2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
18 * Nicholas Ormrod (njormrod)
19 * Andrei Alexandrescu (aalexandre)
21 * FBVector is Facebook's drop-in implementation of std::vector. It has special
22 * optimizations for use with relocatable types and jemalloc.
27 //=============================================================================
35 #include <type_traits>
38 #include <folly/FormatTraits.h>
39 #include <folly/Likely.h>
40 #include <folly/Malloc.h>
41 #include <folly/Traits.h>
43 #include <boost/operators.hpp>
45 //=============================================================================
46 // forward declaration
49 template <class T, class Allocator = std::allocator<T>>
53 //=============================================================================
56 #define FOLLY_FBV_UNROLL_PTR(first, last, OP) do { \
57 for (; (last) - (first) >= 4; (first) += 4) { \
63 for (; (first) != (last); ++(first)) OP((first)); \
66 //=============================================================================
67 ///////////////////////////////////////////////////////////////////////////////
71 ///////////////////////////////////////////////////////////////////////////////
75 template <class T, class Allocator>
76 class fbvector : private boost::totally_ordered<fbvector<T, Allocator>> {
78 //===========================================================================
79 //---------------------------------------------------------------------------
83 typedef std::allocator_traits<Allocator> A;
85 struct Impl : public Allocator {
87 typedef typename A::pointer pointer;
88 typedef typename A::size_type size_type;
94 Impl() : Allocator(), b_(nullptr), e_(nullptr), z_(nullptr) {}
95 /* implicit */ Impl(const Allocator& a)
96 : Allocator(a), b_(nullptr), e_(nullptr), z_(nullptr) {}
97 /* implicit */ Impl(Allocator&& a)
98 : Allocator(std::move(a)), b_(nullptr), e_(nullptr), z_(nullptr) {}
100 /* implicit */ Impl(size_type n, const Allocator& a = Allocator())
104 Impl(Impl&& other) noexcept
105 : Allocator(std::move(other)),
106 b_(other.b_), e_(other.e_), z_(other.z_)
107 { other.b_ = other.e_ = other.z_ = nullptr; }
115 // note that 'allocate' and 'deallocate' are inherited from Allocator
116 T* D_allocate(size_type n) {
117 if (usingStdAllocator::value) {
118 return static_cast<T*>(malloc(n * sizeof(T)));
120 return std::allocator_traits<Allocator>::allocate(*this, n);
124 void D_deallocate(T* p, size_type n) noexcept {
125 if (usingStdAllocator::value) {
128 std::allocator_traits<Allocator>::deallocate(*this, p, n);
133 void swapData(Impl& other) {
134 std::swap(b_, other.b_);
135 std::swap(e_, other.e_);
136 std::swap(z_, other.z_);
140 inline void destroy() noexcept {
142 // THIS DISPATCH CODE IS DUPLICATED IN fbvector::D_destroy_range_a.
143 // It has been inlined here for speed. It calls the static fbvector
144 // methods to perform the actual destruction.
145 if (usingStdAllocator::value) {
146 S_destroy_range(b_, e_);
148 S_destroy_range_a(*this, b_, e_);
151 D_deallocate(b_, z_ - b_);
155 void init(size_type n) {
156 if (UNLIKELY(n == 0)) {
157 b_ = e_ = z_ = nullptr;
159 size_type sz = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
166 void set(pointer newB, size_type newSize, size_type newCap) {
172 void reset(size_type newCap) {
181 void reset() { // same as reset(0)
183 b_ = e_ = z_ = nullptr;
187 static void swap(Impl& a, Impl& b) {
189 if (!usingStdAllocator::value) swap<Allocator>(a, b);
193 //===========================================================================
194 //---------------------------------------------------------------------------
195 // types and constants
198 typedef T value_type;
199 typedef value_type& reference;
200 typedef const value_type& const_reference;
202 typedef const T* const_iterator;
203 typedef size_t size_type;
204 typedef typename std::make_signed<size_type>::type difference_type;
205 typedef Allocator allocator_type;
206 typedef typename A::pointer pointer;
207 typedef typename A::const_pointer const_pointer;
208 typedef std::reverse_iterator<iterator> reverse_iterator;
209 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
213 typedef std::integral_constant<bool,
214 boost::has_trivial_copy_constructor<T>::value &&
215 sizeof(T) <= 16 // don't force large structures to be passed by value
216 > should_pass_by_value;
217 typedef typename std::conditional<
218 should_pass_by_value::value, T, const T&>::type VT;
219 typedef typename std::conditional<
220 should_pass_by_value::value, T, T&&>::type MT;
222 typedef std::integral_constant<bool,
223 std::is_same<Allocator, std::allocator<T>>::value> usingStdAllocator;
224 typedef std::integral_constant<bool,
225 usingStdAllocator::value ||
226 A::propagate_on_container_move_assignment::value> moveIsSwap;
228 //===========================================================================
229 //---------------------------------------------------------------------------
233 //---------------------------------------------------------------------------
236 T* M_allocate(size_type n) {
237 return impl_.D_allocate(n);
240 //---------------------------------------------------------------------------
243 void M_deallocate(T* p, size_type n) noexcept {
244 impl_.D_deallocate(p, n);
247 //---------------------------------------------------------------------------
250 // GCC is very sensitive to the exact way that construct is called. For
251 // that reason there are several different specializations of construct.
