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>
46 #include <folly/FormatTraits.h>
47 #include <folly/Malloc.h>
48 #include <folly/Portability.h>
49 #include <folly/SmallLocks.h>
50 #include <folly/portability/Constexpr.h>
51 #include <folly/portability/Malloc.h>
53 // Ignore shadowing warnings within this file, so includers can use -Wshadow.
54 #pragma GCC diagnostic push
55 #pragma GCC diagnostic ignored "-Wshadow"
59 //////////////////////////////////////////////////////////////////////
61 namespace small_vector_policy {
63 //////////////////////////////////////////////////////////////////////
66 * A flag which makes us refuse to use the heap at all. If we
67 * overflow the in situ capacity we throw an exception.
71 //////////////////////////////////////////////////////////////////////
73 } // small_vector_policy
75 //////////////////////////////////////////////////////////////////////
77 template<class T, std::size_t M, class A, class B, class C>
80 //////////////////////////////////////////////////////////////////////
85 * Move a range to a range of uninitialized memory. Assumes the
86 * ranges don't overlap.
89 typename std::enable_if<
90 !FOLLY_IS_TRIVIALLY_COPYABLE(T)
92 moveToUninitialized(T* first, T* last, T* out) {
95 for (; first != last; ++first, ++idx) {
96 new (&out[idx]) T(std::move(*first));
99 // Even for callers trying to give the strong guarantee
100 // (e.g. push_back) it's ok to assume here that we don't have to
101 // move things back and that it was a copy constructor that
102 // threw: if someone throws from a move constructor the effects
104 for (std::size_t i = 0; i < idx; ++i) {
111 // Specialization for trivially copyable types.
113 typename std::enable_if<
114 FOLLY_IS_TRIVIALLY_COPYABLE(T)
116 moveToUninitialized(T* first, T* last, T* out) {
117 std::memmove(out, first, (last - first) * sizeof *first);
121 * Move objects in memory to the right into some uninitialized
122 * memory, where the region overlaps. This doesn't just use
123 * std::move_backward because move_backward only works if all the
124 * memory is initialized to type T already.
127 typename std::enable_if<
128 !FOLLY_IS_TRIVIALLY_COPYABLE(T)
130 moveObjectsRight(T* first, T* lastConstructed, T* realLast) {
131 if (lastConstructed == realLast) {
135 T* end = first - 1; // Past the end going backwards.
136 T* out = realLast - 1;
137 T* in = lastConstructed - 1;
139 for (; in != end && out >= lastConstructed; --in, --out) {
140 new (out) T(std::move(*in));
142 for (; in != end; --in, --out) {
143 *out = std::move(*in);
145 for (; out >= lastConstructed; --out) {
149 // We want to make sure the same stuff is uninitialized memory
150 // if we exit via an exception (this is to make sure we provide
151 // the basic exception safety guarantee for insert functions).
152 if (out < lastConstructed) {
153 out = lastConstructed - 1;
155 for (auto it = out + 1; it != realLast; ++it) {
162 // Specialization for trivially copyable types. The call to
163 // std::move_backward here will just turn into a memmove. (TODO:
164 // change to std::is_trivially_copyable when that works.)
166 typename std::enable_if<
167 FOLLY_IS_TRIVIALLY_COPYABLE(T)
169 moveObjectsRight(T* first, T* lastConstructed, T* realLast) {
170 std::move_backward(first, lastConstructed, realLast);
174 * Populate a region of memory using `op' to construct elements. If
175 * anything throws, undo what we did.
