rust-analyzer/crates/libanalysis/src/symbol_index.rs

use libeditor::{FileSymbol, file_symbols};
use libsyntax2::{
    File,
    SyntaxKind::{self, *},
};
use fst::{self, IntoStreamer, Streamer};
use Query;

#[derive(Debug)]
pub(crate) struct FileSymbols {
    symbols: Vec<FileSymbol>,
    map: fst::Map,
}

impl FileSymbols {
    pub(crate) fn new(file: &File) -> FileSymbols {
        let mut symbols = file_symbols(file)
            .into_iter()
            .map(|s| (s.name.as_str().to_lowercase(), s))
            .collect::<Vec<_>>();

        symbols.sort_by(|s1, s2| s1.0.cmp(&s2.0));
        symbols.dedup_by(|s1, s2| s1.0 == s2.0);
        let (names, symbols): (Vec<String>, Vec<FileSymbol>) =
            symbols.into_iter().unzip();

        let map = fst::Map::from_iter(
            names.into_iter().zip(0u64..)
        ).unwrap();
        FileSymbols { symbols, map }
    }
}

impl Query {
    pub(crate) fn process(
        &mut self,
        file: &FileSymbols,
    ) -> Vec<FileSymbol> {
        fn is_type(kind: SyntaxKind) -> bool {
            match kind {
                STRUCT_DEF | ENUM_DEF | TRAIT_DEF | TYPE_DEF => true,
                _ => false,
            }
        }
        let automaton = fst::automaton::Subsequence::new(&self.lowercased);
        let mut stream = file.map.search(automaton).into_stream();
        let mut res = Vec::new();
        while let Some((_, idx)) = stream.next() {
            if self.limit == 0 {
                break;
            }
            let idx = idx as usize;
            let symbol = &file.symbols[idx];
            if self.only_types && !is_type(symbol.kind) {
                continue;
            }
            if self.exact && symbol.name != self.query {
                continue;
            }
            res.push(symbol.clone());
            self.limit -= 1;
        }
        res
    }
}