codec: change Encoder to take &Item (#1746)

Co-authored-by: Markus Westerlind <[email protected]>

tokio-util/src/codec/bytes_codec.rs

@@ -65,8 +65,7 @@ impl Decoder for BytesCodec {
     }
 }
 
-impl Encoder for BytesCodec {
-    type Item = Bytes;
+impl Encoder<Bytes> for BytesCodec {
     type Error = io::Error;
 
     fn encode(&mut self, data: Bytes, buf: &mut BytesMut) -> Result<(), io::Error> {

tokio-util/src/codec/decoder.rs

@@ -1,4 +1,3 @@
-use crate::codec::encoder::Encoder;
 use crate::codec::Framed;
 
 use tokio::io::{AsyncRead, AsyncWrite};
@@ -159,7 +158,7 @@ pub trait Decoder {
     /// [`Framed`]: crate::codec::Framed
     fn framed<T: AsyncRead + AsyncWrite + Sized>(self, io: T) -> Framed<T, Self>
     where
-        Self: Encoder + Sized,
+        Self: Sized,
     {
         Framed::new(io, self)
     }

tokio-util/src/codec/encoder.rs

@@ -5,10 +5,7 @@ use std::io;
 /// [`FramedWrite`].
 ///
 /// [`FramedWrite`]: crate::codec::FramedWrite
-pub trait Encoder {
-    /// The type of items consumed by the `Encoder`
-    type Item;
-
+pub trait Encoder<Item> {
     /// The type of encoding errors.
     ///
     /// [`FramedWrite`] requires `Encoder`s errors to implement `From<io::Error>`
@@ -24,5 +21,5 @@ pub trait Encoder {
     /// will be written out when possible.
     ///
     /// [`FramedWrite`]: crate::codec::FramedWrite
-    fn encode(&mut self, item: Self::Item, dst: &mut BytesMut) -> Result<(), Self::Error>;
+    fn encode(&mut self, item: Item, dst: &mut BytesMut) -> Result<(), Self::Error>;
 }

tokio-util/src/codec/framed.rs

@@ -67,7 +67,6 @@ impl<T, U> ProjectFuse for Fuse<T, U> {
 impl<T, U> Framed<T, U>
 where
     T: AsyncRead + AsyncWrite,
-    U: Decoder + Encoder,
 {
     /// Provides a [`Stream`] and [`Sink`] interface for reading and writing to this
     /// I/O object, using [`Decoder`] and [`Encoder`] to read and write the raw data.
@@ -262,7 +261,7 @@ where
 impl<T, I, U> Sink<I> for Framed<T, U>
 where
     T: AsyncWrite,
-    U: Encoder<Item = I>,
+    U: Encoder<I>,
     U::Error: From<io::Error>,
 {
     type Error = U::Error;
@@ -380,11 +379,10 @@ impl<T, U: Decoder> Decoder for Fuse<T, U> {
     }
 }
 
-impl<T, U: Encoder> Encoder for Fuse<T, U> {
-    type Item = U::Item;
+impl<T, I, U: Encoder<I>> Encoder<I> for Fuse<T, U> {
     type Error = U::Error;
 
-    fn encode(&mut self, item: Self::Item, dst: &mut BytesMut) -> Result<(), Self::Error> {
+    fn encode(&mut self, item: I, dst: &mut BytesMut) -> Result<(), Self::Error> {
         self.codec.encode(item, dst)
     }
 }
@@ -414,8 +412,11 @@ pub struct FramedParts<T, U> {
 }
 
 impl<T, U> FramedParts<T, U> {
-    /// Create a new, default, `FramedParts`.
-    pub fn new(io: T, codec: U) -> FramedParts<T, U> {
+    /// Create a new, default, `FramedParts`
+    pub fn new<I>(io: T, codec: U) -> FramedParts<T, U>
+    where
+        U: Encoder<I>,
+    {
         FramedParts {
             io,
             codec,

tokio-util/src/codec/framed_write.rs

@@ -42,7 +42,6 @@ const BACKPRESSURE_BOUNDARY: usize = INITIAL_CAPACITY;
 impl<T, E> FramedWrite<T, E>
 where
     T: AsyncWrite,
-    E: Encoder,
 {
     /// Creates a new `FramedWrite` with the given `encoder`.
     pub fn new(inner: T, encoder: E) -> FramedWrite<T, E> {
@@ -100,7 +99,7 @@ impl<T, E> FramedWrite<T, E> {
 impl<T, I, E> Sink<I> for FramedWrite<T, E>
 where
     T: AsyncWrite,
-    E: Encoder<Item = I>,
+    E: Encoder<I>,
     E::Error: From<io::Error>,
 {
     type Error = E::Error;
@@ -191,9 +190,9 @@ impl<T> FramedWrite2<T> {
 impl<I, T> Sink<I> for FramedWrite2<T>
 where
     T: ProjectFuse + AsyncWrite,
-    T::Codec: Encoder<Item = I>,
+    T::Codec: Encoder<I>,
 {
-    type Error = <T::Codec as Encoder>::Error;
+    type Error = <T::Codec as Encoder<I>>::Error;
 
     fn poll_ready(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         // If the buffer is already over 8KiB, then attempt to flush it. If after flushing it's

tokio-util/src/codec/length_delimited.rs

@@ -546,12 +546,11 @@ impl Decoder for LengthDelimitedCodec {
     }
 }
 
-impl Encoder for LengthDelimitedCodec {
-    type Item = Bytes;
+impl Encoder<Bytes> for LengthDelimitedCodec {
     type Error = io::Error;
 
     fn encode(&mut self, data: Bytes, dst: &mut BytesMut) -> Result<(), io::Error> {
-        let n = (&data).remaining();
+        let n = data.len();
 
         if n > self.builder.max_frame_len {
             return Err(io::Error::new(

tokio-util/src/codec/lines_codec.rs

@@ -182,11 +182,14 @@ impl Decoder for LinesCodec {
     }
 }
 
-impl Encoder for LinesCodec {
-    type Item = String;
+impl<T> Encoder<T> for LinesCodec
+where
+    T: AsRef<str>,
+{
     type Error = LinesCodecError;
 
-    fn encode(&mut self, line: String, buf: &mut BytesMut) -> Result<(), LinesCodecError> {
+    fn encode(&mut self, line: T, buf: &mut BytesMut) -> Result<(), LinesCodecError> {
+        let line = line.as_ref();
         buf.reserve(line.len() + 1);
         buf.put(line.as_bytes());
         buf.put_u8(b'\n');