fix: resolve 7 code review issues from v0.4.x

- Fix KSUDP clutch field reading fuel at offset 59 (KSUDP has no clutch input)
- Replace Notify with watch::channel for reliable shutdown (no missed wakeups)
- Deduplicate read_u16 from parser_pcars into shared binary_utils
- Remove dead Display impl for FeedSource
- Remove unused read_i8 helper from binary_utils
- Change Vec<Instant> to [Instant; 50] in FeedState (eliminate heap alloc)
- Cache rarely-changing strings by driver_id in Telemetry Tool parser

src/binary_utils.rs

@@ -51,12 +51,6 @@ pub fn read_u16(data: &[u8], offset: usize) -> u16 {
     u16::from_le_bytes(buf)
 }
 
-/// Read a signed `i8` from the data at the given offset.
-/// Returns 0 if the offset is out of bounds.
-pub fn read_i8(data: &[u8], offset: usize) -> i8 {
-    data.get(offset).map(|&b| b as i8).unwrap_or(0)
-}
-
 /// Read a little-endian `f32` from the data at the given offset.
 /// Returns 0.0 if the offset is out of bounds (safe fallback for malformed packets).
 pub fn read_f32(data: &[u8], offset: usize) -> f32 {

src/feed_state.rs

@@ -43,7 +43,7 @@ pub struct FeedState {
     pub last_packet_ago_secs: Option<f64>,
     pub start_time: Option<Instant>,
     pub last_packet_time: Option<Instant>,
-    pub packet_timestamps: Vec<Instant>,
+    pub packet_timestamps: [Instant; RING_CAPACITY],
     pub ring_index: usize,
     pub ring_count: usize,
     pub last_frame: Option<TelemetryFrame>,
@@ -62,7 +62,7 @@ impl FeedState {
             last_packet_ago_secs: None,
             start_time: None,
             last_packet_time: None,
-            packet_timestamps: vec![Instant::now(); RING_CAPACITY],
+            packet_timestamps: [Instant::now(); RING_CAPACITY],
             ring_index: 0,
             ring_count: 0,
             last_frame: None,
@@ -85,9 +85,7 @@ impl FeedState {
         self.last_packet_ago_secs = Some(0.0);
 
         if self.ring_count < RING_CAPACITY {
-            if self.ring_count < self.packet_timestamps.len() {
             self.packet_timestamps[self.ring_count] = now;
-            }
             self.ring_count += 1;
             self.ring_index = self.ring_count % RING_CAPACITY;
         } else {

src/main.rs

@@ -120,12 +120,32 @@ fn install_panic_hook() {
     }));
 }
 
+struct CachedStrings {
+    driver_id: u32,
+    driver_name: Option<String>,
+    nationality: Option<String>,
+    car_name: Option<String>,
+    tyre_compound: Option<String>,
+}
+
+impl CachedStrings {
+    fn new() -> Self {
+        Self {
+            driver_id: u32::MAX,
+            driver_name: None,
+            nationality: None,
+            car_name: None,
+            tyre_compound: None,
+        }
+    }
+}
+
 async fn run_feed(
     feed: FeedConfig,
     socket: tokio::net::UdpSocket,
     session_dir: String,
     state: Arc<std::sync::Mutex<FeedState>>,
-    shutdown: Arc<tokio::sync::Notify>,
+    mut shutdown_rx: tokio::sync::watch::Receiver<bool>,
 ) {
     let handshake_target: Option<std::net::SocketAddr> = if feed.needs_handshake {
         let target: std::net::SocketAddr = match format!("{}:{}", game_host(), feed.port).parse() {
@@ -268,6 +288,7 @@ async fn run_feed(
     };
     let mut file = BufWriter::new(file);
     let mut buf = vec![0u8; BUFFER_SIZE];
+    let mut string_cache = CachedStrings::new();
 
