On Nov 16, 2017, at 2:21 PM, Nathan Rusch <[email protected]> wrote:
> Beyond some level of trickery, header changes to a format with a 
> variable-sized header would pretty much always necessitate a complete rewrite 
> of the data portion in one way or another, no?

Yeah, but you could imagine a format in which the data was organized a bit like 
a linked list, where it could put new metadata at the end of the file, and then 
just change a few header bytes in-situ that indicates where the next appended 
metadata hunk starts. And you could put a reasonable amount of padding at the 
front so that it was easy to add a few small items at the beginning without 
even needing to append to the end.

The incoherent seeking behavior (to the extent that we even care in an 
SSD-based world) wouldn't be optimal, but you could make it so that any "copy" 
operation of the file might automatically "defragment", so it would be easy to 
to clean up if you had a whole lot of accumulated changes.

--
Larry Gritz
[email protected]




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