Jeff King <peff@xxxxxxxx> writes: > Side note: The pretend_object_file() approach is actually even better, > because we know the object is fake. So it does not confuse > write_object_file()'s "do we already have this object" freshening > check. > > I suspect it could even be made faster than the tmp_objdir approach. > From our perspective, these objects really are tempfiles. So we could > write them as such, not worrying about things like fsyncing them, > naming them into place, etc. We could just write them out, then mmap > the results, and put the pointers into cached_objects (currently it > insists on malloc-ing a copy of the input buffer, but that seems like > an easy extension to add). > > In fact, I think you could get away with just _one_ tempfile per > merge. Open up one tempfile. Write out all of the objects you want to > "store" into it in sequence, and record the lseek() offsets before and > after for each object. Then mmap the whole result, and stuff the > appropriate pointers (based on arithmetic with the offsets) into the > cached_objects list. Cute. The remerge diff code path creates a full tree that records the mechanical merge result. By hooking into the lowest layer of write_object() interface, we'd serialize all objects in such a tree in the order they are computed (bottom up from the leaf level, I'd presume) into a single flat file ;-)
