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_, size_type(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 if (LIKELY(n != 0)) {
434 std::memset(dest, 0, sizeof(T) * n);
440 for (; b != e; ++b) S_construct(b);
443 for (; b >= dest; --b) b->~T();
449 static void S_uninitialized_fill_n(T* dest, size_type n, const T& value) {
453 for (; b != e; ++b) S_construct(b, value);
455 S_destroy_range(dest, b);
460 //---------------------------------------------------------------------------
461 // uninitialized_copy
463 // it is possible to add an optimization for the case where
464 // It = move(T*) and IsRelocatable<T> and Is0Initiailizable<T>
467 template <typename It>
468 void M_uninitialized_copy_e(It first, It last) {
469 D_uninitialized_copy_a(impl_.e_, first, last);
470 impl_.e_ += std::distance(first, last);
473 template <typename It>
474 void M_uninitialized_move_e(It first, It last) {
475 D_uninitialized_move_a(impl_.e_, first, last);
476 impl_.e_ += std::distance(first, last);
480 template <typename It>
481 void D_uninitialized_copy_a(T* dest, It first, It last) {
482 if (usingStdAllocator::value) {
483 if (folly::IsTriviallyCopyable<T>::value) {
484 S_uninitialized_copy_bits(dest, first, last);
486 S_uninitialized_copy(dest, first, last);
489 S_uninitialized_copy_a(impl_, dest, first, last);
493 template <typename It>
494 void D_uninitialized_move_a(T* dest, It first, It last) {
495 D_uninitialized_copy_a(dest,
496 std::make_move_iterator(first), std::make_move_iterator(last));
500 template <typename It>
502 S_uninitialized_copy_a(Allocator& a, T* dest, It first, It last) {
505 for (; first != last; ++first, ++b)
506 std::allocator_traits<Allocator>::construct(a, b, *first);
508 S_destroy_range_a(a, dest, b);
514 template <typename It>
515 static void S_uninitialized_copy(T* dest, It first, It last) {
518 for (; first != last; ++first, ++b)
519 S_construct(b, *first);
521 S_destroy_range(dest, b);
527 S_uninitialized_copy_bits(T* dest, const T* first, const T* last) {
529 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
534 S_uninitialized_copy_bits(T* dest, std::move_iterator<T*> first,
535 std::move_iterator<T*> last) {
536 T* bFirst = first.base();
537 T* bLast = last.base();
538 if (bLast != bFirst) {
539 std::memcpy((void*)dest, (void*)bFirst, (bLast - bFirst) * sizeof(T));
543 template <typename It>
545 S_uninitialized_copy_bits(T* dest, It first, It last) {
546 S_uninitialized_copy(dest, first, last);
549 //---------------------------------------------------------------------------
552 // This function is "unsafe": it assumes that the iterator can be advanced at
553 // least n times. However, as a private function, that unsafety is managed
554 // wholly by fbvector itself.
556 template <typename It>
557 static It S_copy_n(T* dest, It first, size_type n) {
559 for (; dest != e; ++dest, ++first) *dest = *first;
563 static const T* S_copy_n(T* dest, const T* first, size_type n) {
564 if (folly::IsTriviallyCopyable<T>::value) {
565 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
568 return S_copy_n<const T*>(dest, first, n);
572 static std::move_iterator<T*>
573 S_copy_n(T* dest, std::move_iterator<T*> mIt, size_type n) {
574 if (folly::IsTriviallyCopyable<T>::value) {
575 T* first = mIt.base();
576 std::memcpy((void*)dest, (void*)first, n * sizeof(T));
577 return std::make_move_iterator(first + n);
579 return S_copy_n<std::move_iterator<T*>>(dest, mIt, n);
583 //===========================================================================
584 //---------------------------------------------------------------------------
585 // relocation helpers
588 // Relocation is divided into three parts:
591 // Performs the actual movement of data from point a to point b.
594 // Destroys the old data.
597 // Destoys the new data and restores the old data.
