2 * Copyright 2014 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>
23 #ifndef FOLLY_SMALL_VECTOR_H_
24 #define FOLLY_SMALL_VECTOR_H_
26 #include "Portability.h"
30 #include <type_traits>
35 #include <boost/operators.hpp>
36 #include <boost/type_traits.hpp>
37 #include <boost/mpl/if.hpp>
38 #include <boost/mpl/eval_if.hpp>
39 #include <boost/mpl/vector.hpp>
40 #include <boost/mpl/front.hpp>
41 #include <boost/mpl/filter_view.hpp>
42 #include <boost/mpl/identity.hpp>
43 #include <boost/mpl/placeholders.hpp>
44 #include <boost/mpl/empty.hpp>
45 #include <boost/mpl/size.hpp>
46 #include <boost/mpl/count.hpp>
47 #include <boost/mpl/max.hpp>
49 #include "folly/Malloc.h"
51 #if defined(__GNUC__) && FOLLY_X64
52 # include "folly/SmallLocks.h"
53 # define FB_PACK_ATTR FOLLY_PACK_ATTR
54 # define FB_PACK_PUSH FOLLY_PACK_PUSH
55 # define FB_PACK_POP FOLLY_PACK_POP
62 #if FOLLY_HAVE_MALLOC_SIZE
63 extern "C" std::size_t malloc_size(const void*);
64 # if !FOLLY_HAVE_MALLOC_USABLE_SIZE
65 # define malloc_usable_size malloc_size
67 # ifndef malloc_usable_size
68 # define malloc_usable_size malloc_size
72 // Ignore shadowing warnings within this file, so includers can use -Wshadow.
73 #pragma GCC diagnostic push
74 #pragma GCC diagnostic ignored "-Wshadow"
78 //////////////////////////////////////////////////////////////////////
80 namespace small_vector_policy {
82 //////////////////////////////////////////////////////////////////////
85 * A flag which makes us refuse to use the heap at all. If we
86 * overflow the in situ capacity we throw an exception.
91 * Passing this policy will cause small_vector to provide lock() and
92 * unlock() functions using a 1-bit spin lock in the size value.
94 * Note that this is intended for a fairly specialized (although
95 * strangely common at facebook) use case, where you have billions of
96 * vectors in memory where none of them are "hot" and most of them are
97 * small. This allows you to get fine-grained locks without spending
98 * a lot of memory on mutexes (the alternative of a large hashtable of
99 * locks leads to extra cache misses in the lookup path).
105 //////////////////////////////////////////////////////////////////////
107 } // small_vector_policy
109 //////////////////////////////////////////////////////////////////////
111 template<class T, std::size_t M, class A, class B, class C>
114 //////////////////////////////////////////////////////////////////////
119 * Move a range to a range of uninitialized memory. Assumes the
120 * ranges don't overlap.
123 typename std::enable_if<
124 !FOLLY_IS_TRIVIALLY_COPYABLE(T)
126 moveToUninitialized(T* first, T* last, T* out) {
127 auto const count = last - first;
130 for (; idx < count; ++first, ++idx) {
131 new (&out[idx]) T(std::move(*first));
134 // Even for callers trying to give the strong guarantee
135 // (e.g. push_back) it's ok to assume here that we don't have to
136 // move things back and that it was a copy constructor that
137 // threw: if someone throws from a move constructor the effects
139 for (std::size_t i = 0; i < idx; ++i) {
146 // Specialization for trivially copyable types.
148 typename std::enable_if<
149 FOLLY_IS_TRIVIALLY_COPYABLE(T)
151 moveToUninitialized(T* first, T* last, T* out) {
152 std::memmove(out, first, (last - first) * sizeof *first);
156 * Move objects in memory to the right into some uninitialized
157 * memory, where the region overlaps. This doesn't just use
158 * std::move_backward because move_backward only works if all the
159 * memory is initialized to type T already.
