identification.rs

use arrayvec::ArrayString;

#[derive(Debug, PartialEq, Eq, Clone)]
pub struct Identification {
    pub callsign: ArrayString<252>,
    pub ssid: u8,
    pub icon: u16,
}

impl Identification {
    pub fn new(call: &str, ssid: u8, icon: u16) -> Option<Self> {
        let callsign = ArrayString::from(call).ok()?;

        Some(Self {
            icon,
            callsign,
            ssid,
        })
    }

    /// Returns none if there is not enough space in the buffer
    pub fn encode<'a>(&self, buf: &'a mut [u8]) -> Option<&'a [u8]> {
        // safe to unwrap because we know the length is <= 252
        let len: u8 = self.callsign.as_bytes().len().try_into().unwrap();
        *buf.get_mut(0)? = len + 3;

        buf.get_mut(1..3)?.copy_from_slice(&self.icon.to_le_bytes());

        let mut len = 3;
        for (i, b) in self.callsign.as_bytes().iter().enumerate() {
            *buf.get_mut(i + 3)? = *b;
            len += 1
        }

        *buf.get_mut(len)? = self.ssid;
        len += 1;

        Some(&buf[0..len])
    }

    pub fn decode(data: &[u8]) -> Option<Self> {
        let len = (*data.first()?).into();

        let icon = u16::from_le_bytes([*data.get(1)?, *data.get(2)?]);

        let callsign = core::str::from_utf8(data.get(3..len)?).ok()?;
        let callsign = ArrayString::from(callsign).ok()?;

        let ssid = *data.get(len)?;

        Some(Self {
            icon,
            callsign,
            ssid,
        })
    }
}