2 * Copyright 2015 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.
25 #ifndef FOLLY_FBVECTOR_H
26 #define FOLLY_FBVECTOR_H
28 //=============================================================================
36 #include <type_traits>
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);
167 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) {
526 std::memcpy(dest, first, (last - first) * sizeof(T));
530 S_uninitialized_copy_bits(T* dest, std::move_iterator<T*> first,
531 std::move_iterator<T*> last) {
532 T* bFirst = first.base();
533 T* bLast = last.base();
534 std::memcpy(dest, bFirst, (bLast - bFirst) * sizeof(T));
537 template <typename It>
539 S_uninitialized_copy_bits(T* dest, It first, It last) {
540 S_uninitialized_copy(dest, first, last);
543 //---------------------------------------------------------------------------
546 // This function is "unsafe": it assumes that the iterator can be advanced at
547 // least n times. However, as a private function, that unsafety is managed
548 // wholly by fbvector itself.
550 template <typename It>
551 static It S_copy_n(T* dest, It first, size_type n) {
553 for (; dest != e; ++dest, ++first) *dest = *first;
557 static const T* S_copy_n(T* dest, const T* first, size_type n) {
558 if (folly::IsTriviallyCopyable<T>::value) {
559 std::memcpy(dest, first, n * sizeof(T));
562 return S_copy_n<const T*>(dest, first, n);
566 static std::move_iterator<T*>
567 S_copy_n(T* dest, std::move_iterator<T*> mIt, size_type n) {
568 if (folly::IsTriviallyCopyable<T>::value) {
569 T* first = mIt.base();
570 std::memcpy(dest, first, n * sizeof(T));
571 return std::make_move_iterator(first + n);
573 return S_copy_n<std::move_iterator<T*>>(dest, mIt, n);
577 //===========================================================================
578 //---------------------------------------------------------------------------
579 // relocation helpers
582 // Relocation is divided into three parts:
585 // Performs the actual movement of data from point a to point b.
588 // Destroys the old data.
591 // Destoys the new data and restores the old data.
593 // The three steps are used because there may be an exception after part 1
594 // has completed. If that is the case, then relocate_undo can nullify the
595 // initial move. Otherwise, relocate_done performs the last bit of tidying
598 // The relocation trio may use either memcpy, move, or copy. It is decided
599 // by the following case statement:
601 // IsRelocatable && usingStdAllocator -> memcpy
602 // has_nothrow_move && usingStdAllocator -> move
603 // cannot copy -> move
606 // If the class is non-copyable then it must be movable. However, if the
607 // move constructor is not noexcept, i.e. an error could be thrown, then
608 // relocate_undo will be unable to restore the old data, for fear of a
609 // second exception being thrown. This is a known and unavoidable
610 // deficiency. In lieu of a strong exception guarantee, relocate_undo does
611 // the next best thing: it provides a weak exception guarantee by
612 // destorying the new data, but leaving the old data in an indeterminate
613 // state. Note that that indeterminate state will be valid, since the
614 // old data has not been destroyed; it has merely been the source of a
615 // move, which is required to leave the source in a valid state.
