/*
* Copyright 2011-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Nicholas Ormrod (njormrod)
* Andrei Alexandrescu (aalexandre)
*
* FBVector is Facebook's drop-in implementation of std::vector. It has special
* optimizations for use with relocatable types and jemalloc.
*/
#pragma once
//=============================================================================
// headers
#include <algorithm>
#include <cassert>
#include <iterator>
#include <memory>
#include <stdexcept>
#include <type_traits>
#include <utility>
#include <folly/FormatTraits.h>
#include <folly/Likely.h>
#include <folly/Traits.h>
#include <folly/lang/Exception.h>
#include <folly/memory/Malloc.h>
//=============================================================================
// forward declaration
namespace folly {
template <class T, class Allocator = std::allocator<T>>
class fbvector;
} // namespace folly
//=============================================================================
// unrolling
#define FOLLY_FBV_UNROLL_PTR(first, last, OP) \
do { \
for (; (last) - (first) >= 4; (first) += 4) { \
OP(((first) + 0)); \
OP(((first) + 1)); \
OP(((first) + 2)); \
OP(((first) + 3)); \
} \
for (; (first) != (last); ++(first)) \
OP((first)); \
} while (0);
//=============================================================================
///////////////////////////////////////////////////////////////////////////////
// //
// fbvector class //
// //
///////////////////////////////////////////////////////////////////////////////
namespace folly {
template <class T, class Allocator>
class fbvector {
//===========================================================================
//---------------------------------------------------------------------------
// implementation
private:
typedef std::allocator_traits<Allocator> A;
struct Impl : public Allocator {
// typedefs
typedef typename A::pointer pointer;
typedef typename A::size_type size_type;
// data
pointer b_, e_, z_;
// constructors
Impl() : Allocator(), b_(nullptr), e_(nullptr), z_(nullptr) {}
/* implicit */ Impl(const Allocator& alloc)
: Allocator(alloc), b_(nullptr), e_(nullptr), z_(nullptr) {}
/* implicit */ Impl(Allocator&& alloc)
: Allocator(std::move(alloc)), b_(nullptr), e_(nullptr), z_(nullptr) {}
/* implicit */ Impl(size_type n, const Allocator& alloc = Allocator())
: Allocator(alloc) {
init(n);
}
Impl(Impl&& other) noexcept
: Allocator(std::move(other)),
b_(other.b_),
e_(other.e_),
z_(other.z_) {
other.b_ = other.e_ = other.z_ = nullptr;
}
// destructor
~Impl() {
destroy();
}
// allocation
// note that 'allocate' and 'deallocate' are inherited from Allocator
T* D_allocate(size_type n) {
if (usingStdAllocator::value) {
return static_cast<T*>(checkedMalloc(n * sizeof(T)));
} else {
return std::allocator_traits<Allocator>::allocate(*this, n);
}
}
void D_deallocate(T* p, size_type n) noexcept {
if (usingStdAllocator::value) {
free(p);
} else {
std::allocator_traits<Allocator>::deallocate(*this, p, n);
}
}
// helpers
void swapData(Impl& other) {
std::swap(b_, other.b_);
std::swap(e_, other.e_);
std::swap(z_, other.z_);
}
// data ops
inline void destroy() noexcept {
if (b_) {
// THIS DISPATCH CODE IS DUPLICATED IN fbvector::D_destroy_range_a.
// It has been inlined here for speed. It calls the static fbvector
// methods to perform the actual destruction.
if (usingStdAllocator::value) {
S_destroy_range(b_, e_);
} else {
S_destroy_range_a(*this, b_, e_);
}
D_deallocate(b_, size_type(z_ - b_));
}
}
void init(size_type n) {
if (UNLIKELY(n == 0)) {
b_ = e_ = z_ = nullptr;
} else {
size_type sz = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
b_ = D_allocate(sz);
e_ = b_;
z_ = b_ + sz;
}
}
void set(pointer newB, size_type newSize, size_type newCap) {
z_ = newB + newCap;
e_ = newB + newSize;
b_ = newB;
}
void reset(size_type newCap) {
destroy();
try {
init(newCap);
} catch (...) {
init(0);
throw;
}
}
void reset() { // same as reset(0)
destroy();
b_ = e_ = z_ = nullptr;
}
} impl_;
static void swap(Impl& a, Impl& b) {
using std::swap;
if (!usingStdAllocator::value) {
swap(static_cast<Allocator&>(a), static_cast<Allocator&>(b));
}
a.swapData(b);
}
//===========================================================================
//---------------------------------------------------------------------------
// types and constants
public:
typedef T value_type;
typedef value_type& reference;
typedef const value_type& const_reference;
typedef T* iterator;
typedef const T* const_iterator;
typedef size_t size_type;
typedef typename std::make_signed<size_type>::type difference_type;
typedef Allocator allocator_type;
typedef typename A::pointer pointer;
typedef typename A::const_pointer const_pointer;
typedef std::reverse_iterator<iterator> reverse_iterator;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
private:
typedef bool_constant<
is_trivially_copyable<T>::value &&
sizeof(T) <= 16 // don't force large structures to be passed by value
>
should_pass_by_value;
typedef
typename std::conditional<should_pass_by_value::value, T, const T&>::type
VT;
typedef
typename std::conditional<should_pass_by_value::value, T, T&&>::type MT;
typedef bool_constant<std::is_same<Allocator, std::allocator<T>>::value>
usingStdAllocator;
typedef bool_constant<
usingStdAllocator::value ||
A::propagate_on_container_move_assignment::value>
moveIsSwap;
//===========================================================================
//---------------------------------------------------------------------------
// allocator helpers
private:
//---------------------------------------------------------------------------
// allocate
T* M_allocate(size_type n) {
return impl_.D_allocate(n);
}
//---------------------------------------------------------------------------
// deallocate
void M_deallocate(T* p, size_type n) noexcept {
impl_.D_deallocate(p, n);
}
//---------------------------------------------------------------------------
// construct
// GCC is very sensitive to the exact way that construct is called. For
// that reason there are several different specializations of construct.
