Read header for update check

src/additional_rfactor.rs

@@ -13,11 +13,35 @@ pub const MAX_MAPPED_VEHICLES: usize = 128;
 pub const MAX_MAPPED_IDS: usize = 512;
 
 #[repr(C, packed(4))]
-#[derive(Debug, Copy, Clone)]
-pub struct rF2Telemetry {
+#[derive(Debug, Copy, Clone, Default)]
+pub struct VersionHeader {
     pub version_update_begin: u32,
     pub version_update_end: u32,
     pub bytes_update_hint: i32,
+}
+
+impl VersionHeader {
+    pub const SIZE: usize = mem::size_of::<Self>();
+
+    pub fn check_for_update(&self, other: &Self) -> bool {
+        self.version_update_begin != other.version_update_begin
+            || self.version_update_end != other.version_update_end
+    }
+}
+
+impl From<&[u8]> for VersionHeader {
+    fn from(value: &[u8]) -> Self {
+        debug_assert!(value.len() == Self::SIZE);
+        let fixed_size: [u8; Self::SIZE] = value.try_into().unwrap();
+
+        unsafe { mem::transmute(fixed_size) }
+    }
+}
+
+#[repr(C, packed(4))]
+#[derive(Debug, Copy, Clone)]
+pub struct rF2Telemetry {
+    pub version_header: VersionHeader,
 
     pub num_vehicles: i32,
     pub vehicle_telemetry: [rF2VehicleTelemetry; MAX_MAPPED_VEHICLES],
@@ -43,9 +67,7 @@ impl From<&[u8]> for rF2Telemetry {
 #[repr(C, packed(4))]
 #[derive(Debug, Copy, Clone)]
 pub struct rF2Scoring {
-    pub version_update_begin: u32,
-    pub version_update_end: u32,
-    pub bytes_update_hint: i32,
+    pub version_header: VersionHeader,
 
     pub scoring_info: ScoringInfoV01,
     pub vehicles: [VehicleScoringInfoV01; MAX_MAPPED_VEHICLES],

src/lib.rs

@@ -2,7 +2,7 @@ pub mod additional_rfactor;
 #[allow(warnings)]
 mod rfactor_structs;
 
-use std::{fs::File, marker::PhantomData, path::Path};
+use std::{cell::Cell, fs::File, marker::PhantomData, path::Path};
 
 use additional_rfactor::*;
 pub use additional_rfactor::{rF2Vec3, rF2VehicleTelemetry, rF2Wheel};
@@ -16,6 +16,8 @@ struct ShMReader<T> {
     _file: File,
     shm: Mmap,
 
+    version: Cell<VersionHeader>,
+
     data: PhantomData<T>,
 }
 
@@ -30,17 +32,35 @@ impl<T> ShMReader<T> {
             _file: file,
             shm: mmap,
 
+            version: Cell::new(VersionHeader::default()),
+
             data: PhantomData,
         })
     }
+
+    fn check_version_update(&self) -> bool {
+        let new_version = VersionHeader::from(&self.shm[0..VersionHeader::SIZE]);
+
+        let are_different = self.version.get().check_for_update(&new_version);
+
+        if are_different {
+            self.version.set(new_version);
+        }
+
+        are_different
+    }
 }
 
 impl<'a, T> ShMReader<T>
 where
     T: From<&'a [u8]>,
 {
-    fn read(&'a self) -> T {
-        T::from(&self.shm[0..Self::SIZE])
+    fn read(&'a self) -> Option<T> {
+        if self.check_version_update() {
+            Some(T::from(&self.shm[0..Self::SIZE]))
+        } else {
+            None
+        }
     }
 }
 
@@ -55,8 +75,8 @@ impl TelemetryReader {
         })
     }
 
-    pub fn query_telemetry(&self) -> Vec<rF2VehicleTelemetry> {
-        self.mm_reader.read().vehicles().to_vec()
+    pub fn query_telemetry(&self) -> Option<Vec<rF2VehicleTelemetry>> {
+        self.mm_reader.read().map(|v| v.vehicles().to_vec())
     }
 }
 
@@ -71,9 +91,9 @@ impl ScoringReader {
         })
     }
 
-    pub fn vehicle_scoring(&self) -> (ScoringInfoV01, Vec<VehicleScoringInfoV01>) {
-        let scoring = self.mm_reader.read();
-
-        (scoring.scoring_info, scoring.vehicles().to_vec())
+    pub fn vehicle_scoring(&self) -> Option<(ScoringInfoV01, Vec<VehicleScoringInfoV01>)> {
+        self.mm_reader
+            .read()
+            .map(|s| (s.scoring_info, s.vehicles().to_vec()))
     }
 }