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Commit 74bb11d9 authored by Théo Delrieu's avatar Théo Delrieu Committed by Théo DELRIEU
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remove some useless checks, format a bit, added some comments

parent 907484fb
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Showing with 68 additions and 83 deletions
src/json.hpp
View file @ 74bb11d9
......@@ -130,11 +130,17 @@ using conditional_t = typename std::conditional<If, Then, Else>::type;
namespace detail
{
// implementation of 3 C++17 constructs: conjunction, disjunction, negation.
// This is needed to avoid evaluating all the traits, MSVC cannot compile due
// to std::is_constructible<basic_json_t, void> being instantiated
// (void -> back_insert_iterator::value_type)
// this could slow down compilation, since this implementation is taken from the example in cppreference...
// Implementation of 3 C++17 constructs: conjunction, disjunction, negation.
// This is needed to avoid evaluating all the traits in a condition
//
// For example: not std::is_same<void, T>::value and has_value_type<T>::value
// will not compile when T = void (on MSVC at least)
// Whereas conjunction<negation<std::is_same<void, T>>, has_value_type<T>>::value
// will stop evaluating if negation<...>::value == false
//
// Please note that those constructs must be used with caution, since symbols can
// become very long quickly (which can slow down compilation and cause MSVC internal compiler errors)
// Only use it when you have too (see example ahead)
template <class...> struct conjunction : std::true_type {};
template <class B1> struct conjunction<B1> : B1 {};
template <class B1, class... Bn>
......@@ -192,6 +198,8 @@ struct is_compatible_object_type_impl<true, RealType, CompatibleObjectType>
template<class RealType, class CompatibleObjectType>
struct is_compatible_object_type
{
// As noted ahead, we need to stop evaluating traits if CompatibleObjectType = void
// hence the conjunction
static auto constexpr value = is_compatible_object_type_impl<
conjunction<negation<std::is_same<void, CompatibleObjectType>>,
has_mapped_type<CompatibleObjectType>,
......@@ -223,17 +231,14 @@ struct is_compatible_array_type_impl<true, BasicJson, CompatibleArrayType>
template <class BasicJson, class CompatibleArrayType>
struct is_compatible_array_type
{
static auto constexpr value = disjunction<
std::is_same<BasicJson, CompatibleArrayType>,
is_compatible_array_type_impl<
conjunction<negation<
// MSVC has troubles without this
std::is_same<void, CompatibleArrayType>>,
negation<is_compatible_object_type<
typename BasicJson::object_t, CompatibleArrayType>>,
has_value_type<CompatibleArrayType>,
has_iterator<CompatibleArrayType>>::value,
BasicJson, CompatibleArrayType>>::value;
// the check for CompatibleArrayType = void is done in is_compatible_object_type
// but we need the conjunction here as well
static auto constexpr value = is_compatible_array_type_impl<
conjunction<negation<is_compatible_object_type<
typename BasicJson::object_t, CompatibleArrayType>>,
has_value_type<CompatibleArrayType>,
has_iterator<CompatibleArrayType>>::value,
BasicJson, CompatibleArrayType>::value;
};
template <bool, typename, typename>
......@@ -242,11 +247,14 @@ struct is_compatible_integer_type_impl : std::false_type{};
template <typename RealIntegerType, typename CompatibleNumberIntegerType>
struct is_compatible_integer_type_impl<true, RealIntegerType, CompatibleNumberIntegerType>
{
using RealLimits = std::numeric_limits<RealIntegerType>;
using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;
static constexpr auto value =
std::is_constructible<RealIntegerType,
CompatibleNumberIntegerType>::value and
std::numeric_limits<CompatibleNumberIntegerType>::is_integer and
std::numeric_limits<CompatibleNumberIntegerType>::is_signed;
CompatibleLimits::is_integer and
RealLimits::is_signed == CompatibleLimits::is_signed;
};
template <typename RealIntegerType, typename CompatibleNumberIntegerType>
......@@ -257,27 +265,6 @@ struct is_compatible_integer_type
CompatibleNumberIntegerType>::value;
};
template <bool, typename, typename>
struct is_compatible_unsigned_integer_type_impl : std::false_type{};
template <typename RealUnsignedType, typename CompatibleNumberUnsignedType>
struct is_compatible_unsigned_integer_type_impl<true, RealUnsignedType, CompatibleNumberUnsignedType>
{
static constexpr auto value =
std::is_constructible<RealUnsignedType,
CompatibleNumberUnsignedType>::value and
std::numeric_limits<CompatibleNumberUnsignedType>::is_integer and
not std::numeric_limits<CompatibleNumberUnsignedType>::is_signed;
};
template <typename RealUnsignedType, typename CompatibleNumberUnsignedType>
struct is_compatible_unsigned_integer_type
{
static constexpr auto value = is_compatible_unsigned_integer_type_impl<
std::is_arithmetic<CompatibleNumberUnsignedType>::value, RealUnsignedType,
CompatibleNumberUnsignedType>::value;
};
template <typename RealFloat, typename CompatibleFloat>
struct is_compatible_float_type
{
......@@ -298,8 +285,8 @@ struct is_compatible_basic_json_type
is_compatible_float_type<typename BasicJson::number_float_t, T>::value or
is_compatible_integer_type<typename BasicJson::number_integer_t,
T>::value or
is_compatible_unsigned_integer_type<typename BasicJson::number_unsigned_t,
T>::value;
is_compatible_integer_type<typename BasicJson::number_unsigned_t,
T>::value;
};
template <template <typename, typename> class JSONSerializer, typename Json,
......@@ -334,11 +321,14 @@ public:
detect(std::declval<JSONSerializer<T, void>>()))>::value;
};
// those declarations are needed to workaround a MSVC bug related to ADL
// (idea taken from MSVC-Ranges implementation
void to_json();
void from_json();
struct to_json_fn
{
// is it really useful to mark those as constexpr?
template <typename Json, typename T>
constexpr auto operator()(Json &&j, T &&val) const
noexcept(noexcept(to_json(std::forward<Json>(j), std::forward<T>(val))))
......@@ -357,7 +347,7 @@ struct from_json_fn
-> decltype(from_json(std::forward<Json>(j), val), void())
{
return from_json(std::forward<Json>(j), val);
}
}
};
/*!
