Dear All,

If nifticlib is to be reworked, can I propose contemplating the clean up file i/o section of nifticlib?

The current solution works, so I am not sure whether it is a good idea to clean up file i/o. But since the worst I will get is someone flaming me and that is unlikely on this forum, I will say my piece and leave it at it.

The issue is the physical file read/write part of nifticlib has to deal with four different formats (hdr/img, nii and their gzip counterpart). The current system effectively requires the niftilib read write function to deal with it themselves. This results in quite a lot of code looking like this:

  if (filetype==hdr) then writeHdrImg()
  else if (filetype==hdr.gz) then writeHdrImgGz()
  else if (filetype==nii) then writeNii()
  else if (filetype==nii.gz) then writeNiiGZ()

As each function has to implement this, it becomes a nightmare to introduce new read/write as all functions doing read/write has to be updated. If nifticlib maintainer wants to introduce the ability to read and write nifti1 and nifti2 simultaneously in this update, another 4 formats (for nifti 2) has to be supported.

I think a better solution worth considering is to use function pointers. This way, say we simply need one read and one write function. We modify nifti_image struct to carry function pointers for the two, e.g.

  struct nifti_image {
    ...
    *(fn_read)(...)
    *(fn_write)(...)
  }

and each of the file format supported will define its own fn_read and fn_write function, e.g.
  * hdr     : fn_hdr_read(...)/fn_hdr_write(...)
  * hdr.gz: fn_hdrgz_read(...)/fn_hdrgz_write(...)
  * nii     : fn_nii_read(...)/fn_nii_write(...)
  * nii.gz: fn_niigz_read(...)/fn_niigz_write(...)

Then, a function will be responsible for attaching the correct set of function pointers to nifti_image, say
  function setIOPointers(nim) {
      if (hdr) { nim->fn_read = fn_hdr_read; nim->fn_write=fn_hdr_write; }
      ...
  }

This way, any function that needs to read/write simply has to call
    nim->fn_read()
or
   nim->fn_write()
instead of the if-else statement in the first example

The advantage is we centralize all read/write function maintenance at one place and make it easier to introduce new format or take old format out.

Thanks and HTH
Cinly