From 7e6c0774c428d2d2188c949cc3183a0376f3bc1e Mon Sep 17 00:00:00 2001
From: Hennadii Chernyshchyk <genaloner@gmail.com>
Date: Mon, 2 Dec 2024 01:13:55 +0300
Subject: [PATCH] Use fixed integer encoding for ticks for server events (#371)

---
 CHANGELOG.md                            |  1 +
 src/core/event_registry/server_event.rs | 37 ++++++++++---------------
 src/core/replicon_tick.rs               | 13 ---------
 3 files changed, 15 insertions(+), 36 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a120f778..0f7e8b11 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Split the `ctx` module and move event-related contexts under `core::events_registry::ctx` and replication-related contexts under `core::replication_registry::ctx`.
 - Separate paths from `diagnostics` module by `/` and their parent path now `client/replication` instead of `replication/client`.
 - Provide replication statistics by sum instead of per second and use `usize` for it.
+- Use fixed integer encoding for ticks for server events.
 - Rename `ServerPlugin::change_timeout` into `ServerPlugin::mutations_timeout`.
 - Rename `ServerInitTick` into `ServerChangeTick`.
 - Rename `ReplicatedClient::init_tick` into `ReplicatedClient::change_tick`.
diff --git a/src/core/event_registry/server_event.rs b/src/core/event_registry/server_event.rs
index d47774d8..5686c246 100644
--- a/src/core/event_registry/server_event.rs
+++ b/src/core/event_registry/server_event.rs
@@ -519,7 +519,7 @@ unsafe fn receive<E: Event>(
     for message in client.receive(event_data.channel_id) {
         let mut cursor = Cursor::new(&*message);
         if !event_data.is_independent() {
-            let tick = match DefaultOptions::new().deserialize_from(&mut cursor) {
+            let tick = match bincode::deserialize_from(&mut cursor) {
                 Ok(tick) => tick,
                 Err(e) => {
                     error!(
@@ -671,7 +671,7 @@ unsafe fn serialize_with_padding<E: Event>(
     event: &E,
 ) -> bincode::Result<SerializedMessage> {
     let mut cursor = Cursor::new(Vec::new());
-    let padding = [0u8; RepliconTick::MAX_SERIALIZED_SIZE];
+    let padding = [0; mem::size_of::<RepliconTick>()];
     cursor.write_all(&padding)?;
     event_data.serialize(ctx, event, &mut cursor)?;
     let message = SerializedMessage::Raw(cursor.into_inner());
@@ -685,17 +685,13 @@ enum SerializedMessage {
     ///
     /// `padding | message`
     ///
-    /// The padding length equals max serialized bytes of [`RepliconTick`]. It should be overwritten before sending
+    /// The padding length equals to serialized bytes of [`RepliconTick`]. It should be overwritten before sending
     /// to clients.
     Raw(Vec<u8>),
     /// A message with serialized tick.
     ///
     /// `tick | messsage`
-    Resolved {
-        tick: RepliconTick,
-        tick_size: usize,
-        bytes: Bytes,
-    },
+    Resolved { tick: RepliconTick, bytes: Bytes },
 }
 
 impl SerializedMessage {
@@ -705,32 +701,27 @@ impl SerializedMessage {
         match self {
             // Resolve the raw value into a message with serialized tick.
             Self::Raw(raw) => {
-                let mut bytes = std::mem::take(raw);
-                let tick_size = DefaultOptions::new().serialized_size(&change_tick)? as usize;
-                let padding = RepliconTick::MAX_SERIALIZED_SIZE - tick_size;
-                DefaultOptions::new().serialize_into(&mut bytes[padding..], &change_tick)?;
-                let bytes = Bytes::from(bytes).slice(padding..);
+                let mut bytes = mem::take(raw);
+                bincode::serialize_into(
+                    &mut bytes[..mem::size_of::<RepliconTick>()],
+                    &change_tick,
+                )?;
+                let bytes = Bytes::from(bytes);
                 *self = Self::Resolved {
                     tick: change_tick,
-                    tick_size,
                     bytes: bytes.clone(),
                 };
                 Ok(bytes)
             }
             // Get the already-resolved value or reserialize with a different tick.
-            Self::Resolved {
-                tick,
-                tick_size,
-                bytes,
-            } => {
+            Self::Resolved { tick, bytes } => {
                 if *tick == change_tick {
                     return Ok(bytes.clone());
                 }
 
-                let new_tick_size = DefaultOptions::new().serialized_size(&change_tick)? as usize;
-                let mut new_bytes = Vec::with_capacity(new_tick_size + bytes.len() - *tick_size);
-                DefaultOptions::new().serialize_into(&mut new_bytes, &change_tick)?;
-                new_bytes.extend_from_slice(&bytes[*tick_size..]);
+                let mut new_bytes = Vec::with_capacity(bytes.len());
+                bincode::serialize_into(&mut new_bytes, &change_tick)?;
+                new_bytes.extend_from_slice(&bytes[mem::size_of::<RepliconTick>()..]);
                 Ok(new_bytes.into())
             }
         }
diff --git a/src/core/replicon_tick.rs b/src/core/replicon_tick.rs
index 446e2612..aeb4996b 100644
--- a/src/core/replicon_tick.rs
+++ b/src/core/replicon_tick.rs
@@ -15,9 +15,6 @@ use serde::{Deserialize, Serialize};
 pub struct RepliconTick(u32);
 
 impl RepliconTick {
-    /// Maximum number of bytes required to serialize [`Self`] using default [`bincode::DefaultOptions`].
-    pub const MAX_SERIALIZED_SIZE: usize = 5;
-
     /// Creates a new instance wrapping the given value.
     #[inline]
     pub fn new(value: u32) -> Self {
@@ -82,18 +79,8 @@ impl SubAssign<u32> for RepliconTick {
 
 #[cfg(test)]
 mod tests {
-    use bincode::{DefaultOptions, Options};
-
     use super::*;
 
-    #[test]
-    fn max_serialized_size() {
-        let max = DefaultOptions::new()
-            .serialized_size(&RepliconTick(u32::MAX))
-            .unwrap();
-        assert_eq!(max as usize, RepliconTick::MAX_SERIALIZED_SIZE);
-    }
-
     #[test]
     fn tick_comparsion() {
         assert_eq!(RepliconTick::new(0), RepliconTick::new(0));