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>
42 #include <folly/portability/BitsFunctexcept.h>
44 #include <boost/operators.hpp>
46 //=============================================================================
47 // forward declaration
50 template <class T, class Allocator = std::allocator<T>>
54 //=============================================================================
57 #define FOLLY_FBV_UNROLL_PTR(first, last, OP) do { \
58 for (; (last) - (first) >= 4; (first) += 4) { \
64 for (; (first) != (last); ++(first)) OP((first)); \
67 //=============================================================================
68 ///////////////////////////////////////////////////////////////////////////////
72 ///////////////////////////////////////////////////////////////////////////////
76 template <class T, class Allocator>
77 class fbvector : private boost::totally_ordered<fbvector<T, Allocator>> {
79 //===========================================================================
80 //---------------------------------------------------------------------------
84 typedef std::allocator_traits<Allocator> A;
86 struct Impl : public Allocator {
88 typedef typename A::pointer pointer;
89 typedef typename A::size_type size_type;
95 Impl() : Allocator(), b_(nullptr), e_(nullptr), z_(nullptr) {}
96 /* implicit */ Impl(const Allocator& a)
97 : Allocator(a), b_(nullptr), e_(nullptr), z_(nullptr) {}
98 /* implicit */ Impl(Allocator&& a)
99 : Allocator(std::move(a)), b_(nullptr), e_(nullptr), z_(nullptr) {}
101 /* implicit */ Impl(size_type n, const Allocator& a = Allocator())
105 Impl(Impl&& other) noexcept
106 : Allocator(std::move(other)),
107 b_(other.b_), e_(other.e_), z_(other.z_)
108 { other.b_ = other.e_ = other.z_ = nullptr; }
116 // note that 'allocate' and 'deallocate' are inherited from Allocator
117 T* D_allocate(size_type n) {
118 if (usingStdAllocator::value) {
119 return static_cast<T*>(malloc(n * sizeof(T)));
121 return std::allocator_traits<Allocator>::allocate(*this, n);
125 void D_deallocate(T* p, size_type n) noexcept {
126 if (usingStdAllocator::value) {
129 std::allocator_traits<Allocator>::deallocate(*this, p, n);
134 void swapData(Impl& other) {
135 std::swap(b_, other.b_);
136 std::swap(e_, other.e_);
137 std::swap(z_, other.z_);
141 inline void destroy() noexcept {
143 // THIS DISPATCH CODE IS DUPLICATED IN fbvector::D_destroy_range_a.
144 // It has been inlined here for speed. It calls the static fbvector
145 // methods to perform the actual destruction.
146 if (usingStdAllocator::value) {
147 S_destroy_range(b_, e_);
149 S_destroy_range_a(*this, b_, e_);
152 D_deallocate(b_, z_ - b_);
156 void init(size_type n) {
157 if (UNLIKELY(n == 0)) {
158 b_ = e_ = z_ = nullptr;
160 size_type sz = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
167 void set(pointer newB, size_type newSize, size_type newCap) {
173 void reset(size_type newCap) {
182 void reset() { // same as reset(0)
184 b_ = e_ = z_ = nullptr;
188 static void swap(Impl& a, Impl& b) {
190 if (!usingStdAllocator::value) swap<Allocator>(a, b);
194 //===========================================================================
195 //---------------------------------------------------------------------------
196 // types and constants
199 typedef T value_type;
200 typedef value_type& reference;
201 typedef const value_type& const_reference;
203 typedef const T* const_iterator;
204 typedef size_t size_type;
205 typedef typename std::make_signed<size_type>::type difference_type;
206 typedef Allocator allocator_type;
207 typedef typename A::pointer pointer;
208 typedef typename A::const_pointer const_pointer;
209 typedef std::reverse_iterator<iterator> reverse_iterator;
210 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
214 typedef std::integral_constant<bool,
215 boost::has_trivial_copy_constructor<T>::value &&
216 sizeof(T) <= 16 // don't force large structures to be passed by value
217 > should_pass_by_value;
218 typedef typename std::conditional<
219 should_pass_by_value::value, T, const T&>::type VT;
220 typedef typename std::conditional<
221 should_pass_by_value::value, T, T&&>::type MT;
223 typedef std::integral_constant<bool,
224 std::is_same<Allocator, std::allocator<T>>::value> usingStdAllocator;
225 typedef std::integral_constant<bool,
226 usingStdAllocator::value ||
227 A::propagate_on_container_move_assignment::value> moveIsSwap;
229 //===========================================================================
230 //---------------------------------------------------------------------------
234 //---------------------------------------------------------------------------
237 T* M_allocate(size_type n) {
238 return impl_.D_allocate(n);
241 //---------------------------------------------------------------------------
244 void M_deallocate(T* p, size_type n) noexcept {
245 impl_.D_deallocate(p, n);
248 //---------------------------------------------------------------------------
251 // GCC is very sensitive to the exact way that construct is called. For
252 // that reason there are several different specializations of construct.
