json/include/nlohmann/detail/iterators/iter_impl.hpp
Niels Lohmann 433da31334
⚗️ try to use GCC 10
2020-12-29 20:16:51 +01:00

661 lines
19 KiB
C++

#pragma once
#include <iterator> // iterator, random_access_iterator_tag, bidirectional_iterator_tag, advance, next
#include <type_traits> // conditional, is_const, remove_const
#include <nlohmann/detail/exceptions.hpp>
#include <nlohmann/detail/iterators/internal_iterator.hpp>
#include <nlohmann/detail/iterators/primitive_iterator.hpp>
#include <nlohmann/detail/macro_scope.hpp>
#include <nlohmann/detail/meta/cpp_future.hpp>
#include <nlohmann/detail/meta/type_traits.hpp>
#include <nlohmann/detail/value_t.hpp>
namespace nlohmann
{
namespace detail
{
// forward declare, to be able to friend it later on
template<typename IteratorType> class iteration_proxy;
template<typename IteratorType> class iteration_proxy_value;
/*!
@brief a template for a bidirectional iterator for the @ref basic_json class
This class implements a both iterators (iterator and const_iterator) for the
@ref basic_json class.
@note An iterator is called *initialized* when a pointer to a JSON value has
been set (e.g., by a constructor or a copy assignment). If the iterator is
default-constructed, it is *uninitialized* and most methods are undefined.
**The library uses assertions to detect calls on uninitialized iterators.**
@requirement The class satisfies the following concept requirements:
-
[BidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator):
The iterator that can be moved can be moved in both directions (i.e.
incremented and decremented).
@since version 1.0.0, simplified in version 2.0.9, change to bidirectional
iterators in version 3.0.0 (see https://github.com/nlohmann/json/issues/593)
*/
template<typename BasicJsonType>
class iter_impl
{
/// allow basic_json to access private members
friend iter_impl<typename std::conditional<std::is_const<BasicJsonType>::value, typename std::remove_const<BasicJsonType>::type, const BasicJsonType>::type>;
friend BasicJsonType;
friend iteration_proxy<iter_impl>;
friend iteration_proxy_value<iter_impl>;
using object_t = typename BasicJsonType::object_t;
using array_t = typename BasicJsonType::array_t;
// make sure BasicJsonType is basic_json or const basic_json
static_assert(is_basic_json<typename std::remove_const<BasicJsonType>::type>::value,
"iter_impl only accepts (const) basic_json");
public:
/// The std::iterator class template (used as a base class to provide typedefs) is deprecated in C++17.
/// The C++ Standard has never required user-defined iterators to derive from std::iterator.
/// A user-defined iterator should provide publicly accessible typedefs named
/// iterator_category, value_type, difference_type, pointer, and reference.
/// Note that value_type is required to be non-const, even for constant iterators.
using iterator_category = std::bidirectional_iterator_tag;
/// the type of the values when the iterator is dereferenced
using value_type = typename BasicJsonType::value_type;
/// a type to represent differences between iterators
using difference_type = typename BasicJsonType::difference_type;
/// defines a pointer to the type iterated over (value_type)
using pointer = typename std::conditional<std::is_const<BasicJsonType>::value,
typename BasicJsonType::const_pointer,
typename BasicJsonType::pointer>::type;
/// defines a reference to the type iterated over (value_type)
using reference =
typename std::conditional<std::is_const<BasicJsonType>::value,
typename BasicJsonType::const_reference,
typename BasicJsonType::reference>::type;
/// default constructor
iter_impl() = default;
/*!
@brief constructor for a given JSON instance
@param[in] object pointer to a JSON object for this iterator
@pre object != nullptr
@post The iterator is initialized; i.e. `m_object != nullptr`.
*/
explicit iter_impl(pointer object) noexcept : m_object(object)
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
{
m_it.object_iterator = typename object_t::iterator();
break;
}
case value_t::array:
{
m_it.array_iterator = typename array_t::iterator();
break;
}
default:
{
m_it.primitive_iterator = primitive_iterator_t();
break;
}
}
}
/*!
@note The conventional copy constructor and copy assignment are implicitly
defined. Combined with the following converting constructor and
assignment, they support: (1) copy from iterator to iterator, (2)
copy from const iterator to const iterator, and (3) conversion from
iterator to const iterator. However conversion from const iterator
to iterator is not defined.
