Support borrowed-slice deserialization from cdr-encoding

Cargo.toml

@@ -62,7 +62,8 @@ bytes = "1.11"
 static_assertions = "1.1"
 thiserror = "2.0.9"
 # cdr-encoding = { path = "../cdr-encoding"}
-cdr-encoding = { version="0.10" }
+# cdr-encoding = { version="0.10" }
+cdr-encoding = { git = "https://github.com/iblnkn/cdr-encoding/", branch="zero-copy-byte-deserialization" }
 cdr-encoding-size = { version="^0.5" }
 futures = "0.3"
 io-extras = "0.18.0"
@@ -118,4 +119,4 @@ termion = "4.0.2"
 
 
 [target.'cfg(target_os = "linux")'.dev-dependencies]
-procfs = "0.17" # for ddsperf
+procfs = "0.17" # for ddsperf

src/dds/adapters.rs

@@ -125,13 +125,17 @@ pub mod no_key {
     ///
     /// `encoding` must be something given by `supported_encodings()`, or
     /// implementation may fail with Err or `panic!()`.
-    fn from_bytes_with<S>(
-      input_bytes: &[u8],
+    ///
+    /// The input slice's lifetime is tied to the deserialization lifetime
+    /// `'de`, so adapters that produce borrowed data (zero-copy) are
+    /// supported.
+    fn from_bytes_with<'de, S>(
+      input_bytes: &'de [u8],
       encoding: RepresentationIdentifier,
       decoder: S,
     ) -> Result<D, S::Error>
     where
-      S: Decode<Self::Decoded>,
+      S: Decode<'de, Self::Decoded>,
     {
       decoder
         .decode_bytes(input_bytes, encoding)
@@ -158,8 +162,9 @@ pub mod no_key {
     /// Type of the default decoder.
     ///
     /// The default decoder needs to be clonable to be usable for async stream
-    /// creation (as it's needed multiple times).
-    type Decoder: Decode<Self::Decoded, Error = Self::Error> + Clone;
+    /// creation (as it's needed multiple times). It must work for any input
+    /// lifetime, hence the higher-ranked `for<'de>` bound.
+    type Decoder: for<'de> Decode<'de, Self::Decoded, Error = Self::Error> + Clone;
 
     /// The default decoder value.
     ///
@@ -168,21 +173,23 @@ pub mod no_key {
     const DECODER: Self::Decoder;
   }
 
-  /// The trait `Decode` defines a decoder object that produced a value of type
-  /// `Dec` from a slice of bytes and a [`RepresentationIdentifier`].
+  /// The trait `Decode` defines a decoder object that produces a value of type
+  /// `Decoded` from a slice of bytes and a [`RepresentationIdentifier`].
+  ///
+  /// Note that `Decoded` maps to associated type `Decoded` in
+  /// `DeserializerAdapter`, not `D`.
   ///
-  /// Note
-  /// that `Decoded` maps to associated type `Decoded` in
-  /// `DeserializerAdapter` , not `D`.
-  pub trait Decode<Decoded> {
+  /// The lifetime `'de` is the deserialization lifetime: the returned
+  /// `Decoded` value may borrow from `input_bytes` for `'de`.
+  pub trait Decode<'de, Decoded> {
     /// The decoding error type returned by [`Self::decode_bytes`].
     type Error: std::error::Error;
 
-    /// Tries to decode the given byte slice to a value of type `D` using the
-    /// given encoding.
+    /// Tries to decode the given byte slice to a value of type `Decoded`
+    /// using the given encoding.
     fn decode_bytes(
       self,
-      input_bytes: &[u8],
+      input_bytes: &'de [u8],
       encoding: RepresentationIdentifier,
     ) -> Result<Decoded, Self::Error>;
   }
@@ -242,13 +249,13 @@ pub mod with_key {
     ///
     /// `encoding` must be something given by `supported_encodings()`, or
     /// implementation may fail with Err or `panic!()`.
-    fn key_from_bytes_with<S>(
-      input_bytes: &[u8],
+    fn key_from_bytes_with<'de, S>(
+      input_bytes: &'de [u8],
       encoding: RepresentationIdentifier,
       decoder: S,
     ) -> Result<D::K, S::Error>
     where
-      S: Decode<Self::Decoded, Self::DecodedKey>,
+      S: Decode<'de, Self::Decoded, Self::DecodedKey>,
     {
       decoder
         .decode_key_bytes(input_bytes, encoding)
@@ -280,8 +287,9 @@ pub mod with_key {
     /// Type of the default decoder.
     ///
     /// The default decoder needs to be clonable to be usable for async stream
-    /// creation (as it's needed multiple times).
-    type Decoder: Decode<Self::Decoded, Self::DecodedKey, Error = Self::Error> + Clone;
+    /// creation (as it's needed multiple times). It must work for any input
+    /// lifetime, hence the higher-ranked `for<'de>` bound.
+    type Decoder: for<'de> Decode<'de, Self::Decoded, Self::DecodedKey, Error = Self::Error> + Clone;
 
