use std::io; use super::u16_to_hex;use crate::{encode::Error, Channel, DELIMITER_LINE, ERR_PREFIX, FLUSH_LINE, MAX_DATA_LEN, RESPONSE_END_LINE}; /// Write a response-end message to `out`.pub fn response_end_to_write(mut out: impl io::Write) -> io::Result<usize> {    out.write_all(RESPONSE_END_LINE).map(|_| 4)} /// Write a delim message to `out`.pub fn delim_to_write(mut out: impl io::Write) -> io::Result<usize> {    out.write_all(DELIMITER_LINE).map(|_| 4)} /// Write a flush message to `out`.pub fn flush_to_write(mut out: impl io::Write) -> io::Result<usize> {    out.write_all(FLUSH_LINE).map(|_| 4)} /// Write an error `message` to `out`.pub fn error_to_write(message: &[u8], out: impl io::Write) -> io::Result<usize> {    prefixed_data_to_write(ERR_PREFIX, message, out)} /// Write `data` of `kind` to `out` using side-band encoding.pub fn band_to_write(kind: Channel, data: &[u8], out: impl io::Write) -> io::Result<usize> {    prefixed_data_to_write(&[kind as u8], data, out)} /// Write a `data` message to `out`.pub fn data_to_write(data: &[u8], out: impl io::Write) -> io::Result<usize> {    prefixed_data_to_write(&[], data, out)} /// Write a `text` message to `out`, which is assured to end in a newline.pub fn text_to_write(text: &[u8], out: impl io::Write) -> io::Result<usize> {    prefixed_and_suffixed_data_to_write(&[], text, &[b'\n'], out)} fn prefixed_data_to_write(prefix: &[u8], data: &[u8], out: impl io::Write) -> io::Result<usize> {    prefixed_and_suffixed_data_to_write(prefix, data, &[], out)} fn prefixed_and_suffixed_data_to_write(    prefix: &[u8],    data: &[u8],    suffix: &[u8],    mut out: impl io::Write,) -> io::Result<usize> {    let data_len = prefix.len() + data.len() + suffix.len();    if data_len > MAX_DATA_LEN {        return Err(io::Error::new(            io::ErrorKind::Other,            Error::DataLengthLimitExceeded(data_len),        ));    }    if data.is_empty() {        return Err(io::Error::new(io::ErrorKind::Other, Error::DataIsEmpty));    }     let data_len = data_len + 4;    let buf = u16_to_hex(data_len as u16);     out.write_all(&buf)?;    if !prefix.is_empty() {        out.write_all(prefix)?;    }    out.write_all(data)?;    if !suffix.is_empty() {        out.write_all(suffix)?;    }    Ok(data_len)}