254 template <typename U, typename... Args>
255 void M_construct(U* p, Args&&... args) {
256 if (usingStdAllocator::value) {
257 new (p) U(std::forward<Args>(args)...);
259 std::allocator_traits<Allocator>::construct(
260 impl_, p, std::forward<Args>(args)...);
264 template <typename U, typename... Args>
265 static void S_construct(U* p, Args&&... args) {
266 new (p) U(std::forward<Args>(args)...);
269 template <typename U, typename... Args>
270 static void S_construct_a(Allocator& a, U* p, Args&&... args) {
271 std::allocator_traits<Allocator>::construct(
272 a, p, std::forward<Args>(args)...);
275 // scalar optimization
276 // TODO we can expand this optimization to: default copyable and assignable
277 template <typename U, typename Enable = typename
278 std::enable_if<std::is_scalar<U>::value>::type>
279 void M_construct(U* p, U arg) {
280 if (usingStdAllocator::value) {
283 std::allocator_traits<Allocator>::construct(impl_, p, arg);
287 template <typename U, typename Enable = typename
288 std::enable_if<std::is_scalar<U>::value>::type>
289 static void S_construct(U* p, U arg) {
293 template <typename U, typename Enable = typename
294 std::enable_if<std::is_scalar<U>::value>::type>
295 static void S_construct_a(Allocator& a, U* p, U arg) {
296 std::allocator_traits<Allocator>::construct(a, p, arg);
299 // const& optimization
300 template <typename U, typename Enable = typename
301 std::enable_if<!std::is_scalar<U>::value>::type>
302 void M_construct(U* p, const U& value) {
303 if (usingStdAllocator::value) {
306 std::allocator_traits<Allocator>::construct(impl_, p, value);
310 template <typename U, typename Enable = typename
311 std::enable_if<!std::is_scalar<U>::value>::type>
312 static void S_construct(U* p, const U& value) {
316 template <typename U, typename Enable = typename
317 std::enable_if<!std::is_scalar<U>::value>::type>
318 static void S_construct_a(Allocator& a, U* p, const U& value) {
319 std::allocator_traits<Allocator>::construct(a, p, value);
322 //---------------------------------------------------------------------------
325 void M_destroy(T* p) noexcept {
326 if (usingStdAllocator::value) {
327 if (!boost::has_trivial_destructor<T>::value) p->~T();
329 std::allocator_traits<Allocator>::destroy(impl_, p);
333 //===========================================================================
334 //---------------------------------------------------------------------------
335 // algorithmic helpers
338 //---------------------------------------------------------------------------
342 void M_destroy_range_e(T* pos) noexcept {
343 D_destroy_range_a(pos, impl_.e_);
348 // THIS DISPATCH CODE IS DUPLICATED IN IMPL. SEE IMPL FOR DETAILS.
349 void D_destroy_range_a(T* first, T* last) noexcept {
350 if (usingStdAllocator::value) {
351 S_destroy_range(first, last);
353 S_destroy_range_a(impl_, first, last);
358 static void S_destroy_range_a(Allocator& a, T* first, T* last) noexcept {
359 for (; first != last; ++first)
360 std::allocator_traits<Allocator>::destroy(a, first);
364 static void S_destroy_range(T* first, T* last) noexcept {
365 if (!boost::has_trivial_destructor<T>::value) {
366 // EXPERIMENTAL DATA on fbvector<vector<int>> (where each vector<int> has
368 // The unrolled version seems to work faster for small to medium sized
369 // fbvectors. It gets a 10% speedup on fbvectors of size 1024, 64, and
371 // The simple loop version seems to work faster for large fbvectors. The
372 // unrolled version is about 6% slower on fbvectors on size 16384.
373 // The two methods seem tied for very large fbvectors. The unrolled
374 // version is about 0.5% slower on size 262144.
376 // for (; first != last; ++first) first->~T();
377 #define FOLLY_FBV_OP(p) (p)->~T()
378 FOLLY_FBV_UNROLL_PTR(first, last, FOLLY_FBV_OP)
383 //---------------------------------------------------------------------------
384 // uninitialized_fill_n
387 void M_uninitialized_fill_n_e(size_type sz) {
388 D_uninitialized_fill_n_a(impl_.e_, sz);
392 void M_uninitialized_fill_n_e(size_type sz, VT value) {
393 D_uninitialized_fill_n_a(impl_.e_, sz, value);
398 void D_uninitialized_fill_n_a(T* dest, size_type sz) {
399 if (usingStdAllocator::value) {
400 S_uninitialized_fill_n(dest, sz);
402 S_uninitialized_fill_n_a(impl_, dest, sz);
406 void D_uninitialized_fill_n_a(T* dest, size_type sz, VT value) {
407 if (usingStdAllocator::value) {
408 S_uninitialized_fill_n(dest, sz, value);
410 S_uninitialized_fill_n_a(impl_, dest, sz, value);
415 template <typename... Args>
416 static void S_uninitialized_fill_n_a(Allocator& a, T* dest,
417 size_type sz, Args&&... args) {
422 std::allocator_traits<Allocator>::construct(a, b,
423 std::forward<Args>(args)...);
425 S_destroy_range_a(a, dest, b);
431 static void S_uninitialized_fill_n(T* dest, size_type n) {
432 if (folly::IsZeroInitializable<T>::value) {
433 std::memset(dest, 0, sizeof(T) * n);