253 template <typename U, typename... Args>
254 void M_construct(U* p, Args&&... args) {
255 if (usingStdAllocator::value) {
256 new (p) U(std::forward<Args>(args)...);
258 std::allocator_traits<Allocator>::construct(
259 impl_, p, std::forward<Args>(args)...);
263 template <typename U, typename... Args>
264 static void S_construct(U* p, Args&&... args) {
265 new (p) U(std::forward<Args>(args)...);
268 template <typename U, typename... Args>
269 static void S_construct_a(Allocator& a, U* p, Args&&... args) {
270 std::allocator_traits<Allocator>::construct(
271 a, p, std::forward<Args>(args)...);
274 // scalar optimization
275 // TODO we can expand this optimization to: default copyable and assignable
276 template <typename U, typename Enable = typename
277 std::enable_if<std::is_scalar<U>::value>::type>
278 void M_construct(U* p, U arg) {
279 if (usingStdAllocator::value) {
282 std::allocator_traits<Allocator>::construct(impl_, p, arg);
286 template <typename U, typename Enable = typename
287 std::enable_if<std::is_scalar<U>::value>::type>
288 static void S_construct(U* p, U arg) {
292 template <typename U, typename Enable = typename
293 std::enable_if<std::is_scalar<U>::value>::type>
294 static void S_construct_a(Allocator& a, U* p, U arg) {
295 std::allocator_traits<Allocator>::construct(a, p, arg);
298 // const& optimization
299 template <typename U, typename Enable = typename
300 std::enable_if<!std::is_scalar<U>::value>::type>
301 void M_construct(U* p, const U& value) {
302 if (usingStdAllocator::value) {
305 std::allocator_traits<Allocator>::construct(impl_, p, value);
309 template <typename U, typename Enable = typename
310 std::enable_if<!std::is_scalar<U>::value>::type>
311 static void S_construct(U* p, const U& value) {
315 template <typename U, typename Enable = typename
316 std::enable_if<!std::is_scalar<U>::value>::type>
317 static void S_construct_a(Allocator& a, U* p, const U& value) {
318 std::allocator_traits<Allocator>::construct(a, p, value);
321 //---------------------------------------------------------------------------
324 void M_destroy(T* p) noexcept {
325 if (usingStdAllocator::value) {
326 if (!boost::has_trivial_destructor<T>::value) p->~T();
328 std::allocator_traits<Allocator>::destroy(impl_, p);
332 //===========================================================================
333 //---------------------------------------------------------------------------
334 // algorithmic helpers
337 //---------------------------------------------------------------------------
341 void M_destroy_range_e(T* pos) noexcept {
342 D_destroy_range_a(pos, impl_.e_);
347 // THIS DISPATCH CODE IS DUPLICATED IN IMPL. SEE IMPL FOR DETAILS.
348 void D_destroy_range_a(T* first, T* last) noexcept {
349 if (usingStdAllocator::value) {
350 S_destroy_range(first, last);
352 S_destroy_range_a(impl_, first, last);
357 static void S_destroy_range_a(Allocator& a, T* first, T* last) noexcept {
358 for (; first != last; ++first)
359 std::allocator_traits<Allocator>::destroy(a, first);
363 static void S_destroy_range(T* first, T* last) noexcept {
364 if (!boost::has_trivial_destructor<T>::value) {
365 // EXPERIMENTAL DATA on fbvector<vector<int>> (where each vector<int> has
367 // The unrolled version seems to work faster for small to medium sized
368 // fbvectors. It gets a 10% speedup on fbvectors of size 1024, 64, and
370 // The simple loop version seems to work faster for large fbvectors. The
371 // unrolled version is about 6% slower on fbvectors on size 16384.
372 // The two methods seem tied for very large fbvectors. The unrolled
373 // version is about 0.5% slower on size 262144.
375 // for (; first != last; ++first) first->~T();
376 #define FOLLY_FBV_OP(p) (p)->~T()
377 FOLLY_FBV_UNROLL_PTR(first, last, FOLLY_FBV_OP)
382 //---------------------------------------------------------------------------
383 // uninitialized_fill_n
386 void M_uninitialized_fill_n_e(size_type sz) {
387 D_uninitialized_fill_n_a(impl_.e_, sz);
391 void M_uninitialized_fill_n_e(size_type sz, VT value) {
392 D_uninitialized_fill_n_a(impl_.e_, sz, value);
397 void D_uninitialized_fill_n_a(T* dest, size_type sz) {
398 if (usingStdAllocator::value) {
399 S_uninitialized_fill_n(dest, sz);
401 S_uninitialized_fill_n_a(impl_, dest, sz);
405 void D_uninitialized_fill_n_a(T* dest, size_type sz, VT value) {
406 if (usingStdAllocator::value) {
407 S_uninitialized_fill_n(dest, sz, value);
409 S_uninitialized_fill_n_a(impl_, dest, sz, value);
414 template <typename... Args>
415 static void S_uninitialized_fill_n_a(Allocator& a, T* dest,
416 size_type sz, Args&&... args) {
421 std::allocator_traits<Allocator>::construct(a, b,
422 std::forward<Args>(args)...);
424 S_destroy_range_a(a, dest, b);
430 static void S_uninitialized_fill_n(T* dest, size_type n) {
431 if (folly::IsZeroInitializable<T>::value) {
432 std::memset(dest, 0, sizeof(T) * n);
