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/portability/Constexpr.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.)
359 constexpr_max(sizeof(Value*) / sizeof(Value), RequestedMaxInline),
363 typedef std::size_t size_type;
364 typedef Value value_type;
365 typedef value_type& reference;
366 typedef value_type const& const_reference;
367 typedef value_type* iterator;
368 typedef value_type const* const_iterator;
369 typedef std::ptrdiff_t difference_type;
371 typedef std::reverse_iterator<iterator> reverse_iterator;
372 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
374 explicit small_vector() = default;
376 small_vector(small_vector const& o) {
380 std::uninitialized_copy(o.begin(), o.end(), begin());
382 if (this->isExtern()) {
390 small_vector(small_vector&& o)
391 noexcept(std::is_nothrow_move_constructible<Value>::value) {
395 std::uninitialized_copy(std::make_move_iterator(o.begin()),
396 std::make_move_iterator(o.end()),
398 this->setSize(o.size());
402 small_vector(std::initializer_list<value_type> il) {
403 constructImpl(il.begin(), il.end(), std::false_type());
406 explicit small_vector(size_type n, value_type const& t = value_type()) {
411 explicit small_vector(Arg arg1, Arg arg2) {
412 // Forward using std::is_arithmetic to get to the proper
413 // implementation; this disambiguates between the iterators and
414 // (size_t, value_type) meaning for this constructor.
415 constructImpl(arg1, arg2, std::is_arithmetic<Arg>());
419 for (auto& t : *this) {
422 if (this->isExtern()) {
427 small_vector& operator=(small_vector const& o) {
428 assign(o.begin(), o.end());
432 small_vector& operator=(small_vector&& o) {
433 // TODO: optimization:
434 // if both are internal, use move assignment where possible
435 if (this == &o) return *this;
441 bool operator==(small_vector const& o) const {
442 return size() == o.size() && std::equal(begin(), end(), o.begin());
445 bool operator<(small_vector const& o) const {
446 return std::lexicographical_compare(begin(), end(), o.begin(), o.end());
449 static constexpr size_type max_size() {
450 return !BaseType::kShouldUseHeap ? MaxInline
451 : BaseType::policyMaxSize();
454 size_type size() const { return this->doSize(); }
455 bool empty() const { return !size(); }
457 iterator begin() { return data(); }
458 iterator end() { return data() + size(); }
459 const_iterator begin() const { return data(); }
460 const_iterator end() const { return data() + size(); }
461 const_iterator cbegin() const { return begin(); }
462 const_iterator cend() const { return end(); }
464 reverse_iterator rbegin() { return reverse_iterator(end()); }
465 reverse_iterator rend() { return reverse_iterator(begin()); }
467 const_reverse_iterator rbegin() const {
468 return const_reverse_iterator(end());
471 const_reverse_iterator rend() const {
472 return const_reverse_iterator(begin());
475 const_reverse_iterator crbegin() const { return rbegin(); }
476 const_reverse_iterator crend() const { return rend(); }
479 * Usually one of the simplest functions in a Container-like class
480 * but a bit more complex here. We have to handle all combinations
481 * of in-place vs. heap between this and o.
483 * Basic guarantee only. Provides the nothrow guarantee iff our
484 * value_type has a nothrow move or copy constructor.
486 void swap(small_vector& o) {
487 using std::swap; // Allow ADL on swap for our value_type.