template <typename U, typename... Args>
void M_construct(U* p, Args&&... args) {
if (usingStdAllocator::value) {
new (p) U(std::forward<Args>(args)...);
} else {
std::allocator_traits<Allocator>::construct(
impl_, p, std::forward<Args>(args)...);
}
}
template <typename U, typename... Args>
static void S_construct(U* p, Args&&... args) {
new (p) U(std::forward<Args>(args)...);
}
template <typename U, typename... Args>
static void S_construct_a(Allocator& a, U* p, Args&&... args) {
std::allocator_traits<Allocator>::construct(
a, p, std::forward<Args>(args)...);
}
// scalar optimization
// TODO we can expand this optimization to: default copyable and assignable
template <
typename U,
typename Enable = typename std::enable_if<std::is_scalar<U>::value>::type>
void M_construct(U* p, U arg) {
if (usingStdAllocator::value) {
*p = arg;
} else {
std::allocator_traits<Allocator>::construct(impl_, p, arg);
}
}
template <
typename U,
typename Enable = typename std::enable_if<std::is_scalar<U>::value>::type>
static void S_construct(U* p, U arg) {
*p = arg;
}
template <
typename U,
typename Enable = typename std::enable_if<std::is_scalar<U>::value>::type>
static void S_construct_a(Allocator& a, U* p, U arg) {
std::allocator_traits<Allocator>::construct(a, p, arg);
}
// const& optimization
template <
typename U,
typename Enable =
typename std::enable_if<!std::is_scalar<U>::value>::type>
void M_construct(U* p, const U& value) {
if (usingStdAllocator::value) {
new (p) U(value);
} else {
std::allocator_traits<Allocator>::construct(impl_, p, value);
}
}
template <
typename U,
typename Enable =
typename std::enable_if<!std::is_scalar<U>::value>::type>
static void S_construct(U* p, const U& value) {
new (p) U(value);
}
template <
typename U,
typename Enable =
typename std::enable_if<!std::is_scalar<U>::value>::type>
static void S_construct_a(Allocator& a, U* p, const U& value) {
std::allocator_traits<Allocator>::construct(a, p, value);
}
//---------------------------------------------------------------------------
// destroy
void M_destroy(T* p) noexcept {
if (usingStdAllocator::value) {
if (!std::is_trivially_destructible<T>::value) {
p->~T();
}
} else {
std::allocator_traits<Allocator>::destroy(impl_, p);
}
}
//===========================================================================
//---------------------------------------------------------------------------
// algorithmic helpers
private:
//---------------------------------------------------------------------------
// destroy_range
// wrappers
void M_destroy_range_e(T* pos) noexcept {
D_destroy_range_a(pos, impl_.e_);
impl_.e_ = pos;
}
// dispatch
// THIS DISPATCH CODE IS DUPLICATED IN IMPL. SEE IMPL FOR DETAILS.
void D_destroy_range_a(T* first, T* last) noexcept {
if (usingStdAllocator::value) {
S_destroy_range(first, last);
} else {
S_destroy_range_a(impl_, first, last);
}
}
// allocator
static void S_destroy_range_a(Allocator& a, T* first, T* last) noexcept {
for (; first != last; ++first) {
std::allocator_traits<Allocator>::destroy(a, first);
}
}
// optimized
static void S_destroy_range(T* first, T* last) noexcept {
if (!std::is_trivially_destructible<T>::value) {
#define FOLLY_FBV_OP(p) (p)->~T()
// EXPERIMENTAL DATA on fbvector<vector<int>> (where each vector<int> has
// size 0).
// The unrolled version seems to work faster for small to medium sized
// fbvectors. It gets a 10% speedup on fbvectors of size 1024, 64, and
// 16.
// The simple loop version seems to work faster for large fbvectors. The
// unrolled version is about 6% slower on fbvectors on size 16384.
// The two methods seem tied for very large fbvectors. The unrolled
// version is about 0.5% slower on size 262144.
// for (; first != last; ++first) first->~T();
FOLLY_FBV_UNROLL_PTR(first, last, FOLLY_FBV_OP)
#undef FOLLY_FBV_OP
}
}
//---------------------------------------------------------------------------
// uninitialized_fill_n
// wrappers
void M_uninitialized_fill_n_e(size_type sz) {
D_uninitialized_fill_n_a(impl_.e_, sz);
impl_.e_ += sz;
}
void M_uninitialized_fill_n_e(size_type sz, VT value) {
D_uninitialized_fill_n_a(impl_.e_, sz, value);
impl_.e_ += sz;
}
// dispatch
void D_uninitialized_fill_n_a(T* dest, size_type sz) {
if (usingStdAllocator::value) {
S_uninitialized_fill_n(dest, sz);
} else {
S_uninitialized_fill_n_a(impl_, dest, sz);
}
}
void D_uninitialized_fill_n_a(T* dest, size_type sz, VT value) {
if (usingStdAllocator::value) {
S_uninitialized_fill_n(dest, sz, value);
} else {
S_uninitialized_fill_n_a(impl_, dest, sz, value);
}
}
// allocator
template <typename... Args>
static void S_uninitialized_fill_n_a(
Allocator& a,
T* dest,
size_type sz,
Args&&... args) {
auto b = dest;
auto e = dest + sz;
try {
for (; b != e; ++b) {
std::allocator_traits<Allocator>::construct(
a, b, std::forward<Args>(args)...);
}
} catch (...) {
S_destroy_range_a(a, dest, b);
throw;
}
}
// optimized
static void S_uninitialized_fill_n(T* dest, size_type n) {
if (folly::IsZeroInitializable<T>::value) {
if (LIKELY(n != 0)) {
std::memset(dest, 0, sizeof(T) * n);
}
} else {
auto b = dest;
auto e = dest + n;
try {
