path: root/contrib/libs/cxxsupp/libcxx/include/__split_buffer

// -*- C++ -*- 
#ifndef _LIBCPP_SPLIT_BUFFER 
#define _LIBCPP_SPLIT_BUFFER 
 
#include <__config> 
#include <__utility/forward.h> 
#include <algorithm> 
#include <type_traits> 
 
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 
#pragma GCC system_header 
#endif 
 
_LIBCPP_PUSH_MACROS 
#include <__undef_macros> 
 
 
_LIBCPP_BEGIN_NAMESPACE_STD 
 
template <class _Tp, class _Allocator = allocator<_Tp> > 
struct __split_buffer 
{ 
private: 
    __split_buffer(const __split_buffer&); 
    __split_buffer& operator=(const __split_buffer&); 
public: 
    typedef _Tp                                             value_type; 
    typedef _Allocator                                      allocator_type; 
    typedef typename remove_reference<allocator_type>::type __alloc_rr; 
    typedef allocator_traits<__alloc_rr>                    __alloc_traits; 
    typedef value_type&                                     reference; 
    typedef const value_type&                               const_reference; 
    typedef typename __alloc_traits::size_type              size_type; 
    typedef typename __alloc_traits::difference_type        difference_type; 
    typedef typename __alloc_traits::pointer                pointer; 
    typedef typename __alloc_traits::const_pointer          const_pointer; 
    typedef pointer                                         iterator; 
    typedef const_pointer                                   const_iterator; 
 
    pointer                                         __first_; 
    pointer                                         __begin_; 
    pointer                                         __end_; 
    __compressed_pair<pointer, allocator_type> __end_cap_; 
 
    typedef typename add_lvalue_reference<allocator_type>::type __alloc_ref; 
    typedef typename add_lvalue_reference<allocator_type>::type __alloc_const_ref; 
 
    _LIBCPP_INLINE_VISIBILITY __alloc_rr&           __alloc() _NOEXCEPT         {return __end_cap_.second();} 
    _LIBCPP_INLINE_VISIBILITY const __alloc_rr&     __alloc() const _NOEXCEPT   {return __end_cap_.second();} 
    _LIBCPP_INLINE_VISIBILITY pointer&              __end_cap() _NOEXCEPT       {return __end_cap_.first();} 
    _LIBCPP_INLINE_VISIBILITY const pointer&        __end_cap() const _NOEXCEPT {return __end_cap_.first();} 
 
    _LIBCPP_INLINE_VISIBILITY 
    __split_buffer() 
        _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value); 
    _LIBCPP_INLINE_VISIBILITY 
    explicit __split_buffer(__alloc_rr& __a); 
    _LIBCPP_INLINE_VISIBILITY 
    explicit __split_buffer(const __alloc_rr& __a); 
    __split_buffer(size_type __cap, size_type __start, __alloc_rr& __a); 
    ~__split_buffer(); 
 
    __split_buffer(__split_buffer&& __c) 
        _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value); 
    __split_buffer(__split_buffer&& __c, const __alloc_rr& __a); 
    __split_buffer& operator=(__split_buffer&& __c) 
        _NOEXCEPT_((__alloc_traits::propagate_on_container_move_assignment::value && 
                is_nothrow_move_assignable<allocator_type>::value) || 
               !__alloc_traits::propagate_on_container_move_assignment::value); 
 
    _LIBCPP_INLINE_VISIBILITY       iterator begin() _NOEXCEPT       {return __begin_;} 
    _LIBCPP_INLINE_VISIBILITY const_iterator begin() const _NOEXCEPT {return __begin_;} 
    _LIBCPP_INLINE_VISIBILITY       iterator end() _NOEXCEPT         {return __end_;} 
    _LIBCPP_INLINE_VISIBILITY const_iterator end() const _NOEXCEPT   {return __end_;} 
 