489 if (this->isExtern() && o.isExtern()) {
490 this->swapSizePolicy(o);
492 auto thisCapacity = this->capacity();
493 auto oCapacity = o.capacity();
495 std::swap(unpackHack(&u.pdata_.heap_), unpackHack(&o.u.pdata_.heap_));
497 this->setCapacity(oCapacity);
498 o.setCapacity(thisCapacity);
503 if (!this->isExtern() && !o.isExtern()) {
504 auto& oldSmall = size() < o.size() ? *this : o;
505 auto& oldLarge = size() < o.size() ? o : *this;
507 for (size_type i = 0; i < oldSmall.size(); ++i) {
508 swap(oldSmall[i], oldLarge[i]);
511 size_type i = oldSmall.size();
512 const size_type ci = i;
514 for (; i < oldLarge.size(); ++i) {
515 auto addr = oldSmall.begin() + i;
516 new (addr) value_type(std::move(oldLarge[i]));
517 oldLarge[i].~value_type();
521 for (; i < oldLarge.size(); ++i) {
522 oldLarge[i].~value_type();
524 oldLarge.setSize(ci);
528 oldLarge.setSize(ci);
532 // isExtern != o.isExtern()
533 auto& oldExtern = o.isExtern() ? o : *this;
534 auto& oldIntern = o.isExtern() ? *this : o;
536 auto oldExternCapacity = oldExtern.capacity();
537 auto oldExternHeap = oldExtern.u.pdata_.heap_;
539 auto buff = oldExtern.u.buffer();
542 for (; i < oldIntern.size(); ++i) {
543 new (&buff[i]) value_type(std::move(oldIntern[i]));
544 oldIntern[i].~value_type();
547 for (size_type kill = 0; kill < i; ++kill) {
548 buff[kill].~value_type();
550 for (; i < oldIntern.size(); ++i) {
551 oldIntern[i].~value_type();
553 oldIntern.setSize(0);
554 oldExtern.u.pdata_.heap_ = oldExternHeap;
555 oldExtern.setCapacity(oldExternCapacity);
558 oldIntern.u.pdata_.heap_ = oldExternHeap;
559 this->swapSizePolicy(o);
560 oldIntern.setCapacity(oldExternCapacity);
563 void resize(size_type sz) {
565 erase(begin() + sz, end());
569 detail::populateMemForward(begin() + size(), sz - size(),
570 [&] (void* p) { new (p) value_type(); }
575 void resize(size_type sz, value_type const& v) {
577 erase(begin() + sz, end());
581 detail::populateMemForward(begin() + size(), sz - size(),
582 [&] (void* p) { new (p) value_type(v); }
587 value_type* data() noexcept {
588 return this->isExtern() ? u.heap() : u.buffer();
591 value_type const* data() const noexcept {
592 return this->isExtern() ? u.heap() : u.buffer();
595 template<class ...Args>
596 iterator emplace(const_iterator p, Args&&... args) {
598 emplace_back(std::forward<Args>(args)...);
603 * We implement emplace at places other than at the back with a
604 * temporary for exception safety reasons. It is possible to
605 * avoid having to do this, but it becomes hard to maintain the
606 * basic exception safety guarantee (unless you respond to a copy
607 * constructor throwing by clearing the whole vector).
609 * The reason for this is that otherwise you have to destruct an
610 * element before constructing this one in its place---if the
611 * constructor throws, you either need a nothrow default
612 * constructor or a nothrow copy/move to get something back in the
613 * "gap", and the vector requirements don't guarantee we have any
614 * of these. Clearing the whole vector is a legal response in
615 * this situation, but it seems like this implementation is easy
616 * enough and probably better.