177 template<class T, class Function>
178 void populateMemForward(T* mem, std::size_t n, Function const& op) {
181 for (size_t i = 0; i < n; ++i) {
186 for (std::size_t i = 0; i < idx; ++i) {
193 template<class SizeType, bool ShouldUseHeap>
194 struct IntegralSizePolicy {
195 typedef SizeType InternalSizeType;
197 IntegralSizePolicy() : size_(0) {}
200 static constexpr std::size_t policyMaxSize() {
201 return SizeType(~kExternMask);
204 std::size_t doSize() const {
205 return size_ & ~kExternMask;
208 std::size_t isExtern() const {
209 return kExternMask & size_;
212 void setExtern(bool b) {
214 size_ |= kExternMask;
216 size_ &= ~kExternMask;
220 void setSize(std::size_t sz) {
221 assert(sz <= policyMaxSize());
222 size_ = (kExternMask & size_) | SizeType(sz);
225 void swapSizePolicy(IntegralSizePolicy& o) {
226 std::swap(size_, o.size_);
230 static bool const kShouldUseHeap = ShouldUseHeap;
233 static SizeType const kExternMask =
234 kShouldUseHeap ? SizeType(1) << (sizeof(SizeType) * 8 - 1)
241 * If you're just trying to use this class, ignore everything about
242 * this next small_vector_base class thing.
244 * The purpose of this junk is to minimize sizeof(small_vector<>)
245 * and allow specifying the template parameters in whatever order is
246 * convenient for the user. There's a few extra steps here to try
247 * to keep the error messages at least semi-reasonable.
249 * Apologies for all the black magic.
251 namespace mpl = boost::mpl;
252 template<class Value,
253 std::size_t RequestedMaxInline,
257 struct small_vector_base {
258 typedef mpl::vector<InPolicyA,InPolicyB,InPolicyC> PolicyList;
261 * Determine the size type
263 typedef typename mpl::filter_view<
265 boost::is_integral<mpl::placeholders::_1>
267 typedef typename mpl::eval_if<
268 mpl::empty<Integrals>,
269 mpl::identity<std::size_t>,
270 mpl::front<Integrals>
273 static_assert(std::is_unsigned<SizeType>::value,
274 "Size type should be an unsigned integral type");
275 static_assert(mpl::size<Integrals>::value == 0 ||
276 mpl::size<Integrals>::value == 1,
277 "Multiple size types specified in small_vector<>");
280 * Determine whether we should allow spilling to the heap or not.
282 typedef typename mpl::count<
283 PolicyList,small_vector_policy::NoHeap
286 static_assert(HasNoHeap::value == 0 || HasNoHeap::value == 1,
287 "Multiple copies of small_vector_policy::NoHeap "
288 "supplied; this is probably a mistake");
291 * Make the real policy base classes.
293 typedef IntegralSizePolicy<SizeType,!HasNoHeap::value>
297 * Now inherit from them all. This is done in such a convoluted
298 * way to make sure we get the empty base optimizaton on all these
299 * types to keep sizeof(small_vector<>) minimal.
301 typedef boost::totally_ordered1<
302 small_vector<Value,RequestedMaxInline,InPolicyA,InPolicyB,InPolicyC>,
308 T* pointerFlagSet(T* p) {
309 return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(p) | 1);
312 bool pointerFlagGet(T* p) {
313 return reinterpret_cast<uintptr_t>(p) & 1;
316 T* pointerFlagClear(T* p) {
317 return reinterpret_cast<T*>(
318 reinterpret_cast<uintptr_t>(p) & ~uintptr_t(1));
320 inline void* shiftPointer(void* p, size_t sizeBytes) {
321 return static_cast<char*>(p) + sizeBytes;
325 //////////////////////////////////////////////////////////////////////
327 template<class Value,
328 std::size_t RequestedMaxInline = 1,
329 class PolicyA = void,
330 class PolicyB = void,
331 class PolicyC = void>
333 : public detail::small_vector_base<
334 Value,RequestedMaxInline,PolicyA,PolicyB,PolicyC
337 typedef typename detail::small_vector_base<
338 Value,RequestedMaxInline,PolicyA,PolicyB,PolicyC
340 typedef typename BaseType::InternalSizeType InternalSizeType;
343 * Figure out the max number of elements we should inline. (If
344 * the user asks for less inlined elements than we can fit unioned
345 * into our value_type*, we will inline more than they asked.)
