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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "alloc.h"
#include "traits.h"
#include "arrayref.h"
#include <cstring>
#include <cassert>
#include <iterator>
namespace vespalib {
namespace small_vector {
template <typename T>
constexpr size_t select_N() {
if constexpr (sizeof(T) <= 16) {
return (48 / sizeof(T));
} else {
static_assert(sizeof(T) <= 16,
"auto-selecting N is only supported for small objects (16 bytes or less)");
return 1;
}
}
template <typename T, typename... Args>
void create_at(T *ptr, Args &&...args) {
// https://en.cppreference.com/w/cpp/memory/construct_at
::new (const_cast<void*>(static_cast<const volatile void*>(ptr))) T(std::forward<Args>(args)...);
}
template <typename T>
void move_objects(T *dst, T *src, uint32_t n) {
if constexpr (std::is_trivially_copyable_v<T>) {
// need to cast dst to void to avoid compiler warning caused by some trivially copyable objects not being copy assignable.
memcpy(static_cast<void *>(dst), src, n * sizeof(T));
} else {
for (size_t i = 0; i < n; ++i) {
create_at(dst + i, std::move(src[i]));
}
}
}
template <typename T>
void copy_objects(T *dst, const T *src, uint32_t n) {
if constexpr (std::is_trivially_copyable_v<T>) {
memcpy(dst, src, n * sizeof(T));
} else {
for (size_t i = 0; i < n; ++i) {
create_at(dst + i, src[i]);
}
}
}
template <typename T, typename... Args>
void create_objects(T *dst, uint32_t n, Args &&...args) {
for (size_t i = 0; i < n; ++i) {
create_at(dst + i, std::forward<Args>(args)...);
}
}
template <typename T>
void destroy_objects(T *src, uint32_t n) {
if (!can_skip_destruction<T>) {
std::destroy_n(src, n);
}
}
template <typename T>
std::pair<T*,size_t> alloc_objects(size_t wanted) {
size_t mem = roundUp2inN(wanted * sizeof(T));
size_t entries = (mem / sizeof(T));
mem = (entries * sizeof(T));
T *ptr = static_cast<T*>(malloc(mem));
assert(ptr != nullptr);
return {ptr, entries};
}
} // namespace small_vector
/**
* Simplified vector-like container that has space for some elements
* inside the object itself. Intended use is to contain lists of
* simple objects/values that are small in both size and number.
**/
template <typename T, size_t N = small_vector::select_N<T>()>
class SmallVector
{
private:
T *_data;
uint32_t _size;
uint32_t _capacity;
alignas(T) char _space[sizeof(T) * N];
constexpr T *local() noexcept { return reinterpret_cast<T*>(_space); }
constexpr const T *local() const noexcept { return reinterpret_cast<const T*>(_space); }
void expand(size_t wanted) {
auto [new_data, new_capacity] = small_vector::alloc_objects<T>(wanted);
small_vector::move_objects(new_data, _data, _size);
small_vector::destroy_objects(_data, _size);
auto old_data = _data;
_data = new_data;
_capacity = new_capacity;
if (old_data != local()) {
free(old_data);
}
}
template <std::random_access_iterator InputIt>
void init(InputIt first, InputIt last) {
reserve(last - first);
while (first != last) {
small_vector::create_at((_data + _size++), *first++);
}
}
template <std::input_iterator InputIt>
void init(InputIt first, InputIt last) {
while (first != last) {
emplace_back(*first++);
}
}
public:
constexpr SmallVector() noexcept : _data(local()), _size(0), _capacity(N) {
static_assert(N > 0);
}
SmallVector(size_t n) : SmallVector() {
reserve(n);
small_vector::create_objects(_data, n);
_size = n;
}
SmallVector(size_t n, const T &obj) : SmallVector() {
reserve(n);
small_vector::create_objects(_data, n, obj);
_size = n;
}
SmallVector(std::initializer_list<T> list) : SmallVector() {
reserve(list.size());
for (const T &value: list) {
small_vector::create_at((_data + _size++), value);
}
}
template <std::input_iterator InputIt>
SmallVector(InputIt first, InputIt last) : SmallVector()
{
init(first, last);
}
SmallVector(SmallVector &&rhs) : SmallVector() {
reserve(rhs._size);
small_vector::move_objects(_data, rhs._data, rhs._size);
_size = rhs._size;
}
SmallVector(const SmallVector &rhs) : SmallVector() {
reserve(rhs._size);
small_vector::copy_objects(_data, rhs._data, rhs._size);
_size = rhs._size;
}
SmallVector &operator=(SmallVector &&rhs) {
assert(std::addressof(rhs) != this);
clear();
reserve(rhs._size);
small_vector::move_objects(_data, rhs._data, rhs._size);
_size = rhs._size;
return *this;
}
SmallVector &operator=(const SmallVector &rhs) {
assert(std::addressof(rhs) != this);
clear();
reserve(rhs._size);
small_vector::copy_objects(_data, rhs._data, rhs._size);
_size = rhs._size;
return *this;
}
~SmallVector() {
small_vector::destroy_objects(_data, _size);
if (_data != local()) {
free(_data);
}
}
operator ConstArrayRef<T> () const { return ConstArrayRef<T>(data(), size()); }
bool empty() const noexcept { return (_size == 0); }
uint32_t size() const noexcept { return _size; }
uint32_t capacity() const noexcept { return _capacity; }
bool is_local() const noexcept { return (_data == local()); }
T *begin() noexcept { return _data; }
T *end() noexcept { return (_data + _size); }
const T *begin() const noexcept { return _data; }
const T *end() const noexcept { return (_data + _size); }
T &operator[](size_t idx) noexcept { return _data[idx]; }
const T &operator[](size_t idx) const noexcept { return _data[idx]; }
T *data() noexcept { return _data; }
const T *data() const noexcept { return _data; }
T &back() noexcept { return _data[_size - 1]; }
const T &back() const noexcept { return _data[_size - 1]; }
void clear() noexcept {
small_vector::destroy_objects(_data, _size);
_size = 0;
}
void reserve(size_t wanted) {
if (__builtin_expect(wanted > _capacity, false)) {
expand(wanted);
}
}
template <typename... Args>
void emplace_back(Args &&...args) {
reserve(_size + 1);
small_vector::create_at((_data + _size), std::forward<Args>(args)...);
++_size;
}
template <typename... Args>
SmallVector &add(Args &&...args) {
emplace_back(std::forward<Args>(args)...);
return *this;
}
void push_back(const T &obj) { emplace_back(obj); }
void push_back(T &&obj) { emplace_back(std::move(obj)); }
void pop_back() { small_vector::destroy_objects(_data + --_size, 1); }
};
template <typename T, size_t N, size_t M>
bool operator==(const SmallVector<T,N> &a,
const SmallVector<T,M> &b) noexcept
{
if (a.size() != b.size()) {
return false;
}
for (size_t i = 0; i < a.size(); ++i) {
if (!(a[i] == b[i])) {
return false;
}
}
return true;
}
} // namespace
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