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object.hpp
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object.hpp
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//
// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/boostorg/json
//
#ifndef BOOST_JSON_OBJECT_HPP
#define BOOST_JSON_OBJECT_HPP
#include <boost/json/detail/config.hpp>
#include <boost/json/kind.hpp>
#include <boost/json/pilfer.hpp>
#include <boost/json/storage_ptr.hpp>
#include <boost/json/string_view.hpp>
#include <boost/json/detail/object.hpp>
#include <boost/json/detail/value.hpp>
#include <cstdlib>
#include <initializer_list>
#include <iterator>
#include <type_traits>
#include <utility>
BOOST_JSON_NS_BEGIN
class value;
class value_ref;
class key_value_pair;
/** A dynamically sized associative container of JSON key/value pairs.
This is an associative container whose elements
are key/value pairs with unique keys.
\n
The elements are stored contiguously; iterators are
ordinary pointers, allowing random access pointer
arithmetic for retrieving elements.
In addition, the container maintains an internal
index to speed up find operations, reducing the
average complexity for most lookups and insertions.
\n
Reallocations are usually costly operations in terms of
performance, as elements are copied and the internal
index must be rebuilt. The @ref reserve function can
be used to eliminate reallocations if the number of
elements is known beforehand.
@par Allocators
All elements stored in the container, and their
children if any, will use the same memory resource that
was used to construct the container.
@par Thread Safety
Non-const member functions may not be called
concurrently with any other member functions.
@par Satisfies
<a href="https://en.cppreference.com/w/cpp/named_req/ContiguousContainer"><em>ContiguousContainer</em></a>,
<a href="https://en.cppreference.com/w/cpp/named_req/ReversibleContainer"><em>ReversibleContainer</em></a>, and
<a href="https://en.cppreference.com/w/cpp/named_req/SequenceContainer"><em>SequenceContainer</em></a>.
*/
class object
{
struct table;
class revert_construct;
class revert_insert;
friend class value;
friend class object_test;
using access = detail::access;
using index_t = std::uint32_t;
static index_t constexpr null_index_ =
std::uint32_t(-1);
storage_ptr sp_; // must come first
kind k_ = kind::object; // must come second
table* t_;
BOOST_JSON_DECL
static table empty_;
template<class T>
using is_inputit = typename std::enable_if<
std::is_constructible<key_value_pair,
typename std::iterator_traits<T>::value_type
>::value>::type;
BOOST_JSON_DECL
explicit
object(detail::unchecked_object&& uo);
public:
/** The type of _Allocator_ returned by @ref get_allocator
This type is a @ref polymorphic_allocator.
*/
#ifdef BOOST_JSON_DOCS
// VFALCO doc toolchain renders this incorrectly
using allocator_type = __see_below__;
#else
using allocator_type = polymorphic_allocator<value>;
#endif
/** The type of keys.
The function @ref string::max_size returns the
maximum allowed size of strings used as keys.
*/
using key_type = string_view;
/// The type of mapped values
using mapped_type = value;
/// The element type
using value_type = key_value_pair;
/// The type used to represent unsigned integers
using size_type = std::size_t;
/// The type used to represent signed integers
using difference_type = std::ptrdiff_t;
/// A reference to an element
using reference = value_type&;
/// A const reference to an element
using const_reference = value_type const&;
/// A pointer to an element
using pointer = value_type*;
/// A const pointer to an element
using const_pointer = value_type const*;
/// A random access iterator to an element
using iterator = value_type*;
/// A const random access iterator to an element
using const_iterator = value_type const*;
/// A reverse random access iterator to an element
using reverse_iterator =
std::reverse_iterator<iterator>;
/// A const reverse random access iterator to an element
using const_reverse_iterator =
std::reverse_iterator<const_iterator>;
//------------------------------------------------------
/** Destructor.
The destructor for each element is called if needed,
any used memory is deallocated, and shared ownership
of the @ref memory_resource is released.
@par Complexity
Constant, or linear in @ref size().
@par Exception Safety
No-throw guarantee.
*/
BOOST_JSON_DECL
~object() noexcept;
//------------------------------------------------------
/** Default constructor.
The constructed object is empty with zero
capacity, using the default memory resource.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
object() noexcept
: t_(&empty_)
{
}
/** Constructor.
The constructed object is empty with zero
capacity, using the specified memory resource.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
@param sp A pointer to the @ref memory_resource
to use. The container will acquire shared
ownership of the memory resource.
