Elamur Groupantsvfs-memory-directories
The groupant beside vfs/src/mem.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.
Facts
Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.
Components
| component | label | where |
|---|---|---|
| approximant | partial | approximant |
| ast | partial | ../syntax.json |
| composition | partial | composition |
| cost | partial | Cost |
| descriptant | present | descriptant |
| invariant | partial | Invariant |
| tests | executed bounded checks | tests |
Obernants
The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.
| id | type | label | where |
|---|---|---|---|
behavior_complement | behavior_complement | partial source derived model | behavior_complement |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
rename_order | rename_order | partial source derived model | rename_order |
remove_weight | remove_weight | partial source derived model | remove_weight |
permission_scope | permission_scope | partial source derived model | permission_scope |
partial_mkdir | partial_mkdir | partial source derived model | partial_mkdir |
Model text
descriptant
vfs-memory-directories
Metadata, directory mutations, rename, links and cwd.
Prospective epoch
2026-10-31: source reviewed before edits; prospective review retained under $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31/prospective.md. Predicted order/cost: Directory reads O(k+names); recursive weight O(subtree nodes); rename path lookups plus COW parent map copies; mkdir_all repeats prefix resolution, potentially quadratic path work.
Observation epoch
Bounded actual calls and compiled negative controls are recorded in tests.md. Production behavior bytes unchanged; only focused test blocks added. Snapshot constant-time wording is conditional on cwd and destruction; recursive operations may partially commit.
Unsupported approximants
No executable percentage surrogate is claimed for these categorical/state/effect observations. Future 1%,2%,5%,10% require a useful metric, explicit domain and exact reference.
approximant
Forward relation
Metadata, directory mutations, rename, links and cwd.
stat follows optionally and rejects trailing slash nondirectory. mkdir_all iterates prefixes. remove computes subtree weight before unlink. rename resolves source/destination, rejects root/self-descendant/type mismatch, checks both parents then removes source and inserts same Arc, subtracting overwritten weight. chmod masks07777; set_mtime updates ctime to tick; chdir changes cwd.
Domain: bounded inputs with available allocation and nonoverflowing counters unless checked explicitly. The relation is partial and source-derived.
composition
Composition
Metadata, directory mutations, rename, links and cwd. Shared state and order: stat follows optionally and rejects trailing slash nondirectory. mkdir_all iterates prefixes. remove computes subtree weight before unlink. rename resolves source/destination, rejects root/self-descendant/type mismatch, checks both parents then removes source and inserts same Arc, subtracting overwritten weight. chmod masks07777; set_mtime updates ctime to tick; chdir changes cwd.
Scoped children project this same source. Their domains and effects remain conditional; source execution connects these clauses rather than independently proving their wiring. Rename same canonical path succeeds without tick; nonempty destination directory rejected. Removing root Busy. read_dir uses sorted BTree names; chmod/read checks owner bits, no execute-bit traversal model.
models
Typed source models
Source-bound partial relations; no universal finite-test proof.
behavior_complement
Subject: vfs-memory-directories. Domain: Metadata, directory mutations, rename, links and cwd. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Directory cannot be moved beneath itself; ordinary remove_dir cannot delete nonempty directory; root removal does not succeed.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
reverse_reconstruction
Subject: vfs-memory-directories. Domain: Metadata, directory mutations, rename, links and cwd. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Rename loses overwritten destination and old name; metadata times can map many operations to same saturating clock. Sorted entries omit mutation chronology.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
rename_order
Subject: vfs-memory-directories. Domain: Metadata, directory mutations, rename, links and cwd. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Destination resolve occurs before source lookup; identical path returns before parent write checks.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
remove_weight
Subject: vfs-memory-directories. Domain: Metadata, directory mutations, rename, links and cwd. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Usage subtracts all regular bytes and all removed nodes including directory; symlink text contributes0 bytes.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
permission_scope
Subject: vfs-memory-directories. Domain: Metadata, directory mutations, rename, links and cwd. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Only owner read/write bits checked; access traversal is not full POSIX permission semantics.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
partial_mkdir
Subject: vfs-memory-directories. Domain: Metadata, directory mutations, rename, links and cwd. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Earlier created prefixes persist if later quota/type/path check fails.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
tests
Checks and limitations
Exact named observations: escape_by_dotdot_is_denied, symlinks_cannot_lead_outside, bad_names_and_paths, limits_fire_with_clear_errors_and_leave_state_unchanged, limits_parse, snapshot_changes_restore_is_byte_identical, snapshot_is_isolated_copy_on_write, restore_after_failed_ops_and_limits, posix_like_semantics, virtual_clock_is_deterministic, journal_records_ops_errors_and_denials, import_export_round_trip, dirfs_confines_to_root, gates_green_and_negative_controls_red, wave31_sparse_copy_and_partial_directory_failure.
Fresh receipts: $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31; run.sh retains four profile/repetition sets with raw logs and numeric statuses. native-commands.json and source-test-map.json disambiguate targets. Compiled mutations and exact restoration are separately retained in mutation-summary.json.
These finite observations are not semantic completeness. Source syntax generated twice and compared byte-for-byte. Host effects are limited to owned TMPDIR fixtures. Existing absolute_paths_never_reach_the_host and open_modes are skipped; snapbench main is skipped. Standalone helpers/reexports are only observed through named callers or representation checks; RealFs effect methods unexecuted.
invariant-and-cost
Invariant and cost
Invariant
Rename same canonical path succeeds without tick; nonempty destination directory rejected. Removing root Busy. read_dir uses sorted BTree names; chmod/read checks owner bits, no execute-bit traversal model.
Cost
Directory reads O(k+names); recursive weight O(subtree nodes); rename path lookups plus COW parent map copies; mkdir_all repeats prefix resolution, potentially quadratic path work.
No timing or numerical error guarantee is inferred from finite tests.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/directories.groupant/