Building block view

arc42 §4 — the building blocks that realise the toolchain, one crate per block. The dependency graph is Toolchain layering (crate d... (ARCH_0081); this page records each crate’s job, public surface, and the dependencies it is and is not allowed to carry.

The diagram below reads the same crates as a public-API pipeline: each layer’s output type is the next layer’s input, from .dbc bytes through to the WireType surface the generated code implements.

        graph LR
    dbc["DBC text<br/>&str"]
    c["BB_0117 taktora-idl-core<br/>Module / Struct / Field IR<br/>validate() + max_serialized_len()"]
    w["BB_0118 taktora-idl-wire<br/>WireType + pack/unpack<br/>(no_std, no deps)"]
    d["BB_0119 taktora-idl-dbc<br/>parse() → DbcDatabase<br/>lower() → (Module, DbcLayout)"]
    g["BB_0114 taktora-idl-codegen<br/>resolve() + generate&lt;B&gt;<br/>naming + collision policy"]
    b["BB_0115 taktora-idl-codegen-can<br/>CanBackend: MessageBackend impl"]
    t["BB_0116 taktora-idl-codegen-can-tests<br/>build.rs round-trip harness"]

    dbc -->|"parse()"| d
    c -.->|"IR types"| d
    d -->|Module| g
    d -->|DbcLayout| b
    g -->|ResolvedModule| b
    b -->|TokenStream| t
    w -.->|generated code calls| t
    

Building Block: taktora-idl-core BB_0117

status: implemented implements: FEAT_0111 links incoming: FEAT_0110, REQ_0946, REQ_0947, REQ_0948

The bounded message-type IR. Pure data carriers: Module, Struct, Field, EnumDef, EnumVariant, Service, Type (Scalar / String{capacity} / Array / Sequence{capacity} / Struct / Enum), and Scalar. validate enforces structural soundness; max_serialized_len returns the finite bound. No wire format, no transport dep, no proc-macro2/quote.

Building Block: taktora-idl-wire BB_0118

status: implemented implements: FEAT_0112 links incoming: FEAT_0110, REQ_0949, REQ_0950, REQ_0951

The runtime crate. WireType (MAX_SERIALIZED_LEN const, plus encode/decode over &[u8]), the WireError closed error set, ByteOrder, and the pack_unsigned / pack_signed / unpack_unsigned / unpack_signed bit primitives addressing both DBC bit-numbering conventions. #![no_std], allocation-free, zero external dependencies.

Building Block: taktora-idl-dbc BB_0119

status: implemented implements: FEAT_0113 links incoming: REQ_0952, REQ_0953, FEAT_0110

The DBC frontend. parse(text) -> Result<DbcDatabase, ParseError> builds a faithful model (messages, signals, value tables, multiplexers); lower(&db, name) -> Result<LoweredDbc, LowerError> emits an idl_core::Module plus a DbcLayout sidecar (FrameLayout / SignalLayout) keyed by source name. Depends on taktora-idl-core; no codegen or transport dep.

Building Block: taktora-idl-codegen BB_0114

status: implemented implements: FEAT_0114 links incoming: REQ_0954, REQ_0955, FEAT_0110

The plane-generic codegen layer. Owns the naming policy (PascalCase / snake_case, keyword escaping, leading-digit prefixing) and its collision detection; defines the MessageBackend trait (preamble / emit_enum / emit_struct); exposes resolve (→ ResolvedModule with idents chosen and fields classified by FieldKind) and generate (→ proc_macro2::TokenStream). Names no wire format.

Building Block: taktora-idl-codegen-can BB_0115

status: implemented implements: FEAT_0115 links incoming: REQ_0956, FEAT_0110

The concrete CAN backend. CanBackend::new(&DbcLayout) implements MessageBackend, emitting one WireType impl per message struct whose encode/decode bit-pack each field via the taktora-idl-wire primitives at the DBC-declared placement. Integer and enum fields this round; bool/float rejected. Depends on taktora-idl-codegen and taktora-idl-dbc.

Building Block: taktora-idl-codegen-can-tests BB_0116

status: implemented implements: FEAT_0115 links incoming: REQ_0957

The build-time verification harness (publish = false). Its build.rs runs the full .dbc → IR → codegen → format pipeline over a fixture database and writes the generated module to OUT_DIR; the crate compiles that module and round-trips it in tests. The slice’s proof-of-life that generated WireType code actually compiles and whose encode/decode agree.

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