     /// The default decoder value.
     ///
@@ -290,15 +298,18 @@ pub mod with_key {
     const DECODER: Self::Decoder;
   }
 
-  /// Decodes a value of type `Dec` from a slice of bytes and a
-  /// [`RepresentationIdentifier`]. Note that `Dec` maps to associated type
-  /// `Decoded` in `DeserializerAdapter` , not `D`.
-  pub trait Decode<Dec, DecKey>: no_key::Decode<Dec> {
-    /// Tries to decode the given byte slice to a value of type `D` using the
-    /// given encoding.
+  /// Decodes a value of type `Dec` (or its key `DecKey`) from a slice of
+  /// bytes and a [`RepresentationIdentifier`]. Note that `Dec` maps to
+  /// associated type `Decoded` in `DeserializerAdapter`, not `D`.
+  ///
+  /// The lifetime `'de` is the deserialization lifetime: the returned key
+  /// may borrow from `input_key_bytes` for `'de`.
+  pub trait Decode<'de, Dec, DecKey>: no_key::Decode<'de, Dec> {
+    /// Tries to decode the given byte slice to a value of type `DecKey`
+    /// using the given encoding.
     fn decode_key_bytes(
       self,
-      input_key_bytes: &[u8],
+      input_key_bytes: &'de [u8],
       encoding: RepresentationIdentifier,
     ) -> Result<DecKey, Self::Error>;
   }

src/dds/no_key/simpledatareader.rs

@@ -64,7 +64,7 @@ where
 
   pub fn try_take_one_with<S>(&self, decoder: S) -> ReadResult<Option<DeserializedCacheChange<D>>>
   where
-    S: Decode<DA::Decoded> + Clone,
+    S: for<'de> Decode<'de, DA::Decoded, Error = DA::Error> + Clone,
   {
     match self
       .keyed_simpledatareader
@@ -101,7 +101,7 @@ where
     decoder: S,
   ) -> impl FusedStream<Item = ReadResult<DeserializedCacheChange<D>>> + 'a
   where
-    S: Decode<DA::Decoded> + Clone + 'a,
+    S: for<'de> Decode<'de, DA::Decoded, Error = DA::Error> + Clone + 'a,
   {
     self
       .keyed_simpledatareader

src/dds/no_key/wrappers.rs

@@ -144,15 +144,15 @@ impl<NoKeyDecode> DecodeWrapper<NoKeyDecode> {
 
 // re-implement no_key::Decode<Decoded> for the wrapper also. Wrapped type
 // already does it for us.
-impl<Decoded, NoKeyDecode> no_key::Decode<Decoded> for DecodeWrapper<NoKeyDecode>
+impl<'de, Decoded, NoKeyDecode> no_key::Decode<'de, Decoded> for DecodeWrapper<NoKeyDecode>
 where
-  NoKeyDecode: no_key::Decode<Decoded>,
+  NoKeyDecode: no_key::Decode<'de, Decoded>,
 {
   type Error = NoKeyDecode::Error;
 
   fn decode_bytes(
     self,
-    input_bytes: &[u8],
+    input_bytes: &'de [u8],
     encoding: RepresentationIdentifier,
   ) -> Result<Decoded, Self::Error> {
     self.no_key.decode_bytes(input_bytes, encoding)
@@ -162,13 +162,13 @@ where
 // implement with_key::Decode<Decoded> for the wrapper.
 // The key has type `()`, so the decoded value is always `()` regardless of the
 // input bytes.
-impl<Decoded, NoKeyDecode> with_key::Decode<Decoded, ()> for DecodeWrapper<NoKeyDecode>
+impl<'de, Decoded, NoKeyDecode> with_key::Decode<'de, Decoded, ()> for DecodeWrapper<NoKeyDecode>
 where
-  NoKeyDecode: no_key::Decode<Decoded>,
+  NoKeyDecode: no_key::Decode<'de, Decoded>,
 {
   fn decode_key_bytes(
     self,
-    _input_key_bytes: &[u8],
+    _input_key_bytes: &'de [u8],
     _encoding: RepresentationIdentifier,
   ) -> Result<(), Self::Error> {
     Ok(())

