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 * For high-level documentation and usage examples see
19 * folly/docs/small_vector.md
21 * @author Jordan DeLong <delong.j@fb.com>
28 #include <type_traits>
33 #include <boost/operators.hpp>
34 #include <boost/type_traits.hpp>
35 #include <boost/mpl/if.hpp>
36 #include <boost/mpl/eval_if.hpp>
37 #include <boost/mpl/vector.hpp>
38 #include <boost/mpl/front.hpp>
39 #include <boost/mpl/filter_view.hpp>
40 #include <boost/mpl/identity.hpp>
41 #include <boost/mpl/placeholders.hpp>
42 #include <boost/mpl/empty.hpp>
43 #include <boost/mpl/size.hpp>
44 #include <boost/mpl/count.hpp>
45 #include <boost/mpl/max.hpp>
47 #include <folly/FormatTraits.h>
48 #include <folly/Malloc.h>
49 #include <folly/Portability.h>
50 #include <folly/portability/Malloc.h>
52 #if defined(__GNUC__) && (FOLLY_X64 || FOLLY_PPC64)
53 # include <folly/SmallLocks.h>
54 # define FB_PACK_ATTR FOLLY_PACK_ATTR
55 # define FB_PACK_PUSH FOLLY_PACK_PUSH
56 # define FB_PACK_POP FOLLY_PACK_POP
63 // Ignore shadowing warnings within this file, so includers can use -Wshadow.
64 #pragma GCC diagnostic push
65 #pragma GCC diagnostic ignored "-Wshadow"
69 //////////////////////////////////////////////////////////////////////
71 namespace small_vector_policy {
73 //////////////////////////////////////////////////////////////////////
76 * A flag which makes us refuse to use the heap at all. If we
77 * overflow the in situ capacity we throw an exception.
81 //////////////////////////////////////////////////////////////////////
83 } // small_vector_policy
85 //////////////////////////////////////////////////////////////////////
87 template<class T, std::size_t M, class A, class B, class C>
90 //////////////////////////////////////////////////////////////////////
95 * Move a range to a range of uninitialized memory. Assumes the
96 * ranges don't overlap.
99 typename std::enable_if<
100 !FOLLY_IS_TRIVIALLY_COPYABLE(T)
102 moveToUninitialized(T* first, T* last, T* out) {
105 for (; first != last; ++first, ++idx) {
106 new (&out[idx]) T(std::move(*first));
109 // Even for callers trying to give the strong guarantee
110 // (e.g. push_back) it's ok to assume here that we don't have to
111 // move things back and that it was a copy constructor that
112 // threw: if someone throws from a move constructor the effects
114 for (std::size_t i = 0; i < idx; ++i) {
121 // Specialization for trivially copyable types.
123 typename std::enable_if<
124 FOLLY_IS_TRIVIALLY_COPYABLE(T)
126 moveToUninitialized(T* first, T* last, T* out) {
127 std::memmove(out, first, (last - first) * sizeof *first);
131 * Move objects in memory to the right into some uninitialized
132 * memory, where the region overlaps. This doesn't just use
133 * std::move_backward because move_backward only works if all the
134 * memory is initialized to type T already.
137 typename std::enable_if<
138 !FOLLY_IS_TRIVIALLY_COPYABLE(T)
140 moveObjectsRight(T* first, T* lastConstructed, T* realLast) {
141 if (lastConstructed == realLast) {
145 T* end = first - 1; // Past the end going backwards.
146 T* out = realLast - 1;
147 T* in = lastConstructed - 1;
149 for (; in != end && out >= lastConstructed; --in, --out) {
150 new (out) T(std::move(*in));
152 for (; in != end; --in, --out) {
153 *out = std::move(*in);
155 for (; out >= lastConstructed; --out) {
159 // We want to make sure the same stuff is uninitialized memory
160 // if we exit via an exception (this is to make sure we provide
161 // the basic exception safety guarantee for insert functions).
162 if (out < lastConstructed) {
163 out = lastConstructed - 1;
165 for (auto it = out + 1; it != realLast; ++it) {
172 // Specialization for trivially copyable types. The call to
173 // std::move_backward here will just turn into a memmove. (TODO:
174 // change to std::is_trivially_copyable when that works.)
