crc/
crc8.rs

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1use crate::util::crc8;
2use crc_catalog::Algorithm;
3
4mod bytewise;
5mod nolookup;
6mod slice16;
7
8const fn init(algorithm: &Algorithm<u8>, initial: u8) -> u8 {
9    if algorithm.refin {
10        initial.reverse_bits() >> (8u8 - algorithm.width)
11    } else {
12        initial << (8u8 - algorithm.width)
13    }
14}
15
16const fn finalize(algorithm: &Algorithm<u8>, mut crc: u8) -> u8 {
17    if algorithm.refin ^ algorithm.refout {
18        crc = crc.reverse_bits();
19    }
20    if !algorithm.refout {
21        crc >>= 8u8 - algorithm.width;
22    }
23    crc ^ algorithm.xorout
24}
25
26const fn update_nolookup(mut crc: u8, algorithm: &Algorithm<u8>, bytes: &[u8]) -> u8 {
27    let poly = if algorithm.refin {
28        let poly = algorithm.poly.reverse_bits();
29        poly >> (8u8 - algorithm.width)
30    } else {
31        algorithm.poly << (8u8 - algorithm.width)
32    };
33
34    let mut i = 0;
35
36    while i < bytes.len() {
37        crc = crc8(poly, algorithm.refin, crc ^ bytes[i]);
38        i += 1;
39    }
40
41    crc
42}
43
44const fn update_bytewise(mut crc: u8, table: &[u8; 256], bytes: &[u8]) -> u8 {
45    let mut i = 0;
46
47    while i < bytes.len() {
48        crc = table[(crc ^ bytes[i]) as usize];
49        i += 1;
50    }
51
52    crc
53}
54
55const fn update_slice16(mut crc: u8, table: &[[u8; 256]; 16], bytes: &[u8]) -> u8 {
56    let len = bytes.len();
57    let mut i = 0;
58
59    while i + 16 <= len {
60        crc = table[0][bytes[i + 15] as usize]
61            ^ table[1][bytes[i + 14] as usize]
62            ^ table[2][bytes[i + 13] as usize]
63            ^ table[3][bytes[i + 12] as usize]
64            ^ table[4][bytes[i + 11] as usize]
65            ^ table[5][bytes[i + 10] as usize]
66            ^ table[6][bytes[i + 9] as usize]
67            ^ table[7][bytes[i + 8] as usize]
68            ^ table[8][bytes[i + 7] as usize]
69            ^ table[9][bytes[i + 6] as usize]
70            ^ table[10][bytes[i + 5] as usize]
71            ^ table[11][bytes[i + 4] as usize]
72            ^ table[12][bytes[i + 3] as usize]
73            ^ table[13][bytes[i + 2] as usize]
74            ^ table[14][bytes[i + 1] as usize]
75            ^ table[15][(bytes[i] ^ crc) as usize];
76
77        i += 16;
78    }
79
80    while i < len {
81        crc = table[0][(crc ^ bytes[i]) as usize];
82        i += 1;
83    }
84
85    crc
86}
87
88#[cfg(test)]
89mod test {
90    use crate::*;
91    use crc_catalog::{Algorithm, CRC_8_BLUETOOTH};
92
93    /// Test this optimized version against the well known implementation to ensure correctness
94    #[test]
95    fn correctness() {
96        let data: &[&str] = &[
97            "",
98            "1",
99            "1234",
100            "123456789",
101            "0123456789ABCDE",
102            "01234567890ABCDEFGHIJK",
103            "01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK01234567890ABCDEFGHIJK",
104        ];
105
106        pub const CRC_8_BLUETOOTH_NONREFLEX: Algorithm<u8> = Algorithm {
107            width: 8,
108            poly: 0xa7,
109            init: 0x00,
110            refin: false,
111            refout: true,
112            xorout: 0x00,
113            check: 0x26,
114            residue: 0x00,
115        };
116
117        let algs_to_test = [&CRC_8_BLUETOOTH, &CRC_8_BLUETOOTH_NONREFLEX];
118
119        for alg in algs_to_test {
120            for data in data {
121                let crc_slice16 = Crc::<u8, Table<16>>::new(alg);
122                let crc_nolookup = Crc::<u8, NoTable>::new(alg);
123                let expected = Crc::<u8, Table<1>>::new(alg).checksum(data.as_bytes());
124
125                // Check that doing all at once works as expected
126                assert_eq!(crc_slice16.checksum(data.as_bytes()), expected);
127                assert_eq!(crc_nolookup.checksum(data.as_bytes()), expected);
128
129                let mut digest = crc_slice16.digest();
130                digest.update(data.as_bytes());
131                assert_eq!(digest.finalize(), expected);
132
133                let mut digest = crc_nolookup.digest();
134                digest.update(data.as_bytes());
135                assert_eq!(digest.finalize(), expected);
136
137                // Check that we didn't break updating from multiple sources
138                if data.len() > 2 {
139                    let data = data.as_bytes();
140                    let data1 = &data[..data.len() / 2];
141                    let data2 = &data[data.len() / 2..];
142                    let mut digest = crc_slice16.digest();
143                    digest.update(data1);
144                    digest.update(data2);
145                    assert_eq!(digest.finalize(), expected);
146                    let mut digest = crc_nolookup.digest();
147                    digest.update(data1);
148                    digest.update(data2);
149                    assert_eq!(digest.finalize(), expected);
150                }
151            }
152        }
153    }
154}
crc/crc8.rs

crc/
crc8.rs