for (; b != e; ++b) {
S_construct(b);
}
} catch (...) {
--b;
for (; b >= dest; --b) {
b->~T();
}
throw;
}
}
}
static void S_uninitialized_fill_n(T* dest, size_type n, const T& value) {
auto b = dest;
auto e = dest + n;
try {
for (; b != e; ++b) {
S_construct(b, value);
}
} catch (...) {
S_destroy_range(dest, b);
throw;
}
}
//---------------------------------------------------------------------------
// uninitialized_copy
// it is possible to add an optimization for the case where
// It = move(T*) and IsRelocatable<T> and Is0Initiailizable<T>
// wrappers
template <typename It>
void M_uninitialized_copy_e(It first, It last) {
D_uninitialized_copy_a(impl_.e_, first, last);
impl_.e_ += std::distance(first, last);
}
template <typename It>
void M_uninitialized_move_e(It first, It last) {
D_uninitialized_move_a(impl_.e_, first, last);
impl_.e_ += std::distance(first, last);
}
// dispatch
template <typename It>
void D_uninitialized_copy_a(T* dest, It first, It last) {
if (usingStdAllocator::value) {
if (folly::is_trivially_copyable<T>::value) {
S_uninitialized_copy_bits(dest, first, last);
} else {
S_uninitialized_copy(dest, first, last);
}
} else {
S_uninitialized_copy_a(impl_, dest, first, last);
}
}
template <typename It>
void D_uninitialized_move_a(T* dest, It first, It last) {
D_uninitialized_copy_a(
dest, std::make_move_iterator(first), std::make_move_iterator(last));
}
// allocator
template <typename It>
static void S_uninitialized_copy_a(Allocator& a, T* dest, It first, It last) {
auto b = dest;
try {
for (; first != last; ++first, ++b) {
std::allocator_traits<Allocator>::construct(a, b, *first);
}
} catch (...) {
S_destroy_range_a(a, dest, b);
throw;
}
}
// optimized
template <typename It>
static void S_uninitialized_copy(T* dest, It first, It last) {
auto b = dest;
try {
for (; first != last; ++first, ++b) {
S_construct(b, *first);
}
} catch (...) {
S_destroy_range(dest, b);
throw;
}
}
static void
S_uninitialized_copy_bits(T* dest, const T* first, const T* last) {
if (last != first) {
std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
}
}
static void S_uninitialized_copy_bits(
T* dest,
std::move_iterator<T*> first,
std::move_iterator<T*> last) {
T* bFirst = first.base();
T* bLast = last.base();
if (bLast != bFirst) {
std::memcpy((void*)dest, (void*)bFirst, (bLast - bFirst) * sizeof(T));
}
}
template <typename It>
static void S_uninitialized_copy_bits(T* dest, It first, It last) {
S_uninitialized_copy(dest, first, last);
}
//---------------------------------------------------------------------------
// copy_n
// This function is "unsafe": it assumes that the iterator can be advanced at
// least n times. However, as a private function, that unsafety is managed
// wholly by fbvector itself.
template <typename It>
static It S_copy_n(T* dest, It first, size_type n) {
auto e = dest + n;
for (; dest != e; ++dest, ++first) {
*dest = *first;
}
return first;
}
static const T* S_copy_n(T* dest, const T* first, size_type n) {
if (is_trivially_copyable<T>::value) {
std::memcpy((void*)dest, (void*)first, n * sizeof(T));
return first + n;
} else {
return S_copy_n<const T*>(dest, first, n);
}
}
static std::move_iterator<T*>
S_copy_n(T* dest, std::move_iterator<T*> mIt, size_type n) {
if (is_trivially_copyable<T>::value) {
T* first = mIt.base();
std::memcpy((void*)dest, (void*)first, n * sizeof(T));
return std::make_move_iterator(first + n);
} else {
return S_copy_n<std::move_iterator<T*>>(dest, mIt, n);
}
}
//===========================================================================
//---------------------------------------------------------------------------
// relocation helpers
private:
// Relocation is divided into three parts:
//
// 1: relocate_move
// Performs the actual movement of data from point a to point b.
//
// 2: relocate_done
// Destroys the old data.
//
// 3: relocate_undo
// Destoys the new data and restores the old data.
//
// The three steps are used because there may be an exception after part 1
// has completed. If that is the case, then relocate_undo can nullify the
// initial move. Otherwise, relocate_done performs the last bit of tidying
// up.
//
// The relocation trio may use either memcpy, move, or copy. It is decided
// by the following case statement:
//
// IsRelocatable && usingStdAllocator -> memcpy
// has_nothrow_move && usingStdAllocator -> move
// cannot copy -> move
// default -> copy
//
// If the class is non-copyable then it must be movable. However, if the
// move constructor is not noexcept, i.e. an error could be thrown, then
// relocate_undo will be unable to restore the old data, for fear of a
// second exception being thrown. This is a known and unavoidable
// deficiency. In lieu of a strong exception guarantee, relocate_undo does
// the next best thing: it provides a weak exception guarantee by
// destorying the new data, but leaving the old data in an indeterminate
// state. Note that that indeterminate state will be valid, since the
// old data has not been destroyed; it has merely been the source of a
// move, which is required to leave the source in a valid state.
