If you split the file into multiple files (AppleDouble), you have to play games with the sort routine, or else you risk FS corruption. And it's very inconvenient to be certain that your sort trick had the desired results.
rsync uses qsort(3) after building the whole file list. At least that's the case in rsync-2.6.0. See:
send_file_list() around line 1066 of flist.c
qsort is specified in the C89 standard. The compare function is passed to this routine by rsync. So if there are sort-order vagaries, they would represent a basic bug in rsync.
To fake up the second file, I might suggest a change either to make_file() or in send_file_name(), right after make_file() is called.
Unless you know a bit about the destination FS (specifically what ASCII vals are allowed in filenames), you might still get it wrong.
Again, I'm not aware that rsync supports ideas like file name "munging". The issue you describe is general, not anything to do specifically with supporting, e.g., AppleDouble.
Another problem with file conversion in-stream is what to do with the converted file on the source system. You could store it as a tmp file somewhere, (bad, again creating the different filename/sort order problem which seems to require a protocol revision to solve) or you could hold it in memory (and possibly create enormous memory requirements) and then patch all of the functions that get file comparison info (size, ctime, mtime, checksum, etc) to deal with memory blocks (even worse, and you still create the same problem to safely put the new file into a different filename on the destination).
A tmp file would be "dirty". Assuming AppleDouble, the header portion of the file is a fixed size, i.e., not enormous. The actual contents of the resource fork can be treated like any other file. So the only requirement is for the sender to handle the header specially and to adjust byte offsets in the resource fork by the size of the fixed header.
I'd love to be wrong about requiring a protocol rev. I just can't find an opportunity in the code. I'm still looking. :-)
The above sounds like a recipe to me. The question is, is something like this acceptable to the maintainers?
:wes
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