349 constexpr_max(sizeof(Value*) / sizeof(Value), RequestedMaxInline),
353 typedef std::size_t size_type;
354 typedef Value value_type;
355 typedef value_type& reference;
356 typedef value_type const& const_reference;
357 typedef value_type* iterator;
358 typedef value_type const* const_iterator;
359 typedef std::ptrdiff_t difference_type;
361 typedef std::reverse_iterator<iterator> reverse_iterator;
362 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
364 explicit small_vector() = default;
366 small_vector(small_vector const& o) {
370 std::uninitialized_copy(o.begin(), o.end(), begin());
372 if (this->isExtern()) {
380 small_vector(small_vector&& o)
381 noexcept(std::is_nothrow_move_constructible<Value>::value) {
385 std::uninitialized_copy(std::make_move_iterator(o.begin()),
386 std::make_move_iterator(o.end()),
388 this->setSize(o.size());
392 small_vector(std::initializer_list<value_type> il) {
393 constructImpl(il.begin(), il.end(), std::false_type());
396 explicit small_vector(size_type n, value_type const& t = value_type()) {
401 explicit small_vector(Arg arg1, Arg arg2) {
402 // Forward using std::is_arithmetic to get to the proper
403 // implementation; this disambiguates between the iterators and
404 // (size_t, value_type) meaning for this constructor.
405 constructImpl(arg1, arg2, std::is_arithmetic<Arg>());
409 for (auto& t : *this) {
412 if (this->isExtern()) {
417 small_vector& operator=(small_vector const& o) {
418 assign(o.begin(), o.end());
422 small_vector& operator=(small_vector&& o) {
423 // TODO: optimization:
424 // if both are internal, use move assignment where possible
425 if (this == &o) return *this;
431 bool operator==(small_vector const& o) const {
432 return size() == o.size() && std::equal(begin(), end(), o.begin());
435 bool operator<(small_vector const& o) const {
436 return std::lexicographical_compare(begin(), end(), o.begin(), o.end());
439 static constexpr size_type max_size() {
440 return !BaseType::kShouldUseHeap ? MaxInline
441 : BaseType::policyMaxSize();
444 size_type size() const { return this->doSize(); }
445 bool empty() const { return !size(); }
447 iterator begin() { return data(); }
448 iterator end() { return data() + size(); }
449 const_iterator begin() const { return data(); }
450 const_iterator end() const { return data() + size(); }
451 const_iterator cbegin() const { return begin(); }
452 const_iterator cend() const { return end(); }
454 reverse_iterator rbegin() { return reverse_iterator(end()); }
455 reverse_iterator rend() { return reverse_iterator(begin()); }
457 const_reverse_iterator rbegin() const {
458 return const_reverse_iterator(end());
461 const_reverse_iterator rend() const {
462 return const_reverse_iterator(begin());
465 const_reverse_iterator crbegin() const { return rbegin(); }
466 const_reverse_iterator crend() const { return rend(); }
469 * Usually one of the simplest functions in a Container-like class
470 * but a bit more complex here. We have to handle all combinations
471 * of in-place vs. heap between this and o.
473 * Basic guarantee only. Provides the nothrow guarantee iff our
474 * value_type has a nothrow move or copy constructor.
476 void swap(small_vector& o) {
477 using std::swap; // Allow ADL on swap for our value_type.