    _LIBCPP_INLINE_VISIBILITY 
    void clear() _NOEXCEPT 
        {__destruct_at_end(__begin_);} 
    _LIBCPP_INLINE_VISIBILITY size_type size() const {return static_cast<size_type>(__end_ - __begin_);} 
    _LIBCPP_INLINE_VISIBILITY bool empty()     const {return __end_ == __begin_;} 
    _LIBCPP_INLINE_VISIBILITY size_type capacity() const {return static_cast<size_type>(__end_cap() - __first_);} 
    _LIBCPP_INLINE_VISIBILITY size_type __front_spare() const {return static_cast<size_type>(__begin_ - __first_);} 
    _LIBCPP_INLINE_VISIBILITY size_type __back_spare() const {return static_cast<size_type>(__end_cap() - __end_);} 
 
    _LIBCPP_INLINE_VISIBILITY       reference front()       {return *__begin_;} 
    _LIBCPP_INLINE_VISIBILITY const_reference front() const {return *__begin_;} 
    _LIBCPP_INLINE_VISIBILITY       reference back()        {return *(__end_ - 1);} 
    _LIBCPP_INLINE_VISIBILITY const_reference back() const  {return *(__end_ - 1);} 
 
    void reserve(size_type __n); 
    void shrink_to_fit() _NOEXCEPT; 
    void push_front(const_reference __x); 
    _LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x); 
    void push_front(value_type&& __x); 
    void push_back(value_type&& __x); 
    template <class... _Args> 
        void emplace_back(_Args&&... __args); 
 
    _LIBCPP_INLINE_VISIBILITY void pop_front() {__destruct_at_begin(__begin_+1);} 
    _LIBCPP_INLINE_VISIBILITY void pop_back() {__destruct_at_end(__end_-1);} 
 
    void __uninitialized_at_end(size_type __n); 
    void __construct_at_end(size_type __n); 
    void __construct_at_end(size_type __n, const_reference __x); 
    template <class _InputIter> 
        typename enable_if 
        < 
            __is_cpp17_input_iterator<_InputIter>::value && 
           !__is_cpp17_forward_iterator<_InputIter>::value, 
            void 
        >::type 
        __construct_at_end(_InputIter __first, _InputIter __last); 
    template <class _ForwardIterator> 
        typename enable_if 
        < 
            __is_cpp17_forward_iterator<_ForwardIterator>::value, 
            void 
        >::type 
        __construct_at_end(_ForwardIterator __first, _ForwardIterator __last); 
 
    _LIBCPP_INLINE_VISIBILITY void __destruct_at_begin(pointer __new_begin) 
        {__destruct_at_begin(__new_begin, is_trivially_destructible<value_type>());} 
        _LIBCPP_INLINE_VISIBILITY 
        void __destruct_at_begin(pointer __new_begin, false_type); 
        _LIBCPP_INLINE_VISIBILITY 
        void __destruct_at_begin(pointer __new_begin, true_type); 
 
    _LIBCPP_INLINE_VISIBILITY 
    void __destruct_at_end(pointer __new_last) _NOEXCEPT 
        {__destruct_at_end(__new_last, false_type());} 
    _LIBCPP_INLINE_VISIBILITY 
        void __destruct_at_end(pointer __new_last, false_type) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY 
        void __destruct_at_end(pointer __new_last, true_type) _NOEXCEPT; 
 
    void swap(__split_buffer& __x) 
        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value|| 
                   __is_nothrow_swappable<__alloc_rr>::value); 
 
    bool __invariants() const; 
 
private: 
    _LIBCPP_INLINE_VISIBILITY 
    void __move_assign_alloc(__split_buffer& __c, true_type) 
        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value) 
        { 
            __alloc() = _VSTD::move(__c.__alloc()); 
        } 
 
