1// -*- C++ -*-
2#ifndef _LIBCPP_SPLIT_BUFFER
3#define _LIBCPP_SPLIT_BUFFER
4
5#include <__config>
6#include <type_traits>
7#include <algorithm>
8
9#include <__undef_min_max>
10
11#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
12#pragma GCC system_header
13#endif
14
15_LIBCPP_BEGIN_NAMESPACE_STD
16
17template <bool>
18class __split_buffer_common
19{
20protected:
21    void __throw_length_error() const;
22    void __throw_out_of_range() const;
23};
24
25template <class _Tp, class _Allocator = allocator<_Tp> >
26struct __split_buffer
27    : private __split_buffer_common<true>
28{
29private:
30    __split_buffer(const __split_buffer&);
31    __split_buffer& operator=(const __split_buffer&);
32public:
33    typedef _Tp                                             value_type;
34    typedef _Allocator                                      allocator_type;
35    typedef typename remove_reference<allocator_type>::type __alloc_rr;
36    typedef allocator_traits<__alloc_rr>                    __alloc_traits;
37    typedef value_type&                                     reference;
38    typedef const value_type&                               const_reference;
39    typedef typename __alloc_traits::size_type              size_type;
40    typedef typename __alloc_traits::difference_type        difference_type;
41    typedef typename __alloc_traits::pointer                pointer;
42    typedef typename __alloc_traits::const_pointer          const_pointer;
43    typedef pointer                                         iterator;
44    typedef const_pointer                                   const_iterator;
45
46    pointer                                         __first_;
47    pointer                                         __begin_;
48    pointer                                         __end_;
49    __compressed_pair<pointer, allocator_type> __end_cap_;
50
51    typedef typename add_lvalue_reference<allocator_type>::type __alloc_ref;
52    typedef typename add_lvalue_reference<allocator_type>::type __alloc_const_ref;
53
54    _LIBCPP_INLINE_VISIBILITY __alloc_rr&           __alloc() _NOEXCEPT         {return __end_cap_.second();}
55    _LIBCPP_INLINE_VISIBILITY const __alloc_rr&     __alloc() const _NOEXCEPT   {return __end_cap_.second();}
56    _LIBCPP_INLINE_VISIBILITY pointer&              __end_cap() _NOEXCEPT       {return __end_cap_.first();}
57    _LIBCPP_INLINE_VISIBILITY const pointer&        __end_cap() const _NOEXCEPT {return __end_cap_.first();}
58
59    __split_buffer()
60        _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value);
61    explicit __split_buffer(__alloc_rr& __a);
62    explicit __split_buffer(const __alloc_rr& __a);
63    __split_buffer(size_type __cap, size_type __start, __alloc_rr& __a);
64    ~__split_buffer();
65
66#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
67    __split_buffer(__split_buffer&& __c)
68        _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
69    __split_buffer(__split_buffer&& __c, const __alloc_rr& __a);
70    __split_buffer& operator=(__split_buffer&& __c)
71        _NOEXCEPT_((__alloc_traits::propagate_on_container_move_assignment::value &&
72                is_nothrow_move_assignable<allocator_type>::value) ||
73               !__alloc_traits::propagate_on_container_move_assignment::value);
74#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
75
76    _LIBCPP_INLINE_VISIBILITY       iterator begin() _NOEXCEPT       {return __begin_;}
77    _LIBCPP_INLINE_VISIBILITY const_iterator begin() const _NOEXCEPT {return __begin_;}
78    _LIBCPP_INLINE_VISIBILITY       iterator end() _NOEXCEPT         {return __end_;}
79    _LIBCPP_INLINE_VISIBILITY const_iterator end() const _NOEXCEPT   {return __end_;}
80
81    _LIBCPP_INLINE_VISIBILITY
82    void clear() _NOEXCEPT
83        {__destruct_at_end(__begin_);}
84    _LIBCPP_INLINE_VISIBILITY size_type size() const {return static_cast<size_type>(__end_ - __begin_);}
85    _LIBCPP_INLINE_VISIBILITY bool empty()     const {return __end_ == __begin_;}
86    _LIBCPP_INLINE_VISIBILITY size_type capacity() const {return static_cast<size_type>(__end_cap() - __first_);}
