2005.03.30 03:30 "Re: [Tiff] RFC: fast 'copy free' tiff decoding", by Bob Friesenhahn
The basic idea is very simple. First map a tiff into memory, then cast carefully constructed C structures into the right offsets of that memory space to be able to access the data directly.
What problem are you trying to solve? Fixing the private IFD access should not require re-implementing the whole library! :-)
I agree that mmap() is cool, but libtiff already uses it to read files, just not quite as efficiently as it could. Requiring mmap() would make libtiff less portable.
Based on my own testing, libtiff's performance is quite good. The library is very robust and well tested.
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/