438 for (; b != e; ++b) S_construct(b);
441 for (; b >= dest; --b) b->~T();
447 static void S_uninitialized_fill_n(T* dest, size_type n, const T& value) {
451 for (; b != e; ++b) S_construct(b, value);
453 S_destroy_range(dest, b);
458 //---------------------------------------------------------------------------
459 // uninitialized_copy
461 // it is possible to add an optimization for the case where
462 // It = move(T*) and IsRelocatable<T> and Is0Initiailizable<T>
465 template <typename It>
466 void M_uninitialized_copy_e(It first, It last) {
467 D_uninitialized_copy_a(impl_.e_, first, last);
468 impl_.e_ += std::distance(first, last);
471 template <typename It>
472 void M_uninitialized_move_e(It first, It last) {
473 D_uninitialized_move_a(impl_.e_, first, last);
474 impl_.e_ += std::distance(first, last);
478 template <typename It>
479 void D_uninitialized_copy_a(T* dest, It first, It last) {
480 if (usingStdAllocator::value) {
481 if (folly::IsTriviallyCopyable<T>::value) {
482 S_uninitialized_copy_bits(dest, first, last);
484 S_uninitialized_copy(dest, first, last);
487 S_uninitialized_copy_a(impl_, dest, first, last);
491 template <typename It>
492 void D_uninitialized_move_a(T* dest, It first, It last) {
493 D_uninitialized_copy_a(dest,
494 std::make_move_iterator(first), std::make_move_iterator(last));
498 template <typename It>
500 S_uninitialized_copy_a(Allocator& a, T* dest, It first, It last) {
503 for (; first != last; ++first, ++b)
504 std::allocator_traits<Allocator>::construct(a, b, *first);
506 S_destroy_range_a(a, dest, b);
512 template <typename It>
513 static void S_uninitialized_copy(T* dest, It first, It last) {
516 for (; first != last; ++first, ++b)
517 S_construct(b, *first);
519 S_destroy_range(dest, b);
525 S_uninitialized_copy_bits(T* dest, const T* first, const T* last) {
527 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
532 S_uninitialized_copy_bits(T* dest, std::move_iterator<T*> first,
533 std::move_iterator<T*> last) {
534 T* bFirst = first.base();
535 T* bLast = last.base();
536 if (bLast != bFirst) {
537 std::memcpy((void*)dest, (void*)bFirst, (bLast - bFirst) * sizeof(T));
541 template <typename It>
543 S_uninitialized_copy_bits(T* dest, It first, It last) {
544 S_uninitialized_copy(dest, first, last);
547 //---------------------------------------------------------------------------
550 // This function is "unsafe": it assumes that the iterator can be advanced at
551 // least n times. However, as a private function, that unsafety is managed
552 // wholly by fbvector itself.
554 template <typename It>
555 static It S_copy_n(T* dest, It first, size_type n) {
557 for (; dest != e; ++dest, ++first) *dest = *first;
561 static const T* S_copy_n(T* dest, const T* first, size_type n) {
562 if (folly::IsTriviallyCopyable<T>::value) {
563 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
566 return S_copy_n<const T*>(dest, first, n);
570 static std::move_iterator<T*>
571 S_copy_n(T* dest, std::move_iterator<T*> mIt, size_type n) {
572 if (folly::IsTriviallyCopyable<T>::value) {
573 T* first = mIt.base();
574 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
575 return std::make_move_iterator(first + n);
577 return S_copy_n<std::move_iterator<T*>>(dest, mIt, n);
581 //===========================================================================
582 //---------------------------------------------------------------------------
583 // relocation helpers
586 // Relocation is divided into three parts:
589 // Performs the actual movement of data from point a to point b.
592 // Destroys the old data.
595 // Destoys the new data and restores the old data.
597 // The three steps are used because there may be an exception after part 1
598 // has completed. If that is the case, then relocate_undo can nullify the
599 // initial move. Otherwise, relocate_done performs the last bit of tidying
602 // The relocation trio may use either memcpy, move, or copy. It is decided
603 // by the following case statement:
605 // IsRelocatable && usingStdAllocator -> memcpy
606 // has_nothrow_move && usingStdAllocator -> move
607 // cannot copy -> move
610 // If the class is non-copyable then it must be movable. However, if the
611 // move constructor is not noexcept, i.e. an error could be thrown, then
612 // relocate_undo will be unable to restore the old data, for fear of a
613 // second exception being thrown. This is a known and unavoidable
614 // deficiency. In lieu of a strong exception guarantee, relocate_undo does
615 // the next best thing: it provides a weak exception guarantee by
616 // destorying the new data, but leaving the old data in an indeterminate
617 // state. Note that that indeterminate state will be valid, since the
618 // old data has not been destroyed; it has merely been the source of a
619 // move, which is required to leave the source in a valid state.