437 for (; b != e; ++b) S_construct(b);
440 for (; b >= dest; --b) b->~T();
446 static void S_uninitialized_fill_n(T* dest, size_type n, const T& value) {
450 for (; b != e; ++b) S_construct(b, value);
452 S_destroy_range(dest, b);
457 //---------------------------------------------------------------------------
458 // uninitialized_copy
460 // it is possible to add an optimization for the case where
461 // It = move(T*) and IsRelocatable<T> and Is0Initiailizable<T>
464 template <typename It>
465 void M_uninitialized_copy_e(It first, It last) {
466 D_uninitialized_copy_a(impl_.e_, first, last);
467 impl_.e_ += std::distance(first, last);
470 template <typename It>
471 void M_uninitialized_move_e(It first, It last) {
472 D_uninitialized_move_a(impl_.e_, first, last);
473 impl_.e_ += std::distance(first, last);
477 template <typename It>
478 void D_uninitialized_copy_a(T* dest, It first, It last) {
479 if (usingStdAllocator::value) {
480 if (folly::IsTriviallyCopyable<T>::value) {
481 S_uninitialized_copy_bits(dest, first, last);
483 S_uninitialized_copy(dest, first, last);
486 S_uninitialized_copy_a(impl_, dest, first, last);
490 template <typename It>
491 void D_uninitialized_move_a(T* dest, It first, It last) {
492 D_uninitialized_copy_a(dest,
493 std::make_move_iterator(first), std::make_move_iterator(last));
497 template <typename It>
499 S_uninitialized_copy_a(Allocator& a, T* dest, It first, It last) {
502 for (; first != last; ++first, ++b)
503 std::allocator_traits<Allocator>::construct(a, b, *first);
505 S_destroy_range_a(a, dest, b);
511 template <typename It>
512 static void S_uninitialized_copy(T* dest, It first, It last) {
515 for (; first != last; ++first, ++b)
516 S_construct(b, *first);
518 S_destroy_range(dest, b);
524 S_uninitialized_copy_bits(T* dest, const T* first, const T* last) {
526 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
531 S_uninitialized_copy_bits(T* dest, std::move_iterator<T*> first,
532 std::move_iterator<T*> last) {
533 T* bFirst = first.base();
534 T* bLast = last.base();
535 if (bLast != bFirst) {
536 std::memcpy((void*)dest, (void*)bFirst, (bLast - bFirst) * sizeof(T));
540 template <typename It>
542 S_uninitialized_copy_bits(T* dest, It first, It last) {
543 S_uninitialized_copy(dest, first, last);
546 //---------------------------------------------------------------------------
549 // This function is "unsafe": it assumes that the iterator can be advanced at
550 // least n times. However, as a private function, that unsafety is managed
551 // wholly by fbvector itself.
553 template <typename It>
554 static It S_copy_n(T* dest, It first, size_type n) {
556 for (; dest != e; ++dest, ++first) *dest = *first;
560 static const T* S_copy_n(T* dest, const T* first, size_type n) {
561 if (folly::IsTriviallyCopyable<T>::value) {
562 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
565 return S_copy_n<const T*>(dest, first, n);
569 static std::move_iterator<T*>
570 S_copy_n(T* dest, std::move_iterator<T*> mIt, size_type n) {
571 if (folly::IsTriviallyCopyable<T>::value) {
572 T* first = mIt.base();
573 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
574 return std::make_move_iterator(first + n);
576 return S_copy_n<std::move_iterator<T*>>(dest, mIt, n);
580 //===========================================================================
581 //---------------------------------------------------------------------------
582 // relocation helpers
585 // Relocation is divided into three parts:
588 // Performs the actual movement of data from point a to point b.
591 // Destroys the old data.
594 // Destoys the new data and restores the old data.
596 // The three steps are used because there may be an exception after part 1
597 // has completed. If that is the case, then relocate_undo can nullify the
598 // initial move. Otherwise, relocate_done performs the last bit of tidying
601 // The relocation trio may use either memcpy, move, or copy. It is decided
602 // by the following case statement:
604 // IsRelocatable && usingStdAllocator -> memcpy
605 // has_nothrow_move && usingStdAllocator -> move
606 // cannot copy -> move
609 // If the class is non-copyable then it must be movable. However, if the
610 // move constructor is not noexcept, i.e. an error could be thrown, then
611 // relocate_undo will be unable to restore the old data, for fear of a
612 // second exception being thrown. This is a known and unavoidable
613 // deficiency. In lieu of a strong exception guarantee, relocate_undo does
614 // the next best thing: it provides a weak exception guarantee by
615 // destorying the new data, but leaving the old data in an indeterminate
616 // state. Note that that indeterminate state will be valid, since the
617 // old data has not been destroyed; it has merely been the source of a
618 // move, which is required to leave the source in a valid state.
