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// https://github.com/d-e-s-o/nitrocli/blob/ac29709a644682c61a5a28d2a23f8887174fcc31/nitrocli/src/crc32.rs
//
// *************************************************************************
// * Copyright (C) 2017 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 = 0x04c11db7;
fn crc32(mut crc: u32, data: u32) -> u32 {
crc = crc ^ data;
for _ in 0..32 {
if crc & 0x80000000 != 0 {
crc = (crc << 1) ^ CRC32_POLYNOMIAL;
} else {
crc = crc << 1;
}
}
return 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>();
return ::std::slice::from_raw_parts(ptr, len);
}
}
/// Calculate the CRC of a byte slice.
pub fn crc(data: &[u8]) -> u32 {
let mut crc = 0xffffffff;
for value in as_slice_u32(data) {
crc = crc32(crc, *value);
}
return 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);
}
}
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