622 void M_relocate(T* newB) {
623 relocate_move(newB, impl_.b_, impl_.e_);
624 relocate_done(newB, impl_.b_, impl_.e_);
627 // dispatch type trait
628 typedef std::integral_constant<bool,
629 folly::IsRelocatable<T>::value && usingStdAllocator::value
630 > relocate_use_memcpy;
632 typedef std::integral_constant<bool,
633 (std::is_nothrow_move_constructible<T>::value
634 && usingStdAllocator::value)
635 || !std::is_copy_constructible<T>::value
639 void relocate_move(T* dest, T* first, T* last) {
640 relocate_move_or_memcpy(dest, first, last, relocate_use_memcpy());
643 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::true_type) {
644 if (first != nullptr) {
645 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
649 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::false_type) {
650 relocate_move_or_copy(dest, first, last, relocate_use_move());
653 void relocate_move_or_copy(T* dest, T* first, T* last, std::true_type) {
654 D_uninitialized_move_a(dest, first, last);
657 void relocate_move_or_copy(T* dest, T* first, T* last, std::false_type) {
658 D_uninitialized_copy_a(dest, first, last);
662 void relocate_done(T* /*dest*/, T* first, T* last) noexcept {
663 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
664 // used memcpy; data has been relocated, do not call destructor
666 D_destroy_range_a(first, last);
671 void relocate_undo(T* dest, T* first, T* last) noexcept {
672 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
673 // used memcpy, old data is still valid, nothing to do
674 } else if (std::is_nothrow_move_constructible<T>::value &&
675 usingStdAllocator::value) {
676 // noexcept move everything back, aka relocate_move
677 relocate_move(first, dest, dest + (last - first));
678 } else if (!std::is_copy_constructible<T>::value) {
680 D_destroy_range_a(dest, dest + (last - first));
682 // used copy, old data is still valid
683 D_destroy_range_a(dest, dest + (last - first));
688 //===========================================================================
689 //---------------------------------------------------------------------------
690 // construct/copy/destroy
693 fbvector() = default;
695 explicit fbvector(const Allocator& a) : impl_(a) {}
697 explicit fbvector(size_type n, const Allocator& a = Allocator())
699 { M_uninitialized_fill_n_e(n); }
701 fbvector(size_type n, VT value, const Allocator& a = Allocator())
703 { M_uninitialized_fill_n_e(n, value); }
705 template <class It, class Category = typename
706 std::iterator_traits<It>::iterator_category>
707 fbvector(It first, It last, const Allocator& a = Allocator())
708 : fbvector(first, last, a, Category()) {}
710 fbvector(const fbvector& other)
711 : impl_(other.size(), A::select_on_container_copy_construction(other.impl_))
712 { M_uninitialized_copy_e(other.begin(), other.end()); }
714 fbvector(fbvector&& other) noexcept : impl_(std::move(other.impl_)) {}
716 fbvector(const fbvector& other, const Allocator& a)
717 : fbvector(other.begin(), other.end(), a) {}
719 /* may throw */ fbvector(fbvector&& other, const Allocator& a) : impl_(a) {
720 if (impl_ == other.impl_) {
721 impl_.swapData(other.impl_);
723 impl_.init(other.size());
724 M_uninitialized_move_e(other.begin(), other.end());
728 fbvector(std::initializer_list<T> il, const Allocator& a = Allocator())
729 : fbvector(il.begin(), il.end(), a) {}
731 ~fbvector() = default; // the cleanup occurs in impl_
733 fbvector& operator=(const fbvector& other) {
734 if (UNLIKELY(this == &other)) return *this;
736 if (!usingStdAllocator::value &&
737 A::propagate_on_container_copy_assignment::value) {
738 if (impl_ != other.impl_) {
739 // can't use other's different allocator to clean up self
742 (Allocator&)impl_ = (Allocator&)other.impl_;
745 assign(other.begin(), other.end());
749 fbvector& operator=(fbvector&& other) {
750 if (UNLIKELY(this == &other)) return *this;
751 moveFrom(std::move(other), moveIsSwap());
755 fbvector& operator=(std::initializer_list<T> il) {
756 assign(il.begin(), il.end());
760 template <class It, class Category = typename
761 std::iterator_traits<It>::iterator_category>
762 void assign(It first, It last) {
763 assign(first, last, Category());
766 void assign(size_type n, VT value) {
767 if (n > capacity()) {
768 // Not enough space. Do not reserve in place, since we will
769 // discard the old values anyways.
770 if (dataIsInternalAndNotVT(value)) {
771 T copy(std::move(value));
773 M_uninitialized_fill_n_e(n, copy);
776 M_uninitialized_fill_n_e(n, value);
778 } else if (n <= size()) {
779 auto newE = impl_.b_ + n;
780 std::fill(impl_.b_, newE, value);
781 M_destroy_range_e(newE);
783 std::fill(impl_.b_, impl_.e_, value);
784 M_uninitialized_fill_n_e(n - size(), value);
788 void assign(std::initializer_list<T> il) {
789 assign(il.begin(), il.end());
792 allocator_type get_allocator() const noexcept {
798 // contract dispatch for iterator types fbvector(It first, It last)
799 template <class ForwardIterator>
800 fbvector(ForwardIterator first, ForwardIterator last,