87    _LIBCPP_INLINE_VISIBILITY size_type __front_spare() const {return static_cast<size_type>(__begin_ - __first_);}
88    _LIBCPP_INLINE_VISIBILITY size_type __back_spare() const {return static_cast<size_type>(__end_cap() - __end_);}
89
90    _LIBCPP_INLINE_VISIBILITY       reference front()       {return *__begin_;}
91    _LIBCPP_INLINE_VISIBILITY const_reference front() const {return *__begin_;}
92    _LIBCPP_INLINE_VISIBILITY       reference back()        {return *(__end_ - 1);}
93    _LIBCPP_INLINE_VISIBILITY const_reference back() const  {return *(__end_ - 1);}
94
95    void reserve(size_type __n);
96    void shrink_to_fit() _NOEXCEPT;
97    void push_front(const_reference __x);
98    _LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
99#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
100    void push_front(value_type&& __x);
101    void push_back(value_type&& __x);
102#if !defined(_LIBCPP_HAS_NO_VARIADICS)
103    template <class... _Args>
104        void emplace_back(_Args&&... __args);
105#endif  // !defined(_LIBCPP_HAS_NO_VARIADICS)
106#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
107
108    _LIBCPP_INLINE_VISIBILITY void pop_front() {__destruct_at_begin(__begin_+1);}
109    _LIBCPP_INLINE_VISIBILITY void pop_back() {__destruct_at_end(__end_-1);}
110
111    void __construct_at_end(size_type __n);
112    void __construct_at_end(size_type __n, const_reference __x);
113    template <class _InputIter>
114        typename enable_if
115        <
116            __is_input_iterator<_InputIter>::value &&
117           !__is_forward_iterator<_InputIter>::value,
118            void
119        >::type
120        __construct_at_end(_InputIter __first, _InputIter __last);
121    template <class _ForwardIterator>
122        typename enable_if
123        <
124            __is_forward_iterator<_ForwardIterator>::value,
125            void
126        >::type
127        __construct_at_end(_ForwardIterator __first, _ForwardIterator __last);
128
129    _LIBCPP_INLINE_VISIBILITY void __destruct_at_begin(pointer __new_begin)
130        {__destruct_at_begin(__new_begin, is_trivially_destructible<value_type>());}
131        void __destruct_at_begin(pointer __new_begin, false_type);
132        void __destruct_at_begin(pointer __new_begin, true_type);
133
134    _LIBCPP_INLINE_VISIBILITY
135    void __destruct_at_end(pointer __new_last) _NOEXCEPT
136        {__destruct_at_end(__new_last, false_type());}
137    _LIBCPP_INLINE_VISIBILITY
138        void __destruct_at_end(pointer __new_last, false_type) _NOEXCEPT;
139    _LIBCPP_INLINE_VISIBILITY
140        void __destruct_at_end(pointer __new_last, true_type) _NOEXCEPT;
141
142    void swap(__split_buffer& __x)
143        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value||
144                   __is_nothrow_swappable<__alloc_rr>::value);
145
146    bool __invariants() const;
147
148private:
149    _LIBCPP_INLINE_VISIBILITY
150    void __move_assign_alloc(__split_buffer& __c, true_type)
151        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
152        {
153            __alloc() = _VSTD::move(__c.__alloc());
154        }
155
156    _LIBCPP_INLINE_VISIBILITY
157    void __move_assign_alloc(__split_buffer&, false_type) _NOEXCEPT
158        {}
159
160    _LIBCPP_INLINE_VISIBILITY
161    static void __swap_alloc(__alloc_rr& __x, __alloc_rr& __y)
162        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value||
163                   __is_nothrow_swappable<__alloc_rr>::value)
164        {__swap_alloc(__x, __y, integral_constant<bool,
165                      __alloc_traits::propagate_on_container_swap::value>());}
166
167    _LIBCPP_INLINE_VISIBILITY
168    static void __swap_alloc(__alloc_rr& __x, __alloc_rr& __y, true_type)
169        _NOEXCEPT_(__is_nothrow_swappable<__alloc_rr>::value)
170        {
171            using _VSTD::swap;
172            swap(__x, __y);
173        }
174
175    _LIBCPP_INLINE_VISIBILITY
176    static void __swap_alloc(__alloc_rr&, __alloc_rr&, false_type) _NOEXCEPT
