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//! Conversion of byte positions to line/column locations.
use super::Scanner;
use crate::syntax::{Location, Pos};
/// Enables conversion of byte position to locations.
pub struct LineMap<'s> {
src: &'s str,
line_starts: Vec<Pos>,
}
impl<'s> LineMap<'s> {
/// Create a new line map for a source string.
pub fn new(src: &'s str) -> Self {
let mut line_starts = vec![Pos::ZERO];
let mut s = Scanner::new(src);
while let Some(c) = s.eat_merging_crlf() {
if is_newline(c) {
line_starts.push(s.index().into());
}
}
Self { src, line_starts }
}
/// Convert a byte position to a location.
///
/// # Panics
/// This panics if the position is out of bounds.
pub fn location(&self, pos: Pos) -> Location {
let line_index = match self.line_starts.binary_search(&pos) {
Ok(i) => i,
Err(i) => i - 1,
};
let line_start = self.line_starts[line_index];
let head = &self.src[line_start.to_usize() .. pos.to_usize()];
let column_index = head.chars().count();
Location {
line: 1 + line_index as u32,
column: 1 + column_index as u32,
}
}
}
/// Whether this character denotes a newline.
pub fn is_newline(character: char) -> bool {
match character {
// Line Feed, Vertical Tab, Form Feed, Carriage Return.
'\n' | '\x0B' | '\x0C' | '\r' |
// Next Line, Line Separator, Paragraph Separator.
'\u{0085}' | '\u{2028}' | '\u{2029}' => true,
_ => false,
}
}
#[cfg(test)]
mod tests {
use super::*;
const TEST: &str = "äbcde\nf💛g\r\nhi\rjkl";
#[test]
fn test_line_map_new() {
let map = LineMap::new(TEST);
assert_eq!(map.line_starts, vec![Pos(0), Pos(7), Pos(15), Pos(18)]);
}
#[test]
fn test_line_map_location() {
let map = LineMap::new(TEST);
assert_eq!(map.location(Pos(0)), Location::new(1, 1));
assert_eq!(map.location(Pos(2)), Location::new(1, 2));
assert_eq!(map.location(Pos(6)), Location::new(1, 6));
assert_eq!(map.location(Pos(7)), Location::new(2, 1));
assert_eq!(map.location(Pos(8)), Location::new(2, 2));
assert_eq!(map.location(Pos(12)), Location::new(2, 3));
assert_eq!(map.location(Pos(21)), Location::new(4, 4));
}
#[test]
#[should_panic]
fn test_line_map_panics_out_of_bounds() {
LineMap::new(TEST).location(Pos(22));
}
}
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