src/dds/with_key/simpledatareader.rs

@@ -234,7 +234,7 @@ where
     decoder: S,
   ) -> ReadResult<DeserializedCacheChange<D>>
   where
-    S: Decode<DA::Decoded, DA::DecodedKey>,
+    S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error>,
   {
     match cc.data_value {
       DDSData::Data {
@@ -342,7 +342,7 @@ where
   #[allow(clippy::needless_pass_by_value)]
   pub fn try_take_one_with<S>(&self, decoder: S) -> ReadResult<Option<DeserializedCacheChange<D>>>
   where
-    S: Decode<DA::Decoded, DA::DecodedKey> + Clone,
+    S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error> + Clone,
   {
     let is_reliable = matches!(
       self.qos_policy.reliability(),
@@ -414,14 +414,14 @@ where
   where
     DA: DefaultDecoder<D, Decoder = S>,
     DA::Decoder: Clone,
-    S: Decode<DA::Decoded, DA::DecodedKey>,
+    S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error>,
   {
     Self::as_async_stream_with(self, DA::DECODER)
   }
 
   pub fn as_async_stream_with<S>(&self, decoder: S) -> SimpleDataReaderStream<'_, D, S, DA>
   where
-    S: Decode<DA::Decoded, DA::DecodedKey> + Clone,
+    S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error> + Clone,
   {
     SimpleDataReaderStream {
       simple_datareader: self,
@@ -553,7 +553,7 @@ where
 pub struct SimpleDataReaderStream<
   'a,
   D: Keyed + 'static,
-  S: Decode<DA::Decoded, DA::DecodedKey>,
+  S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error>,
   DA: DeserializerAdapter<D> + 'static = CDRDeserializerAdapter<D>,
 > {
   simple_datareader: &'a SimpleDataReader<D, DA>,
@@ -568,15 +568,15 @@ impl<D, S, DA> Unpin for SimpleDataReaderStream<'_, D, S, DA>
 where
   D: Keyed + 'static,
   DA: DeserializerAdapter<D>,
-  S: Decode<DA::Decoded, DA::DecodedKey> + Unpin,
+  S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error> + Unpin,
 {
 }
 
 impl<D, S, DA> Stream for SimpleDataReaderStream<'_, D, S, DA>
 where
   D: Keyed + 'static,
   DA: DeserializerAdapter<D>,
-  S: Decode<DA::Decoded, DA::DecodedKey> + Clone,
+  S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error> + Clone,
 {
   type Item = ReadResult<DeserializedCacheChange<D>>;
 
@@ -633,7 +633,7 @@ impl<D, S, DA> FusedStream for SimpleDataReaderStream<'_, D, S, DA>
 where
   D: Keyed + 'static,
   DA: DeserializerAdapter<D>,
-  S: Decode<DA::Decoded, DA::DecodedKey> + Clone,
+  S: for<'de> Decode<'de, DA::Decoded, DA::DecodedKey, Error = DA::Error> + Clone,
 {
   fn is_terminated(&self) -> bool {
     false // Never terminate. This means it is always valid to call poll_next().

src/serialization/cdr_adapters.rs

@@ -135,11 +135,12 @@ where
   }
 }
 
-/// A default decoder is available for all types that implement
-/// `serde::Deserialize`.
-impl<'de, D> no_key::DefaultDecoder<D> for CDRDeserializerAdapter<D>
+/// A default decoder is available for all owned types that implement
+/// `serde::Deserialize`. Borrowing types use `from_bytes_with` with an
+/// explicit decoder instead.
+impl<D> no_key::DefaultDecoder<D> for CDRDeserializerAdapter<D>
 where
-  D: serde::Deserialize<'de>,
+  D: DeserializeOwned,
 {
   type Decoder = CdrDeserializeDecoder<D>;
   const DECODER: Self::Decoder = CdrDeserializeDecoder(PhantomData);
@@ -157,25 +158,25 @@ where
 /// Decode type based on a `serde::Deserialize` implementation.
 pub struct CdrDeserializeDecoder<D>(PhantomData<D>);
 
-impl<'de, D> no_key::Decode<D> for CdrDeserializeDecoder<D>
+impl<'de, D> no_key::Decode<'de, D> for CdrDeserializeDecoder<D>
 where
   D: serde::Deserialize<'de>,
 {
   type Error = Error;
 
-  fn decode_bytes(self, input_bytes: &[u8], encoding: RepresentationIdentifier) -> Result<D> {
+  fn decode_bytes(self, input_bytes: &'de [u8], encoding: RepresentationIdentifier) -> Result<D> {
     deserialize_from_cdr_with_decoder_and_rep_id(input_bytes, encoding, PhantomData).map(|r| r.0)
   }
 }
 