    _LIBCPP_INLINE_VISIBILITY 
    void __move_assign_alloc(__split_buffer&, false_type) _NOEXCEPT 
        {} 
 
    struct _ConstructTransaction { 
      explicit _ConstructTransaction(pointer* __p, size_type __n) _NOEXCEPT 
      : __pos_(*__p), __end_(*__p + __n), __dest_(__p) { 
      } 
      ~_ConstructTransaction() { 
        *__dest_ = __pos_; 
      } 
      pointer __pos_; 
     const pointer __end_; 
    private: 
     pointer *__dest_; 
    }; 
}; 
 
template <class _Tp, class _Allocator> 
bool 
__split_buffer<_Tp, _Allocator>::__invariants() const 
{ 
    if (__first_ == nullptr) 
    { 
        if (__begin_ != nullptr) 
            return false; 
        if (__end_ != nullptr) 
            return false; 
        if (__end_cap() != nullptr) 
            return false; 
    } 
    else 
    { 
        if (__begin_ < __first_) 
            return false; 
        if (__end_ < __begin_) 
            return false; 
        if (__end_cap() < __end_) 
            return false; 
    } 
    return true; 
} 
 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::__uninitialized_at_end(size_type __n) 
{ 
    this->__end_ += __n; 
} 
 
//  Default constructs __n objects starting at __end_ 
//  throws if construction throws 
//  Precondition:  __n > 0 
//  Precondition:  size() + __n <= capacity() 
//  Postcondition:  size() == size() + __n 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::__construct_at_end(size_type __n) 
{ 
    _ConstructTransaction __tx(&this->__end_, __n); 
    for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) { 
        __alloc_traits::construct(this->__alloc(), _VSTD::__to_address(__tx.__pos_)); 
    } 
} 
 
//  Copy constructs __n objects starting at __end_ from __x 
//  throws if construction throws 
//  Precondition:  __n > 0 
//  Precondition:  size() + __n <= capacity() 
//  Postcondition:  size() == old size() + __n 
//  Postcondition:  [i] == __x for all i in [size() - __n, __n) 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::__construct_at_end(size_type __n, const_reference __x) 
{ 
    _ConstructTransaction __tx(&this->__end_, __n); 
    for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) { 
        __alloc_traits::construct(this->__alloc(), 
            _VSTD::__to_address(__tx.__pos_), __x); 
    } 
} 
 
template <class _Tp, class _Allocator> 
template <class _InputIter> 
typename enable_if 
< 
     __is_cpp17_input_iterator<_InputIter>::value && 
    !__is_cpp17_forward_iterator<_InputIter>::value, 
    void 
>::type 
__split_buffer<_Tp, _Allocator>::__construct_at_end(_InputIter __first, _InputIter __last) 
{ 
    __alloc_rr& __a = this->__alloc(); 
    for (; __first != __last; ++__first) 
    { 
        if (__end_ == __end_cap()) 
        { 
            size_type __old_cap = __end_cap() - __first_; 
            size_type __new_cap = _VSTD::max<size_type>(2 * __old_cap, 8); 
            __split_buffer __buf(__new_cap, 0, __a); 
            for (pointer __p = __begin_; __p != __end_; ++__p, (void) ++__buf.__end_) 
                __alloc_traits::construct(__buf.__alloc(), 
                        _VSTD::__to_address(__buf.__end_), _VSTD::move(*__p)); 
            swap(__buf); 
        } 
        __alloc_traits::construct(__a, _VSTD::__to_address(this->__end_), *__first); 
        ++this->__end_; 
    } 
} 
 
template <class _Tp, class _Allocator> 
template <class _ForwardIterator> 
typename enable_if 
< 
    __is_cpp17_forward_iterator<_ForwardIterator>::value, 
    void 
>::type 
__split_buffer<_Tp, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last) 
{ 
    _ConstructTransaction __tx(&this->__end_, _VSTD::distance(__first, __last)); 
    for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_, (void) ++__first) { 
        __alloc_traits::construct(this->__alloc(), 
            _VSTD::__to_address(__tx.__pos_), *__first); 
    } 
} 
 
template <class _Tp, class _Allocator> 
inline 
void 
__split_buffer<_Tp, _Allocator>::__destruct_at_begin(pointer __new_begin, false_type) 
{ 
    while (__begin_ != __new_begin) 
        __alloc_traits::destroy(__alloc(), _VSTD::__to_address(__begin_++)); 
} 
 
template <class _Tp, class _Allocator> 
inline 
void 
__split_buffer<_Tp, _Allocator>::__destruct_at_begin(pointer __new_begin, true_type) 
{ 
    __begin_ = __new_begin; 
} 
 
