srec 0.2.0

use std::num::Wrapping;

pub fn checksum_of(data: &[u8]) -> u8 {
    !data.iter().map(|b| Wrapping(*b)).sum::<Wrapping<u8>>().0
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn checksum_of_returns_correct_value() {
        // All sourced from the Wikipedia SREC article
        // https://en.wikipedia.org/wiki/SREC_(file_format)
        assert_eq!(
            checksum_of(&vec![
                0x13, 0x7a, 0xf0, 0x0a, 0x0a, 0x0d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0x00, 0x00
            ]),
            0x61
        );

        assert_eq!(
            checksum_of(&vec![
                0x0f, 0x00, 0x00, 0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x20, 0x20, 0x20, 0x20, 0x00,
                0x00
            ]),
            0x3c
        );

        assert_eq!(
            checksum_of(&vec![
                0x1f, 0x00, 0x00, 0x7c, 0x08, 0x02, 0xa6, 0x90, 0x01, 0x00, 0x04, 0x94, 0x21, 0xff,
                0xf0, 0x7c, 0x6c, 0x1b, 0x78, 0x7c, 0x8c, 0x23, 0x78, 0x3c, 0x60, 0x00, 0x00, 0x38,
                0x63, 0x00, 0x00
            ]),
            0x26
        );

        assert_eq!(
            checksum_of(&vec![
                0x1f, 0x00, 0x1c, 0x4b, 0xff, 0xff, 0xe5, 0x39, 0x80, 0x00, 0x00, 0x7d, 0x83, 0x63,
                0x78, 0x80, 0x01, 0x00, 0x14, 0x38, 0x21, 0x00, 0x10, 0x7c, 0x08, 0x03, 0xa6, 0x4e,
                0x80, 0x00, 0x20
            ]),
            0xe9
        );

        assert_eq!(
            checksum_of(&vec![
                0x11, 0x00, 0x38, 0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x77, 0x6f, 0x72, 0x6c, 0x64,
                0x2e, 0x0a, 0x00
            ]),
            0x42
        );

        assert_eq!(checksum_of(&vec![0x03, 0x00, 0x03]), 0xf9);

        assert_eq!(checksum_of(&vec![0x03, 0x00, 0x00]), 0xfc);
    }

}