Serde

Serde support sits behind the serde Cargo feature (enabled by default; dropped under default-features = false — see Cargo features). Every width implements Serialize / Deserialize, choosing its encoding from the serializer's is_human_readable flag.

Wire format

For human-readable formats (JSON, TOML, YAML) the wire format is the raw scaled-integer storage rendered as a base-10 string — not the displayed decimal value. D38s12::ONE serialises as "1000000000000" (the storage 1 × 10^12), and a native integer in the payload is likewise read as storage: the JSON number 1 deserialises to 0.000000000001 at scale 12, not to 1.0.

Cross-system warning: the wire value is meaningless without the SCALE. The scale is a compile-time type parameter and is not encoded in the payload, so any other system reading or writing this data must agree on the scale out-of-band. Treating the wire value as a plain number yields a result 10^SCALE times too large.

The integer-string form is deliberate: it is the only lossless, JavaScript-BigInt-compatible encoding for storage values wider than the 53-bit safe-integer range of a JSON number.

Binary formats

Binary formats (postcard, bincode) carry the same storage as raw little-endian bytes — no string round-trip, same exact value.

Round-tripping

Because the wire value is the storage integer, serialise → deserialise at the same width and scale is always bit-exact: no parsing, no rounding, no normalisation. To exchange values with a system that expects the displayed decimal instead, format with Display and parse with FromStr explicitly — that path is also exact at the type's scale.