479 if (this->isExtern() && o.isExtern()) {
480 this->swapSizePolicy(o);
482 auto thisCapacity = this->capacity();
483 auto oCapacity = o.capacity();
485 std::swap(unpackHack(&u.pdata_.heap_), unpackHack(&o.u.pdata_.heap_));
487 this->setCapacity(oCapacity);
488 o.setCapacity(thisCapacity);
493 if (!this->isExtern() && !o.isExtern()) {
494 auto& oldSmall = size() < o.size() ? *this : o;
495 auto& oldLarge = size() < o.size() ? o : *this;
497 for (size_type i = 0; i < oldSmall.size(); ++i) {
498 swap(oldSmall[i], oldLarge[i]);
501 size_type i = oldSmall.size();
502 const size_type ci = i;
504 for (; i < oldLarge.size(); ++i) {
505 auto addr = oldSmall.begin() + i;
506 new (addr) value_type(std::move(oldLarge[i]));
507 oldLarge[i].~value_type();
511 for (; i < oldLarge.size(); ++i) {
512 oldLarge[i].~value_type();
514 oldLarge.setSize(ci);
518 oldLarge.setSize(ci);
522 // isExtern != o.isExtern()
523 auto& oldExtern = o.isExtern() ? o : *this;
524 auto& oldIntern = o.isExtern() ? *this : o;
526 auto oldExternCapacity = oldExtern.capacity();
527 auto oldExternHeap = oldExtern.u.pdata_.heap_;
529 auto buff = oldExtern.u.buffer();
532 for (; i < oldIntern.size(); ++i) {
533 new (&buff[i]) value_type(std::move(oldIntern[i]));
534 oldIntern[i].~value_type();
537 for (size_type kill = 0; kill < i; ++kill) {
538 buff[kill].~value_type();
540 for (; i < oldIntern.size(); ++i) {
541 oldIntern[i].~value_type();
543 oldIntern.setSize(0);
544 oldExtern.u.pdata_.heap_ = oldExternHeap;
545 oldExtern.setCapacity(oldExternCapacity);
548 oldIntern.u.pdata_.heap_ = oldExternHeap;
549 this->swapSizePolicy(o);
550 oldIntern.setCapacity(oldExternCapacity);
553 void resize(size_type sz) {
555 erase(begin() + sz, end());
559 detail::populateMemForward(begin() + size(), sz - size(),
560 [&] (void* p) { new (p) value_type(); }
565 void resize(size_type sz, value_type const& v) {
567 erase(begin() + sz, end());
571 detail::populateMemForward(begin() + size(), sz - size(),
572 [&] (void* p) { new (p) value_type(v); }
577 value_type* data() noexcept {
578 return this->isExtern() ? u.heap() : u.buffer();
581 value_type const* data() const noexcept {
582 return this->isExtern() ? u.heap() : u.buffer();
585 template<class ...Args>
586 iterator emplace(const_iterator p, Args&&... args) {
588 emplace_back(std::forward<Args>(args)...);
593 * We implement emplace at places other than at the back with a
594 * temporary for exception safety reasons. It is possible to
595 * avoid having to do this, but it becomes hard to maintain the
596 * basic exception safety guarantee (unless you respond to a copy
597 * constructor throwing by clearing the whole vector).
599 * The reason for this is that otherwise you have to destruct an
600 * element before constructing this one in its place---if the
601 * constructor throws, you either need a nothrow default
602 * constructor or a nothrow copy/move to get something back in the
603 * "gap", and the vector requirements don't guarantee we have any
604 * of these. Clearing the whole vector is a legal response in
605 * this situation, but it seems like this implementation is easy
606 * enough and probably better.
608 return insert(p, value_type(std::forward<Args>(args)...));
611 void reserve(size_type sz) {
615 size_type capacity() const {
616 if (this->isExtern()) {
617 if (u.hasCapacity()) {
618 return *u.getCapacity();
620 return malloc_usable_size(u.pdata_.heap_) / sizeof(value_type);
625 void shrink_to_fit() {
626 if (!this->isExtern()) {
630 small_vector tmp(begin(), end());
634 template<class ...Args>
635 void emplace_back(Args&&... args) {
636 // call helper function for static dispatch of special cases
637 emplaceBack(std::forward<Args>(args)...);
640 void emplace_back(const value_type& t) {
643 void emplace_back(value_type& t) {
647 void emplace_back(value_type&& t) {
648 push_back(std::move(t));
651 void push_back(value_type&& t) {
652 if (capacity() == size()) {