599 // The three steps are used because there may be an exception after part 1
600 // has completed. If that is the case, then relocate_undo can nullify the
601 // initial move. Otherwise, relocate_done performs the last bit of tidying
604 // The relocation trio may use either memcpy, move, or copy. It is decided
605 // by the following case statement:
607 // IsRelocatable && usingStdAllocator -> memcpy
608 // has_nothrow_move && usingStdAllocator -> move
609 // cannot copy -> move
612 // If the class is non-copyable then it must be movable. However, if the
613 // move constructor is not noexcept, i.e. an error could be thrown, then
614 // relocate_undo will be unable to restore the old data, for fear of a
615 // second exception being thrown. This is a known and unavoidable
616 // deficiency. In lieu of a strong exception guarantee, relocate_undo does
617 // the next best thing: it provides a weak exception guarantee by
618 // destorying the new data, but leaving the old data in an indeterminate
619 // state. Note that that indeterminate state will be valid, since the
620 // old data has not been destroyed; it has merely been the source of a
621 // move, which is required to leave the source in a valid state.
624 void M_relocate(T* newB) {
625 relocate_move(newB, impl_.b_, impl_.e_);
626 relocate_done(newB, impl_.b_, impl_.e_);
629 // dispatch type trait
630 typedef std::integral_constant<bool,
631 folly::IsRelocatable<T>::value && usingStdAllocator::value
632 > relocate_use_memcpy;
634 typedef std::integral_constant<bool,
635 (std::is_nothrow_move_constructible<T>::value
636 && usingStdAllocator::value)
637 || !std::is_copy_constructible<T>::value
641 void relocate_move(T* dest, T* first, T* last) {
642 relocate_move_or_memcpy(dest, first, last, relocate_use_memcpy());
645 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::true_type) {
646 if (first != nullptr) {
647 std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
651 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::false_type) {
652 relocate_move_or_copy(dest, first, last, relocate_use_move());
655 void relocate_move_or_copy(T* dest, T* first, T* last, std::true_type) {
656 D_uninitialized_move_a(dest, first, last);
659 void relocate_move_or_copy(T* dest, T* first, T* last, std::false_type) {
660 D_uninitialized_copy_a(dest, first, last);
664 void relocate_done(T* /*dest*/, T* first, T* last) noexcept {
665 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
666 // used memcpy; data has been relocated, do not call destructor
668 D_destroy_range_a(first, last);
673 void relocate_undo(T* dest, T* first, T* last) noexcept {
674 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
675 // used memcpy, old data is still valid, nothing to do
676 } else if (std::is_nothrow_move_constructible<T>::value &&
677 usingStdAllocator::value) {
678 // noexcept move everything back, aka relocate_move
679 relocate_move(first, dest, dest + (last - first));
680 } else if (!std::is_copy_constructible<T>::value) {
682 D_destroy_range_a(dest, dest + (last - first));
684 // used copy, old data is still valid
685 D_destroy_range_a(dest, dest + (last - first));
690 //===========================================================================
691 //---------------------------------------------------------------------------
692 // construct/copy/destroy
695 fbvector() = default;
697 explicit fbvector(const Allocator& a) : impl_(a) {}
699 explicit fbvector(size_type n, const Allocator& a = Allocator())
701 { M_uninitialized_fill_n_e(n); }
703 fbvector(size_type n, VT value, const Allocator& a = Allocator())
705 { M_uninitialized_fill_n_e(n, value); }
707 template <class It, class Category = typename
708 std::iterator_traits<It>::iterator_category>
709 fbvector(It first, It last, const Allocator& a = Allocator())
710 : fbvector(first, last, a, Category()) {}
712 fbvector(const fbvector& other)
713 : impl_(other.size(), A::select_on_container_copy_construction(other.impl_))
714 { M_uninitialized_copy_e(other.begin(), other.end()); }
716 fbvector(fbvector&& other) noexcept : impl_(std::move(other.impl_)) {}
718 fbvector(const fbvector& other, const Allocator& a)
719 : fbvector(other.begin(), other.end(), a) {}
721 /* may throw */ fbvector(fbvector&& other, const Allocator& a) : impl_(a) {
722 if (impl_ == other.impl_) {
723 impl_.swapData(other.impl_);
725 impl_.init(other.size());
726 M_uninitialized_move_e(other.begin(), other.end());
730 fbvector(std::initializer_list<T> il, const Allocator& a = Allocator())
731 : fbvector(il.begin(), il.end(), a) {}
733 ~fbvector() = default; // the cleanup occurs in impl_
735 fbvector& operator=(const fbvector& other) {
736 if (UNLIKELY(this == &other)) return *this;
738 if (!usingStdAllocator::value &&
739 A::propagate_on_container_copy_assignment::value) {
740 if (impl_ != other.impl_) {
741 // can't use other's different allocator to clean up self
744 (Allocator&)impl_ = (Allocator&)other.impl_;
747 assign(other.begin(), other.end());
751 fbvector& operator=(fbvector&& other) {
752 if (UNLIKELY(this == &other)) return *this;
753 moveFrom(std::move(other), moveIsSwap());
757 fbvector& operator=(std::initializer_list<T> il) {
758 assign(il.begin(), il.end());
762 template <class It, class Category = typename
763 std::iterator_traits<It>::iterator_category>
764 void assign(It first, It last) {
765 assign(first, last, Category());
768 void assign(size_type n, VT value) {
769 if (n > capacity()) {
770 // Not enough space. Do not reserve in place, since we will
771 // discard the old values anyways.
