use bstr::BString;use quick_error::quick_error; use crate::{PacketLine, DELIMITER_LINE, FLUSH_LINE, MAX_DATA_LEN, MAX_LINE_LEN, RESPONSE_END_LINE, U16_HEX_BYTES}; quick_error! {    /// The error used in the [`decode`][crate::decode] module    #[derive(Debug)]    #[allow(missing_docs)]    pub enum Error {        HexDecode(err: String) {            display("Failed to decode the first four hex bytes indicating the line length: {}", err)        }        DataLengthLimitExceeded(length_in_bytes: usize) {            display("The data received claims to be larger than than the maximum allowed size: got {}, exceeds {}", length_in_bytes, MAX_DATA_LEN)        }        DataIsEmpty {            display("Received an invalid empty line")        }        InvalidLineLength {            display("Received an invalid line of length 3")        }        Line(data: BString, bytes_consumed: usize) {            display("{}", data)        }        NotEnoughData(bytes_needed: usize) {            display("Needing {} additional bytes to decode the line successfully", bytes_needed)        }    }} /// A utility return type to support incremental parsing of packet lines.#[derive(Debug, Clone)]pub enum Stream<'a> {    /// Indicate a single packet line was parsed completely    Complete {        /// The parsed packet line        line: PacketLine<'a>,        /// The amount of bytes consumed from input        bytes_consumed: usize,    },    /// A packet line could not yet be parsed to to missing bytes    Incomplete {        /// The amount of additional bytes needed for the parsing to complete        bytes_needed: usize,    },} /// The result of [`hex_prefix()`] indicating either a special packet line or the amount of wanted bytespub enum PacketLineOrWantedSize<'a> {    /// The special kind of packet line decoded from the hex prefix. It never contains actual data.    Line(PacketLine<'a>),    /// The amount of bytes indicated by the hex prefix of the packet line.    Wanted(u16),} /// Decode the `four_bytes` packet line prefix provided in hexadecimal form and check it for validity.pub fn hex_prefix(four_bytes: &[u8]) -> Result<PacketLineOrWantedSize<'_>, Error> {    debug_assert_eq!(four_bytes.len(), 4, "need four hex bytes");    for (line_bytes, line_type) in &[        (FLUSH_LINE, PacketLine::Flush),        (DELIMITER_LINE, PacketLine::Delimiter),        (RESPONSE_END_LINE, PacketLine::ResponseEnd),    ] {        if four_bytes == *line_bytes {            return Ok(PacketLineOrWantedSize::Line(*line_type));        }    }     let mut buf = [0u8; U16_HEX_BYTES / 2];    hex::decode_to_slice(four_bytes, &mut buf).map_err(|err| Error::HexDecode(err.to_string()))?;    let wanted_bytes = u16::from_be_bytes(buf);     if wanted_bytes == 3 {        return Err(Error::InvalidLineLength);    }    if wanted_bytes == 4 {        return Err(Error::DataIsEmpty);    }    debug_assert!(        wanted_bytes as usize > U16_HEX_BYTES,        "by now there should be more wanted bytes than prefix bytes"    );    Ok(PacketLineOrWantedSize::Wanted(wanted_bytes - U16_HEX_BYTES as u16))} /// Obtain a `PacketLine` from `data` after assuring `data` is small enough to fit.pub fn to_data_line(data: &[u8]) -> Result<PacketLine<'_>, Error> {    if data.len() > MAX_LINE_LEN {        return Err(Error::DataLengthLimitExceeded(data.len()));    }     Ok(PacketLine::Data(data))} /// Decode `data` as packet line while reporting whether the data is complete or not using a [`Stream`].pub fn streaming(data: &[u8]) -> Result<Stream<'_>, Error> {    let data_len = data.len();    if data_len < U16_HEX_BYTES {        return Ok(Stream::Incomplete {            bytes_needed: U16_HEX_BYTES - data_len,        });    }    let wanted_bytes = match hex_prefix(&data[..U16_HEX_BYTES])? {        PacketLineOrWantedSize::Wanted(s) => s as usize,        PacketLineOrWantedSize::Line(line) => {            return Ok(Stream::Complete {                line,                bytes_consumed: 4,            })        }    } + U16_HEX_BYTES;    if wanted_bytes > MAX_LINE_LEN {        return Err(Error::DataLengthLimitExceeded(wanted_bytes));    }    if data_len < wanted_bytes {        return Ok(Stream::Incomplete {            bytes_needed: wanted_bytes - data_len,        });    }     Ok(Stream::Complete {        line: to_data_line(&data[U16_HEX_BYTES..wanted_bytes])?,        bytes_consumed: wanted_bytes,    })} /// Decode an entire packet line from data or fail.////// Note that failure also happens if there is not enough data to parse a complete packet line, as opposed to [`streaming()`] decoding/// succeeds in that case, stating how much more bytes are required.pub fn all_at_once(data: &[u8]) -> Result<PacketLine<'_>, Error> {    match streaming(data)? {        Stream::Complete { line, .. } => Ok(line),        Stream::Incomplete { bytes_needed } => Err(Error::NotEnoughData(bytes_needed)),    }}