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//! Version of `std::str::Lines` that tracks line numbers and has `remainder()`
/// Version of `std::str::Lines` that tracks line numbers and has `remainder()`
///
/// Implements `Iterator`, returning one `str` for each line, with the `'\n'` removed.
///
/// Missing final newline is silently tolerated.
#[derive(Debug, Clone)]
pub struct Lines<'s> {
/// Line number at the start of `rest`
lno: usize,
/// The remaining part of the document
rest: &'s str,
}
/// Extension trait adding a method to `str`
pub trait StrExt: AsRef<str> {
/// Remove `count` bytes from the end of `self`
///
/// # Panics
///
/// Panics if `count > self.len()`.
#[allow(clippy::string_slice)] // TODO
fn strip_end_counted(&self, count: usize) -> &str {
let s = self.as_ref();
&s[0..s.len().checked_sub(count).expect("stripping too much")]
}
}
impl StrExt for str {}
/// Information about the next line we have peeked
///
/// To get the line as an actual string, pass this to `peeked_line`.
///
/// # Correctness
///
/// Each `Peeked` is only valid in conjunction with the `Lines` that returned it,
/// and becomes invalidated if the `Lines` is modified
/// (ie, it can be invalidated by calls that take `&mut Lines`).
///
/// Cloning a `Peeked` is hazrdous since using it twice would be wrong.
///
/// None of this is checked at compile- or run-time.
// We could perhaps use lifetimes somehow to enforce this,
// but `ItemStream` wants `Peeked` to be `'static` and `Clone`.
#[derive(Debug, Clone, amplify::Getters)]
pub struct Peeked {
/// The length of the next line
//
// # Invariant
//
// `rest[line_len]` is a newline, or `line_len` is `rest.len()`.
#[getter(as_copy)]
line_len: usize,
}
impl<'s> Lines<'s> {
/// Start reading lines from a document as a string
pub fn new(s: &'s str) -> Self {
Lines { lno: 1, rest: s }
}
/// Line number of the next line we'll read
pub fn peek_lno(&self) -> usize {
self.lno
}
/// Peek the next line
pub fn peek(&self) -> Option<Peeked> {
if self.rest.is_empty() {
None
} else if let Some(newline) = self.rest.find('\n') {
Some(Peeked { line_len: newline })
} else {
Some(Peeked {
line_len: self.rest.len(),
})
}
}
/// The rest of the file as a `str`
pub fn remaining(&self) -> &'s str {
self.rest
}
/// After `peek`, advance to the next line, consuming the one that was peeked
///
/// # Correctness
///
/// See [`Peeked`].
#[allow(clippy::needless_pass_by_value)] // Yes, we want to consume Peeked
#[allow(clippy::string_slice)] // TODO
pub fn consume_peeked(&mut self, peeked: Peeked) -> &'s str {
let line = self.peeked_line(&peeked);
self.rest = &self.rest[peeked.line_len..];
if !self.rest.is_empty() {
debug_assert!(self.rest.starts_with('\n'));
self.rest = &self.rest[1..];
}
self.lno += 1;
line
}
/// After `peek`, obtain the actual peeked line as a `str`
///
/// As with [`<Lines as Iterator>::next`](Lines::next), does not include the newline.
// Rustdoc doesn't support linking` fully qualified syntax.
// https://github.com/rust-lang/rust/issues/74563
///
/// # Correctness
///
/// See [`Peeked`].
#[allow(clippy::string_slice)] // TODO
pub fn peeked_line(&self, peeked: &Peeked) -> &'s str {
&self.rest[0..peeked.line_len()]
}
}
impl<'s> Iterator for Lines<'s> {
type Item = &'s str;
fn next(&mut self) -> Option<&'s str> {
let peeked = self.peek()?;
let line = self.consume_peeked(peeked);
Some(line)
}
}
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