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) {
525 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
529 S_uninitialized_copy_bits(T* dest, std::move_iterator<T*> first,
530 std::move_iterator<T*> last) {
531 T* bFirst = first.base();
532 T* bLast = last.base();
533 std::memcpy((void*)dest, (void*)bFirst, (bLast - bFirst) * sizeof(T));
536 template <typename It>
538 S_uninitialized_copy_bits(T* dest, It first, It last) {
539 S_uninitialized_copy(dest, first, last);
542 //---------------------------------------------------------------------------
545 // This function is "unsafe": it assumes that the iterator can be advanced at
546 // least n times. However, as a private function, that unsafety is managed
547 // wholly by fbvector itself.
549 template <typename It>
550 static It S_copy_n(T* dest, It first, size_type n) {
552 for (; dest != e; ++dest, ++first) *dest = *first;
556 static const T* S_copy_n(T* dest, const T* first, size_type n) {
557 if (folly::IsTriviallyCopyable<T>::value) {
558 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
561 return S_copy_n<const T*>(dest, first, n);
565 static std::move_iterator<T*>
566 S_copy_n(T* dest, std::move_iterator<T*> mIt, size_type n) {
567 if (folly::IsTriviallyCopyable<T>::value) {
568 T* first = mIt.base();
569 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
570 return std::make_move_iterator(first + n);
572 return S_copy_n<std::move_iterator<T*>>(dest, mIt, n);
576 //===========================================================================
577 //---------------------------------------------------------------------------
578 // relocation helpers
581 // Relocation is divided into three parts:
584 // Performs the actual movement of data from point a to point b.
587 // Destroys the old data.
590 // Destoys the new data and restores the old data.
592 // The three steps are used because there may be an exception after part 1
593 // has completed. If that is the case, then relocate_undo can nullify the
594 // initial move. Otherwise, relocate_done performs the last bit of tidying
597 // The relocation trio may use either memcpy, move, or copy. It is decided
598 // by the following case statement:
600 // IsRelocatable && usingStdAllocator -> memcpy
601 // has_nothrow_move && usingStdAllocator -> move
602 // cannot copy -> move
605 // If the class is non-copyable then it must be movable. However, if the
606 // move constructor is not noexcept, i.e. an error could be thrown, then
607 // relocate_undo will be unable to restore the old data, for fear of a
608 // second exception being thrown. This is a known and unavoidable
609 // deficiency. In lieu of a strong exception guarantee, relocate_undo does
610 // the next best thing: it provides a weak exception guarantee by
611 // destorying the new data, but leaving the old data in an indeterminate
612 // state. Note that that indeterminate state will be valid, since the
613 // old data has not been destroyed; it has merely been the source of a
614 // move, which is required to leave the source in a valid state.
617 void M_relocate(T* newB) {
618 relocate_move(newB, impl_.b_, impl_.e_);
619 relocate_done(newB, impl_.b_, impl_.e_);
622 // dispatch type trait
623 typedef std::integral_constant<bool,
624 folly::IsRelocatable<T>::value && usingStdAllocator::value
625 > relocate_use_memcpy;
627 typedef std::integral_constant<bool,
628 (std::is_nothrow_move_constructible<T>::value
629 && usingStdAllocator::value)
630 || !std::is_copy_constructible<T>::value
634 void relocate_move(T* dest, T* first, T* last) {
635 relocate_move_or_memcpy(dest, first, last, relocate_use_memcpy());
638 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::true_type) {
639 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
642 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::false_type) {
643 relocate_move_or_copy(dest, first, last, relocate_use_move());
646 void relocate_move_or_copy(T* dest, T* first, T* last, std::true_type) {
647 D_uninitialized_move_a(dest, first, last);
650 void relocate_move_or_copy(T* dest, T* first, T* last, std::false_type) {
651 D_uninitialized_copy_a(dest, first, last);
655 void relocate_done(T* /*dest*/, T* first, T* last) noexcept {
656 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
657 // used memcpy; data has been relocated, do not call destructor
