rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
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//! JSON-based FFI API for physics CNM functions.

use std::os::raw::c_char;

use serde::Deserialize;

use crate::ffi_apis::common::from_json_string;
use crate::ffi_apis::common::to_c_string;
use crate::ffi_apis::ffi_api::FfiResult;
use crate::physics::physics_cnm::HeatEquationSolverConfig;
use crate::physics::physics_cnm::{
    self,
};

#[derive(Deserialize)]
struct Heat2DInput {
    initial_condition: Vec<f64>,
    config: HeatEquationSolverConfig,
}

/// Solves the 2D heat equation using Crank-Nicolson ADI method via JSON serialization.
///
/// The heat equation ∂u/∂t = α∇²u is solved using the Crank-Nicolson Alternating
/// Direction Implicit (ADI) method, which is unconditionally stable and second-order
/// accurate in both space and time.
///
/// # Arguments
///
/// * `input` - A JSON string pointer containing:
///   - `initial_condition`: Initial temperature distribution (flattened 2D grid)
///   - `config`: Solver configuration (grid size, time step, thermal diffusivity, etc.)
///
/// # Returns
///
/// A C string pointer containing JSON-encoded `FfiResult<Vec<f64>, String>` with
/// the final temperature distribution after time evolution.
///
/// # Safety
///
/// This function is unsafe because it receives a raw C string pointer that must be
/// valid, null-terminated UTF-8. The caller must free the returned pointer.
///
/// # 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.
///
/// # Panics
///
/// This function may panic if the FFI input is malformed, null where not expected,
/// or if internal state synchronization fails (e.g., poisoned locks).
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_physics_cnm_solve_heat_2d_json(input: *const c_char) -> *mut c_char {
    let input: Heat2DInput = match from_json_string(input) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<Vec<f64>, String>::err(
                    "Invalid JSON".to_string(),
                ))
                .unwrap(),
            );
        },
    };

    let res = physics_cnm::solve_heat_equation_2d_cn_adi(&input.initial_condition, &input.config);

    to_c_string(serde_json::to_string(&FfiResult::<Vec<f64>, String>::ok(res)).unwrap())
}