nada 0.2.2

Compression-focused encoding for zero-heavy solidity calldata and bytecode
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

pub(crate) struct Decoder {
    out: Vec<u8>,
    waiting_follow_up: bool,
}

impl Decoder {
    pub fn new() -> Self {
        Self {
            out: Vec::new(),
            waiting_follow_up: false,
        }
    }

    pub fn feed(&mut self, input: u8) -> Result<(), DecodeError> {
        if self.waiting_follow_up {
            match input {
                0x00 => {
                    return Err(DecodeError::ReservedSequence);
                }
                0x01 => {
                    self.waiting_follow_up = false;
                    self.out.push(0xFF);
                }
                0x02 => {
                    self.waiting_follow_up = false;
                    self.out.push(0xFF);
                    self.out.push(0xFF);
                }
                _ => {
                    self.waiting_follow_up = false;
                    for _ in 0..input {
                        self.out.push(0x00);
                    }
                }
            }
        } else {
            match input {
                0xFF => {
                    self.waiting_follow_up = true;
                }
                _ => {
                    self.out.push(input);
                }
            }
        }

        Ok(())
    }

    pub fn output(self) -> Result<Vec<u8>, DecodeError> {
        if self.waiting_follow_up {
            return Err(DecodeError::UnexpectedEOF);
        }
        Ok(self.out)
    }

    pub fn len(&self) -> usize {
        self.out.len()
    }
}

#[derive(Debug, Clone, Copy, PartialEq)]
pub enum DecodeError {
    UnexpectedEOF,    // Reached the end of input unexpectedly
    ReservedSequence, // Encountered a reserved sequence, e.g., 0xFF followed by 0x00
    LimitExceeded,    // Output exceeds the specified limit
}

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

    #[test]
    fn test_decoder() {
        let mut decoder = Decoder::new();
        let input = vec![0xFF, 0x01, 0xFF, 0x02, 0x03];
        for byte in input {
            decoder.feed(byte).unwrap();
        }
        let output = decoder.output().unwrap();
        assert_eq!(output, vec![0xFF, 0xFF, 0xFF, 0x03]);
    }

    #[test]
    fn test_decoder_empty() {
        let mut decoder = Decoder::new();
        let input: Vec<u8> = vec![];
        for byte in input {
            decoder.feed(byte).unwrap();
        }
        assert_eq!(decoder.output().unwrap(), vec![]);
    }

    #[test]
    fn test_decoder_no_zeros() {
        let mut decoder = Decoder::new();
        let input = vec![1, 2, 3, 4, 5];
        for byte in input {
            decoder.feed(byte).unwrap();
        }
        assert_eq!(decoder.output().unwrap(), vec![1, 2, 3, 4, 5]);
    }

    #[test]
    fn test_decoder_only_zeros() {
        let mut decoder = Decoder::new();
        let input = vec![0xFF, 0x04];
        for byte in input {
            decoder.feed(byte).unwrap();
        }
        assert_eq!(decoder.output().unwrap(), vec![0, 0, 0, 0]);
    }

    #[test]
    fn test_decoder_only_ff() {
        let mut decoder = Decoder::new();
        let input = vec![0xFF, 0x02, 0xFF, 0x01];
        for byte in input {
            decoder.feed(byte).unwrap();
        }
        assert_eq!(decoder.output().unwrap(), vec![0xFF, 0xFF, 0xFF]);
    }

    #[test]
    fn test_decoder_mixed() {
        let mut decoder = Decoder::new();
        let input = vec![0xFF, 0x01, 0xFF, 0x05, 2, 0xFF, 1, 0x03];
        for byte in input {
            decoder.feed(byte).unwrap();
        }
        assert_eq!(
            decoder.output().unwrap(),
            vec![0xFF, 0, 0, 0, 0, 0, 2, 0xFF, 0x03]
        );
    }

    #[test]
    fn test_decoder_unexpected_eof() {
        let mut decoder = Decoder::new();
        let input = vec![1, 2, 3, 4, 5, 0xFF];
        for byte in input {
            decoder.feed(byte).unwrap();
        }
        assert_eq!(decoder.output(), Err(DecodeError::UnexpectedEOF));
    }

    #[test]
    fn test_decoder_reserved_sequence() {
        let mut decoder = Decoder::new();
        decoder.feed(0xFF).unwrap();
        assert_eq!(decoder.feed(0x00), Err(DecodeError::ReservedSequence));
    }
}