<span style='mso-spacerun:yes'> </span>The value of these eight bits
is 135.<span style='mso-spacerun:yes'> </span>After subtracting the bias 127,
the true exponent is 8.<span style='mso-spacerun:yes'> </span>The 23 bits
after the exponent <span style='font-size:10.0pt;font-family:"Courier New"'>1110000
00000000 <span class=SpellE>00000000</span></span> in <span style='font-size:
10.0pt;font-family:"Courier New"'>byte 2, 1, 0</span>, is the mantissa.<span
style='mso-spacerun:yes'> </span>After restoring the implicit leading bit and
adding the radix, the mantissa becomes <span style='font-size:10.0pt;
font-family:"Courier New"'>1.1110000 00000000 <span class=SpellE>00000000</span></span>.<span
style='mso-spacerun:yes'> </span>The value of this float number is <span
style='font-size:10.0pt;font-family:"Courier New"'>1.111 x 2<sup>8</sup> =
111100000.0 = 480.0</span>.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>There are a few special values for floating-point numbers,</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'><span class=SpellE><i
style='mso-bidi-font-style:normal'>Denormalized</i></span> when exponent bits
are all 0s but mantissa bits are non-zero.<span style='mso-spacerun:yes'>
</span>There will be no implicit bit for the mantissa.</p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'><i style='mso-bidi-font-style:normal'>Zero</i>
when exponent and mantissa bits are all set to 0s.<span
style='mso-spacerun:yes'> </span>There can be both +0 and -0.</p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'><i style='mso-bidi-font-style:normal'>Infinity</i>
when exponent bits are all 1s and mantissa bits are all 0s.<span
style='mso-spacerun:yes'> </span>There can be both positive and negative
infinities.</p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'><st1:place><span class=SpellE><span
class=GramE><i style='mso-bidi-font-style:normal'>NaN</i></span></span></st1:place><span
class=GramE>(</span>Not a Number) when exponent bits are all 1s and mantissa bits
are not all 0s.<span style='mso-spacerun:yes'> </span><st1:place><span
class=SpellE>NaN</span></st1:place> can be either positive or negative.<span
style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>For other predefined or used-defined types, they should be
similar to IEEE standard.<span style='mso-spacerun:yes'> </span>There should
be the sign, exponent, mantissa, and bias.<span style='mso-spacerun:yes'>
</span>The bits of exponent or mantissa should be contiguous.<span
style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><span style='mso-tab-count:1'> </span><span
style='mso-spacerun:yes'></span></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>Between Integer and Integer Types</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Generally, converting from one integer type to another
should result in the same mathematical value.<span style='mso-spacerun:yes'>
</span>There are some cases that overflow may happen.<span
style='mso-spacerun:yes'> </span>If overflow happens, the library will let
users exception handling function to handle if this function is available.<span
style='mso-spacerun:yes'> </span>The two exceptions relating to this kind of
conversion are <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_HI</span>
and <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_LOW</span>.<span
style='mso-spacerun:yes'> </span>Otherwise, the librarys default way is to
assign maximal or minimal value to the destination type.<span
style='mso-spacerun:yes'> </span>To the library, the maximal value is that all
data bit of an integer is set to 1s.<span style='mso-spacerun:yes'> </span>The
minimal value is that all data bit of an unsigned integer is set to 0s, or that
only the sign bit of a signed integer is set to 1.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The following table lists all possible scenarios when
overflow can happen and the values assigned to the destination.</p>
<p class=MsoNormal><o:p> </o:p></p>
<table class=MsoTableGrid border=1 cellspacing=0 cellpadding=0
style='border-collapse:collapse;border:none;mso-border-alt:solid windowtext .5pt;
mso-yfti-tbllook:480;mso-padding-alt:0in 5.4pt 0in 5.4pt;mso-border-insideh:
.5pt solid windowtext;mso-border-insidev:.5pt solid windowtext'>
<tr style='mso-yfti-irow:0'>
<td width=148 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Source type<o:p></o:p></b></p>
</td>
<td width=148 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Destination type<o:p></o:p></b></p>
</td>
<td width=148 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>When source value
may be out of the range of destination and overflow happens<o:p></o:p></b></p>
</td>
<td width=148 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;mso-border-alt:
solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Value assigned to
destination when overflows<o:p></o:p></b></p>
</td>
</tr>
<tr style='mso-yfti-irow:1'>
<td width=148 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>unsigned</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>unsigned</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>source size > destination size</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>maximum</p>
</td>
</tr>
<tr style='mso-yfti-irow:2'>
<td width=148 rowspan=2 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>signed </p>
</td>
<td width=148 rowspan=2 valign=top style='width:110.7pt;border-top:none;
