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//! Line ending detection and conversion.
use std::fmt::Debug;
/// Supported line endings. Like in the Rust standard library, two line
/// endings are supported: `\r\n` and `\n`
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum LineEnding {
/// _Carriage return and line feed_ – a line ending sequence
/// historically used in Windows. Corresponds to the sequence
/// of ASCII control characters `0x0D 0x0A` or `\r\n`
CRLF,
/// _Line feed_ – a line ending historically used in Unix.
/// Corresponds to the ASCII control character `0x0A` or `\n`
LF,
}
impl LineEnding {
/// Turns this [`LineEnding`] value into its ASCII representation.
#[inline]
pub const fn as_str(&self) -> &'static str {
match self {
Self::CRLF => "\r\n",
Self::LF => "\n",
}
}
}
/// An iterator over the lines of a string, as tuples of string slice
/// and [`LineEnding`] value; it only emits non-empty lines (i.e. having
/// some content before the terminating `\r\n` or `\n`).
///
/// This struct is used internally by the library.
#[derive(Debug, Clone, Copy)]
pub(crate) struct NonEmptyLines<'a>(pub &'a str);
impl<'a> Iterator for NonEmptyLines<'a> {
type Item = (&'a str, Option<LineEnding>);
fn next(&mut self) -> Option<Self::Item> {
while let Some(lf) = self.0.find('\n') {
if lf == 0 || (lf == 1 && self.0.as_bytes()[lf - 1] == b'\r') {
self.0 = &self.0[(lf + 1)..];
continue;
}
let trimmed = match self.0.as_bytes()[lf - 1] {
b'\r' => (&self.0[..(lf - 1)], Some(LineEnding::CRLF)),
_ => (&self.0[..lf], Some(LineEnding::LF)),
};
self.0 = &self.0[(lf + 1)..];
return Some(trimmed);
}
if self.0.is_empty() {
None
} else {
let line = std::mem::take(&mut self.0);
Some((line, None))
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn non_empty_lines_full_case() {
assert_eq!(
NonEmptyLines("LF\nCRLF\r\n\r\n\nunterminated")
.collect::<Vec<(&str, Option<LineEnding>)>>(),
vec![
("LF", Some(LineEnding::LF)),
("CRLF", Some(LineEnding::CRLF)),
("unterminated", None),
]
);
}
#[test]
fn non_empty_lines_new_lines_only() {
assert_eq!(NonEmptyLines("\r\n\n\n\r\n").next(), None);
}
#[test]
fn non_empty_lines_no_input() {
assert_eq!(NonEmptyLines("").next(), None);
}
}