1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99

use math::{Point2, Point3, Point4};
use noise_fns::NoiseFn;
use std::cell::{Cell, RefCell};

/// Noise function that caches the last output value generated by the source
/// function.
///
/// If the input coordinates passed to `Cache::get` are equal to the previous
/// call, the function returns the cached result of the previous call to
/// `Source::get`. Otherwise, `Source::get` is called with the new coordinates,
/// overwriting the cache with the result, and returning the result to the
/// caller.
///
/// Caching a noise function is useful if it is used as a source function for
/// multiple noise functions. If a source function is not cached, the source
/// function will redundantly calculate the same output value once for each
/// noise function in which it is included.
#[derive(Clone, Debug)]
pub struct Cache<'a, Source: 'a> {
    /// Outputs the value to be cached.
    pub source: &'a Source,

    value: Cell<Option<f64>>,

    point: RefCell<Vec<f64>>,
}

impl<'a, Source> Cache<'a, Source> {
    pub fn new(source: &'a Source) -> Self {
        Cache {
            source,
            value: Cell::new(None),
            point: RefCell::new(Vec::new()),
        }
    }
}

impl<'a, Source> NoiseFn<Point2<f64>> for Cache<'a, Source>
where
    Source: NoiseFn<Point2<f64>>,
{
    fn get(&self, point: Point2<f64>) -> f64 {
        match self.value.get() {
            Some(value) if *self.point.borrow() == point => value,
            Some(_) | None => {
                let value = self.source.get(point);
                self.value.set(Some(value));

                let mut cached_point = self.point.borrow_mut();
                cached_point.clear();
                cached_point.extend_from_slice(&point);

                value
            },
        }
    }
}

impl<'a, Source> NoiseFn<Point3<f64>> for Cache<'a, Source>
where
    Source: NoiseFn<Point3<f64>>,
{
    fn get(&self, point: Point3<f64>) -> f64 {
        match self.value.get() {
            Some(value) if *self.point.borrow() == point => value,
            Some(_) | None => {
                let value = self.source.get(point);
                self.value.set(Some(value));

                let mut cached_point = self.point.borrow_mut();
                cached_point.clear();
                cached_point.extend_from_slice(&point);

                value
            },
        }
    }
}

impl<'a, Source> NoiseFn<Point4<f64>> for Cache<'a, Source>
where
    Source: NoiseFn<Point4<f64>>,
{
    fn get(&self, point: Point4<f64>) -> f64 {
        match self.value.get() {
            Some(value) if *self.point.borrow() == point => value,
            Some(_) | None => {
                let value = self.source.get(point);
                self.value.set(Some(value));

                let mut cached_point = self.point.borrow_mut();
                cached_point.clear();
                cached_point.extend_from_slice(&point);

                value
            },
        }
    }
}