mutex refinements

mission_rust/src/fsrc/datasets/mod.rs

@@ -52,9 +52,9 @@ impl<T: Clone + Default> OwnedDataset<T> {
         }
     }
 
-    pub fn new_default(default_values: T) -> OwnedDataset<T> {
+    pub fn new_init_values(init_values: T) -> OwnedDataset<T> {
         OwnedDataset::<T> {
-            actual_data: default_values,
+            actual_data: init_values,
             mutex: mutex::RawMutex::new(),
         }
     }

mission_rust/src/fsrc/mutex.rs

@@ -1,11 +1,13 @@
+use crate::check_global_threading_available;
+
 use super::osal;
 
-// for now, this is an implementation based on FreeRTOS, where we can preallocate mutexes
-// this allows us to assume that mutexes are valid starting from their creation until end of runtime
-// and so we do not use the global_threading lock
+// TODO we do not discern between a mutex (holding the descriptor) and a clone (pointing to the
+// original descriptor), waisting some memory
 
 pub struct RawMutex {
-    handle: *const core::ffi::c_void
+    handle: Option<*const core::ffi::c_void>,
+    descriptor: [u8; 10], //TODO which size?
 }
 
 pub struct RawMutexGuard {
@@ -14,26 +16,59 @@ pub struct RawMutexGuard {
 
 impl Drop for RawMutexGuard {
     fn drop(&mut self) {
-        //TODO do we need some check here?
-        unsafe{osal::give_mutex(self.handle)};
+        check_global_threading_available!(); // tell me when you reach this one!
+        // We use nullptr as marker for an uninitialized mutex, which we
+        // must not give
+        if self.handle != 0 as *const core::ffi::c_void {
+            unsafe { osal::give_mutex(self.handle) };
+        }
     }
 }
 
 impl RawMutex {
     pub fn new() -> Self {
-        let handle = unsafe {osal::create_mutex()};
-        if handle == 0 as *const core::ffi::c_void {
-            panic!("Could not create mutex")
-        }
         Self {
-            handle: handle
+            handle: None,
+            descriptor: [0; 10],
         }
     }
 
-    pub fn take(&self) -> Result<RawMutexGuard,()> {
-        match unsafe {osal::take_mutex(self.handle)} {
-            1 => Ok(RawMutexGuard { handle: self.handle }),
-            _ => Err(()) //TODO error code
+    fn initialize(&mut self) {
+        // check_global_threading_available!(); we have a token, so this is redundant
+        if self.handle != None {
+            return;
+        }
+        // TODO verify handle size
+        let handle = unsafe { osal::create_mutex() };
+        if handle == 0 as *const core::ffi::c_void {
+            panic!("Could not create mutex")
+        }
+        self.handle = Some(handle);
+    }
+
+    pub fn take(&self) -> Result<RawMutexGuard, ()> {
+        check_global_threading_available!();
+        if let Some(handle) = self.handle {
+            return match unsafe { osal::take_mutex(handle) } {
+                1 => Ok(RawMutexGuard { handle: handle }),
+                _ => Err(()), // Only when timeout expired (we have none) TODO error code
+            };
+        } else {
+            // nullptr makes the guard do nothing
+            Ok(RawMutexGuard {
+                handle: 0 as *const core::ffi::c_void,
+            })
+        }
+    }
+
+    // TODO protect with token
+    pub fn clone(&self) -> Self {
+        let mut_self = self as *const Self as *mut Self; //oh look, a C developer wrote this
+        unsafe { (*mut_self).initialize() }; //TODO this might be safe (we are in init), but does not look very good
+        // At this point self.handle must be valid, initialize would have panicked otherwise
+        Self {
+            handle: self.handle,
+            descriptor: [0; 10],
         }
     }
 
@@ -51,11 +86,3 @@ impl RawMutex {
     //     }
     // }
 }
-
-impl Clone for RawMutex {
-    fn clone(&self) -> Self {
-        Self {
-            handle: self.handle
-        }
-    }
-}