801 const Allocator& a, std::forward_iterator_tag)
802 : impl_(std::distance(first, last), a)
803 { M_uninitialized_copy_e(first, last); }
805 template <class InputIterator>
806 fbvector(InputIterator first, InputIterator last,
807 const Allocator& a, std::input_iterator_tag)
809 { for (; first != last; ++first) emplace_back(*first); }
811 // contract dispatch for allocator movement in operator=(fbvector&&)
813 moveFrom(fbvector&& other, std::true_type) {
814 swap(impl_, other.impl_);
816 void moveFrom(fbvector&& other, std::false_type) {
817 if (impl_ == other.impl_) {
818 impl_.swapData(other.impl_);
820 impl_.reset(other.size());
821 M_uninitialized_move_e(other.begin(), other.end());
825 // contract dispatch for iterator types in assign(It first, It last)
826 template <class ForwardIterator>
827 void assign(ForwardIterator first, ForwardIterator last,
828 std::forward_iterator_tag) {
829 const size_t newSize = std::distance(first, last);
830 if (newSize > capacity()) {
831 impl_.reset(newSize);
832 M_uninitialized_copy_e(first, last);
833 } else if (newSize <= size()) {
834 auto newEnd = std::copy(first, last, impl_.b_);
835 M_destroy_range_e(newEnd);
837 auto mid = S_copy_n(impl_.b_, first, size());
838 M_uninitialized_copy_e<decltype(last)>(mid, last);
842 template <class InputIterator>
843 void assign(InputIterator first, InputIterator last,
844 std::input_iterator_tag) {
846 for (; first != last && p != impl_.e_; ++first, ++p) {
850 M_destroy_range_e(p);
852 for (; first != last; ++first) emplace_back(*first);
856 // contract dispatch for aliasing under VT optimization
857 bool dataIsInternalAndNotVT(const T& t) {
858 if (should_pass_by_value::value) return false;
859 return dataIsInternal(t);
861 bool dataIsInternal(const T& t) {
862 return UNLIKELY(impl_.b_ <= std::addressof(t) &&
863 std::addressof(t) < impl_.e_);
867 //===========================================================================
868 //---------------------------------------------------------------------------
872 iterator begin() noexcept {
875 const_iterator begin() const noexcept {
878 iterator end() noexcept {
881 const_iterator end() const noexcept {
884 reverse_iterator rbegin() noexcept {
885 return reverse_iterator(end());
887 const_reverse_iterator rbegin() const noexcept {
888 return const_reverse_iterator(end());
890 reverse_iterator rend() noexcept {
891 return reverse_iterator(begin());
893 const_reverse_iterator rend() const noexcept {
894 return const_reverse_iterator(begin());
897 const_iterator cbegin() const noexcept {
900 const_iterator cend() const noexcept {
903 const_reverse_iterator crbegin() const noexcept {
904 return const_reverse_iterator(end());
906 const_reverse_iterator crend() const noexcept {
907 return const_reverse_iterator(begin());
910 //===========================================================================
911 //---------------------------------------------------------------------------
915 size_type size() const noexcept {
916 return impl_.e_ - impl_.b_;
919 size_type max_size() const noexcept {
920 // good luck gettin' there
921 return ~size_type(0);
924 void resize(size_type n) {
926 M_destroy_range_e(impl_.b_ + n);
929 M_uninitialized_fill_n_e(n - size());
933 void resize(size_type n, VT t) {
935 M_destroy_range_e(impl_.b_ + n);
936 } else if (dataIsInternalAndNotVT(t) && n > capacity()) {
939 M_uninitialized_fill_n_e(n - size(), copy);
942 M_uninitialized_fill_n_e(n - size(), t);
946 size_type capacity() const noexcept {
947 return impl_.z_ - impl_.b_;
950 bool empty() const noexcept {
951 return impl_.b_ == impl_.e_;
954 void reserve(size_type n) {
955 if (n <= capacity()) return;
956 if (impl_.b_ && reserve_in_place(n)) return;
958 auto newCap = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
959 auto newB = M_allocate(newCap);
963 M_deallocate(newB, newCap);
967 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
968 impl_.z_ = newB + newCap;
969 impl_.e_ = newB + (impl_.e_ - impl_.b_);
973 void shrink_to_fit() noexcept {
979 auto const newCapacityBytes = folly::goodMallocSize(size() * sizeof(T));
980 auto const newCap = newCapacityBytes / sizeof(T);
981 auto const oldCap = capacity();
983 if (newCap >= oldCap) return;
986 // xallocx() will shrink to precisely newCapacityBytes (which was generated
987 // by goodMallocSize()) if it successfully shrinks in place.
988 if ((usingJEMalloc() && usingStdAllocator::value) &&
989 newCapacityBytes >= folly::jemallocMinInPlaceExpandable &&
990 xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
991 impl_.z_ += newCap - oldCap;
993 T* newB; // intentionally uninitialized
995 newB = M_allocate(newCap);
999 M_deallocate(newB, newCap);
1000 return; // swallow the error
1006 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
1007 impl_.z_ = newB + newCap;
1008 impl_.e_ = newB + (impl_.e_ - impl_.b_);
1015 bool reserve_in_place(size_type n) {
1016 if (!usingStdAllocator::value || !usingJEMalloc()) return false;
1018 // jemalloc can never grow in place blocks smaller than 4096 bytes.