162 typename std::enable_if<
163 !FOLLY_IS_TRIVIALLY_COPYABLE(T)
165 moveObjectsRight(T* first, T* lastConstructed, T* realLast) {
166 if (lastConstructed == realLast) {
170 T* end = first - 1; // Past the end going backwards.
171 T* out = realLast - 1;
172 T* in = lastConstructed - 1;
174 for (; in != end && out >= lastConstructed; --in, --out) {
175 new (out) T(std::move(*in));
177 for (; in != end; --in, --out) {
178 *out = std::move(*in);
180 for (; out >= lastConstructed; --out) {
184 // We want to make sure the same stuff is uninitialized memory
185 // if we exit via an exception (this is to make sure we provide
186 // the basic exception safety guarantee for insert functions).
187 if (out < lastConstructed) {
188 out = lastConstructed - 1;
190 for (auto it = out + 1; it != realLast; ++it) {
197 // Specialization for trivially copyable types. The call to
198 // std::move_backward here will just turn into a memmove. (TODO:
199 // change to std::is_trivially_copyable when that works.)
201 typename std::enable_if<
202 FOLLY_IS_TRIVIALLY_COPYABLE(T)
204 moveObjectsRight(T* first, T* lastConstructed, T* realLast) {
205 std::move_backward(first, lastConstructed, realLast);
209 * Populate a region of memory using `op' to construct elements. If
210 * anything throws, undo what we did.
212 template<class T, class Function>
213 void populateMemForward(T* mem, std::size_t n, Function const& op) {
216 for (size_t i = 0; i < n; ++i) {
221 for (std::size_t i = 0; i < idx; ++i) {
228 template<class SizeType, bool ShouldUseHeap>
229 struct IntegralSizePolicy {
230 typedef SizeType InternalSizeType;
232 IntegralSizePolicy() : size_(0) {}
235 static constexpr std::size_t policyMaxSize() {
236 return SizeType(~kExternMask);
239 std::size_t doSize() const {
240 return size_ & ~kExternMask;
243 std::size_t isExtern() const {
244 return kExternMask & size_;
247 void setExtern(bool b) {
249 size_ |= kExternMask;
251 size_ &= ~kExternMask;
255 void setSize(std::size_t sz) {
256 assert(sz <= policyMaxSize());
257 size_ = (kExternMask & size_) | SizeType(sz);
260 void swapSizePolicy(IntegralSizePolicy& o) {
261 std::swap(size_, o.size_);
265 static bool const kShouldUseHeap = ShouldUseHeap;
268 static SizeType const kExternMask =
269 kShouldUseHeap ? SizeType(1) << (sizeof(SizeType) * 8 - 1)
276 template<class SizeType, bool ShouldUseHeap>
277 struct OneBitMutexImpl {
278 typedef SizeType InternalSizeType;
280 OneBitMutexImpl() { psl_.init(); }
282 void lock() const { psl_.lock(); }
283 void unlock() const { psl_.unlock(); }
284 bool try_lock() const { return psl_.try_lock(); }
287 static bool const kShouldUseHeap = ShouldUseHeap;
289 static constexpr std::size_t policyMaxSize() {
290 return SizeType(~(SizeType(1) << kLockBit | kExternMask));
293 std::size_t doSize() const {
294 return psl_.getData() & ~kExternMask;
297 std::size_t isExtern() const {
298 return psl_.getData() & kExternMask;
301 void setExtern(bool b) {
303 setSize(SizeType(doSize()) | kExternMask);
305 setSize(SizeType(doSize()) & ~kExternMask);
309 void setSize(std::size_t sz) {
310 assert(sz < (std::size_t(1) << kLockBit));
311 psl_.setData((kExternMask & psl_.getData()) | SizeType(sz));
314 void swapSizePolicy(OneBitMutexImpl& o) {
315 std::swap(psl_, o.psl_);
319 static SizeType const kLockBit = sizeof(SizeType) * 8 - 1;
320 static SizeType const kExternMask =
321 kShouldUseHeap ? SizeType(1) << (sizeof(SizeType) * 8 - 2)
324 PicoSpinLock<SizeType,kLockBit> psl_;
327 template<class SizeType, bool ShouldUseHeap>
328 struct OneBitMutexImpl {
329 static_assert(std::is_same<SizeType,void>::value,
330 "OneBitMutex only works on x86-64");
335 * If you're just trying to use this class, ignore everything about
336 * this next small_vector_base class thing.
