ccsds 0.1.0-beta.25

CCSDS spacecraft data stream decoding
Documentation 
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use super::{Integrity, IntegrityAlgorithm};
use crate::{
    error::{Error, Result},
    framing::VCDUHeader,
};

pub struct DefaultCrc32 {
    /// Offset to the start of the crc checksum bytes
    offset: usize,
    size: usize,
    alg: crc::Crc<u32>,
}

impl DefaultCrc32 {
    const CRC_SIZE: usize = 4;
    pub fn new(offset: usize) -> Self {
        Self {
            offset,
            size: offset + Self::CRC_SIZE,
            alg: crc::Crc::<u32>::new(&crc::CRC_32_ISO_HDLC),
        }
    }
}

impl IntegrityAlgorithm for DefaultCrc32 {
    fn perform(&self, header: &VCDUHeader, cadu_dat: &[u8]) -> Result<(Integrity, Vec<u8>)> {
        if cadu_dat.len() < self.size {
            return Err(Error::NotEnoughData {
                got: cadu_dat.len(),
                wanted: self.size,
            });
        }
        if header.vcid == VCDUHeader::FILL {
            return Ok((Integrity::Skipped, cadu_dat.to_vec()));
        }
        let dat = &cadu_dat[self.offset..self.offset + Self::CRC_SIZE];
        let expected = u32::from_be_bytes([dat[0], dat[1], dat[2], dat[3]]);
        if expected != self.alg.checksum(cadu_dat) {
            return Ok((Integrity::NoErrors, cadu_dat.to_vec()));
        }
        Ok((Integrity::HasErrors, cadu_dat.to_vec()))
    }
}