618 void M_relocate(T* newB) {
619 relocate_move(newB, impl_.b_, impl_.e_);
620 relocate_done(newB, impl_.b_, impl_.e_);
623 // dispatch type trait
624 typedef std::integral_constant<bool,
625 folly::IsRelocatable<T>::value && usingStdAllocator::value
626 > relocate_use_memcpy;
628 typedef std::integral_constant<bool,
629 (std::is_nothrow_move_constructible<T>::value
630 && usingStdAllocator::value)
631 || !std::is_copy_constructible<T>::value
635 void relocate_move(T* dest, T* first, T* last) {
636 relocate_move_or_memcpy(dest, first, last, relocate_use_memcpy());
639 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::true_type) {
640 std::memcpy(dest, first, (last - first) * sizeof(T));
643 void relocate_move_or_memcpy(T* dest, T* first, T* last, std::false_type) {
644 relocate_move_or_copy(dest, first, last, relocate_use_move());
647 void relocate_move_or_copy(T* dest, T* first, T* last, std::true_type) {
648 D_uninitialized_move_a(dest, first, last);
651 void relocate_move_or_copy(T* dest, T* first, T* last, std::false_type) {
652 D_uninitialized_copy_a(dest, first, last);
656 void relocate_done(T* dest, T* first, T* last) noexcept {
657 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
658 // used memcpy; data has been relocated, do not call destructor
660 D_destroy_range_a(first, last);
665 void relocate_undo(T* dest, T* first, T* last) noexcept {
666 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
667 // used memcpy, old data is still valid, nothing to do
668 } else if (std::is_nothrow_move_constructible<T>::value &&
669 usingStdAllocator::value) {
670 // noexcept move everything back, aka relocate_move
671 relocate_move(first, dest, dest + (last - first));
672 } else if (!std::is_copy_constructible<T>::value) {
674 D_destroy_range_a(dest, dest + (last - first));
676 // used copy, old data is still valid
677 D_destroy_range_a(dest, dest + (last - first));
682 //===========================================================================
683 //---------------------------------------------------------------------------
684 // construct/copy/destroy
687 fbvector() = default;
689 explicit fbvector(const Allocator& a) : impl_(a) {}
691 explicit fbvector(size_type n, const Allocator& a = Allocator())
693 { M_uninitialized_fill_n_e(n); }
695 fbvector(size_type n, VT value, const Allocator& a = Allocator())
697 { M_uninitialized_fill_n_e(n, value); }
699 template <class It, class Category = typename
700 std::iterator_traits<It>::iterator_category>
701 fbvector(It first, It last, const Allocator& a = Allocator())
702 : fbvector(first, last, a, Category()) {}
704 fbvector(const fbvector& other)
705 : impl_(other.size(), A::select_on_container_copy_construction(other.impl_))
706 { M_uninitialized_copy_e(other.begin(), other.end()); }
708 fbvector(fbvector&& other) noexcept : impl_(std::move(other.impl_)) {}
710 fbvector(const fbvector& other, const Allocator& a)
711 : fbvector(other.begin(), other.end(), a) {}
713 /* may throw */ fbvector(fbvector&& other, const Allocator& a) : impl_(a) {
714 if (impl_ == other.impl_) {
715 impl_.swapData(other.impl_);
717 impl_.init(other.size());
718 M_uninitialized_move_e(other.begin(), other.end());
722 fbvector(std::initializer_list<T> il, const Allocator& a = Allocator())
723 : fbvector(il.begin(), il.end(), a) {}
725 ~fbvector() = default; // the cleanup occurs in impl_
727 fbvector& operator=(const fbvector& other) {
728 if (UNLIKELY(this == &other)) return *this;
730 if (!usingStdAllocator::value &&
731 A::propagate_on_container_copy_assignment::value) {
732 if (impl_ != other.impl_) {
733 // can't use other's different allocator to clean up self
736 (Allocator&)impl_ = (Allocator&)other.impl_;
739 assign(other.begin(), other.end());
743 fbvector& operator=(fbvector&& other) {
744 if (UNLIKELY(this == &other)) return *this;
745 moveFrom(std::move(other), moveIsSwap());
749 fbvector& operator=(std::initializer_list<T> il) {
750 assign(il.begin(), il.end());
754 template <class It, class Category = typename
755 std::iterator_traits<It>::iterator_category>
756 void assign(It first, It last) {
757 assign(first, last, Category());
760 void assign(size_type n, VT value) {
761 if (n > capacity()) {
762 // Not enough space. Do not reserve in place, since we will
763 // discard the old values anyways.