338 * The purpose of this junk is to minimize sizeof(small_vector<>)
339 * and allow specifying the template parameters in whatever order is
340 * convenient for the user. There's a few extra steps here to try
341 * to keep the error messages at least semi-reasonable.
343 * Apologies for all the black magic.
345 namespace mpl = boost::mpl;
346 template<class Value,
347 std::size_t RequestedMaxInline,
351 struct small_vector_base {
352 typedef mpl::vector<InPolicyA,InPolicyB,InPolicyC> PolicyList;
355 * Determine the size type
357 typedef typename mpl::filter_view<
359 boost::is_integral<mpl::placeholders::_1>
361 typedef typename mpl::eval_if<
362 mpl::empty<Integrals>,
363 mpl::identity<std::size_t>,
364 mpl::front<Integrals>
367 static_assert(std::is_unsigned<SizeType>::value,
368 "Size type should be an unsigned integral type");
369 static_assert(mpl::size<Integrals>::value == 0 ||
370 mpl::size<Integrals>::value == 1,
371 "Multiple size types specified in small_vector<>");
374 * Figure out if we're supposed to supply a one-bit mutex. :)
376 typedef typename mpl::count<
377 PolicyList,small_vector_policy::OneBitMutex
380 static_assert(HasMutex::value == 0 || HasMutex::value == 1,
381 "Multiple copies of small_vector_policy::OneBitMutex "
382 "supplied; this is probably a mistake");
385 * Determine whether we should allow spilling to the heap or not.
387 typedef typename mpl::count<
388 PolicyList,small_vector_policy::NoHeap
391 static_assert(HasNoHeap::value == 0 || HasNoHeap::value == 1,
392 "Multiple copies of small_vector_policy::NoHeap "
393 "supplied; this is probably a mistake");
396 * Make the real policy base classes.
398 typedef typename mpl::if_<
400 OneBitMutexImpl<SizeType,!HasNoHeap::value>,
401 IntegralSizePolicy<SizeType,!HasNoHeap::value>
402 >::type ActualSizePolicy;
405 * Now inherit from them all. This is done in such a convoluted
406 * way to make sure we get the empty base optimizaton on all these
407 * types to keep sizeof(small_vector<>) minimal.
409 typedef boost::totally_ordered1<
410 small_vector<Value,RequestedMaxInline,InPolicyA,InPolicyB,InPolicyC>,
416 T* pointerFlagSet(T* p) {
417 return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(p) | 1);
420 bool pointerFlagGet(T* p) {
421 return reinterpret_cast<uintptr_t>(p) & 1;
424 T* pointerFlagClear(T* p) {
425 return reinterpret_cast<T*>(
426 reinterpret_cast<uintptr_t>(p) & ~uintptr_t(1));
428 inline void* shiftPointer(void* p, size_t sizeBytes) {
429 return static_cast<char*>(p) + sizeBytes;
433 //////////////////////////////////////////////////////////////////////
435 template<class Value,
436 std::size_t RequestedMaxInline = 1,
437 class PolicyA = void,
438 class PolicyB = void,
439 class PolicyC = void>
441 : public detail::small_vector_base<
442 Value,RequestedMaxInline,PolicyA,PolicyB,PolicyC
445 typedef typename detail::small_vector_base<
446 Value,RequestedMaxInline,PolicyA,PolicyB,PolicyC
448 typedef typename BaseType::InternalSizeType InternalSizeType;
451 * Figure out the max number of elements we should inline. (If
452 * the user asks for less inlined elements than we can fit unioned
453 * into our value_type*, we will inline more than they asked.)