772 if (dataIsInternalAndNotVT(value)) {
773 T copy(std::move(value));
775 M_uninitialized_fill_n_e(n, copy);
778 M_uninitialized_fill_n_e(n, value);
780 } else if (n <= size()) {
781 auto newE = impl_.b_ + n;
782 std::fill(impl_.b_, newE, value);
783 M_destroy_range_e(newE);
785 std::fill(impl_.b_, impl_.e_, value);
786 M_uninitialized_fill_n_e(n - size(), value);
790 void assign(std::initializer_list<T> il) {
791 assign(il.begin(), il.end());
794 allocator_type get_allocator() const noexcept {
800 // contract dispatch for iterator types fbvector(It first, It last)
801 template <class ForwardIterator>
802 fbvector(ForwardIterator first, ForwardIterator last,
803 const Allocator& a, std::forward_iterator_tag)
804 : impl_(std::distance(first, last), a)
805 { M_uninitialized_copy_e(first, last); }
807 template <class InputIterator>
808 fbvector(InputIterator first, InputIterator last,
809 const Allocator& a, std::input_iterator_tag)
811 { for (; first != last; ++first) emplace_back(*first); }
813 // contract dispatch for allocator movement in operator=(fbvector&&)
815 moveFrom(fbvector&& other, std::true_type) {
816 swap(impl_, other.impl_);
818 void moveFrom(fbvector&& other, std::false_type) {
819 if (impl_ == other.impl_) {
820 impl_.swapData(other.impl_);
822 impl_.reset(other.size());
823 M_uninitialized_move_e(other.begin(), other.end());
827 // contract dispatch for iterator types in assign(It first, It last)
828 template <class ForwardIterator>
829 void assign(ForwardIterator first, ForwardIterator last,
830 std::forward_iterator_tag) {
831 const size_t newSize = std::distance(first, last);
832 if (newSize > capacity()) {
833 impl_.reset(newSize);
834 M_uninitialized_copy_e(first, last);
835 } else if (newSize <= size()) {
836 auto newEnd = std::copy(first, last, impl_.b_);
837 M_destroy_range_e(newEnd);
839 auto mid = S_copy_n(impl_.b_, first, size());
840 M_uninitialized_copy_e<decltype(last)>(mid, last);
844 template <class InputIterator>
845 void assign(InputIterator first, InputIterator last,
846 std::input_iterator_tag) {
848 for (; first != last && p != impl_.e_; ++first, ++p) {
852 M_destroy_range_e(p);
854 for (; first != last; ++first) emplace_back(*first);
858 // contract dispatch for aliasing under VT optimization
859 bool dataIsInternalAndNotVT(const T& t) {
860 if (should_pass_by_value::value) return false;
861 return dataIsInternal(t);
863 bool dataIsInternal(const T& t) {
864 return UNLIKELY(impl_.b_ <= std::addressof(t) &&
865 std::addressof(t) < impl_.e_);
869 //===========================================================================
870 //---------------------------------------------------------------------------
874 iterator begin() noexcept {
877 const_iterator begin() const noexcept {
880 iterator end() noexcept {
883 const_iterator end() const noexcept {
886 reverse_iterator rbegin() noexcept {