764 if (dataIsInternalAndNotVT(value)) {
765 T copy(std::move(value));
767 M_uninitialized_fill_n_e(n, copy);
770 M_uninitialized_fill_n_e(n, value);
772 } else if (n <= size()) {
773 auto newE = impl_.b_ + n;
774 std::fill(impl_.b_, newE, value);
775 M_destroy_range_e(newE);
777 std::fill(impl_.b_, impl_.e_, value);
778 M_uninitialized_fill_n_e(n - size(), value);
782 void assign(std::initializer_list<T> il) {
783 assign(il.begin(), il.end());
786 allocator_type get_allocator() const noexcept {
792 // contract dispatch for iterator types fbvector(It first, It last)
793 template <class ForwardIterator>
794 fbvector(ForwardIterator first, ForwardIterator last,
795 const Allocator& a, std::forward_iterator_tag)
796 : impl_(std::distance(first, last), a)
797 { M_uninitialized_copy_e(first, last); }
799 template <class InputIterator>
800 fbvector(InputIterator first, InputIterator last,
801 const Allocator& a, std::input_iterator_tag)
803 { for (; first != last; ++first) emplace_back(*first); }
805 // contract dispatch for allocator movement in operator=(fbvector&&)
807 moveFrom(fbvector&& other, std::true_type) {
808 swap(impl_, other.impl_);
810 void moveFrom(fbvector&& other, std::false_type) {
811 if (impl_ == other.impl_) {
812 impl_.swapData(other.impl_);
814 impl_.reset(other.size());
815 M_uninitialized_move_e(other.begin(), other.end());
819 // contract dispatch for iterator types in assign(It first, It last)
820 template <class ForwardIterator>
821 void assign(ForwardIterator first, ForwardIterator last,
822 std::forward_iterator_tag) {
823 const size_t newSize = std::distance(first, last);
824 if (newSize > capacity()) {
825 impl_.reset(newSize);
826 M_uninitialized_copy_e(first, last);
827 } else if (newSize <= size()) {
828 auto newEnd = std::copy(first, last, impl_.b_);
829 M_destroy_range_e(newEnd);
831 auto mid = S_copy_n(impl_.b_, first, size());
832 M_uninitialized_copy_e<decltype(last)>(mid, last);
836 template <class InputIterator>
837 void assign(InputIterator first, InputIterator last,
838 std::input_iterator_tag) {
840 for (; first != last && p != impl_.e_; ++first, ++p) {
844 M_destroy_range_e(p);
846 for (; first != last; ++first) emplace_back(*first);
850 // contract dispatch for aliasing under VT optimization
851 bool dataIsInternalAndNotVT(const T& t) {
852 if (should_pass_by_value::value) return false;
853 return dataIsInternal(t);
855 bool dataIsInternal(const T& t) {
856 return UNLIKELY(impl_.b_ <= std::addressof(t) &&
857 std::addressof(t) < impl_.e_);
861 //===========================================================================
862 //---------------------------------------------------------------------------
866 iterator begin() noexcept {
869 const_iterator begin() const noexcept {
872 iterator end() noexcept {
875 const_iterator end() const noexcept {
878 reverse_iterator rbegin() noexcept {
879 return reverse_iterator(end());
881 const_reverse_iterator rbegin() const noexcept {
882 return const_reverse_iterator(end());
884 reverse_iterator rend() noexcept {
885 return reverse_iterator(begin());
887 const_reverse_iterator rend() const noexcept {
888 return const_reverse_iterator(begin());
891 const_iterator cbegin() const noexcept {
894 const_iterator cend() const noexcept {
897 const_reverse_iterator crbegin() const noexcept {
898 return const_reverse_iterator(end());
900 const_reverse_iterator crend() const noexcept {
901 return const_reverse_iterator(begin());
904 //===========================================================================
905 //---------------------------------------------------------------------------
909 size_type size() const noexcept {
910 return impl_.e_ - impl_.b_;
913 size_type max_size() const noexcept {
914 // good luck gettin' there
915 return ~size_type(0);
918 void resize(size_type n) {
920 M_destroy_range_e(impl_.b_ + n);
923 M_uninitialized_fill_n_e(n - size());
927 void resize(size_type n, VT t) {
929 M_destroy_range_e(impl_.b_ + n);
930 } else if (dataIsInternalAndNotVT(t) && n > capacity()) {
933 M_uninitialized_fill_n_e(n - size(), copy);
936 M_uninitialized_fill_n_e(n - size(), t);
940 size_type capacity() const noexcept {
941 return impl_.z_ - impl_.b_;
944 bool empty() const noexcept {
945 return impl_.b_ == impl_.e_;
948 void reserve(size_type n) {
949 if (n <= capacity()) return;
950 if (impl_.b_ && reserve_in_place(n)) return;
952 auto newCap = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
953 auto newB = M_allocate(newCap);
957 M_deallocate(newB, newCap);
961 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
962 impl_.z_ = newB + newCap;
963 impl_.e_ = newB + (impl_.e_ - impl_.b_);
967 void shrink_to_fit() noexcept {
968 auto const newCapacityBytes = folly::goodMallocSize(size() * sizeof(T));
969 auto const newCap = newCapacityBytes / sizeof(T);
970 auto const oldCap = capacity();
972 if (newCap >= oldCap) return;
975 // xallocx() will shrink to precisely newCapacityBytes (which was generated
976 // by goodMallocSize()) if it successfully shrinks in place.
