depends 0.11.0

Ergonomic, performant, incremental computation between arbitrary types
Documentation 
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
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118

use std::{
    hash::Hasher,
    ops::{Deref, DerefMut},
};

use super::NodeHash;
use crate::{
    error::EarlyExit,
    execution::{Clean, HashValue, Named},
    UpdateDerived,
};

/// A wrapper for some value `T`, tracking some context around the value's
/// computation state.
#[derive(Debug)]
pub struct NodeState<T> {
    /// A value representing the unique state of the value (i.e. the Hash).
    node_hash: NodeHash,
    /// The value being wrapped.
    value: T,
}

impl<T: HashValue> NodeState<T> {
    pub fn new(value: T) -> Self {
        Self {
            node_hash: NodeHash::default(),
            value,
        }
    }

    pub fn node_hash(&self) -> NodeHash {
        self.node_hash
    }

    pub fn node_hash_mut(&mut self) -> &mut NodeHash {
        &mut self.node_hash
    }

    /// Update the stored hash value of the value.
    pub fn update_node_hash(&mut self, hasher: &mut impl Hasher) {
        self.node_hash = self.value.hash_value(hasher)
    }

    pub fn value(&self) -> &T {
        &self.value
    }

    pub fn value_mut(&mut self) -> &mut T {
        &mut self.value
    }
}

impl<T: HashValue> HashValue for NodeState<T> {
    fn hash_value(&self, _: &mut impl Hasher) -> NodeHash {
        self.node_hash
    }
}

impl<T: Named> Named for NodeState<T> {
    fn name() -> &'static str {
        T::name()
    }
}

impl<T: Clean> Clean for NodeState<T> {
    fn clean(&mut self) {
        self.value.clean()
    }
}

impl<T> Deref for NodeState<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.value
    }
}

impl<T> DerefMut for NodeState<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.value
    }
}

impl<T, D, F> UpdateDerived<D, F> for NodeState<T>
where
    T: UpdateDerived<D, F>,
{
    fn update(&mut self, value: D) -> Result<(), EarlyExit> {
        self.value.update(value)
    }
}

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

    #[test]
    fn test_node_state() {
        let mut state = NodeState::new(123_i32);
        assert_eq!(
            "NodeState { node_hash: NotHashed, value: 123 }",
            format!("{:?}", state)
        );
        assert_eq!(<NodeState<i32> as Named>::name(), "i32");
        let hasher = &mut std::collections::hash_map::DefaultHasher::new();
        state.update_node_hash(hasher);
        assert_eq!(state.node_hash(), NodeHash::Hashed(14370432302296844161));
        assert_eq!(
            state.node_hash_mut(),
            &mut NodeHash::Hashed(14370432302296844161)
        );
        state.clean();
        assert_eq!(state.value(), &123);
        *state.value_mut() = 456;
        assert_eq!(state.value(), &456);
    }
}