rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
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//! Bincode-based FFI API for physics RKM (Runge-Kutta Methods) functions.

use serde::Deserialize;
use serde::Serialize;

use crate::ffi_apis::common::BincodeBuffer;
use crate::ffi_apis::common::from_bincode_buffer;
use crate::ffi_apis::common::to_bincode_buffer;
use crate::ffi_apis::ffi_api::FfiResult;
use crate::physics::physics_rkm::DormandPrince54;
use crate::physics::physics_rkm::{
    self,
};

#[derive(Deserialize)]
struct LorenzInput {
    sigma: f64,
    rho: f64,
    beta: f64,
    y0: Vec<f64>,
    t_span: (f64, f64),
    dt_initial: f64,
    tol: (f64, f64),
}

#[derive(Serialize)]
struct OdeResult {
    time: Vec<f64>,
    states: Vec<Vec<f64>>,
}

/// Solves the Lorenz system using adaptive Dormand-Prince RK5(4) method via bincode serialization.
///
/// The Lorenz system is a chaotic dynamical system defined by:
/// dx/dt = σ(y - x), dy/dt = x(ρ - z) - y, dz/dt = xy - βz.
///
/// # Arguments
///
/// * `buffer` - A bincode-encoded buffer containing `LorenzInput` with:
///   - `sigma`: Prandtl number σ
///   - `rho`: Rayleigh number ρ
///   - `beta`: Geometric parameter β
///   - `y0`: Initial state [x₀, y₀, z₀]
///   - `t_span`: Time interval (`t_start`, `t_end`)
///   - `dt_initial`: Initial time step size
///   - `tol`: Error tolerances (absolute, relative)
///
/// # Returns
///
/// A bincode-encoded buffer containing `FfiResult<OdeResult, String>` with either:
/// - `ok`: Object containing `time` and `states` arrays
/// - `err`: Error message if computation failed
///
/// # Safety
///
/// This function is unsafe because it receives a raw bincode buffer that must be
/// valid and properly encoded.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_physics_rkm_lorenz_bincode(buffer: BincodeBuffer) -> BincodeBuffer {
    let input: LorenzInput = match from_bincode_buffer(&buffer) {
        | Some(i) => i,
        | None => {
            return to_bincode_buffer(&FfiResult::<OdeResult, String>::err(
                "Invalid Bincode".to_string(),
            ));
        },
    };

    let system = physics_rkm::LorenzSystem {
        sigma: input.sigma,
        rho: input.rho,
        beta: input.beta,
    };

    let solver = DormandPrince54::new();

    let results = solver.solve(
        &system,
        &input.y0,
        input.t_span,
        input.dt_initial,
        input.tol,
    );

    let mut time = Vec::with_capacity(results.len());

    let mut states = Vec::with_capacity(results.len());

    for (t, y) in results {
        time.push(t);

        states.push(y);
    }

    to_bincode_buffer(&FfiResult::<OdeResult, String>::ok(OdeResult {
        time,
        states,
    }))
}