1999.06.07 13:03 "Re: Large File Support", by Frank Warmerdam

I'd prefer the professional way rather than the quick-and-dirty one: If offsets in the file are changed to be 64 Bit, then ALL offsets should be changed.

Rainer,

Given time to reflect, I agree that my proposal would lead into a morass of problems somewhat akin to segmented programming on the x86. I agree that a better approach is 64bit offsets used everywhere offsets apply.

In addition, some other changes could be discussed in this context:

• the 'Count' field in the Directory Entry should also be 64 bit. This will not be neccessary for today's needs, but who knows what tomorrow will bring us.
• maybe the 'Tag' field should be extended to 32 bit. This is only to avoid a further redefinition of the basics of TIFF.
• maybe the 'Type' field should be extended to 32bit. This would make the Directory Entry size a multiple of 8.

I suppose that since the directory format would already have to change to handle the 64bit NextIFD, and Offset values, it wouldn't hurt to do the rest.

• as the size of the offset is now 64 bit, more data (e.g. 8 bytes) can be packed in the offset field without the need for redirection.

I suppose so.

Because this approach requires fundamental changes to the directory format I think it will be significantly harder to pull off than the offset32 approach. Now I am waffling again. It makes my brain hurt.

Regards,

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