977 if ((usingJEMalloc() && usingStdAllocator::value) &&
978 newCapacityBytes >= folly::jemallocMinInPlaceExpandable &&
979 xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
980 impl_.z_ += newCap - oldCap;
982 T* newB; // intentionally uninitialized
984 newB = M_allocate(newCap);
988 M_deallocate(newB, newCap);
989 return; // swallow the error
995 M_deallocate(impl_.b_, impl_.z_ - impl_.b_);
996 impl_.z_ = newB + newCap;
997 impl_.e_ = newB + (impl_.e_ - impl_.b_);
1004 bool reserve_in_place(size_type n) {
1005 if (!usingStdAllocator::value || !usingJEMalloc()) return false;
1007 // jemalloc can never grow in place blocks smaller than 4096 bytes.
1008 if ((impl_.z_ - impl_.b_) * sizeof(T) <
1009 folly::jemallocMinInPlaceExpandable) return false;
1011 auto const newCapacityBytes = folly::goodMallocSize(n * sizeof(T));
1013 if (xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
1014 impl_.z_ = impl_.b_ + newCapacityBytes / sizeof(T);
1020 //===========================================================================
1021 //---------------------------------------------------------------------------
1025 reference operator[](size_type n) {
1029 const_reference operator[](size_type n) const {
1033 const_reference at(size_type n) const {
1034 if (UNLIKELY(n >= size())) {
1035 throw std::out_of_range("fbvector: index is greater than size.");
1039 reference at(size_type n) {
1040 auto const& cThis = *this;
1041 return const_cast<reference>(cThis.at(n));
1047 const_reference front() const {
1053 return impl_.e_[-1];
1055 const_reference back() const {
1057 return impl_.e_[-1];
1060 //===========================================================================
1061 //---------------------------------------------------------------------------
1065 T* data() noexcept {
1068 const T* data() const noexcept {
1072 //===========================================================================
1073 //---------------------------------------------------------------------------
1074 // modifiers (common)
1077 template <class... Args>
1078 void emplace_back(Args&&... args) {
1079 if (impl_.e_ != impl_.z_) {
1080 M_construct(impl_.e_, std::forward<Args>(args)...);
1083 emplace_back_aux(std::forward<Args>(args)...);
1088 push_back(const T& value) {
1089 if (impl_.e_ != impl_.z_) {
1090 M_construct(impl_.e_, value);
1093 emplace_back_aux(value);
1098 push_back(T&& value) {
1099 if (impl_.e_ != impl_.z_) {
1100 M_construct(impl_.e_, std::move(value));
1103 emplace_back_aux(std::move(value));
1110 M_destroy(impl_.e_);
1113 void swap(fbvector& other) noexcept {
1114 if (!usingStdAllocator::value &&
1115 A::propagate_on_container_swap::value)
1116 swap(impl_, other.impl_);
1117 else impl_.swapData(other.impl_);
1120 void clear() noexcept {
1121 M_destroy_range_e(impl_.b_);
1126 // std::vector implements a similar function with a different growth
1127 // strategy: empty() ? 1 : capacity() * 2.
1129 // fbvector grows differently on two counts:
1132 // Instead of grwoing to size 1 from empty, and fbvector allocates at
1133 // least 64 bytes. You may still use reserve to reserve a lesser amount
1136 // For medium-sized vectors, the growth strategy is 1.5x. See the docs
1138 // This does not apply to very small or very large fbvectors. This is a
1140 // A nice addition to fbvector would be the capability of having a user-
1141 // defined growth strategy, probably as part of the allocator.
