cs440-assignment3/SharedPtr.hpp

#include <atomic>
#ifndef _POWELLCS440
#include <cassert>
#include <iostream>

#define todo(msg)                                                              \
  std::cerr << msg << std::endl;                                               \
  assert(false);

namespace cs440 {
using counter = std::atomic<std::size_t>;
template <typename T> struct Base {
  template <typename U> friend struct Base;

  T *ptr;
  Base(T *ptr) : ptr{ptr} {}
  template <typename U> Base(Base<U> &ptr) : ptr{ptr.ptr} {}
  template <typename U> Base(Base<U> &&ptr) : ptr{ptr.ptr} {
    ptr.ptr = nullptr;
  }

public:
  virtual T &operator*() { return *ptr; }
  virtual T *operator->() { return ptr; }
  virtual ~Base() = default;
};
template <typename T, typename U> class MyDerived : public Base<T> {
  U *ptr;

public:
  MyDerived(U *ptr) : Base<T>{ptr} { this->ptr = ptr; }
  MyDerived(Base<U> &ptr) : Base<T>{ptr.ptr} { this->ptr = ptr.ptr; }
  U &operator*() { return *ptr; }
  U *operator->() { return ptr; }
  virtual ~MyDerived() { delete this->ptr; }
};
template <typename T> class SharedPtr {
public:
  Base<T> *ptr;
  counter *count;

  SharedPtr() : ptr{nullptr}, count{new std::atomic<std::size_t>{0}} {}
  template <typename U>
  explicit SharedPtr(U *ptr)
      : ptr{static_cast<Base<T> *>(new MyDerived<T, U>{ptr})},
        count{new std::atomic<std::size_t>{
            static_cast<std::size_t>(ptr ? 1 : 0)}} {}
  SharedPtr(const SharedPtr &p) : ptr{p.ptr}, count{p.count} {}
  template <typename U>
  SharedPtr(const SharedPtr<U> &p)
      : ptr(MyDerived<U, T>(const_cast<cs440::Base<U> &>(*p.ptr))),
        count{p.count} {
    (*count)++;
  }
  SharedPtr(SharedPtr &&p) : ptr{p.ptr} { p.ptr = nullptr; }
  template <typename U> SharedPtr(SharedPtr<U> &&p) : ptr{p.ptr} {
    p.ptr = nullptr;
    this->count = p.count;
    p->count = nullptr;
  }
  SharedPtr &operator=(const SharedPtr &ptr) {
    this->ptr = ptr.ptr;
    (*count)++;
    return *this;
  }
  template <typename U> SharedPtr<T> &operator=(const SharedPtr<U> &ptr) {
    this->ptr = ptr.ptr;
    (*count)++;
    return *this;
  }
  SharedPtr &operator=(SharedPtr &&p) {
    ptr = p.ptr;
    p.ptr = nullptr;
    this->count = p.count;
    p->count = nullptr;
    return *this;
  }
  template <typename U> SharedPtr &operator=(SharedPtr<U> &&p) {
    ptr = p.ptr;
    p.ptr = nullptr;
  }
  ~SharedPtr() {
    if (this->count == nullptr) {
      if (this->ptr != nullptr) {
        delete this->ptr;
        this->ptr = nullptr;
      }
      return;
    }
    if (--(*this->count) == 0) {
      delete this->count;
      this->count = nullptr;
      delete this->ptr;
      this->ptr = nullptr;
    }
  }
  void reset() {
    this->ptr = nullptr;
    --(*this->count);
  }
  template <typename U> void reset(U *p) {
    this->ptr = new MyDerived<T, U>{p};
    --(*this->count);
    this->count = new counter{0};
  }
  T *get() const { return this->ptr ? this->ptr->ptr : nullptr; }
  T &operator*() const { return this->ptr->operator*(); }
  T *operator->() const { return this->ptr->operator->(); }
  explicit operator bool() const {
    return this->ptr != nullptr && this->ptr->ptr != nullptr;
  }
};
// template <typename T, typename U>
// SharedPtr<T> static_pointer_cast(const SharedPtr<U> &sp) {
//   todo("");
// }
// template <typename T, typename U>
// SharedPtr<T> dynamic_pointer_cast(const SharedPtr<U> &sp) {
//   todo("");
// }
template <typename T1, typename T2>
bool operator==(const SharedPtr<T1> &lhs, const SharedPtr<T2> &rhs) {
  return lhs.get() == rhs.get();
}
template <typename T>
bool operator==(const SharedPtr<T> &lhs, std::nullptr_t rhs) {

  return lhs.get() == rhs;
}
template <typename T>
bool operator==(std::nullptr_t lhs, const SharedPtr<T> &rhs) {
  return lhs == rhs.get();
}
template <typename T1, typename T2>
bool operator!=(const SharedPtr<T1> &lhs, const SharedPtr<T2> &rhs) {
  return !(lhs == rhs);
}
template <typename T>
bool operator!=(const SharedPtr<T> &lhs, std::nullptr_t rhs) {
  return !(lhs == rhs);
}
template <typename T>
bool operator!=(std::nullptr_t lhs, const SharedPtr<T> &rhs) {
  return !(lhs == rhs);
}
} // namespace cs440
#endif