2 files changed, 24 insertions, 17 deletions

diff --git a/libeditor/src/lib.rs b/libeditor/src/lib.rs
index 9da71743f..f77647338 100644
--- a/libeditor/src/lib.rs
+++ b/libeditor/src/lib.rs
@@ -10,6 +10,7 @@ use libsyntax2::{
     SyntaxKind::*,
 };
 pub use libsyntax2::{TextRange, TextUnit, ast};
+pub use self::line_index::{LineIndex, LineCol};
 
 #[derive(Debug)]
 pub struct HighlightedRange {
diff --git a/libeditor/src/line_index.rs b/libeditor/src/line_index.rs
index feb482b32..801726aa5 100644
--- a/libeditor/src/line_index.rs
+++ b/libeditor/src/line_index.rs
@@ -1,6 +1,7 @@
 use superslice::Ext;
-use ::{TextUnit};
+use ::TextUnit;
 
+#[derive(Clone, Debug)]
 pub struct LineIndex {
     newlines: Vec<TextUnit>,
 }
@@ -24,11 +25,16 @@ impl LineIndex {
         LineIndex { newlines }
     }
 
-    pub fn translate(&self, offset: TextUnit) -> LineCol {
+    pub fn line_col(&self, offset: TextUnit) -> LineCol {
         let line = self.newlines.upper_bound(&offset) - 1;
         let line_start_offset = self.newlines[line];
         let col = offset - line_start_offset;
-        return LineCol { line: line as u32, col }
+        return LineCol { line: line as u32, col };
+    }
+
+    pub fn offset(&self, line_col: LineCol) -> TextUnit {
+        //TODO: return Result
+        self.newlines[line_col.line as usize] + line_col.col
     }
 }
 
@@ -36,21 +42,21 @@ impl LineIndex {
 fn test_line_index() {
     let text = "hello\nworld";
     let index = LineIndex::new(text);
-    assert_eq!(index.translate(0.into()), LineCol { line: 0, col: 0.into()});
-    assert_eq!(index.translate(1.into()), LineCol { line: 0, col: 1.into()});
-    assert_eq!(index.translate(5.into()), LineCol { line: 0, col: 5.into()});
-    assert_eq!(index.translate(6.into()), LineCol { line: 1, col: 0.into()});
-    assert_eq!(index.translate(7.into()), LineCol { line: 1, col: 1.into()});
-    assert_eq!(index.translate(8.into()), LineCol { line: 1, col: 2.into()});
-    assert_eq!(index.translate(10.into()), LineCol { line: 1, col: 4.into()});
-    assert_eq!(index.translate(11.into()), LineCol { line: 1, col: 5.into()});
-    assert_eq!(index.translate(12.into()), LineCol { line: 1, col: 6.into()});
+    assert_eq!(index.line_col(0.into()), LineCol { line: 0, col: 0.into() });
+    assert_eq!(index.line_col(1.into()), LineCol { line: 0, col: 1.into() });
+    assert_eq!(index.line_col(5.into()), LineCol { line: 0, col: 5.into() });
+    assert_eq!(index.line_col(6.into()), LineCol { line: 1, col: 0.into() });
+    assert_eq!(index.line_col(7.into()), LineCol { line: 1, col: 1.into() });
+    assert_eq!(index.line_col(8.into()), LineCol { line: 1, col: 2.into() });
+    assert_eq!(index.line_col(10.into()), LineCol { line: 1, col: 4.into() });
+    assert_eq!(index.line_col(11.into()), LineCol { line: 1, col: 5.into() });
+    assert_eq!(index.line_col(12.into()), LineCol { line: 1, col: 6.into() });
 
     let text = "\nhello\nworld";
     let index = LineIndex::new(text);
-    assert_eq!(index.translate(0.into()), LineCol { line: 0, col: 0.into()});
-    assert_eq!(index.translate(1.into()), LineCol { line: 1, col: 0.into()});
-    assert_eq!(index.translate(2.into()), LineCol { line: 1, col: 1.into()});
-    assert_eq!(index.translate(6.into()), LineCol { line: 1, col: 5.into()});
-    assert_eq!(index.translate(7.into()), LineCol { line: 2, col: 0.into()});
+    assert_eq!(index.line_col(0.into()), LineCol { line: 0, col: 0.into() });
+    assert_eq!(index.line_col(1.into()), LineCol { line: 1, col: 0.into() });
+    assert_eq!(index.line_col(2.into()), LineCol { line: 1, col: 1.into() });
+    assert_eq!(index.line_col(6.into()), LineCol { line: 1, col: 5.into() });
+    assert_eq!(index.line_col(7.into()), LineCol { line: 2, col: 0.into() });
 }