887 return reverse_iterator(end());
889 const_reverse_iterator rbegin() const noexcept {
890 return const_reverse_iterator(end());
892 reverse_iterator rend() noexcept {
893 return reverse_iterator(begin());
895 const_reverse_iterator rend() const noexcept {
896 return const_reverse_iterator(begin());
899 const_iterator cbegin() const noexcept {
902 const_iterator cend() const noexcept {
905 const_reverse_iterator crbegin() const noexcept {
906 return const_reverse_iterator(end());
908 const_reverse_iterator crend() const noexcept {
909 return const_reverse_iterator(begin());
912 //===========================================================================
913 //---------------------------------------------------------------------------
917 size_type size() const noexcept {
918 return size_type(impl_.e_ - impl_.b_);
921 size_type max_size() const noexcept {
922 // good luck gettin' there
923 return ~size_type(0);
926 void resize(size_type n) {
928 M_destroy_range_e(impl_.b_ + n);
931 M_uninitialized_fill_n_e(n - size());
935 void resize(size_type n, VT t) {
937 M_destroy_range_e(impl_.b_ + n);
938 } else if (dataIsInternalAndNotVT(t) && n > capacity()) {
941 M_uninitialized_fill_n_e(n - size(), copy);
944 M_uninitialized_fill_n_e(n - size(), t);
948 size_type capacity() const noexcept {
949 return size_type(impl_.z_ - impl_.b_);
952 bool empty() const noexcept {
953 return impl_.b_ == impl_.e_;
956 void reserve(size_type n) {
957 if (n <= capacity()) return;
958 if (impl_.b_ && reserve_in_place(n)) return;
960 auto newCap = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
961 auto newB = M_allocate(newCap);
965 M_deallocate(newB, newCap);
969 M_deallocate(impl_.b_, size_type(impl_.z_ - impl_.b_));
970 impl_.z_ = newB + newCap;
971 impl_.e_ = newB + (impl_.e_ - impl_.b_);
975 void shrink_to_fit() noexcept {
981 auto const newCapacityBytes = folly::goodMallocSize(size() * sizeof(T));
982 auto const newCap = newCapacityBytes / sizeof(T);
983 auto const oldCap = capacity();
985 if (newCap >= oldCap) return;
988 // xallocx() will shrink to precisely newCapacityBytes (which was generated
989 // by goodMallocSize()) if it successfully shrinks in place.
990 if ((usingJEMalloc() && usingStdAllocator::value) &&
991 newCapacityBytes >= folly::jemallocMinInPlaceExpandable &&
992 xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
993 impl_.z_ += newCap - oldCap;
995 T* newB; // intentionally uninitialized
997 newB = M_allocate(newCap);
1001 M_deallocate(newB, newCap);
1002 return; // swallow the error
1008 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
1009 impl_.z_ = newB + newCap;
1010 impl_.e_ = newB + (impl_.e_ - impl_.b_);
1017 bool reserve_in_place(size_type n) {
1018 if (!usingStdAllocator::value || !usingJEMalloc()) return false;
1020 // jemalloc can never grow in place blocks smaller than 4096 bytes.