template <class _Tp, class _Allocator> 
inline _LIBCPP_INLINE_VISIBILITY 
void 
__split_buffer<_Tp, _Allocator>::__destruct_at_end(pointer __new_last, false_type) _NOEXCEPT 
{ 
    while (__new_last != __end_) 
        __alloc_traits::destroy(__alloc(), _VSTD::__to_address(--__end_)); 
} 
 
template <class _Tp, class _Allocator> 
inline _LIBCPP_INLINE_VISIBILITY 
void 
__split_buffer<_Tp, _Allocator>::__destruct_at_end(pointer __new_last, true_type) _NOEXCEPT 
{ 
    __end_ = __new_last; 
} 
 
template <class _Tp, class _Allocator> 
__split_buffer<_Tp, _Allocator>::__split_buffer(size_type __cap, size_type __start, __alloc_rr& __a) 
    : __end_cap_(nullptr, __a) 
{ 
    __first_ = __cap != 0 ? __alloc_traits::allocate(__alloc(), __cap) : nullptr; 
    __begin_ = __end_ = __first_ + __start; 
    __end_cap() = __first_ + __cap; 
} 
 
template <class _Tp, class _Allocator> 
inline 
__split_buffer<_Tp, _Allocator>::__split_buffer() 
    _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value) 
    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr, __default_init_tag()) 
{ 
} 
 
template <class _Tp, class _Allocator> 
inline 
__split_buffer<_Tp, _Allocator>::__split_buffer(__alloc_rr& __a) 
    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr, __a) 
{ 
} 
 
template <class _Tp, class _Allocator> 
inline 
__split_buffer<_Tp, _Allocator>::__split_buffer(const __alloc_rr& __a) 
    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr, __a) 
{ 
} 
 
template <class _Tp, class _Allocator> 
__split_buffer<_Tp, _Allocator>::~__split_buffer() 
{ 
    clear(); 
    if (__first_) 
        __alloc_traits::deallocate(__alloc(), __first_, capacity()); 
} 
 
template <class _Tp, class _Allocator> 
__split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c) 
    _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value) 
    : __first_(_VSTD::move(__c.__first_)), 
      __begin_(_VSTD::move(__c.__begin_)), 
      __end_(_VSTD::move(__c.__end_)), 
      __end_cap_(_VSTD::move(__c.__end_cap_)) 
{ 
    __c.__first_ = nullptr; 
    __c.__begin_ = nullptr; 
    __c.__end_ = nullptr; 
    __c.__end_cap() = nullptr; 
} 
 
template <class _Tp, class _Allocator> 
__split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c, const __alloc_rr& __a) 
    : __end_cap_(nullptr, __a) 
{ 
    if (__a == __c.__alloc()) 
    { 
        __first_ = __c.__first_; 
        __begin_ = __c.__begin_; 
        __end_ = __c.__end_; 
        __end_cap() = __c.__end_cap(); 
        __c.__first_ = nullptr; 
        __c.__begin_ = nullptr; 
        __c.__end_ = nullptr; 
        __c.__end_cap() = nullptr; 
    } 
    else 
    { 
        size_type __cap = __c.size(); 
        __first_ = __alloc_traits::allocate(__alloc(), __cap); 
        __begin_ = __end_ = __first_; 
        __end_cap() = __first_ + __cap; 
        typedef move_iterator<iterator> _Ip; 
        __construct_at_end(_Ip(__c.begin()), _Ip(__c.end())); 
    } 
} 
 
