GatoMQTT 0.2.0

no_std, no_alloc MQTT 3.1.1 broker library for embedded Rust. Bounded session registry, retained messages, QoS 1, transport-agnostic (plain TCP or TLS via TlsSession trait).
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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156

use embassy_time::Instant;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TokenBucket {
    tokens: u8,
    capacity: u8,
    rate_per_sec: u8,
    last_refill: Instant,
    violations: u8,
}

impl TokenBucket {
    pub const fn new(capacity: u8, rate_per_sec: u8) -> Self {
        Self {
            tokens: capacity,
            capacity,
            rate_per_sec,
            last_refill: Instant::from_ticks(0),
            violations: 0,
        }
    }

    pub fn try_consume(&mut self, now: Instant) -> bool {
        if let Some(elapsed) = now.checked_duration_since(self.last_refill) {
            let elapsed_secs = elapsed.as_secs();
            if elapsed_secs > 0 {
                let refill = (elapsed_secs.saturating_mul(self.rate_per_sec as u64))
                    .min(u8::MAX as u64) as u8;
                self.tokens = self.tokens.saturating_add(refill).min(self.capacity);
                self.last_refill = now;
            }
        }

        if self.tokens > 0 {
            self.tokens -= 1;
            self.violations = 0;
            true
        } else {
            self.violations = self.violations.saturating_add(1);
            false
        }
    }

    pub fn reset_violations(&mut self) {
        self.violations = 0;
    }

    pub const fn violations(&self) -> u8 {
        self.violations
    }
}

impl Default for TokenBucket {
    fn default() -> Self {
        Self::new(0, 0)
    }
}

#[cfg(test)]
mod tests {
    use super::TokenBucket;
    use embassy_time::Instant;

    #[test]
    fn starts_with_full_capacity_and_allows_initial_burst() {
        let mut bucket = TokenBucket::new(20, 10);
        let t0 = Instant::from_secs(0);

        for _ in 0..20 {
            assert!(bucket.try_consume(t0));
        }

        assert_eq!(bucket.tokens, 0);
        assert_eq!(bucket.violations(), 0);
    }

    #[test]
    fn twenty_first_consume_fails_and_increments_violations() {
        let mut bucket = TokenBucket::new(20, 10);
        let t0 = Instant::from_secs(0);

        for _ in 0..20 {
            assert!(bucket.try_consume(t0));
        }

        assert!(!bucket.try_consume(t0));
        assert_eq!(bucket.violations(), 1);
    }

    #[test]
    fn one_second_refills_rate_tokens() {
        let mut bucket = TokenBucket::new(20, 10);
        let t0 = Instant::from_secs(0);

        for _ in 0..20 {
            assert!(bucket.try_consume(t0));
        }

        assert!(bucket.try_consume(Instant::from_secs(1)));
        assert_eq!(bucket.tokens, 9);
        assert_eq!(bucket.violations(), 0);
    }

    #[test]
    fn refill_does_not_exceed_capacity() {
        let mut bucket = TokenBucket::new(20, 10);
        let t0 = Instant::from_secs(0);

        for _ in 0..5 {
            assert!(bucket.try_consume(t0));
        }

        assert!(bucket.try_consume(Instant::from_secs(10)));
        assert_eq!(bucket.tokens, 19);
    }

    #[test]
    fn fifty_consecutive_violations_are_counted() {
        let mut bucket = TokenBucket::new(1, 0);
        let t0 = Instant::from_secs(0);

        assert!(bucket.try_consume(t0));
        for _ in 0..50 {
            assert!(!bucket.try_consume(t0));
        }

        assert_eq!(bucket.violations(), 50);
    }

    #[test]
    fn successful_consume_resets_violations() {
        let mut bucket = TokenBucket::new(1, 1);
        let t0 = Instant::from_secs(0);

        assert!(bucket.try_consume(t0));
        assert!(!bucket.try_consume(t0));
        assert!(!bucket.try_consume(t0));
        assert_eq!(bucket.violations(), 2);

        assert!(bucket.try_consume(Instant::from_secs(1)));
        assert_eq!(bucket.violations(), 0);
    }

    #[test]
    fn reset_violations_clears_counter() {
        let mut bucket = TokenBucket::new(1, 0);
        let t0 = Instant::from_secs(0);

        assert!(bucket.try_consume(t0));
        assert!(!bucket.try_consume(t0));
        assert_eq!(bucket.violations(), 1);

        bucket.reset_violations();
        assert_eq!(bucket.violations(), 0);
    }
}