659 D_destroy_range_a(first, last);
664 void relocate_undo(T* dest, T* first, T* last) noexcept {
665 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
666 // used memcpy, old data is still valid, nothing to do
667 } else if (std::is_nothrow_move_constructible<T>::value &&
668 usingStdAllocator::value) {
669 // noexcept move everything back, aka relocate_move
670 relocate_move(first, dest, dest + (last - first));
671 } else if (!std::is_copy_constructible<T>::value) {
673 D_destroy_range_a(dest, dest + (last - first));
675 // used copy, old data is still valid
676 D_destroy_range_a(dest, dest + (last - first));
681 //===========================================================================
682 //---------------------------------------------------------------------------
683 // construct/copy/destroy
686 fbvector() = default;
688 explicit fbvector(const Allocator& a) : impl_(a) {}
690 explicit fbvector(size_type n, const Allocator& a = Allocator())
692 { M_uninitialized_fill_n_e(n); }
694 fbvector(size_type n, VT value, const Allocator& a = Allocator())
696 { M_uninitialized_fill_n_e(n, value); }
698 template <class It, class Category = typename
699 std::iterator_traits<It>::iterator_category>
700 fbvector(It first, It last, const Allocator& a = Allocator())
701 : fbvector(first, last, a, Category()) {}
703 fbvector(const fbvector& other)
704 : impl_(other.size(), A::select_on_container_copy_construction(other.impl_))
705 { M_uninitialized_copy_e(other.begin(), other.end()); }
707 fbvector(fbvector&& other) noexcept : impl_(std::move(other.impl_)) {}
709 fbvector(const fbvector& other, const Allocator& a)
710 : fbvector(other.begin(), other.end(), a) {}
712 /* may throw */ fbvector(fbvector&& other, const Allocator& a) : impl_(a) {
713 if (impl_ == other.impl_) {
714 impl_.swapData(other.impl_);
716 impl_.init(other.size());
717 M_uninitialized_move_e(other.begin(), other.end());
721 fbvector(std::initializer_list<T> il, const Allocator& a = Allocator())
722 : fbvector(il.begin(), il.end(), a) {}
724 ~fbvector() = default; // the cleanup occurs in impl_
726 fbvector& operator=(const fbvector& other) {
727 if (UNLIKELY(this == &other)) return *this;
729 if (!usingStdAllocator::value &&
730 A::propagate_on_container_copy_assignment::value) {
731 if (impl_ != other.impl_) {
732 // can't use other's different allocator to clean up self
735 (Allocator&)impl_ = (Allocator&)other.impl_;
738 assign(other.begin(), other.end());
742 fbvector& operator=(fbvector&& other) {
743 if (UNLIKELY(this == &other)) return *this;
744 moveFrom(std::move(other), moveIsSwap());
748 fbvector& operator=(std::initializer_list<T> il) {
749 assign(il.begin(), il.end());
753 template <class It, class Category = typename
754 std::iterator_traits<It>::iterator_category>
755 void assign(It first, It last) {
756 assign(first, last, Category());
759 void assign(size_type n, VT value) {
760 if (n > capacity()) {
761 // Not enough space. Do not reserve in place, since we will
762 // discard the old values anyways.
763 if (dataIsInternalAndNotVT(value)) {
764 T copy(std::move(value));
766 M_uninitialized_fill_n_e(n, copy);
769 M_uninitialized_fill_n_e(n, value);
771 } else if (n <= size()) {
772 auto newE = impl_.b_ + n;
773 std::fill(impl_.b_, newE, value);
774 M_destroy_range_e(newE);
776 std::fill(impl_.b_, impl_.e_, value);
777 M_uninitialized_fill_n_e(n - size(), value);
781 void assign(std::initializer_list<T> il) {
782 assign(il.begin(), il.end());
785 allocator_type get_allocator() const noexcept {
791 // contract dispatch for iterator types fbvector(It first, It last)
792 template <class ForwardIterator>
793 fbvector(ForwardIterator first, ForwardIterator last,
794 const Allocator& a, std::forward_iterator_tag)
795 : impl_(std::distance(first, last), a)
796 { M_uninitialized_copy_e(first, last); }
798 template <class InputIterator>
799 fbvector(InputIterator first, InputIterator last,
800 const Allocator& a, std::input_iterator_tag)
802 { for (; first != last; ++first) emplace_back(*first); }
804 // contract dispatch for allocator movement in operator=(fbvector&&)
806 moveFrom(fbvector&& other, std::true_type) {
807 swap(impl_, other.impl_);
809 void moveFrom(fbvector&& other, std::false_type) {
810 if (impl_ == other.impl_) {
811 impl_.swapData(other.impl_);
813 impl_.reset(other.size());
814 M_uninitialized_move_e(other.begin(), other.end());