456 MaxInline = boost::mpl::max<
457 boost::mpl::int_<sizeof(Value*) / sizeof(Value)>,
458 boost::mpl::int_<RequestedMaxInline>
463 typedef std::size_t size_type;
464 typedef Value value_type;
465 typedef value_type& reference;
466 typedef value_type const& const_reference;
467 typedef value_type* iterator;
468 typedef value_type const* const_iterator;
469 typedef std::ptrdiff_t difference_type;
471 typedef std::reverse_iterator<iterator> reverse_iterator;
472 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
474 explicit small_vector() {}
476 small_vector(small_vector const& o) {
477 assign(o.begin(), o.end());
480 small_vector(small_vector&& o) {
481 *this = std::move(o);
484 small_vector(std::initializer_list<value_type> il) {
485 constructImpl(il.begin(), il.end(), std::false_type());
488 explicit small_vector(size_type n, value_type const& t = value_type()) {
493 explicit small_vector(Arg arg1, Arg arg2) {
494 // Forward using std::is_arithmetic to get to the proper
495 // implementation; this disambiguates between the iterators and
496 // (size_t, value_type) meaning for this constructor.
497 constructImpl(arg1, arg2, std::is_arithmetic<Arg>());
501 for (auto& t : *this) {
504 if (this->isExtern()) {
509 small_vector& operator=(small_vector const& o) {
510 assign(o.begin(), o.end());
514 small_vector& operator=(small_vector&& o) {
518 for (std::size_t i = 0; i < o.size(); ++i) {
519 new (data() + i) value_type(std::move(o[i]));
521 this->setSize(o.size());
528 bool operator==(small_vector const& o) const {
529 return size() == o.size() && std::equal(begin(), end(), o.begin());
532 bool operator<(small_vector const& o) const {
533 return std::lexicographical_compare(begin(), end(), o.begin(), o.end());
536 static constexpr size_type max_size() {
537 return !BaseType::kShouldUseHeap ? MaxInline
538 : BaseType::policyMaxSize();
541 size_type size() const { return this->doSize(); }
542 bool empty() const { return !size(); }
544 iterator begin() { return data(); }
545 iterator end() { return data() + size(); }
546 const_iterator begin() const { return data(); }
547 const_iterator end() const { return data() + size(); }
548 const_iterator cbegin() const { return begin(); }
549 const_iterator cend() const { return end(); }
551 reverse_iterator rbegin() { return reverse_iterator(end()); }
552 reverse_iterator rend() { return reverse_iterator(begin()); }
554 const_reverse_iterator rbegin() const {
555 return const_reverse_iterator(end());
558 const_reverse_iterator rend() const {
559 return const_reverse_iterator(begin());
562 const_reverse_iterator crbegin() const { return rbegin(); }
563 const_reverse_iterator crend() const { return rend(); }
566 * Usually one of the simplest functions in a Container-like class
567 * but a bit more complex here. We have to handle all combinations
568 * of in-place vs. heap between this and o.
570 * Basic guarantee only. Provides the nothrow guarantee iff our
571 * value_type has a nothrow move or copy constructor.
573 void swap(small_vector& o) {
574 using std::swap; // Allow ADL on swap for our value_type.
