perf: O(children) directory lookups via reverse index#356
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perf: O(children) directory lookups via reverse index#356Koan-Bot wants to merge 1 commit intocpan-authors:mainfrom
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Replace O(total_mocks) full-hash scans in _files_in_dir() and the dir() constructor with O(children) lookups using a %_dir_children reverse index. The index maps each ancestor directory to the set of descendant paths registered under it. Maintained at mock registration (new, autovivify, broken-symlink creation), destruction (DESTROY), and rename re-keying — the same five mutation points that touch %files_being_mocked. For test suites with many mocked files, this eliminates per-readdir and per-rmdir linear scans of the entire mock registry. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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What
Replace O(total_mocks) linear scans with O(children) indexed lookups for directory-related operations.
Why
_files_in_dir()scans every key in%files_being_mockedon each call. It's used by readdir (contents()), thedir()constructor'shas_contentcheck, and the ENOTEMPTY checks inrmdirandrename. For test suites with many mocked files, this is a hot path paying unnecessary O(n) cost.How
New
%_dir_childrenreverse index maps each ancestor directory to its set of descendant mock paths. Maintained at the same 5 mutation points that already touch%files_being_mocked:new()constructor (registration)_create_file_through_broken_symlink()_maybe_autovivify()DESTROY()(cleanup)__rename()re-keying loopEach path registers under ALL ancestor directories (not just the immediate parent), preserving the existing semantics where
_files_in_dir('/a')returns descendants at any depth.Testing
Full test suite passes (94 files, 1586 subtests). Initial run caught a semantic mismatch (direct-parent-only vs all-ancestors) in globbing.t — fixed before push.
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