618 return insert(p, value_type(std::forward<Args>(args)...));
621 void reserve(size_type sz) {
625 size_type capacity() const {
626 if (this->isExtern()) {
627 if (u.hasCapacity()) {
628 return *u.getCapacity();
630 return malloc_usable_size(u.pdata_.heap_) / sizeof(value_type);
635 void shrink_to_fit() {
636 if (!this->isExtern()) {
640 small_vector tmp(begin(), end());
644 template<class ...Args>
645 void emplace_back(Args&&... args) {
646 // call helper function for static dispatch of special cases
647 emplaceBack(std::forward<Args>(args)...);
650 void emplace_back(const value_type& t) {
653 void emplace_back(value_type& t) {
657 void emplace_back(value_type&& t) {
658 push_back(std::move(t));
661 void push_back(value_type&& t) {
662 if (capacity() == size()) {
663 makeSize(std::max(size_type(2), 3 * size() / 2), &t, size());
665 new (end()) value_type(std::move(t));
667 this->setSize(size() + 1);
670 void push_back(value_type const& t) {
671 // TODO: we'd like to make use of makeSize (it can be optimized better,
672 // because it manipulates the internals)
673 // unfortunately the current implementation only supports moving from
674 // a supplied rvalue, and doing an extra move just to reuse it is a perf
676 if (size() == capacity()) {// && isInside(&t)) {
678 emplaceBack(std::move(tmp));
688 iterator insert(const_iterator constp, value_type&& t) {
689 iterator p = unconst(constp);
692 push_back(std::move(t));
696 auto offset = p - begin();
698 if (capacity() == size()) {
699 makeSize(size() + 1, &t, offset);
700 this->setSize(this->size() + 1);
702 makeSize(size() + 1);
703 detail::moveObjectsRight(data() + offset,
705 data() + size() + 1);
706 this->setSize(size() + 1);
707 data()[offset] = std::move(t);
709 return begin() + offset;
713 iterator insert(const_iterator p, value_type const& t) {
714 // Make a copy and forward to the rvalue value_type&& overload
716 return insert(p, value_type(t));
719 iterator insert(const_iterator pos, size_type n, value_type const& val) {
720 auto offset = pos - begin();
721 makeSize(size() + n);
722 detail::moveObjectsRight(data() + offset,
724 data() + size() + n);
725 this->setSize(size() + n);
726 std::generate_n(begin() + offset, n, [&] { return val; });
727 return begin() + offset;
731 iterator insert(const_iterator p, Arg arg1, Arg arg2) {
732 // Forward using std::is_arithmetic to get to the proper
733 // implementation; this disambiguates between the iterators and
734 // (size_t, value_type) meaning for this function.
735 return insertImpl(unconst(p), arg1, arg2, std::is_arithmetic<Arg>());
738 iterator insert(const_iterator p, std::initializer_list<value_type> il) {
739 return insert(p, il.begin(), il.end());
742 iterator erase(const_iterator q) {
743 std::move(unconst(q) + 1, end(), unconst(q));
744 (data() + size() - 1)->~value_type();
745 this->setSize(size() - 1);
749 iterator erase(const_iterator q1, const_iterator q2) {
750 if (q1 == q2) return unconst(q1);
751 std::move(unconst(q2), end(), unconst(q1));
752 for (auto it = (end() - std::distance(q1, q2)); it != end(); ++it) {
755 this->setSize(size() - (q2 - q1));
760 erase(begin(), end());
764 void assign(Arg first, Arg last) {
766 insert(end(), first, last);
769 void assign(std::initializer_list<value_type> il) {
770 assign(il.begin(), il.end());
773 void assign(size_type n, const value_type& t) {
778 reference front() { assert(!empty()); return *begin(); }
779 reference back() { assert(!empty()); return *(end() - 1); }
780 const_reference front() const { assert(!empty()); return *begin(); }
781 const_reference back() const { assert(!empty()); return *(end() - 1); }
783 reference operator[](size_type i) {
785 return *(begin() + i);
788 const_reference operator[](size_type i) const {
790 return *(begin() + i);
793 reference at(size_type i) {
795 throw std::out_of_range("index out of range");
800 const_reference at(size_type i) const {
802 throw std::out_of_range("index out of range");
810 * This is doing the same like emplace_back, but we need this helper
811 * to catch the special case - see the next overload function..
813 template<class ...Args>
814 void emplaceBack(Args&&... args) {
815 makeSize(size() + 1);
816 new (end()) value_type(std::forward<Args>(args)...);
817 this->setSize(size() + 1);
820 static iterator unconst(const_iterator it) {
821 return const_cast<iterator>(it);
825 * g++ doesn't allow you to bind a non-const reference to a member
826 * of a packed structure, presumably because it would make it too
827 * easy to accidentally make an unaligned memory access?
829 template<class T> static T& unpackHack(T* p) {
833 // The std::false_type argument is part of disambiguating the
834 // iterator insert functions from integral types (see insert().)