176 typename std::enable_if<
177 FOLLY_IS_TRIVIALLY_COPYABLE(T)
179 moveObjectsRight(T* first, T* lastConstructed, T* realLast) {
180 std::move_backward(first, lastConstructed, realLast);
184 * Populate a region of memory using `op' to construct elements. If
185 * anything throws, undo what we did.
187 template<class T, class Function>
188 void populateMemForward(T* mem, std::size_t n, Function const& op) {
191 for (size_t i = 0; i < n; ++i) {
196 for (std::size_t i = 0; i < idx; ++i) {
203 template<class SizeType, bool ShouldUseHeap>
204 struct IntegralSizePolicy {
205 typedef SizeType InternalSizeType;
207 IntegralSizePolicy() : size_(0) {}
210 static constexpr std::size_t policyMaxSize() {
211 return SizeType(~kExternMask);
214 std::size_t doSize() const {
215 return size_ & ~kExternMask;
218 std::size_t isExtern() const {
219 return kExternMask & size_;
222 void setExtern(bool b) {
224 size_ |= kExternMask;
226 size_ &= ~kExternMask;
230 void setSize(std::size_t sz) {
231 assert(sz <= policyMaxSize());
232 size_ = (kExternMask & size_) | SizeType(sz);
235 void swapSizePolicy(IntegralSizePolicy& o) {
236 std::swap(size_, o.size_);
240 static bool const kShouldUseHeap = ShouldUseHeap;
243 static SizeType const kExternMask =
244 kShouldUseHeap ? SizeType(1) << (sizeof(SizeType) * 8 - 1)
251 * If you're just trying to use this class, ignore everything about
252 * this next small_vector_base class thing.
254 * The purpose of this junk is to minimize sizeof(small_vector<>)
255 * and allow specifying the template parameters in whatever order is
256 * convenient for the user. There's a few extra steps here to try
257 * to keep the error messages at least semi-reasonable.
259 * Apologies for all the black magic.
261 namespace mpl = boost::mpl;
262 template<class Value,
263 std::size_t RequestedMaxInline,
267 struct small_vector_base {
268 typedef mpl::vector<InPolicyA,InPolicyB,InPolicyC> PolicyList;
271 * Determine the size type
273 typedef typename mpl::filter_view<
275 boost::is_integral<mpl::placeholders::_1>
277 typedef typename mpl::eval_if<
278 mpl::empty<Integrals>,
279 mpl::identity<std::size_t>,
280 mpl::front<Integrals>
283 static_assert(std::is_unsigned<SizeType>::value,
284 "Size type should be an unsigned integral type");
285 static_assert(mpl::size<Integrals>::value == 0 ||
286 mpl::size<Integrals>::value == 1,
287 "Multiple size types specified in small_vector<>");
290 * Determine whether we should allow spilling to the heap or not.
292 typedef typename mpl::count<
293 PolicyList,small_vector_policy::NoHeap
296 static_assert(HasNoHeap::value == 0 || HasNoHeap::value == 1,
297 "Multiple copies of small_vector_policy::NoHeap "
298 "supplied; this is probably a mistake");
301 * Make the real policy base classes.
303 typedef IntegralSizePolicy<SizeType,!HasNoHeap::value>
307 * Now inherit from them all. This is done in such a convoluted
308 * way to make sure we get the empty base optimizaton on all these
309 * types to keep sizeof(small_vector<>) minimal.
311 typedef boost::totally_ordered1<
312 small_vector<Value,RequestedMaxInline,InPolicyA,InPolicyB,InPolicyC>,
318 T* pointerFlagSet(T* p) {
319 return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(p) | 1);
322 bool pointerFlagGet(T* p) {
323 return reinterpret_cast<uintptr_t>(p) & 1;
326 T* pointerFlagClear(T* p) {
327 return reinterpret_cast<T*>(
328 reinterpret_cast<uintptr_t>(p) & ~uintptr_t(1));
330 inline void* shiftPointer(void* p, size_t sizeBytes) {
331 return static_cast<char*>(p) + sizeBytes;
335 //////////////////////////////////////////////////////////////////////
337 template<class Value,
338 std::size_t RequestedMaxInline = 1,
339 class PolicyA = void,
340 class PolicyB = void,
341 class PolicyC = void>
343 : public detail::small_vector_base<
344 Value,RequestedMaxInline,PolicyA,PolicyB,PolicyC
347 typedef typename detail::small_vector_base<
348 Value,RequestedMaxInline,PolicyA,PolicyB,PolicyC
350 typedef typename BaseType::InternalSizeType InternalSizeType;
353 * Figure out the max number of elements we should inline. (If
354 * the user asks for less inlined elements than we can fit unioned
355 * into our value_type*, we will inline more than they asked.)