177        {}
178};
179
180template <class _Tp, class _Allocator>
181bool
182__split_buffer<_Tp, _Allocator>::__invariants() const
183{
184    if (__first_ == nullptr)
185    {
186        if (__begin_ != nullptr)
187            return false;
188        if (__end_ != nullptr)
189            return false;
190        if (__end_cap() != nullptr)
191            return false;
192    }
193    else
194    {
195        if (__begin_ < __first_)
196            return false;
197        if (__end_ < __begin_)
198            return false;
199        if (__end_cap() < __end_)
200            return false;
201    }
202    return true;
203}
204
205//  Default constructs __n objects starting at __end_
206//  throws if construction throws
207//  Precondition:  __n > 0
208//  Precondition:  size() + __n <= capacity()
209//  Postcondition:  size() == size() + __n
210template <class _Tp, class _Allocator>
211void
212__split_buffer<_Tp, _Allocator>::__construct_at_end(size_type __n)
213{
214    __alloc_rr& __a = this->__alloc();
215    do
216    {
217        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_));
218        ++this->__end_;
219        --__n;
220    } while (__n > 0);
221}
222
223//  Copy constructs __n objects starting at __end_ from __x
224//  throws if construction throws
225//  Precondition:  __n > 0
226//  Precondition:  size() + __n <= capacity()
227//  Postcondition:  size() == old size() + __n
228//  Postcondition:  [i] == __x for all i in [size() - __n, __n)
229template <class _Tp, class _Allocator>
230void
231__split_buffer<_Tp, _Allocator>::__construct_at_end(size_type __n, const_reference __x)
232{
233    __alloc_rr& __a = this->__alloc();
234    do
235    {
236        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), __x);
237        ++this->__end_;
238        --__n;
239    } while (__n > 0);
240}
241
242template <class _Tp, class _Allocator>
243template <class _InputIter>
244typename enable_if
245<
246     __is_input_iterator<_InputIter>::value &&
247    !__is_forward_iterator<_InputIter>::value,
248    void
249>::type
250__split_buffer<_Tp, _Allocator>::__construct_at_end(_InputIter __first, _InputIter __last)
251{
252    __alloc_rr& __a = this->__alloc();
253    for (; __first != __last; ++__first)
254    {
255        if (__end_ == __end_cap())
256        {
257            size_type __old_cap = __end_cap() - __first_;
258            size_type __new_cap = _VSTD::max<size_type>(2 * __old_cap, 8);
259            __split_buffer __buf(__new_cap, 0, __a);
260            for (pointer __p = __begin_; __p != __end_; ++__p, ++__buf.__end_)
261                __alloc_traits::construct(__buf.__alloc(),
262                        _VSTD::__to_raw_pointer(__buf.__end_), _VSTD::move(*__p));
263            swap(__buf);
264        }
265        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), *__first);
266        ++this->__end_;
267    }
268}
269
270template <class _Tp, class _Allocator>
271template <class _ForwardIterator>
272typename enable_if
273<
274    __is_forward_iterator<_ForwardIterator>::value,
275    void
276>::type
277__split_buffer<_Tp, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last)
278{
279    __alloc_rr& __a = this->__alloc();
280    for (; __first != __last; ++__first)
281    {
282        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), *__first);
283        ++this->__end_;
284    }
285}
286
287template <class _Tp, class _Allocator>
288inline _LIBCPP_INLINE_VISIBILITY
289void
290__split_buffer<_Tp, _Allocator>::__destruct_at_begin(pointer __new_begin, false_type)
291{
292    while (__begin_ != __new_begin)
293        __alloc_traits::destroy(__alloc(), __to_raw_pointer(__begin_++));
294}
295
296template <class _Tp, class _Allocator>
297inline _LIBCPP_INLINE_VISIBILITY
298void
299__split_buffer<_Tp, _Allocator>::__destruct_at_begin(pointer __new_begin, true_type)
300{
301    __begin_ = __new_begin;
302}
303
304template <class _Tp, class _Allocator>
305inline _LIBCPP_INLINE_VISIBILITY
306void
307__split_buffer<_Tp, _Allocator>::__destruct_at_end(pointer __new_last, false_type) _NOEXCEPT