836 iterator insertImpl(iterator pos, It first, It last, std::false_type) {
837 typedef typename std::iterator_traits<It>::iterator_category categ;
838 if (std::is_same<categ,std::input_iterator_tag>::value) {
839 auto offset = pos - begin();
840 while (first != last) {
841 pos = insert(pos, *first++);
844 return begin() + offset;
847 auto distance = std::distance(first, last);
848 auto offset = pos - begin();
849 makeSize(size() + distance);
850 detail::moveObjectsRight(data() + offset,
852 data() + size() + distance);
853 this->setSize(size() + distance);
854 std::copy_n(first, distance, begin() + offset);
855 return begin() + offset;
858 iterator insertImpl(iterator pos, size_type n, const value_type& val,
860 // The true_type means this should call the size_t,value_type
861 // overload. (See insert().)
862 return insert(pos, n, val);
865 // The std::false_type argument came from std::is_arithmetic as part
866 // of disambiguating an overload (see the comment in the
869 void constructImpl(It first, It last, std::false_type) {
870 typedef typename std::iterator_traits<It>::iterator_category categ;
871 if (std::is_same<categ,std::input_iterator_tag>::value) {
872 // With iterators that only allow a single pass, we can't really
873 // do anything sane here.
874 while (first != last) {
875 emplace_back(*first++);
880 auto distance = std::distance(first, last);
882 this->setSize(distance);
884 detail::populateMemForward(data(), distance,
885 [&] (void* p) { new (p) value_type(*first++); }
888 if (this->isExtern()) {
895 void doConstruct(size_type n, value_type const& val) {
899 detail::populateMemForward(data(), n,
900 [&] (void* p) { new (p) value_type(val); }
903 if (this->isExtern()) {
910 // The true_type means we should forward to the size_t,value_type
912 void constructImpl(size_type n, value_type const& val, std::true_type) {
916 void makeSize(size_type size, value_type* v = nullptr) {
917 makeSize(size, v, size - 1);
921 * Ensure we have a large enough memory region to be size `size'.
922 * Will move/copy elements if we are spilling to heap_ or needed to
923 * allocate a new region, but if resized in place doesn't initialize
924 * anything in the new region. In any case doesn't change size().
925 * Supports insertion of new element during reallocation by given
926 * pointer to new element and position of new element.
927 * NOTE: If reallocation is not needed, and new element should be
928 * inserted in the middle of vector (not at the end), do the move
929 * objects and insertion outside the function, otherwise exception is thrown.
931 void makeSize(size_type size, value_type* v, size_type pos) {
932 if (size > this->max_size()) {
933 throw std::length_error("max_size exceeded in small_vector");
935 if (size <= this->capacity()) {
939 auto needBytes = size * sizeof(value_type);
940 // If the capacity isn't explicitly stored inline, but the heap
941 // allocation is grown to over some threshold, we should store
942 // a capacity at the front of the heap allocation.
943 bool heapifyCapacity =
944 !kHasInlineCapacity && needBytes > kHeapifyCapacityThreshold;
945 if (heapifyCapacity) {
946 needBytes += kHeapifyCapacitySize;
948 auto const sizeBytes = goodMallocSize(needBytes);
949 void* newh = checkedMalloc(sizeBytes);
950 // We expect newh to be at least 2-aligned, because we want to
951 // use its least significant bit as a flag.
952 assert(!detail::pointerFlagGet(newh));
954 value_type* newp = static_cast<value_type*>(
956 detail::shiftPointer(newh, kHeapifyCapacitySize) :
962 new (&newp[pos]) value_type(std::move(*v));
968 // move old elements to the left of the new one
970 detail::moveToUninitialized(begin(), begin() + pos, newp);
972 newp[pos].~value_type();
977 // move old elements to the right of the new one
980 detail::moveToUninitialized(begin() + pos, end(), newp + pos + 1);
983 for (size_type i = 0; i <= pos; ++i) {
984 newp[i].~value_type();
990 // move without inserting new element
992 detail::moveToUninitialized(begin(), end(), newp);
998 for (auto& val : *this) {
1002 if (this->isExtern()) {
1005 auto availableSizeBytes = sizeBytes;
1006 if (heapifyCapacity) {
1007 u.pdata_.heap_ = detail::pointerFlagSet(newh);
1008 availableSizeBytes -= kHeapifyCapacitySize;
1010 u.pdata_.heap_ = newh;
1012 this->setExtern(true);
1013 this->setCapacity(availableSizeBytes / sizeof(value_type));
1017 * This will set the capacity field, stored inline in the storage_ field
1018 * if there is sufficient room to store it.