621 void M_relocate(T* newB) {
622 relocate_move(newB, impl_.b_, impl_.e_);
623 relocate_done(newB, impl_.b_, impl_.e_);
626 // dispatch type trait
627 typedef std::integral_constant<bool,
628 folly::IsRelocatable<T>::value && usingStdAllocator::value
629 > relocate_use_memcpy;
631 typedef std::integral_constant<bool,
632 (std::is_nothrow_move_constructible<T>::value
633 && usingStdAllocator::value)
634 || !std::is_copy_constructible<T>::value
638 void relocate_move(T* dest, T* first, T* last) {
639 relocate_move_or_memcpy(dest, first, last, relocate_use_memcpy());
642 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::true_type) {
643 if (first != nullptr) {
644 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
648 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::false_type) {
649 relocate_move_or_copy(dest, first, last, relocate_use_move());
652 void relocate_move_or_copy(T* dest, T* first, T* last, std::true_type) {
653 D_uninitialized_move_a(dest, first, last);
656 void relocate_move_or_copy(T* dest, T* first, T* last, std::false_type) {
657 D_uninitialized_copy_a(dest, first, last);
661 void relocate_done(T* /*dest*/, T* first, T* last) noexcept {
662 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
663 // used memcpy; data has been relocated, do not call destructor
665 D_destroy_range_a(first, last);
670 void relocate_undo(T* dest, T* first, T* last) noexcept {
671 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
672 // used memcpy, old data is still valid, nothing to do
673 } else if (std::is_nothrow_move_constructible<T>::value &&
674 usingStdAllocator::value) {
675 // noexcept move everything back, aka relocate_move
676 relocate_move(first, dest, dest + (last - first));
677 } else if (!std::is_copy_constructible<T>::value) {
679 D_destroy_range_a(dest, dest + (last - first));
681 // used copy, old data is still valid
682 D_destroy_range_a(dest, dest + (last - first));
687 //===========================================================================
688 //---------------------------------------------------------------------------
689 // construct/copy/destroy
692 fbvector() = default;
694 explicit fbvector(const Allocator& a) : impl_(a) {}
696 explicit fbvector(size_type n, const Allocator& a = Allocator())
698 { M_uninitialized_fill_n_e(n); }
700 fbvector(size_type n, VT value, const Allocator& a = Allocator())
702 { M_uninitialized_fill_n_e(n, value); }
704 template <class It, class Category = typename
705 std::iterator_traits<It>::iterator_category>
706 fbvector(It first, It last, const Allocator& a = Allocator())
707 : fbvector(first, last, a, Category()) {}
709 fbvector(const fbvector& other)
710 : impl_(other.size(), A::select_on_container_copy_construction(other.impl_))
711 { M_uninitialized_copy_e(other.begin(), other.end()); }
713 fbvector(fbvector&& other) noexcept : impl_(std::move(other.impl_)) {}
715 fbvector(const fbvector& other, const Allocator& a)
716 : fbvector(other.begin(), other.end(), a) {}
718 /* may throw */ fbvector(fbvector&& other, const Allocator& a) : impl_(a) {
719 if (impl_ == other.impl_) {
720 impl_.swapData(other.impl_);
722 impl_.init(other.size());
723 M_uninitialized_move_e(other.begin(), other.end());
727 fbvector(std::initializer_list<T> il, const Allocator& a = Allocator())
728 : fbvector(il.begin(), il.end(), a) {}
730 ~fbvector() = default; // the cleanup occurs in impl_
732 fbvector& operator=(const fbvector& other) {
733 if (UNLIKELY(this == &other)) return *this;
735 if (!usingStdAllocator::value &&
736 A::propagate_on_container_copy_assignment::value) {
737 if (impl_ != other.impl_) {
738 // can't use other's different allocator to clean up self
741 (Allocator&)impl_ = (Allocator&)other.impl_;
744 assign(other.begin(), other.end());
748 fbvector& operator=(fbvector&& other) {
749 if (UNLIKELY(this == &other)) return *this;
750 moveFrom(std::move(other), moveIsSwap());
754 fbvector& operator=(std::initializer_list<T> il) {
755 assign(il.begin(), il.end());
759 template <class It, class Category = typename
760 std::iterator_traits<It>::iterator_category>
761 void assign(It first, It last) {
762 assign(first, last, Category());
765 void assign(size_type n, VT value) {
766 if (n > capacity()) {
767 // Not enough space. Do not reserve in place, since we will
768 // discard the old values anyways.
