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//! `LineIndex` to make a line_offsets, each item is an byte offset (start from 0) of the beginning of the line.
//!
//! For example, the text: `"hello 你好\nworld"`, the line_offsets will store `[0, 13]`.
//!
//! Then `line_col` with a offset just need to find the line index by binary search.
//!
//! Inspired by rust-analyzer's `LineIndex`:
//! <https://github.com/rust-lang/rust/blob/1.67.0/src/tools/rust-analyzer/crates/ide-db/src/line_index.rs>
use alloc::vec::Vec;
#[derive(Clone)]
pub struct LineIndex {
/// Offset (bytes) the the beginning of each line, zero-based
line_offsets: Vec<usize>,
}
impl LineIndex {
pub fn new(text: &str) -> LineIndex {
let mut line_offsets: Vec<usize> = alloc::vec![0];
let mut offset = 0;
for c in text.chars() {
offset += c.len_utf8();
if c == '\n' {
line_offsets.push(offset);
}
}
LineIndex { line_offsets }
}
/// Returns (line, col) of pos.
///
/// The pos is a byte offset, start from 0, e.g. "ab" is 2, "你好" is 6
pub fn line_col(&self, input: &str, pos: usize) -> (usize, usize) {
let line = self.line_offsets.partition_point(|&it| it <= pos) - 1;
let first_offset = self.line_offsets[line];
// Get line str from original input, then we can get column offset
let line_str = &input[first_offset..pos];
let col = line_str.chars().count();
(line + 1, col + 1)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[allow(clippy::zero_prefixed_literal)]
#[test]
fn test_line_index() {
let text = "hello 你好 A🎈C\nworld";
let table = [
(00, 1, 1, 'h'),
(01, 1, 2, 'e'),
(02, 1, 3, 'l'),
(03, 1, 4, 'l'),
(04, 1, 5, 'o'),
(05, 1, 6, ' '),
(06, 1, 7, '你'),
(09, 1, 8, '好'),
(12, 1, 9, ' '),
(13, 1, 10, 'A'),
(14, 1, 11, '🎈'),
(18, 1, 12, 'C'),
(19, 1, 13, '\n'),
(20, 2, 1, 'w'),
(21, 2, 2, 'o'),
(22, 2, 3, 'r'),
(23, 2, 4, 'l'),
(24, 2, 5, 'd'),
];
let index = LineIndex::new(text);
for &(offset, line, col, c) in table.iter() {
let res = index.line_col(text, offset);
assert_eq!(
(res.0, res.1),
(line, col),
"Expected: ({}, {}, {}, {:?})",
offset,
line,
col,
c
);
}
}
}
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