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Merge pull request #663 from himikof/move-construction

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Support moving from rvalues in std::initializer_list
This commit is contained in:
Niels Lohmann 2017-07-30 20:00:46 +02:00 committed by GitHub
commit 80e95844f6
2 changed files with 293 additions and 54 deletions
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201
src/json.hpp
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@ -575,6 +575,14 @@ struct external_constructor<value_t::string>
j.m_value = s;
j.assert_invariant();
}
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::string_t&& s)
{
j.m_type = value_t::string;
j.m_value = std::move(s);
j.assert_invariant();
}
};
template<>
@ -624,6 +632,14 @@ struct external_constructor<value_t::array>
j.assert_invariant();
}
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::array_t&& arr)
{
j.m_type = value_t::array;
j.m_value = std::move(arr);
j.assert_invariant();
}
template<typename BasicJsonType, typename CompatibleArrayType,
enable_if_t<not std::is_same<CompatibleArrayType,
typename BasicJsonType::array_t>::value,
@ -662,6 +678,14 @@ struct external_constructor<value_t::object>
j.assert_invariant();
}
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::object_t&& obj)
{
j.m_type = value_t::object;
j.m_value = std::move(obj);
j.assert_invariant();
}
template<typename BasicJsonType, typename CompatibleObjectType,
enable_if_t<not std::is_same<CompatibleObjectType,
typename BasicJsonType::object_t>::value, int> = 0>
@ -850,6 +874,12 @@ void to_json(BasicJsonType& j, const CompatibleString& s)
external_constructor<value_t::string>::construct(j, s);
}
template <typename BasicJsonType>
void to_json(BasicJsonType& j, typename BasicJsonType::string_t&& s)
{
external_constructor<value_t::string>::construct(j, std::move(s));
}
template<typename BasicJsonType, typename FloatType,
enable_if_t<std::is_floating_point<FloatType>::value, int> = 0>
void to_json(BasicJsonType& j, FloatType val) noexcept
@ -900,13 +930,25 @@ void to_json(BasicJsonType& j, const CompatibleArrayType& arr)
external_constructor<value_t::array>::construct(j, arr);
}
template <typename BasicJsonType>
void to_json(BasicJsonType& j, typename BasicJsonType::array_t&& arr)
{
external_constructor<value_t::array>::construct(j, std::move(arr));
}
template <
typename BasicJsonType, typename CompatibleObjectType,
enable_if_t<is_compatible_object_type<BasicJsonType, CompatibleObjectType>::value,
int> = 0 >
void to_json(BasicJsonType& j, const CompatibleObjectType& arr)
void to_json(BasicJsonType& j, const CompatibleObjectType& obj)
{
external_constructor<value_t::object>::construct(j, arr);
external_constructor<value_t::object>::construct(j, obj);
}
template <typename BasicJsonType>
void to_json(BasicJsonType& j, typename BasicJsonType::object_t&& obj)
{
external_constructor<value_t::object>::construct(j, std::move(obj));
}
template<typename BasicJsonType, typename T, std::size_t N,
@ -6799,6 +6841,67 @@ class serializer
/// the indentation string
string_t indent_string;
};
template<typename BasicJsonType>
struct json_ref
{
typedef BasicJsonType value_type;
json_ref(value_type&& value)
: owned_value_(std::move(value))
, is_rvalue_(true)
{
value_ref_ = &owned_value_;
}
json_ref(const value_type& value)
: value_ref_(const_cast<value_type*>(&value))
, is_rvalue_(false)
{}
json_ref(std::initializer_list<json_ref> init)
: owned_value_(init)
, is_rvalue_(true)
{
value_ref_ = &owned_value_;
}
template <class... Args>
json_ref(Args... args)
: owned_value_(std::forward<Args>(args)...)
