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> |
9 | use alloc::vec::Vec; |
10 | |
11 | #[derive (Clone)] |
12 | pub struct LineIndex { |
13 | /// Offset (bytes) the the beginning of each line, zero-based |
14 | line_offsets: Vec<usize>, |
15 | } |
16 | |
17 | impl 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)] |
49 | mod 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 | } |
92 | |