use methods that allows better handling of dummies

Assignment_2/FineList.cpp

@@ -14,9 +14,8 @@ class FineSet {
 };
 
 FineSet::FineSet(){
-    first = new Node(); // dummy node;
-    Node* last = new Node();
-    last->data = INT_MAX; // end node;
+    first = Node::Dummy(); // dummy node;
+    Node* last = Node::Dummy();
     first->next = last;
 }
 
@@ -25,20 +24,19 @@ bool FineSet::add(int element) {
     Node* p = this->first;
     Node* c = p->next;
     c->lock();
-    while (c->data < element) {
+    while (c->is_smaller_than(element)) {
         p->unlock();
         p = c;
         c = c->next;
         c->lock();     
     }
 
-    if (c->data == element) {
+    if (c->is_equal(element)) {
         c->unlock();
         p->unlock();
         return false;
     }  else {
-        Node* n = new Node();
-        n->data = element;
+        Node* n = new Node(element);
         n->next = c;
         p->next = n;
         
@@ -54,7 +52,7 @@ bool FineSet::rmv(int element) {
     Node* c = p->next;
     c->lock();
 
-    while (c->data < element) {
+    while (c->is_smaller_than(element)) {
         p->unlock();
         c = c->next;
         c->lock();        
@@ -78,13 +76,13 @@ bool FineSet::ctn(int element) {
     Node* c = p->next;
     c->lock();
 
-    while (c->data < element) {
+    while (c->is_smaller_than(element)) {
         p->unlock();
         c = c->next;
         c->lock();
     }
 
-    if (c->data == element) {            
+    if (c->is_equal(element)) {            
         c->unlock();
         p->unlock();
         return true;

Assignment_2/Node.cpp

@@ -3,12 +3,38 @@
 class Node { 
 public: 
     int data; 
+    bool is_dummy;
     Node* next;
     std::mutex mut; 
     public:
+        Node(int element);
+        static Node* Dummy();
         void lock();
         void unlock();
+        bool is_smaller_than(int n);
+        bool is_equal(int n);
 };
+Node::Node(int element){
+    this->data = element;
+    this->is_dummy = false;
+}
+
+Node* Node::Dummy(){
+    Node* n = new Node(0);
+    n->is_dummy = true;
+    return n;
+}
+
+bool Node::is_smaller_than(int n) {
+    // Everything is smaller than a dummy -> false
+    return  this->data < n && !this->is_dummy;
+}
+
+bool Node::is_equal(int n) {
+    // Dummies are not equal to any number -> false
+    return  this->data == n && !this->is_dummy;
+}
+
 void Node::lock() {
     this->mut.lock();
 }