*/
explicit
object(storage_ptr sp) noexcept
: sp_(std::move(sp))
, t_(&empty_)
{
}
/** Constructor.
The constructed object is empty with capacity
equal to the specified minimum capacity,
using the specified memory resource.
@par Complexity
Constant.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param min_capacity The minimum number
of elements for which capacity is guaranteed
without a subsequent reallocation.
@param sp A pointer to the @ref memory_resource
to use. The container will acquire shared
ownership of the memory resource.
*/
BOOST_JSON_DECL
object(
std::size_t min_capacity,
storage_ptr sp = {});
/** Constructor.
The object is constructed with the elements
in the range `{first, last)`, preserving order,
using the specified memory resource.
If there are elements with duplicate keys; that
is, if multiple elements in the range have keys
that compare equal, only the first equivalent
element will be inserted.
@par Constraints
@code
std::is_constructible_v<
key_value_pair,
std::iterator_traits<InputIt>::value_type>
@endcode
@par Complexity
Linear in `std::distance(first, last)`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param first An input iterator pointing to the
first element to insert, or pointing to the end
of the range.
@param last An input iterator pointing to the end
of the range.
@param min_capacity The minimum number
of elements for which capacity is guaranteed
without a subsequent reallocation.
Upon construction, @ref capacity() will be greater
than or equal to this number.
@param sp A pointer to the @ref memory_resource
to use. The container will acquire shared
ownership of the memory resource.
@tparam InputIt a type satisfying the requirements
of __InputIterator__.
*/
template<
class InputIt
#ifndef BOOST_JSON_DOCS
,class = is_inputit<InputIt>
#endif
>
object(
InputIt first,
InputIt last,
std::size_t min_capacity = 0,
storage_ptr sp = {})
: sp_(std::move(sp))
, t_(&empty_)
{
construct(
first, last,
min_capacity,
typename std::iterator_traits<
InputIt>::iterator_category{});
}
/** Move constructor.
The object is constructed by acquiring ownership of
the contents of `other` and shared ownership
of `other`'s memory resource.
@note
After construction, the moved-from object behaves
as if newly constructed with its current memory resource.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
@param other The object to move.
*/
BOOST_JSON_DECL
object(object&& other) noexcept;
/** Move constructor.
The object is constructed with the contents of
`other` by move semantics, using the specified
memory resource:
@li If `*other.storage() == *sp`, ownership of
the underlying memory is transferred in constant
time, with no possibility of exceptions.
After construction, the moved-from object behaves
as if newly constructed with its current storage
pointer.
@li If `*other.storage() != *sp`, an
element-wise copy is performed, which may throw.
In this case, the moved-from object is not
changed.
@par Complexity
Constant or linear in `other.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param other The object to move.
@param sp A pointer to the @ref memory_resource
to use. The container will acquire shared
ownership of the memory resource.
*/
BOOST_JSON_DECL
object(
object&& other,
storage_ptr sp);
/** Pilfer constructor.
The object is constructed by acquiring ownership
of the contents of `other` using pilfer semantics.
This is more efficient than move construction, when
it is known that the moved-from object will be
immediately destroyed afterwards.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
@param other The value to pilfer. After pilfer
construction, `other` is not in a usable state
and may only be destroyed.
@see @ref pilfer,
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0308r0.html">
Valueless Variants Considered Harmful</a>
*/
object(pilfered<object> other) noexcept
: sp_(std::move(other.get().sp_))
, t_(detail::exchange(
other.get().t_, &empty_))
{
}
/** Copy constructor.
The object is constructed with a copy of the
contents of `other`, using `other`'s memory resource.
@par Complexity
Linear in `other.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param other The object to copy.
*/
object(
object const& other)
: object(other, other.sp_)
{
}
/** Copy constructor.
The object is constructed with a copy of the
contents of `other`, using the specified memory resource.
@par Complexity
Linear in `other.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param other The object to copy.
@param sp A pointer to the @ref memory_resource
to use. The container will acquire shared
ownership of the memory resource.
*/
BOOST_JSON_DECL
object(
object const& other,
storage_ptr sp);
/** Construct from initializer-list.
The object is constructed with a copy of the values
in the initializer-list in order, using the
specified memory resource.
If there are elements with duplicate keys; that
is, if multiple elements in the range have keys
that compare equal, only the first equivalent
element will be inserted.
@par Complexity
Linear in `init.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param init The initializer list to insert.
