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updated crc algorithm to a more efficient implementation

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judge
2026-03-25 13:54:20 +01:00
parent 5ab61e77d6
commit 6b82ddcd74
1 changed files with 7 additions and 10 deletions
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lib-bms-protocol/src/types.rs
+7 -10
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@@ -332,7 +332,7 @@ pub fn check_hemming(data: u32, hemming: u8) -> Result<(), HemmingCorrectionValu
/// CRC-6 calculation using polynomial 0x21 (MSB first) /// CRC-6 calculation using polynomial 0x21 (MSB first)
/// ///
/// This function calculates a 6-bit CRC for 26 bits of data. /// This function calculates a 6-bit CRC for a u32 value.
/// The polynomial used is 0x21 in the crc world polynoms /// The polynomial used is 0x21 in the crc world polynoms
/// are named after the bit pattern with implicit assumption /// are named after the bit pattern with implicit assumption
/// of the trailing 1, thus 0x21 become 0x43 referring to /// of the trailing 1, thus 0x21 become 0x43 referring to
@@ -349,18 +349,15 @@ pub fn check_hemming(data: u32, hemming: u8) -> Result<(), HemmingCorrectionValu
/// - All double-bit errors /// - All double-bit errors
/// - Random errors with a probability of 2^-6 = 0.015625 of going undetected /// - Random errors with a probability of 2^-6 = 0.015625 of going undetected
pub fn calc_crc6(data: u32) -> u8 { pub fn calc_crc6(data: u32) -> u8 {
let mut working_data: u32 = data << 6; let mut crc: u8 = 0x00;
let mut polynom: u32 = 0x43 << 25; for pos in 0..32 {
let mut mask: u32 = 0x40 << 25; if ((data >> (31-pos)) & 0x1) ^ ((crc >> 5) & 0x1) as u32 != 0 {
while working_data >= 0x40 { crc = ((crc << 1) ^ 0x03) & 0x3F;
if working_data & mask != 0 {
working_data ^= polynom;
} else { } else {
polynom >>= 1; crc = (crc << 1) & 0x3F;
mask >>= 1;
} }
} }
(working_data & 0x3f) as u8 crc
} }
/// CRC-6 checking /// CRC-6 checking