osdp 0.3.1

Pure-Rust, no_std-friendly implementation of the SIA Open Supervised Device Protocol (OSDP) v2.2
Documentation 
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//! `osdp_FILETRANSFER` (`0x7C`) — chunked file upload to the PD.
//!
//! # Spec: §6.21

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

/// `osdp_FILETRANSFER` body.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct FileTransfer {
    /// Vendor-specific file type.
    pub file_type: u8,
    /// Total file size, in bytes.
    pub total_size: u32,
    /// Byte offset of this fragment.
    pub offset: u32,
    /// File fragment.
    pub fragment: Vec<u8>,
}

impl FileTransfer {
    /// Encode.
    pub fn encode(&self) -> Result<Vec<u8>, Error> {
        if self.fragment.len() > u16::MAX as usize {
            return Err(Error::MalformedPayload {
                code: 0x7C,
                reason: "FILETRANSFER fragment > 65535 bytes",
            });
        }
        let mut out = Vec::with_capacity(11 + self.fragment.len());
        out.push(self.file_type);
        out.extend_from_slice(&self.total_size.to_le_bytes());
        out.extend_from_slice(&self.offset.to_le_bytes());
        out.extend_from_slice(&(self.fragment.len() as u16).to_le_bytes());
        out.extend_from_slice(&self.fragment);
        Ok(out)
    }

    /// Decode.
    pub fn decode(data: &[u8]) -> Result<Self, Error> {
        require_at_least(data, 11, 0x7C)?;
        let total_size = u32::from_le_bytes([data[1], data[2], data[3], data[4]]);
        let offset = u32::from_le_bytes([data[5], data[6], data[7], data[8]]);
        let frag_len = u16::from_le_bytes([data[9], data[10]]) as usize;
        if data.len() != 11 + frag_len {
            return Err(Error::MalformedPayload {
                code: 0x7C,
                reason: "FILETRANSFER fragment length disagrees with payload",
            });
        }
        Ok(Self {
            file_type: data[0],
            total_size,
            offset,
            fragment: data[11..11 + frag_len].to_vec(),
        })
    }
}

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

    #[test]
    fn roundtrip() {
        let body = FileTransfer {
            file_type: 0x07,
            total_size: 0x0000_0100,
            offset: 0x0000_0040,
            fragment: alloc::vec![0xAA, 0xBB, 0xCC],
        };
        let bytes = body.encode().unwrap();
        // file_type | total_size LE | offset LE | frag_len LE | fragment
        assert_eq!(
            bytes,
            [
                0x07, 0x00, 0x01, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x03, 0x00, 0xAA, 0xBB, 0xCC
            ]
        );
        assert_eq!(FileTransfer::decode(&bytes).unwrap(), body);
    }

    #[test]
    fn decode_rejects_short_header() {
        assert!(matches!(
            FileTransfer::decode(&[0; 10]),
            Err(Error::PayloadTooShort { code: 0x7C, .. })
        ));
    }

    #[test]
    fn decode_rejects_length_mismatch() {
        // Header advertises a 5-byte fragment but only 2 bytes follow.
        let bad = [
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0xAA, 0xBB,
        ];
        assert!(matches!(
            FileTransfer::decode(&bad),
            Err(Error::MalformedPayload { code: 0x7C, .. })
        ));
    }
}