Add struct for unique task id type.

lib/pls/include/pls/internal/scheduling/abstract_task.h

@@ -10,12 +10,23 @@ namespace pls {
     namespace internal {
         namespace scheduling {
             class abstract_task {
+                struct id {
+                    uint32_t id_;
+                    bool auto_generated_;
+
+                    explicit id(uint32_t id, bool auto_generated=true): id_{id}, auto_generated_{auto_generated} {};
+
+                    bool operator==(const abstract_task::id& other) const {
+                        return id_ == other.id_ && auto_generated_ == other.auto_generated_;
+                    }
+                };
+
                 int depth_;
-                int unique_id_;
+                abstract_task::id unique_id_;
                 abstract_task* child_task_;
 
             public:
-                abstract_task(int depth, int unique_id):
+                abstract_task(int depth, abstract_task::id unique_id):
                     depth_{depth},
                     unique_id_{unique_id},
                     child_task_{nullptr} {}
@@ -25,7 +36,7 @@ namespace pls {
                 abstract_task* child() { return child_task_; }
 
                 void set_depth(int depth) { depth_ = depth; }
-                int depth() { return depth_; }
+                int depth() const { return depth_; }
             protected:
                 virtual bool internal_stealing(abstract_task* other_task) = 0;
                 virtual bool split_task(base::spin_lock* lock) = 0;