fix

src/with_indices.rs

@@ -9,7 +9,8 @@ where
 {
   /// line is a string reference
   pub line: S,
-  last_char_index_to_byte_index: RefCell<(usize, usize)>,
+  last_start_char_index_to_start_byte_index: RefCell<(usize, usize)>,
+  last_end_char_index_to_end_byte_index: RefCell<(usize, usize)>,
   data: PhantomData<&'a S>,
 }
 
@@ -20,7 +21,8 @@ where
   pub fn new(line: S) -> Self {
     Self {
       line,
-      last_char_index_to_byte_index: RefCell::new((0, 0)),
+      last_start_char_index_to_start_byte_index: RefCell::new((0, 0)),
+      last_end_char_index_to_end_byte_index: RefCell::new((0, 0)),
       data: PhantomData,
     }
   }
@@ -39,27 +41,36 @@ where
     let mut start_byte_index = None;
     let mut end_byte_index = None;
 
-    let (last_char_index, mut last_byte_index) =
-      *self.last_char_index_to_byte_index.borrow();
-    let mut char_index = last_char_index;
-    if start_char_index < last_char_index {
-      char_index = 0;
-      last_byte_index = 0;
-    }
+    let (last_start_char_index, last_start_byte_index) =
+      *self.last_start_char_index_to_start_byte_index.borrow();
+    let (last_end_char_index, last_end_byte_index) =
+      *self.last_end_char_index_to_end_byte_index.borrow();
+
+    let (mut char_index, last_byte_index) =
+      if start_char_index >= last_end_char_index {
+        (last_end_char_index, last_end_byte_index)
+      } else if start_char_index >= last_start_char_index {
+        (last_start_char_index, last_start_byte_index)
+      } else {
+        (0, 0)
+      };
+
     for (byte_index, _) in self
       .line
       .byte_slice(last_byte_index..line_len)
       .char_indices()
     {
       if char_index == start_char_index {
         start_byte_index = Some(byte_index + last_byte_index);
+        *self.last_start_char_index_to_start_byte_index.borrow_mut() =
+          (start_char_index, byte_index + last_byte_index);
         if end_char_index == usize::MAX {
           break;
         }
       }
       if char_index == end_char_index {
         end_byte_index = Some(byte_index + last_byte_index);
-        *self.last_char_index_to_byte_index.borrow_mut() =
+        *self.last_end_char_index_to_end_byte_index.borrow_mut() =
           (end_char_index, byte_index + last_byte_index);
         break;
       }