-impl<Dec, DecKey> with_key::Decode<Dec, DecKey> for CdrDeserializeDecoder<Dec>
+impl<'de, Dec, DecKey> with_key::Decode<'de, Dec, DecKey> for CdrDeserializeDecoder<Dec>
 where
-  Dec: DeserializeOwned,
-  DecKey: DeserializeOwned,
+  Dec: serde::Deserialize<'de>,
+  DecKey: serde::Deserialize<'de>,
 {
   fn decode_key_bytes(
     self,
-    input_key_bytes: &[u8],
+    input_key_bytes: &'de [u8],
     encoding: RepresentationIdentifier,
   ) -> Result<DecKey> {
     deserialize_from_cdr_with_decoder_and_rep_id(input_key_bytes, encoding, PhantomData)
@@ -210,26 +211,27 @@ where
 }
 
 /// Decode type based on a [`serde::de::DeserializeSeed`]-based decoder.
-impl<'de, D, S, SK> no_key::Decode<D> for CdrDeserializeSeedDecoder<S, SK>
+impl<'de, D, S, SK> no_key::Decode<'de, D> for CdrDeserializeSeedDecoder<S, SK>
 where
   S: serde::de::DeserializeSeed<'de, Value = D>,
 {
   type Error = Error;
 
-  fn decode_bytes(self, input_bytes: &[u8], encoding: RepresentationIdentifier) -> Result<D> {
+  fn decode_bytes(self, input_bytes: &'de [u8], encoding: RepresentationIdentifier) -> Result<D> {
     deserialize_from_cdr_with_decoder_and_rep_id(input_bytes, encoding, self.value_seed)
       .map(|r| r.0)
   }
 }
 
-impl<'de, Dec, DecKey, S, SK> with_key::Decode<Dec, DecKey> for CdrDeserializeSeedDecoder<S, SK>
+impl<'de, Dec, DecKey, S, SK> with_key::Decode<'de, Dec, DecKey>
+  for CdrDeserializeSeedDecoder<S, SK>
 where
   S: serde::de::DeserializeSeed<'de, Value = Dec>,
   SK: serde::de::DeserializeSeed<'de, Value = DecKey>,
 {
   fn decode_key_bytes(
     self,
-    input_key_bytes: &[u8],
+    input_key_bytes: &'de [u8],
     encoding: RepresentationIdentifier,
   ) -> Result<DecKey> {
     deserialize_from_cdr_with_decoder_and_rep_id(input_key_bytes, encoding, self.key_seed)
@@ -241,7 +243,7 @@ where
 ///
 /// Returns deserialized object. Byte count is discarded.
 pub fn deserialize_from_cdr_with_rep_id<'de, T>(
-  input_bytes: &[u8],
+  input_bytes: &'de [u8],
   encoding: RepresentationIdentifier,
 ) -> Result<(T, usize)>
 where
@@ -254,7 +256,7 @@ where
 ///
 /// Returns deserialized object and byte count of stream consumed.
 pub fn deserialize_from_cdr_with_decoder_and_rep_id<'de, S>(
-  input_bytes: &[u8],
+  input_bytes: &'de [u8],
   encoding: RepresentationIdentifier,
   decoder: S,
 ) -> Result<(S::Value, usize)>

src/serialization/pl_cdr_adapters.rs

@@ -167,15 +167,15 @@ where
 /// Decode type based on [`PlCdrDeserialize`] implementation.
 pub struct PlCdrDeserializer<D>(PhantomData<D>);
 
-impl<D> no_key::Decode<D> for PlCdrDeserializer<D>
+impl<'de, D> no_key::Decode<'de, D> for PlCdrDeserializer<D>
 where
   D: PlCdrDeserialize,
 {
   type Error = PlCdrDeserializeError;
 
   fn decode_bytes(
     self,
-    input_bytes: &[u8],
+    input_bytes: &'de [u8],
     encoding: RepresentationIdentifier,
   ) -> Result<D, Self::Error> {
     match encoding {
@@ -189,14 +189,14 @@ where
   }
 }
 
-impl<Dec, DecKey> with_key::Decode<Dec, DecKey> for PlCdrDeserializer<Dec>
+impl<'de, Dec, DecKey> with_key::Decode<'de, Dec, DecKey> for PlCdrDeserializer<Dec>
 where
   Dec: PlCdrDeserialize,
   DecKey: PlCdrDeserialize,
 {
   fn decode_key_bytes(
     self,
-    input_bytes: &[u8],
+    input_bytes: &'de [u8],
     encoding: RepresentationIdentifier,
   ) -> Result<DecKey, Self::Error> {
     match encoding {