818 // contract dispatch for iterator types in assign(It first, It last)
819 template <class ForwardIterator>
820 void assign(ForwardIterator first, ForwardIterator last,
821 std::forward_iterator_tag) {
822 const size_t newSize = std::distance(first, last);
823 if (newSize > capacity()) {
824 impl_.reset(newSize);
825 M_uninitialized_copy_e(first, last);
826 } else if (newSize <= size()) {
827 auto newEnd = std::copy(first, last, impl_.b_);
828 M_destroy_range_e(newEnd);
830 auto mid = S_copy_n(impl_.b_, first, size());
831 M_uninitialized_copy_e<decltype(last)>(mid, last);
835 template <class InputIterator>
836 void assign(InputIterator first, InputIterator last,
837 std::input_iterator_tag) {
839 for (; first != last && p != impl_.e_; ++first, ++p) {
843 M_destroy_range_e(p);
845 for (; first != last; ++first) emplace_back(*first);
849 // contract dispatch for aliasing under VT optimization
850 bool dataIsInternalAndNotVT(const T& t) {
851 if (should_pass_by_value::value) return false;
852 return dataIsInternal(t);
854 bool dataIsInternal(const T& t) {
855 return UNLIKELY(impl_.b_ <= std::addressof(t) &&
856 std::addressof(t) < impl_.e_);
860 //===========================================================================
861 //---------------------------------------------------------------------------
865 iterator begin() noexcept {
868 const_iterator begin() const noexcept {
871 iterator end() noexcept {
874 const_iterator end() const noexcept {
877 reverse_iterator rbegin() noexcept {
878 return reverse_iterator(end());
880 const_reverse_iterator rbegin() const noexcept {
881 return const_reverse_iterator(end());
883 reverse_iterator rend() noexcept {
884 return reverse_iterator(begin());
886 const_reverse_iterator rend() const noexcept {
887 return const_reverse_iterator(begin());
890 const_iterator cbegin() const noexcept {
893 const_iterator cend() const noexcept {
896 const_reverse_iterator crbegin() const noexcept {
897 return const_reverse_iterator(end());
899 const_reverse_iterator crend() const noexcept {
900 return const_reverse_iterator(begin());
903 //===========================================================================
904 //---------------------------------------------------------------------------
908 size_type size() const noexcept {
909 return impl_.e_ - impl_.b_;
912 size_type max_size() const noexcept {
913 // good luck gettin' there
914 return ~size_type(0);
917 void resize(size_type n) {
919 M_destroy_range_e(impl_.b_ + n);
922 M_uninitialized_fill_n_e(n - size());
926 void resize(size_type n, VT t) {
928 M_destroy_range_e(impl_.b_ + n);
929 } else if (dataIsInternalAndNotVT(t) && n > capacity()) {
932 M_uninitialized_fill_n_e(n - size(), copy);
935 M_uninitialized_fill_n_e(n - size(), t);
939 size_type capacity() const noexcept {
940 return impl_.z_ - impl_.b_;
943 bool empty() const noexcept {
944 return impl_.b_ == impl_.e_;
947 void reserve(size_type n) {
948 if (n <= capacity()) return;
949 if (impl_.b_ && reserve_in_place(n)) return;
951 auto newCap = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
952 auto newB = M_allocate(newCap);
956 M_deallocate(newB, newCap);
960 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
961 impl_.z_ = newB + newCap;
962 impl_.e_ = newB + (impl_.e_ - impl_.b_);
966 void shrink_to_fit() noexcept {
972 auto const newCapacityBytes = folly::goodMallocSize(size() * sizeof(T));
973 auto const newCap = newCapacityBytes / sizeof(T);
974 auto const oldCap = capacity();
976 if (newCap >= oldCap) return;
979 // xallocx() will shrink to precisely newCapacityBytes (which was generated
980 // by goodMallocSize()) if it successfully shrinks in place.
981 if ((usingJEMalloc() && usingStdAllocator::value) &&
982 newCapacityBytes >= folly::jemallocMinInPlaceExpandable &&
983 xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
984 impl_.z_ += newCap - oldCap;
986 T* newB; // intentionally uninitialized
988 newB = M_allocate(newCap);
992 M_deallocate(newB, newCap);
993 return; // swallow the error
999 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
1000 impl_.z_ = newB + newCap;
1001 impl_.e_ = newB + (impl_.e_ - impl_.b_);
1008 bool reserve_in_place(size_type n) {
1009 if (!usingStdAllocator::value || !usingJEMalloc()) return false;
1011 // jemalloc can never grow in place blocks smaller than 4096 bytes.
