microspectrogram 0.1.0

A simple `no_std` library for computing spectrograms.
Documentation 
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use microfft::{real::*, Complex32};

macro_rules! impl_ff {
    ( $name:ident, $n:tt, $fn:ident) => {
        #[allow(dead_code)]
        pub fn $name<const N: usize>(arr: &mut [f32; $n], result: &mut [Complex32; 1 + N / 2]) {
            let out = $fn(arr);
            result[0] = Complex32::new(out[0].re, 0.0);
            (1..($n / 2)).for_each(|i| {
                result[i] = out[i];
            });
            result[$n / 2] = Complex32::new(out[0].im, 0.0);

            // ((1 + $n / 2)..$n).for_each(|i| {
            //     result[i] = Complex32::new(out[$n - i].re, -out[$n - i].im);
            // });
        }
    };
}

impl_ff!(fft_4, 4, rfft_4);
impl_ff!(fft_8, 8, rfft_8);
impl_ff!(fft_16, 16, rfft_16);
impl_ff!(fft_32, 32, rfft_32);
impl_ff!(fft_64, 64, rfft_64);
impl_ff!(fft_128, 128, rfft_128);
impl_ff!(fft_256, 256, rfft_256);

pub unsafe fn fft<const N: usize>(arr: &mut [f32], result: &mut [Complex32; 1 + N / 2]) {
    match N {
        4 => {
            let arr = arr.as_ptr() as *mut [f32; 4];
            fft_4(&mut unsafe { *arr }, result)
        }
        8 => {
            let arr = arr.as_ptr() as *mut [f32; 8];
            fft_8(&mut unsafe { *arr }, result)
        }
        16 => {
            let arr = arr.as_ptr() as *mut [f32; 16];
            fft_16(&mut unsafe { *arr }, result)
        }
        32 => {
            let arr = arr.as_ptr() as *mut [f32; 32];
            fft_32(&mut unsafe { *arr }, result)
        }
        64 => {
            let arr = arr.as_ptr() as *mut [f32; 64];
            fft_64(&mut unsafe { *arr }, result)
        }
        128 => {
            let arr = arr.as_ptr() as *mut [f32; 128];
            fft_128(&mut unsafe { *arr }, result)
        }
        256 => {
            let arr = arr.as_ptr() as *mut [f32; 256];
            fft_256(&mut unsafe { *arr }, result)
        }
        _ => unreachable!(),
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    #[allow(clippy::excessive_precision)]
    fn test_fft_4() {
        let mut input = [1.0f32, 2.19328005, 4.81047738, 10.55072407];
        let expected_scipy = [
            Complex32::new(18.55448151, -0.),
            Complex32::new(-3.8104773, 8.35744402),
            Complex32::new(-6.933527, -0.),
            // Complex32::new(-3.8104773, -8.35744402),
        ];
        let mut out: [Complex32; 3] = Default::default();
        fft_4::<4>(&mut input, &mut out);
        assert_eq!(out, expected_scipy);
    }

    #[test]
    #[allow(clippy::excessive_precision)]
    fn test_fft_8() {
        let mut input = [
            1.0f32,
            2.19328005,
            4.81047738,
            10.55072407,
            23.14069263,
            50.75401951,
            111.31777849,
            244.15106285,
        ];
        let expected_scipy = [
            Complex32::new(447.91803499, -0.),
            Complex32::new(108.70207, 306.02533),
            Complex32::new(-91.98756324, 201.75448737),
            Complex32::new(-152.9834481, 93.0107107),
            Complex32::new(-167.38013, -0.),
            // Complex32::new(-152.9834481, -93.0107107),
            // Complex32::new(-91.98756324, -201.75448737),
            // Complex32::new(108.70207, -306.02533),
        ];
        let mut out: [Complex32; 5] = Default::default();
        fft_8::<8>(&mut input, &mut out);
        assert_eq!(out, expected_scipy);
    }

    #[test]
    #[allow(clippy::excessive_precision)]
    fn test_fft_16() {
        let mut input = [
            0.65600173, 0.63951888, 0.62348176, 0.60798841, 0.59066761, 0.57568833, 0.56063477,
            0.54556932, 0.53043256, 0.51324547, 0.4984534, 0.48411299, 0.46861073, 0.45568773,
            0.4428301, 0.42829952,
        ];
        let expected_scipy = [
            Complex32::new(8.62122329, -0.),
            Complex32::new(0.14047813, -0.61227777),
            Complex32::new(0.12938741, -0.2879077),
            Complex32::new(0.12032691, -0.18132925),
            Complex32::new(0.12031269, -0.11817002),
            Complex32::new(0.120595664, -0.082025215),
            Complex32::new(0.12492439, -0.050967306),
            Complex32::new(0.12087595, -0.02474621),
            Complex32::new(0.1210022, -0.),
            // Complex32::new(0.12087595, 0.02474621),
            // Complex32::new(0.12492439, 0.050967306),
            // Complex32::new(0.120595664, 0.082025215),
            // Complex32::new(0.12031269, 0.11817002),
            // Complex32::new(0.12032691, 0.18132925),
            // Complex32::new(0.12938741, 0.2879077),
            // Complex32::new(0.14047813, 0.61227777),
        ];
        let mut out: [Complex32; 9] = Default::default();
        fft_16::<16>(&mut input, &mut out);
        assert_eq!(out, expected_scipy);
    }
}