@param sp A pointer to the @ref memory_resource
to use. The container will acquire shared
ownership of the memory resource.
*/
object(
std::initializer_list<
std::pair<string_view, value_ref>> init,
storage_ptr sp = {})
: object(init, 0, std::move(sp))
{
}
/** Construct from initializer-list.
Storage for at least `min_capacity` elements is
reserved, and then
the object is constructed with a copy of the values
in the initializer-list in order, using the
specified memory resource.
If there are elements with duplicate keys; that
is, if multiple elements in the range have keys
that compare equal, only the first equivalent
element will be inserted.
@par Complexity
Linear in `init.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param init The initializer list to insert.
@param min_capacity The minimum number
of elements for which capacity is guaranteed
without a subsequent reallocation.
Upon construction, @ref capacity() will be greater
than or equal to this number.
@param sp A pointer to the @ref memory_resource
to use. The container will acquire shared
ownership of the memory resource.
*/
BOOST_JSON_DECL
object(
std::initializer_list<
std::pair<string_view, value_ref>> init,
std::size_t min_capacity,
storage_ptr sp = {});
//------------------------------------------------------
//
// Assignment
//
//------------------------------------------------------
/** Copy assignment.
The contents of the object are replaced with an
element-wise copy of `other`.
@par Complexity
Linear in @ref size() plus `other.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param other The object to copy.
*/
BOOST_JSON_DECL
object&
operator=(object const& other);
/** Move assignment.
The contents of the object are replaced with the
contents of `other` using move semantics:
@li If `*other.storage() == *sp`, ownership of
the underlying memory is transferred in constant
time, with no possibility of exceptions.
After assignment, the moved-from object behaves
as if newly constructed with its current storage
pointer.
@li If `*other.storage() != *sp`, an
element-wise copy is performed, which may throw.
In this case, the moved-from object is not
changed.
@par Complexity
Constant or linear in @ref size() plus `other.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param other The object to move.
*/
BOOST_JSON_DECL
object&
operator=(object&& other);
/** Assignment.
Replaces the contents with the contents of an
initializer list.
@par Complexity
Linear in @ref size() plus
average case linear in `init.size()`,
worst case quadratic in `init.size()`.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param init The initializer list to copy.
*/
BOOST_JSON_DECL
object&
operator=(std::initializer_list<
std::pair<string_view, value_ref>> init);
//------------------------------------------------------
/** Return the associated @ref memory_resource
This returns the @ref memory_resource used by
the container.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
storage_ptr const&
storage() const noexcept
{
return sp_;
}
/** Return the associated @ref memory_resource
This function returns an instance of
@ref polymorphic_allocator constructed from the
associated @ref memory_resource.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
allocator_type
get_allocator() const noexcept
{
return sp_.get();
}
//------------------------------------------------------
//
// Iterators
//
//------------------------------------------------------
/** Return an iterator to the first element.
If the container is empty, @ref end() is returned.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
iterator
begin() noexcept;
/** Return a const iterator to the first element.
If the container is empty, @ref end() is returned.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_iterator
begin() const noexcept;
/** Return a const iterator to the first element.
If the container is empty, @ref cend() is returned.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_iterator
cbegin() const noexcept;
/** Return an iterator to the element following the last element.
The element acts as a placeholder; attempting
to access it results in undefined behavior.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
iterator
end() noexcept;
/** Return a const iterator to the element following the last element.
The element acts as a placeholder; attempting
to access it results in undefined behavior.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_iterator
end() const noexcept;
/** Return a const iterator to the element following the last element.
The element acts as a placeholder; attempting
to access it results in undefined behavior.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_iterator
cend() const noexcept;
/** Return a reverse iterator to the first element of the reversed container.
The pointed-to element corresponds to the
last element of the non-reversed container.
If the container is empty, @ref rend() is returned.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
reverse_iterator
rbegin() noexcept;
/** Return a const reverse iterator to the first element of the reversed container.
The pointed-to element corresponds to the
last element of the non-reversed container.
If the container is empty, @ref rend() is returned.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_reverse_iterator
rbegin() const noexcept;
/** Return a const reverse iterator to the first element of the reversed container.
The pointed-to element corresponds to the
last element of the non-reversed container.
If the container is empty, @ref crend() is returned.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_reverse_iterator
crbegin() const noexcept;
/** Return a reverse iterator to the element following the last element of the reversed container.
The pointed-to element corresponds to the element
preceding the first element of the non-reversed container.
