osdp 0.3.0

Pure-Rust, no_std-friendly implementation of the SIA Open Supervised Device Protocol (OSDP) v2.2
Documentation 
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//! `osdp_RMAC_I` (`0x78`) — initial R-MAC.
//!
//! # Spec: §7.17, Annex D.4

use crate::error::Error;
use crate::payload_util::require_exact_len;
use alloc::vec::Vec;

/// `osdp_RMAC_I` body.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct RMacI {
    /// Initial R-MAC seed (16 bytes).
    pub r_mac_i: [u8; 16],
}

impl RMacI {
    /// Encode.
    pub fn encode(&self) -> Result<Vec<u8>, Error> {
        Ok(self.r_mac_i.to_vec())
    }

    /// Decode.
    pub fn decode(data: &[u8]) -> Result<Self, Error> {
        require_exact_len(data, 16, 0x78)?;
        let mut r_mac_i = [0u8; 16];
        r_mac_i.copy_from_slice(data);
        Ok(Self { r_mac_i })
    }
}

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

    #[test]
    fn roundtrip() {
        let body = RMacI {
            r_mac_i: [0x77; 16],
        };
        let bytes = body.encode().unwrap();
        assert_eq!(bytes.len(), 16);
        assert_eq!(RMacI::decode(&bytes).unwrap(), body);
    }

    #[test]
    fn decode_rejects_wrong_length() {
        assert!(matches!(
            RMacI::decode(&[0; 15]),
            Err(Error::PayloadLength { code: 0x78, .. })
        ));
    }
}