adding 14

labs/14_smart_memory/main_smart_pointers.cpp

@@ -0,0 +1,208 @@
+#include <iostream>
+#include <cassert>
+#include <string>
+
+// simple homemade smart pointers
+#include "ds_smart_pointers.h"
+
+
+// ====================================================
+// BALLOON: a toy class with dynamically allocated memory
+// ====================================================
+
+#define MAX_NUM_ROPES 10
+
+class Balloon {
+public:
+  // CONSTRUCTOR & DESTRUCTOR
+  Balloon(const std::string& name_) : name(name_) {
+    std::cout << "Balloon constructor " << name << std::endl;
+    num_ropes = 0;
+    ropes = new Balloon*[MAX_NUM_ROPES];
+  }
+  ~Balloon() {
+    std::cout << "Balloon destructor " << name << std::endl;
+    // don't try to destroy attached balloons, just delete array
+    delete [] ropes;
+  }
+
+  // ACCESSORS
+  const std::string& getName() const { return name; }
+  int numRopes() const { return num_ropes; }
+  const Balloon* getRope(int i) const { return ropes[i]; }
+
+  // print the balloons we are attached to
+  void print() { 
+    std::cout << "Balloon " << name << " is connected to: ";
+    for (int i = 0; i < num_ropes; i++) {
+      std::cout << ropes[i]->name << " ";
+    }
+    if (num_ropes == 0) std::cout << "nothing";
+    std::cout << std::endl;
+  }
+  // add a rope connecting this balloon to another
+  void addRope(Balloon* b) { 
+    assert (num_ropes < MAX_NUM_ROPES);
+    ropes[num_ropes] = b;
+    num_ropes++;
+  }
+  // detach a rope connecting this balloon to another
+  void removeRope(Balloon* b) { 
+    for (int i = 0; i < MAX_NUM_ROPES; i++) {
+      if (ropes[i] == b) { ropes[i] = ropes[num_ropes-1]; num_ropes--; break; }
+    }
+  }
+
+private:
+  std::string name;
+  int num_ropes;
+  // a dynamically allocated C-style array of ropes connecting to other Balloons
+  Balloon** ropes; 
+};
+
+
+// ====================================================
+// ====================================================
+
+int main() {
+
+  std::cout << "start of main" << std::endl;
+  
+  // ====================================================
+  // SINGLE OWNER SMART POINTERS
+  // ====================================================
+
+  // first, without smart pointers!
+  Balloon* alice(new Balloon("Hello Kitty"));
+  
+  // now, with our homemade single owner smart pointer
+  dsAutoPtr<Balloon> bob(new Balloon("Spiderman"));
+
+  // both alice & bob work like regular pointers...
+  alice->print();
+  bob->print();
+
+
+
+  //
+  // CHECKPOINT 2A: INSERT NECESSARY EXPLICIT DEALLOCATION
+  //
+
+
+  
+  // ====================================================
+  // SIMPLE SHARED POINTERS
+  // ====================================================
+
+  // first, without smart pointers
+  Balloon* cathy(new Balloon("Buzz Lightyear"));  
+  Balloon* daniel(cathy);
+  Balloon* elaine(new Balloon("Pokemon"));
+  Balloon* fred(elaine);
+  daniel = fred;
+  fred = NULL;
+  elaine = cathy;
+  cathy = NULL;
+  
+
+
+  //
+  // CHECKPOINT 2B: INSERT NECESSARY EXPLICIT DEALLOCATION
+  //
+
+
+
+  daniel = NULL;
+  elaine = NULL;
+  
+
+  // now, with our homemade shared pointer
+  dsSharedPtr<Balloon> cathy2(new Balloon("Buzz Lightyear2"));
+  dsSharedPtr<Balloon> daniel2(cathy2);
+  dsSharedPtr<Balloon> elaine2(new Balloon("Pokemon2"));
+  dsSharedPtr<Balloon> fred2(elaine2);
+  daniel2 = fred2;
+  fred2 = NULL;
+  elaine2 = cathy2;
+  cathy2 = NULL;
+   // NOTE:  no explicit destruction required!
+  daniel2 = NULL;
+  elaine2 = NULL;
+
+
+  // ====================================================
+  // SHARED POINTERS WITH INTERCONNECTED STRUCTURES
+  // ====================================================
+
+  Balloon* georgette(new Balloon("Mr Potato Head"));
+  Balloon* henry(new Balloon("Snoopy"));
+
+  georgette->addRope(henry);
+  henry = new Balloon("Tigger");
+  georgette->addRope(henry);
+  georgette->print();
+  henry->print();
+  
+  Balloon* isabelle(new Balloon("Shrek"));
+  henry->addRope(isabelle);
+  isabelle = new Balloon("Barney the Purple Dinosaur");
+  georgette->addRope(isabelle);
+
+  henry->print();
+  georgette->print();
+  isabelle->print();
+
+
+  //
+  // CHECKPOINT 2C: REWRITE THE ABOVE EXAMPLE TO USE SHARED POINTERS
+  //
+
+
+
+  // ====================================================
+  // CYCLIC STRUCTURES
+  // ====================================================
+
+
+  // FOR CHECKPOINT 3
+
+
+  /*
+  Balloon* jacob(new Balloon("Dora the Explorer"));
+  Balloon* katherine(new Balloon("Kung Fu Panda"));
+  Balloon* larry(new Balloon("Scooby Doo"));
+  Balloon* miranda(new Balloon("SpongeBob SquarePants"));
+  Balloon* nicole(new Balloon("Papa Smurf"));
+
+  jacob->addRope(katherine);
+  katherine->addRope(larry);
+  larry->addRope(jacob);
+  miranda->addRope(jacob);
+  nicole->addRope(miranda);
+  larry->addRope(nicole);
+
+  katherine = NULL;
+  larry = NULL;
+  miranda = NULL;
+  nicole = NULL;
+
+  // jacob points to a cyclic structure!
+
+  // to cleanup this structure:
+  deleteAll(jacob);
+  
+  jacob = NULL;
+  */
+
+
+
+  std::cout << "end of main" << std::endl;
+  return 0;
+
+  //
+  // NOTE: when smart pointers go out of scope, the destructors for
+  //       those objects will be called automatically
+  //
+}
+
+// ====================================================