769 if (dataIsInternalAndNotVT(value)) {
770 T copy(std::move(value));
772 M_uninitialized_fill_n_e(n, copy);
775 M_uninitialized_fill_n_e(n, value);
777 } else if (n <= size()) {
778 auto newE = impl_.b_ + n;
779 std::fill(impl_.b_, newE, value);
780 M_destroy_range_e(newE);
782 std::fill(impl_.b_, impl_.e_, value);
783 M_uninitialized_fill_n_e(n - size(), value);
787 void assign(std::initializer_list<T> il) {
788 assign(il.begin(), il.end());
791 allocator_type get_allocator() const noexcept {
797 // contract dispatch for iterator types fbvector(It first, It last)
798 template <class ForwardIterator>
799 fbvector(ForwardIterator first, ForwardIterator last,
800 const Allocator& a, std::forward_iterator_tag)
801 : impl_(std::distance(first, last), a)
802 { M_uninitialized_copy_e(first, last); }
804 template <class InputIterator>
805 fbvector(InputIterator first, InputIterator last,
806 const Allocator& a, std::input_iterator_tag)
808 { for (; first != last; ++first) emplace_back(*first); }
810 // contract dispatch for allocator movement in operator=(fbvector&&)
812 moveFrom(fbvector&& other, std::true_type) {
813 swap(impl_, other.impl_);
815 void moveFrom(fbvector&& other, std::false_type) {
816 if (impl_ == other.impl_) {
817 impl_.swapData(other.impl_);
819 impl_.reset(other.size());
820 M_uninitialized_move_e(other.begin(), other.end());
824 // contract dispatch for iterator types in assign(It first, It last)
825 template <class ForwardIterator>
826 void assign(ForwardIterator first, ForwardIterator last,
827 std::forward_iterator_tag) {
828 const size_t newSize = std::distance(first, last);
829 if (newSize > capacity()) {
830 impl_.reset(newSize);
831 M_uninitialized_copy_e(first, last);
832 } else if (newSize <= size()) {
833 auto newEnd = std::copy(first, last, impl_.b_);
834 M_destroy_range_e(newEnd);
836 auto mid = S_copy_n(impl_.b_, first, size());
837 M_uninitialized_copy_e<decltype(last)>(mid, last);
841 template <class InputIterator>
842 void assign(InputIterator first, InputIterator last,
843 std::input_iterator_tag) {
845 for (; first != last && p != impl_.e_; ++first, ++p) {
849 M_destroy_range_e(p);
851 for (; first != last; ++first) emplace_back(*first);
855 // contract dispatch for aliasing under VT optimization
856 bool dataIsInternalAndNotVT(const T& t) {
857 if (should_pass_by_value::value) return false;
858 return dataIsInternal(t);
860 bool dataIsInternal(const T& t) {
861 return UNLIKELY(impl_.b_ <= std::addressof(t) &&
862 std::addressof(t) < impl_.e_);
866 //===========================================================================
867 //---------------------------------------------------------------------------
871 iterator begin() noexcept {
874 const_iterator begin() const noexcept {
877 iterator end() noexcept {
880 const_iterator end() const noexcept {
883 reverse_iterator rbegin() noexcept {
884 return reverse_iterator(end());
886 const_reverse_iterator rbegin() const noexcept {
887 return const_reverse_iterator(end());
889 reverse_iterator rend() noexcept {
890 return reverse_iterator(begin());
892 const_reverse_iterator rend() const noexcept {
893 return const_reverse_iterator(begin());
896 const_iterator cbegin() const noexcept {
899 const_iterator cend() const noexcept {
902 const_reverse_iterator crbegin() const noexcept {
903 return const_reverse_iterator(end());
905 const_reverse_iterator crend() const noexcept {
906 return const_reverse_iterator(begin());
909 //===========================================================================
910 //---------------------------------------------------------------------------
914 size_type size() const noexcept {
915 return impl_.e_ - impl_.b_;
918 size_type max_size() const noexcept {
919 // good luck gettin' there
920 return ~size_type(0);
923 void resize(size_type n) {
925 M_destroy_range_e(impl_.b_ + n);
928 M_uninitialized_fill_n_e(n - size());
932 void resize(size_type n, VT t) {
934 M_destroy_range_e(impl_.b_ + n);
935 } else if (dataIsInternalAndNotVT(t) && n > capacity()) {
938 M_uninitialized_fill_n_e(n - size(), copy);
941 M_uninitialized_fill_n_e(n - size(), t);
945 size_type capacity() const noexcept {
946 return impl_.z_ - impl_.b_;
949 bool empty() const noexcept {
950 return impl_.b_ == impl_.e_;
953 void reserve(size_type n) {
954 if (n <= capacity()) return;
955 if (impl_.b_ && reserve_in_place(n)) return;
957 auto newCap = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
958 auto newB = M_allocate(newCap);
962 M_deallocate(newB, newCap);
966 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
967 impl_.z_ = newB + newCap;
968 impl_.e_ = newB + (impl_.e_ - impl_.b_);
972 void shrink_to_fit() noexcept {
978 auto const newCapacityBytes = folly::goodMallocSize(size() * sizeof(T));
979 auto const newCap = newCapacityBytes / sizeof(T);
980 auto const oldCap = capacity();
982 if (newCap >= oldCap) return;
985 // xallocx() will shrink to precisely newCapacityBytes (which was generated
986 // by goodMallocSize()) if it successfully shrinks in place.
987 if ((usingJEMalloc() && usingStdAllocator::value) &&
988 newCapacityBytes >= folly::jemallocMinInPlaceExpandable &&
989 xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
990 impl_.z_ += newCap - oldCap;
992 T* newB; // intentionally uninitialized
994 newB = M_allocate(newCap);
998 M_deallocate(newB, newCap);
999 return; // swallow the error
1005 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
1006 impl_.z_ = newB + newCap;
1007 impl_.e_ = newB + (impl_.e_ - impl_.b_);
1014 bool reserve_in_place(size_type n) {
1015 if (!usingStdAllocator::value || !usingJEMalloc()) return false;
1017 // jemalloc can never grow in place blocks smaller than 4096 bytes.