1019 if ((impl_.z_ - impl_.b_) * sizeof(T) <
1020 folly::jemallocMinInPlaceExpandable) return false;
1022 auto const newCapacityBytes = folly::goodMallocSize(n * sizeof(T));
1024 if (xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
1025 impl_.z_ = impl_.b_ + newCapacityBytes / sizeof(T);
1031 //===========================================================================
1032 //---------------------------------------------------------------------------
1036 reference operator[](size_type n) {
1040 const_reference operator[](size_type n) const {
1044 const_reference at(size_type n) const {
1045 if (UNLIKELY(n >= size())) {
1046 std::__throw_out_of_range("fbvector: index is greater than size.");
1050 reference at(size_type n) {
1051 auto const& cThis = *this;
1052 return const_cast<reference>(cThis.at(n));
1058 const_reference front() const {
1064 return impl_.e_[-1];
1066 const_reference back() const {
1068 return impl_.e_[-1];
1071 //===========================================================================
1072 //---------------------------------------------------------------------------
1076 T* data() noexcept {
1079 const T* data() const noexcept {
1083 //===========================================================================
1084 //---------------------------------------------------------------------------
1085 // modifiers (common)
1088 template <class... Args>
1089 void emplace_back(Args&&... args) {
1090 if (impl_.e_ != impl_.z_) {
1091 M_construct(impl_.e_, std::forward<Args>(args)...);
1094 emplace_back_aux(std::forward<Args>(args)...);
1099 push_back(const T& value) {
1100 if (impl_.e_ != impl_.z_) {
1101 M_construct(impl_.e_, value);
1104 emplace_back_aux(value);
1109 push_back(T&& value) {
1110 if (impl_.e_ != impl_.z_) {
1111 M_construct(impl_.e_, std::move(value));
1114 emplace_back_aux(std::move(value));
1121 M_destroy(impl_.e_);
1124 void swap(fbvector& other) noexcept {
1125 if (!usingStdAllocator::value &&
1126 A::propagate_on_container_swap::value)
1127 swap(impl_, other.impl_);
1128 else impl_.swapData(other.impl_);
1131 void clear() noexcept {
1132 M_destroy_range_e(impl_.b_);
1137 // std::vector implements a similar function with a different growth
1138 // strategy: empty() ? 1 : capacity() * 2.
1140 // fbvector grows differently on two counts:
1143 // Instead of growing to size 1 from empty, fbvector allocates at least
1144 // 64 bytes. You may still use reserve to reserve a lesser amount of
1147 // For medium-sized vectors, the growth strategy is 1.5x. See the docs
1149 // This does not apply to very small or very large fbvectors. This is a
1151 // A nice addition to fbvector would be the capability of having a user-
1152 // defined growth strategy, probably as part of the allocator.
1155 size_type computePushBackCapacity() const {
1156 if (capacity() == 0) {
1157 return std::max(64 / sizeof(T), size_type(1));
1159 if (capacity() < folly::jemallocMinInPlaceExpandable / sizeof(T)) {
1160 return capacity() * 2;
1162 if (capacity() > 4096 * 32 / sizeof(T)) {
1163 return capacity() * 2;
1165 return (capacity() * 3 + 1) / 2;
1168 template <class... Args>
1169 void emplace_back_aux(Args&&... args);
1171 //===========================================================================
1172 //---------------------------------------------------------------------------
1173 // modifiers (erase)
1176 iterator erase(const_iterator position) {
1177 return erase(position, position + 1);
1180 iterator erase(const_iterator first, const_iterator last) {
1181 assert(isValid(first) && isValid(last));
1182 assert(first <= last);
1183 if (first != last) {
1184 if (last == end()) {
1185 M_destroy_range_e((iterator)first);
1187 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1188 D_destroy_range_a((iterator)first, (iterator)last);
1189 if (last - first >= cend() - last) {
1190 std::memcpy((void*)first, (void*)last, (cend() - last) * sizeof(T));
1192 std::memmove((iterator)first, last, (cend() - last) * sizeof(T));
1194 impl_.e_ -= (last - first);
1196 std::copy(std::make_move_iterator((iterator)last),
1197 std::make_move_iterator(end()), (iterator)first);
1198 auto newEnd = impl_.e_ - std::distance(first, last);
1199 M_destroy_range_e(newEnd);
1203 return (iterator)first;
1206 //===========================================================================
1207 //---------------------------------------------------------------------------
1208 // modifiers (insert)
1209 private: // we have the private section first because it defines some macros
1211 bool isValid(const_iterator it) {
1212 return cbegin() <= it && it <= cend();
1215 size_type computeInsertCapacity(size_type n) {
1216 size_type nc = std::max(computePushBackCapacity(), size() + n);
1217 size_type ac = folly::goodMallocSize(nc * sizeof(T)) / sizeof(T);
1221 //---------------------------------------------------------------------------
1223 // make_window takes an fbvector, and creates an uninitialized gap (a
1224 // window) at the given position, of the given size. The fbvector must
1225 // have enough capacity.
1227 // Explanation by picture.
1231 // make_window here of size 3
1235 // If something goes wrong and the window must be destroyed, use
1236 // undo_window to provide a weak exception guarantee. It destroys
1241 //---------------------------------------------------------------------------
1243 // wrap_frame takes an inverse window and relocates an fbvector around it.
1244 // The fbvector must have at least as many elements as the left ledge.
1246 // Explanation by picture.
1249 // fbvector: inverse window:
1250 // 123456789______ _____abcde_______
1254 // _______________ 12345abcde6789___
1256 //---------------------------------------------------------------------------
1258 // insert_use_fresh_memory returns true iff the fbvector should use a fresh
1259 // block of memory for the insertion. If the fbvector does not have enough
1260 // spare capacity, then it must return true. Otherwise either true or false
1263 //---------------------------------------------------------------------------
1265 // These three functions, make_window, wrap_frame, and
1266 // insert_use_fresh_memory, can be combined into a uniform interface.
1267 // Since that interface involves a lot of case-work, it is built into
1268 // some macros: FOLLY_FBVECTOR_INSERT_(PRE|START|TRY|END)
1269 // Macros are used in an attempt to let GCC perform better optimizations,
1270 // especially control flow optimization.