, is_rvalue_(true)
{
value_ref_ = &owned_value_;
}
value_type moved_or_copied() const
{
if (is_rvalue_)
{
return std::move(*value_ref_);
}
else
{
return *value_ref_;
}
}
value_type const& operator*() const
{
return *static_cast<value_type const*>(value_ref_);
}
value_type const* operator->() const
{
return static_cast<value_type const*>(value_ref_);
}
private:
value_type * value_ref_;
mutable value_type owned_value_;
bool is_rvalue_;
};
} // namespace detail
/// namespace to hold default `to_json` / `from_json` functions
@ -7297,6 +7400,7 @@ class basic_json
template<typename T, typename SFINAE>
using json_serializer = JSONSerializer<T, SFINAE>;
using initializer_list_t = std::initializer_list<detail::json_ref<basic_json>>;
////////////////
// exceptions //
@ -8025,18 +8129,36 @@ class basic_json
string = create<string_t>(value);
}
/// constructor for rvalue strings
json_value(string_t&& value)
{
string = create<string_t>(std::move(value));
}
/// constructor for objects
json_value(const object_t& value)
{
object = create<object_t>(value);
}
/// constructor for rvalue objects
json_value(object_t&& value)
{
object = create<object_t>(std::move(value));
}
/// constructor for arrays
json_value(const array_t& value)
{
array = create<array_t>(value);
}
/// constructor for rvalue arrays
json_value(array_t&& value)
{
array = create<array_t>(std::move(value));
}
void destroy(value_t t)
{
switch (t)
@ -8310,10 +8432,10 @@ class basic_json
With the rules described above, the following JSON values cannot be
expressed by an initializer list:
- the empty array (`[]`): use @ref array(std::initializer_list<basic_json>)
- the empty array (`[]`): use @ref array(initializer_list_t)
with an empty initializer list in this case
- arrays whose elements satisfy rule 2: use @ref
array(std::initializer_list<basic_json>) with the same initializer list
array(initializer_list_t) with the same initializer list
in this case
@note When used without parentheses around an empty initializer list, @ref
@ -8325,8 +8447,8 @@ class basic_json
@param[in] type_deduction internal parameter; when set to `true`, the type
of the JSON value is deducted from the initializer list @a init; when set
to `false`, the type provided via @a manual_type is forced. This mode is
used by the functions @ref array(std::initializer_list<basic_json>) and
@ref object(std::initializer_list<basic_json>).
used by the functions @ref array(initializer_list_t) and
@ref object(initializer_list_t).
@param[in] manual_type internal parameter; when @a type_deduction is set
to `false`, the created JSON value will use the provided type (only @ref
@ -8337,7 +8459,7 @@ class basic_json
`value_t::object`, but @a init contains an element which is not a pair
whose first element is a string. In this case, the constructor could not
create an object. If @a type_deduction would have be `true`, an array
would have been created. See @ref object(std::initializer_list<basic_json>)
would have been created. See @ref object(initializer_list_t)
for an example.
@complexity Linear in the size of the initializer list @a init.
@ -8345,23 +8467,23 @@ class basic_json
@liveexample{The example below shows how JSON values are created from
initializer lists.,basic_json__list_init_t}
@sa @ref array(std::initializer_list<basic_json>) -- create a JSON array
@sa @ref array(initializer_list_t) -- create a JSON array
value from an initializer list
@sa @ref object(std::initializer_list<basic_json>) -- create a JSON object
@sa @ref object(initializer_list_t) -- create a JSON object
value from an initializer list
@since version 1.0.0
*/
basic_json(std::initializer_list<basic_json> init,
basic_json(initializer_list_t init,
bool type_deduction = true,
value_t manual_type = value_t::array)
{
// check if each element is an array with two elements whose first
// element is a string
bool is_an_object = std::all_of(init.begin(), init.end(),
[](const basic_json & element)
[](const detail::json_ref<basic_json>& element_ref)
{
return (element.is_array() and element.size() == 2 and element[0].is_string());
return (element_ref->is_array() and element_ref->size() == 2 and (*element_ref)[0].is_string());
});
// adjust type if type deduction is not wanted
@ -8386,16 +8508,19 @@ class basic_json
m_type = value_t::object;
m_value = value_t::object;
std::for_each(init.begin(), init.end(), [this](const basic_json & element)
std::for_each(init.begin(), init.end(), [this](const detail::json_ref<basic_json>& element_ref)
{
m_value.object->emplace(*(element[0].m_value.string), element[1]);
basic_json element = element_ref.moved_or_copied();
m_value.object->emplace(
std::move(*((*element.m_value.array)[0].m_value.string)),
std::move((*element.m_value.array)[1]));
});
}
else
{
// the initializer list describes an array -> create array
m_type = value_t::array;
m_value.array = create<array_t>(init);
m_value.array = create<array_t>(init.begin(), init.end());
}
assert_invariant();
@ -8410,7 +8535,7 @@ class basic_json
@note This function is only needed to express two edge cases that cannot
be realized with the initializer list constructor (@ref
basic_json(std::initializer_list<basic_json>, bool, value_t)). These cases
basic_json(initializer_list_t, bool, value_t)). These cases
are:
1. creating an array whose elements are all pairs whose first element is a
string -- in this case, the initializer list constructor would create an
@ -8428,15 +8553,14 @@ class basic_json
@liveexample{The following code shows an example for the `array`
function.,array}
@sa @ref basic_json(std::initializer_list<basic_json>, bool, value_t) --
@sa @ref basic_json(initializer_list_t, bool, value_t) --
create a JSON value from an initializer list
@sa @ref object(std::initializer_list<basic_json>) -- create a JSON object
@sa @ref object(initializer_list_t) -- create a JSON object
value from an initializer list
@since version 1.0.0
*/
static basic_json array(std::initializer_list<basic_json> init =
std::initializer_list<basic_json>())
static basic_json array(initializer_list_t init = {})
{
return basic_json(init, false, value_t::array);
}
@ -8449,10 +8573,10 @@ class basic_json
the initializer list is empty, the empty object `{}` is created.
