removes serde::Serialize trait bound from Packet::{from_data,populate…

…_packet} (anza-xyz#3636)

As part of anza-xyz#3575
we need to implement bincode (de)serialization without deriving serde
Serialize/Deserialize traits.

Packet::{from_data,populate_packet} methods also only require that the
data to be bincode serializable and do not care about serde either.

Next version of bincode provides the necessary traits to achieve this
functionality:
https://docs.rs/bincode/2.0.0-rc.3/bincode/enc/trait.Encode.html
but that is not released yet.

In order to avoid serde::Serialize trait bound on
Packet::{from_data,populate_packet}, the commit adds a new Encode trait
which only requires implementing bincode serialization.

perf/src/packet.rs

@@ -1,5 +1,5 @@
 //! The `packet` module defines data structures and methods to pull data from the network.
-pub use solana_packet::{Meta, Packet, PacketFlags, PACKET_DATA_SIZE};
+pub use solana_packet::{self, Meta, Packet, PacketFlags, PACKET_DATA_SIZE};
 use {
     crate::{cuda_runtime::PinnedVec, recycler::Recycler},
     bincode::config::Options,
@@ -73,7 +73,7 @@ impl PacketBatch {
         batch
     }
 
-    pub fn new_unpinned_with_recycler_data_and_dests<T: Serialize>(
+    pub fn new_unpinned_with_recycler_data_and_dests<T: solana_packet::Encode>(
         recycler: &PacketBatchRecycler,
         name: &'static str,
         dests_and_data: &[(SocketAddr, T)],
@@ -85,7 +85,7 @@ impl PacketBatch {
 
         for ((addr, data), packet) in dests_and_data.iter().zip(batch.packets.iter_mut()) {
             if !addr.ip().is_unspecified() && addr.port() != 0 {
-                if let Err(e) = Packet::populate_packet(packet, Some(addr), &data) {
+                if let Err(e) = Packet::populate_packet(packet, Some(addr), data) {
                     // TODO: This should never happen. Instead the caller should
                     // break the payload into smaller messages, and here any errors
                     // should be propagated.

sdk/packet/src/lib.rs

@@ -2,10 +2,13 @@
 #![cfg_attr(feature = "frozen-abi", feature(min_specialization))]
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 
-#[cfg(feature = "bincode")]
-use bincode::{Options, Result};
 #[cfg(feature = "frozen-abi")]
 use solana_frozen_abi_macro::AbiExample;
+#[cfg(feature = "bincode")]
+use {
+    bincode::{Options, Result},
+    std::io::Write,
+};
 use {
     bitflags::bitflags,
     std::{
@@ -28,6 +31,18 @@ static_assertions::const_assert_eq!(PACKET_DATA_SIZE, 1232);
 ///   8 bytes is the size of the fragment header
 pub const PACKET_DATA_SIZE: usize = 1280 - 40 - 8;
 
+#[cfg(feature = "bincode")]
+pub trait Encode {
+    fn encode<W: Write>(&self, writer: W) -> Result<()>;
+}
+
+#[cfg(feature = "bincode")]
+impl<T: ?Sized + serde::Serialize> Encode for T {
+    fn encode<W: Write>(&self, writer: W) -> Result<()> {
+        bincode::serialize_into::<W, T>(writer, self)
+    }
+}
+
 bitflags! {
     #[repr(C)]
     #[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
@@ -159,21 +174,21 @@ impl Packet {
     }
 
     #[cfg(feature = "bincode")]
-    pub fn from_data<T: serde::Serialize>(dest: Option<&SocketAddr>, data: T) -> Result<Self> {
+    pub fn from_data<T: Encode>(dest: Option<&SocketAddr>, data: T) -> Result<Self> {
         let mut packet = Self::default();
         Self::populate_packet(&mut packet, dest, &data)?;
         Ok(packet)
     }
 
     #[cfg(feature = "bincode")]
-    pub fn populate_packet<T: serde::Serialize>(
+    pub fn populate_packet<T: Encode>(
         &mut self,
         dest: Option<&SocketAddr>,
         data: &T,
     ) -> Result<()> {
         debug_assert!(!self.meta.discard());
         let mut wr = std::io::Cursor::new(self.buffer_mut());
-        bincode::serialize_into(&mut wr, data)?;
+        <T as Encode>::encode(data, &mut wr)?;
         self.meta.size = wr.position() as usize;
         if let Some(dest) = dest {
             self.meta.set_socket_addr(dest);