Crate oxgraph_layout_util 

Shared layout primitives for OxGraph graph and hypergraph crates.

Three responsibilities live here:

• Index/word vocabulary (LayoutIndex, LayoutWord, LayoutSnapshotWord, SnapshotWidth): the single sealed set of dense index widths, native/little-endian storage words, and the width-to-LE-word bijection shared by every layout and snapshot crate. CSR and BCSR add only thin section-kind-bearing sub-traits on top.
• Build-time (id_to_slot, slot_or_max, index_from_usize, build_offset_index, slice_to_le, map_offset_overflow): validate dense IDs against a known count, convert usize slots back into a typed index width, flatten per-bucket payloads into CSR-style (offsets, items) pairs, and lower native index slices into explicit little-endian words.
• Read-time (OffsetIntegrityIssue, check_offsets_monotonic, check_value_range, check_offset_section, index_to_usize_validated, usize_to_index_validated): walk borrowed offset arrays at view-open time and convert already-validated indexes infallibly.

Helpers return small typed data enums (IdOutOfBounds, OffsetOverflow, OffsetIntegrityIssue) instead of crate-specific error types. Callers map the issue to their own typed error at the boundary.

LocalId is the one generic local-handle newtype every layout crate aliases for its node/edge/vertex/hyperedge/incidence identities, and IdSlice is the one slice-to-handle iterator they all reuse.

no_std + alloc (build-time primitives need Vec). No public domain semantics. No dependency on any other oxgraph crate.

Structs

EdgeAxis

Relation axis for binary graphs (an edge).

HyperedgeAxis

Relation axis for hypergraphs (a hyperedge).

IdSlice

Iterator that maps a borrowed slice of LayoutWords into axis-branded handles, recovering each logical index and wrapping it with Id::from.

IncidenceAxis

Incidence axis (a participant / endpoint).

LocalId

A dense local handle: an axis-branded index value.

NodeAxis

Element axis for binary graphs (a node).

VertexAxis

Element axis for hypergraphs (a vertex).

Enums

IdOutOfBounds

Reasons an ID failed dense bounds validation.

OffsetIntegrityIssue

Reasons a borrowed offset or value array failed structural validation.

OffsetOverflow

Reasons a usize could not be represented in a target index width during builder offset construction.

Traits

Axis

Marker for a local-handle axis (node, edge, vertex, hyperedge, incidence).

LayoutIndex

Unsigned dense ID width usable by graph and hypergraph layouts and builders.

LayoutSnapshotWord

A little-endian storage word usable in persisted snapshot payloads.

LayoutWord

A native-host or little-endian word carrying a typed dense LayoutIndex.

SnapshotWidth

A persisted unsigned width with its little-endian storage word.

ZerocopyWord

Borrowed offset or value word usable by offset-integrity primitives.

Functions

build_offset_index

Flattens per-bucket payloads into a (offsets, items) pair.

check_offset_section

Validates one offset section against expected_count rows and a backing values array of length value_len.

check_offsets_monotonic

Verifies offsets[0] == 0 and that offsets is non-decreasing.

check_value_range

Verifies every value in values is less than bound.

id_to_slot

Validates that id’s usize representation is less than count.

index_from_usize

Converts a usize value into the target index width.

index_to_usize_validated

Converts an already-validated index into usize.

map_offset_overflow

Maps an OffsetOverflow into a caller-chosen error via on_overflow.

slice_to_le

Lowers a native index slice into explicit little-endian storage words.

slot_or_max

Returns id’s usize representation, or usize::MAX when it does not fit in usize on the current target.

usize_to_index_validated

Converts an already-validated usize slot into the target index width.