FunctionTraits.h

 
#pragma once
#include <exception>
#include <string>
#include <tuple>
#include <type_traits>
 
namespace drogon
{
namespace orm
{
class Result;
class DrogonDbException;
 
namespace internal
{
template <typename>
struct FunctionTraits;
 
template <>
struct FunctionTraits<void (*)()>
{
    using result_type = void;
    template <std::size_t Index>
    using argument = void;
    static const std::size_t arity = 0;
 
    static const bool isSqlCallback = false;
    static const bool isExceptCallback = false;
};
 
// functor,lambda
template <typename Function>
struct FunctionTraits
    : public FunctionTraits<
          decltype(&std::remove_reference<Function>::type::operator())>
{
};
 
template <typename ClassType, typename ReturnType, typename... Arguments>
struct FunctionTraits<ReturnType (ClassType::*)(Arguments...) const>
    : FunctionTraits<ReturnType (*)(Arguments...)>
{
};
 
template <typename ClassType, typename ReturnType, typename... Arguments>
struct FunctionTraits<ReturnType (ClassType::*)(Arguments...)>
    : FunctionTraits<ReturnType (*)(Arguments...)>
{
};
 
template <>
struct FunctionTraits<void (*)(const Result &)>
    : public FunctionTraits<void (*)()>
{
    static const bool isSqlCallback = true;
    static const bool isStepResultCallback = false;
    static const bool isExceptCallback = false;
};
 
template <>
struct FunctionTraits<void (*)(const DrogonDbException &)>
    : public FunctionTraits<void (*)()>
{
    static const bool isExceptCallback = true;
    static const bool isSqlCallback = false;
    static const bool isStepResultCallback = false;
    static const bool isPtr = false;
};
 
template <>
struct FunctionTraits<void (*)(const std::exception_ptr &)>
    : public FunctionTraits<void (*)()>
{
    static const bool isExceptCallback = true;
    static const bool isSqlCallback = false;
    static const bool isStepResultCallback = false;
    static const bool isPtr = true;
};
 
template <typename ReturnType, typename... Arguments>
struct FunctionTraits<ReturnType (*)(bool, Arguments...)>
    : FunctionTraits<ReturnType (*)(Arguments...)>
{
    static const bool isSqlCallback = true;
    static const bool isStepResultCallback = true;
};
 
template <typename ReturnType, typename... Arguments>
struct FunctionTraits<ReturnType (*)(Arguments...)>
{
    using result_type = ReturnType;
 
    template <std::size_t Index>
    using argument =
        typename std::tuple_element<Index, std::tuple<Arguments...>>::type;
 
    static const std::size_t arity = sizeof...(Arguments);
 
    static const bool isSqlCallback = true;
    static const bool isStepResultCallback = true;
    static const bool isExceptCallback = false;
    static const bool isPtr = false;
};
}  // namespace internal
}  // namespace orm
}  // namespace drogon