copy-move-semantics.cpp

#include <cstddef>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <string>

using namespace std;

class Foo {
 public:
  Foo() {
    cout << "    "
         << "Foo::Foo() - (Constructor @ " << this << ")\n";

    m_data = new uint8_t[m_length];
    for (uint8_t i = 0; i < m_length; i++) {
      m_data[i] = i;
    }
  }

  Foo(const Foo& other) {
    cout << "    "
         << "Foo::Foo(const Foo&) - (Copy Constructor @ " << this << " <- " << &other << ")\n";

    // Object is being constructed, so we need to allocate m_data
    m_data = new uint8_t[m_length];

    for (int i = 0; i < m_length; i++) {
      m_data[i] = other.m_data[i];
    }
  }

  Foo& operator=(const Foo& other) {
    cout << "    "
         << "Foo& Foo::operator=(const Foo&) - (Copy Assignment @ " << this << " <- " << &other
         << ")\n";

    // Target already exists. No need to allocate m_date
    for (int i = 0; i < m_length; i++) {
      m_data[i] = other.m_data[i];
    }

    return *this;
  }

  Foo(Foo&& other) {
    cout << "    "
         << "Foo::Foo(Foo&&) - (Move Constructor @ " << this << " <- " << &other << ")\n";
    m_data = other.m_data;
    other.m_data = nullptr;  // other is now in an undefined state
  }

  Foo& operator=(Foo&& other) {
    cout << "    "
         << "Foo& Foo::operator=(Foo&&) - (Move Assignment @ " << this << " <- " << &other << ")\n";

    delete m_data;  // release our existing resource
    m_data = other.m_data;
    other.m_data = nullptr;  // other is now in an undefined state

    return *this;
  }

  ~Foo() {
    cout << "    "
         << "Foo::~Foo() - (Destructor @ " << this << ")\n";
    if (m_data) delete m_data;
  }

  string toString() {
    ostringstream out;

    out << "    ";
    if (!m_data) {
      out << "Empty\n";
    } else {
      out << '[';
      for (int i = 0; i < m_length - 1; i++) {
        out << static_cast<int>(m_data[i]) << ", ";
      }
      out << static_cast<int>(m_data[m_length - 1]) << "]\n";
    }

    return out.str();
  }

 private:
  int m_length = 16;
  uint8_t* m_data;
};

int main() {
  cout << endl << "Foo f;\n" << endl;
  Foo f;

  cout << endl << "Foo g = f;\n" << endl;
  Foo g = f;  // Copy

  cout << endl
       << "Foo h;\n"
       << "h = f;\n"
       << endl;
  Foo h;
  h = f;  // Copy assignment

  cout << endl << "Foo j = move(f);\n" << endl;
  Foo j = move(f);  // Move construction

  cout << endl
       << "Foo k;\n"
       << "k = move(g);\n"
       << endl;

  Foo k;
  k = move(g);

  cout << endl << "Content:\n";

  cout << "f:" << f.toString();
  cout << "g:" << g.toString();
  cout << "h:" << h.toString();
  cout << "j:" << j.toString();
  cout << "k:" << k.toString();

  cout << endl << "Leaving main\n";

  return 0;
}