358 MaxInline = boost::mpl::max<
359 boost::mpl::int_<sizeof(Value*) / sizeof(Value)>,
360 boost::mpl::int_<RequestedMaxInline>
365 typedef std::size_t size_type;
366 typedef Value value_type;
367 typedef value_type& reference;
368 typedef value_type const& const_reference;
369 typedef value_type* iterator;
370 typedef value_type const* const_iterator;
371 typedef std::ptrdiff_t difference_type;
373 typedef std::reverse_iterator<iterator> reverse_iterator;
374 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
376 explicit small_vector() = default;
378 small_vector(small_vector const& o) {
382 std::uninitialized_copy(o.begin(), o.end(), begin());
384 if (this->isExtern()) {
392 small_vector(small_vector&& o)
393 noexcept(std::is_nothrow_move_constructible<Value>::value) {
397 std::uninitialized_copy(std::make_move_iterator(o.begin()),
398 std::make_move_iterator(o.end()),
400 this->setSize(o.size());
404 small_vector(std::initializer_list<value_type> il) {
405 constructImpl(il.begin(), il.end(), std::false_type());
408 explicit small_vector(size_type n, value_type const& t = value_type()) {
413 explicit small_vector(Arg arg1, Arg arg2) {
414 // Forward using std::is_arithmetic to get to the proper
415 // implementation; this disambiguates between the iterators and
416 // (size_t, value_type) meaning for this constructor.
417 constructImpl(arg1, arg2, std::is_arithmetic<Arg>());
421 for (auto& t : *this) {
424 if (this->isExtern()) {
429 small_vector& operator=(small_vector const& o) {
430 assign(o.begin(), o.end());
434 small_vector& operator=(small_vector&& o) {
435 // TODO: optimization:
436 // if both are internal, use move assignment where possible
437 if (this == &o) return *this;
443 bool operator==(small_vector const& o) const {
444 return size() == o.size() && std::equal(begin(), end(), o.begin());
447 bool operator<(small_vector const& o) const {
448 return std::lexicographical_compare(begin(), end(), o.begin(), o.end());
451 static constexpr size_type max_size() {
452 return !BaseType::kShouldUseHeap ? MaxInline
453 : BaseType::policyMaxSize();
456 size_type size() const { return this->doSize(); }
457 bool empty() const { return !size(); }
459 iterator begin() { return data(); }
460 iterator end() { return data() + size(); }
461 const_iterator begin() const { return data(); }
462 const_iterator end() const { return data() + size(); }
463 const_iterator cbegin() const { return begin(); }
464 const_iterator cend() const { return end(); }
466 reverse_iterator rbegin() { return reverse_iterator(end()); }
467 reverse_iterator rend() { return reverse_iterator(begin()); }
469 const_reverse_iterator rbegin() const {
470 return const_reverse_iterator(end());
473 const_reverse_iterator rend() const {
474 return const_reverse_iterator(begin());
477 const_reverse_iterator crbegin() const { return rbegin(); }
478 const_reverse_iterator crend() const { return rend(); }
481 * Usually one of the simplest functions in a Container-like class
482 * but a bit more complex here. We have to handle all combinations
483 * of in-place vs. heap between this and o.
485 * Basic guarantee only. Provides the nothrow guarantee iff our
486 * value_type has a nothrow move or copy constructor.
488 void swap(small_vector& o) {
489 using std::swap; // Allow ADL on swap for our value_type.
