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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I have added a header file “napiu.h” to CVS (see
<a
href="http://nexus.isis.rl.ac.uk/cgi-bin/viewcvs.cgi/include/napiu.h?rev=1.1&content-type=text/vnd.viewcvs-markup">http://nexus.isis.rl.ac.uk/cgi-bin/viewcvs.cgi/include/napiu.h?rev=1.1&content-type=text/vnd.viewcvs-markup</a>)
containing the C declarations for NXU routines – I have taken as a basis
the F90 implementation as detailed at <a
href="http://www.nexus.anl.gov/nexus_f90.html#NXUwriteglobals">http://www.nexus.anl.gov/nexus_f90.html#NXUwriteglobals</a>
This page mentions NXUwritehistogram and NXUreadhistogram functions, though
these are not currently implemented in NXUmodule.f90; are they still required?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Though the C signature of the functions can be the same as
the F90 ones in most cases, there are a few exceptions. The C NXUwritedata
cannot follow the F90 one exactly as F90 arrays know their size and so do not
require such parameters; also F90 allows several functions for different array
types/dimensionality to be written and a general “interface” to be
defined that will map to the correct function at compile time. I have thus
added additional size, rank and type parameters to NXUwritedata and NXUreaddata</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>A general question concerns memory allocation: should the
NXU functions allocate memory for the caller or rely on being provided with a
buffer of at least the correct size; if the latter, then should extra size
parameters be added so that buffer overruns are detected? The functions concerned
are:</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>NXUreadhistogram and NXUreaddata – allocate space for
returned data or assume this will be provided?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>NXUfindgroup – allocate space for group_class output
variable or assume this will be provided?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>NXUfindclass – allocate space for group_name output
variable or assume this will be provided?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>NXUfindsignal – allocate space for data_name and data_dimensions
output variables or assume this will be provided?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>NXUfindaxis – allocate space for data_name and data_dimensions
output variables or assume this will be provided?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>If we were to prototype as e.g. (char** value), we could
only allocate memory if we are passed (*value == NULL) which would allows both
memory options, but does not address the buffer overrun issue.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Regards,</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Freddie </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
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