653 makeSize(std::max(size_type(2), 3 * size() / 2), &t, size());
655 new (end()) value_type(std::move(t));
657 this->setSize(size() + 1);
660 void push_back(value_type const& t) {
661 // TODO: we'd like to make use of makeSize (it can be optimized better,
662 // because it manipulates the internals)
663 // unfortunately the current implementation only supports moving from
664 // a supplied rvalue, and doing an extra move just to reuse it is a perf
666 if (size() == capacity()) {// && isInside(&t)) {
668 emplaceBack(std::move(tmp));
678 iterator insert(const_iterator constp, value_type&& t) {
679 iterator p = unconst(constp);
682 push_back(std::move(t));
686 auto offset = p - begin();
688 if (capacity() == size()) {
689 makeSize(size() + 1, &t, offset);
690 this->setSize(this->size() + 1);
692 makeSize(size() + 1);
693 detail::moveObjectsRight(data() + offset,
695 data() + size() + 1);
696 this->setSize(size() + 1);
697 data()[offset] = std::move(t);
699 return begin() + offset;
703 iterator insert(const_iterator p, value_type const& t) {
704 // Make a copy and forward to the rvalue value_type&& overload
706 return insert(p, value_type(t));
709 iterator insert(const_iterator pos, size_type n, value_type const& val) {
710 auto offset = pos - begin();
711 makeSize(size() + n);
712 detail::moveObjectsRight(data() + offset,
714 data() + size() + n);
715 this->setSize(size() + n);
716 std::generate_n(begin() + offset, n, [&] { return val; });
717 return begin() + offset;
721 iterator insert(const_iterator p, Arg arg1, Arg arg2) {
722 // Forward using std::is_arithmetic to get to the proper
723 // implementation; this disambiguates between the iterators and
724 // (size_t, value_type) meaning for this function.
725 return insertImpl(unconst(p), arg1, arg2, std::is_arithmetic<Arg>());
728 iterator insert(const_iterator p, std::initializer_list<value_type> il) {
729 return insert(p, il.begin(), il.end());
732 iterator erase(const_iterator q) {
733 std::move(unconst(q) + 1, end(), unconst(q));
734 (data() + size() - 1)->~value_type();
735 this->setSize(size() - 1);
739 iterator erase(const_iterator q1, const_iterator q2) {
740 if (q1 == q2) return unconst(q1);
741 std::move(unconst(q2), end(), unconst(q1));
742 for (auto it = (end() - std::distance(q1, q2)); it != end(); ++it) {
745 this->setSize(size() - (q2 - q1));
750 erase(begin(), end());
754 void assign(Arg first, Arg last) {
756 insert(end(), first, last);
759 void assign(std::initializer_list<value_type> il) {
760 assign(il.begin(), il.end());
763 void assign(size_type n, const value_type& t) {
768 reference front() { assert(!empty()); return *begin(); }
769 reference back() { assert(!empty()); return *(end() - 1); }
770 const_reference front() const { assert(!empty()); return *begin(); }
771 const_reference back() const { assert(!empty()); return *(end() - 1); }
773 reference operator[](size_type i) {
775 return *(begin() + i);
778 const_reference operator[](size_type i) const {
780 return *(begin() + i);
783 reference at(size_type i) {
785 throw std::out_of_range("index out of range");
790 const_reference at(size_type i) const {
792 throw std::out_of_range("index out of range");
800 * This is doing the same like emplace_back, but we need this helper
801 * to catch the special case - see the next overload function..
803 template<class ...Args>
804 void emplaceBack(Args&&... args) {
805 makeSize(size() + 1);
806 new (end()) value_type(std::forward<Args>(args)...);
807 this->setSize(size() + 1);
810 static iterator unconst(const_iterator it) {
811 return const_cast<iterator>(it);
815 * g++ doesn't allow you to bind a non-const reference to a member
816 * of a packed structure, presumably because it would make it too
817 * easy to accidentally make an unaligned memory access?
819 template<class T> static T& unpackHack(T* p) {
823 // The std::false_type argument is part of disambiguating the
824 // iterator insert functions from integral types (see insert().)