     let mut hs_interval: Option<tokio::time::Interval> = handshake_target.map(|_| {
         tokio::time::interval(Duration::from_secs(HANDSHAKE_INTERVAL_SECS))
@@ -295,8 +316,25 @@ async fn run_feed(
                                 _ => None,
                             }
                         } else {
-                            // Telemetry Tool: parse only the first driver
+                            // Telemetry Tool: parse first driver, cache rarely-changing strings
-                            parser_telemetry_tool::parse_first_driver(&buf[..len]).ok()
+                            match parser_telemetry_tool::parse_first_driver_no_strings(&buf[..len]) {
+                                Ok((mut frame, driver_id)) => {
+                                    if driver_id != string_cache.driver_id {
+                                        string_cache.driver_id = driver_id;
+                                        let raw = &buf[..len];
+                                        string_cache.driver_name = Some(binary_utils::read_string(raw, parser_telemetry_tool::STRING_OFFSET_DRIVER_NAME, parser_telemetry_tool::STRING_LEN_DRIVER_NAME));
+                                        string_cache.nationality = Some(binary_utils::read_string(raw, parser_telemetry_tool::STRING_OFFSET_NATIONALITY, parser_telemetry_tool::STRING_LEN_NATIONALITY));
+                                        string_cache.car_name = Some(binary_utils::read_string(raw, parser_telemetry_tool::STRING_OFFSET_CAR_NAME, parser_telemetry_tool::STRING_LEN_CAR_NAME));
+                                        string_cache.tyre_compound = Some(binary_utils::read_string(raw, parser_telemetry_tool::STRING_OFFSET_TYRE_COMPOUND, parser_telemetry_tool::STRING_LEN_TYRE_COMPOUND));
+                                    }
+                                    frame.driver_name = string_cache.driver_name.clone();
+                                    frame.car_name = string_cache.car_name.clone();
+                                    frame.nationality = string_cache.nationality.clone();
+                                    frame.tyre_compound = string_cache.tyre_compound.clone();
+                                    Some(frame)
+                                }
+                                Err(_) => None,
+                            }
                         };
 
                         // Update state in a single brief lock acquisition.
@@ -344,7 +382,7 @@ async fn run_feed(
                     }
                 }
             }
-            _ = shutdown.notified() => {
+            _ = shutdown_rx.changed() => {
                 break;
             }
         }
@@ -391,7 +429,7 @@ async fn main() {
 
     let mut feed_displays: Vec<(FeedDisplayInfo, Arc<std::sync::Mutex<FeedState>>)> = Vec::new();
     let mut feed_tasks: Vec<tokio::task::JoinHandle<()>> = Vec::new();
-    let shutdown = Arc::new(tokio::sync::Notify::new());
+    let (shutdown_tx, shutdown_rx) = tokio::sync::watch::channel(false);
 
     for feed in FEEDS {
         let state = Arc::new(std::sync::Mutex::new(FeedState::new()));
@@ -446,7 +484,7 @@ async fn main() {
         if let Some(socket) = socket_opt {
             let feed_clone = feed.clone();
             let dir = session_dir.clone();
-            let sh = shutdown.clone();
+            let sh = shutdown_rx.clone();
             feed_tasks.push(tokio::spawn(async move {
                 run_feed(feed_clone, socket, dir, state, sh).await;
             }));
@@ -507,7 +545,7 @@ async fn main() {
     }
 
     event_running.store(false, Ordering::Relaxed);
-    shutdown.notify_waiters();
+    let _ = shutdown_tx.send(true);
 
     match tokio::time::timeout(
         Duration::from_secs(3),

src/parser_ksudp.rs

@@ -93,7 +93,7 @@ pub fn parse_rt_car_info(data: &[u8]) -> Result<TelemetryFrame, KsudpParseError>
         // Driver inputs
         throttle: read_f32(data, 51),
         brake: read_f32(data, 55),
-        clutch: read_f32(data, 59),
+        clutch: 0.0, // offset 59 is fuel (0.0–1.0), not clutch; KSUDP has no clutch input
         engine_rpm: read_f32(data, 63),
         steer: read_f32(data, 67),
 

src/parser_pcars.rs

@@ -366,15 +366,6 @@ fn parse_v2_car_physics(data: &[u8]) -> Result<TelemetryFrame, PcarsParseError>
     Ok(frame)
 }
 
-/// Read a u16 at the given offset (little-endian).
-fn read_u16(data: &[u8], offset: usize) -> u16 {
-    let buf: [u8; 2] = data
-        .get(offset..offset + 2)
-        .and_then(|s| s.try_into().ok())
-        .unwrap_or([0u8; 2]);
-    u16::from_le_bytes(buf)
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

src/parser_telemetry_tool.rs

@@ -104,6 +104,7 @@ pub fn parse_packet(data: &[u8]) -> Result<TelemetryToolPacket, TelemetryToolPar
 ///
 /// Avoids allocating a `Vec` for all drivers when only the local player's
 /// telemetry is needed.
+#[allow(dead_code)]
 pub fn parse_first_driver(data: &[u8]) -> Result<TelemetryFrame, TelemetryToolParseError> {
     if data.is_empty() {
         return Err(TelemetryToolParseError::TooShort { actual: 0, needed: 1 });
@@ -125,8 +126,56 @@ pub fn parse_first_driver(data: &[u8]) -> Result<TelemetryFrame, TelemetryToolPa
     parse_driver(&payload[..DRIVER_STRUCT_SIZE])
 }
 
