This ended up a little different than I had originally planned.
The bad part is that my idea for the 'prevlnk' references wasn't going
to work out. For one because the reader has no efficient way to
determine the head reference of this list and implementing a lookup
table would be pretty costly and complex, and second because even with
those references working, they'd be pretty useless because there's no
way to go from an itemref to a full path. I don't see an easy way to
solve these problems, so I'm afraid the efficient hardlink list feature
will have to be disabled when reading from this new format. :(
The good news is that removing these references simplifies the hardlink
counting implementation and removes the requirement for a global inode
map and associated mutex. \o/
Performance is looking really good so far, too.
The goals of this format being:
- Streaming parallel export with minimal mandatory buffering.
- Exported data includes cumulative directory stats, so reader doesn't
have to go through the entire tree to calculate these.
- Fast-ish directory listings without reading the entire file.
- Built-in compression.
Current implementation is missing compression, hardlink counting and
actually reading the file. Also need to tune and measure stuff.