576 if (this->isExtern() && o.isExtern()) {
577 this->swapSizePolicy(o);
579 auto thisCapacity = this->capacity();
580 auto oCapacity = o.capacity();
582 std::swap(unpackHack(&u.pdata_.heap_), unpackHack(&o.u.pdata_.heap_));
584 this->setCapacity(oCapacity);
585 o.setCapacity(thisCapacity);
590 if (!this->isExtern() && !o.isExtern()) {
591 auto& oldSmall = size() < o.size() ? *this : o;
592 auto& oldLarge = size() < o.size() ? o : *this;
594 for (size_type i = 0; i < oldSmall.size(); ++i) {
595 swap(oldSmall[i], oldLarge[i]);
598 size_type i = oldSmall.size();
600 for (; i < oldLarge.size(); ++i) {
601 new (&oldSmall[i]) value_type(std::move(oldLarge[i]));
602 oldLarge[i].~value_type();
605 for (; i < oldLarge.size(); ++i) {
606 oldLarge[i].~value_type();
608 oldLarge.setSize(oldSmall.size());
611 this->swapSizePolicy(o);
615 // isExtern != o.isExtern()
616 auto& oldExtern = o.isExtern() ? o : *this;
617 auto& oldIntern = o.isExtern() ? *this : o;
619 auto oldExternCapacity = oldExtern.capacity();
620 auto oldExternHeap = oldExtern.u.pdata_.heap_;
622 auto buff = oldExtern.u.buffer();
625 for (; i < oldIntern.size(); ++i) {
626 new (&buff[i]) value_type(std::move(oldIntern[i]));
627 oldIntern[i].~value_type();
630 for (size_type kill = 0; kill < i; ++kill) {
631 buff[kill].~value_type();
633 for (; i < oldIntern.size(); ++i) {
634 oldIntern[i].~value_type();
636 oldIntern.setSize(0);
637 oldExtern.u.pdata_.heap_ = oldExternHeap;
638 oldExtern.setCapacity(oldExternCapacity);
641 oldIntern.u.pdata_.heap_ = oldExternHeap;
642 this->swapSizePolicy(o);
643 oldIntern.setCapacity(oldExternCapacity);
646 void resize(size_type sz) {
648 erase(begin() + sz, end());
652 detail::populateMemForward(begin() + size(), sz - size(),
653 [&] (void* p) { new (p) value_type(); }
658 void resize(size_type sz, value_type const& v) {
660 erase(begin() + sz, end());
664 detail::populateMemForward(begin() + size(), sz - size(),
665 [&] (void* p) { new (p) value_type(v); }
670 value_type* data() noexcept {
671 return this->isExtern() ? u.heap() : u.buffer();
674 value_type const* data() const noexcept {
675 return this->isExtern() ? u.heap() : u.buffer();
678 template<class ...Args>
679 iterator emplace(const_iterator p, Args&&... args) {
681 emplace_back(std::forward<Args>(args)...);
686 * We implement emplace at places other than at the back with a
687 * temporary for exception safety reasons. It is possible to
688 * avoid having to do this, but it becomes hard to maintain the
689 * basic exception safety guarantee (unless you respond to a copy
690 * constructor throwing by clearing the whole vector).
692 * The reason for this is that otherwise you have to destruct an
693 * element before constructing this one in its place---if the
694 * constructor throws, you either need a nothrow default
695 * constructor or a nothrow copy/move to get something back in the
696 * "gap", and the vector requirements don't guarantee we have any
697 * of these. Clearing the whole vector is a legal response in
698 * this situation, but it seems like this implementation is easy
699 * enough and probably better.
