Function spectrusty_formats::tap::try_checksum

source · 
pub fn try_checksum<I: IntoIterator<Item = Result<u8>>>(iter: I) -> Result<u8>
Expand description

Calculates bit toggle checksum from the given iterator of the result of u8. Useful with std::io::Bytes.

Examples found in repository?
src/tap/read.rs (line 172)
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    fn try_from(rd: &mut Take<R>) -> Result<Self> {
        let limit = match rd.limit() {
            0 => {
                return Ok(TapChunkInfo::Empty)
            }
            limit if limit > u16::max_value().into() => {
                return Err(Error::new(ErrorKind::InvalidData, "Not a proper TAP chunk: too large"));
            }
            limit => limit
        };
        let mut flag: u8 = 0;
        rd.read_exact(slice::from_mut(&mut flag))?;
        if limit == 1 {
            return Ok(TapChunkInfo::Unknown { size: 1, flag })
        }
        match flag {
            HEAD_BLOCK_FLAG if limit == HEADER_SIZE as u64 => {
                let mut header: [u8; HEADER_SIZE - 1] = Default::default();
                rd.read_exact(&mut header)?;
                if checksum(header) != flag {
                    Ok(TapChunkInfo::Unknown { size: limit as u16, flag })
                }
                else {
                    Header::try_from(&header[..HEADER_SIZE - 2])
                    .map(TapChunkInfo::Head)
                    .or(Ok(TapChunkInfo::Unknown { size: limit as u16, flag }))
                }
            }
            DATA_BLOCK_FLAG => {
                let checksum = try_checksum(rd.by_ref().bytes())? ^ flag;
                if rd.limit() != 0 {
                    return Err(Error::new(ErrorKind::InvalidData, "Not a proper TAP block: invalid length"));
                }
                Ok(TapChunkInfo::Data{ length: limit as u16 - 2, checksum })
            }
            flag => {
                // TODO: perhaps check length and read to eof
                Ok(TapChunkInfo::Unknown { size: limit as u16, flag })
            }
        }
    }