308{
309    while (__new_last != __end_)
310        __alloc_traits::destroy(__alloc(), __to_raw_pointer(--__end_));
311}
312
313template <class _Tp, class _Allocator>
314inline _LIBCPP_INLINE_VISIBILITY
315void
316__split_buffer<_Tp, _Allocator>::__destruct_at_end(pointer __new_last, true_type) _NOEXCEPT
317{
318    __end_ = __new_last;
319}
320
321template <class _Tp, class _Allocator>
322__split_buffer<_Tp, _Allocator>::__split_buffer(size_type __cap, size_type __start, __alloc_rr& __a)
323    : __end_cap_(nullptr, __a)
324{
325    __first_ = __cap != 0 ? __alloc_traits::allocate(__alloc(), __cap) : nullptr;
326    __begin_ = __end_ = __first_ + __start;
327    __end_cap() = __first_ + __cap;
328}
329
330template <class _Tp, class _Allocator>
331inline _LIBCPP_INLINE_VISIBILITY
332__split_buffer<_Tp, _Allocator>::__split_buffer()
333    _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
334    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr)
335{
336}
337
338template <class _Tp, class _Allocator>
339inline _LIBCPP_INLINE_VISIBILITY
340__split_buffer<_Tp, _Allocator>::__split_buffer(__alloc_rr& __a)
341    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr, __a)
342{
343}
344
345template <class _Tp, class _Allocator>
346inline _LIBCPP_INLINE_VISIBILITY
347__split_buffer<_Tp, _Allocator>::__split_buffer(const __alloc_rr& __a)
348    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr, __a)
349{
350}
351
352template <class _Tp, class _Allocator>
353__split_buffer<_Tp, _Allocator>::~__split_buffer()
354{
355    clear();
356    if (__first_)
357        __alloc_traits::deallocate(__alloc(), __first_, capacity());
358}
359
360#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
361
362template <class _Tp, class _Allocator>
363__split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c)
364    _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
365    : __first_(_VSTD::move(__c.__first_)),
366      __begin_(_VSTD::move(__c.__begin_)),
367      __end_(_VSTD::move(__c.__end_)),
368      __end_cap_(_VSTD::move(__c.__end_cap_))
369{
370    __c.__first_ = nullptr;
371    __c.__begin_ = nullptr;
372    __c.__end_ = nullptr;
373    __c.__end_cap() = nullptr;
374}
375
376template <class _Tp, class _Allocator>
377__split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c, const __alloc_rr& __a)
378    : __end_cap_(__a)
379{
380    if (__a == __c.__alloc())
381    {
382        __first_ = __c.__first_;
383        __begin_ = __c.__begin_;
384        __end_ = __c.__end_;
385        __end_cap() = __c.__end_cap();
386        __c.__first_ = nullptr;
387        __c.__begin_ = nullptr;
388        __c.__end_ = nullptr;
389        __c.__end_cap() = nullptr;
390    }
391    else
392    {
393        size_type __cap = __c.size();
394        __first_ = __alloc_traits::allocate(__alloc(), __cap);
395        __begin_ = __end_ = __first_;
396        __end_cap() = __first_ + __cap;
397        typedef move_iterator<iterator> _Ip;
398        __construct_at_end(_Ip(__c.begin()), _Ip(__c.end()));
399    }
400}
401
402template <class _Tp, class _Allocator>
403__split_buffer<_Tp, _Allocator>&
404__split_buffer<_Tp, _Allocator>::operator=(__split_buffer&& __c)
405    _NOEXCEPT_((__alloc_traits::propagate_on_container_move_assignment::value &&
406                is_nothrow_move_assignable<allocator_type>::value) ||
407               !__alloc_traits::propagate_on_container_move_assignment::value)
408{
409    clear();
410    shrink_to_fit();
411    __first_ = __c.__first_;
412    __begin_ = __c.__begin_;
413    __end_ = __c.__end_;
414    __end_cap() = __c.__end_cap();
415    __move_assign_alloc(__c,
416        integral_constant<bool,
417                          __alloc_traits::propagate_on_container_move_assignment::value>());
418    __c.__first_ = __c.__begin_ = __c.__end_ = __c.__end_cap() = nullptr;
419    return *this;
420}
421
422#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
423
424template <class _Tp, class _Allocator>
425void
426__split_buffer<_Tp, _Allocator>::swap(__split_buffer& __x)
