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//! Newline-delimited protocol helpers shared by the client and server.
//!
//! TLS reads can return more than one line at a time. Keeping the leftover
//! bytes is essential: dropping them silently loses the next message.
use std::io::{self, Read};
#[derive(Debug, Default)]
pub struct LineBuffer {
buffer: Vec<u8>,
}
impl LineBuffer {
pub fn new() -> Self {
Self::default()
}
pub fn push(&mut self, bytes: &[u8]) {
self.buffer.extend_from_slice(bytes);
}
/// Return the next complete line, including a line that ended at EOF.
pub fn next_line(&mut self) -> Option<String> {
let end = self.buffer.iter().position(|byte| *byte == b'\n')?;
let mut line: Vec<u8> = self.buffer.drain(..=end).collect();
line.pop(); // '\n'
if line.last() == Some(&b'\r') {
line.pop();
}
Some(String::from_utf8_lossy(&line).into_owned())
}
/// Return the unterminated remainder at EOF, if any.
pub fn take_rest(&mut self) -> Option<String> {
if self.buffer.is_empty() {
return None;
}
let mut rest = std::mem::take(&mut self.buffer);
if rest.last() == Some(&b'\r') {
rest.pop();
}
Some(String::from_utf8_lossy(&rest).into_owned())
}
/// Read one line from a blocking reader, preserving any extra lines for
/// the next call. Returns `None` at EOF with nothing buffered.
pub fn read_line<R: Read>(&mut self, reader: &mut R) -> io::Result<Option<String>> {
loop {
if let Some(line) = self.next_line() {
return Ok(Some(line));
}
let mut chunk = [0u8; 4096];
match reader.read(&mut chunk) {
Ok(0) => return Ok(self.take_rest()),
Ok(n) => self.push(&chunk[..n]),
Err(error) if error.kind() == io::ErrorKind::Interrupted => continue,
Err(error) => return Err(error),
}
}
}
}
/// A stable, user-facing message for a failed request.
pub fn io_failure_message(error: &io::Error) -> &'static str {
match error.kind() {
io::ErrorKind::TimedOut | io::ErrorKind::WouldBlock => "ERROR Request timed out",
_ => "ERROR Connection lost",
}
}
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