rustyfit 0.4.1

This project hosts the Rust implementation for The Flexible and Interoperable Data Transfer (FIT) Protocol
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

#[derive(Default)]
pub(super) struct Lru {
    items: Vec<Vec<u8>>,
    bucket: Vec<usize>,
}

impl Lru {
    pub(super) fn new(n: usize) -> Self {
        Self {
            items: vec![Vec::new(); n],
            bucket: Vec::with_capacity(n),
        }
    }

    pub(super) fn reset(&mut self) {
        self.bucket.clear();
    }

    pub(super) fn put(&mut self, item: &[u8]) -> (u8, bool) {
        if let Some(bucket_index) = self.bucket_index(item) {
            return (self.mark_as_recently_used(bucket_index), false);
        }
        if self.bucket.len() != self.items.len() {
            return (self.store(item), true);
        }
        (self.replace_least_recently_used(item), true)
    }

    fn store(&mut self, item: &[u8]) -> u8 {
        let item_index = self.bucket.len();
        self.items[item_index].clear();
        self.items[item_index].extend_from_slice(item);
        self.bucket.push(item_index);
        item_index as u8
    }

    fn mark_as_recently_used(&mut self, bucket_index: usize) -> u8 {
        let item_index = self.bucket[bucket_index];
        self.bucket.remove(bucket_index);
        self.bucket.push(item_index);
        item_index as u8
    }

    fn replace_least_recently_used(&mut self, item: &[u8]) -> u8 {
        let item_index = self.bucket[0];
        self.bucket.remove(0);
        self.bucket.push(item_index);
        self.items[item_index].clear();
        self.items[item_index].extend_from_slice(item);
        item_index as u8
    }

    fn bucket_index(&self, item: &[u8]) -> Option<usize> {
        for i in (0..self.bucket.len()).rev() {
            let cur = self.bucket[i];
            if self.items[cur] == item {
                return Some(i);
            }
        }
        None
    }
}

#[cfg(test)]
#[test]
fn test_lru() {
    const SIZE: usize = 16;
    let mut lru = Lru::new(SIZE);

    assert_eq!(lru.bucket.len(), 0);
    assert_eq!(lru.bucket.capacity(), SIZE);
    assert_eq!(lru.items.len(), SIZE);
    assert_eq!(lru.items.capacity(), SIZE);

    // place (size * 10) different items, the lru will be shifted in roundroubin order.
    for i in 0..SIZE * 10 {
        let mut b = vec![0u8; i + 1];
        b[0] = i as u8;
        let (local_mesg_num, is_new) = lru.put(&b);
        assert_eq!(local_mesg_num, (i % SIZE) as u8);
        assert!(is_new);
    }

    // put same items should shift the lru bucket
    for i in 0..SIZE {
        let item = lru.items[i].clone();
        let (local_mesg_num, _) = lru.put(&item);
        assert_eq!(local_mesg_num, i as u8);
        assert_eq!(lru.bucket[SIZE - 1], i);
    }

    // check index exist
    assert_eq!(lru.bucket_index(&lru.items[lru.bucket[1]]), Some(1));

    // check index not exist
    assert!(lru.bucket_index(&[255, 255]).is_none());

    lru.reset();
    assert_eq!(lru.bucket.len(), 0);
    assert_eq!(lru.items.len(), SIZE);
}