bkietz commented on a change in pull request #10915: URL: https://github.com/apache/arrow/pull/10915#discussion_r689946268
########## File path: cpp/src/arrow/util/small_vector.h ########## @@ -0,0 +1,509 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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. + +#pragma once + +#include <algorithm> +#include <cassert> +#include <cstddef> +#include <initializer_list> +#include <limits> +#include <new> +#include <type_traits> +#include <utility> + +#include "arrow/util/macros.h" + +namespace arrow { +namespace internal { + +#if __cplusplus >= 201703L +using std::launder; +#else +// TODO factor out from result.h + +// template <class T> +// constexpr T* launder(T* p) noexcept { +// return p; +// } +#endif + +template <typename ValueType, typename PointerType, typename ReferenceType> +class VectorIterator { + public: + using value_type = ValueType; + using pointer = PointerType; + using reference = ReferenceType; + using difference_type = ptrdiff_t; + using iterator_category = std::random_access_iterator_tag; + + // Some algorithms need to default-construct an iterator + constexpr VectorIterator() noexcept = default; + + constexpr explicit VectorIterator(pointer ptr) noexcept : ptr_(ptr) {} + + // Value access + constexpr reference operator*() const { return *ptr_; } + + constexpr reference operator[](difference_type n) const { return ptr_[n]; } + + // Forward / backward + VectorIterator& operator++() { + ++ptr_; + return *this; + } + VectorIterator& operator--() { + --ptr_; + return *this; + } + VectorIterator operator++(int) { + VectorIterator tmp(*this); + ++ptr_; + return tmp; + } + VectorIterator operator--(int) { + VectorIterator tmp(*this); + --ptr_; + return tmp; + } + + // Arithmetic + constexpr difference_type operator-(const VectorIterator& other) const { + return ptr_ - other.ptr_; + } + constexpr VectorIterator operator+(difference_type n) const { + return VectorIterator(ptr_ + n); + } + constexpr VectorIterator operator-(difference_type n) const { + return VectorIterator(ptr_ - n); + } + VectorIterator& operator+=(difference_type n) { + ptr_ += n; + return *this; + } + VectorIterator& operator-=(difference_type n) { + ptr_ -= n; + return *this; + } + + // Comparisons + constexpr bool operator==(const VectorIterator& other) const { + return ptr_ == other.ptr_; + } + constexpr bool operator!=(const VectorIterator& other) const { + return ptr_ != other.ptr_; + } + constexpr bool operator<(const VectorIterator& other) const { + return ptr_ < other.ptr_; + } + constexpr bool operator>(const VectorIterator& other) const { + return ptr_ > other.ptr_; + } + constexpr bool operator<=(const VectorIterator& other) const { + return ptr_ <= other.ptr_; + } + constexpr bool operator>=(const VectorIterator& other) const { + return ptr_ >= other.ptr_; + } + + private: + pointer ptr_ = NULLPTR; +}; + +template <typename T> +class StaticVectorMixin { + protected: + // properly aligned uninitialized storage for N T's + using storage_type = typename std::aligned_storage<sizeof(T), alignof(T)>::type; + + static T* ptr_at(storage_type* p, size_t i) { + return launder(reinterpret_cast<T*>(&p[i])); + } + + static const T* ptr_at(const storage_type* p, size_t i) { + return launder(reinterpret_cast<const T*>(&p[i])); + } + + static void move_storage(storage_type* src, storage_type* dest, size_t n) { + for (size_t i = 0; i < n; ++i) { + T* src_item = ptr_at(src, i); + T* dest_item = ptr_at(dest, i); + new (dest_item) T(std::move(*src_item)); + src_item->~T(); + } + } + + static void destroy_storage(storage_type* p, size_t n) { + for (size_t i = 0; i < n; ++i) { + ptr_at(p, i)->~T(); + } + } +}; + +template <typename T, size_t N, bool NonTrivialDestructor> +class StaticVectorBaseStorage : public StaticVectorMixin<T> { Review comment: I would like to see this use composition instead. Honestly, I think in this case since there are only two classes it'd be better to keep the two unrelated and repeat implementations (modulo calls to the helper trait). I can make a meta-PR to your branch tomorrow with a more thorough sketch if you'd prefer ########## File path: cpp/src/arrow/util/small_vector.h ########## @@ -0,0 +1,427 