border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>unsigned</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>source data bit size > destination data bit size</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>maximum</p>
</td>
</tr>
<tr style='mso-yfti-irow:3'>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>source value < 0</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>0</p>
</td>
</tr>
<tr style='mso-yfti-irow:4'>
<td width=148 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>unsigned</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>signed</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>source data bit size > destination data bit size</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>maximum</p>
</td>
</tr>
<tr style='mso-yfti-irow:5'>
<td width=148 rowspan=2 valign=top style='width:110.7pt;border:solid windowtext 1.0pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;mso-border-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>signed </p>
</td>
<td width=148 rowspan=2 valign=top style='width:110.7pt;border-top:none;
border-left:none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>signed</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>source value < 0; source size > destination size</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>minimum</p>
</td>
</tr>
<tr style='mso-yfti-irow:6;mso-yfti-lastrow:yes'>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>source value > 0;</p>
<p class=MsoNormal>Source size > destination size</p>
</td>
<td width=148 valign=top style='width:110.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
mso-border-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal>maximum</p>
</td>
</tr>
</table>
<p class=MsoNormal><span style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>From Integer To Floating-point Number</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>When the library converts integer to floating-point number,
the result should be equal to the original value except two cases.<span
style='mso-spacerun:yes'> </span>One is when the mantissa of floating-point is
not big enough to hold all the digits of integer, there will be some precision
loss.<span style='mso-spacerun:yes'> </span>In this case, an exception of <span
style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_PRECISION</span>
will be returned if users exception handling has been registered with the
library.<span style='mso-spacerun:yes'> </span>Otherwise, the library will
round up or round down the source integer to the closest floating-point number.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Another case is when the integer value is beyond the range
of floating-point number, overflow happens.<span style='mso-spacerun:yes'>
</span>The exception <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_HI</span>
or <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_LOW</span>
is returned to users exception handling function.<span
style='mso-spacerun:yes'> </span>If users exception handling function is
absent, the library will assign the value of positive or negative infinity to
the destination.<span style='mso-spacerun:yes'> </span>However, this case does
not happen often because floating-point numbers have broad ranges.<span
style='mso-spacerun:yes'> </span><span style='font-size:10.0pt;font-family:
"Courier New"'><span style='mso-spacerun:yes'></span></span><span
style='mso-spacerun:yes'></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>4.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>From Floating-point Number To Integer</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The conversion from floating-point number to integer results
the same value if the floating-point number does not have fractional part.<span
style='mso-spacerun:yes'> </span>If the fractional part is non-zero, the
library will return an exception of <span style='font-size:10.0pt;font-family:
"Courier New"'>H5T_CONV_EXCEPT_TRUNCATE</span> to the users exception handling
function.<span style='mso-spacerun:yes'> </span>If this function is absent,
the library will discard the fractional part.<span style='mso-spacerun:yes'>
</span>The conversion from floating-point number to integer usually involves
truncating of the fractional part. </p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Because floating-point numbers normally have greater ranges
than integers, overflow may happen.<span style='mso-spacerun:yes'> </span>The
library returns the exceptions of <span style='font-size:10.0pt;font-family:
"Courier New"'>H5T_CONV_EXCEPT_RANGE_HI</span> and <span style='font-size:10.0pt;
font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_LOW</span> to the users
exception handling function.<span style='mso-spacerun:yes'> </span>If such
function is absent, the library will set the maximal (set all data bits to 1s)
or minimal (set all data bits to 0s for unsigned integer; set only the sign bit
to 1 for signed integer) values for the integer.<span
style='mso-spacerun:yes'> </span>This is similar to conversion between integer
and integer.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Floating-point numbers have some special values.<span
style='mso-spacerun:yes'> </span>These values are +/-0, +/-infinity, and <st1:place><span
class=SpellE>NaN</span></st1:place>.<span style='mso-spacerun:yes'>
</span>For +/-0, the library simply converts them to 0 for the integer.<span
style='mso-spacerun:yes'> </span>For +/-infinity, the exception <span