1021 if ((impl_.z_ - impl_.b_) * sizeof(T) <
1022 folly::jemallocMinInPlaceExpandable) return false;
1024 auto const newCapacityBytes = folly::goodMallocSize(n * sizeof(T));
1026 if (xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
1027 impl_.z_ = impl_.b_ + newCapacityBytes / sizeof(T);
1033 //===========================================================================
1034 //---------------------------------------------------------------------------
1038 reference operator[](size_type n) {
1042 const_reference operator[](size_type n) const {
1046 const_reference at(size_type n) const {
1047 if (UNLIKELY(n >= size())) {
1048 std::__throw_out_of_range("fbvector: index is greater than size.");
1052 reference at(size_type n) {
1053 auto const& cThis = *this;
1054 return const_cast<reference>(cThis.at(n));
1060 const_reference front() const {
1066 return impl_.e_[-1];
1068 const_reference back() const {
1070 return impl_.e_[-1];
1073 //===========================================================================
1074 //---------------------------------------------------------------------------
1078 T* data() noexcept {
1081 const T* data() const noexcept {
1085 //===========================================================================
1086 //---------------------------------------------------------------------------
1087 // modifiers (common)
1090 template <class... Args>
1091 void emplace_back(Args&&... args) {
1092 if (impl_.e_ != impl_.z_) {
1093 M_construct(impl_.e_, std::forward<Args>(args)...);
1096 emplace_back_aux(std::forward<Args>(args)...);
1101 push_back(const T& value) {
1102 if (impl_.e_ != impl_.z_) {
1103 M_construct(impl_.e_, value);
1106 emplace_back_aux(value);
1111 push_back(T&& value) {
1112 if (impl_.e_ != impl_.z_) {
1113 M_construct(impl_.e_, std::move(value));
1116 emplace_back_aux(std::move(value));
1123 M_destroy(impl_.e_);
1126 void swap(fbvector& other) noexcept {
1127 if (!usingStdAllocator::value &&
1128 A::propagate_on_container_swap::value)
1129 swap(impl_, other.impl_);
1130 else impl_.swapData(other.impl_);
1133 void clear() noexcept {
1134 M_destroy_range_e(impl_.b_);
1139 // std::vector implements a similar function with a different growth
1140 // strategy: empty() ? 1 : capacity() * 2.
1142 // fbvector grows differently on two counts:
1145 // Instead of growing to size 1 from empty, fbvector allocates at least
1146 // 64 bytes. You may still use reserve to reserve a lesser amount of
1149 // For medium-sized vectors, the growth strategy is 1.5x. See the docs
1151 // This does not apply to very small or very large fbvectors. This is a
1153 // A nice addition to fbvector would be the capability of having a user-
1154 // defined growth strategy, probably as part of the allocator.
1157 size_type computePushBackCapacity() const {
1158 if (capacity() == 0) {
1159 return std::max(64 / sizeof(T), size_type(1));
1161 if (capacity() < folly::jemallocMinInPlaceExpandable / sizeof(T)) {
1162 return capacity() * 2;
1164 if (capacity() > 4096 * 32 / sizeof(T)) {
1165 return capacity() * 2;
1167 return (capacity() * 3 + 1) / 2;
1170 template <class... Args>
1171 void emplace_back_aux(Args&&... args);
1173 //===========================================================================
1174 //---------------------------------------------------------------------------
1175 // modifiers (erase)
1178 iterator erase(const_iterator position) {
1179 return erase(position, position + 1);
1182 iterator erase(const_iterator first, const_iterator last) {
1183 assert(isValid(first) && isValid(last));
1184 assert(first <= last);
1185 if (first != last) {
1186 if (last == end()) {
1187 M_destroy_range_e((iterator)first);
1189 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1190 D_destroy_range_a((iterator)first, (iterator)last);
1191 if (last - first >= cend() - last) {
1192 std::memcpy((void*)first, (void*)last, (cend() - last) * sizeof(T));
1194 std::memmove((iterator)first, last, (cend() - last) * sizeof(T));
1196 impl_.e_ -= (last - first);
1198 std::copy(std::make_move_iterator((iterator)last),
1199 std::make_move_iterator(end()), (iterator)first);
1200 auto newEnd = impl_.e_ - std::distance(first, last);
1201 M_destroy_range_e(newEnd);
1205 return (iterator)first;
1208 //===========================================================================
1209 //---------------------------------------------------------------------------
1210 // modifiers (insert)
1211 private: // we have the private section first because it defines some macros
1213 bool isValid(const_iterator it) {
1214 return cbegin() <= it && it <= cend();
1217 size_type computeInsertCapacity(size_type n) {
1218 size_type nc = std::max(computePushBackCapacity(), size() + n);
1219 size_type ac = folly::goodMallocSize(nc * sizeof(T)) / sizeof(T);
1223 //---------------------------------------------------------------------------
1225 // make_window takes an fbvector, and creates an uninitialized gap (a
1226 // window) at the given position, of the given size. The fbvector must
1227 // have enough capacity.