491 if (this->isExtern() && o.isExtern()) {
492 this->swapSizePolicy(o);
494 auto thisCapacity = this->capacity();
495 auto oCapacity = o.capacity();
497 std::swap(unpackHack(&u.pdata_.heap_), unpackHack(&o.u.pdata_.heap_));
499 this->setCapacity(oCapacity);
500 o.setCapacity(thisCapacity);
505 if (!this->isExtern() && !o.isExtern()) {
506 auto& oldSmall = size() < o.size() ? *this : o;
507 auto& oldLarge = size() < o.size() ? o : *this;
509 for (size_type i = 0; i < oldSmall.size(); ++i) {
510 swap(oldSmall[i], oldLarge[i]);
513 size_type i = oldSmall.size();
514 const size_type ci = i;
516 for (; i < oldLarge.size(); ++i) {
517 auto addr = oldSmall.begin() + i;
518 new (addr) value_type(std::move(oldLarge[i]));
519 oldLarge[i].~value_type();
523 for (; i < oldLarge.size(); ++i) {
524 oldLarge[i].~value_type();
526 oldLarge.setSize(ci);
530 oldLarge.setSize(ci);
534 // isExtern != o.isExtern()
535 auto& oldExtern = o.isExtern() ? o : *this;
536 auto& oldIntern = o.isExtern() ? *this : o;
538 auto oldExternCapacity = oldExtern.capacity();
539 auto oldExternHeap = oldExtern.u.pdata_.heap_;
541 auto buff = oldExtern.u.buffer();
544 for (; i < oldIntern.size(); ++i) {
545 new (&buff[i]) value_type(std::move(oldIntern[i]));
546 oldIntern[i].~value_type();
549 for (size_type kill = 0; kill < i; ++kill) {
550 buff[kill].~value_type();
552 for (; i < oldIntern.size(); ++i) {
553 oldIntern[i].~value_type();
555 oldIntern.setSize(0);
556 oldExtern.u.pdata_.heap_ = oldExternHeap;
557 oldExtern.setCapacity(oldExternCapacity);
560 oldIntern.u.pdata_.heap_ = oldExternHeap;
561 this->swapSizePolicy(o);
562 oldIntern.setCapacity(oldExternCapacity);
565 void resize(size_type sz) {
567 erase(begin() + sz, end());
571 detail::populateMemForward(begin() + size(), sz - size(),
572 [&] (void* p) { new (p) value_type(); }
577 void resize(size_type sz, value_type const& v) {
579 erase(begin() + sz, end());
583 detail::populateMemForward(begin() + size(), sz - size(),
584 [&] (void* p) { new (p) value_type(v); }
589 value_type* data() noexcept {
590 return this->isExtern() ? u.heap() : u.buffer();
593 value_type const* data() const noexcept {
594 return this->isExtern() ? u.heap() : u.buffer();
597 template<class ...Args>
598 iterator emplace(const_iterator p, Args&&... args) {
600 emplace_back(std::forward<Args>(args)...);
605 * We implement emplace at places other than at the back with a
606 * temporary for exception safety reasons. It is possible to
607 * avoid having to do this, but it becomes hard to maintain the
608 * basic exception safety guarantee (unless you respond to a copy
609 * constructor throwing by clearing the whole vector).
611 * The reason for this is that otherwise you have to destruct an
612 * element before constructing this one in its place---if the
613 * constructor throws, you either need a nothrow default
614 * constructor or a nothrow copy/move to get something back in the
615 * "gap", and the vector requirements don't guarantee we have any
616 * of these. Clearing the whole vector is a legal response in
617 * this situation, but it seems like this implementation is easy
618 * enough and probably better.
