first implementation of queue

c_os/lib/Queue.cc

@@ -0,0 +1,57 @@
+#include "Queue.h"
+#include <cstddef>
+// #include <iostream>
+
+void Queue::enqueue(Chain* item) {
+    // std::cout << "Enqueue " << item->val << std::endl;
+
+    *this->tail = item;        // If queue is empty tail points to head pointer,
+    this->tail = &item->next;  // otherwise to last next pointer
+}
+
+Chain* Queue::dequeue() {
+    if (*this->tail == this->head) {
+        // This should not ever happen as the idle thread exists always
+        // std::cout << "Dequeue called on empty queue." << std::endl;
+        return NULL;
+    }
+
+    Chain* item = this->head;
+    this->head = this->head->next;  // If *item was the only item this->head->next
+                                    // is equal to this->tail
+
+    if (*this->tail == this->head) {
+        // Reset after last element was removed
+        this->head = 0;
+        this->tail = &this->head;
+    }
+
+    // std::cout << "Dequeue " << item->val << std::endl;
+
+    return item;
+}
+
+void Queue::remove(Chain* item) {}
+
+/*
+void Queue::print() const {
+    if (*this->tail == this->head) {
+        // Queue is empty
+        // std::cout << "List is empty!" << std::endl;
+        return;
+    }
+
+    // std::cout << "List: ";
+
+    Chain* current = this->head;
+    // std::cout << current->val << " ";  // At least one element in queue
+
+    while (&current->next != this->tail) {
+        // More than one element in queue
+        current = current->next;
+        // std::cout << current->val << " ";
+    }
+
+    // std::cout << std::endl;
+}
+*/

c_os/lib/Queue.h

@@ -23,22 +23,20 @@
 #include "lib/Chain.h"
 
 class Queue {
-
 private:
-    Queue(const Queue& copy);  // Verhindere Kopieren
+    Queue(const Queue& copy) = delete;  // Verhindere Kopieren
 
 protected:
     Chain* head;
     Chain** tail;
 
 public:
-    Queue() {
+    Queue() : head(0), tail(&head) {}
-        head = 0;
+
-        tail = &head;
-    }
     void enqueue(Chain* item);
     Chain* dequeue();
-    void remove(Chain*);
+    void remove(Chain* item);
+    // void print() const;
 };
 
 #endif