1144 size_type computePushBackCapacity() const {
1145 if (capacity() == 0) {
1146 return std::max(64 / sizeof(T), size_type(1));
1148 if (capacity() < folly::jemallocMinInPlaceExpandable / sizeof(T)) {
1149 return capacity() * 2;
1151 if (capacity() > 4096 * 32 / sizeof(T)) {
1152 return capacity() * 2;
1154 return (capacity() * 3 + 1) / 2;
1157 template <class... Args>
1158 void emplace_back_aux(Args&&... args);
1160 //===========================================================================
1161 //---------------------------------------------------------------------------
1162 // modifiers (erase)
1165 iterator erase(const_iterator position) {
1166 return erase(position, position + 1);
1169 iterator erase(const_iterator first, const_iterator last) {
1170 assert(isValid(first) && isValid(last));
1171 assert(first <= last);
1172 if (first != last) {
1173 if (last == end()) {
1174 M_destroy_range_e((iterator)first);
1176 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1177 D_destroy_range_a((iterator)first, (iterator)last);
1178 if (last - first >= cend() - last) {
1179 std::memcpy((iterator)first, last, (cend() - last) * sizeof(T));
1181 std::memmove((iterator)first, last, (cend() - last) * sizeof(T));
1183 impl_.e_ -= (last - first);
1185 std::copy(std::make_move_iterator((iterator)last),
1186 std::make_move_iterator(end()), (iterator)first);
1187 auto newEnd = impl_.e_ - std::distance(first, last);
1188 M_destroy_range_e(newEnd);
1192 return (iterator)first;
1195 //===========================================================================
1196 //---------------------------------------------------------------------------
1197 // modifiers (insert)
1198 private: // we have the private section first because it defines some macros
1200 bool isValid(const_iterator it) {
1201 return cbegin() <= it && it <= cend();
1204 size_type computeInsertCapacity(size_type n) {
1205 size_type nc = std::max(computePushBackCapacity(), size() + n);
1206 size_type ac = folly::goodMallocSize(nc * sizeof(T)) / sizeof(T);
1210 //---------------------------------------------------------------------------
1212 // make_window takes an fbvector, and creates an uninitialized gap (a
1213 // window) at the given position, of the given size. The fbvector must
1214 // have enough capacity.
1216 // Explanation by picture.
1220 // make_window here of size 3
1224 // If something goes wrong and the window must be destroyed, use
1225 // undo_window to provide a weak exception guarantee. It destroys
1230 //---------------------------------------------------------------------------
1232 // wrap_frame takes an inverse window and relocates an fbvector around it.
1233 // The fbvector must have at least as many elements as the left ledge.
1235 // Explanation by picture.
1238 // fbvector: inverse window:
1239 // 123456789______ _____abcde_______
1243 // _______________ 12345abcde6789___
1245 //---------------------------------------------------------------------------
1247 // insert_use_fresh_memory returns true iff the fbvector should use a fresh
1248 // block of memory for the insertion. If the fbvector does not have enough
1249 // spare capacity, then it must return true. Otherwise either true or false
1252 //---------------------------------------------------------------------------
1254 // These three functions, make_window, wrap_frame, and
1255 // insert_use_fresh_memory, can be combined into a uniform interface.
1256 // Since that interface involves a lot of case-work, it is built into
1257 // some macros: FOLLY_FBVECTOR_INSERT_(START|TRY|END)
1258 // Macros are used in an attempt to let GCC perform better optimizations,
1259 // especially control flow optimization.