*/
/*!
@brief const copy constructor
@param[in] other const iterator to copy from
@note This copy constructor had to be defined explicitly to circumvent a bug
occurring on msvc v19.0 compiler (VS 2015) debug build. For more
information refer to: https://github.com/nlohmann/json/issues/1608
*/
iter_impl(const iter_impl<const BasicJsonType>& other) noexcept
: m_object(other.m_object), m_it(other.m_it)
{}
/*!
@brief converting assignment
@param[in] other const iterator to copy from
@return const/non-const iterator
@note It is not checked whether @a other is initialized.
*/
iter_impl& operator=(const iter_impl<const BasicJsonType>& other) noexcept
{
m_object = other.m_object;
m_it = other.m_it;
return *this;
}
/*!
@brief converting constructor
@param[in] other non-const iterator to copy from
@note It is not checked whether @a other is initialized.
*/
iter_impl(const iter_impl<typename std::remove_const<BasicJsonType>::type>& other) noexcept
: m_object(other.m_object), m_it(other.m_it)
{}
/*!
@brief converting assignment
@param[in] other non-const iterator to copy from
@return const/non-const iterator
@note It is not checked whether @a other is initialized.
*/
iter_impl& operator=(const iter_impl<typename std::remove_const<BasicJsonType>::type>& other) noexcept
{
m_object = other.m_object;
m_it = other.m_it;
return *this;
}
JSON_PRIVATE_UNLESS_TESTED:
/*!
@brief set the iterator to the first value
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
void set_begin() noexcept
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
{
m_it.object_iterator = m_object->m_value.object->begin();
break;
}
case value_t::array:
{
m_it.array_iterator = m_object->m_value.array->begin();
break;
}
case value_t::null:
{
// set to end so begin()==end() is true: null is empty
m_it.primitive_iterator.set_end();
break;
}
default:
{
m_it.primitive_iterator.set_begin();
break;
}
}
}
/*!
@brief set the iterator past the last value
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
void set_end() noexcept
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
{
m_it.object_iterator = m_object->m_value.object->end();
break;
}
case value_t::array:
{
m_it.array_iterator = m_object->m_value.array->end();
break;
}
default:
{
m_it.primitive_iterator.set_end();
break;
}
}
}
public:
/*!
@brief return a reference to the value pointed to by the iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
reference operator*() const
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
{
JSON_ASSERT(m_it.object_iterator != m_object->m_value.object->end());
return m_it.object_iterator->second;
}
case value_t::array:
{
JSON_ASSERT(m_it.array_iterator != m_object->m_value.array->end());
return *m_it.array_iterator;
}
case value_t::null:
JSON_THROW(invalid_iterator::create(214, "cannot get value"));
default:
{
if (JSON_HEDLEY_LIKELY(m_it.primitive_iterator.is_begin()))
{
return *m_object;
}
JSON_THROW(invalid_iterator::create(214, "cannot get value"));
}
}
}
/*!
@brief dereference the iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
pointer operator->() const
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
{
JSON_ASSERT(m_it.object_iterator != m_object->m_value.object->end());
return &(m_it.object_iterator->second);
}
case value_t::array:
{
JSON_ASSERT(m_it.array_iterator != m_object->m_value.array->end());
return &*m_it.array_iterator;
}
default:
{
if (JSON_HEDLEY_LIKELY(m_it.primitive_iterator.is_begin()))
{
return m_object;
}
JSON_THROW(invalid_iterator::create(214, "cannot get value"));
}
}
}
/*!
@brief post-increment (it++)
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl const operator++(int)
{
auto result = *this;
++(*this);
return result;
}
/*!
@brief pre-increment (++it)
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl& operator++()
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
{
std::advance(m_it.object_iterator, 1);
break;
}
case value_t::array:
{
std::advance(m_it.array_iterator, 1);
break;
}
default:
{
++m_it.primitive_iterator;
break;
}
}
return *this;
}
/*!
@brief post-decrement (it--)
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl const operator--(int)
{
auto result = *this;
--(*this);
return result;
}
/*!
@brief pre-decrement (--it)
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl& operator--()
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
{
std::advance(m_it.object_iterator, -1);
break;
}
case value_t::array:
{
std::advance(m_it.array_iterator, -1);
break;
}
default:
{
--m_it.primitive_iterator;
break;
}
}
return *this;
}
/*!