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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. + +#pragma once + +#include <algorithm> +#include <cassert> +#include <cstddef> +#include <initializer_list> +#include <limits> +#include <new> +#include <type_traits> +#include <utility> + +#include "arrow/util/macros.h" + +namespace arrow { +namespace internal { + +#if __cplusplus >= 201703L +using std::launder; +#else +// TODO factor out from result.h Review comment: agreed, this should be a tiny header like `util/unreachable.h` ########## File path: cpp/src/arrow/util/small_vector.h ########## @@ -0,0 +1,427 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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. + +#pragma once + +#include <algorithm> +#include <cassert> +#include <cstddef> +#include <initializer_list> +#include <limits> +#include <new> +#include <type_traits> +#include <utility> + +#include "arrow/util/macros.h" + +namespace arrow { +namespace internal { + +#if __cplusplus >= 201703L +using std::launder; +#else +// TODO factor out from result.h + +// template <class T> +// constexpr T* launder(T* p) noexcept { +// return p; +// } +#endif + +template <typename T> +class StaticVectorMixin { + protected: + // properly aligned uninitialized storage for N T's + using storage_type = typename std::aligned_storage<sizeof(T), alignof(T)>::type; + + static T* ptr_at(storage_type* p, size_t i) { + return launder(reinterpret_cast<T*>(&p[i])); + } + + static const T* ptr_at(const storage_type* p, size_t i) { + return launder(reinterpret_cast<const T*>(&p[i])); + } + + static void move_storage(storage_type* src, storage_type* dest, size_t n) { + for (size_t i = 0; i < n; ++i) { + T* src_item = ptr_at(src, i); + T* dest_item = ptr_at(dest, i); + new (dest_item) T(std::move(*src_item)); + src_item->~T(); + } + } + + static void destroy_storage(storage_type* p, size_t n) { + for (size_t i = 0; i < n; ++i) { + ptr_at(p, i)->~T(); + } + } +}; + +template <typename T, size_t N, bool NonTrivialDestructor> +class StaticVectorBaseStorage : public StaticVectorMixin<T> { + protected: + using typename StaticVectorMixin<T>::storage_type; + + storage_type static_data_[N]; + size_t size_ = 0; + + void destroy() {} +}; + +template <typename T, size_t N> +class StaticVectorBaseStorage<T, N, true> : public StaticVectorMixin<T> { + protected: + using typename StaticVectorMixin<T>::storage_type; + + storage_type static_data_[N]; + size_t size_ = 0; + + ~StaticVectorBaseStorage() noexcept { destroy(); } + + void destroy() noexcept { this->destroy_storage(static_data_, size_); } +}; + +template <typename T, size_t N, bool D = !std::is_trivially_destructible<T>::value> +class StaticVectorBase : public StaticVectorBaseStorage<T, N, D> { + protected: + using Base = StaticVectorBaseStorage<T, N, D>; + using typename Base::storage_type; + + using Base::size_; + using Base::static_data_; + + StaticVectorBase() noexcept = default; + + storage_type* data_ptr() { return static_data_; } + + constexpr const storage_type* const_data_ptr() const { return static_data_; } + + void bump_size(size_t addend) { + assert(size_ + addend <= N); + size_ += addend; + } + + void reduce_size(size_t reduce_by) { + assert(reduce_by <= size_); + size_ -= reduce_by; + } + + void move_from(StaticVectorBase&& other) noexcept { + size_ = other.size_; + this->move_storage(other.static_data_, static_data_, size_); + other.size_ = 0; + } + + public: + constexpr size_t capacity() const { return N; } + + constexpr size_t max_size() const { return N; } + + void reserve(size_t n) {} + + void clear() { + this->destroy_storage(static_data_, size_); + size_ = 0; + } +}; + +template <typename T, size_t N> +class SmallVectorBase : public StaticVectorMixin<T> { + protected: + using typename StaticVectorMixin<T>::storage_type; + + storage_type static_data_[N]; + size_t size_ = 0; + storage_type* data_ = static_data_; + size_t dynamic_capacity_ = 0; + + SmallVectorBase() noexcept = default; + + ~SmallVectorBase() { destroy(); } + + storage_type* data_ptr() { return data_; } + + constexpr const storage_type* const_data_ptr() const { return data_; } + + void bump_size(size_t addend) { + size_t new_size = size_ + addend; + if (dynamic_capacity_) { + // Grow dynamic storage if necessary + if (new_size > dynamic_capacity_) { + size_t new_capacity = std::max(dynamic_capacity_ * 3 / 2, new_size); + auto new_data = new storage_type[new_capacity]; + this->move_storage(data_, new_data, size_); + delete[] data_; + dynamic_capacity_ = new_capacity; + data_ = new_data; + } + } else if (new_size > N) { + switch_to_dynamic(new_size); + } + size_ = new_size; + } + + void reduce_size(size_t reduce_by) { + assert(reduce_by <= size_); + size_ -= reduce_by; + } + + void destroy() { + this->destroy_storage(data_, size_); + if (dynamic_capacity_) { + delete[] data_; + } + } + + void move_from(SmallVectorBase&& other) noexcept { + size_ = other.size_; + dynamic_capacity_ = other.dynamic_capacity_; + if (dynamic_capacity_) { + data_ = other.data_; + other.data_ = NULLPTR; + other.dynamic_capacity_ = 0; + } else { + this->move_storage(other.data_, data_, size_); + } + other.size_ = 0; + } + + public: + constexpr size_t capacity() const { return dynamic_capacity_ ? dynamic_capacity_ : N; } + + constexpr size_t max_size() const { return std::numeric_limits<size_t>::max(); } + + void reserve(size_t n) { + if (dynamic_capacity_) { + if (n > dynamic_capacity_) { + reallocate_dynamic(n); + } + } else if (n > N) { + switch_to_dynamic(n); + } + } + + void clear() { + this->destroy_storage(data_, size_); + size_ = 0; + } + + private: + void switch_to_dynamic(size_t new_capacity) { + dynamic_capacity_ = new_capacity; + data_ = new storage_type[new_capacity]; + this->move_storage(static_data_, data_, size_); + } + + void reallocate_dynamic(size_t new_capacity) { + assert(new_capacity >= size_); + auto new_data = new storage_type[new_capacity]; + this->move_storage(data_, new_data, size_); + delete[] data_; + dynamic_capacity_ = new_capacity; + data_ = new_data; + } +}; + +template <typename T, size_t N, typename Base> +class StaticVectorImpl : public Base { + private: + using Base::size_; + + T* item_ptr(size_t i) { return this->ptr_at(this->data_ptr(), i); } + + constexpr const T* const_item_ptr(size_t i) const { + return this->ptr_at(this->const_data_ptr(), i); + } + + public: + using size_type = size_t; + using difference_type = ptrdiff_t; + using value_type = T; + using pointer = T*; + using const_pointer = const T*; + using reference = T&; + using const_reference = const T&; + using iterator = T*; + using const_iterator = const T*; + + constexpr StaticVectorImpl() noexcept = default; + + StaticVectorImpl(StaticVectorImpl&& other) noexcept { + this->move_from(std::move(other)); + } + + StaticVectorImpl& operator=(StaticVectorImpl&& other) noexcept { + if (&other != this) { + this->destroy(); + this->move_from(std::move(other)); + } + return *this; + } + + StaticVectorImpl(const StaticVectorImpl& other) { + const size_t n = other.size_; + this->bump_size(n); + auto* src = other.const_item_ptr(0); + auto* dest = this->item_ptr(0); + for (size_t i = 0; i < n; ++i) { + new (&dest[i]) T(src[i]); + } + } + + StaticVectorImpl& operator=(const StaticVectorImpl& other) noexcept { + if (&other == this) { + return *this; + } + const size_t n = other.size_; + const size_t old_size = size_; + auto* src = other.const_item_ptr(0); + if (n > old_size) { + this->bump_size(n); + auto* dest = this->item_ptr(0); + for (size_t i = 0; i < old_size; ++i) { + dest[i] = src[i]; + } + for (size_t i = old_size; i < n; ++i) { + new (&dest[i]) T(src[i]); + } + } else { + auto* dest = this->item_ptr(0); + for (size_t i = 0; i < n; ++i) { + dest[i] = src[i]; + } + for (size_t i = n; i < old_size; ++i) { + dest[i].~T(); + } + this->reduce_size(n); + } + return *this; + } + + explicit StaticVectorImpl(size_t count) { + this->bump_size(count); + auto* p = this->item_ptr(0); + for (size_t i = 0; i < count; ++i) { + new (&p[i]) T(); + } + } + + StaticVectorImpl(size_t count, const T& value) { + this->bump_size(count); + auto* p = this->item_ptr(0); + for (size_t i = 0; i < count; ++i) { + new (&p[i]) T(value); + } + } + Review comment: I think for usability we'd also want (possibly implicit) construction and assignment from `std::vector`. I think this would make replacement of `ArrayData::buffers` less painful -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