1018 if ((impl_.z_ - impl_.b_) * sizeof(T) <
1019 folly::jemallocMinInPlaceExpandable) return false;
1021 auto const newCapacityBytes = folly::goodMallocSize(n * sizeof(T));
1023 if (xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
1024 impl_.z_ = impl_.b_ + newCapacityBytes / sizeof(T);
1030 //===========================================================================
1031 //---------------------------------------------------------------------------
1035 reference operator[](size_type n) {
1039 const_reference operator[](size_type n) const {
1043 const_reference at(size_type n) const {
1044 if (UNLIKELY(n >= size())) {
1045 throw std::out_of_range("fbvector: index is greater than size.");
1049 reference at(size_type n) {
1050 auto const& cThis = *this;
1051 return const_cast<reference>(cThis.at(n));
1057 const_reference front() const {
1063 return impl_.e_[-1];
1065 const_reference back() const {
1067 return impl_.e_[-1];
1070 //===========================================================================
1071 //---------------------------------------------------------------------------
1075 T* data() noexcept {
1078 const T* data() const noexcept {
1082 //===========================================================================
1083 //---------------------------------------------------------------------------
1084 // modifiers (common)
1087 template <class... Args>
1088 void emplace_back(Args&&... args) {
1089 if (impl_.e_ != impl_.z_) {
1090 M_construct(impl_.e_, std::forward<Args>(args)...);
1093 emplace_back_aux(std::forward<Args>(args)...);
1098 push_back(const T& value) {
1099 if (impl_.e_ != impl_.z_) {
1100 M_construct(impl_.e_, value);
1103 emplace_back_aux(value);
1108 push_back(T&& value) {
1109 if (impl_.e_ != impl_.z_) {
1110 M_construct(impl_.e_, std::move(value));
1113 emplace_back_aux(std::move(value));
1120 M_destroy(impl_.e_);
1123 void swap(fbvector& other) noexcept {
1124 if (!usingStdAllocator::value &&
1125 A::propagate_on_container_swap::value)
1126 swap(impl_, other.impl_);
1127 else impl_.swapData(other.impl_);
1130 void clear() noexcept {
1131 M_destroy_range_e(impl_.b_);
1136 // std::vector implements a similar function with a different growth
1137 // strategy: empty() ? 1 : capacity() * 2.
1139 // fbvector grows differently on two counts:
1142 // Instead of growing to size 1 from empty, fbvector allocates at least
1143 // 64 bytes. You may still use reserve to reserve a lesser amount of
1146 // For medium-sized vectors, the growth strategy is 1.5x. See the docs
1148 // This does not apply to very small or very large fbvectors. This is a
1150 // A nice addition to fbvector would be the capability of having a user-
1151 // defined growth strategy, probably as part of the allocator.
1154 size_type computePushBackCapacity() const {
1155 if (capacity() == 0) {
1156 return std::max(64 / sizeof(T), size_type(1));
1158 if (capacity() < folly::jemallocMinInPlaceExpandable / sizeof(T)) {
1159 return capacity() * 2;
1161 if (capacity() > 4096 * 32 / sizeof(T)) {
1162 return capacity() * 2;
1164 return (capacity() * 3 + 1) / 2;
1167 template <class... Args>
1168 void emplace_back_aux(Args&&... args);
1170 //===========================================================================
1171 //---------------------------------------------------------------------------
1172 // modifiers (erase)
1175 iterator erase(const_iterator position) {
1176 return erase(position, position + 1);
1179 iterator erase(const_iterator first, const_iterator last) {
1180 assert(isValid(first) && isValid(last));
1181 assert(first <= last);
1182 if (first != last) {
1183 if (last == end()) {
1184 M_destroy_range_e((iterator)first);
1186 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1187 D_destroy_range_a((iterator)first, (iterator)last);
1188 if (last - first >= cend() - last) {
1189 std::memcpy((void*)first, (void*)last, (cend() - last) * sizeof(T));
1191 std::memmove((iterator)first, last, (cend() - last) * sizeof(T));
1193 impl_.e_ -= (last - first);
1195 std::copy(std::make_move_iterator((iterator)last),
1196 std::make_move_iterator(end()), (iterator)first);
1197 auto newEnd = impl_.e_ - std::distance(first, last);
1198 M_destroy_range_e(newEnd);
1202 return (iterator)first;
1205 //===========================================================================
1206 //---------------------------------------------------------------------------
1207 // modifiers (insert)
1208 private: // we have the private section first because it defines some macros
1210 bool isValid(const_iterator it) {
1211 return cbegin() <= it && it <= cend();
1214 size_type computeInsertCapacity(size_type n) {
1215 size_type nc = std::max(computePushBackCapacity(), size() + n);
1216 size_type ac = folly::goodMallocSize(nc * sizeof(T)) / sizeof(T);
1220 //---------------------------------------------------------------------------
1222 // make_window takes an fbvector, and creates an uninitialized gap (a
1223 // window) at the given position, of the given size. The fbvector must
1224 // have enough capacity.
1226 // Explanation by picture.
1230 // make_window here of size 3
1234 // If something goes wrong and the window must be destroyed, use
1235 // undo_window to provide a weak exception guarantee. It destroys
1240 //---------------------------------------------------------------------------
1242 // wrap_frame takes an inverse window and relocates an fbvector around it.
1243 // The fbvector must have at least as many elements as the left ledge.
1245 // Explanation by picture.
1248 // fbvector: inverse window:
1249 // 123456789______ _____abcde_______
1253 // _______________ 12345abcde6789___
1255 //---------------------------------------------------------------------------
1257 // insert_use_fresh_memory returns true iff the fbvector should use a fresh
1258 // block of memory for the insertion. If the fbvector does not have enough
1259 // spare capacity, then it must return true. Otherwise either true or false
1262 //---------------------------------------------------------------------------
1264 // These three functions, make_window, wrap_frame, and
1265 // insert_use_fresh_memory, can be combined into a uniform interface.
1266 // Since that interface involves a lot of case-work, it is built into
1267 // some macros: FOLLY_FBVECTOR_INSERT_(PRE|START|TRY|END)
1268 // Macros are used in an attempt to let GCC perform better optimizations,
1269 // especially control flow optimization.