// wrappers
void M_relocate(T* newB) {
relocate_move(newB, impl_.b_, impl_.e_);
relocate_done(newB, impl_.b_, impl_.e_);
}
// dispatch type trait
typedef bool_constant<
folly::IsRelocatable<T>::value && usingStdAllocator::value>
relocate_use_memcpy;
typedef bool_constant<
(std::is_nothrow_move_constructible<T>::value &&
usingStdAllocator::value) ||
!std::is_copy_constructible<T>::value>
relocate_use_move;
// move
void relocate_move(T* dest, T* first, T* last) {
relocate_move_or_memcpy(dest, first, last, relocate_use_memcpy());
}
void relocate_move_or_memcpy(T* dest, T* first, T* last, std::true_type) {
if (first != nullptr) {
std::memcpy((void*)dest, (void*)first, (last - first) * sizeof(T));
}
}
void relocate_move_or_memcpy(T* dest, T* first, T* last, std::false_type) {
relocate_move_or_copy(dest, first, last, relocate_use_move());
}
void relocate_move_or_copy(T* dest, T* first, T* last, std::true_type) {
D_uninitialized_move_a(dest, first, last);
}
void relocate_move_or_copy(T* dest, T* first, T* last, std::false_type) {
D_uninitialized_copy_a(dest, first, last);
}
// done
void relocate_done(T* /*dest*/, T* first, T* last) noexcept {
if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
// used memcpy; data has been relocated, do not call destructor
} else {
D_destroy_range_a(first, last);
}
}
// undo
void relocate_undo(T* dest, T* first, T* last) noexcept {
if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
// used memcpy, old data is still valid, nothing to do
} else if (
std::is_nothrow_move_constructible<T>::value &&
usingStdAllocator::value) {
// noexcept move everything back, aka relocate_move
relocate_move(first, dest, dest + (last - first));
} else if (!std::is_copy_constructible<T>::value) {
// weak guarantee
D_destroy_range_a(dest, dest + (last - first));
} else {
// used copy, old data is still valid
D_destroy_range_a(dest, dest + (last - first));
}
}
//===========================================================================
//---------------------------------------------------------------------------
// construct/copy/destroy
public:
fbvector() = default;
explicit fbvector(const Allocator& a) : impl_(a) {}
explicit fbvector(size_type n, const Allocator& a = Allocator())
: impl_(n, a) {
M_uninitialized_fill_n_e(n);
}
fbvector(size_type n, VT value, const Allocator& a = Allocator())
: impl_(n, a) {
M_uninitialized_fill_n_e(n, value);
}
template <
class It,
class Category = typename std::iterator_traits<It>::iterator_category>
fbvector(It first, It last, const Allocator& a = Allocator())
: fbvector(first, last, a, Category()) {}
fbvector(const fbvector& other)
: impl_(
other.size(),
A::select_on_container_copy_construction(other.impl_)) {
M_uninitialized_copy_e(other.begin(), other.end());
}
fbvector(fbvector&& other) noexcept : impl_(std::move(other.impl_)) {}
fbvector(const fbvector& other, const Allocator& a)
: fbvector(other.begin(), other.end(), a) {}
/* may throw */ fbvector(fbvector&& other, const Allocator& a) : impl_(a) {
if (impl_ == other.impl_) {
impl_.swapData(other.impl_);
} else {
impl_.init(other.size());
M_uninitialized_move_e(other.begin(), other.end());
}
}
fbvector(std::initializer_list<T> il, const Allocator& a = Allocator())
: fbvector(il.begin(), il.end(), a) {}
~fbvector() = default; // the cleanup occurs in impl_
fbvector& operator=(const fbvector& other) {
if (UNLIKELY(this == &other)) {
return *this;
}
if (!usingStdAllocator::value &&
A::propagate_on_container_copy_assignment::value) {
if (impl_ != other.impl_) {
// can't use other's different allocator to clean up self
impl_.reset();
}
(Allocator&)impl_ = (Allocator&)other.impl_;
}
assign(other.begin(), other.end());
return *this;
}
fbvector& operator=(fbvector&& other) {
if (UNLIKELY(this == &other)) {
return *this;
}
moveFrom(std::move(other), moveIsSwap());
return *this;
}
fbvector& operator=(std::initializer_list<T> il) {
assign(il.begin(), il.end());
return *this;
}
template <
class It,
class Category = typename std::iterator_traits<It>::iterator_category>
void assign(It first, It last) {
assign(first, last, Category());
}
void assign(size_type n, VT value) {
if (n > capacity()) {
// Not enough space. Do not reserve in place, since we will
// discard the old values anyways.
if (dataIsInternalAndNotVT(value)) {
T copy(std::move(value));
impl_.reset(n);
M_uninitialized_fill_n_e(n, copy);
} else {
impl_.reset(n);
M_uninitialized_fill_n_e(n, value);
}
} else if (n <= size()) {
auto newE = impl_.b_ + n;
std::fill(impl_.b_, newE, value);
M_destroy_range_e(newE);
} else {
std::fill(impl_.b_, impl_.e_, value);
M_uninitialized_fill_n_e(n - size(), value);
}
}
void assign(std::initializer_list<T> il) {
assign(il.begin(), il.end());
}
allocator_type get_allocator() const noexcept {
return impl_;
}
private:
// contract dispatch for iterator types fbvector(It first, It last)
template <class ForwardIterator>
fbvector(
ForwardIterator first,
ForwardIterator last,
const Allocator& a,
std::forward_iterator_tag)
: impl_(size_type(std::distance(first, last)), a) {
M_uninitialized_copy_e(first, last);
}
template <class InputIterator>
fbvector(
InputIterator first,
