rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
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//! Handle-based FFI API for numerical interpolation.

use std::ptr;
use std::sync::Arc;

use crate::ffi_apis::ffi_api::update_last_error;
use crate::numerical::interpolate;
use crate::numerical::polynomial::Polynomial;

/// Opaque type for cubic spline closure.
pub type CubicSplineHandle = Arc<dyn Fn(f64) -> f64>;

/// Computes Lagrange interpolation and returns a Polynomial 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.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_lagrange_interpolation(
    x_coords: *const f64,
    y_coords: *const f64,
    len: usize,
) -> *mut Polynomial {
    unsafe {
        if x_coords.is_null() || y_coords.is_null() {
            update_last_error("Null pointer passed to rssn_num_lagrange_interpolation".to_string());

            return ptr::null_mut();
        }

        let x_slice = { std::slice::from_raw_parts(x_coords, len) };

        let y_slice = { std::slice::from_raw_parts(y_coords, len) };

        let points: Vec<(f64, f64)> = x_slice
            .iter()
            .zip(y_slice.iter())
            .map(|(&x, &y)| (x, y))
            .collect();

        match interpolate::lagrange_interpolation(&points) {
            | Ok(poly) => Box::into_raw(Box::new(poly)),
            | Err(e) => {
                update_last_error(e);

                ptr::null_mut()
            },
        }
    }
}

/// Creates a cubic spline interpolator handle.
///
/// # 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_num_cubic_spline_interpolation(
    x_coords: *const f64,
    y_coords: *const f64,
    len: usize,
) -> *mut CubicSplineHandle {
    unsafe {
        if x_coords.is_null() || y_coords.is_null() {
            update_last_error(
                "Null pointer passed to rssn_num_cubic_spline_interpolation".to_string(),
            );

            return ptr::null_mut();
        }

        let x_slice = { std::slice::from_raw_parts(x_coords, len) };

        let y_slice = { std::slice::from_raw_parts(y_coords, len) };

        let points: Vec<(f64, f64)> = x_slice
            .iter()
            .zip(y_slice.iter())
            .map(|(&x, &y)| (x, y))
            .collect();

        match interpolate::cubic_spline_interpolation(&points) {
            | Ok(spline) => Box::into_raw(Box::new(spline)),
            | Err(e) => {
                update_last_error(e);

                ptr::null_mut()
            },
        }
    }
}

/// Evaluates a cubic spline at a given x coordinate.
///
/// # 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_num_cubic_spline_evaluate(
    handle: *const CubicSplineHandle,
    x: f64,
) -> f64 {
    unsafe {
        if handle.is_null() {
            update_last_error("Null pointer passed to rssn_num_cubic_spline_evaluate".to_string());

            return f64::NAN;
        }

        let spline = { &*handle };

        spline(x)
    }
}

/// Frees a cubic spline handle.
///
/// # 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_num_cubic_spline_free(handle: *mut CubicSplineHandle) {
    if !handle.is_null() {
        unsafe {
            let _ = Box::from_raw(handle);
        }
    }
}

/// Evaluates a Bézier curve at parameter t.
/// `control_points` is a flattened array of size `n_points` * dim.
///
/// # 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_num_bezier_curve(
    control_points: *const f64,
    n_points: usize,
    dim: usize,
    t: f64,
    out_point: *mut f64,
) -> i32 {
    if control_points.is_null() || out_point.is_null() {
        return -1;
    }

    let data = unsafe { std::slice::from_raw_parts(control_points, n_points * dim) };

    let mut cp_vecs = Vec::with_capacity(n_points);

    for i in 0..n_points {
        cp_vecs.push(data[i * dim..(i + 1) * dim].to_vec());
    }

    let result = interpolate::bezier_curve(&cp_vecs, t);

    unsafe {
        std::ptr::copy_nonoverlapping(result.as_ptr(), out_point, dim);
    }

    0
}

/// Evaluates a B-spline curve at parameter t.
///
/// # 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_num_b_spline(
    control_points: *const f64,
    n_points: usize,
    dim: usize,
    degree: usize,
    knots: *const f64,
    n_knots: usize,
    t: f64,
    out_point: *mut f64,
) -> i32 {
    if control_points.is_null() || knots.is_null() || out_point.is_null() {
        return -1;
    }

    let data = unsafe { std::slice::from_raw_parts(control_points, n_points * dim) };

    let mut cp_vecs = Vec::with_capacity(n_points);

    for i in 0..n_points {
        cp_vecs.push(data[i * dim..(i + 1) * dim].to_vec());
    }

    let knot_slice = unsafe { std::slice::from_raw_parts(knots, n_knots) };

    match interpolate::b_spline(&cp_vecs, degree, knot_slice, t) {
        | Some(result) => {
            unsafe {
                std::ptr::copy_nonoverlapping(result.as_ptr(), out_point, dim);
            }

            0
        },
        | None => -1,
    }
}