Helper::IsCloser Concept Reference

Checks if the input class can close the needed thing, either as a operator() or using the close() function. More...

#include <management.hpp>

Concept definition

template<typename Class, typename Type>
concept Helper::IsCloser =  requires(Class c, Type t) {
  { c(t) } -> std::same_as<void>;
} || requires(Class c, Type t) {
  { c.close(t) } -> std::same_as<void>;
}

Detailed Description

Checks if the input class can close the needed thing, either as a operator() or using the close() function.

// A example valid class structure.
class CloserWithFunction {
  template <typename>
  static constexpr bool always_false = false;
 
public:
  template <typename T>
  void close(T &var) const noexcept {
    if constexpr (std::is_same_v<std::decay_t<T>, int>) {
      if (static_cast<int>(var) >= 0) ::close(static_cast<int>(var));
    } else if constexpr (std::is_same_v<std::decay_t<T>, FILE*>) {
      if (var != nullptr) fclose(var);
    } else if constexpr (std::is_same_v<std::decay_t<T>, DIR*>) {
      if (var != nullptr) closedir(var);
    } else {
      static_assert(always_false<T>, "Unsupported input type. Closer is only supports int, FILE* and DIR*");
    }
  }
};
 
// --- OR --- //
 
class CloserWithOperator {
  template <typename>
  static constexpr bool always_false = false;
 
public:
  template <typename T>
  void operator()(T &var) const noexcept {
    if constexpr (std::is_same_v<std::decay_t<T>, int>) {
      if (static_cast<int>(var) >= 0) ::close(static_cast<int>(var));
    } else if constexpr (std::is_same_v<std::decay_t<T>, FILE*>) {
      if (var != nullptr) fclose(var);
    } else if constexpr (std::is_same_v<std::decay_t<T>, DIR*>) {
      if (var != nullptr) closedir(var);
    } else {
      static_assert(always_false<T>, "Unsupported input type. Closer is only supports int, FILE* and DIR*");
    }
  }
};
 
// To see how this concept is used, check out Helper::BasicUniqueFD or Helper::BasicUniqueFP.

Template Parameters

Class	Class.
Type	Needed type.

See also

Helper::BasicUniqueFD

Helper::BasicUniqueFP

Note

The return type of the desired close() function/operator() must be void.