1273 //---------------------------------------------------------------------------
1276 void make_window(iterator position, size_type n) {
1277 // The result is guaranteed to be non-negative, so use an unsigned type:
1278 size_type tail = std::distance(position, impl_.e_);
1281 relocate_move(position + n, position, impl_.e_);
1282 relocate_done(position + n, position, impl_.e_);
1285 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1286 std::memmove(position + n, position, tail * sizeof(T));
1289 D_uninitialized_move_a(impl_.e_, impl_.e_ - n, impl_.e_);
1291 std::copy_backward(std::make_move_iterator(position),
1292 std::make_move_iterator(impl_.e_ - n), impl_.e_);
1294 D_destroy_range_a(impl_.e_ - n, impl_.e_ + n);
1299 D_destroy_range_a(position, position + n);
1304 void undo_window(iterator position, size_type n) noexcept {
1305 D_destroy_range_a(position + n, impl_.e_);
1306 impl_.e_ = position;
1309 //---------------------------------------------------------------------------
1312 void wrap_frame(T* ledge, size_type idx, size_type n) {
1313 assert(size() >= idx);
1316 relocate_move(ledge, impl_.b_, impl_.b_ + idx);
1318 relocate_move(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1320 relocate_undo(ledge, impl_.b_, impl_.b_ + idx);
1323 relocate_done(ledge, impl_.b_, impl_.b_ + idx);
1324 relocate_done(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1327 //---------------------------------------------------------------------------
1330 bool insert_use_fresh(bool at_end, size_type n) {
1332 if (size() + n <= capacity()) return false;
1333 if (reserve_in_place(size() + n)) return false;
1337 if (size() + n > capacity()) return true;
1342 //---------------------------------------------------------------------------
1345 #define FOLLY_FBVECTOR_INSERT_PRE(cpos, n) \
1346 if (n == 0) return (iterator)cpos; \
1347 bool at_end = cpos == cend(); \
1348 bool fresh = insert_use_fresh(at_end, n); \
1352 // check for internal data (technically not required by the standard)
1354 #define FOLLY_FBVECTOR_INSERT_START(cpos, n) \
1356 assert(isValid(cpos)); \
1358 T* position = const_cast<T*>(cpos); \
1359 size_type idx = std::distance(impl_.b_, position); \
1361 size_type newCap; /* intentionally uninitialized */ \
1364 newCap = computeInsertCapacity(n); \
1365 b = M_allocate(newCap); \
1368 make_window(position, n); \
1375 T* start = b + idx; \
1379 // construct the inserted elements
1381 #define FOLLY_FBVECTOR_INSERT_TRY(cpos, n) \
1384 M_deallocate(b, newCap); \
1387 undo_window(position, n); \
1397 wrap_frame(b, idx, n); \
1401 // delete the inserted elements (exception has been thrown)
1403 #define FOLLY_FBVECTOR_INSERT_END(cpos, n) \
1404 M_deallocate(b, newCap); \
1407 if (impl_.b_) M_deallocate(impl_.b_, capacity()); \
1408 impl_.set(b, size() + n, newCap); \
1409 return impl_.b_ + idx; \
1414 //---------------------------------------------------------------------------
1418 template <class... Args>
1419 iterator emplace(const_iterator cpos, Args&&... args) {
1420 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1421 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1422 M_construct(start, std::forward<Args>(args)...);
1423 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1425 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1428 iterator insert(const_iterator cpos, const T& value) {
1429 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1430 if (dataIsInternal(value)) return insert(cpos, T(value));
1431 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1432 M_construct(start, value);
1433 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1435 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1438 iterator insert(const_iterator cpos, T&& value) {
1439 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1440 if (dataIsInternal(value)) return insert(cpos, T(std::move(value)));
1441 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1442 M_construct(start, std::move(value));
1443 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1445 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1448 iterator insert(const_iterator cpos, size_type n, VT value) {
1449 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1450 if (dataIsInternalAndNotVT(value)) return insert(cpos, n, T(value));
1451 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1452 D_uninitialized_fill_n_a(start, n, value);
1453 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1454 D_destroy_range_a(start, start + n);
1455 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1458 template <class It, class Category = typename
1459 std::iterator_traits<It>::iterator_category>
1460 iterator insert(const_iterator cpos, It first, It last) {
1461 return insert(cpos, first, last, Category());
1464 iterator insert(const_iterator cpos, std::initializer_list<T> il) {
1465 return insert(cpos, il.begin(), il.end());
1468 //---------------------------------------------------------------------------
1469 // insert dispatch for iterator types
1472 template <class FIt>
1473 iterator insert(const_iterator cpos, FIt first, FIt last,
1474 std::forward_iterator_tag) {
1475 size_type n = std::distance(first, last);
1476 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1477 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1478 D_uninitialized_copy_a(start, first, last);
1479 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1480 D_destroy_range_a(start, start + n);
1481 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1484 template <class IIt>
1485 iterator insert(const_iterator cpos, IIt first, IIt last,
1486 std::input_iterator_tag) {
1487 T* position = const_cast<T*>(cpos);
1488 assert(isValid(position));
1489 size_type idx = std::distance(begin(), position);
1491 fbvector storage(std::make_move_iterator(position),
1492 std::make_move_iterator(end()),
1493 A::select_on_container_copy_construction(impl_));
1494 M_destroy_range_e(position);
1495 for (; first != last; ++first) emplace_back(*first);
1496 insert(cend(), std::make_move_iterator(storage.begin()),
1497 std::make_move_iterator(storage.end()));
1498 return impl_.b_ + idx;
1501 //===========================================================================
1502 //---------------------------------------------------------------------------
1503 // lexicographical functions (others from boost::totally_ordered superclass)
1506 bool operator==(const fbvector& other) const {
1507 return size() == other.size() && std::equal(begin(), end(), other.begin());
1510 bool operator<(const fbvector& other) const {
1511 return std::lexicographical_compare(
1512 begin(), end(), other.begin(), other.end());
1515 //===========================================================================
1516 //---------------------------------------------------------------------------
1520 template <class _T, class _A>
1521 friend _T* relinquish(fbvector<_T, _A>&);
1523 template <class _T, class _A>
1524 friend void attach(fbvector<_T, _A>&, _T* data, size_t sz, size_t cap);
1526 }; // class fbvector
1529 //=============================================================================
1530 //-----------------------------------------------------------------------------
1531 // outlined functions (gcc, you finicky compiler you)
1533 template <typename T, typename Allocator>
1534 template <class... Args>
1535 void fbvector<T, Allocator>::emplace_back_aux(Args&&... args) {
1536 size_type byte_sz = folly::goodMallocSize(
1537 computePushBackCapacity() * sizeof(T));
1538 if (usingStdAllocator::value
1540 && ((impl_.z_ - impl_.b_) * sizeof(T) >=
1541 folly::jemallocMinInPlaceExpandable)) {
1542 // Try to reserve in place.