701 return insert(p, value_type(std::forward<Args>(args)...));
704 void reserve(size_type sz) {
708 size_type capacity() const {
709 if (this->isExtern()) {
710 if (u.hasCapacity()) {
711 return *u.getCapacity();
713 return malloc_usable_size(u.pdata_.heap_) / sizeof(value_type);
718 void shrink_to_fit() {
719 if (!this->isExtern()) {
723 small_vector tmp(begin(), end());
727 template<class ...Args>
728 void emplace_back(Args&&... args) {
729 // call helper function for static dispatch of special cases
730 emplaceBack(std::forward<Args>(args)...);
733 void push_back(value_type&& t) {
734 if (capacity() == size()) {
735 makeSize(std::max(size_type(2), 3 * size() / 2), &t, size());
737 new (end()) value_type(std::move(t));
739 this->setSize(size() + 1);
742 void push_back(value_type const& t) {
743 // Make a copy and forward to the rvalue value_type&& overload
745 push_back(value_type(t));
752 iterator insert(const_iterator constp, value_type&& t) {
753 iterator p = unconst(constp);
756 push_back(std::move(t));
760 auto offset = p - begin();
762 if (capacity() == size()) {
763 makeSize(size() + 1, &t, offset);
764 this->setSize(this->size() + 1);
766 makeSize(size() + 1);
767 detail::moveObjectsRight(data() + offset,
769 data() + size() + 1);
770 this->setSize(size() + 1);
771 data()[offset] = std::move(t);
773 return begin() + offset;
777 iterator insert(const_iterator p, value_type const& t) {
778 // Make a copy and forward to the rvalue value_type&& overload
780 return insert(p, value_type(t));
783 iterator insert(const_iterator pos, size_type n, value_type const& val) {
784 auto offset = pos - begin();
785 makeSize(size() + n);
786 detail::moveObjectsRight(data() + offset,
788 data() + size() + n);
789 this->setSize(size() + n);
790 std::generate_n(begin() + offset, n, [&] { return val; });
791 return begin() + offset;
795 iterator insert(const_iterator p, Arg arg1, Arg arg2) {
796 // Forward using std::is_arithmetic to get to the proper
797 // implementation; this disambiguates between the iterators and
798 // (size_t, value_type) meaning for this function.
799 return insertImpl(unconst(p), arg1, arg2, std::is_arithmetic<Arg>());
802 iterator insert(const_iterator p, std::initializer_list<value_type> il) {
803 return insert(p, il.begin(), il.end());
806 iterator erase(const_iterator q) {
807 std::move(unconst(q) + 1, end(), unconst(q));
808 (data() + size() - 1)->~value_type();
809 this->setSize(size() - 1);
813 iterator erase(const_iterator q1, const_iterator q2) {
814 std::move(unconst(q2), end(), unconst(q1));
815 for (auto it = q1; it != end(); ++it) {
818 this->setSize(size() - (q2 - q1));
823 erase(begin(), end());
827 void assign(Arg first, Arg last) {
829 insert(end(), first, last);
832 void assign(std::initializer_list<value_type> il) {
833 assign(il.begin(), il.end());
836 void assign(size_type n, const value_type& t) {
841 reference front() { assert(!empty()); return *begin(); }
842 reference back() { assert(!empty()); return *(end() - 1); }
843 const_reference front() const { assert(!empty()); return *begin(); }
844 const_reference back() const { assert(!empty()); return *(end() - 1); }
846 reference operator[](size_type i) {
848 return *(begin() + i);
851 const_reference operator[](size_type i) const {
853 return *(begin() + i);
856 reference at(size_type i) {
858 throw std::out_of_range("index out of range");
863 const_reference at(size_type i) const {
865 throw std::out_of_range("index out of range");
873 * This is doing the same like emplace_back, but we need this helper
874 * to catch the special case - see the next overload function..
876 template<class ...Args>
877 void emplaceBack(Args&&... args) {
878 makeSize(size() + 1);
879 new (end()) value_type(std::forward<Args>(args)...);
880 this->setSize(size() + 1);
884 * Special case of emplaceBack for rvalue
886 void emplaceBack(value_type&& t) {
887 push_back(std::move(t));
890 static iterator unconst(const_iterator it) {
891 return const_cast<iterator>(it);
895 * g++ doesn't allow you to bind a non-const reference to a member
896 * of a packed structure, presumably because it would make it too
897 * easy to accidentally make an unaligned memory access?
899 template<class T> static T& unpackHack(T* p) {
903 // The std::false_type argument is part of disambiguating the
904 // iterator insert functions from integral types (see insert().)
