SBE Feature Tour

Standalone laboratory sample for ergo-sbe (publish = false). This is the crates.io / docs.rs teaching entry.

Conversion: three styles in one crate

build.rs uses different APIs for different selectors:

#![allow(unused)]
fn main() {
    let generated_dir = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("src/generated");
    let config = ergo_sbe::GenerationConfig::new("feature_tour")
        .with_domain_objects(ergo_sbe::DomainVarData::Strings)
        .with_domain_type(
            ergo_sbe::ConversionSelector::named_type("BooleanType"),
            "bool")
        .with_domain_type(
            ergo_sbe::ConversionSelector::semantic_type("UTCTimestamp"),
            "chrono::DateTime<chrono::Utc>")
        .with_conversion(ergo_sbe::ConversionSelector::named_type("Decimal"))
        // Same shape as Decimal, but the app supplies the impl itself — see
        // demo_domain_type_manual_impl in src/lib.rs.
        .with_manual_domain_type(
            ergo_sbe::ConversionSelector::named_type("ManualDecimal"),
            "rust_decimal::Decimal");

    ergo_sbe::generate_to_dir("schemas/feature-tour.xml", config, &generated_dir)?;
}

(The real build.rs — this code is compiled and tested in CI.)

The generated code is included via #[path = "generated/feature_tour.rs"] — no sbe_mod! needed. See Build Patterns.

Selector	Config	Decode API	Encode API	Who writes the impl?
`BooleanType`	`with_domain_type(.., "bool")`	`dec.try_available()?`	`enc.try_available(true)?`	ergo-sbe
`UTCTimestamp`	`with_domain_type(.., chrono)`	`dec.try_timestamp()?`	`enc.try_timestamp(t)?`	ergo-sbe
`Decimal` (Quote)	`with_conversion` only	`dec.price_as::<T>()?`	`enc.price_from(&t)?`	app (generic, any `T`)
`ManualDecimal` (Quote)	`with_manual_domain_type(.., rust_decimal)`	`dec.try_manual_price()?`	`enc.try_manual_price(v)?`	app (one concrete type)

Runnable proof for the Decimal row: demo_conversion_only in src/lib.rs (uses both rust_decimal and a tiny FixedPrice adapter on the same buffer). Runnable proof for the ManualDecimal row: demo_domain_type_manual_impl — same concrete try_manual_price(...)? signature DomainImpl::Generated would give you, but the impl TryFromSbe<ManualDecimal> / TryToSbe<ManualDecimal> above it are a literal copy-paste of the doc comment ergo-sbe put on the generated method (see with_conversion vs with_domain_type).

Quick rule

One fixed app type, ergo-sbe writes the impl → with_domain_type(selector, path)
One fixed app type, you write the impl (custom rounding/validation, or overriding the three built-ins) → with_manual_domain_type(selector, path)
Pluggable / no forced dep → with_conversion
Never call more than one of these for the same selector

Other samples:

Sample	Style
L3 Order Book	`with_domain_type` only
Exchange Example	`with_conversion` only

Feature map → demo

Feature	Demo
Fixed message + `compute_length_with_header()`	`demo_fixed_heartbeat`
Staged `CarEncodedLength`	`demo_car_size_and_encode`
Consuming decoder stages	`demo_car_decode_stages`
Owned DTO	`demo_car_domain_dto`
`AnyMessage`	`demo_any_message`
`bulk_add` (fixed-stride leaf group)	`demo_bulk_add`
Checked decode / wrap / verify	`demo_try_vs_trusted`
Display / Debug	`demo_display_debug`
`with_conversion` only	`demo_conversion_only`
`with_manual_domain_type`	`demo_domain_type_manual_impl`
All of the above	`run_all`

Run

cargo run  --manifest-path samples/sbe-feature-tour/Cargo.toml
cargo test --manifest-path samples/sbe-feature-tour/Cargo.toml

After build, generated source is under src/generated/feature_tour.rs.

ergo-sbe book

SBE Feature Tour

Conversion: three styles in one crate

Quick rule

Feature map → demo

Run