pest/iterators/
line_index.rs

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1//! `LineIndex` to make a line_offsets, each item is an byte offset (start from 0) of the beginning of the line.
2//!
3//! For example, the text: `"hello 你好\nworld"`, the line_offsets will store `[0, 13]`.
4//!
5//! Then `line_col` with a offset just need to find the line index by binary search.
6//!
7//! Inspired by rust-analyzer's `LineIndex`:
8//! <https://github.com/rust-lang/rust/blob/1.67.0/src/tools/rust-analyzer/crates/ide-db/src/line_index.rs>
9use alloc::vec::Vec;
10
11#[derive(Clone)]
12pub struct LineIndex {
13    /// Offset (bytes) the the beginning of each line, zero-based
14    line_offsets: Vec<usize>,
15}
16
17impl LineIndex {
18    pub fn new(text: &str) -> LineIndex {
19        let mut line_offsets: Vec<usize> = alloc::vec![0];
20
21        let mut offset = 0;
22
23        for c in text.chars() {
24            offset += c.len_utf8();
25            if c == '\n' {
26                line_offsets.push(offset);
27            }
28        }
29
30        LineIndex { line_offsets }
31    }
32
33    /// Returns (line, col) of pos.
34    ///
35    /// The pos is a byte offset, start from 0, e.g. "ab" is 2, "你好" is 6
36    pub fn line_col(&self, input: &str, pos: usize) -> (usize, usize) {
37        let line = self.line_offsets.partition_point(|&it| it <= pos) - 1;
38        let first_offset = self.line_offsets[line];
39
40        // Get line str from original input, then we can get column offset
41        let line_str = &input[first_offset..pos];
42        let col = line_str.chars().count();
43
44        (line + 1, col + 1)
45    }
46}
47
48#[cfg(test)]
49mod tests {
50    use super::*;
51
52    #[allow(clippy::zero_prefixed_literal)]
53    #[test]
54    fn test_line_index() {
55        let text = "hello 你好 A🎈C\nworld";
56        let table = [
57            (00, 1, 1, 'h'),
58            (01, 1, 2, 'e'),
59            (02, 1, 3, 'l'),
60            (03, 1, 4, 'l'),
61            (04, 1, 5, 'o'),
62            (05, 1, 6, ' '),
63            (06, 1, 7, '你'),
64            (09, 1, 8, '好'),
65            (12, 1, 9, ' '),
66            (13, 1, 10, 'A'),
67            (14, 1, 11, '🎈'),
68            (18, 1, 12, 'C'),
69            (19, 1, 13, '\n'),
70            (20, 2, 1, 'w'),
71            (21, 2, 2, 'o'),
72            (22, 2, 3, 'r'),
73            (23, 2, 4, 'l'),
74            (24, 2, 5, 'd'),
75        ];
76
77        let index = LineIndex::new(text);
78        for &(offset, line, col, c) in table.iter() {
79            let res = index.line_col(text, offset);
80            assert_eq!(
81                (res.0, res.1),
82                (line, col),
83                "Expected: ({}, {}, {}, {:?})",
84                offset,
85                line,
86                col,
87                c
88            );
89        }
90    }
91}
pest/iterators/line_index.rs

pest/iterators/
line_index.rs