@note This function is only added for symmetry reasons. In contrast to the
related function @ref array(std::initializer_list<basic_json>), there are
related function @ref array(initializer_list_t), there are
no cases which can only be expressed by this function. That is, any
initializer list @a init can also be passed to the initializer list
constructor @ref basic_json(std::initializer_list<basic_json>, bool, value_t).
constructor @ref basic_json(initializer_list_t, bool, value_t).
@param[in] init initializer list to create an object from (optional)
@ -8460,7 +8584,7 @@ class basic_json
@throw type_error.301 if @a init is not a list of pairs whose first
elements are strings. In this case, no object can be created. When such a
value is passed to @ref basic_json(std::initializer_list<basic_json>, bool, value_t),
value is passed to @ref basic_json(initializer_list_t, bool, value_t),
an array would have been created from the passed initializer list @a init.
See example below.
@ -8469,15 +8593,14 @@ class basic_json
@liveexample{The following code shows an example for the `object`
function.,object}
@sa @ref basic_json(std::initializer_list<basic_json>, bool, value_t) --
@sa @ref basic_json(initializer_list_t, bool, value_t) --
create a JSON value from an initializer list
@sa @ref array(std::initializer_list<basic_json>) -- create a JSON array
@sa @ref array(initializer_list_t) -- create a JSON array
value from an initializer list
@since version 1.0.0
*/
static basic_json object(std::initializer_list<basic_json> init =
std::initializer_list<basic_json>())
static basic_json object(initializer_list_t init = {})
{
return basic_json(init, false, value_t::object);
}
@ -8650,6 +8773,11 @@ class basic_json
// other constructors and destructor //
///////////////////////////////////////
basic_json(const detail::json_ref<basic_json>& ref)
: basic_json(ref.moved_or_copied())
{
}
/*!
@brief copy constructor
@ -11450,7 +11578,7 @@ class basic_json
@brief add an object to an array
@copydoc push_back(basic_json&&)
*/
reference operator+=(basic_json&& val)
reference operator+=(basic_json && val)
{
push_back(std::move(val));
return *this;
@ -11565,12 +11693,13 @@ class basic_json
@liveexample{The example shows how initializer lists are treated as
objects when possible.,push_back__initializer_list}
*/
void push_back(std::initializer_list<basic_json> init)
void push_back(initializer_list_t init)
{
if (is_object() and init.size() == 2 and init.begin()->is_string())
if (is_object() and init.size() == 2 and (*init.begin())->is_string())
{
const string_t key = *init.begin();
push_back(typename object_t::value_type(key, *(init.begin() + 1)));
basic_json&& key = init.begin()->moved_or_copied();
push_back(typename object_t::value_type(
std::move(key.get_ref<string_t&>()), (init.begin() + 1)->moved_or_copied()));
}
else
{
@ -11580,9 +11709,9 @@ class basic_json
/*!
