C Version of NXU utility routines

[Freddie Akeroyd]

A C version of the FORTRAN 90 NXU* routines needs to be implemented

[Freddie Akeroyd]

I have added a header file "napiu.h" containing the C declarations for NXU routines - I have taken as a basis the F90 implementation as detailed in the NXU* module. The old web pages mention NXUwritehistogram and NXUreadhistogram functions, though these are not currently implemented in NXUmodule.f90; are they still required?

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

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:

NXUreadhistogram and NXUreaddata - allocate space for returned data or assume this will be provided?

NXUfindgroup - allocate space for group_class output variable or assume this will be provided?

NXUfindclass - allocate space for group_name output variable or assume this will be provided?

NXUfindsignal - allocate space for data_name and data_dimensions output variables or assume this will be provided?

NXUfindaxis - allocate space for data_name and data_dimensions output variables or assume this will be provided?

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.

Cheers,

Freddie

[Peter Peterson]

Caller should allocate the memory for NXUreadhistorgram and similar functions. There will be a parallel function NXUreadhistogrammalloc which allocates memory.

[Peter Peterson]

(In [1447]) Fixed error in fixing the percent differences to avoid nans. Refs #1.

[Peter Peterson]

No longer needed.