add is_empty() methods

Author: dwrensha

capnp/src/text.rs

@@ -102,10 +102,15 @@ impl<'a> crate::traits::FromPointerReader<'a> for Reader<'a> {
 }
 
 impl<'a> Reader<'a> {
+    /// The string's length, in bytes.
     pub fn len(&self) -> usize {
         self.as_bytes().len()
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     pub fn as_bytes(self) -> &'a [u8] {
         let Self(d) = self;
         d
@@ -159,10 +164,15 @@ impl<'a> Builder<'a> {
         Builder { bytes, pos }
     }
 
+    /// The string's length, in bytes.
     pub fn len(&self) -> usize {
         self.bytes.len()
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     pub fn as_bytes(self) -> &'a [u8] {
         &self.bytes[..]
     }