113 lines
3.8 KiB
Rust
113 lines
3.8 KiB
Rust
/// TextIndex provides conversions between byte offsets (used in the core)
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/// and LSP positions (line, column in UTF-16 units).
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///
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/// Notes:
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/// - `line_starts` stores byte offsets for the start of each line.
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/// - We keep a copy of the text to allow conversions without external dependencies.
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/// - The LSP column is counted in UTF-16 units, excluding the end-of-line `\n`.
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#[derive(Clone, Debug)]
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pub struct TextIndex {
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text: String,
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line_starts: Vec<u32>,
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}
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impl TextIndex {
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/// Builds the index from the file's current textual content.
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pub fn new(text: &str) -> Self {
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let mut line_starts = Vec::with_capacity(128);
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line_starts.push(0);
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for (byte, ch) in text.char_indices() {
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if ch == '\n' {
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// the start of the next line is the byte after the '\n'
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line_starts.push((byte + 1) as u32);
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}
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}
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Self {
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text: text.to_string(),
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line_starts,
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}
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}
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/// Number of lines (0-based; empty lines count).
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#[inline]
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pub fn line_count(&self) -> u32 {
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self.line_starts.len() as u32
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}
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/// Converts a byte offset (within the file) to (line, UTF-16 column) in LSP format.
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///
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/// For offsets exactly at end-of-line, the column will be the line's UTF-16 length.
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pub fn byte_to_lsp(&self, byte: u32) -> (u32, u32) {
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let byte = byte.min(self.text.len() as u32);
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let line = match self.line_starts.binary_search(&byte) {
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Ok(i) => i as u32,
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Err(i) => (i.saturating_sub(1)) as u32,
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};
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let (line_start, line_end) = self.line_bounds(line);
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let rel = byte.saturating_sub(line_start as u32) as usize;
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let slice = &self.text[line_start..line_end];
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let mut utf16_col: u32 = 0;
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for (i, ch) in slice.char_indices() {
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if i >= rel { break; }
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utf16_col += ch.len_utf16() as u32;
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}
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(line, utf16_col)
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}
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/// Converts (line, UTF-16 column) to a byte offset.
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///
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/// - Lines outside the range are clamped to [0, last].
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/// - Columns larger than the line's UTF-16 length return end-of-line.
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pub fn lsp_to_byte(&self, line: u32, utf16_col: u32) -> u32 {
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let line = line.min(self.line_count().saturating_sub(1));
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let (line_start, line_end) = self.line_bounds(line);
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let slice = &self.text[line_start..line_end];
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let mut acc: u32 = 0;
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for (i, ch) in slice.char_indices() {
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if acc >= utf16_col {
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return (line_start + i) as u32;
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}
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acc += ch.len_utf16() as u32;
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}
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// If the target column is after the last character, return end-of-line.
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line_end as u32
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}
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#[inline]
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fn line_bounds(&self, line: u32) -> (usize, usize) {
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let start = *self
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.line_starts
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.get(line as usize)
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.unwrap_or(self.line_starts.last().unwrap());
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let next = self.line_starts.get(line as usize + 1).copied();
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// If there is a next line, `next` points to the byte after the current line's '\n',
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// so the content ends at `next - 1`. Otherwise (last line), the content ends at `text.len()`.
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let end = match next {
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Some(next_start) => next_start.saturating_sub(1),
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None => self.text.len() as u32,
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};
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(start as usize, end as usize)
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}
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}
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#[cfg(test)]
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mod tests_internal {
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use super::*;
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#[test]
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fn line_bounds_basic() {
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let s = "ab\ncd\n";
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let idx = TextIndex::new(s);
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assert_eq!(idx.line_count(), 3);
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// line 0: "ab"
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assert_eq!(idx.line_bounds(0), (0, 2));
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// line 1: "cd"
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assert_eq!(idx.line_bounds(1), (3, 5));
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// line 2: final empty line
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assert_eq!(idx.line_bounds(2), (6, 6));
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}
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}
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