1229 // Explanation by picture.
1233 // make_window here of size 3
1237 // If something goes wrong and the window must be destroyed, use
1238 // undo_window to provide a weak exception guarantee. It destroys
1243 //---------------------------------------------------------------------------
1245 // wrap_frame takes an inverse window and relocates an fbvector around it.
1246 // The fbvector must have at least as many elements as the left ledge.
1248 // Explanation by picture.
1251 // fbvector: inverse window:
1252 // 123456789______ _____abcde_______
1256 // _______________ 12345abcde6789___
1258 //---------------------------------------------------------------------------
1260 // insert_use_fresh_memory returns true iff the fbvector should use a fresh
1261 // block of memory for the insertion. If the fbvector does not have enough
1262 // spare capacity, then it must return true. Otherwise either true or false
1265 //---------------------------------------------------------------------------
1267 // These three functions, make_window, wrap_frame, and
1268 // insert_use_fresh_memory, can be combined into a uniform interface.
1269 // Since that interface involves a lot of case-work, it is built into
1270 // some macros: FOLLY_FBVECTOR_INSERT_(PRE|START|TRY|END)
1271 // Macros are used in an attempt to let GCC perform better optimizations,
1272 // especially control flow optimization.
1275 //---------------------------------------------------------------------------
1278 void make_window(iterator position, size_type n) {
1279 // The result is guaranteed to be non-negative, so use an unsigned type:
1280 size_type tail = std::distance(position, impl_.e_);
1283 relocate_move(position + n, position, impl_.e_);
1284 relocate_done(position + n, position, impl_.e_);
1287 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1288 std::memmove(position + n, position, tail * sizeof(T));
1291 D_uninitialized_move_a(impl_.e_, impl_.e_ - n, impl_.e_);
1293 std::copy_backward(std::make_move_iterator(position),
1294 std::make_move_iterator(impl_.e_ - n), impl_.e_);
1296 D_destroy_range_a(impl_.e_ - n, impl_.e_ + n);
1301 D_destroy_range_a(position, position + n);
1306 void undo_window(iterator position, size_type n) noexcept {
1307 D_destroy_range_a(position + n, impl_.e_);
1308 impl_.e_ = position;
1311 //---------------------------------------------------------------------------
1314 void wrap_frame(T* ledge, size_type idx, size_type n) {
1315 assert(size() >= idx);
1318 relocate_move(ledge, impl_.b_, impl_.b_ + idx);
1320 relocate_move(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1322 relocate_undo(ledge, impl_.b_, impl_.b_ + idx);
1325 relocate_done(ledge, impl_.b_, impl_.b_ + idx);
1326 relocate_done(ledge + idx + n, impl_.b_ + idx, impl_.e_);
1329 //---------------------------------------------------------------------------
1332 bool insert_use_fresh(bool at_end, size_type n) {
1334 if (size() + n <= capacity()) return false;
1335 if (reserve_in_place(size() + n)) return false;
1339 if (size() + n > capacity()) return true;
1344 //---------------------------------------------------------------------------
1347 #define FOLLY_FBVECTOR_INSERT_PRE(cpos, n) \
1348 if (n == 0) return (iterator)cpos; \
1349 bool at_end = cpos == cend(); \
1350 bool fresh = insert_use_fresh(at_end, n); \
1354 // check for internal data (technically not required by the standard)
1356 #define FOLLY_FBVECTOR_INSERT_START(cpos, n) \
1358 assert(isValid(cpos)); \
1360 T* position = const_cast<T*>(cpos); \
1361 size_type idx = std::distance(impl_.b_, position); \
1363 size_type newCap; /* intentionally uninitialized */ \
1366 newCap = computeInsertCapacity(n); \
1367 b = M_allocate(newCap); \
1370 make_window(position, n); \
1377 T* start = b + idx; \
1381 // construct the inserted elements
1383 #define FOLLY_FBVECTOR_INSERT_TRY(cpos, n) \
1386 M_deallocate(b, newCap); \
1389 undo_window(position, n); \
1399 wrap_frame(b, idx, n); \
1403 // delete the inserted elements (exception has been thrown)
1405 #define FOLLY_FBVECTOR_INSERT_END(cpos, n) \
1406 M_deallocate(b, newCap); \
1409 if (impl_.b_) M_deallocate(impl_.b_, capacity()); \
1410 impl_.set(b, size() + n, newCap); \
1411 return impl_.b_ + idx; \
1416 //---------------------------------------------------------------------------
1420 template <class... Args>
1421 iterator emplace(const_iterator cpos, Args&&... args) {
1422 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1423 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1424 M_construct(start, std::forward<Args>(args)...);