1012 if ((impl_.z_ - impl_.b_) * sizeof(T) <
1013 folly::jemallocMinInPlaceExpandable) return false;
1015 auto const newCapacityBytes = folly::goodMallocSize(n * sizeof(T));
1017 if (xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
1018 impl_.z_ = impl_.b_ + newCapacityBytes / sizeof(T);
1024 //===========================================================================
1025 //---------------------------------------------------------------------------
1029 reference operator[](size_type n) {
1033 const_reference operator[](size_type n) const {
1037 const_reference at(size_type n) const {
1038 if (UNLIKELY(n >= size())) {
1039 throw std::out_of_range("fbvector: index is greater than size.");
1043 reference at(size_type n) {
1044 auto const& cThis = *this;
1045 return const_cast<reference>(cThis.at(n));
1051 const_reference front() const {
1057 return impl_.e_[-1];
1059 const_reference back() const {
1061 return impl_.e_[-1];
1064 //===========================================================================
1065 //---------------------------------------------------------------------------
1069 T* data() noexcept {
1072 const T* data() const noexcept {
1076 //===========================================================================
1077 //---------------------------------------------------------------------------
1078 // modifiers (common)
1081 template <class... Args>
1082 void emplace_back(Args&&... args) {
1083 if (impl_.e_ != impl_.z_) {
1084 M_construct(impl_.e_, std::forward<Args>(args)...);
1087 emplace_back_aux(std::forward<Args>(args)...);
1092 push_back(const T& value) {
1093 if (impl_.e_ != impl_.z_) {
1094 M_construct(impl_.e_, value);
1097 emplace_back_aux(value);
1102 push_back(T&& value) {
1103 if (impl_.e_ != impl_.z_) {
1104 M_construct(impl_.e_, std::move(value));
1107 emplace_back_aux(std::move(value));
1114 M_destroy(impl_.e_);
1117 void swap(fbvector& other) noexcept {
1118 if (!usingStdAllocator::value &&
1119 A::propagate_on_container_swap::value)
1120 swap(impl_, other.impl_);
1121 else impl_.swapData(other.impl_);
1124 void clear() noexcept {
1125 M_destroy_range_e(impl_.b_);
1130 // std::vector implements a similar function with a different growth
1131 // strategy: empty() ? 1 : capacity() * 2.
1133 // fbvector grows differently on two counts:
1136 // Instead of grwoing to size 1 from empty, and fbvector allocates at
1137 // least 64 bytes. You may still use reserve to reserve a lesser amount
1140 // For medium-sized vectors, the growth strategy is 1.5x. See the docs
1142 // This does not apply to very small or very large fbvectors. This is a
1144 // A nice addition to fbvector would be the capability of having a user-
1145 // defined growth strategy, probably as part of the allocator.
1148 size_type computePushBackCapacity() const {
1149 if (capacity() == 0) {
1150 return std::max(64 / sizeof(T), size_type(1));
1152 if (capacity() < folly::jemallocMinInPlaceExpandable / sizeof(T)) {
1153 return capacity() * 2;
1155 if (capacity() > 4096 * 32 / sizeof(T)) {
1156 return capacity() * 2;
1158 return (capacity() * 3 + 1) / 2;
1161 template <class... Args>
1162 void emplace_back_aux(Args&&... args);
1164 //===========================================================================
1165 //---------------------------------------------------------------------------
1166 // modifiers (erase)
1169 iterator erase(const_iterator position) {
1170 return erase(position, position + 1);
1173 iterator erase(const_iterator first, const_iterator last) {
1174 assert(isValid(first) && isValid(last));
1175 assert(first <= last);
1176 if (first != last) {
1177 if (last == end()) {
1178 M_destroy_range_e((iterator)first);
1180 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1181 D_destroy_range_a((iterator)first, (iterator)last);
1182 if (last - first >= cend() - last) {
1183 std::memcpy((void*)first, (void*)last, (cend() - last) * sizeof(T));
1185 std::memmove((iterator)first, last, (cend() - last) * sizeof(T));
1187 impl_.e_ -= (last - first);
1189 std::copy(std::make_move_iterator((iterator)last),
1190 std::make_move_iterator(end()), (iterator)first);
1191 auto newEnd = impl_.e_ - std::distance(first, last);
1192 M_destroy_range_e(newEnd);
1196 return (iterator)first;
1199 //===========================================================================
1200 //---------------------------------------------------------------------------
1201 // modifiers (insert)
1202 private: // we have the private section first because it defines some macros
1204 bool isValid(const_iterator it) {
1205 return cbegin() <= it && it <= cend();
1208 size_type computeInsertCapacity(size_type n) {
1209 size_type nc = std::max(computePushBackCapacity(), size() + n);
1210 size_type ac = folly::goodMallocSize(nc * sizeof(T)) / sizeof(T);
1214 //---------------------------------------------------------------------------
1216 // make_window takes an fbvector, and creates an uninitialized gap (a
1217 // window) at the given position, of the given size. The fbvector must
1218 // have enough capacity.