InputIterator last,
const Allocator& a,
std::input_iterator_tag)
: impl_(a) {
for (; first != last; ++first) {
emplace_back(*first);
}
}
// contract dispatch for allocator movement in operator=(fbvector&&)
void moveFrom(fbvector&& other, std::true_type) {
swap(impl_, other.impl_);
}
void moveFrom(fbvector&& other, std::false_type) {
if (impl_ == other.impl_) {
impl_.swapData(other.impl_);
} else {
impl_.reset(other.size());
M_uninitialized_move_e(other.begin(), other.end());
}
}
// contract dispatch for iterator types in assign(It first, It last)
template <class ForwardIterator>
void assign(
ForwardIterator first,
ForwardIterator last,
std::forward_iterator_tag) {
const auto newSize = size_type(std::distance(first, last));
if (newSize > capacity()) {
impl_.reset(newSize);
M_uninitialized_copy_e(first, last);
} else if (newSize <= size()) {
auto newEnd = std::copy(first, last, impl_.b_);
M_destroy_range_e(newEnd);
} else {
auto mid = S_copy_n(impl_.b_, first, size());
M_uninitialized_copy_e<decltype(last)>(mid, last);
}
}
template <class InputIterator>
void
assign(InputIterator first, InputIterator last, std::input_iterator_tag) {
auto p = impl_.b_;
for (; first != last && p != impl_.e_; ++first, ++p) {
*p = *first;
}
if (p != impl_.e_) {
M_destroy_range_e(p);
} else {
for (; first != last; ++first) {
emplace_back(*first);
}
}
}
// contract dispatch for aliasing under VT optimization
bool dataIsInternalAndNotVT(const T& t) {
if (should_pass_by_value::value) {
return false;
}
return dataIsInternal(t);
}
bool dataIsInternal(const T& t) {
return UNLIKELY(
impl_.b_ <= std::addressof(t) && std::addressof(t) < impl_.e_);
}
//===========================================================================
//---------------------------------------------------------------------------
// iterators
public:
iterator begin() noexcept {
return impl_.b_;
}
const_iterator begin() const noexcept {
return impl_.b_;
}
iterator end() noexcept {
return impl_.e_;
}
const_iterator end() const noexcept {
return impl_.e_;
}
reverse_iterator rbegin() noexcept {
return reverse_iterator(end());
}
const_reverse_iterator rbegin() const noexcept {
return const_reverse_iterator(end());
}
reverse_iterator rend() noexcept {
return reverse_iterator(begin());
}
const_reverse_iterator rend() const noexcept {
return const_reverse_iterator(begin());
}
const_iterator cbegin() const noexcept {
return impl_.b_;
}
const_iterator cend() const noexcept {
return impl_.e_;
}
const_reverse_iterator crbegin() const noexcept {
return const_reverse_iterator(end());
}
const_reverse_iterator crend() const noexcept {
return const_reverse_iterator(begin());
}
//===========================================================================
//---------------------------------------------------------------------------
// capacity
public:
size_type size() const noexcept {
return size_type(impl_.e_ - impl_.b_);
}
size_type max_size() const noexcept {
// good luck gettin' there
return ~size_type(0);
}
void resize(size_type n) {
if (n <= size()) {
M_destroy_range_e(impl_.b_ + n);
} else {
reserve(n);
M_uninitialized_fill_n_e(n - size());
}
}
void resize(size_type n, VT t) {
if (n <= size()) {
M_destroy_range_e(impl_.b_ + n);
} else if (dataIsInternalAndNotVT(t) && n > capacity()) {
T copy(t);
reserve(n);
M_uninitialized_fill_n_e(n - size(), copy);
} else {
reserve(n);
M_uninitialized_fill_n_e(n - size(), t);
}
}
size_type capacity() const noexcept {
return size_type(impl_.z_ - impl_.b_);
}
bool empty() const noexcept {
return impl_.b_ == impl_.e_;
}
void reserve(size_type n) {
if (n <= capacity()) {
return;
}
if (impl_.b_ && reserve_in_place(n)) {
return;
}
auto newCap = folly::goodMallocSize(n * sizeof(T)) / sizeof(T);
auto newB = M_allocate(newCap);
try {
M_relocate(newB);
} catch (...) {
M_deallocate(newB, newCap);
throw;
}
if (impl_.b_) {
M_deallocate(impl_.b_, size_type(impl_.z_ - impl_.b_));
}
impl_.z_ = newB + newCap;
impl_.e_ = newB + (impl_.e_ - impl_.b_);
impl_.b_ = newB;
}
void shrink_to_fit() noexcept {
if (empty()) {
impl_.reset();
return;
}
auto const newCapacityBytes = folly::goodMallocSize(size() * sizeof(T));
auto const newCap = newCapacityBytes / sizeof(T);
auto const oldCap = capacity();
if (newCap >= oldCap) {
return;
}
void* p = impl_.b_;
// xallocx() will shrink to precisely newCapacityBytes (which was generated
// by goodMallocSize()) if it successfully shrinks in place.
if ((usingJEMalloc() && usingStdAllocator::value) &&
newCapacityBytes >= folly::jemallocMinInPlaceExpandable &&
xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
impl_.z_ += newCap - oldCap;
} else {
T* newB; // intentionally uninitialized
try {
newB = M_allocate(newCap);
try {
M_relocate(newB);
} catch (...) {
M_deallocate(newB, newCap);
return; // swallow the error
}
} catch (...) {
return;
}
if (impl_.b_) {
M_deallocate(impl_.b_, size_type(impl_.z_ - impl_.b_));
}
impl_.z_ = newB + newCap;
impl_.e_ = newB + (impl_.e_ - impl_.b_);
impl_.b_ = newB;
}
}
private:
bool reserve_in_place(size_type n) {
if (!usingStdAllocator::value || !usingJEMalloc()) {
return false;
}
// jemalloc can never grow in place blocks smaller than 4096 bytes.
