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//! Version of `std::str::Lines` that tracks line numbers and has `remainder()`
use extend::ext;
/// 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`
#[ext(name = StrExt)]
pub impl 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 {
&self[0..self.len().checked_sub(count).expect("stripping too much")]
/// 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
/// Return a `Lines` like `self` but which always yields `None`
/// Useful for certain error handling cases.
/// The returned `Lines`:
/// * Reports the same line number as `self` would now
/// * Returns `None` from `peek` and `next`
/// * Returns `""` from `remaining` (the returned slice is the end of the real input,
/// not a fresh empty slice).
pub fn clone_entirely_consumed(&self) -> Lines<'s> {
Lines {
lno: self.lno,
rest: self
.rest
.rsplit_once("")
.expect("all strings contain the empty string")
.1,
/// After `peek`, advance to the next line, consuming the one that was peeked
/// See [`Peeked`].
#[allow(clippy::needless_pass_by_value)] // Yes, we want to consume Peeked
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
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)