1272 //---------------------------------------------------------------------------
1275 void make_window(iterator position, size_type n) {
1276 // The result is guaranteed to be non-negative, so use an unsigned type:
1277 size_type tail = std::distance(position, impl_.e_);
1280 relocate_move(position + n, position, impl_.e_);
1281 relocate_done(position + n, position, impl_.e_);
1284 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1285 std::memmove(position + n, position, tail * sizeof(T));
1288 D_uninitialized_move_a(impl_.e_, impl_.e_ - n, impl_.e_);
1290 std::copy_backward(std::make_move_iterator(position),
1291 std::make_move_iterator(impl_.e_ - n), impl_.e_);
1293 D_destroy_range_a(impl_.e_ - n, impl_.e_ + n);
1298 D_destroy_range_a(position, position + n);
1303 void undo_window(iterator position, size_type n) noexcept {
1304 D_destroy_range_a(position + n, impl_.e_);
1305 impl_.e_ = position;
1308 //---------------------------------------------------------------------------
1311 void wrap_frame(T* ledge, size_type idx, size_type n) {
1312 assert(size() >= idx);
1315 relocate_move(ledge, impl_.b_, impl_.b_ + idx);
1317 relocate_move(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1319 relocate_undo(ledge, impl_.b_, impl_.b_ + idx);
1322 relocate_done(ledge, impl_.b_, impl_.b_ + idx);
1323 relocate_done(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1326 //---------------------------------------------------------------------------
1329 bool insert_use_fresh(bool at_end, size_type n) {
1331 if (size() + n <= capacity()) return false;
1332 if (reserve_in_place(size() + n)) return false;
1336 if (size() + n > capacity()) return true;
1341 //---------------------------------------------------------------------------
1344 #define FOLLY_FBVECTOR_INSERT_PRE(cpos, n) \
1345 if (n == 0) return (iterator)cpos; \
1346 bool at_end = cpos == cend(); \
1347 bool fresh = insert_use_fresh(at_end, n); \
1351 // check for internal data (technically not required by the standard)
1353 #define FOLLY_FBVECTOR_INSERT_START(cpos, n) \
1355 assert(isValid(cpos)); \
1357 T* position = const_cast<T*>(cpos); \
1358 size_type idx = std::distance(impl_.b_, position); \
1360 size_type newCap; /* intentionally uninitialized */ \
1363 newCap = computeInsertCapacity(n); \
1364 b = M_allocate(newCap); \
1367 make_window(position, n); \
1374 T* start = b + idx; \
1378 // construct the inserted elements
1380 #define FOLLY_FBVECTOR_INSERT_TRY(cpos, n) \
1383 M_deallocate(b, newCap); \
1386 undo_window(position, n); \
1396 wrap_frame(b, idx, n); \
1400 // delete the inserted elements (exception has been thrown)
1402 #define FOLLY_FBVECTOR_INSERT_END(cpos, n) \
1403 M_deallocate(b, newCap); \
1406 if (impl_.b_) M_deallocate(impl_.b_, capacity()); \
1407 impl_.set(b, size() + n, newCap); \
1408 return impl_.b_ + idx; \
1413 //---------------------------------------------------------------------------
1417 template <class... Args>
1418 iterator emplace(const_iterator cpos, Args&&... args) {
1419 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1420 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1421 M_construct(start, std::forward<Args>(args)...);
1422 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1424 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1427 iterator insert(const_iterator cpos, const T& value) {
1428 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1429 if (dataIsInternal(value)) return insert(cpos, T(value));
1430 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1431 M_construct(start, value);
1432 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1434 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1437 iterator insert(const_iterator cpos, T&& value) {
1438 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1439 if (dataIsInternal(value)) return insert(cpos, T(std::move(value)));
1440 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1441 M_construct(start, std::move(value));
1442 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1444 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1447 iterator insert(const_iterator cpos, size_type n, VT value) {
1448 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1449 if (dataIsInternalAndNotVT(value)) return insert(cpos, n, T(value));
1450 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1451 D_uninitialized_fill_n_a(start, n, value);
1452 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1453 D_destroy_range_a(start, start + n);
1454 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1457 template <class It, class Category = typename
1458 std::iterator_traits<It>::iterator_category>
1459 iterator insert(const_iterator cpos, It first, It last) {
1460 return insert(cpos, first, last, Category());
1463 iterator insert(const_iterator cpos, std::initializer_list<T> il) {
1464 return insert(cpos, il.begin(), il.end());
1467 //---------------------------------------------------------------------------
1468 // insert dispatch for iterator types
1471 template <class FIt>
1472 iterator insert(const_iterator cpos, FIt first, FIt last,
1473 std::forward_iterator_tag) {
1474 size_type n = std::distance(first, last);
1475 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1476 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1477 D_uninitialized_copy_a(start, first, last);
1478 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1479 D_destroy_range_a(start, start + n);
1480 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1483 template <class IIt>
1484 iterator insert(const_iterator cpos, IIt first, IIt last,
1485 std::input_iterator_tag) {
1486 T* position = const_cast<T*>(cpos);
1487 assert(isValid(position));
1488 size_type idx = std::distance(begin(), position);
1490 fbvector storage(std::make_move_iterator(position),
1491 std::make_move_iterator(end()),
1492 A::select_on_container_copy_construction(impl_));
1493 M_destroy_range_e(position);
1494 for (; first != last; ++first) emplace_back(*first);
1495 insert(cend(), std::make_move_iterator(storage.begin()),
1496 std::make_move_iterator(storage.end()));
1497 return impl_.b_ + idx;
1500 //===========================================================================
1501 //---------------------------------------------------------------------------
1502 // lexicographical functions (others from boost::totally_ordered superclass)
1505 bool operator==(const fbvector& other) const {
1506 return size() == other.size() && std::equal(begin(), end(), other.begin());
1509 bool operator<(const fbvector& other) const {
1510 return std::lexicographical_compare(
1511 begin(), end(), other.begin(), other.end());
1514 //===========================================================================
1515 //---------------------------------------------------------------------------
1519 template <class _T, class _A>
1520 friend _T* relinquish(fbvector<_T, _A>&);
1522 template <class _T, class _A>
1523 friend void attach(fbvector<_T, _A>&, _T* data, size_t sz, size_t cap);
1525 }; // class fbvector
1528 //=============================================================================
1529 //-----------------------------------------------------------------------------
1530 // outlined functions (gcc, you finicky compiler you)
1532 template <typename T, typename Allocator>
1533 template <class... Args>
1534 void fbvector<T, Allocator>::emplace_back_aux(Args&&... args) {
1535 size_type byte_sz = folly::goodMallocSize(
1536 computePushBackCapacity() * sizeof(T));
1537 if (usingStdAllocator::value
1539 && ((impl_.z_ - impl_.b_) * sizeof(T) >=
1540 folly::jemallocMinInPlaceExpandable)) {
1541 // Try to reserve in place.