+/// Parse only the first driver, skipping rarely-changing string fields.
+///
+/// Returns a tuple of (frame, raw_driver_id). Strings can be populated
+/// from a cache keyed by `raw_driver_id`.
+pub fn parse_first_driver_no_strings(data: &[u8]) -> Result<(TelemetryFrame, u32), TelemetryToolParseError> {
+    if data.is_empty() {
+        return Err(TelemetryToolParseError::TooShort { actual: 0, needed: 1 });
+    }
+
+    let packet_type = data[0];
+    if packet_type != PACKET_TYPE_TELEMETRY {
+        return Err(TelemetryToolParseError::UnknownPacketType { got: packet_type });
+    }
+
+    let payload = &data[1..];
+    if payload.len() < DRIVER_STRUCT_SIZE {
+        return Err(TelemetryToolParseError::TooShort {
+            actual: data.len(),
+            needed: 1 + DRIVER_STRUCT_SIZE,
+        });
+    }
+
+    let driver_data = &payload[..DRIVER_STRUCT_SIZE];
+    let driver_id = read_u32(driver_data, 0);
+    let mut frame = parse_driver_core(driver_data)?;
+    frame.driver_id = Some(driver_id);
+    Ok((frame, driver_id))
+}
+
+pub const STRING_OFFSET_DRIVER_NAME: usize = 1 + 97;
+pub const STRING_LEN_DRIVER_NAME: usize = 33;
+pub const STRING_OFFSET_NATIONALITY: usize = 1 + 130;
+pub const STRING_LEN_NATIONALITY: usize = 4;
+pub const STRING_OFFSET_CAR_NAME: usize = 1 + 134;
+pub const STRING_LEN_CAR_NAME: usize = 33;
+pub const STRING_OFFSET_TYRE_COMPOUND: usize = 1 + 167;
+pub const STRING_LEN_TYRE_COMPOUND: usize = 10;
+
 /// Parse a single 357-byte driver structure.
 fn parse_driver(data: &[u8]) -> Result<TelemetryFrame, TelemetryToolParseError> {
+    let mut frame = parse_driver_core(data)?;
+    frame.driver_id = Some(read_u32(data, 0));
+    frame.driver_name = Some(read_string(data, 97, 33));
+    frame.nationality = Some(read_string(data, 130, 4));
+    frame.car_name = Some(read_string(data, 134, 33));
+    frame.tyre_compound = Some(read_string(data, 167, 10));
+    Ok(frame)
+}
+
+fn parse_driver_core(data: &[u8]) -> Result<TelemetryFrame, TelemetryToolParseError> {
     // Validation: check test_float at offset 93
     let test_float_val = read_f32(data, 93);
     if (test_float_val - TEST_FLOAT).abs() > 1.0 {
@@ -195,11 +244,6 @@ fn parse_driver(data: &[u8]) -> Result<TelemetryFrame, TelemetryToolParseError>
         tyre_slip: read_f32_4(data, 305),
 
         // Telemetry Tool-specific fields
-        driver_id: Some(read_u32(data, 0)),
-        driver_name: Some(read_string(data, 97, 33)),
-        nationality: Some(read_string(data, 130, 4)),
-        car_name: Some(read_string(data, 134, 33)),
-        tyre_compound: Some(read_string(data, 167, 10)),
         track_position: Some(read_i16(data, 67)),
         leaderboard_position: Some(read_i16(data, 69)),
         is_connected: Some(read_bool(data, 181)),

src/telemetry_frame.rs

@@ -3,8 +3,6 @@
 //! Both the KSUDP (port 9996) and Telemetry Tool (port 10101) parsers produce
 //! `TelemetryFrame` instances from their raw binary data.
 
-use std::fmt;
-
 /// Identifies which feed source produced this frame.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum FeedSource {
@@ -242,13 +240,3 @@ impl TelemetryFrame {
         }
     }
 }
-
-impl fmt::Display for FeedSource {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            FeedSource::Ksudp => write!(f, "KSUDP"),
-            FeedSource::TelemetryTool => write!(f, "Telemetry Tool"),
-            FeedSource::Pcars => write!(f, "PCARS"),
-        }
-    }
-}