1220 // Explanation by picture.
1224 // make_window here of size 3
1228 // If something goes wrong and the window must be destroyed, use
1229 // undo_window to provide a weak exception guarantee. It destroys
1234 //---------------------------------------------------------------------------
1236 // wrap_frame takes an inverse window and relocates an fbvector around it.
1237 // The fbvector must have at least as many elements as the left ledge.
1239 // Explanation by picture.
1242 // fbvector: inverse window:
1243 // 123456789______ _____abcde_______
1247 // _______________ 12345abcde6789___
1249 //---------------------------------------------------------------------------
1251 // insert_use_fresh_memory returns true iff the fbvector should use a fresh
1252 // block of memory for the insertion. If the fbvector does not have enough
1253 // spare capacity, then it must return true. Otherwise either true or false
1256 //---------------------------------------------------------------------------
1258 // These three functions, make_window, wrap_frame, and
1259 // insert_use_fresh_memory, can be combined into a uniform interface.
1260 // Since that interface involves a lot of case-work, it is built into
1261 // some macros: FOLLY_FBVECTOR_INSERT_(PRE|START|TRY|END)
1262 // Macros are used in an attempt to let GCC perform better optimizations,
1263 // especially control flow optimization.
1266 //---------------------------------------------------------------------------
1269 void make_window(iterator position, size_type n) {
1270 // The result is guaranteed to be non-negative, so use an unsigned type:
1271 size_type tail = std::distance(position, impl_.e_);
1274 relocate_move(position + n, position, impl_.e_);
1275 relocate_done(position + n, position, impl_.e_);
1278 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1279 std::memmove(position + n, position, tail * sizeof(T));
1282 D_uninitialized_move_a(impl_.e_, impl_.e_ - n, impl_.e_);
1284 std::copy_backward(std::make_move_iterator(position),
1285 std::make_move_iterator(impl_.e_ - n), impl_.e_);
1287 D_destroy_range_a(impl_.e_ - n, impl_.e_ + n);
1292 D_destroy_range_a(position, position + n);
1297 void undo_window(iterator position, size_type n) noexcept {
1298 D_destroy_range_a(position + n, impl_.e_);
1299 impl_.e_ = position;
1302 //---------------------------------------------------------------------------
1305 void wrap_frame(T* ledge, size_type idx, size_type n) {
1306 assert(size() >= idx);
1309 relocate_move(ledge, impl_.b_, impl_.b_ + idx);
1311 relocate_move(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1313 relocate_undo(ledge, impl_.b_, impl_.b_ + idx);
1316 relocate_done(ledge, impl_.b_, impl_.b_ + idx);
1317 relocate_done(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1320 //---------------------------------------------------------------------------
1323 bool insert_use_fresh(bool at_end, size_type n) {
1325 if (size() + n <= capacity()) return false;
1326 if (reserve_in_place(size() + n)) return false;
1330 if (size() + n > capacity()) return true;
1335 //---------------------------------------------------------------------------
1338 #define FOLLY_FBVECTOR_INSERT_PRE(cpos, n) \
1339 if (n == 0) return (iterator)cpos; \
1340 bool at_end = cpos == cend(); \
1341 bool fresh = insert_use_fresh(at_end, n); \
1345 // check for internal data (technically not required by the standard)
1347 #define FOLLY_FBVECTOR_INSERT_START(cpos, n) \
1349 assert(isValid(cpos)); \
1351 T* position = const_cast<T*>(cpos); \
1352 size_type idx = std::distance(impl_.b_, position); \
1354 size_type newCap; /* intentionally uninitialized */ \
1357 newCap = computeInsertCapacity(n); \
1358 b = M_allocate(newCap); \
1361 make_window(position, n); \
1368 T* start = b + idx; \
1372 // construct the inserted elements
1374 #define FOLLY_FBVECTOR_INSERT_TRY(cpos, n) \
1377 M_deallocate(b, newCap); \
1380 undo_window(position, n); \
1390 wrap_frame(b, idx, n); \
1394 // delete the inserted elements (exception has been thrown)
1396 #define FOLLY_FBVECTOR_INSERT_END(cpos, n) \
1397 M_deallocate(b, newCap); \
1400 if (impl_.b_) M_deallocate(impl_.b_, capacity()); \
1401 impl_.set(b, size() + n, newCap); \
1402 return impl_.b_ + idx; \
1407 //---------------------------------------------------------------------------
1411 template <class... Args>
1412 iterator emplace(const_iterator cpos, Args&&... args) {
1413 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1414 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1415 M_construct(start, std::forward<Args>(args)...);