@brief add an object to an object
@copydoc push_back(std::initializer_list<basic_json>)
@copydoc push_back(initializer_list_t)
*/
reference operator+=(std::initializer_list<basic_json> init)
reference operator+=(initializer_list_t init)
{
push_back(init);
return *this;
@ -11867,7 +11996,7 @@ class basic_json
@since version 1.0.0
*/
iterator insert(const_iterator pos, std::initializer_list<basic_json> ilist)
iterator insert(const_iterator pos, initializer_list_t ilist)
{
// insert only works for arrays
if (JSON_UNLIKELY(not is_array()))
@ -11883,7 +12012,7 @@ class basic_json
// insert to array and return iterator
iterator result(this);
result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, ilist);
result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, ilist.begin(), ilist.end());
return result;
}

146
test/src/unit-constructor1.cpp
View file

@ -842,8 +842,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l;
json j(l);
json j(json::initializer_list_t {});
CHECK(j.type() == json::value_t::object);
}
@ -860,8 +859,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {json(json::array_t())};
json j(l);
json j(json::initializer_list_t {json(json::array_t())});
CHECK(j.type() == json::value_t::array);
}
@ -876,8 +874,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {json(json::object_t())};
json j(l);
json j(json::initializer_list_t {json(json::object_t())});
CHECK(j.type() == json::value_t::array);
}
@ -892,8 +889,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {json("Hello world")};
json j(l);
json j(json::initializer_list_t {json("Hello world")});
CHECK(j.type() == json::value_t::array);
}
@ -908,8 +904,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {json(true)};
json j(l);
json j(json::initializer_list_t {json(true)});
CHECK(j.type() == json::value_t::array);
}
@ -924,8 +919,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {json(1)};
json j(l);
json j(json::initializer_list_t {json(1)});
CHECK(j.type() == json::value_t::array);
}
@ -940,8 +934,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {json(1u)};
json j(l);
json j(json::initializer_list_t {json(1u)});
CHECK(j.type() == json::value_t::array);
}
@ -956,8 +949,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {json(42.23)};
json j(l);
json j(json::initializer_list_t {json(42.23)});
CHECK(j.type() == json::value_t::array);
}
@ -973,8 +965,7 @@ TEST_CASE("constructors")
{
SECTION("explicit")
{
std::initializer_list<json> l = {1, 1u, 42.23, true, nullptr, json::object_t(), json::array_t()};
json j(l);
json j(json::initializer_list_t {1, 1u, 42.23, true, nullptr, json::object_t(), json::array_t()});
CHECK(j.type() == json::value_t::array);
}
@ -1034,6 +1025,125 @@ TEST_CASE("constructors")
CHECK(j.type() == json::value_t::array);
}
}
SECTION("move from initializer_list")
{
SECTION("string")
{
// This should break through any short string optimization in std::string
std::string source(1024, '!');
const char* source_addr = source.data();
SECTION("constructor with implicit types (array)")
{
json j = {std::move(source)};
CHECK(j[0].get_ref<std::string const&>().data() == source_addr);
}
SECTION("constructor with implicit types (object)")
{
json j = {{"key", std::move(source)}};
CHECK(j["key"].get_ref<std::string const&>().data() == source_addr);
}
SECTION("constructor with implicit types (object key)")
{
json j = {{std::move(source), 42}};
CHECK(j.get_ref<json::object_t&>().begin()->first.data() == source_addr);
}
}
SECTION("array")
{
json::array_t source = {1, 2, 3};
const json* source_addr = source.data();
SECTION("constructor with implicit types (array)")
{
json j {std::move(source)};
CHECK(j[0].get_ref<json::array_t const&>().data() == source_addr);
}
SECTION("constructor with implicit types (object)")
{
json j {{"key", std::move(source)}};
CHECK(j["key"].get_ref<json::array_t const&>().data() == source_addr);
}
SECTION("assignment with implicit types (array)")
{
json j = {std::move(source)};
CHECK(j[0].get_ref<json::array_t const&>().data() == source_addr);
}
SECTION("assignment with implicit types (object)")
{
json j = {{"key", std::move(source)}};
CHECK(j["key"].get_ref<json::array_t const&>().data() == source_addr);
}
}
SECTION("object")
{
json::object_t source = {{"hello", "world"}};
const json* source_addr = &source.at("hello");
SECTION("constructor with implicit types (array)")
{
json j {std::move(source)};
CHECK(&(j[0].get_ref<json::object_t const&>().at("hello")) == source_addr);
}
SECTION("constructor with implicit types (object)")
{
json j {{"key", std::move(source)}};
CHECK(&(j["key"].get_ref<json::object_t const&>().at("hello")) == source_addr);
}
SECTION("assignment with implicit types (array)")
{
json j = {std::move(source)};
CHECK(&(j[0].get_ref<json::object_t const&>().at("hello")) == source_addr);
}
SECTION("assignment with implicit types (object)")
{
json j = {{"key", std::move(source)}};
CHECK(&(j["key"].get_ref<json::object_t const&>().at("hello")) == source_addr);
}
}
SECTION("json")
{
json source {1, 2, 3};
const json* source_addr = &source[0];
SECTION("constructor with implicit types (array)")
{
json j {std::move(source), {}};
CHECK(&j[0][0] == source_addr);
}
SECTION("constructor with implicit types (object)")
{
json j {{"key", std::move(source)}};
CHECK(&j["key"][0] == source_addr);
}
SECTION("assignment with implicit types (array)")
{
json j = {std::move(source), {}};
CHECK(&j[0][0] == source_addr);
}
SECTION("assignment with implicit types (object)")
{
json j = {{"key", std::move(source)}};
CHECK(&j["key"][0] == source_addr);
}
}
}
}
SECTION("create an array of n copies of a given value")