feat: Impl DekuRead and DekuWrite for ()

src/impls/mod.rs

@@ -2,6 +2,7 @@ mod nonzero;
 mod option;
 mod primitive;
 mod slice;
+mod unit;
 mod vec;
 
 #[cfg(feature = "std")]

src/impls/unit.rs

@@ -0,0 +1,44 @@
+use crate::{DekuError, DekuRead, DekuWrite};
+use bitvec::prelude::*;
+
+impl<Ctx: Copy> DekuRead<'_, Ctx> for () {
+    /// NOP on read
+    fn read(
+        input: &BitSlice<Msb0, u8>,
+        _inner_ctx: Ctx,
+    ) -> Result<(&BitSlice<Msb0, u8>, Self), DekuError>
+    where
+        Self: Sized,
+    {
+        Ok((input, ()))
+    }
+}
+
+impl<Ctx: Copy> DekuWrite<Ctx> for () {
+    /// NOP on write
+    fn write(&self, _output: &mut BitVec<Msb0, u8>, _inner_ctx: Ctx) -> Result<(), DekuError> {
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use hexlit::hex;
+
+    #[test]
+    #[allow(clippy::unit_arg)]
+    #[allow(clippy::unit_cmp)]
+    fn test_unit() {
+        let input = &hex!("FF");
+
+        let bit_slice = input.view_bits::<Msb0>();
+        let (rest, res_read) = <()>::read(bit_slice, ()).unwrap();
+        assert_eq!((), res_read);
+        assert_eq!(bit_slice, rest);
+
+        let mut res_write = bitvec![Msb0, u8;];
+        res_read.write(&mut res_write, ()).unwrap();
+        assert_eq!(0, res_write.len());
+    }
+}