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rust: add `dirstate_tree` module

Authored by Alphare.

Description

rust: add dirstate_tree module

Mercurial needs to represent the filesystem hierarchy on which it operates, for
example in the dirstate. Its current on-disk representation is an unsorted, flat
structure that gets transformed in the current Rust code into a HashMap.
This loses the hierarchical information of the dirstate, leading to some
unfortunate performance and algorithmic compromises.

This module adds an implementation of a radix tree that is specialized for
representing the dirstate: its unit is the path component. I have made no
efforts to optimize either its memory footprint or its insertion speed: they're
pretty bad for now.

Following will be a few patches that modify the dirstate.status logic to use
that new hierarchical information, fixing issue 6335 in the same swing.

Differential Revision: https://phab.mercurial-scm.org/D9085

Details

Committed
AlphareSep 25 2020, 11:51 AM
Differential Revision
D9085: rust: add `dirstate_tree` module
Parents
rHG80bf7b1ada15: rust-dirstatemap: add #[timed] to dirstatemap read for comparison
Branches
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