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

[Blezek, Daniel J (GE, Research)]

Hi Kent,

  I'm having problems with NIfTI on my 32 bit machine as well, it writes
352 bytes.  It seems to Analyze doesn't like the 352 byte NIfTI header.
It was my understanding that NIfTI just used unused fields in the
Analyze header.  I also don't like that Analyze is never used, as it's
after Nifti in itkImageIOFactory.  Seems to break our model.

For the moment, I switched Nifti and Analyze in the IOFactory.  I'll not
check it in, but perhaps we should think a bit about this issue of 2
formats that share header extentions.

-dan

kent williams wrote:
> 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.   
> 
> 
> 
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