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 transforms (FFT/IFFT).

use num_complex::Complex;

use crate::ffi_apis::ffi_api::update_last_error;
use crate::numerical::transforms;

/// Computes the Fast Fourier Transform (FFT) in-place.
///
/// # Arguments
/// * `real` - Pointer to the real parts of the input/output sequence.
/// * `imag` - Pointer to the imaginary parts of the input/output sequence.
/// * `len` - Length of the sequence. Must be a power of two for optimal performance.
///
/// # Returns
/// 0 on success, -1 on error.
///
/// # 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_fft_inplace(
    real: *mut f64,
    imag: *mut f64,
    len: usize,
) -> i32 {
    unsafe {
        if real.is_null() || imag.is_null() {
            update_last_error(
                "Null pointer passed to \
             rssn_num_fft_inplace"
                    .to_string(),
            );

            return -1;
        }

        if !len.is_power_of_two() {
            update_last_error(
                "FFT length must be a \
                 power of two for \
                 in-place operation."
                    .to_string(),
            );

            return -1;
        }

        let mut data: Vec<Complex<f64>> = (0..len)
            .map(|i| Complex::new(*real.add(i), *imag.add(i)))
            .collect();

        transforms::fft_slice(&mut data);

        for (i, c) in data.iter().enumerate() {
            *real.add(i) = c.re;

            *imag.add(i) = c.im;
        }

        0
    }
}

/// Computes the Inverse Fast Fourier Transform (IFFT) in-place.
///
/// # 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_ifft_inplace(
    real: *mut f64,
    imag: *mut f64,
    len: usize,
) -> i32 {
    unsafe {
        if real.is_null() || imag.is_null() {
            update_last_error(
                "Null pointer passed to \
             rssn_num_ifft_inplace"
                    .to_string(),
            );

            return -1;
        }

        if !len.is_power_of_two() {
            update_last_error(
                "IFFT length must be \
                 a power of two for \
                 in-place operation."
                    .to_string(),
            );

            return -1;
        }

        let mut data: Vec<Complex<f64>> = (0..len)
            .map(|i| Complex::new(*real.add(i), *imag.add(i)))
            .collect();

        transforms::ifft_slice(&mut data);

        for (i, c) in data.iter().enumerate() {
            *real.add(i) = c.re;

            *imag.add(i) = c.im;
        }

        0
    }
}