sqlite-parser-nom 1.0.0

SQLite database file parser
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

use nom::error::{ErrorKind, ParseError};
use nom::Err;
use nom::IResult;

/// Big-endian unsigned varint (huffman coding) implementation.
///
/// Most-significant bit is used as a flag if next byte should taken.
/// It is discarded and the rest are concatenated into resulting integer.
pub fn be_u64_varint(i: &[u8]) -> IResult<&[u8], u64> {
    let mut res = 0;
    // to guard from overflow
    let max_slice = &i[0..(i.len().min(5))];
    for (id, &b) in max_slice.iter().enumerate() {
        let b = b as u64;
        res = (res << 7) | (b & 0b0111_1111);

        if b >> 7 == 0 {
            return Ok((&i[id + 1..], res));
        }
    }

    Err(Err::Error(ParseError::from_error_kind(
        i,
        ErrorKind::MapOpt,
    )))
}

#[cfg(test)]
mod tests {
    use crate::varint::be_u64_varint;

    #[test]
    fn parse_1_byte() {
        let varint = [0b0000_1111];
        let (i, res) = be_u64_varint(&varint).unwrap();

        assert!(i.is_empty());
        assert_eq!(res, 0b0000_1111);
    }

    #[test]
    fn parse_2_byte() {
        let varint = [0b1000_1111, 0b0000_1011];
        let (i, res) = be_u64_varint(&varint).unwrap();

        assert!(i.is_empty());
        assert_eq!(res, 0b1111_000_1011);
    }

    #[test]
    fn parse_3_byte() {
        let varint = [0b1000_1111, 0b1000_1101, 0b0000_1011];
        let (i, res) = be_u64_varint(&varint).unwrap();

        assert!(i.is_empty());
        assert_eq!(res, 0b1111_000_1101_000_1011);
    }

    #[test]
    fn parse_4_byte() {
        let varint = [0b1000_1111, 0b1000_0111, 0b1000_1101, 0b0000_1011];
        let (i, res) = be_u64_varint(&varint).unwrap();

        assert!(i.is_empty());
        assert_eq!(res, 0b1111_000_0111_000_1101_000_1011);
    }

    #[test]
    fn parse_5_byte() {
        let varint = [
            0b1000_1111,
            0b1000_1110,
            0b1000_0111,
            0b1000_1101,
            0b0000_1011,
        ];
        let (i, res) = be_u64_varint(&varint).unwrap();

        assert!(i.is_empty());
        assert_eq!(res, 0b1111_000_1110_000_0111_000_1101_000_1011);
    }

    #[test]
    fn ignore_rest() {
        let varint = [
            0b1000_1111,
            0b1000_1110,
            0b1000_0111,
            0b1000_1101,
            0b0000_1011,
            0b0,
        ];
        let (i, _) = be_u64_varint(&varint).unwrap();

        assert_eq!(i.len(), 1);
    }
}