This element acts as a placeholder, attempting
to access it results in undefined behavior.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
reverse_iterator
rend() noexcept;
/** Return a const reverse iterator to the element following the last element of the reversed container.
The pointed-to element corresponds to the element
preceding the first element of the non-reversed container.
This element acts as a placeholder, attempting
to access it results in undefined behavior.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_reverse_iterator
rend() const noexcept;
/** Return a const reverse iterator to the element following the last element of the reversed container.
The pointed-to element corresponds to the element
preceding the first element of the non-reversed container.
This element acts as a placeholder, attempting
to access it results in undefined behavior.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
const_reverse_iterator
crend() const noexcept;
//------------------------------------------------------
//
// Capacity
//
//------------------------------------------------------
/** Return whether there are no elements.
Returns `true` if there are no elements in
the container, i.e. @ref size() returns 0.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
bool
empty() const noexcept;
/** Return the number of elements.
This returns the number of elements in the container.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
std::size_t
size() const noexcept;
/** Return the maximum number of elements any object can hold
The maximum is an implementation-defined number dependent
on system or library implementation. This value is a
theoretical limit; at runtime, the actual maximum size
may be less due to resource limits.
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
static
constexpr
std::size_t
max_size() noexcept;
/** Return the number of elements that can be held in currently allocated memory
This number may be larger than the value returned
by @ref size().
@par Complexity
Constant.
@par Exception Safety
No-throw guarantee.
*/
inline
std::size_t
capacity() const noexcept;
/** Increase the capacity to at least a certain amount.
This increases the @ref capacity() to a value
that is greater than or equal to `new_capacity`.
If `new_capacity > capacity()`, new memory is
allocated. Otherwise, the call has no effect.
The number of elements and therefore the
@ref size() of the container is not changed.
\n
If new memory is allocated, all iterators
including any past-the-end iterators, and all
references to the elements are invalidated.
Otherwise, no iterators or references are
invalidated.
@par Complexity
Constant or average case linear in
@ref size(), worst case quadratic.
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param new_capacity The new minimum capacity.
@throw std::length_error `new_capacity > max_size()`
*/
void
reserve(std::size_t new_capacity)
{
if(new_capacity <= capacity())
return;
rehash(new_capacity);
}
//------------------------------------------------------
//
// Modifiers
//
//------------------------------------------------------
/** Erase all elements.
Erases all elements from the container without
changing the capacity.
After this call, @ref size() returns zero.
All references, pointers, and iterators are
invalidated.
@par Complexity
Linear in @ref size().
@par Exception Safety
No-throw guarantee.
*/
BOOST_JSON_DECL
void
clear() noexcept;
/** Insert elements.
Inserts `p` if `this->contains(value_type(p).key())` is `false`.
@ref value_type must be constructible from `p`.
If the insertion occurs and results in a rehashing
of the container, all iterators and references are invalidated.
Otherwise, they are not affected.
Rehashing occurs only if the new number of elements
is greater than @ref capacity().
@par Constraints
@code
std::is_constructible_v<value_type, P>
@endcode
@par Complexity
Average case amortized constant,
worst case linear in @ref size().
@par Exception Safety
Strong guarantee.
Calls to `memory_resource::allocate` may throw.
@param p The value to insert.
@throw std::length_error key is too long.
@throw std::length_error @ref size() >= max_size().
@return A pair where `first` is an iterator
to the existing or inserted element, and `second`
is `true` if the insertion took place or `false` otherwise.
*/
template<class P
#ifndef BOOST_JSON_DOCS
,class = typename std::enable_if<
std::is_constructible<key_value_pair,
P, storage_ptr>::value>::type
#endif
>
std::pair<iterator, bool>
insert(P&& p);
/** Insert elements.
The elements in the range `[first, last)` are inserted one at a time,
in order. Any element with key that is a duplicate of a key already
present in container will be skipped. This also means, that if there
are two keys within the range that are equal to each other, only the
first will be inserted.
If the size necessary to accomodate elements from the range exceeds
@ref capacity(), a rehashing can occur. In that case all iterators and
references are invalidated. Otherwise, they are not affected.
@par Precondition
`first` and `last` are not iterators into `*this`.
`first` and `last` form a valid range.
@par Constraints
@code
std::is_constructible_v<value_type, std::iterator_traits<InputIt>::value_type>
@endcode
@par Complexity
Linear in `std::distance(first, last)`.
@par Exception Safety
Basic guarantee.
Calls to `memory_resource::allocate` may throw.