1425 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1427 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1430 iterator insert(const_iterator cpos, const T& value) {
1431 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1432 if (dataIsInternal(value)) return insert(cpos, T(value));
1433 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1434 M_construct(start, value);
1435 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1437 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1440 iterator insert(const_iterator cpos, T&& value) {
1441 FOLLY_FBVECTOR_INSERT_PRE(cpos, 1)
1442 if (dataIsInternal(value)) return insert(cpos, T(std::move(value)));
1443 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1444 M_construct(start, std::move(value));
1445 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1447 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1450 iterator insert(const_iterator cpos, size_type n, VT value) {
1451 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1452 if (dataIsInternalAndNotVT(value)) return insert(cpos, n, T(value));
1453 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1454 D_uninitialized_fill_n_a(start, n, value);
1455 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1456 D_destroy_range_a(start, start + n);
1457 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1460 template <class It, class Category = typename
1461 std::iterator_traits<It>::iterator_category>
1462 iterator insert(const_iterator cpos, It first, It last) {
1463 return insert(cpos, first, last, Category());
1466 iterator insert(const_iterator cpos, std::initializer_list<T> il) {
1467 return insert(cpos, il.begin(), il.end());
1470 //---------------------------------------------------------------------------
1471 // insert dispatch for iterator types
1474 template <class FIt>
1475 iterator insert(const_iterator cpos, FIt first, FIt last,
1476 std::forward_iterator_tag) {
1477 size_type n = std::distance(first, last);
1478 FOLLY_FBVECTOR_INSERT_PRE(cpos, n)
1479 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1480 D_uninitialized_copy_a(start, first, last);
1481 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1482 D_destroy_range_a(start, start + n);
1483 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1486 template <class IIt>
1487 iterator insert(const_iterator cpos, IIt first, IIt last,
1488 std::input_iterator_tag) {
1489 T* position = const_cast<T*>(cpos);
1490 assert(isValid(position));
1491 size_type idx = std::distance(begin(), position);
1493 fbvector storage(std::make_move_iterator(position),
1494 std::make_move_iterator(end()),
1495 A::select_on_container_copy_construction(impl_));
1496 M_destroy_range_e(position);
1497 for (; first != last; ++first) emplace_back(*first);
1498 insert(cend(), std::make_move_iterator(storage.begin()),
1499 std::make_move_iterator(storage.end()));
1500 return impl_.b_ + idx;
1503 //===========================================================================
1504 //---------------------------------------------------------------------------
1505 // lexicographical functions (others from boost::totally_ordered superclass)
1508 bool operator==(const fbvector& other) const {
1509 return size() == other.size() && std::equal(begin(), end(), other.begin());
1512 bool operator<(const fbvector& other) const {
1513 return std::lexicographical_compare(
1514 begin(), end(), other.begin(), other.end());
1517 //===========================================================================
1518 //---------------------------------------------------------------------------
1522 template <class _T, class _A>
1523 friend _T* relinquish(fbvector<_T, _A>&);
1525 template <class _T, class _A>
1526 friend void attach(fbvector<_T, _A>&, _T* data, size_t sz, size_t cap);
1528 }; // class fbvector
1531 //=============================================================================
1532 //-----------------------------------------------------------------------------
1533 // outlined functions (gcc, you finicky compiler you)
1535 template <typename T, typename Allocator>
1536 template <class... Args>
1537 void fbvector<T, Allocator>::emplace_back_aux(Args&&... args) {
1538 size_type byte_sz = folly::goodMallocSize(
1539 computePushBackCapacity() * sizeof(T));
1540 if (usingStdAllocator::value
1542 && ((impl_.z_ - impl_.b_) * sizeof(T) >=
1543 folly::jemallocMinInPlaceExpandable)) {
1544 // Try to reserve in place.