1543 // Ask xallocx to allocate in place at least size()+1 and at most sz space.
1544 // xallocx will allocate as much as possible within that range, which
1545 // is the best possible outcome: if sz space is available, take it all,
1546 // otherwise take as much as possible. If nothing is available, then fail.
1547 // In this fashion, we never relocate if there is a possibility of
1548 // expanding in place, and we never reallocate by less than the desired
1549 // amount unless we cannot expand further. Hence we will not reallocate
1550 // sub-optimally twice in a row (modulo the blocking memory being freed).
1551 size_type lower = folly::goodMallocSize(sizeof(T) + size() * sizeof(T));
1552 size_type upper = byte_sz;
1553 size_type extra = upper - lower;
1558 if ((actual = xallocx(p, lower, extra, 0)) >= lower) {
1559 impl_.z_ = impl_.b_ + actual / sizeof(T);
1560 M_construct(impl_.e_, std::forward<Args>(args)...);
1566 // Reallocation failed. Perform a manual relocation.
1567 size_type sz = byte_sz / sizeof(T);
1568 auto newB = M_allocate(sz);
1569 auto newE = newB + size();
1571 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1572 // For linear memory access, relocate before construction.
1573 // By the test condition, relocate is noexcept.
1574 // Note that there is no cleanup to do if M_construct throws - that's
1575 // one of the beauties of relocation.
1576 // Benchmarks for this code have high variance, and seem to be close.
1577 relocate_move(newB, impl_.b_, impl_.e_);
1578 M_construct(newE, std::forward<Args>(args)...);
1581 M_construct(newE, std::forward<Args>(args)...);
1586 M_destroy(newE - 1);
1591 M_deallocate(newB, sz);
1594 if (impl_.b_) M_deallocate(impl_.b_, size());
1597 impl_.z_ = newB + sz;
1600 //=============================================================================
1601 //-----------------------------------------------------------------------------
1602 // specialized functions
1604 template <class T, class A>
1605 void swap(fbvector<T, A>& lhs, fbvector<T, A>& rhs) noexcept {
1609 //=============================================================================
1610 //-----------------------------------------------------------------------------
1616 template <class T, class A>
1617 struct IndexableTraits<fbvector<T, A>>
1618 : public IndexableTraitsSeq<fbvector<T, A>> {
1621 } // namespace detail
1623 template <class T, class A>
1624 void compactResize(fbvector<T, A>* v, size_t sz) {
1631 // relinquish and attach are not a members function specifically so that it is
1632 // awkward to call them. It is very easy to shoot yourself in the foot with
1635 // If you call relinquish, then it is your responsibility to free the data
1636 // and the storage, both of which may have been generated in a non-standard
1637 // way through the fbvector's allocator.
1639 // If you call attach, it is your responsibility to ensure that the fbvector
1640 // is fresh (size and capacity both zero), and that the supplied data is
1641 // capable of being manipulated by the allocator.
1642 // It is acceptable to supply a stack pointer IF:
1643 // (1) The vector's data does not outlive the stack pointer. This includes
1644 // extension of the data's life through a move operation.
1645 // (2) The pointer has enough capacity that the vector will never be
1647 // (3) Insert is not called on the vector; these functions have leeway to
1648 // relocate the vector even if there is enough capacity.
1649 // (4) A stack pointer is compatible with the fbvector's allocator.
1652 template <class T, class A>
1653 T* relinquish(fbvector<T, A>& v) {
1655 v.impl_.b_ = v.impl_.e_ = v.impl_.z_ = nullptr;
1659 template <class T, class A>
1660 void attach(fbvector<T, A>& v, T* data, size_t sz, size_t cap) {
1661 assert(v.data() == nullptr);
1663 v.impl_.e_ = data + sz;
1664 v.impl_.z_ = data + cap;
1667 } // namespace folly