826 iterator insertImpl(iterator pos, It first, It last, std::false_type) {
827 typedef typename std::iterator_traits<It>::iterator_category categ;
828 if (std::is_same<categ,std::input_iterator_tag>::value) {
829 auto offset = pos - begin();
830 while (first != last) {
831 pos = insert(pos, *first++);
834 return begin() + offset;
837 auto distance = std::distance(first, last);
838 auto offset = pos - begin();
839 makeSize(size() + distance);
840 detail::moveObjectsRight(data() + offset,
842 data() + size() + distance);
843 this->setSize(size() + distance);
844 std::copy_n(first, distance, begin() + offset);
845 return begin() + offset;
848 iterator insertImpl(iterator pos, size_type n, const value_type& val,
850 // The true_type means this should call the size_t,value_type
851 // overload. (See insert().)
852 return insert(pos, n, val);
855 // The std::false_type argument came from std::is_arithmetic as part
856 // of disambiguating an overload (see the comment in the
859 void constructImpl(It first, It last, std::false_type) {
860 typedef typename std::iterator_traits<It>::iterator_category categ;
861 if (std::is_same<categ,std::input_iterator_tag>::value) {
862 // With iterators that only allow a single pass, we can't really
863 // do anything sane here.
864 while (first != last) {
865 emplace_back(*first++);
870 auto distance = std::distance(first, last);
872 this->setSize(distance);
874 detail::populateMemForward(data(), distance,
875 [&] (void* p) { new (p) value_type(*first++); }
878 if (this->isExtern()) {
885 void doConstruct(size_type n, value_type const& val) {
889 detail::populateMemForward(data(), n,
890 [&] (void* p) { new (p) value_type(val); }
893 if (this->isExtern()) {
900 // The true_type means we should forward to the size_t,value_type
902 void constructImpl(size_type n, value_type const& val, std::true_type) {
906 void makeSize(size_type size, value_type* v = nullptr) {
907 makeSize(size, v, size - 1);
911 * Ensure we have a large enough memory region to be size `size'.
912 * Will move/copy elements if we are spilling to heap_ or needed to
913 * allocate a new region, but if resized in place doesn't initialize
914 * anything in the new region. In any case doesn't change size().
915 * Supports insertion of new element during reallocation by given
916 * pointer to new element and position of new element.
917 * NOTE: If reallocation is not needed, and new element should be
918 * inserted in the middle of vector (not at the end), do the move
919 * objects and insertion outside the function, otherwise exception is thrown.
921 void makeSize(size_type size, value_type* v, size_type pos) {
922 if (size > this->max_size()) {
923 throw std::length_error("max_size exceeded in small_vector");
925 if (size <= this->capacity()) {
929 auto needBytes = size * sizeof(value_type);
930 // If the capacity isn't explicitly stored inline, but the heap
931 // allocation is grown to over some threshold, we should store
932 // a capacity at the front of the heap allocation.
933 bool heapifyCapacity =
934 !kHasInlineCapacity && needBytes > kHeapifyCapacityThreshold;
935 if (heapifyCapacity) {
936 needBytes += kHeapifyCapacitySize;
938 auto const sizeBytes = goodMallocSize(needBytes);
939 void* newh = checkedMalloc(sizeBytes);
940 // We expect newh to be at least 2-aligned, because we want to
941 // use its least significant bit as a flag.
942 assert(!detail::pointerFlagGet(newh));
944 value_type* newp = static_cast<value_type*>(
946 detail::shiftPointer(newh, kHeapifyCapacitySize) :
952 new (&newp[pos]) value_type(std::move(*v));
958 // move old elements to the left of the new one
960 detail::moveToUninitialized(begin(), begin() + pos, newp);
962 newp[pos].~value_type();
967 // move old elements to the right of the new one
970 detail::moveToUninitialized(begin() + pos, end(), newp + pos + 1);
973 for (size_type i = 0; i <= pos; ++i) {
974 newp[i].~value_type();
980 // move without inserting new element
982 detail::moveToUninitialized(begin(), end(), newp);
988 for (auto& val : *this) {
992 if (this->isExtern()) {
995 auto availableSizeBytes = sizeBytes;
996 if (heapifyCapacity) {
997 u.pdata_.heap_ = detail::pointerFlagSet(newh);
998 availableSizeBytes -= kHeapifyCapacitySize;
1000 u.pdata_.heap_ = newh;
1002 this->setExtern(true);
1003 this->setCapacity(availableSizeBytes / sizeof(value_type));
1007 * This will set the capacity field, stored inline in the storage_ field
1008 * if there is sufficient room to store it.