906 iterator insertImpl(iterator pos, It first, It last, std::false_type) {
907 typedef typename std::iterator_traits<It>::iterator_category categ;
908 if (std::is_same<categ,std::input_iterator_tag>::value) {
909 auto offset = pos - begin();
910 while (first != last) {
911 pos = insert(pos, *first++);
914 return begin() + offset;
917 auto distance = std::distance(first, last);
918 auto offset = pos - begin();
919 makeSize(size() + distance);
920 detail::moveObjectsRight(data() + offset,
922 data() + size() + distance);
923 this->setSize(size() + distance);
924 std::copy_n(first, distance, begin() + offset);
925 return begin() + offset;
928 iterator insertImpl(iterator pos, size_type n, const value_type& val,
930 // The true_type means this should call the size_t,value_type
931 // overload. (See insert().)
932 return insert(pos, n, val);
935 // The std::false_type argument came from std::is_arithmetic as part
936 // of disambiguating an overload (see the comment in the
939 void constructImpl(It first, It last, std::false_type) {
940 typedef typename std::iterator_traits<It>::iterator_category categ;
941 if (std::is_same<categ,std::input_iterator_tag>::value) {
942 // With iterators that only allow a single pass, we can't really
943 // do anything sane here.
944 while (first != last) {
950 auto distance = std::distance(first, last);
952 this->setSize(distance);
954 detail::populateMemForward(data(), distance,
955 [&] (void* p) { new (p) value_type(*first++); }
959 void doConstruct(size_type n, value_type const& val) {
962 detail::populateMemForward(data(), n,
963 [&] (void* p) { new (p) value_type(val); }
967 // The true_type means we should forward to the size_t,value_type
969 void constructImpl(size_type n, value_type const& val, std::true_type) {
973 void makeSize(size_type size, value_type* v = nullptr) {
974 makeSize(size, v, size - 1);
978 * Ensure we have a large enough memory region to be size `size'.
979 * Will move/copy elements if we are spilling to heap_ or needed to
980 * allocate a new region, but if resized in place doesn't initialize
981 * anything in the new region. In any case doesn't change size().
982 * Supports insertion of new element during reallocation by given
983 * pointer to new element and position of new element.
984 * NOTE: If reallocation is not needed, and new element should be
985 * inserted in the middle of vector (not at the end), do the move
986 * objects and insertion outside the function, otherwise exception is thrown.
988 void makeSize(size_type size, value_type* v, size_type pos) {
989 if (size > this->max_size()) {
990 throw std::length_error("max_size exceeded in small_vector");
992 if (size <= this->capacity()) {
996 auto needBytes = size * sizeof(value_type);
997 // If the capacity isn't explicitly stored inline, but the heap
998 // allocation is grown to over some threshold, we should store
999 // a capacity at the front of the heap allocation.
1000 bool heapifyCapacity =
1001 !kHasInlineCapacity && needBytes > kHeapifyCapacityThreshold;
1002 if (heapifyCapacity) {
1003 needBytes += kHeapifyCapacitySize;
1005 auto const sizeBytes = goodMallocSize(needBytes);
1006 void* newh = checkedMalloc(sizeBytes);
1007 // We expect newh to be at least 2-aligned, because we want to
1008 // use its least significant bit as a flag.
1009 assert(!detail::pointerFlagGet(newh));
1011 value_type* newp = static_cast<value_type*>(
1013 detail::shiftPointer(newh, kHeapifyCapacitySize) :
1019 new (&newp[pos]) value_type(std::move(*v));
1025 // move old elements to the left of the new one
1027 detail::moveToUninitialized(begin(), begin() + pos, newp);
1029 newp[pos].~value_type();
1034 // move old elements to the right of the new one
1037 detail::moveToUninitialized(begin() + pos, end(), newp + pos + 1);
1040 for (size_type i = 0; i <= pos; ++i) {
1041 newp[i].~value_type();
1047 // move without inserting new element
1049 detail::moveToUninitialized(begin(), end(), newp);
1055 for (auto& val : *this) {
1059 if (this->isExtern()) {
1062 auto availableSizeBytes = sizeBytes;
1063 if (heapifyCapacity) {
1064 u.pdata_.heap_ = detail::pointerFlagSet(newh);
1065 availableSizeBytes -= kHeapifyCapacitySize;
1067 u.pdata_.heap_ = newh;
1069 this->setExtern(true);
1070 this->setCapacity(availableSizeBytes / sizeof(value_type));
1074 * This will set the capacity field, stored inline in the storage_ field
1075 * if there is sufficient room to store it.
