azalea_core/
math.rs

1use std::{
2    f64::consts::PI,
3    ops::{Add, Div, Sub},
4    sync::LazyLock,
5};
6
7pub const EPSILON: f64 = 1.0e-7;
8
9// has to be boxed to avoid a stack overflow on windows when run in debug mode
10pub static SIN: LazyLock<Box<[f32; 65536]>> = LazyLock::new(|| {
11    (0..65536)
12        .map(|i| f64::sin((i as f64) * PI * 2. / 65536.) as f32)
13        .collect::<Box<[f32]>>()
14        .try_into()
15        .unwrap()
16});
17
18/// A sine function that uses a lookup table.
19pub fn sin(x: f32) -> f32 {
20    let x = x * 10430.378;
21    let x = x as i32 as usize & 0xFFFF;
22    SIN[x]
23}
24
25/// A cosine function that uses a lookup table.
26pub fn cos(x: f32) -> f32 {
27    let x = x * 10430.378 + 16384.;
28    let x = x as i32 as usize & 0xFFFF;
29    SIN[x]
30}
31
32pub fn binary_search<
33    T: Ord + PartialOrd + Add<Output = T> + Sub<Output = T> + Div<Output = T> + From<u8> + Copy,
34>(
35    mut min: T,
36    max: T,
37    predicate: impl Fn(T) -> bool,
38) -> T {
39    let mut diff = max - min;
40    while diff > T::from(0) {
41        let diff_mid = diff / T::from(2);
42        let mid = min + diff_mid;
43        if predicate(mid) {
44            diff = diff_mid;
45        } else {
46            min = mid + T::from(1);
47            diff = diff - (diff_mid + T::from(1));
48        }
49    }
50
51    min
52}
53
54pub fn lcm(a: u32, b: u32) -> u64 {
55    let gcd = gcd(a, b);
56    (a as u64) * (b / gcd) as u64
57}
58pub fn gcd(mut a: u32, mut b: u32) -> u32 {
59    while b != 0 {
60        let t = b;
61        b = a % b;
62        a = t;
63    }
64    a
65}
66
67pub fn lerp<T: num_traits::Float>(amount: T, a: T, b: T) -> T {
68    a + amount * (b - a)
69}
70
71pub fn ceil_log2(x: u32) -> u32 {
72    u32::BITS - x.saturating_sub(1).leading_zeros()
73}
74
75pub fn fract(x: f64) -> f64 {
76    let x_int = x as i64 as f64;
77    let floor = if x < x_int { x_int - 1. } else { x_int };
78    x - floor
79}
80
81// these are copied from the java standard library, we don't calculate the
82// consts ourself to make sure it's the same as java
83pub fn to_radians(degrees: f64) -> f64 {
84    degrees * 0.017453292519943295
85}
86pub fn to_degrees(radians: f64) -> f64 {
87    radians * 57.29577951308232
88}
89
90/// Returns either -1, 0, or 1, depending on whether the number is negative,
91/// zero, or positive.
92///
93/// This function exists because f64::signum doesn't check for 0.
94pub fn sign(num: f64) -> f64 {
95    if num == 0. { 0. } else { num.signum() }
96}
97pub fn sign_as_int(num: f64) -> i32 {
98    if num == 0. { 0 } else { num.signum() as i32 }
99}
100
101pub fn ceil_long(x: f64) -> i64 {
102    let x_i64 = x as i64;
103    if x > x_i64 as f64 { x_i64 + 1 } else { x_i64 }
104}
105
106pub fn equal(a: f64, b: f64) -> bool {
107    (b - a).abs() < 1.0e-5
108}
109
110#[cfg(test)]
111mod tests {
112    use super::*;
113
114    #[test]
115    fn test_gcd() {
116        assert_eq!(gcd(0, 0), 0);
117        assert_eq!(gcd(1, 1), 1);
118
119        assert_eq!(gcd(0, 1), 1);
120        assert_eq!(gcd(1, 0), 1);
121
122        assert_eq!(gcd(12, 8), 4);
123        assert_eq!(gcd(8, 12), 4);
124
125        assert_eq!(gcd(12, 9), 3);
126        assert_eq!(gcd(9, 12), 3);
127
128        assert_eq!(gcd(12, 7), 1);
129        assert_eq!(gcd(7, 12), 1);
130    }
131
132    #[test]
133    fn test_sin() {
134        const PI: f32 = std::f32::consts::PI;
135        // check that they're close enough
136        fn assert_sin_eq_enough(number: f32) {
137            let a = sin(number);
138            let b = f32::sin(number);
139            assert!((a - b).abs() < 0.01, "sin({number}) failed, {a} != {b}");
140        }
141        assert_sin_eq_enough(0.0);
142        assert_sin_eq_enough(PI / 2.0);
143        assert_sin_eq_enough(PI);
144        assert_sin_eq_enough(PI * 2.0);
145        assert_sin_eq_enough(PI * 3.0 / 2.0);
146        assert_sin_eq_enough(-PI / 2.0);
147        assert_sin_eq_enough(-PI);
148        assert_sin_eq_enough(-PI * 2.0);
149        assert_sin_eq_enough(-PI * 3.0 / 2.0);
150    }
151}
azalea_core/math.rs

azalea_core/
math.rs
