Function spectrusty_formats::mdr::checksum

pub fn checksum<I: IntoIterator<Item = B>, B: Borrow<u8>>(iter: I) -> u8

Checksum calculating routine used by Spectrum for Microdrive data.

Examples found in repository

src/mdr.rs (line 545)

    fn update_block_checksums(&mut self) {
        self.data[DESCHK] = checksum(&self.data[0..DESCHK]);
        self.data[DCHK]   = checksum(&self.data[DESCHK + 1..DCHK])
    }

    fn erase(&mut self) {
        self.data[RECFLG] = 0;
        self.data[RECLEN..RECLEN + 2].iter_mut().for_each(|p| *p=0);
        self.data[DESCHK] = checksum(&self.data[0..DESCHK]);
    }

    fn format(&mut self, seq: u8, catalog_name: &[u8]) {
        if !(1..=245).contains(&seq) {
            panic!("HDNUMB must be between 1 and 254");
        }
        self.head[HDFLAG] = 1;
        self.head[HDNUMB] = seq;
        let head_name = &mut self.head[HDNAME..HDNAME + 10];
        copy_name(head_name.try_into().unwrap(), catalog_name);
        self.head[HDCHK] = checksum(&self.head[0..HDCHK]);
        self.erase();
    }

    fn validate(&self) -> Result<(), &'static str> {
        if self.head[HDFLAG] & 1 != 1 {
            return Err("bad sector header: HDFLAG bit 0 is reset");
        }
        if self.data[RECFLG] & 1 != 0 {
            return Err("bad data block: RECFLG bit 0 is set");
        }
        if !(1..=254).contains(&self.head[HDNUMB]) {
            return Err("bad sector header: HDNUMB is outside the allowed range: [1-254]");
        }
        if self.file_block_len() > BLOCK_DATA_MAX {
            return Err("bad data block: RECLEN is larger than the sector size: 512");
        }
        if self.head[HDCHK] != checksum(&self.head[0..HDCHK]) {
            return Err("bad sector header: HDCHK invalid checksum");
        }
        if self.data[DESCHK] != checksum(&self.data[0..DESCHK]) {
            return Err("bad data block: DESCHK invalid header checksum");
        }
        if !self.is_free() &&
           self.data[DCHK] != checksum(&self.data[DESCHK+1..DCHK])
        {
            return Err("bad data block: DESCHK invalid data checksum");
        }
        Ok(())
    }