1010 void setCapacity(size_type newCapacity) {
1011 assert(this->isExtern());
1012 if (u.hasCapacity()) {
1013 assert(newCapacity < std::numeric_limits<InternalSizeType>::max());
1014 *u.getCapacity() = InternalSizeType(newCapacity);
1019 struct HeapPtrWithCapacity {
1021 InternalSizeType capacity_;
1023 InternalSizeType* getCapacity() {
1029 // Lower order bit of heap_ is used as flag to indicate whether capacity is
1030 // stored at the front of the heap allocation.
1033 InternalSizeType* getCapacity() {
1034 assert(detail::pointerFlagGet(heap_));
1035 return static_cast<InternalSizeType*>(
1036 detail::pointerFlagClear(heap_));
1040 #if (FOLLY_X64 || FOLLY_PPC64)
1041 typedef unsigned char InlineStorageDataType[sizeof(value_type) * MaxInline];
1043 typedef typename std::aligned_storage<
1044 sizeof(value_type) * MaxInline,
1046 >::type InlineStorageDataType;
1049 typedef typename std::conditional<
1050 sizeof(value_type) * MaxInline != 0,
1051 InlineStorageDataType,
1053 >::type InlineStorageType;
1055 static bool const kHasInlineCapacity =
1056 sizeof(HeapPtrWithCapacity) < sizeof(InlineStorageType);
1058 // This value should we multiple of word size.
1059 static size_t const kHeapifyCapacitySize = sizeof(
1060 typename std::aligned_storage<
1061 sizeof(InternalSizeType),
1064 // Threshold to control capacity heapifying.
1065 static size_t const kHeapifyCapacityThreshold =
1066 100 * kHeapifyCapacitySize;
1068 typedef typename std::conditional<
1070 HeapPtrWithCapacity,
1072 >::type PointerType;
1075 explicit Data() { pdata_.heap_ = 0; }
1078 InlineStorageType storage_;
1080 value_type* buffer() noexcept {
1081 void* vp = &storage_;
1082 return static_cast<value_type*>(vp);
1084 value_type const* buffer() const noexcept {
1085 return const_cast<Data*>(this)->buffer();
1087 value_type* heap() noexcept {
1088 if (kHasInlineCapacity || !detail::pointerFlagGet(pdata_.heap_)) {
1089 return static_cast<value_type*>(pdata_.heap_);
1091 return static_cast<value_type*>(
1092 detail::shiftPointer(
1093 detail::pointerFlagClear(pdata_.heap_), kHeapifyCapacitySize));
1095 value_type const* heap() const noexcept {
1096 return const_cast<Data*>(this)->heap();
1099 bool hasCapacity() const {
1100 return kHasInlineCapacity || detail::pointerFlagGet(pdata_.heap_);
1102 InternalSizeType* getCapacity() {
1103 return pdata_.getCapacity();
1105 InternalSizeType* getCapacity() const {
1106 return const_cast<Data*>(this)->getCapacity();
1110 auto vp = detail::pointerFlagClear(pdata_.heap_);
1113 } FOLLY_PACK_ATTR u;
1117 //////////////////////////////////////////////////////////////////////
1119 // Basic guarantee only, or provides the nothrow guarantee iff T has a
1120 // nothrow move or copy constructor.
1121 template<class T, std::size_t MaxInline, class A, class B, class C>
1122 void swap(small_vector<T,MaxInline,A,B,C>& a,
1123 small_vector<T,MaxInline,A,B,C>& b) {
1127 //////////////////////////////////////////////////////////////////////
1132 template <class T, size_t M, class A, class B, class C>
1133 struct IndexableTraits<small_vector<T, M, A, B, C>>
1134 : public IndexableTraitsSeq<small_vector<T, M, A, B, C>> {
1137 } // namespace detail
1139 } // namespace folly
1141 #pragma GCC diagnostic pop