1262 //---------------------------------------------------------------------------
1265 void make_window(iterator position, size_type n) {
1266 assert(isValid(position));
1267 assert(size() + n <= capacity());
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(const_iterator cposition, size_type n) {
1324 if (cposition == cend()) {
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_START(cpos, n) \
1339 assert(isValid(cpos)); \
1340 T* position = const_cast<T*>(cpos); \
1341 size_type idx = std::distance(impl_.b_, position); \
1342 bool fresh = insert_use_fresh(position, n); \
1344 size_type newCap = 0; \
1347 newCap = computeInsertCapacity(n); \
1348 b = M_allocate(newCap); \
1350 make_window(position, n); \
1354 T* start = b + idx; \
1358 // construct the inserted elements
1360 #define FOLLY_FBVECTOR_INSERT_TRY(cpos, n) \
1363 M_deallocate(b, newCap); \
1365 undo_window(position, n); \
1372 wrap_frame(b, idx, n); \
1376 // delete the inserted elements (exception has been thrown)
1378 #define FOLLY_FBVECTOR_INSERT_END(cpos, n) \
1379 M_deallocate(b, newCap); \
1382 if (impl_.b_) M_deallocate(impl_.b_, capacity()); \
1383 impl_.set(b, size() + n, newCap); \
1384 return impl_.b_ + idx; \
1389 //---------------------------------------------------------------------------
1393 template <class... Args>
1394 iterator emplace(const_iterator cpos, Args&&... args) {
1395 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1396 M_construct(start, std::forward<Args>(args)...);
1397 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1399 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1402 iterator insert(const_iterator cpos, const T& value) {
1403 if (dataIsInternal(value)) return insert(cpos, T(value));
1405 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1406 M_construct(start, value);
1407 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1409 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1412 iterator insert(const_iterator cpos, T&& value) {
1413 if (dataIsInternal(value)) return insert(cpos, T(std::move(value)));
1415 FOLLY_FBVECTOR_INSERT_START(cpos, 1)
1416 M_construct(start, std::move(value));
1417 FOLLY_FBVECTOR_INSERT_TRY(cpos, 1)
1419 FOLLY_FBVECTOR_INSERT_END(cpos, 1)
1422 iterator insert(const_iterator cpos, size_type n, VT value) {
1423 if (n == 0) return (iterator)cpos;
1424 if (dataIsInternalAndNotVT(value)) return insert(cpos, n, T(value));
1426 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1427 D_uninitialized_fill_n_a(start, n, value);
1428 FOLLY_FBVECTOR_INSERT_TRY(cpos, n)
1429 D_destroy_range_a(start, start + n);
1430 FOLLY_FBVECTOR_INSERT_END(cpos, n)
1433 template <class It, class Category = typename
1434 std::iterator_traits<It>::iterator_category>
1435 iterator insert(const_iterator cpos, It first, It last) {
1436 return insert(cpos, first, last, Category());
1439 iterator insert(const_iterator cpos, std::initializer_list<T> il) {
1440 return insert(cpos, il.begin(), il.end());
1443 //---------------------------------------------------------------------------
1444 // insert dispatch for iterator types
1447 template <class FIt>
1448 iterator insert(const_iterator cpos, FIt first, FIt last,
1449 std::forward_iterator_tag) {
1450 size_type n = std::distance(first, last);
1451 if (n == 0) return (iterator)cpos;
1453 FOLLY_FBVECTOR_INSERT_START(cpos, n)
1454 D_uninitialized_copy_a(start, first, last);
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 IIt>
1461 iterator insert(const_iterator cpos, IIt first, IIt last,
1462 std::input_iterator_tag) {
1463 T* position = const_cast<T*>(cpos);
1464 assert(isValid(position));
1465 size_type idx = std::distance(begin(), position);
1467 fbvector storage(std::make_move_iterator(position),
1468 std::make_move_iterator(end()),
1469 A::select_on_container_copy_construction(impl_));
1470 M_destroy_range_e(position);
1471 for (; first != last; ++first) emplace_back(*first);
1472 insert(cend(), std::make_move_iterator(storage.begin()),
1473 std::make_move_iterator(storage.end()));
1474 return impl_.b_ + idx;
1477 //===========================================================================
1478 //---------------------------------------------------------------------------
1479 // lexicographical functions (others from boost::totally_ordered superclass)
1482 bool operator==(const fbvector& other) const {
1483 return size() == other.size() && std::equal(begin(), end(), other.begin());
1486 bool operator<(const fbvector& other) const {
1487 return std::lexicographical_compare(
1488 begin(), end(), other.begin(), other.end());
1491 //===========================================================================
1492 //---------------------------------------------------------------------------
1496 template <class _T, class _A>
1497 friend _T* relinquish(fbvector<_T, _A>&);
1499 template <class _T, class _A>
1500 friend void attach(fbvector<_T, _A>&, _T* data, size_t sz, size_t cap);
1502 }; // class fbvector
1505 //=============================================================================
1506 //-----------------------------------------------------------------------------
1507 // outlined functions (gcc, you finicky compiler you)
1509 template <typename T, typename Allocator>
1510 template <class... Args>
1511 void fbvector<T, Allocator>::emplace_back_aux(Args&&... args) {
1512 size_type byte_sz = folly::goodMallocSize(
1513 computePushBackCapacity() * sizeof(T));
1514 if (usingStdAllocator::value
1516 && ((impl_.z_ - impl_.b_) * sizeof(T) >=
1517 folly::jemallocMinInPlaceExpandable)) {
1518 // Try to reserve in place.