template <class _Tp, class _Allocator> 
__split_buffer<_Tp, _Allocator>& 
__split_buffer<_Tp, _Allocator>::operator=(__split_buffer&& __c) 
    _NOEXCEPT_((__alloc_traits::propagate_on_container_move_assignment::value && 
                is_nothrow_move_assignable<allocator_type>::value) || 
               !__alloc_traits::propagate_on_container_move_assignment::value) 
{ 
    clear(); 
    shrink_to_fit(); 
    __first_ = __c.__first_; 
    __begin_ = __c.__begin_; 
    __end_ = __c.__end_; 
    __end_cap() = __c.__end_cap(); 
    __move_assign_alloc(__c, 
        integral_constant<bool, 
                          __alloc_traits::propagate_on_container_move_assignment::value>()); 
    __c.__first_ = __c.__begin_ = __c.__end_ = __c.__end_cap() = nullptr; 
    return *this; 
} 
 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::swap(__split_buffer& __x) 
        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value|| 
                   __is_nothrow_swappable<__alloc_rr>::value) 
{ 
    _VSTD::swap(__first_, __x.__first_); 
    _VSTD::swap(__begin_, __x.__begin_); 
    _VSTD::swap(__end_, __x.__end_); 
    _VSTD::swap(__end_cap(), __x.__end_cap()); 
    _VSTD::__swap_allocator(__alloc(), __x.__alloc()); 
} 
 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::reserve(size_type __n) 
{ 
    if (__n < capacity()) 
    { 
        __split_buffer<value_type, __alloc_rr&> __t(__n, 0, __alloc()); 
        __t.__construct_at_end(move_iterator<pointer>(__begin_), 
                               move_iterator<pointer>(__end_)); 
        _VSTD::swap(__first_, __t.__first_); 
        _VSTD::swap(__begin_, __t.__begin_); 
        _VSTD::swap(__end_, __t.__end_); 
        _VSTD::swap(__end_cap(), __t.__end_cap()); 
    } 
} 
 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::shrink_to_fit() _NOEXCEPT 
{ 
    if (capacity() > size()) 
    { 
#ifndef _LIBCPP_NO_EXCEPTIONS 
        try 
        { 
#endif // _LIBCPP_NO_EXCEPTIONS 
            __split_buffer<value_type, __alloc_rr&> __t(size(), 0, __alloc()); 
            __t.__construct_at_end(move_iterator<pointer>(__begin_), 
                                   move_iterator<pointer>(__end_)); 
            __t.__end_ = __t.__begin_ + (__end_ - __begin_); 
            _VSTD::swap(__first_, __t.__first_); 
            _VSTD::swap(__begin_, __t.__begin_); 
            _VSTD::swap(__end_, __t.__end_); 
            _VSTD::swap(__end_cap(), __t.__end_cap()); 
#ifndef _LIBCPP_NO_EXCEPTIONS 
        } 
        catch (...) 
        { 
        } 
#endif // _LIBCPP_NO_EXCEPTIONS 
    } 
} 
 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::push_front(const_reference __x) 
{ 
    if (__begin_ == __first_) 
    { 
        if (__end_ < __end_cap()) 
        { 
            difference_type __d = __end_cap() - __end_; 
            __d = (__d + 1) / 2; 
            __begin_ = _VSTD::move_backward(__begin_, __end_, __end_ + __d); 
            __end_ += __d; 
        } 
        else 
        { 
            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1); 
            __split_buffer<value_type, __alloc_rr&> __t(__c, (__c + 3) / 4, __alloc()); 
            __t.__construct_at_end(move_iterator<pointer>(__begin_), 
                                   move_iterator<pointer>(__end_)); 
            _VSTD::swap(__first_, __t.__first_); 
            _VSTD::swap(__begin_, __t.__begin_); 
            _VSTD::swap(__end_, __t.__end_); 
            _VSTD::swap(__end_cap(), __t.__end_cap()); 
        } 
    } 
    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__begin_-1), __x); 
    --__begin_; 
} 
 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::push_front(value_type&& __x) 
{ 
    if (__begin_ == __first_) 
    { 
        if (__end_ < __end_cap()) 
        { 
            difference_type __d = __end_cap() - __end_; 
            __d = (__d + 1) / 2; 
            __begin_ = _VSTD::move_backward(__begin_, __end_, __end_ + __d); 
            __end_ += __d; 
        } 
        else 
        { 
            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1); 
            __split_buffer<value_type, __alloc_rr&> __t(__c, (__c + 3) / 4, __alloc()); 
            __t.__construct_at_end(move_iterator<pointer>(__begin_), 
                                   move_iterator<pointer>(__end_)); 
            _VSTD::swap(__first_, __t.__first_); 
            _VSTD::swap(__begin_, __t.__begin_); 
            _VSTD::swap(__end_, __t.__end_); 
            _VSTD::swap(__end_cap(), __t.__end_cap()); 
        } 
    } 
    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__begin_-1), 
            _VSTD::move(__x)); 
    --__begin_; 
} 
 
