zhl16

zhl16 is a small #![no_std] Rust crate for core Bühlmann ZHL-16 tissue loading primitives.

The crate currently provides:

• 16-compartment nitrogen and helium tissue loading.
• ZHL-16C tissue constants loaded from data/zhl16c.csv at compile time.
• Gas mixture handling for oxygen, helium, and derived nitrogen fractions.
• Maximum operating pressure and equivalent narcotic pressure helpers.
• Per-compartment safe ambient pressure calculation from a gradient factor.
• Lightweight unit wrappers for pressure, time, pressure rate, and frequency.

This is not a complete dive computer. It does not currently provide dive profile planning, ascent scheduling, decompression stop generation, CNS/OTU tracking, gas switching, validation against dive-computer reference profiles, or safety policy around user input.

Installation

Add the crate to your Cargo.toml:

[dependencies]
zhl16 = "0.1"

Example

use zhl16::{BodyState, GasMixture, Pressure, PressureUnit, Time, TimeUnit};

let mut body = BodyState::new(
    Pressure::new(0.79, PressureUnit::Bar).expect("valid pressure"),
    Pressure::zero(),
);

let trimix_10_20 = GasMixture::new(0.10, 0.20).expect("valid gas mixture");

body.evolve(
    Pressure::new(2.0, PressureUnit::Bar).expect("valid pressure"),
    &trimix_10_20,
    Time::new(60.0, TimeUnit::Seconds).expect("valid time"),
)
.expect("positive time step");

let first_compartment = &body.compartments()[0];
let n2 = first_compartment
    .get_nitrogen_pressure()
    .to(PressureUnit::Bar);
let he = first_compartment
    .get_helium_pressure()
    .to(PressureUnit::Bar);
let safe_pressure = first_compartment
    .safe_ambient_pressure(0.85)
    .expect("valid gradient factor")
    .to(PressureUnit::Bar);

assert!(n2 > 0.79);
assert!(he > 0.0);
let _ = safe_pressure;

Gas Mixtures

GasMixture::new(oxygen_fraction, helium_fraction) stores oxygen and helium fractions. Nitrogen is derived as:

1.0 - oxygen_fraction - helium_fraction

The constructor returns Result<GasMixture, GasMixtureError> if either supplied fraction is not finite, oxygen is zero, either fraction is negative, or oxygen plus helium is greater than 1.0.

use zhl16::{Gas, GasMixture, GasMixtureError, Pressure, PressureUnit};

fn main() -> Result<(), GasMixtureError> {
    let nitrox_32 = GasMixture::new(0.32, 0.0)?;
    assert_eq!(nitrox_32.helium_fraction(), 0.0);
    assert!((nitrox_32.inert_fraction(Gas::Nitrogen) - 0.68).abs() < 1e-12);

    let mod_pressure = nitrox_32
        .max_operational_pressure(
            Pressure::new(1.4, PressureUnit::Bar).expect("valid pressure"),
        )?
        .to(PressureUnit::Bar);

    assert!((mod_pressure - 4.375).abs() < 1e-12);

    Ok(())
}

Tissue Constants

The ZHL-16-C constants live in data/zhl16c.csv. A build script validates that file and generates the Rust TISSUE_CONSTANTS array at compile time.

This keeps the runtime crate no_std; the CSV parsing happens only during compilation.

Units

The crate uses simple typed quantity wrappers:

• Pressure
• Time
• PressureRate
• Frequency

Each quantity stores a base-unit f64 internally and converts through unit enums such as PressureUnit::Bar and TimeUnit::Seconds.

Public quantity constructors return Result<_, QuantityError> and reject NaN values.

Safety

Do not use this crate as the sole basis for real dive planning or life-support decisions. The API is still early and intentionally exposes low-level model primitives rather than a validated decompression algorithm.

License

Licensed under MIT license