@brief comparison: equal
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
bool operator==(const iter_impl<const BasicJsonType>& other) const
{
// if objects are not the same, the comparison is undefined
if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
{
JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers"));
}
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
return (m_it.object_iterator == other.m_it.object_iterator);
case value_t::array:
return (m_it.array_iterator == other.m_it.array_iterator);
default:
return (m_it.primitive_iterator == other.m_it.primitive_iterator);
}
}
bool operator==(const iter_impl<typename std::remove_const<BasicJsonType>::type>& other) const
{
// if objects are not the same, the comparison is undefined
if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
{
JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers"));
}
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
return (m_it.object_iterator == other.m_it.object_iterator);
case value_t::array:
return (m_it.array_iterator == other.m_it.array_iterator);
default:
return (m_it.primitive_iterator == other.m_it.primitive_iterator);
}
}
/*!
@brief comparison: not equal
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
bool operator!=(const iter_impl& other) const
{
return !operator==(other);
}
/*!
@brief comparison: smaller
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
bool operator<(const iter_impl& other) const
{
// if objects are not the same, the comparison is undefined
if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
{
JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers"));
}
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
JSON_THROW(invalid_iterator::create(213, "cannot compare order of object iterators"));
case value_t::array:
return (m_it.array_iterator < other.m_it.array_iterator);
default:
return (m_it.primitive_iterator < other.m_it.primitive_iterator);
}
}
/*!
@brief comparison: less than or equal
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
bool operator<=(const iter_impl& other) const
{
return !other.operator < (*this);
}
/*!
@brief comparison: greater than
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
bool operator>(const iter_impl& other) const
{
return !operator<=(other);
}
/*!
@brief comparison: greater than or equal
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
bool operator>=(const iter_impl& other) const
{
return !operator<(other);
}
/*!
@brief add to iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl& operator+=(difference_type i)
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators"));
case value_t::array:
{
std::advance(m_it.array_iterator, i);
break;
}
default:
{
m_it.primitive_iterator += i;
break;
}
}
return *this;
}
/*!
@brief subtract from iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl& operator-=(difference_type i)
{
return operator+=(-i);
}
/*!
@brief add to iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl operator+(difference_type i) const
{
auto result = *this;
result += i;
return result;
}
/*!
@brief addition of distance and iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
friend iter_impl operator+(difference_type i, const iter_impl& it)
{
auto result = it;
result += i;
return result;
}
/*!
@brief subtract from iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
iter_impl operator-(difference_type i) const
{
auto result = *this;
result -= i;
return result;
}
/*!
@brief return difference
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
difference_type operator-(const iter_impl& other) const
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators"));
case value_t::array:
return m_it.array_iterator - other.m_it.array_iterator;
default:
return m_it.primitive_iterator - other.m_it.primitive_iterator;
}
}
/*!
@brief access to successor
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
reference operator[](difference_type n) const
{
JSON_ASSERT(m_object != nullptr);
switch (m_object->m_type)
{
case value_t::object:
JSON_THROW(invalid_iterator::create(208, "cannot use operator[] for object iterators"));
case value_t::array:
return *std::next(m_it.array_iterator, n);
case value_t::null:
JSON_THROW(invalid_iterator::create(214, "cannot get value"));
default:
{
if (JSON_HEDLEY_LIKELY(m_it.primitive_iterator.get_value() == -n))
{
return *m_object;
}
JSON_THROW(invalid_iterator::create(214, "cannot get value"));
}
}
}
/*!
@brief return the key of an object iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
const typename object_t::key_type& key() const
{
JSON_ASSERT(m_object != nullptr);
if (JSON_HEDLEY_LIKELY(m_object->is_object()))
{
return m_it.object_iterator->first;
}
JSON_THROW(invalid_iterator::create(207, "cannot use key() for non-object iterators"));
}
/*!
@brief return the value of an iterator
@pre The iterator is initialized; i.e. `m_object != nullptr`.
*/
reference value() const
{
return operator*();
}
JSON_PRIVATE_UNLESS_TESTED:
/// associated JSON instance
pointer m_object = nullptr;
/// the actual iterator of the associated instance
internal_iterator<typename std::remove_const<BasicJsonType>::type> m_it {};
};
} // namespace detail
} // namespace nlohmann