template <class _Tp, class _Allocator> 
inline _LIBCPP_INLINE_VISIBILITY 
void 
__split_buffer<_Tp, _Allocator>::push_back(const_reference __x) 
{ 
    if (__end_ == __end_cap()) 
    { 
        if (__begin_ > __first_) 
        { 
            difference_type __d = __begin_ - __first_; 
            __d = (__d + 1) / 2; 
            __end_ = _VSTD::move(__begin_, __end_, __begin_ - __d); 
            __begin_ -= __d; 
        } 
        else 
        { 
            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1); 
            __split_buffer<value_type, __alloc_rr&> __t(__c, __c / 4, __alloc()); 
            __t.__construct_at_end(move_iterator<pointer>(__begin_), 
                                   move_iterator<pointer>(__end_)); 
            _VSTD::swap(__first_, __t.__first_); 
            _VSTD::swap(__begin_, __t.__begin_); 
            _VSTD::swap(__end_, __t.__end_); 
            _VSTD::swap(__end_cap(), __t.__end_cap()); 
        } 
    } 
    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__end_), __x); 
    ++__end_; 
} 
 
template <class _Tp, class _Allocator> 
void 
__split_buffer<_Tp, _Allocator>::push_back(value_type&& __x) 
{ 
    if (__end_ == __end_cap()) 
    { 
        if (__begin_ > __first_) 
        { 
            difference_type __d = __begin_ - __first_; 
            __d = (__d + 1) / 2; 
            __end_ = _VSTD::move(__begin_, __end_, __begin_ - __d); 
            __begin_ -= __d; 
        } 
        else 
        { 
            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1); 
            __split_buffer<value_type, __alloc_rr&> __t(__c, __c / 4, __alloc()); 
            __t.__construct_at_end(move_iterator<pointer>(__begin_), 
                                   move_iterator<pointer>(__end_)); 
            _VSTD::swap(__first_, __t.__first_); 
            _VSTD::swap(__begin_, __t.__begin_); 
            _VSTD::swap(__end_, __t.__end_); 
            _VSTD::swap(__end_cap(), __t.__end_cap()); 
        } 
    } 
    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__end_), 
            _VSTD::move(__x)); 
    ++__end_; 
} 
 
template <class _Tp, class _Allocator> 
template <class... _Args> 
void 
__split_buffer<_Tp, _Allocator>::emplace_back(_Args&&... __args) 
{ 
    if (__end_ == __end_cap()) 
    { 
        if (__begin_ > __first_) 
        { 
            difference_type __d = __begin_ - __first_; 
            __d = (__d + 1) / 2; 
            __end_ = _VSTD::move(__begin_, __end_, __begin_ - __d); 
            __begin_ -= __d; 
        } 
        else 
        { 
            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1); 
            __split_buffer<value_type, __alloc_rr&> __t(__c, __c / 4, __alloc()); 
            __t.__construct_at_end(move_iterator<pointer>(__begin_), 
                                   move_iterator<pointer>(__end_)); 
            _VSTD::swap(__first_, __t.__first_); 
            _VSTD::swap(__begin_, __t.__begin_); 
            _VSTD::swap(__end_, __t.__end_); 
            _VSTD::swap(__end_cap(), __t.__end_cap()); 
        } 
    } 
    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__end_), 
                              _VSTD::forward<_Args>(__args)...); 
    ++__end_; 
} 
 
template <class _Tp, class _Allocator> 
inline _LIBCPP_INLINE_VISIBILITY 
void 
swap(__split_buffer<_Tp, _Allocator>& __x, __split_buffer<_Tp, _Allocator>& __y) 
        _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y))) 
{ 
    __x.swap(__y); 
} 
 
_LIBCPP_END_NAMESPACE_STD 
 
_LIBCPP_POP_MACROS 
 
#endif // _LIBCPP_SPLIT_BUFFER