620 return insert(p, value_type(std::forward<Args>(args)...));
623 void reserve(size_type sz) {
627 size_type capacity() const {
628 if (this->isExtern()) {
629 if (u.hasCapacity()) {
630 return *u.getCapacity();
632 return malloc_usable_size(u.pdata_.heap_) / sizeof(value_type);
637 void shrink_to_fit() {
638 if (!this->isExtern()) {
642 small_vector tmp(begin(), end());
646 template<class ...Args>
647 void emplace_back(Args&&... args) {
648 // call helper function for static dispatch of special cases
649 emplaceBack(std::forward<Args>(args)...);
652 void emplace_back(const value_type& t) {
655 void emplace_back(value_type& t) {
659 void emplace_back(value_type&& t) {
660 push_back(std::move(t));
663 void push_back(value_type&& t) {
664 if (capacity() == size()) {
665 makeSize(std::max(size_type(2), 3 * size() / 2), &t, size());
667 new (end()) value_type(std::move(t));
669 this->setSize(size() + 1);
672 void push_back(value_type const& t) {
673 // TODO: we'd like to make use of makeSize (it can be optimized better,
674 // because it manipulates the internals)
675 // unfortunately the current implementation only supports moving from
676 // a supplied rvalue, and doing an extra move just to reuse it is a perf
678 if (size() == capacity()) {// && isInside(&t)) {
680 emplaceBack(std::move(tmp));
690 iterator insert(const_iterator constp, value_type&& t) {
691 iterator p = unconst(constp);
694 push_back(std::move(t));
698 auto offset = p - begin();
700 if (capacity() == size()) {
701 makeSize(size() + 1, &t, offset);
702 this->setSize(this->size() + 1);
704 makeSize(size() + 1);
705 detail::moveObjectsRight(data() + offset,
707 data() + size() + 1);
708 this->setSize(size() + 1);
709 data()[offset] = std::move(t);
711 return begin() + offset;
715 iterator insert(const_iterator p, value_type const& t) {
716 // Make a copy and forward to the rvalue value_type&& overload
718 return insert(p, value_type(t));
721 iterator insert(const_iterator pos, size_type n, value_type const& val) {
722 auto offset = pos - begin();
723 makeSize(size() + n);
724 detail::moveObjectsRight(data() + offset,
726 data() + size() + n);
727 this->setSize(size() + n);
728 std::generate_n(begin() + offset, n, [&] { return val; });
729 return begin() + offset;
733 iterator insert(const_iterator p, Arg arg1, Arg arg2) {
734 // Forward using std::is_arithmetic to get to the proper
735 // implementation; this disambiguates between the iterators and
736 // (size_t, value_type) meaning for this function.
737 return insertImpl(unconst(p), arg1, arg2, std::is_arithmetic<Arg>());
740 iterator insert(const_iterator p, std::initializer_list<value_type> il) {
741 return insert(p, il.begin(), il.end());
744 iterator erase(const_iterator q) {
745 std::move(unconst(q) + 1, end(), unconst(q));
746 (data() + size() - 1)->~value_type();
747 this->setSize(size() - 1);
751 iterator erase(const_iterator q1, const_iterator q2) {
752 if (q1 == q2) return unconst(q1);
753 std::move(unconst(q2), end(), unconst(q1));
754 for (auto it = (end() - std::distance(q1, q2)); it != end(); ++it) {
757 this->setSize(size() - (q2 - q1));
762 erase(begin(), end());
766 void assign(Arg first, Arg last) {
768 insert(end(), first, last);
771 void assign(std::initializer_list<value_type> il) {
772 assign(il.begin(), il.end());
775 void assign(size_type n, const value_type& t) {
780 reference front() { assert(!empty()); return *begin(); }
781 reference back() { assert(!empty()); return *(end() - 1); }
782 const_reference front() const { assert(!empty()); return *begin(); }
783 const_reference back() const { assert(!empty()); return *(end() - 1); }
785 reference operator[](size_type i) {
787 return *(begin() + i);
790 const_reference operator[](size_type i) const {
792 return *(begin() + i);
795 reference at(size_type i) {
797 throw std::out_of_range("index out of range");
802 const_reference at(size_type i) const {
804 throw std::out_of_range("index out of range");
812 * This is doing the same like emplace_back, but we need this helper
813 * to catch the special case - see the next overload function..
815 template<class ...Args>
816 void emplaceBack(Args&&... args) {
817 makeSize(size() + 1);
818 new (end()) value_type(std::forward<Args>(args)...);
819 this->setSize(size() + 1);
822 static iterator unconst(const_iterator it) {
823 return const_cast<iterator>(it);
827 * g++ doesn't allow you to bind a non-const reference to a member
828 * of a packed structure, presumably because it would make it too
829 * easy to accidentally make an unaligned memory access?
831 template<class T> static T& unpackHack(T* p) {
835 // The std::false_type argument is part of disambiguating the
836 // iterator insert functions from integral types (see insert().)
