fn float(data: &[u8]) -> IResult<&[u8], f32> {
    let mut pos = 0;
    let mut next_nibble = || -> u8 {
        let nibble = (data[pos/2] >> (4 * (pos & 1) as u8)) & 0xf;
        pos += 1;
        nibble
    };

    let mut is_negaive = false;
    let mut digits = vec![];
    let mut power_digits = vec![];
    let mut power_negative = false;
    let mut decimal_point = None;
    loop {
        match next_nibble() {
            d @ 0 ..= 9 => digits.push(b'0' + d),
            0xa => decimal_point = Some(digits.len()),
            b @ 0xb | 0xc  => { // positive 10^x
                power_negative = (b == 0xc);
                loop {
                    match next_nibble() {
                        d @ 0 ..= 9 => power_digits.push(b'0' + d),
                        0xf => break
                    }
                }
            },
            0xd => panic!("reserved"),
            0xe => is_negaive = true,
            0xf => break,
            _ => unreachable!()
        }
    }

    let mut n = i32::parse(&digits);
    if is_negaive {
        n *= -1;
    }
    let mut value = n as f32;
    let mut power = 0;
    if let Some(dp) = decimal_point {
        power += dp - digits.len();
    }
    if power_digits.len() > 0 {
        let mut p = i32::parse(&power_digits);
        if power_negative {
            p *= -1;
        }
        power += p;
    }
    if power != 0 {
        value *= 10.0.powi(power);
    }
    Ok((&data[(pos+1)/2 ..], value))
}