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#[cfg(test)]
mod fingerprint_test;
use crate::attributes::ATTR_FINGERPRINT;
use crate::checks::*;
use crate::error::*;
use crate::message::*;
use crc::{Crc, CRC_32_ISO_HDLC};
pub struct FingerprintAttr;
pub const FINGERPRINT: FingerprintAttr = FingerprintAttr {};
pub const FINGERPRINT_XOR_VALUE: u32 = 0x5354554e;
pub const FINGERPRINT_SIZE: usize = 4;
pub fn fingerprint_value(b: &[u8]) -> u32 {
let checksum = Crc::<u32>::new(&CRC_32_ISO_HDLC).checksum(b);
checksum ^ FINGERPRINT_XOR_VALUE
}
impl Setter for FingerprintAttr {
fn add_to(&self, m: &mut Message) -> Result<()> {
let l = m.length;
m.length += (FINGERPRINT_SIZE + ATTRIBUTE_HEADER_SIZE) as u32;
m.write_length();
let val = fingerprint_value(&m.raw);
let b = val.to_be_bytes();
m.length = l;
m.add(ATTR_FINGERPRINT, &b);
Ok(())
}
}
impl FingerprintAttr {
pub fn check(&self, m: &Message) -> Result<()> {
let b = m.get(ATTR_FINGERPRINT)?;
check_size(ATTR_FINGERPRINT, b.len(), FINGERPRINT_SIZE)?;
let val = u32::from_be_bytes([b[0], b[1], b[2], b[3]]);
let attr_start = m.raw.len() - (FINGERPRINT_SIZE + ATTRIBUTE_HEADER_SIZE);
let expected = fingerprint_value(&m.raw[..attr_start]);
check_fingerprint(val, expected)
}
}