1542 // Ask xallocx to allocate in place at least size()+1 and at most sz space.
1543 // xallocx will allocate as much as possible within that range, which
1544 // is the best possible outcome: if sz space is available, take it all,
1545 // otherwise take as much as possible. If nothing is available, then fail.
1546 // In this fashion, we never relocate if there is a possibility of
1547 // expanding in place, and we never reallocate by less than the desired
1548 // amount unless we cannot expand further. Hence we will not reallocate
1549 // sub-optimally twice in a row (modulo the blocking memory being freed).
1550 size_type lower = folly::goodMallocSize(sizeof(T) + size() * sizeof(T));
1551 size_type upper = byte_sz;
1552 size_type extra = upper - lower;
1557 if ((actual = xallocx(p, lower, extra, 0)) >= lower) {
1558 impl_.z_ = impl_.b_ + actual / sizeof(T);
1559 M_construct(impl_.e_, std::forward<Args>(args)...);
1565 // Reallocation failed. Perform a manual relocation.
1566 size_type sz = byte_sz / sizeof(T);
1567 auto newB = M_allocate(sz);
1568 auto newE = newB + size();
1570 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1571 // For linear memory access, relocate before construction.
1572 // By the test condition, relocate is noexcept.
1573 // Note that there is no cleanup to do if M_construct throws - that's
1574 // one of the beauties of relocation.
1575 // Benchmarks for this code have high variance, and seem to be close.
1576 relocate_move(newB, impl_.b_, impl_.e_);
1577 M_construct(newE, std::forward<Args>(args)...);
1580 M_construct(newE, std::forward<Args>(args)...);
1585 M_destroy(newE - 1);
1590 M_deallocate(newB, sz);
1593 if (impl_.b_) M_deallocate(impl_.b_, size());
1596 impl_.z_ = newB + sz;
1599 //=============================================================================
1600 //-----------------------------------------------------------------------------
1601 // specialized functions
1603 template <class T, class A>
1604 void swap(fbvector<T, A>& lhs, fbvector<T, A>& rhs) noexcept {
1608 //=============================================================================
1609 //-----------------------------------------------------------------------------
1615 template <class T, class A>
1616 struct IndexableTraits<fbvector<T, A>>
1617 : public IndexableTraitsSeq<fbvector<T, A>> {
1620 } // namespace detail
1622 template <class T, class A>
1623 void compactResize(fbvector<T, A>* v, size_t sz) {
1630 // relinquish and attach are not a members function specifically so that it is
1631 // awkward to call them. It is very easy to shoot yourself in the foot with
1634 // If you call relinquish, then it is your responsibility to free the data
1635 // and the storage, both of which may have been generated in a non-standard
1636 // way through the fbvector's allocator.
1638 // If you call attach, it is your responsibility to ensure that the fbvector
1639 // is fresh (size and capacity both zero), and that the supplied data is
1640 // capable of being manipulated by the allocator.
1641 // It is acceptable to supply a stack pointer IF:
1642 // (1) The vector's data does not outlive the stack pointer. This includes
1643 // extension of the data's life through a move operation.
1644 // (2) The pointer has enough capacity that the vector will never be
1646 // (3) Insert is not called on the vector; these functions have leeway to
1647 // relocate the vector even if there is enough capacity.
1648 // (4) A stack pointer is compatible with the fbvector's allocator.
1651 template <class T, class A>
1652 T* relinquish(fbvector<T, A>& v) {
1654 v.impl_.b_ = v.impl_.e_ = v.impl_.z_ = nullptr;
1658 template <class T, class A>
1659 void attach(fbvector<T, A>& v, T* data, size_t sz, size_t cap) {
1660 assert(v.data() == nullptr);
1662 v.impl_.e_ = data + sz;
1663 v.impl_.z_ = data + cap;
1666 } // namespace folly