Module schema 

Layer schema — the table-of-contents for one layer’s attributes + geometry + CRS.

Structure

• fields: Vec<FieldDef> — attribute columns in declared order. Order is the public contract: DBF row layout, Arrow column indices, FileGDB row-blob nullable bitmap all derive from it. Lookup-by-name is available via field_index(name) against a precomputed HashMap.
• geometry: Option<GeomField> — optional because attribute-only tables exist (GDB system tables, DBF sidecars).
• crs: Crs — the source CRS, carried through verbatim. Readers populate it from .prj / GDB geom-field metadata / GeoParquet geo metadata / etc. Writers serialize it in each format’s native form (WKT / PROJJSON / EPSG code / nothing).

Clever bits

• validate_row typechecks an attribute vector against the schema before writers ingest it — arity, type tags, nullability.
• name_index is private so callers can’t desync it with fields; it’s rebuilt on every Schema::new. Adding fields requires a fresh Schema, not a mutation.

Structs

FieldDef

GeomField

Per-layer geometry column metadata.

Schema