838 iterator insertImpl(iterator pos, It first, It last, std::false_type) {
839 typedef typename std::iterator_traits<It>::iterator_category categ;
840 if (std::is_same<categ,std::input_iterator_tag>::value) {
841 auto offset = pos - begin();
842 while (first != last) {
843 pos = insert(pos, *first++);
846 return begin() + offset;
849 auto distance = std::distance(first, last);
850 auto offset = pos - begin();
851 makeSize(size() + distance);
852 detail::moveObjectsRight(data() + offset,
854 data() + size() + distance);
855 this->setSize(size() + distance);
856 std::copy_n(first, distance, begin() + offset);
857 return begin() + offset;
860 iterator insertImpl(iterator pos, size_type n, const value_type& val,
862 // The true_type means this should call the size_t,value_type
863 // overload. (See insert().)
864 return insert(pos, n, val);
867 // The std::false_type argument came from std::is_arithmetic as part
868 // of disambiguating an overload (see the comment in the
871 void constructImpl(It first, It last, std::false_type) {
872 typedef typename std::iterator_traits<It>::iterator_category categ;
873 if (std::is_same<categ,std::input_iterator_tag>::value) {
874 // With iterators that only allow a single pass, we can't really
875 // do anything sane here.
876 while (first != last) {
877 emplace_back(*first++);
882 auto distance = std::distance(first, last);
884 this->setSize(distance);
886 detail::populateMemForward(data(), distance,
887 [&] (void* p) { new (p) value_type(*first++); }
890 if (this->isExtern()) {
897 void doConstruct(size_type n, value_type const& val) {
901 detail::populateMemForward(data(), n,
902 [&] (void* p) { new (p) value_type(val); }
905 if (this->isExtern()) {
912 // The true_type means we should forward to the size_t,value_type
914 void constructImpl(size_type n, value_type const& val, std::true_type) {
918 void makeSize(size_type size, value_type* v = nullptr) {
919 makeSize(size, v, size - 1);
923 * Ensure we have a large enough memory region to be size `size'.
924 * Will move/copy elements if we are spilling to heap_ or needed to
925 * allocate a new region, but if resized in place doesn't initialize
926 * anything in the new region. In any case doesn't change size().
927 * Supports insertion of new element during reallocation by given
928 * pointer to new element and position of new element.
929 * NOTE: If reallocation is not needed, and new element should be
930 * inserted in the middle of vector (not at the end), do the move
931 * objects and insertion outside the function, otherwise exception is thrown.
933 void makeSize(size_type size, value_type* v, size_type pos) {
934 if (size > this->max_size()) {
935 throw std::length_error("max_size exceeded in small_vector");
937 if (size <= this->capacity()) {
941 auto needBytes = size * sizeof(value_type);
942 // If the capacity isn't explicitly stored inline, but the heap
943 // allocation is grown to over some threshold, we should store
944 // a capacity at the front of the heap allocation.
945 bool heapifyCapacity =
946 !kHasInlineCapacity && needBytes > kHeapifyCapacityThreshold;
947 if (heapifyCapacity) {
948 needBytes += kHeapifyCapacitySize;
950 auto const sizeBytes = goodMallocSize(needBytes);
951 void* newh = checkedMalloc(sizeBytes);
952 // We expect newh to be at least 2-aligned, because we want to
953 // use its least significant bit as a flag.
954 assert(!detail::pointerFlagGet(newh));
956 value_type* newp = static_cast<value_type*>(
958 detail::shiftPointer(newh, kHeapifyCapacitySize) :
964 new (&newp[pos]) value_type(std::move(*v));
970 // move old elements to the left of the new one
972 detail::moveToUninitialized(begin(), begin() + pos, newp);
974 newp[pos].~value_type();
979 // move old elements to the right of the new one
982 detail::moveToUninitialized(begin() + pos, end(), newp + pos + 1);
985 for (size_type i = 0; i <= pos; ++i) {
986 newp[i].~value_type();
992 // move without inserting new element
994 detail::moveToUninitialized(begin(), end(), newp);
1000 for (auto& val : *this) {
1004 if (this->isExtern()) {
1007 auto availableSizeBytes = sizeBytes;
1008 if (heapifyCapacity) {
1009 u.pdata_.heap_ = detail::pointerFlagSet(newh);
1010 availableSizeBytes -= kHeapifyCapacitySize;
1012 u.pdata_.heap_ = newh;
1014 this->setExtern(true);
1015 this->setCapacity(availableSizeBytes / sizeof(value_type));
1019 * This will set the capacity field, stored inline in the storage_ field
1020 * if there is sufficient room to store it.
