[Insight-developers] NIfTI and Analyze 64-bit lossage

[kent williams]

The problem, with both NIfTI and Analyze is that the file format -- and the
code used to read and write them, are grounded in a 1991, 32-Bit-Only
mindset.  The problem that Dan Blezek encountered is one of structure
alignment, not of integer size.

I can test integer size in my own abbreviated version of stdint, and not
wory too much about a hypothetical platform that has no 32 bit integer type.
Is there such an architecture? If sizeof(short int) == 16, and sizeof(int)
== 64, what would they call a 32-bit int? 'long short int'?

I have other assignments on my plate at the moment, but I know how to fix
things, in niftilib and itkAnalyzeImageIO, and will work on it in the next
week or so.  

1. Modify niftilib so that instead of putting sizeof(Header) in the
sizeof_hdr field, put in 348.

2. Modify the header readers and writers so that they read the 348 bytes of
the header, and then extract the various fields from the header at their
mandated offsets in the header.  On writing, similarly, place each attribute
at it's proper offset.

In any case, there's still only one read/write per header.  Even explicitly
reading each field one at a time wouldn't cause a performance penalty, since
we're only talking about 348 bytes, read or written once per file.