Avoid materializing strings

crates/libsyntax2/src/yellow/syntax_text.rs

@@ -0,0 +1,101 @@
+use std::{
+    fmt, ops,
+};
+
+use {
+    SyntaxNodeRef, TextRange, TextUnit,
+    algo::walk::preorder,
+    text_utils::{intersect, contains_offset_nonstrict},
+};
+
+#[derive(Clone)]
+pub struct SyntaxText<'a> {
+    node: SyntaxNodeRef<'a>,
+    range: TextRange,
+}
+
+impl<'a> SyntaxText<'a> {
+    pub(crate) fn new(node: SyntaxNodeRef<'a>) -> SyntaxText<'a> {
+        SyntaxText {
+            node,
+            range: node.range()
+        }
+    }
+    pub fn chunks(&self) -> impl Iterator<Item=&'a str> {
+        let range = self.range;
+        preorder(self.node)
+            .filter_map(move |node| {
+                let text = node.leaf_text_ref()?;
+                let range = intersect(range, node.range())?;
+                let range = range - node.range().start();
+                Some(&text[range])
+            })
+    }
+    pub fn to_string(&self) -> String {
+        self.chunks().collect()
+    }
+    pub fn contains(&self, c: char) -> bool {
+        self.chunks().any(|it| it.contains(c))
+    }
+    pub fn find(&self, c: char) -> Option<TextUnit> {
+        let mut acc: TextUnit = 0.into();
+        for chunk in self.chunks() {
+            if let Some(pos) = chunk.find(c) {
+                let pos: TextUnit = (pos as u32).into();
+                return Some(acc + pos);
+            }
+            acc += TextUnit::of_str(chunk);
+        }
+        None
+    }
+    pub fn len(&self) -> TextUnit {
+        self.range.len()
+    }
+    pub fn slice(&self, range: impl SyntaxTextSlice) -> SyntaxText<'a> {
+        let range = range.restrict(self.range)
+            .unwrap_or_else(|| {
+                panic!("invalid slice, range: {:?}, slice: {:?}", self.range, range)
+            });
+        SyntaxText { node: self.node, range }
+    }
+}
+
+impl<'a> fmt::Debug for SyntaxText<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Debug::fmt(&self.to_string(), f)
+    }
+}
+
+impl<'a> fmt::Display for SyntaxText<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&self.to_string(), f)
+    }
+}
+
+pub trait SyntaxTextSlice: fmt::Debug {
+    fn restrict(&self, range: TextRange) -> Option<TextRange>;
+}
+
+impl SyntaxTextSlice for TextRange {
+    fn restrict(&self, range: TextRange) -> Option<TextRange> {
+        intersect(*self, range)
+    }
+}
+
+impl SyntaxTextSlice for ops::RangeTo<TextUnit> {
+    fn restrict(&self, range: TextRange) -> Option<TextRange> {
+        if !contains_offset_nonstrict(range, self.end) {
+            return None;
+        }
+        Some(TextRange::from_to(range.start(), self.end))
+    }
+}
+
+impl SyntaxTextSlice for ops::RangeFrom<TextUnit> {
+    fn restrict(&self, range: TextRange) -> Option<TextRange> {
+        if !contains_offset_nonstrict(range, self.start) {
+            return None;
+        }
+        Some(TextRange::from_to(self.start, range.end()))
+    }
+}