1545 // Ask xallocx to allocate in place at least size()+1 and at most sz space.
1546 // xallocx will allocate as much as possible within that range, which
1547 // is the best possible outcome: if sz space is available, take it all,
1548 // otherwise take as much as possible. If nothing is available, then fail.
1549 // In this fashion, we never relocate if there is a possibility of
1550 // expanding in place, and we never reallocate by less than the desired
1551 // amount unless we cannot expand further. Hence we will not reallocate
1552 // sub-optimally twice in a row (modulo the blocking memory being freed).
1553 size_type lower = folly::goodMallocSize(sizeof(T) + size() * sizeof(T));
1554 size_type upper = byte_sz;
1555 size_type extra = upper - lower;
1560 if ((actual = xallocx(p, lower, extra, 0)) >= lower) {
1561 impl_.z_ = impl_.b_ + actual / sizeof(T);
1562 M_construct(impl_.e_, std::forward<Args>(args)...);
1568 // Reallocation failed. Perform a manual relocation.
1569 size_type sz = byte_sz / sizeof(T);
1570 auto newB = M_allocate(sz);
1571 auto newE = newB + size();
1573 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1574 // For linear memory access, relocate before construction.
1575 // By the test condition, relocate is noexcept.
1576 // Note that there is no cleanup to do if M_construct throws - that's
1577 // one of the beauties of relocation.
1578 // Benchmarks for this code have high variance, and seem to be close.
1579 relocate_move(newB, impl_.b_, impl_.e_);
1580 M_construct(newE, std::forward<Args>(args)...);
1583 M_construct(newE, std::forward<Args>(args)...);
1588 M_destroy(newE - 1);
1593 M_deallocate(newB, sz);
1596 if (impl_.b_) M_deallocate(impl_.b_, size());
1599 impl_.z_ = newB + sz;
1602 //=============================================================================
1603 //-----------------------------------------------------------------------------
1604 // specialized functions
1606 template <class T, class A>
1607 void swap(fbvector<T, A>& lhs, fbvector<T, A>& rhs) noexcept {
1611 //=============================================================================
1612 //-----------------------------------------------------------------------------
1618 template <class T, class A>
1619 struct IndexableTraits<fbvector<T, A>>
1620 : public IndexableTraitsSeq<fbvector<T, A>> {
1623 } // namespace detail
1625 template <class T, class A>
1626 void compactResize(fbvector<T, A>* v, size_t sz) {
1633 // relinquish and attach are not a members function specifically so that it is
1634 // awkward to call them. It is very easy to shoot yourself in the foot with
1637 // If you call relinquish, then it is your responsibility to free the data
1638 // and the storage, both of which may have been generated in a non-standard
1639 // way through the fbvector's allocator.
1641 // If you call attach, it is your responsibility to ensure that the fbvector
1642 // is fresh (size and capacity both zero), and that the supplied data is
1643 // capable of being manipulated by the allocator.
1644 // It is acceptable to supply a stack pointer IF:
1645 // (1) The vector's data does not outlive the stack pointer. This includes
1646 // extension of the data's life through a move operation.
1647 // (2) The pointer has enough capacity that the vector will never be
1649 // (3) Insert is not called on the vector; these functions have leeway to
1650 // relocate the vector even if there is enough capacity.
1651 // (4) A stack pointer is compatible with the fbvector's allocator.
1654 template <class T, class A>
1655 T* relinquish(fbvector<T, A>& v) {
1657 v.impl_.b_ = v.impl_.e_ = v.impl_.z_ = nullptr;
1661 template <class T, class A>
1662 void attach(fbvector<T, A>& v, T* data, size_t sz, size_t cap) {
1663 assert(v.data() == nullptr);
1665 v.impl_.e_ = data + sz;
1666 v.impl_.z_ = data + cap;
1669 } // namespace folly