427        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value||
428                   __is_nothrow_swappable<__alloc_rr>::value)
429{
430    _VSTD::swap(__first_, __x.__first_);
431    _VSTD::swap(__begin_, __x.__begin_);
432    _VSTD::swap(__end_, __x.__end_);
433    _VSTD::swap(__end_cap(), __x.__end_cap());
434    __swap_alloc(__alloc(), __x.__alloc());
435}
436
437template <class _Tp, class _Allocator>
438void
439__split_buffer<_Tp, _Allocator>::reserve(size_type __n)
440{
441    if (__n < capacity())
442    {
443        __split_buffer<value_type, __alloc_rr&> __t(__n, 0, __alloc());
444        __t.__construct_at_end(move_iterator<pointer>(__begin_),
445                               move_iterator<pointer>(__end_));
446        _VSTD::swap(__first_, __t.__first_);
447        _VSTD::swap(__begin_, __t.__begin_);
448        _VSTD::swap(__end_, __t.__end_);
449        _VSTD::swap(__end_cap(), __t.__end_cap());
450    }
451}
452
453template <class _Tp, class _Allocator>
454void
455__split_buffer<_Tp, _Allocator>::shrink_to_fit() _NOEXCEPT
456{
457    if (capacity() > size())
458    {
459#ifndef _LIBCPP_NO_EXCEPTIONS
460        try
461        {
462#endif  // _LIBCPP_NO_EXCEPTIONS
463            __split_buffer<value_type, __alloc_rr&> __t(size(), 0, __alloc());
464            __t.__construct_at_end(move_iterator<pointer>(__begin_),
465                                   move_iterator<pointer>(__end_));
466            __t.__end_ = __t.__begin_ + (__end_ - __begin_);
467            _VSTD::swap(__first_, __t.__first_);
468            _VSTD::swap(__begin_, __t.__begin_);
469            _VSTD::swap(__end_, __t.__end_);
470            _VSTD::swap(__end_cap(), __t.__end_cap());
471#ifndef _LIBCPP_NO_EXCEPTIONS
472        }
473        catch (...)
474        {
475        }
476#endif  // _LIBCPP_NO_EXCEPTIONS
477    }
478}
479
480template <class _Tp, class _Allocator>
481void
482__split_buffer<_Tp, _Allocator>::push_front(const_reference __x)
483{
484    if (__begin_ == __first_)
485    {
486        if (__end_ < __end_cap())
487        {
488            difference_type __d = __end_cap() - __end_;
489            __d = (__d + 1) / 2;
490            __begin_ = _VSTD::move_backward(__begin_, __end_, __end_ + __d);
491            __end_ += __d;
492        }
493        else
494        {
495            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1);
496            __split_buffer<value_type, __alloc_rr&> __t(__c, (__c + 3) / 4, __alloc());
497            __t.__construct_at_end(move_iterator<pointer>(__begin_),
498                                   move_iterator<pointer>(__end_));
499            _VSTD::swap(__first_, __t.__first_);
500            _VSTD::swap(__begin_, __t.__begin_);
501            _VSTD::swap(__end_, __t.__end_);
502            _VSTD::swap(__end_cap(), __t.__end_cap());
503        }
504    }
505    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__begin_-1), __x);
506    --__begin_;
507}
508
509#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
510
511template <class _Tp, class _Allocator>
512void
513__split_buffer<_Tp, _Allocator>::push_front(value_type&& __x)
514{
515    if (__begin_ == __first_)
516    {
517        if (__end_ < __end_cap())
518        {
519            difference_type __d = __end_cap() - __end_;
520            __d = (__d + 1) / 2;
521            __begin_ = _VSTD::move_backward(__begin_, __end_, __end_ + __d);
522            __end_ += __d;
523        }
524        else
525        {
526            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1);
527            __split_buffer<value_type, __alloc_rr&> __t(__c, (__c + 3) / 4, __alloc());
528            __t.__construct_at_end(move_iterator<pointer>(__begin_),
529                                   move_iterator<pointer>(__end_));
530            _VSTD::swap(__first_, __t.__first_);
531            _VSTD::swap(__begin_, __t.__begin_);
532            _VSTD::swap(__end_, __t.__end_);
533            _VSTD::swap(__end_cap(), __t.__end_cap());
534        }
535    }
536    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__begin_-1),
537            _VSTD::move(__x));
