2004.09.17 13:11 "Re: [Tiff] BigTIFF Tag Value Count issue", by Frank Warmerdam

This does raise an interesting question. I would personally like libtiff to continue working on platforms with no identifiable 64bit integer data type if practical. Of course it would be fine if it only supported files smaller than 4GB in this case.

Does anyone know if stuff like PDA's and such have efficient-to-use 64bit integer datatypes? I am somewhat doubtful.

Is it allowable to have BigTIFF not work on those machines, but have classic TIFF still in working order? Perhaps a structure like...

#ifdef BIGTIFF_SUPPORT
if file is tiff classic {
#endif
  tiff classic supporting code
  ** this includes reporting error when suffering the consequences
       of getting a BigTIFF file **
#ifdef BIGTIFF_SUPPORT
} else {
  bigtiff supporting code
}
#endif

Joris,

I don't see any compelling reason libtiff could not be made to support bigtiff files smaller than 4GB on machines without a 64bit integer type. I would forsee the toff_t (and possibly tsize_t) types being 64 bits on platforms that allow it and 32bit otherwise. The code that reads the tags would need a special case for non-64bit-int platforms to downcast the values and throw some sort of error if there are any values that don't fit in a 32bit value.

While I imagine it will be some time till BigTIFF support catches on for general use, I would not want to preclude it's use in all environments.

Best regards,

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