1416 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1418 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1421 iterator insert(const_iterator cpos, const T& value) {
1422 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1423 if (dataIsInternal(value)) return insert(cpos, T(value));
1424 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1425 M_construct(start, value);
1426 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1428 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1431 iterator insert(const_iterator cpos, T&& value) {
1432 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1433 if (dataIsInternal(value)) return insert(cpos, T(std::move(value)));
1434 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1435 M_construct(start, std::move(value));
1436 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1438 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1441 iterator insert(const_iterator cpos, size_type n, VT value) {
1442 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1443 if (dataIsInternalAndNotVT(value)) return insert(cpos, n, T(value));
1444 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1445 D_uninitialized_fill_n_a(start, n, value);
1446 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1447 D_destroy_range_a(start, start + n);
1448 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1451 template <class It, class Category = typename
1452 std::iterator_traits<It>::iterator_category>
1453 iterator insert(const_iterator cpos, It first, It last) {
1454 return insert(cpos, first, last, Category());
1457 iterator insert(const_iterator cpos, std::initializer_list<T> il) {
1458 return insert(cpos, il.begin(), il.end());
1461 //---------------------------------------------------------------------------
1462 // insert dispatch for iterator types
1465 template <class FIt>
1466 iterator insert(const_iterator cpos, FIt first, FIt last,
1467 std::forward_iterator_tag) {
1468 size_type n = std::distance(first, last);
1469 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1470 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1471 D_uninitialized_copy_a(start, first, last);
1472 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1473 D_destroy_range_a(start, start + n);
1474 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1477 template <class IIt>
1478 iterator insert(const_iterator cpos, IIt first, IIt last,
1479 std::input_iterator_tag) {
1480 T* position = const_cast<T*>(cpos);
1481 assert(isValid(position));
1482 size_type idx = std::distance(begin(), position);
1484 fbvector storage(std::make_move_iterator(position),
1485 std::make_move_iterator(end()),
1486 A::select_on_container_copy_construction(impl_));
1487 M_destroy_range_e(position);
1488 for (; first != last; ++first) emplace_back(*first);
1489 insert(cend(), std::make_move_iterator(storage.begin()),
1490 std::make_move_iterator(storage.end()));
1491 return impl_.b_ + idx;
1494 //===========================================================================
1495 //---------------------------------------------------------------------------
1496 // lexicographical functions (others from boost::totally_ordered superclass)
1499 bool operator==(const fbvector& other) const {
1500 return size() == other.size() && std::equal(begin(), end(), other.begin());
1503 bool operator<(const fbvector& other) const {
1504 return std::lexicographical_compare(
1505 begin(), end(), other.begin(), other.end());
1508 //===========================================================================
1509 //---------------------------------------------------------------------------
1513 template <class _T, class _A>
1514 friend _T* relinquish(fbvector<_T, _A>&);
1516 template <class _T, class _A>
1517 friend void attach(fbvector<_T, _A>&, _T* data, size_t sz, size_t cap);
1519 }; // class fbvector
1522 //=============================================================================
1523 //-----------------------------------------------------------------------------
1524 // outlined functions (gcc, you finicky compiler you)
1526 template <typename T, typename Allocator>
1527 template <class... Args>
1528 void fbvector<T, Allocator>::emplace_back_aux(Args&&... args) {
1529 size_type byte_sz = folly::goodMallocSize(
1530 computePushBackCapacity() * sizeof(T));
1531 if (usingStdAllocator::value
1533 && ((impl_.z_ - impl_.b_) * sizeof(T) >=
1534 folly::jemallocMinInPlaceExpandable)) {
1535 // Try to reserve in place.