......@@ -384,18 +374,18 @@ struct DecimalSeparator : std::numpunct<char>
// taken from ranges-v3
// TODO add doc
template <typename T>
struct _static_const
struct static_const
{
static constexpr T value{};
};
template <typename T>
constexpr T _static_const<T>::value;
constexpr T static_const<T>::value;
inline namespace
{
constexpr auto const& to_json = _static_const<detail::to_json_fn>::value;
constexpr auto const& from_json = _static_const<detail::from_json_fn>::value;
constexpr auto const& to_json = static_const<detail::to_json_fn>::value;
constexpr auto const& from_json = static_const<detail::from_json_fn>::value;
}
// default JSONSerializer template argument, doesn't care about template argument
......@@ -1493,14 +1483,16 @@ class basic_json
@since version 1.0.0
*/
template<class CompatibleObjectType, enable_if_t<detail::is_compatible_object_type<object_t, CompatibleObjectType>::value, int> = 0>
basic_json(const CompatibleObjectType& val)
: m_type(value_t::object)
template <class CompatibleObjectType,
enable_if_t<detail::is_compatible_object_type<
object_t, CompatibleObjectType>::value,
int> = 0>
basic_json(const CompatibleObjectType &val) : m_type(value_t::object)
{
using std::begin;
using std::end;
m_value.object = create<object_t>(begin(val), end(val));
assert_invariant();
using std::begin;
using std::end;
m_value.object = create<object_t>(begin(val), end(val));
assert_invariant();
}
/*!
......@@ -1554,16 +1546,12 @@ class basic_json
@since version 1.0.0
*/
template <
class CompatibleArrayType,
enable_if_t<
detail::disjunction<
// MSVC..
std::is_same<uncvref_t<CompatibleArrayType>, basic_json_t>,
detail::is_compatible_array_type<basic_json_t,
CompatibleArrayType>>::value,
int> = 0>
basic_json(const CompatibleArrayType &val) : m_type(value_t::array) {
template <class CompatibleArrayType,
enable_if_t<detail::is_compatible_array_type<
basic_json_t, CompatibleArrayType>::value,
int> = 0>
basic_json(const CompatibleArrayType &val) : m_type(value_t::array)
{
using std::begin;
using std::end;
m_value.array = create<array_t>(begin(val), end(val));
......@@ -1571,19 +1559,18 @@ class basic_json
}
// constructor chosen when JSONSerializer::to_json exists for type T
// first check avoids being chosen instead of move/copy constructor
// constructor chosen when:
// - JSONSerializer::to_json exists for type T
// - T is not a istream, nor convertible to basic_json (float, vectors, etc)
// is_compatible_basic_json_type == not is_user_defined_type
template <
typename T,
enable_if_t<
detail::conjunction<
detail::negation<std::is_same<uncvref_t<T>, basic_json_t>>,
detail::negation<std::is_base_of<std::istream, uncvref_t<T>>>,
detail::negation<detail::is_compatible_basic_json_type<
uncvref_t<T>, basic_json_t>>,
detail::has_to_json<JSONSerializer, basic_json,
uncvref_t<T>>>::value,
int> = 0>
enable_if_t<not std::is_base_of<std::istream, uncvref_t<T>>::value and
not detail::is_compatible_basic_json_type<
uncvref_t<T>, basic_json_t>::value and
detail::has_to_json<JSONSerializer, basic_json,
uncvref_t<T>>::value,
int> = 0>
explicit basic_json(T &&val)
{
JSONSerializer<uncvref_t<T>>::to_json(*this, std::forward<T>(val));
......@@ -1842,7 +1829,7 @@ class basic_json
*/
template <
typename CompatibleNumberUnsignedType,
enable_if_t<detail::is_compatible_unsigned_integer_type<
enable_if_t<detail::is_compatible_integer_type<
number_unsigned_t, CompatibleNumberUnsignedType>::value,
int> = 0>
basic_json(const CompatibleNumberUnsignedType val) noexcept
......@@ -3257,21 +3244,19 @@ class basic_json
@since version 1.0.0
*/
template <typename ValueType,
enable_if_t<
not std::is_pointer<ValueType>::value,
int> = 0>
enable_if_t<not std::is_pointer<ValueType>::value, int> = 0>
auto get() const
-> decltype(this->get_impl(static_cast<ValueType *>(nullptr))) {
-> decltype(this->get_impl(static_cast<ValueType *>(nullptr)))
{
return get_impl(static_cast<ValueType *>(nullptr));
}
template <
typename T,
enable_if_t<detail::conjunction<
detail::negation<detail::is_compatible_basic_json_type<
uncvref_t<T>, basic_json_t>>,
enable_if_t<not detail::is_compatible_basic_json_type<
uncvref_t<T>, basic_json_t>::value and
detail::has_from_json<JSONSerializer, basic_json_t,
uncvref_t<T>>>::value,
uncvref_t<T>>::value,
int> = 0>
auto get() const -> uncvref_t<T>
{
......
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