use crate::{MAX_DATA_LEN, U16_HEX_BYTES};use std::io; /// An implementor of [`Write`][io::Write] which passes all input to an inner `Write` in packet line data encoding,/// one line per `write(…)` call or as many lines as it takes if the data doesn't fit into the maximum allowed line length.pub struct Writer<T> {    /// the `Write` implementation to which to propagate packet lines    pub inner: T,    binary: bool,} impl<T: io::Write> Writer<T> {    /// Create a new instance from the given `write`    pub fn new(write: T) -> Self {        Writer {            inner: write,            binary: true,        }    }    /// If called, each call to [`write()`][io::Write::write()] will write bytes as is.    pub fn enable_binary_mode(&mut self) {        self.binary = true;    }    /// If called, each call to [`write()`][io::Write::write()] will write the input as text, appending a trailing newline    /// if needed before writing.    pub fn enable_text_mode(&mut self) {        self.binary = false;    }    /// As [`enable_text_mode()`][Writer::enable_text_mode()], but suitable for chaining.    pub fn text_mode(mut self) -> Self {        self.binary = false;        self    }    /// As [`enable_binary_mode()`][Writer::enable_binary_mode()], but suitable for chaining.    pub fn binary_mode(mut self) -> Self {        self.binary = true;        self    }} impl<T: io::Write> io::Write for Writer<T> {    fn write(&mut self, mut buf: &[u8]) -> io::Result<usize> {        if buf.is_empty() {            return Err(io::Error::new(                io::ErrorKind::Other,                "empty packet lines are not permitted as '0004' is invalid",            ));        }         let mut written = 0;        while !buf.is_empty() {            let (data, rest) = buf.split_at(buf.len().min(MAX_DATA_LEN));            written += if self.binary {                crate::encode::data_to_write(data, &mut self.inner)            } else {                crate::encode::text_to_write(data, &mut self.inner)            }            .map_err(|err| {                use crate::encode::Error::*;                match err {                    Io(err) => err,                    DataIsEmpty | DataLengthLimitExceeded(_) => {                        unreachable!("We are handling empty and large data here, so this can't ever happen")                    }                }            })?;            // subtract header (and trailng NL) because write-all can't handle writing more than it passes in            written -= U16_HEX_BYTES + if self.binary { 0 } else { 1 };            buf = rest;        }        Ok(written)    }     fn flush(&mut self) -> io::Result<()> {        self.inner.flush()    }}