Struct LineColLookup

pub struct LineColLookup<'source> { /* private fields */ }

Pre-cached line/column lookup table for a string slice.

Implementations

impl<'source> LineColLookup<'source>

pub fn new(src: &'source str) -> Self

Creates a new line/col lookup table. The src parameter provides the input string used to calculate lines and columns.

Internally, this scans src and caches the starting positions of all lines. This means this is an O(n) operation.

pub fn get(&self, index: usize) -> (usize, usize)

Looks up the 1-based line and column numbers of the specified byte index.

Returns a tuple with the line number first, then column number.

Example

use line_col::*;
let text = "One\nTwo";
let lookup = LineColLookup::new(text);
assert_eq!(lookup.get(0), (1, 1)); // 'O' (line 1, col 1)
assert_eq!(lookup.get(1), (1, 2)); // 'n' (line 1, col 2)
assert_eq!(lookup.get(2), (1, 3)); // 'e' (line 1, col 3)
assert_eq!(lookup.get(4), (2, 1)); // 'T' (line 2, col 1)
assert_eq!(lookup.get(5), (2, 2)); // 'w' (line 2, col 2)
assert_eq!(lookup.get(6), (2, 3)); // 'o' (line 2, col 3)
assert_eq!(lookup.get(7), (2, 4)); // <end> (line 2, col 4)

Panics

Panics if index is greater than the length of the input &str.

Notes

This function uses a binary search to locate the line on which index resides. This means that it runs in approximately O(log n) time.

pub fn get_by_cluster(&self, index: usize) -> (usize, usize)

Looks up the 1-based line and column numbers of the specified byte index. The column number correlates to the number of grapheme clusters up to and at the specified index.

Returns a tuple with the line number first, then column number.

Panics

Panics if index is greater than the length of the input &str.

Notes

This function uses a binary search to locate the line on which index resides. This means that it runs in approximately O(log n) time.