1022 void setCapacity(size_type newCapacity) {
1023 assert(this->isExtern());
1024 if (u.hasCapacity()) {
1025 assert(newCapacity < std::numeric_limits<InternalSizeType>::max());
1026 *u.getCapacity() = InternalSizeType(newCapacity);
1031 struct HeapPtrWithCapacity {
1033 InternalSizeType capacity_;
1035 InternalSizeType* getCapacity() {
1041 // Lower order bit of heap_ is used as flag to indicate whether capacity is
1042 // stored at the front of the heap allocation.
1045 InternalSizeType* getCapacity() {
1046 assert(detail::pointerFlagGet(heap_));
1047 return static_cast<InternalSizeType*>(
1048 detail::pointerFlagClear(heap_));
1052 #if (FOLLY_X64 || FOLLY_PPC64)
1053 typedef unsigned char InlineStorageType[sizeof(value_type) * MaxInline];
1055 typedef typename std::aligned_storage<
1056 sizeof(value_type) * MaxInline,
1058 >::type InlineStorageType;
1061 static bool const kHasInlineCapacity =
1062 sizeof(HeapPtrWithCapacity) < sizeof(InlineStorageType);
1064 // This value should we multiple of word size.
1065 static size_t const kHeapifyCapacitySize = sizeof(
1066 typename std::aligned_storage<
1067 sizeof(InternalSizeType),
1070 // Threshold to control capacity heapifying.
1071 static size_t const kHeapifyCapacityThreshold =
1072 100 * kHeapifyCapacitySize;
1074 typedef typename std::conditional<
1076 HeapPtrWithCapacity,
1078 >::type PointerType;
1081 explicit Data() { pdata_.heap_ = 0; }
1084 InlineStorageType storage_;
1086 value_type* buffer() noexcept {
1087 void* vp = &storage_;
1088 return static_cast<value_type*>(vp);
1090 value_type const* buffer() const noexcept {
1091 return const_cast<Data*>(this)->buffer();
1093 value_type* heap() noexcept {
1094 if (kHasInlineCapacity || !detail::pointerFlagGet(pdata_.heap_)) {
1095 return static_cast<value_type*>(pdata_.heap_);
1097 return static_cast<value_type*>(
1098 detail::shiftPointer(
1099 detail::pointerFlagClear(pdata_.heap_), kHeapifyCapacitySize));
1101 value_type const* heap() const noexcept {
1102 return const_cast<Data*>(this)->heap();
1105 bool hasCapacity() const {
1106 return kHasInlineCapacity || detail::pointerFlagGet(pdata_.heap_);
1108 InternalSizeType* getCapacity() {
1109 return pdata_.getCapacity();
1111 InternalSizeType* getCapacity() const {
1112 return const_cast<Data*>(this)->getCapacity();
1116 auto vp = detail::pointerFlagClear(pdata_.heap_);
1123 //////////////////////////////////////////////////////////////////////
1125 // Basic guarantee only, or provides the nothrow guarantee iff T has a
1126 // nothrow move or copy constructor.
1127 template<class T, std::size_t MaxInline, class A, class B, class C>
1128 void swap(small_vector<T,MaxInline,A,B,C>& a,
1129 small_vector<T,MaxInline,A,B,C>& b) {
1133 //////////////////////////////////////////////////////////////////////
1138 template <class T, size_t M, class A, class B, class C>
1139 struct IndexableTraits<small_vector<T, M, A, B, C>>
1140 : public IndexableTraitsSeq<small_vector<T, M, A, B, C>> {
1143 } // namespace detail
1145 } // namespace folly
1147 #pragma GCC diagnostic pop
1150 # undef FB_PACK_ATTR
1151 # undef FB_PACK_PUSH