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support construction from other basic_json types

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Before this patch, `basic_json` types with different template arguments
were treated as `CompatibleArrayType`. Which sometimes leads to recursive
calls and stack overflows.

This patch adds a constructor and a `get` overload to deal with
different `basic_json` types.
This commit is contained in:
Théo DELRIEU 2018-02-27 12:11:04 +01:00
parent c22f2d41f3
commit 8711ec6034
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GPG key ID: 7D6E00D1DF01DEAF
5 changed files with 281 additions and 8 deletions
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2
include/nlohmann/detail/meta.hpp
View file

@ -233,7 +233,7 @@ struct is_compatible_complete_type
{
static constexpr bool value =
not std::is_base_of<std::istream, CompatibleCompleteType>::value and
not std::is_same<BasicJsonType, CompatibleCompleteType>::value and
not is_basic_json<CompatibleCompleteType>::value and
not is_basic_json_nested_type<BasicJsonType, CompatibleCompleteType>::value and
has_to_json<BasicJsonType, CompatibleCompleteType>::value;
};

102
include/nlohmann/json.hpp
View file

@ -1207,6 +1207,7 @@ class basic_json
- @a CompatibleType is not derived from `std::istream`,
- @a CompatibleType is not @ref basic_json (to avoid hijacking copy/move
constructors),
- @a CompatibleType is not a different @ref basic_json type (i.e. with different template arguments)
- @a CompatibleType is not a @ref basic_json nested type (e.g.,
@ref json_pointer, @ref iterator, etc ...)
- @ref @ref json_serializer<U> has a
@ -1242,6 +1243,77 @@ class basic_json
assert_invariant();
}
/*!
@brief create a JSON value from an existing one
This is a constructor for existing @ref basic_json types.
It does not hijack copy/move constructors, since the parameter has different template arguments than the current ones.
The constructor tries to convert the internal @ref m_value of the parameter.
@tparam BasicJsonType a type such that:
- @a BasicJsonType is a @ref basic_json type.
- @a BasicJsonType has different template arguments than @ref basic_json_t.
@param[in] val the @ref basic_json value to be converted.
@complexity Usually linear in the size of the passed @a val, also
depending on the implementation of the called `to_json()`
method.
@exceptionsafety Depends on the called constructor. For types directly
supported by the library (i.e., all types for which no `to_json()` function
was provided), strong guarantee holds: if an exception is thrown, there are
no changes to any JSON value.
@since version 3.1.2
*/
template <typename BasicJsonType,
detail::enable_if_t<
detail::is_basic_json<BasicJsonType>::value and not std::is_same<basic_json, BasicJsonType>::value, int> = 0>
basic_json(const BasicJsonType& val)
{
using other_boolean_t = typename BasicJsonType::boolean_t;
using other_number_float_t = typename BasicJsonType::number_float_t;
using other_number_integer_t = typename BasicJsonType::number_integer_t;
using other_number_unsigned_t = typename BasicJsonType::number_unsigned_t;
using other_string_t = typename BasicJsonType::string_t;
using other_object_t = typename BasicJsonType::object_t;
using other_array_t = typename BasicJsonType::array_t;
switch (val.type())
{
case value_t::boolean:
JSONSerializer<other_boolean_t>::to_json(*this, val.template get<other_boolean_t>());
break;
case value_t::number_float:
JSONSerializer<other_number_float_t>::to_json(*this, val.template get<other_number_float_t>());
break;
case value_t::number_integer:
JSONSerializer<other_number_integer_t>::to_json(*this, val.template get<other_number_integer_t>());
break;
case value_t::number_unsigned:
JSONSerializer<other_number_unsigned_t>::to_json(*this, val.template get<other_number_unsigned_t>());
break;
case value_t::string:
JSONSerializer<other_string_t>::to_json(*this, val.template get_ref<const other_string_t&>());
break;
case value_t::object:
JSONSerializer<other_object_t>::to_json(*this, val.template get_ref<const other_object_t&>());
break;
case value_t::array:
JSONSerializer<other_array_t>::to_json(*this, val.template get_ref<const other_array_t&>());
break;
case value_t::null:
*this = nullptr;
break;
case value_t::discarded:
m_type = value_t::discarded;
break;
}
assert_invariant();
}
/*!
@brief create a container (array or object) from an initializer list
@ -2414,6 +2486,31 @@ class basic_json
return *this;
}
/*!
@brief get special-case overload
This overloads converts the current @ref basic_json in a different @ref basic_json type
@tparam BasicJsonType == @ref basic_json
@return a copy of *this, converted into @tparam BasicJsonType
@complexity Depending on the implementation of the called `from_json()`
method.
@since version 3.1.2
*/
template<typename BasicJsonType, detail::enable_if_t<
not std::is_same<BasicJsonType, basic_json>::value and
detail::is_basic_json<BasicJsonType>::value
,
int> = 0>
BasicJsonType get() const
{
return *this;
}
/*!
@brief get a value (explicit)
@ -2455,7 +2552,7 @@ class basic_json
*/
template<typename ValueTypeCV, typename ValueType = detail::uncvref_t<ValueTypeCV>,
detail::enable_if_t <
not std::is_same<basic_json_t, ValueType>::value and
not detail::is_basic_json<ValueType>::value and
detail::has_from_json<basic_json_t, ValueType>::value and
not detail::has_non_default_from_json<basic_json_t, ValueType>::value,
int> = 0>
@ -2721,7 +2818,8 @@ class basic_json
template < typename ValueType, typename std::enable_if <
not std::is_pointer<ValueType>::value and
not std::is_same<ValueType, detail::json_ref<basic_json>>::value and
not std::is_same<ValueType, typename string_t::value_type>::value
not std::is_same<ValueType, typename string_t::value_type>::value and
not detail::is_basic_json<ValueType>::value
#ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
#endif