if ((impl_.z_ - impl_.b_) * sizeof(T) <
folly::jemallocMinInPlaceExpandable) {
return false;
}
auto const newCapacityBytes = folly::goodMallocSize(n * sizeof(T));
void* p = impl_.b_;
if (xallocx(p, newCapacityBytes, 0, 0) == newCapacityBytes) {
impl_.z_ = impl_.b_ + newCapacityBytes / sizeof(T);
return true;
}
return false;
}
//===========================================================================
//---------------------------------------------------------------------------
// element access
public:
reference operator[](size_type n) {
assert(n < size());
return impl_.b_[n];
}
const_reference operator[](size_type n) const {
assert(n < size());
return impl_.b_[n];
}
const_reference at(size_type n) const {
if (UNLIKELY(n >= size())) {
throw_exception<std::out_of_range>(
"fbvector: index is greater than size.");
}
return (*this)[n];
}
reference at(size_type n) {
auto const& cThis = *this;
return const_cast<reference>(cThis.at(n));
}
reference front() {
assert(!empty());
return *impl_.b_;
}
const_reference front() const {
assert(!empty());
return *impl_.b_;
}
reference back() {
assert(!empty());
return impl_.e_[-1];
}
const_reference back() const {
assert(!empty());
return impl_.e_[-1];
}
//===========================================================================
//---------------------------------------------------------------------------
// data access
public:
T* data() noexcept {
return impl_.b_;
}
const T* data() const noexcept {
return impl_.b_;
}
//===========================================================================
//---------------------------------------------------------------------------
// modifiers (common)
public:
template <class... Args>
void emplace_back(Args&&... args) {
if (impl_.e_ != impl_.z_) {
M_construct(impl_.e_, std::forward<Args>(args)...);
++impl_.e_;
} else {
emplace_back_aux(std::forward<Args>(args)...);
}
}
void push_back(const T& value) {
if (impl_.e_ != impl_.z_) {
M_construct(impl_.e_, value);
++impl_.e_;
} else {
emplace_back_aux(value);
}
}
void push_back(T&& value) {
if (impl_.e_ != impl_.z_) {
M_construct(impl_.e_, std::move(value));
++impl_.e_;
} else {
emplace_back_aux(std::move(value));
}
}
void pop_back() {
assert(!empty());
--impl_.e_;
M_destroy(impl_.e_);
}
void swap(fbvector& other) noexcept {
if (!usingStdAllocator::value && A::propagate_on_container_swap::value) {
swap(impl_, other.impl_);
} else {
impl_.swapData(other.impl_);
}
}
void clear() noexcept {
M_destroy_range_e(impl_.b_);
}
private:
// std::vector implements a similar function with a different growth
// strategy: empty() ? 1 : capacity() * 2.
//
// fbvector grows differently on two counts:
//
// (1) initial size
// Instead of growing to size 1 from empty, fbvector allocates at least
// 64 bytes. You may still use reserve to reserve a lesser amount of
// memory.
// (2) 1.5x
// For medium-sized vectors, the growth strategy is 1.5x. See the docs
// for details.
// This does not apply to very small or very large fbvectors. This is a
// heuristic.
// A nice addition to fbvector would be the capability of having a user-
// defined growth strategy, probably as part of the allocator.
//
size_type computePushBackCapacity() const {
if (capacity() == 0) {
return std::max(64 / sizeof(T), size_type(1));
}
if (capacity() < folly::jemallocMinInPlaceExpandable / sizeof(T)) {
return capacity() * 2;
}
if (capacity() > 4096 * 32 / sizeof(T)) {
return capacity() * 2;
}
return (capacity() * 3 + 1) / 2;
}
template <class... Args>
void emplace_back_aux(Args&&... args);
//===========================================================================
//---------------------------------------------------------------------------
// modifiers (erase)
public:
iterator erase(const_iterator position) {
return erase(position, position + 1);
}
iterator erase(const_iterator first, const_iterator last) {
assert(isValid(first) && isValid(last));
assert(first <= last);
if (first != last) {
if (last == end()) {
M_destroy_range_e((iterator)first);
} else {
if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
D_destroy_range_a((iterator)first, (iterator)last);
if (last - first >= cend() - last) {
std::memcpy((void*)first, (void*)last, (cend() - last) * sizeof(T));
} else {
std::memmove((iterator)first, last, (cend() - last) * sizeof(T));
}
impl_.e_ -= (last - first);
} else {
std::copy(
std::make_move_iterator((iterator)last),
std::make_move_iterator(end()),
(iterator)first);
auto newEnd = impl_.e_ - std::distance(first, last);
M_destroy_range_e(newEnd);
}
}
}
return (iterator)first;
}
//===========================================================================
//---------------------------------------------------------------------------
// modifiers (insert)
private: // we have the private section first because it defines some macros
bool isValid(const_iterator it) {
return cbegin() <= it && it <= cend();
}
size_type computeInsertCapacity(size_type n) {
size_type nc = std::max(computePushBackCapacity(), size() + n);
size_type ac = folly::goodMallocSize(nc * sizeof(T)) / sizeof(T);
return ac;
}
//---------------------------------------------------------------------------
//
// make_window takes an fbvector, and creates an uninitialized gap (a
// window) at the given position, of the given size. The fbvector must
// have enough capacity.
//
// Explanation by picture.
//
// 123456789______
// ^
// make_window here of size 3
//
// 1234___56789___
//
// If something goes wrong and the window must be destroyed, use
// undo_window to provide a weak exception guarantee. It destroys
// the right ledge.
//
// 1234___________
//
//---------------------------------------------------------------------------
//
// wrap_frame takes an inverse window and relocates an fbvector around it.
// The fbvector must have at least as many elements as the left ledge.
//
// Explanation by picture.
//
// START
// fbvector: inverse window:
// 123456789______ _____abcde_______
// [idx][ n ]
//
// RESULT
// _______________ 12345abcde6789___
//
//---------------------------------------------------------------------------
//
// insert_use_fresh_memory returns true iff the fbvector should use a fresh
// block of memory for the insertion. If the fbvector does not have enough
// spare capacity, then it must return true. Otherwise either true or false
// may be returned.
//
//---------------------------------------------------------------------------
//
// These three functions, make_window, wrap_frame, and
// insert_use_fresh_memory, can be combined into a uniform interface.
// Since that interface involves a lot of case-work, it is built into
// some macros: FOLLY_FBVECTOR_INSERT_(PRE|START|TRY|END)
// Macros are used in an attempt to let GCC perform better optimizations,
// especially control flow optimization.
