fixed-dsp 0.2.1

A Rust library for fixed-point digital signal processing (DSP) algorithms.
Documentation 
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use crate::common::tables::{SIN_TABLE_U16, SIN_TABLE_U32};

const Q15_SHIFT: i32 = 16 - 10;
const Q31_SHIFT: i32 = 32 - 10;

/// x is in Q15 format (1.15 fixed-point), representing angles in the range [0, 2π].
pub fn sin_i16(x: i16) -> i16 {
    let mut x_bits = x as u16;
    if x < 0 {
        x_bits = x_bits.wrapping_add(0x8000);
    }

    let x_mapped = x_bits as i32;
    let index = ((x_bits as u32) >> Q15_SHIFT) as usize;
    let fract = (x_mapped - ((index as i32) << Q15_SHIFT)) << 9;

    let a = SIN_TABLE_U16[index] as i16 as i32;
    let b = SIN_TABLE_U16[index + 1] as i16 as i32;

    let mut sin_val = ((0x8000_i32 - fract) * a) >> 16;
    sin_val = ((sin_val << 16) + (fract * b)) >> 16;

    (sin_val << 1) as i16
}

/// x is in Q31 format (1.31 fixed-point), representing angles in the range [0, 2π].
pub fn sin_i32(x: i32) -> i32 {
    let mut x_bits = x as u32;
    if x < 0 {
        x_bits = x_bits.wrapping_add(0x8000_0000);
    }

    let x_mapped = x_bits as i64;
    let index = (x_bits >> Q31_SHIFT) as usize;
    let fract = (x_mapped - ((index as i64) << Q31_SHIFT)) << 9;

    let a = SIN_TABLE_U32[index] as i32 as i64;
    let b = SIN_TABLE_U32[index + 1] as i32 as i64;

    let mut sin_val = ((0x8000_0000_i64 - fract) * a) >> 32;
    sin_val = ((sin_val << 32) + (fract * b)) >> 32;

    (sin_val << 1) as i32
}