genapi-core

genapi-core builds and evaluates the NodeMap from the device’s GenApi XML. It supports common node kinds and SwissKnife expressions.

Responsibilities

• Parse the genapi-xml intermediate representation into in‑memory nodes.
• Resolve node references and dependencies (incl. Selectors).
• Provide get_*/set_* operations that either access registers or evaluate expressions.

Node kinds (current)

• Integer / Float / Boolean / Enumeration / Command / String / Register
• SwissKnife — expression node referencing other nodes (read‑only). Typical syntax supports arithmetic, comparisons, logical ops, and ternary‑like conditionals.

Selectors

When a feature has selectors (e.g., GainSelector), evaluation temporarily switches the active selector context so reads/writes map to the correct addresses.

Read/write examples (via façade)

Below is a minimal flow using the genicam façade.

use genicam::Client; // façade crate

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    // 1) Connect over GigE Vision to a known IP
    let mut cam = Client::connect("192.168.0.10").await?;

    // 2) Read a numeric feature (backed by register or computed by SwissKnife)
    let exposure: f64 = cam.get_f64("ExposureTime")?; // microseconds
    println!("ExposureTime = {} µs", exposure);

    // 3) Set a feature (register-backed)
    cam.set_f64("ExposureTime", 5000.0)?; // 5 ms

    // 4) Read a computed feature (SwissKnife)
    let derived: f64 = cam.get_f64("LinePeriodUs")?; // example name
    println!("LinePeriodUs (computed) = {}", derived);

    Ok(())
}

Any SwissKnife node is evaluated transparently when you call get_*. If it references other nodes, those nodes are read or computed first.

Caching & invalidation (overview)

• Values are cached within an evaluation pass; writes invalidate dependent caches.
• Selector changes create a new evaluation context so the correct addresses/branches are used.

Errors you may see

• OutOfRange: requested value outside [Min, Max, Inc].
• AccessDenied: node not writable in the current state.
• DependencyMissing: referenced node not found/visible.
• Transport: I/O error while reading/writing registers.

Tips for contributors

• Implement new node kinds behind a common evaluation trait.
• Keep pure computation separate from transport; call into the transport via a narrow interface.
• Add unit tests with synthetic NodeMaps (no device required) plus integration tests that hit real hardware when available.