class=GramE>of<span style='mso-spacerun:yes'> </span><span style='font-size:
10.0pt;font-family:"Courier New"'>H5T</span></span><span style='font-size:10.0pt;
font-family:"Courier New"'>_CONV_EXCEPT_PINF</span> or <span style='font-size:
10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_NINF</span> is returned to
the users exception handling function.<span style='mso-spacerun:yes'>
</span>If no such function, the library will assign the maximal or minimal
values to the integer.<span style='mso-spacerun:yes'> </span>For <st1:place><span
class=SpellE>NaN</span></st1:place>, the library returns the exception <span
style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_NAN</span>.<span
style='mso-spacerun:yes'> </span>The librarys default way is to assign the
value 0 to the integer for <st1:place><span class=SpellE>NaN</span></st1:place>.<span
style='mso-spacerun:yes'> </span><span style='mso-spacerun:yes'></span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level2 lfo1;
tab-stops:list .5in'><![if !supportLists]><span style='mso-fareast-font-family:
"Times New Roman"'><span style='mso-list:Ignore'>5.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]>Between Floating-point and Floating-point
Numbers</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The conversion between two floating-point numbers involves
more issues to consider.<span style='mso-spacerun:yes'> </span>Converting from
a smaller floating-point number like <span style='font-size:10.0pt;font-family:
"Courier New"'>float</span> to a bigger type like <span style='font-size:10.0pt;
font-family:"Courier New"'>double</span> should result in the same value.<span
style='mso-spacerun:yes'> </span>Converting from a bigger type like <span
style='font-size:10.0pt;font-family:"Courier New"'>double</span> to a smaller
type like <span style='font-size:10.0pt;font-family:"Courier New"'>float</span>
has three problems to be taken care of.<span style='mso-spacerun:yes'> </span>One
is that if the source value is within the range of the destination, there can be
some precision loss because the source mantissa is bigger than the destination
mantissa.<span style='mso-spacerun:yes'> </span>The library will do rounding
to make the result be closest to the original value.<span
style='mso-spacerun:yes'> </span>Another one is that if the source value is
beyond the range of the destination, overflow happens.<span
style='mso-spacerun:yes'> </span>The library will return the exception of <span
style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_HI</span>
or <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_LOW</span>
to users exception handling function.<span style='mso-spacerun:yes'> </span>If
no such a function is present, the library will assign infinity to the
destination.<span style='mso-spacerun:yes'> </span>The third issue is that if
the source value is very small, the library will try to <span class=SpellE>denormalize</span>
the destination.<span style='mso-spacerun:yes'> </span>If it is still too
small for the destination, underflow happens.<span style='mso-spacerun:yes'>
</span>The library simply assigns 0 to the destination.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>For the special values of floating-point numbers, +/-0,
+/-infinity, and <st1:place><span class=SpellE>NaN</span></st1:place>, the
librarys default way is to assign the same special values to the
destination.<span style='mso-spacerun:yes'> </span>But if the users exception
handling function is present, the library will returns exception to it.<span
style='mso-spacerun:yes'> </span>For positive infinity, the exception is <span
style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_PINF</span>;
for the negative infinity, the exception is <span style='font-size:10.0pt;
font-family:"Courier New"'>H5T_CONV_EXCEPT_NINF</span>; for the Not a Number,
the exception is <span style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_NAN.</span></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal style='margin-left:.75in;text-indent:0in;mso-list:l0 level1 lfo1;
tab-stops:list .75in'><![if !supportLists]><b style='mso-bidi-font-weight:normal'><span
style='mso-fareast-font-family:"Times New Roman"'><span style='mso-list:Ignore'>V.<span
style='font:7.0pt "Times New Roman"'> </span></span></span></b><![endif]><b
style='mso-bidi-font-weight:normal'>Hard Data Conversions<o:p></o:p></b></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal>Because the details are handled by compilers, the library
has little control over hard conversion.<span style='mso-spacerun:yes'>
</span>The librarys control is mainly on overflow.<span
style='mso-spacerun:yes'> </span>When the source value is beyond the ranges of
the destination, overflow happens.<span style='mso-spacerun:yes'> </span>Just
like the soft conversion, the library will signal <span style='font-size:10.0pt;
font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_HI</span> or <span
style='font-size:10.0pt;font-family:"Courier New"'>H5T_CONV_EXCEPT_RANGE_LOW</span>
to users exception handling function.<span style='mso-spacerun:yes'>
</span>If no such a function is present, the library will assign maximal or
minimal values to the destination.<span style='mso-spacerun:yes'> </span>These
maximal or minimal values are found in the C librarys header file <span
class=SpellE><span style='font-size:10.0pt;font-family:"Courier New"'>limits.h</span></span>
for integers or <span class=SpellE><span style='font-size:10.0pt;font-family:
"Courier New"'>floats.h</span></span> for floating-point numbers.<span
style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>For integers, these values can be different from the maximal
and minimal values of soft conversion because they are defined by specific C
library implementation.<span style='mso-spacerun:yes'> </span>For example, the
<span style='font-size:10.0pt;font-family:"Courier New"'>INT_MAX</span> (maximal
<span class=SpellE><span style='font-size:10.0pt;font-family:"Courier New"'>int</span></span>)
can be defined as 32,767 and the <span style='font-size:10.0pt;font-family:
"Courier New"'>INT_MIN</span> (minimal <span class=SpellE><span
style='font-size:10.0pt;font-family:"Courier New"'>int</span></span>) can be
defined as -32,767.<span style='mso-spacerun:yes'> </span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>For floating-point numbers, the soft conversion sets the
destination to positive or negative infinity when overflow happens.<span
style='mso-spacerun:yes'> </span>The hard conversion will set to the maximal
values found in Cs header file <span class=SpellE><span style='font-size:10.0pt;
font-family:"Courier New"'>floats.h</span></span>.<span
style='mso-spacerun:yes'> </span>For example, the <span style='font-size:10.0pt;
font-family:"Courier New"'>FLT_<span class=GramE>MAX<span style='font-size:
12.0pt;font-family:"Times New Roman"'>(</span></span></span>maximal <span
style='font-size:10.0pt;font-family:"Courier New"'>float</span>) can be defined
as 10<sup>+37</sup> and the minimal value is simply <span style='font-size:
10.0pt;font-family:"Courier New"'>FLT_MAX</span>.<span
style='mso-spacerun:yes'> </span><o:p></o:p></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal style='margin-left:.75in;text-indent:0in;mso-list:l0 level1 lfo1;
tab-stops:list .75in'><![if !supportLists]><b style='mso-bidi-font-weight:normal'><span
style='mso-fareast-font-family:"Times New Roman"'><span style='mso-list:Ignore'>VI.<span
style='font:7.0pt "Times New Roman"'> </span></span></span></b><![endif]><b
style='mso-bidi-font-weight:normal'>Summary<o:p></o:p></b></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><o:p> </o:p></b></p>
<p class=MsoNormal>Generally speaking, during data conversion, the HDF5 library
tries to convert the original value to the same mathematical <span class=GramE>value,</span>
or close to the original value if the same value is not possible.</p>
<p class=MsoNormal><span style='mso-spacerun:yes'> </span><o:p></o:p></p>
<p class=MsoNormal>The way that HDF5 library deals with overflow and underflow may
not be the same as some C implementations.<span style='mso-spacerun:yes'>
</span>For the special values of floating-point numbers, the library may behave
differently from some C implementations, too.</p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'>Appendix:<o:p></o:p></b></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><strong>Name:</strong> <a name=Datatype-Find>H5T</a>is_hard </p>
<p class=MsoNormal><strong>Signature:</strong> </p>
<p class=MsoNormal style='margin-left:.5in'><span class=SpellE><em>herr_t</em></span>
<code><span style='font-size:10.0pt'>H5Tis_<span class=GramE>hard<span
style='font-size:12.0pt;font-family:"Times New Roman"'>(</span></span></span></code><span
class=SpellE><em>hid_t</em></span> <span class=SpellE><code><span
style='font-size:10.0pt'>src_id</span></code></span>, <span class=SpellE><em>hid_t</em></span>
<span class=SpellE><code><span style='font-size:10.0pt'>dst_id</span></code></span>)
</p>
<p class=MsoNormal><strong>Purpose:</strong> </p>
<p class=MsoNormal style='margin-left:.5in'>Check whether the librarys default
conversion is hard conversion. </p>
<p class=MsoNormal><strong>Description:</strong> </p>
<p class=MsoNormal style='margin-left:.5in'><code><span style='font-size:10.0pt'>H5Tis_hard</span></code>
finds out whether the librarys conversion function from type <span
class=SpellE><code><span style='font-size:10.0pt'>src_id</span></code></span>
to type <span class=SpellE><code><span style='font-size:10.0pt'>dst_id</span></code></span>
is a hard conversion.<span style='mso-spacerun:yes'> </span>A hard conversion
uses compilers casting; a soft conversion uses the librarys own conversion
function. </p>
<p class=MsoNormal><strong>Parameters:</strong> </p>
<table class=MsoNormalTable border=0 cellpadding=0 style='mso-cellspacing:1.5pt;
margin-left:.5in'>
<tr style='mso-yfti-irow:0'>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><span class=SpellE><em>hid_t</em></span> <span
class=SpellE><code><span style='font-size:10.0pt'>src_id</span></code></span></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal>IN: Identifier for the source <span class=SpellE>datatype</span>.</p>
</td>
</tr>
<tr style='mso-yfti-irow:1;mso-yfti-lastrow:yes'>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><span class=SpellE><em>hid_t</em></span> <span
class=SpellE><code><span style='font-size:10.0pt'>dst_id</span></code></span></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal>IN: Identifier for the destination <span class=SpellE>datatype</span>.</p>
</td>
</tr>
</table>
<p class=MsoNormal><strong>Returns:</strong> </p>
<p class=MsoNormal style='margin-left:.5in'>Returns TRUE for hard conversion,
FALSE for soft conversion. </p>
<p class=MsoNormal><strong>Fortran90 Interface:</strong> </p>
<p class=MsoNormal style='margin-left:.5in'><span class=GramE>None.</span><o:p></o:p></p>
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