1020 void setCapacity(size_type newCapacity) {
1021 assert(this->isExtern());
1022 if (u.hasCapacity()) {
1023 assert(newCapacity < std::numeric_limits<InternalSizeType>::max());
1024 *u.getCapacity() = InternalSizeType(newCapacity);
1029 struct HeapPtrWithCapacity {
1031 InternalSizeType capacity_;
1033 InternalSizeType* getCapacity() {
1039 // Lower order bit of heap_ is used as flag to indicate whether capacity is
1040 // stored at the front of the heap allocation.
1043 InternalSizeType* getCapacity() {
1044 assert(detail::pointerFlagGet(heap_));
1045 return static_cast<InternalSizeType*>(
1046 detail::pointerFlagClear(heap_));
1050 #if (FOLLY_X64 || FOLLY_PPC64)
1051 typedef unsigned char InlineStorageType[sizeof(value_type) * MaxInline];
1053 typedef typename std::aligned_storage<
1054 sizeof(value_type) * MaxInline,
1056 >::type InlineStorageType;
1059 static bool const kHasInlineCapacity =
1060 sizeof(HeapPtrWithCapacity) < sizeof(InlineStorageType);
1062 // This value should we multiple of word size.
1063 static size_t const kHeapifyCapacitySize = sizeof(
1064 typename std::aligned_storage<
1065 sizeof(InternalSizeType),
1068 // Threshold to control capacity heapifying.
1069 static size_t const kHeapifyCapacityThreshold =
1070 100 * kHeapifyCapacitySize;
1072 typedef typename std::conditional<
1074 HeapPtrWithCapacity,
1076 >::type PointerType;
1079 explicit Data() { pdata_.heap_ = 0; }
1082 InlineStorageType storage_;
1084 value_type* buffer() noexcept {
1085 void* vp = &storage_;
1086 return static_cast<value_type*>(vp);
1088 value_type const* buffer() const noexcept {
1089 return const_cast<Data*>(this)->buffer();
1091 value_type* heap() noexcept {
1092 if (kHasInlineCapacity || !detail::pointerFlagGet(pdata_.heap_)) {
1093 return static_cast<value_type*>(pdata_.heap_);
1095 return static_cast<value_type*>(
1096 detail::shiftPointer(
1097 detail::pointerFlagClear(pdata_.heap_), kHeapifyCapacitySize));
1099 value_type const* heap() const noexcept {
1100 return const_cast<Data*>(this)->heap();
1103 bool hasCapacity() const {
1104 return kHasInlineCapacity || detail::pointerFlagGet(pdata_.heap_);
1106 InternalSizeType* getCapacity() {
1107 return pdata_.getCapacity();
1109 InternalSizeType* getCapacity() const {
1110 return const_cast<Data*>(this)->getCapacity();
1114 auto vp = detail::pointerFlagClear(pdata_.heap_);
1121 //////////////////////////////////////////////////////////////////////
1123 // Basic guarantee only, or provides the nothrow guarantee iff T has a
1124 // nothrow move or copy constructor.
1125 template<class T, std::size_t MaxInline, class A, class B, class C>
1126 void swap(small_vector<T,MaxInline,A,B,C>& a,
1127 small_vector<T,MaxInline,A,B,C>& b) {
1131 //////////////////////////////////////////////////////////////////////
1136 template <class T, size_t M, class A, class B, class C>
1137 struct IndexableTraits<small_vector<T, M, A, B, C>>
1138 : public IndexableTraitsSeq<small_vector<T, M, A, B, C>> {
1141 } // namespace detail
1143 } // namespace folly
1145 #pragma GCC diagnostic pop
1148 # undef FB_PACK_ATTR
1149 # undef FB_PACK_PUSH