//
//---------------------------------------------------------------------------
// window
void make_window(iterator position, size_type n) {
// The result is guaranteed to be non-negative, so use an unsigned type:
size_type tail = size_type(std::distance(position, impl_.e_));
if (tail <= n) {
relocate_move(position + n, position, impl_.e_);
relocate_done(position + n, position, impl_.e_);
impl_.e_ += n;
} else {
if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
std::memmove(position + n, position, tail * sizeof(T));
impl_.e_ += n;
} else {
D_uninitialized_move_a(impl_.e_, impl_.e_ - n, impl_.e_);
try {
std::copy_backward(
std::make_move_iterator(position),
std::make_move_iterator(impl_.e_ - n),
impl_.e_);
} catch (...) {
D_destroy_range_a(impl_.e_ - n, impl_.e_ + n);
impl_.e_ -= n;
throw;
}
impl_.e_ += n;
D_destroy_range_a(position, position + n);
}
}
}
void undo_window(iterator position, size_type n) noexcept {
D_destroy_range_a(position + n, impl_.e_);
impl_.e_ = position;
}
//---------------------------------------------------------------------------
// frame
void wrap_frame(T* ledge, size_type idx, size_type n) {
assert(size() >= idx);
assert(n != 0);
relocate_move(ledge, impl_.b_, impl_.b_ + idx);
try {
relocate_move(ledge + idx + n, impl_.b_ + idx, impl_.e_);
} catch (...) {
relocate_undo(ledge, impl_.b_, impl_.b_ + idx);
throw;
}
relocate_done(ledge, impl_.b_, impl_.b_ + idx);
relocate_done(ledge + idx + n, impl_.b_ + idx, impl_.e_);
}
//---------------------------------------------------------------------------
// use fresh?
bool insert_use_fresh(bool at_end, size_type n) {
if (at_end) {
if (size() + n <= capacity()) {
return false;
}
if (reserve_in_place(size() + n)) {
return false;
}
return true;
}
if (size() + n > capacity()) {
return true;
}
return false;
}
//---------------------------------------------------------------------------
// interface
template <
typename IsInternalFunc,
typename InsertInternalFunc,
typename ConstructFunc,
typename DestroyFunc>
iterator do_real_insert(
const_iterator cpos,
size_type n,
IsInternalFunc&& isInternalFunc,
InsertInternalFunc&& insertInternalFunc,
ConstructFunc&& constructFunc,
DestroyFunc&& destroyFunc) {
if (n == 0) {
return iterator(cpos);
}
bool at_end = cpos == cend();
bool fresh = insert_use_fresh(at_end, n);
if (!at_end) {
if (!fresh && isInternalFunc()) {
// check for internal data (technically not required by the standard)
return insertInternalFunc();
}
assert(isValid(cpos));
}
T* position = const_cast<T*>(cpos);
size_type idx = size_type(std::distance(impl_.b_, position));
T* b;
size_type newCap; /* intentionally uninitialized */
if (fresh) {
newCap = computeInsertCapacity(n);
b = M_allocate(newCap);
} else {
if (!at_end) {
make_window(position, n);
} else {
impl_.e_ += n;
}
b = impl_.b_;
}
T* start = b + idx;
try {
// construct the inserted elements
constructFunc(start);
} catch (...) {
if (fresh) {
M_deallocate(b, newCap);
} else {
if (!at_end) {
undo_window(position, n);
} else {
impl_.e_ -= n;
}
}
throw;
}
if (fresh) {
try {
wrap_frame(b, idx, n);
} catch (...) {
// delete the inserted elements (exception has been thrown)
destroyFunc(start);
M_deallocate(b, newCap);
throw;
}
if (impl_.b_) {
M_deallocate(impl_.b_, capacity());
}
impl_.set(b, size() + n, newCap);
return impl_.b_ + idx;
} else {
return position;
}
}
public:
template <class... Args>
iterator emplace(const_iterator cpos, Args&&... args) {
return do_real_insert(
cpos,
1,
[&] { return false; },
[&] { return iterator{}; },
[&](iterator start) {
M_construct(start, std::forward<Args>(args)...);
},
[&](iterator start) { M_destroy(start); });
}
iterator insert(const_iterator cpos, const T& value) {
return do_real_insert(
cpos,
1,
[&] { return dataIsInternal(value); },
[&] { return insert(cpos, T(value)); },
[&](iterator start) { M_construct(start, value); },
[&](iterator start) { M_destroy(start); });
}
iterator insert(const_iterator cpos, T&& value) {
return do_real_insert(
cpos,
1,
[&] { return dataIsInternal(value); },
[&] { return insert(cpos, T(std::move(value))); },
[&](iterator start) { M_construct(start, std::move(value)); },
[&](iterator start) { M_destroy(start); });
}
iterator insert(const_iterator cpos, size_type n, VT value) {
return do_real_insert(
cpos,
n,
[&] { return dataIsInternalAndNotVT(value); },
[&] { return insert(cpos, n, T(value)); },
[&](iterator start) { D_uninitialized_fill_n_a(start, n, value); },
[&](iterator start) { D_destroy_range_a(start, start + n); });
}
template <
class It,
class Category = typename std::iterator_traits<It>::iterator_category>
iterator insert(const_iterator cpos, It first, It last) {
return insert(cpos, first, last, Category());
}
iterator insert(const_iterator cpos, std::initializer_list<T> il) {
return insert(cpos, il.begin(), il.end());
}
//---------------------------------------------------------------------------
// insert dispatch for iterator types
private:
template <class FIt>
iterator
insert(const_iterator cpos, FIt first, FIt last, std::forward_iterator_tag) {
size_type n = size_type(std::distance(first, last));
return do_real_insert(
cpos,
n,
[&] { return false; },
[&] { return iterator{}; },
[&](iterator start) { D_uninitialized_copy_a(start, first, last); },
[&](iterator start) { D_destroy_range_a(start, start + n); });
}
template <class IIt>
iterator
insert(const_iterator cpos, IIt first, IIt last, std::input_iterator_tag) {
T* position = const_cast<T*>(cpos);
assert(isValid(position));
size_type idx = std::distance(begin(), position);
fbvector storage(
std::make_move_iterator(position),
std::make_move_iterator(end()),
A::select_on_container_copy_construction(impl_));
M_destroy_range_e(position);
for (; first != last; ++first) {
emplace_back(*first);
}
insert(
cend(),
