cache text buf

src/util/change.rs

@@ -0,0 +1,30 @@
+use std::ops::{Deref, DerefMut};
+
+pub struct MutDetect<T> {
+    inner: T,
+    pub changed: bool,
+}
+
+impl<T> Deref for MutDetect<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl<T> DerefMut for MutDetect<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.changed = true;
+        &mut self.inner
+    }
+}
+
+impl<T> From<T> for MutDetect<T> {
+    fn from(inner: T) -> Self {
+        MutDetect {
+            inner,
+            changed: true,
+        }
+    }
+}