538    --__begin_;
539}
540
541#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
542
543template <class _Tp, class _Allocator>
544inline _LIBCPP_INLINE_VISIBILITY
545void
546__split_buffer<_Tp, _Allocator>::push_back(const_reference __x)
547{
548    if (__end_ == __end_cap())
549    {
550        if (__begin_ > __first_)
551        {
552            difference_type __d = __begin_ - __first_;
553            __d = (__d + 1) / 2;
554            __end_ = _VSTD::move(__begin_, __end_, __begin_ - __d);
555            __begin_ -= __d;
556        }
557        else
558        {
559            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1);
560            __split_buffer<value_type, __alloc_rr&> __t(__c, __c / 4, __alloc());
561            __t.__construct_at_end(move_iterator<pointer>(__begin_),
562                                   move_iterator<pointer>(__end_));
563            _VSTD::swap(__first_, __t.__first_);
564            _VSTD::swap(__begin_, __t.__begin_);
565            _VSTD::swap(__end_, __t.__end_);
566            _VSTD::swap(__end_cap(), __t.__end_cap());
567        }
568    }
569    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__end_), __x);
570    ++__end_;
571}
572
573#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
574
575template <class _Tp, class _Allocator>
576void
577__split_buffer<_Tp, _Allocator>::push_back(value_type&& __x)
578{
579    if (__end_ == __end_cap())
580    {
581        if (__begin_ > __first_)
582        {
583            difference_type __d = __begin_ - __first_;
584            __d = (__d + 1) / 2;
585            __end_ = _VSTD::move(__begin_, __end_, __begin_ - __d);
586            __begin_ -= __d;
587        }
588        else
589        {
590            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1);
591            __split_buffer<value_type, __alloc_rr&> __t(__c, __c / 4, __alloc());
592            __t.__construct_at_end(move_iterator<pointer>(__begin_),
593                                   move_iterator<pointer>(__end_));
594            _VSTD::swap(__first_, __t.__first_);
595            _VSTD::swap(__begin_, __t.__begin_);
596            _VSTD::swap(__end_, __t.__end_);
597            _VSTD::swap(__end_cap(), __t.__end_cap());
598        }
599    }
600    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__end_),
601            _VSTD::move(__x));
602    ++__end_;
603}
604
605#ifndef _LIBCPP_HAS_NO_VARIADICS
606
607template <class _Tp, class _Allocator>
608template <class... _Args>
609void
610__split_buffer<_Tp, _Allocator>::emplace_back(_Args&&... __args)
611{
612    if (__end_ == __end_cap())
613    {
614        if (__begin_ > __first_)
615        {
616            difference_type __d = __begin_ - __first_;
617            __d = (__d + 1) / 2;
618            __end_ = _VSTD::move(__begin_, __end_, __begin_ - __d);
619            __begin_ -= __d;
620        }
621        else
622        {
623            size_type __c = max<size_type>(2 * static_cast<size_t>(__end_cap() - __first_), 1);
624            __split_buffer<value_type, __alloc_rr&> __t(__c, __c / 4, __alloc());
625            __t.__construct_at_end(move_iterator<pointer>(__begin_),
626                                   move_iterator<pointer>(__end_));
627            _VSTD::swap(__first_, __t.__first_);
628            _VSTD::swap(__begin_, __t.__begin_);
629            _VSTD::swap(__end_, __t.__end_);
630            _VSTD::swap(__end_cap(), __t.__end_cap());
631        }
632    }
633    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__end_),
634                              _VSTD::forward<_Args>(__args)...);
635    ++__end_;
636}
637
638#endif  // _LIBCPP_HAS_NO_VARIADICS
639
640#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
641
642template <class _Tp, class _Allocator>
643inline _LIBCPP_INLINE_VISIBILITY
644void
645swap(__split_buffer<_Tp, _Allocator>& __x, __split_buffer<_Tp, _Allocator>& __y)
646        _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y)))
647{
648    __x.swap(__y);
649}
650
651
652_LIBCPP_END_NAMESPACE_STD
653
654#endif  // _LIBCPP_SPLIT_BUFFER
655