std::make_move_iterator(storage.begin()),
std::make_move_iterator(storage.end()));
return impl_.b_ + idx;
}
//===========================================================================
//---------------------------------------------------------------------------
// lexicographical functions
public:
bool operator==(const fbvector& other) const {
return size() == other.size() && std::equal(begin(), end(), other.begin());
}
bool operator!=(const fbvector& other) const {
return !(*this == other);
}
bool operator<(const fbvector& other) const {
return std::lexicographical_compare(
begin(), end(), other.begin(), other.end());
}
bool operator>(const fbvector& other) const {
return other < *this;
}
bool operator<=(const fbvector& other) const {
return !(*this > other);
}
bool operator>=(const fbvector& other) const {
return !(*this < other);
}
//===========================================================================
//---------------------------------------------------------------------------
// friends
private:
template <class _T, class _A>
friend _T* relinquish(fbvector<_T, _A>&);
template <class _T, class _A>
friend void attach(fbvector<_T, _A>&, _T* data, size_t sz, size_t cap);
}; // class fbvector
//=============================================================================
//-----------------------------------------------------------------------------
// outlined functions (gcc, you finicky compiler you)
template <typename T, typename Allocator>
template <class... Args>
void fbvector<T, Allocator>::emplace_back_aux(Args&&... args) {
size_type byte_sz =
folly::goodMallocSize(computePushBackCapacity() * sizeof(T));
if (usingStdAllocator::value && usingJEMalloc() &&
((impl_.z_ - impl_.b_) * sizeof(T) >=
folly::jemallocMinInPlaceExpandable)) {
// Try to reserve in place.
// Ask xallocx to allocate in place at least size()+1 and at most sz space.
// xallocx will allocate as much as possible within that range, which
// is the best possible outcome: if sz space is available, take it all,
// otherwise take as much as possible. If nothing is available, then fail.
// In this fashion, we never relocate if there is a possibility of
// expanding in place, and we never reallocate by less than the desired
// amount unless we cannot expand further. Hence we will not reallocate
// sub-optimally twice in a row (modulo the blocking memory being freed).
size_type lower = folly::goodMallocSize(sizeof(T) + size() * sizeof(T));
size_type upper = byte_sz;
size_type extra = upper - lower;
void* p = impl_.b_;
size_t actual;
if ((actual = xallocx(p, lower, extra, 0)) >= lower) {
impl_.z_ = impl_.b_ + actual / sizeof(T);
M_construct(impl_.e_, std::forward<Args>(args)...);
++impl_.e_;
return;
}
}
// Reallocation failed. Perform a manual relocation.
size_type sz = byte_sz / sizeof(T);
auto newB = M_allocate(sz);
auto newE = newB + size();
try {
if (folly::IsRelocatable<T>::value && usingStdAllocator::value) {
// For linear memory access, relocate before construction.
// By the test condition, relocate is noexcept.
// Note that there is no cleanup to do if M_construct throws - that's
// one of the beauties of relocation.
// Benchmarks for this code have high variance, and seem to be close.
relocate_move(newB, impl_.b_, impl_.e_);
M_construct(newE, std::forward<Args>(args)...);
++newE;
} else {
M_construct(newE, std::forward<Args>(args)...);
++newE;
try {
M_relocate(newB);
} catch (...) {
M_destroy(newE - 1);
throw;
}
}
} catch (...) {
M_deallocate(newB, sz);
throw;
}
if (impl_.b_) {
M_deallocate(impl_.b_, size());
}
impl_.b_ = newB;
impl_.e_ = newE;
impl_.z_ = newB + sz;
}
//=============================================================================
//-----------------------------------------------------------------------------
// specialized functions
template <class T, class A>
void swap(fbvector<T, A>& lhs, fbvector<T, A>& rhs) noexcept {
lhs.swap(rhs);
}
//=============================================================================
//-----------------------------------------------------------------------------
// other
namespace detail {
// Format support.
template <class T, class A>
struct IndexableTraits<fbvector<T, A>>
: public IndexableTraitsSeq<fbvector<T, A>> {};
} // namespace detail
template <class T, class A>
void compactResize(fbvector<T, A>* v, size_t sz) {
v->resize(sz);
v->shrink_to_fit();
}
// DANGER
//
// relinquish and attach are not a members function specifically so that it is
// awkward to call them. It is very easy to shoot yourself in the foot with
// these functions.
//
// If you call relinquish, then it is your responsibility to free the data
// and the storage, both of which may have been generated in a non-standard
// way through the fbvector's allocator.
//
// If you call attach, it is your responsibility to ensure that the fbvector
// is fresh (size and capacity both zero), and that the supplied data is
// capable of being manipulated by the allocator.
// It is acceptable to supply a stack pointer IF:
// (1) The vector's data does not outlive the stack pointer. This includes
// extension of the data's life through a move operation.
// (2) The pointer has enough capacity that the vector will never be
// relocated.
// (3) Insert is not called on the vector; these functions have leeway to
// relocate the vector even if there is enough capacity.
// (4) A stack pointer is compatible with the fbvector's allocator.
//
template <class T, class A>
T* relinquish(fbvector<T, A>& v) {
T* ret = v.data();
v.impl_.b_ = v.impl_.e_ = v.impl_.z_ = nullptr;
return ret;
}
template <class T, class A>
void attach(fbvector<T, A>& v, T* data, size_t sz, size_t cap) {
assert(v.data() == nullptr);
v.impl_.b_ = data;
v.impl_.e_ = data + sz;
v.impl_.z_ = data + cap;
}
} // namespace folly