rusty-tpkt 1.0.0

Implements the TPKT standard to encapsulate ISO protocols for TCP transport.
Documentation 
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use std::array::TryFromSliceError;

use bytes::BytesMut;

use crate::api::TpktError;

pub const HEADER_LENGTH: usize = 4;
pub const TPKT_MAGIC_START_NUMBER: u8 = 0x03u8;

pub(crate) enum TpktParserResult {
    InProgress,
    Data(Vec<u8>),
}

pub(crate) struct TpktParser {}

impl TpktParser {
    pub(crate) fn new() -> Self {
        Self {}
    }

    pub(crate) fn parse(&self, data: &mut BytesMut) -> Result<TpktParserResult, TpktError> {
        let packet_length_value = match data.len() {
            0 => return Ok(TpktParserResult::InProgress),
            x if x > 0 && data[0] != TPKT_MAGIC_START_NUMBER => {
                return Err(TpktError::ProtocolError(format!("Invalid Header. Expected 0x03 but was {:#04x}", x).into()));
            }
            // Ignore the version field and just straight to the length.
            x if x > 3 => u16::from_be_bytes(data[2..4].try_into().map_err(|e: TryFromSliceError| TpktError::InternalError(format!("Failed to parse data: {:?}", e.to_string()).into()))?),
            _ => return Ok(TpktParserResult::InProgress),
        } as usize;

        if data.len() < packet_length_value {
            return Ok(TpktParserResult::InProgress);
        }
        let _remove_header = data.split_to(HEADER_LENGTH);
        return Ok(TpktParserResult::Data(data.split_to(packet_length_value - HEADER_LENGTH).to_vec()));
    }
}