1536 // Ask xallocx to allocate in place at least size()+1 and at most sz space.
1537 // xallocx will allocate as much as possible within that range, which
1538 // is the best possible outcome: if sz space is available, take it all,
1539 // otherwise take as much as possible. If nothing is available, then fail.
1540 // In this fashion, we never relocate if there is a possibility of
1541 // expanding in place, and we never reallocate by less than the desired
1542 // amount unless we cannot expand further. Hence we will not reallocate
1543 // sub-optimally twice in a row (modulo the blocking memory being freed).
1544 size_type lower = folly::goodMallocSize(sizeof(T) + size() * sizeof(T));
1545 size_type upper = byte_sz;
1546 size_type extra = upper - lower;
1551 if ((actual = xallocx(p, lower, extra, 0)) >= lower) {
1552 impl_.z_ = impl_.b_ + actual / sizeof(T);
1553 M_construct(impl_.e_, std::forward<Args>(args)...);
1559 // Reallocation failed. Perform a manual relocation.
1560 size_type sz = byte_sz / sizeof(T);
1561 auto newB = M_allocate(sz);
1562 auto newE = newB + size();
1564 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1565 // For linear memory access, relocate before construction.
1566 // By the test condition, relocate is noexcept.
1567 // Note that there is no cleanup to do if M_construct throws - that's
1568 // one of the beauties of relocation.
1569 // Benchmarks for this code have high variance, and seem to be close.
1570 relocate_move(newB, impl_.b_, impl_.e_);
1571 M_construct(newE, std::forward<Args>(args)...);
1574 M_construct(newE, std::forward<Args>(args)...);
1579 M_destroy(newE - 1);
1584 M_deallocate(newB, sz);
1587 if (impl_.b_) M_deallocate(impl_.b_, size());
1590 impl_.z_ = newB + sz;
1593 //=============================================================================
1594 //-----------------------------------------------------------------------------
1595 // specialized functions
1597 template <class T, class A>
1598 void swap(fbvector<T, A>& lhs, fbvector<T, A>& rhs) noexcept {
1602 //=============================================================================
1603 //-----------------------------------------------------------------------------
1609 template <class T, class A>
1610 struct IndexableTraits<fbvector<T, A>>
1611 : public IndexableTraitsSeq<fbvector<T, A>> {
1614 } // namespace detail
1616 template <class T, class A>
1617 void compactResize(fbvector<T, A>* v, size_t sz) {
1624 // relinquish and attach are not a members function specifically so that it is
1625 // awkward to call them. It is very easy to shoot yourself in the foot with
1628 // If you call relinquish, then it is your responsibility to free the data
1629 // and the storage, both of which may have been generated in a non-standard
1630 // way through the fbvector's allocator.
1632 // If you call attach, it is your responsibility to ensure that the fbvector
1633 // is fresh (size and capacity both zero), and that the supplied data is
1634 // capable of being manipulated by the allocator.
1635 // It is acceptable to supply a stack pointer IF:
1636 // (1) The vector's data does not outlive the stack pointer. This includes
1637 // extension of the data's life through a move operation.
1638 // (2) The pointer has enough capacity that the vector will never be
1640 // (3) Insert is not called on the vector; these functions have leeway to
1641 // relocate the vector even if there is enough capacity.
1642 // (4) A stack pointer is compatible with the fbvector's allocator.
1645 template <class T, class A>
1646 T* relinquish(fbvector<T, A>& v) {
1648 v.impl_.b_ = v.impl_.e_ = v.impl_.z_ = nullptr;
1652 template <class T, class A>
1653 void attach(fbvector<T, A>& v, T* data, size_t sz, size_t cap) {
1654 assert(v.data() == nullptr);
1656 v.impl_.e_ = data + sz;
1657 v.impl_.z_ = data + cap;
1660 } // namespace folly