1077 void setCapacity(size_type newCapacity) {
1078 assert(this->isExtern());
1079 if (u.hasCapacity()) {
1080 assert(newCapacity < std::numeric_limits<InternalSizeType>::max());
1081 *u.getCapacity() = InternalSizeType(newCapacity);
1086 struct HeapPtrWithCapacity {
1088 InternalSizeType capacity_;
1090 InternalSizeType* getCapacity() {
1096 // Lower order bit of heap_ is used as flag to indicate whether capacity is
1097 // stored at the front of the heap allocation.
1100 InternalSizeType* getCapacity() {
1101 assert(detail::pointerFlagGet(heap_));
1102 return static_cast<InternalSizeType*>(
1103 detail::pointerFlagClear(heap_));
1108 typedef unsigned char InlineStorageType[sizeof(value_type) * MaxInline];
1110 typedef typename std::aligned_storage<
1111 sizeof(value_type) * MaxInline,
1113 >::type InlineStorageType;
1116 static bool const kHasInlineCapacity =
1117 sizeof(HeapPtrWithCapacity) < sizeof(InlineStorageType);
1119 // This value should we multiple of word size.
1120 static size_t const kHeapifyCapacitySize = sizeof(
1121 typename std::aligned_storage<
1122 sizeof(InternalSizeType),
1125 // Threshold to control capacity heapifying.
1126 static size_t const kHeapifyCapacityThreshold =
1127 100 * kHeapifyCapacitySize;
1129 typedef typename std::conditional<
1131 HeapPtrWithCapacity,
1133 >::type PointerType;
1136 explicit Data() { pdata_.heap_ = 0; }
1139 InlineStorageType storage_;
1141 value_type* buffer() noexcept {
1142 void* vp = &storage_;
1143 return static_cast<value_type*>(vp);
1145 value_type const* buffer() const noexcept {
1146 return const_cast<Data*>(this)->buffer();
1148 value_type* heap() noexcept {
1149 if (kHasInlineCapacity || !detail::pointerFlagGet(pdata_.heap_)) {
1150 return static_cast<value_type*>(pdata_.heap_);
1152 return static_cast<value_type*>(
1153 detail::shiftPointer(
1154 detail::pointerFlagClear(pdata_.heap_), kHeapifyCapacitySize));
1156 value_type const* heap() const noexcept {
1157 return const_cast<Data*>(this)->heap();
1160 bool hasCapacity() const {
1161 return kHasInlineCapacity || detail::pointerFlagGet(pdata_.heap_);
1163 InternalSizeType* getCapacity() {
1164 return pdata_.getCapacity();
1166 InternalSizeType* getCapacity() const {
1167 return const_cast<Data*>(this)->getCapacity();
1171 auto vp = detail::pointerFlagClear(pdata_.heap_);
1178 //////////////////////////////////////////////////////////////////////
1180 // Basic guarantee only, or provides the nothrow guarantee iff T has a
1181 // nothrow move or copy constructor.
1182 template<class T, std::size_t MaxInline, class A, class B, class C>
1183 void swap(small_vector<T,MaxInline,A,B,C>& a,
1184 small_vector<T,MaxInline,A,B,C>& b) {
1188 //////////////////////////////////////////////////////////////////////
1192 #pragma GCC diagnostic pop
1195 # undef FB_PACK_ATTR
1196 # undef FB_PACK_PUSH