optional.h

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*/
 
#ifndef ROUTER_SRC_REST_MRS_SRC_HELPER_OPTIONAL_H_
#define ROUTER_SRC_REST_MRS_SRC_HELPER_OPTIONAL_H_
 
#include <cassert>
 
namespace helper {
 
/**
 * Lightweight implementation of optional.
 *
 * This class was especially created for POD types.
 */
template <typename ValueType>
class Optional {
 public:
  Optional() = default;
  Optional(const ValueType value) : is_set_{true}, v_{value} {}
  Optional(const Optional &other) { *this = other; }
 
  ValueType &operator*() {
    assert(is_set_);
    return v_;
  }
 
  ValueType operator*() const {
    assert(is_set_);
    return v_;
  }
 
  ValueType *operator->() {
    assert(is_set_);
    return &v_;
  }
 
  const ValueType *operator->() const {
    assert(is_set_);
    return &v_;
  }
 
  Optional &operator=(const Optional &value) {
    v_ = value.v_;
    is_set_ = value.is_set_;
 
    return *this;
  }
 
  Optional &operator=(const ValueType value) {
    v_ = value;
    is_set_ = true;
 
    return *this;
  }
 
  void reset() { is_set_ = false; }
 
  bool has_value() const { return is_set_; }
  ValueType value() const {
    assert(is_set_);
    return v_;
  }
 
  operator bool() const { return is_set_; }
 
 private:
  bool is_set_{false};
  ValueType v_{};
};
 
template <class T>
bool operator==(const Optional<T> &lhs, const Optional<T> &rhs) {
  if (lhs.has_value() != rhs.has_value()) return false;
 
  return *lhs == *rhs;
}
 
template <class T>
bool operator==(const T &lhs, const Optional<T> &rhs) {
  if (!rhs.has_value()) return false;
 
  return lhs == *rhs;
}
 
template <class T>
bool operator==(const Optional<T> &lhs, const T rhs) {
  if (!lhs.has_value()) return false;
 
  return *lhs == rhs;
}
 
}  // namespace helper
 
#endif  // ROUTER_SRC_REST_MRS_SRC_HELPER_OPTIONAL_H_