[fiber] Add fiber identifier type

src/modm/processing/fiber/functions.hpp

@@ -42,6 +42,13 @@ yield()
 	modm::fiber::Scheduler::instance().yield();
 }
 
+/// Returns the id of the current fiber
+inline modm::fiber::id
+get_id()
+{
+	return modm::fiber::Scheduler::instance().get_id();
+}
+
 /**
  * Yields the current fiber until the time interval has elapsed.
  * This functionality is a convenience wrapper around `modm::Timeout`

src/modm/processing/fiber/scheduler.hpp.in

@@ -20,7 +20,7 @@
 %% endif
 
 // forward declaration
-namespace modm::this_fiber { void yield(); }
+namespace modm::this_fiber { void yield(); modm::fiber::id get_id(); }
 
 namespace modm::fiber
 {
@@ -37,13 +37,20 @@ class Scheduler
 {
 	friend class Task;
 	friend void modm::this_fiber::yield();
+	friend modm::fiber::id modm::this_fiber::get_id();
 	Scheduler(const Scheduler&) = delete;
 	Scheduler& operator=(const Scheduler&) = delete;
 
 protected:
 	Task* last{nullptr};
 	Task* current{nullptr};
 
+	uintptr_t
+	get_id() const
+	{
+		return reinterpret_cast<uintptr_t>(current);
+	}
+
 	void
 	runNext(Task* task)
 	{

src/modm/processing/fiber/task.hpp

@@ -29,6 +29,10 @@ Start
 	Later,	// Manually add the fiber to a scheduler.
 };
 
+/// Identifier of a fiber task.
+/// @ingroup modm_processing_fiber
+using id = uintptr_t;
+
 /**
  * The fiber task connects the callable fiber object with the fiber context and
  * scheduler. It constructs the fiber function on the stack if necessary, and
@@ -74,15 +78,15 @@ class Task
 
 	/// @returns the stack usage as measured by a watermark level.
 	/// @see `modm_context_stack_usage()`.
-	size_t
+	[[nodiscard]] size_t
 	stack_usage() const
 	{
 		return modm_context_stack_usage(&ctx);
 	}
 
 	/// @returns if the bottom word on the stack has been overwritten.
 	/// @see `modm_context_stack_overflow()`.
-	bool
+	[[nodiscard]] bool
 	stack_overflow() const
 	{
 		return modm_context_stack_overflow(&ctx);
@@ -94,7 +98,7 @@ class Task
 	start();
 
 	/// @returns if the fiber is attached to a scheduler.
-	bool
+	[[nodiscard]] bool
 	isRunning() const
 	{
 		return scheduler;