diff --git a/zlib-rs/src/deflate.rs b/zlib-rs/src/deflate.rs
index df0e35d3..9070b6d9 100644
--- a/zlib-rs/src/deflate.rs
+++ b/zlib-rs/src/deflate.rs
@@ -691,7 +691,7 @@ impl<'a> State<'a> {
             "zng_tr_tally: bad literal"
         );
 
-        self.sym_buf.filled().len() == self.sym_end
+        self.sym_buf.len() == self.sym_end
     }
 
     pub(crate) fn tally_dist(&mut self, mut dist: usize, len: usize) -> bool {
@@ -712,7 +712,7 @@ impl<'a> State<'a> {
 
         *self.d_desc.dyn_tree[Self::d_code(dist) as usize].freq_mut() += 1;
 
-        self.sym_buf.filled().len() == self.sym_end
+        self.sym_buf.len() == self.sym_end
     }
 
     fn detect_data_type(dyn_tree: &[Value]) -> DataType {
@@ -790,7 +790,7 @@ impl<'a> State<'a> {
                     "pending_buf overflow"
                 );
 
-                if sx >= self.sym_buf.filled().len() {
+                if sx >= self.sym_buf.len() {
                     break;
                 }
             }
diff --git a/zlib-rs/src/inflate.rs b/zlib-rs/src/inflate.rs
index 5041b4df..64c043c5 100644
--- a/zlib-rs/src/inflate.rs
+++ b/zlib-rs/src/inflate.rs
@@ -857,7 +857,7 @@ impl<'a> State<'a> {
         }
 
         // this is not quite right. not sure when that matters
-        let out = self.writer.remaining() + self.writer.filled().len();
+        let out = self.writer.remaining() + self.writer.len();
         let left = self.writer.remaining();
 
         let copy = out - left;
@@ -1207,7 +1207,7 @@ fn inflate_fast_help(state: &mut State, _start: usize) -> ReturnCode {
                         bit_reader.drop_bits(op as usize);
 
                         // max distance in output
-                        let written = writer.filled().len();
+                        let written = writer.len();
 
                         if dist as usize > written {
                             // copy fropm the window
@@ -1483,7 +1483,7 @@ pub unsafe fn inflate(stream: &mut InflateStream, flush: Flush) -> ReturnCode {
     stream.avail_in = state.bit_reader.bytes_remaining() as u32;
     stream.next_in = state.bit_reader.as_ptr() as *mut u8;
 
-    stream.avail_out = (state.writer.capacity() - state.writer.filled().len()) as u32;
+    stream.avail_out = (state.writer.capacity() - state.writer.len()) as u32;
     stream.next_out = state.writer.as_mut_ptr() as *mut u8;
 
     stream.adler = state.checksum as u64;
diff --git a/zlib-rs/src/read_buf.rs b/zlib-rs/src/read_buf.rs
index ad859dc9..69400dfb 100644
--- a/zlib-rs/src/read_buf.rs
+++ b/zlib-rs/src/read_buf.rs
@@ -75,6 +75,12 @@ impl<'a> ReadBuf<'a> {
         self.buf.len()
     }
 
+    /// Returns the length of the filled part of the buffer
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.filled
+    }
+
     /// Returns true if there are no bytes in this ReadBuf
     #[inline]
     pub fn is_empty(&self) -> bool {
@@ -132,7 +138,7 @@ impl<'a> ReadBuf<'a> {
     /// Returns a mutable reference to the entire buffer, without ensuring that it has been fully
     /// initialized.
     ///
-    /// The elements between 0 and `self.filled().len()` are filled, and those between 0 and
+    /// The elements between 0 and `self.len()` are filled, and those between 0 and
     /// `self.initialized().len()` are initialized (and so can be converted to a `&mut [u8]`).
     ///
     /// The caller of this method must ensure that these invariants are upheld. For example, if the