implement memory freeing and block merging

c_os/user/HeapDemo.cc

@@ -20,7 +20,7 @@ void waitForReturn() {
 
     Key key;
     do {
-        kb.key_hit();
+        key = kb.key_hit();
     } while (key.ascii() != '\n');
 }
 
@@ -29,9 +29,46 @@ void heap_demo() {
     /* hier muss Code eingefuegt werden */
     allocator.dump_free_memory();
 
+    // Some objects and forward/backward merging
     MyObj* a = new MyObj(5);
+    // allocator.dump_free_memory();
+    MyObj* b = new MyObj(10);
+    // allocator.dump_free_memory();
+    MyObj* c = new MyObj(15);
+    allocator.dump_free_memory();
+    delete b;
+    // allocator.dump_free_memory();
+    delete a;
+    // allocator.dump_free_memory();
+    delete c;
     allocator.dump_free_memory();
 
-    allocator.alloc(1024 * 1024 - 16);  // should fail as only 1024 * 1024 - (4 + 4) bytes remain
-    allocator.dump_free_memory();
+    // Allocate too whole heap
+    // void* ptr = allocator.alloc(1024 * 1024 - 24);
+    // allocator.dump_free_memory();
+    // allocator.free(ptr);
+    // allocator.dump_free_memory();
+
+    // Allocate too much
+    // allocator.alloc(1024 * 1024);  // should fail as only 1024 * 1024 - Headersize bytes are available
+    // allocator.dump_free_memory();
+
+    // A lot of allocations
+    // MyObj* objs[1024];
+    // for (unsigned int i = 0; i < 1024; ++i) {
+    //     // This tries allocates a lot more than possible
+    //     objs[i] = new MyObj(5);
+    // }
+    // allocator.dump_free_memory();
+    // waitForReturn();
+    // for (unsigned int i = 0; i < 1024; ++i) {
+    //     delete objs[i];
+    // }
+    // allocator.dump_free_memory();
+
+    // Array allocation
+    // MyObj* objs = new MyObj[1024];
+    // allocator.dump_free_memory();
+    // delete[] objs;
+    // allocator.dump_free_memory();
 }