blob: 8b85b4939f070fd30a4198a109964381bcb5e4f4 (
plain)
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
|
// crc32.rs
// *************************************************************************
// * Copyright (C) 2017-2018 Daniel Mueller (deso@posteo.net) *
// * *
// * This program is free software: you can redistribute it and/or modify *
// * it under the terms of the GNU General Public License as published by *
// * the Free Software Foundation, either version 3 of the License, or *
// * (at your option) any later version. *
// * *
// * This program is distributed in the hope that it will be useful, *
// * but WITHOUT ANY WARRANTY; without even the implied warranty of *
// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
// * GNU General Public License for more details. *
// * *
// * You should have received a copy of the GNU General Public License *
// * along with this program. If not, see <http://www.gnu.org/licenses/>. *
// *************************************************************************
/// Polynomial used in STM32.
const CRC32_POLYNOMIAL: u32 = 0x04c1_1db7;
fn crc32(mut crc: u32, data: u32) -> u32 {
crc ^= data;
for _ in 0..32 {
if crc & 0x8000_0000 != 0 {
crc = (crc << 1) ^ CRC32_POLYNOMIAL;
} else {
crc <<= 1;
}
}
crc
}
/// Retrieve a u32 slice of the 'data' part.
///
/// Note that the size of the supplied data has to be a multiple of 4
/// bytes.
fn as_slice_u32(data: &[u8]) -> &[u32] {
assert!(data.len() % ::std::mem::size_of::<u32>() == 0);
unsafe {
let ptr = data.as_ptr() as *const u32;
let len = data.len() / ::std::mem::size_of::<u32>();
::std::slice::from_raw_parts(ptr, len)
}
}
/// Calculate the CRC of a byte slice.
pub fn crc(data: &[u8]) -> u32 {
let mut crc = 0xffff_ffff;
let data = as_slice_u32(data);
for byte in data {
crc = crc32(crc, *byte);
}
crc
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_crc32() {
let mut crc = 0;
// The expected values were computed with the original function.
crc = crc32(crc, 0xdeadbeef);
assert_eq!(crc, 0x46dec763);
crc = crc32(crc, 42);
assert_eq!(crc, 0x7e579b45);
}
#[test]
fn test_crc() {
let data = &"thisisatextthatistobecrced..".to_string().into_bytes();
let crc = crc(data);
assert_eq!(crc, 0x469db4ee);
}
}
|
