y-octo 0.0.3

High-performance and thread-safe CRDT implementation compatible with Yjs
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
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138

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

use super::{
    Client, ClientMap, Clock, CrdtRead, CrdtReader, CrdtWrite, CrdtWriter, HASHMAP_SAFE_CAPACITY, HashMapExt, Id,
    JwstCodecResult,
};

#[derive(Default, Debug, PartialEq, Clone)]
pub struct StateVector(ClientMap<Clock>);

impl StateVector {
    pub fn set_max(&mut self, client: Client, clock: Clock) {
        self.entry(client)
            .and_modify(|m_clock| {
                if *m_clock < clock {
                    *m_clock = clock;
                }
            })
            .or_insert(clock);
    }

    pub fn get(&self, client: &Client) -> Clock {
        *self.0.get(client).unwrap_or(&0)
    }

    pub fn contains(&self, id: &Id) -> bool {
        id.clock <= self.get(&id.client)
    }

    pub fn set_min(&mut self, client: Client, clock: Clock) {
        self.entry(client)
            .and_modify(|m_clock| {
                if *m_clock > clock {
                    *m_clock = clock;
                }
            })
            .or_insert(clock);
    }

    pub fn iter(&self) -> impl Iterator<Item = (&Client, &Clock)> {
        self.0.iter()
    }

    pub fn merge_with(&mut self, other: &Self) {
        for (client, clock) in other.iter() {
            self.set_min(*client, *clock);
        }
    }
}

impl Deref for StateVector {
    type Target = ClientMap<Clock>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for StateVector {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl<const N: usize> From<[(Client, Clock); N]> for StateVector {
    fn from(value: [(Client, Clock); N]) -> Self {
        let mut map = ClientMap::with_capacity(N);

        for (client, clock) in value {
            map.insert(client, clock);
        }

        Self(map)
    }
}

impl<R: CrdtReader> CrdtRead<R> for StateVector {
    fn read(decoder: &mut R) -> JwstCodecResult<Self> {
        let len = decoder.read_var_u64()? as usize;

        // See: [HASHMAP_SAFE_CAPACITY]
        let mut map = ClientMap::with_capacity(len.min(HASHMAP_SAFE_CAPACITY));
        for _ in 0..len {
            let client = decoder.read_var_u64()?;
            let clock = decoder.read_var_u64()?;
            map.insert(client, clock);
        }

        map.shrink_to_fit();
        Ok(Self(map))
    }
}

impl<W: CrdtWriter> CrdtWrite<W> for StateVector {
    fn write(&self, encoder: &mut W) -> JwstCodecResult {
        encoder.write_var_u64(self.len() as u64)?;

        for (client, clock) in self.iter() {
            encoder.write_var_u64(*client)?;
            encoder.write_var_u64(*clock)?;
        }

        Ok(())
    }
}

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

    #[test]
    fn test_state_vector_basic() {
        let mut state_vector = StateVector::from([(1, 1), (2, 2), (3, 3)]);
        assert_eq!(state_vector.len(), 3);
        assert_eq!(state_vector.get(&1), 1);

        state_vector.set_min(1, 0);
        assert_eq!(state_vector.get(&1), 0);

        state_vector.set_max(1, 4);
        assert_eq!(state_vector.get(&1), 4);

        // set inexistent client
        state_vector.set_max(4, 1);
        assert_eq!(state_vector.get(&4), 1);

        // same client with larger clock
        assert!(!state_vector.contains(&(1, 5).into()));
    }

    #[test]
    fn test_state_vector_merge() {
        let mut state_vector = StateVector::from([(1, 1), (2, 2), (3, 3)]);
        let other_state_vector = StateVector::from([(1, 5), (2, 6), (3, 7)]);
        state_vector.merge_with(&other_state_vector);
        assert_eq!(state_vector, StateVector::from([(3, 3), (1, 1), (2, 2)]));
    }
}