1519 // Ask xallocx to allocate in place at least size()+1 and at most sz space.
1520 // xallocx will allocate as much as possible within that range, which
1521 // is the best possible outcome: if sz space is available, take it all,
1522 // otherwise take as much as possible. If nothing is available, then fail.
1523 // In this fashion, we never relocate if there is a possibility of
1524 // expanding in place, and we never reallocate by less than the desired
1525 // amount unless we cannot expand further. Hence we will not reallocate
1526 // sub-optimally twice in a row (modulo the blocking memory being freed).
1527 size_type lower = folly::goodMallocSize(sizeof(T) + size() * sizeof(T));
1528 size_type upper = byte_sz;
1529 size_type extra = upper - lower;
1534 if ((actual = xallocx(p, lower, extra, 0)) >= lower) {
1535 impl_.z_ = impl_.b_ + actual / sizeof(T);
1536 M_construct(impl_.e_, std::forward<Args>(args)...);
1542 // Reallocation failed. Perform a manual relocation.
1543 size_type sz = byte_sz / sizeof(T);
1544 auto newB = M_allocate(sz);
1545 auto newE = newB + size();
1547 if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
1548 // For linear memory access, relocate before construction.
1549 // By the test condition, relocate is noexcept.
1550 // Note that there is no cleanup to do if M_construct throws - that's
1551 // one of the beauties of relocation.
1552 // Benchmarks for this code have high variance, and seem to be close.
1553 relocate_move(newB, impl_.b_, impl_.e_);
1554 M_construct(newE, std::forward<Args>(args)...);
1557 M_construct(newE, std::forward<Args>(args)...);
1562 M_destroy(newE - 1);
1567 M_deallocate(newB, sz);
1570 if (impl_.b_) M_deallocate(impl_.b_, size());
1573 impl_.z_ = newB + sz;
1576 //=============================================================================
1577 //-----------------------------------------------------------------------------
1578 // specialized functions
1580 template <class T, class A>
1581 void swap(fbvector<T, A>& lhs, fbvector<T, A>& rhs) noexcept {
1585 //=============================================================================
1586 //-----------------------------------------------------------------------------
1589 template <class T, class A>
1590 void compactResize(fbvector<T, A>* v, size_t sz) {
1597 // relinquish and attach are not a members function specifically so that it is
1598 // awkward to call them. It is very easy to shoot yourself in the foot with
1601 // If you call relinquish, then it is your responsibility to free the data
1602 // and the storage, both of which may have been generated in a non-standard
1603 // way through the fbvector's allocator.
1605 // If you call attach, it is your responsibility to ensure that the fbvector
1606 // is fresh (size and capacity both zero), and that the supplied data is
1607 // capable of being manipulated by the allocator.
1608 // It is acceptable to supply a stack pointer IF:
1609 // (1) The vector's data does not outlive the stack pointer. This includes
1610 // extension of the data's life through a move operation.
1611 // (2) The pointer has enough capacity that the vector will never be
1613 // (3) Insert is not called on the vector; these functions have leeway to
1614 // relocate the vector even if there is enough capacity.
1615 // (4) A stack pointer is compatible with the fbvector's allocator.
1618 template <class T, class A>
1619 T* relinquish(fbvector<T, A>& v) {
1621 v.impl_.b_ = v.impl_.e_ = v.impl_.z_ = nullptr;
1625 template <class T, class A>
1626 void attach(fbvector<T, A>& v, T* data, size_t sz, size_t cap) {
1627 assert(v.data() == nullptr);
1629 v.impl_.e_ = data + sz;
1630 v.impl_.z_ = data + cap;
1633 } // namespace folly
1635 #endif // FOLLY_FBVECTOR_H