FTL: Add SmallVector<T, N> (0bacf27f) · Commits · e / os / platform_frameworks_native

include/ftl/ArrayTraits.h

0 → 100644

+129 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright 2020 The Android Open Source Project
		*
		* 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.
		*/

		#pragma once

		#include <algorithm>
		#include <iterator>
		#include <new>

		#define FTL_ARRAY_TRAIT(T, U) using U = typename ArrayTraits<T>::U

		namespace android::ftl {

		template <typename T>
		struct ArrayTraits {
		using value_type = T;
		using size_type = size_t;
		using difference_type = ptrdiff_t;

		using pointer = value_type*;
		using reference = value_type&;
		using iterator = pointer;
		using reverse_iterator = std::reverse_iterator<iterator>;

		using const_pointer = const value_type*;
		using const_reference = const value_type&;
		using const_iterator = const_pointer;
		using const_reverse_iterator = std::reverse_iterator<const_iterator>;

		// TODO: Replace with std::construct_at in C++20.
		template <typename... Args>
		static pointer construct_at(const_iterator it, Args&&... args) {
		void* const ptr = const_cast<void>(static_cast<const void>(it));
		return new (ptr) value_type{std::forward<Args>(args)...};
		}
		};

		// CRTP mixin to define iterator functions in terms of non-const Self::begin and Self::end.
		template <typename Self, typename T>
		class ArrayIterators {
		FTL_ARRAY_TRAIT(T, size_type);

		FTL_ARRAY_TRAIT(T, reference);
		FTL_ARRAY_TRAIT(T, iterator);
		FTL_ARRAY_TRAIT(T, reverse_iterator);

		FTL_ARRAY_TRAIT(T, const_reference);
		FTL_ARRAY_TRAIT(T, const_iterator);
		FTL_ARRAY_TRAIT(T, const_reverse_iterator);

		Self& self() const { return const_cast<Self>(static_cast<const Self*>(this)); }

		public:
		const_iterator begin() const { return cbegin(); }
		const_iterator cbegin() const { return self().begin(); }

		const_iterator end() const { return cend(); }
		const_iterator cend() const { return self().end(); }

		reverse_iterator rbegin() { return std::make_reverse_iterator(self().end()); }
		const_reverse_iterator rbegin() const { return crbegin(); }
		const_reverse_iterator crbegin() const { return self().rbegin(); }

		reverse_iterator rend() { return std::make_reverse_iterator(self().begin()); }
		const_reverse_iterator rend() const { return crend(); }
		const_reverse_iterator crend() const { return self().rend(); }

		iterator last() { return self().end() - 1; }
		const_iterator last() const { return self().last(); }

		reference front() { return *self().begin(); }
		const_reference front() const { return self().front(); }

		reference back() { return *last(); }
		const_reference back() const { return self().back(); }

		reference operator[](size_type i) { return *(self().begin() + i); }
		const_reference operator[](size_type i) const { return self()[i]; }
		};

		// Mixin to define comparison operators for an array-like template.
		// TODO: Replace with operator<=> in C++20.
		template <template <typename, size_t> class Array>
		struct ArrayComparators {
		template <typename T, size_t N, size_t M>
		friend bool operator==(const Array<T, N>& lhs, const Array<T, M>& rhs) {
		return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
		}

		template <typename T, size_t N, size_t M>
		friend bool operator<(const Array<T, N>& lhs, const Array<T, M>& rhs) {
		return std::lexicographical_compare(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
		}

		template <typename T, size_t N, size_t M>
		friend bool operator>(const Array<T, N>& lhs, const Array<T, M>& rhs) {
		return rhs < lhs;
		}

		template <typename T, size_t N, size_t M>
		friend bool operator!=(const Array<T, N>& lhs, const Array<T, M>& rhs) {
		return !(lhs == rhs);
		}

		template <typename T, size_t N, size_t M>
		friend bool operator>=(const Array<T, N>& lhs, const Array<T, M>& rhs) {
		return !(lhs < rhs);
		}

		template <typename T, size_t N, size_t M>
		friend bool operator<=(const Array<T, N>& lhs, const Array<T, M>& rhs) {
		return !(lhs > rhs);
		}
		};

		} // namespace android::ftl

include/ftl/SmallVector.h

0 → 100644

+381 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright 2020 The Android Open Source Project
		*
		* 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.
		*/

		#pragma once

		#include <ftl/ArrayTraits.h>
		#include <ftl/StaticVector.h>

		#include <algorithm>
		#include <iterator>
		#include <type_traits>
		#include <utility>
		#include <variant>
		#include <vector>

		namespace android::ftl {

		template <typename>
		struct IsSmallVector;

		// ftl::StaticVector that promotes to std::vector when full. SmallVector is a drop-in replacement
		// for std::vector with statically allocated storage for N elements, whose goal is to improve run
		// time by avoiding heap allocation and increasing probability of cache hits. The standard API is
		// augmented by an unstable_erase operation that does not preserve order, and a replace operation
		// that destructively emplaces.
		//
		// SmallVector<T, 0> is a specialization that thinly wraps std::vector.
		//
		// Example usage:
		//
		// ftl::SmallVector<char, 3> vector;
		// assert(vector.empty());
		// assert(!vector.dynamic());
		//
		// vector = {'a', 'b', 'c'};
		// assert(vector.size() == 3u);
		// assert(!vector.dynamic());
		//
		// vector.push_back('d');
		// assert(vector.dynamic());
		//
		// vector.unstable_erase(vector.begin());
		// assert(vector == (ftl::SmallVector{'d', 'b', 'c'}));
		//
		// vector.pop_back();
		// assert(vector.back() == 'b');
		// assert(vector.dynamic());
		//
		// const char array[] = "hi";
		// vector = ftl::SmallVector(array);
		// assert(vector == (ftl::SmallVector{'h', 'i', '\0'}));
		// assert(!vector.dynamic());
		//
		template <typename T, size_t N>
		class SmallVector final : ArrayTraits<T>, ArrayComparators<SmallVector> {
		using Static = StaticVector<T, N>;
		using Dynamic = SmallVector<T, 0>;

		// TODO: Replace with std::remove_cvref_t in C++20.
		template <typename U>
		using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<U>>;

		public:
		FTL_ARRAY_TRAIT(T, value_type);
		FTL_ARRAY_TRAIT(T, size_type);
		FTL_ARRAY_TRAIT(T, difference_type);

		FTL_ARRAY_TRAIT(T, pointer);
		FTL_ARRAY_TRAIT(T, reference);
		FTL_ARRAY_TRAIT(T, iterator);
		FTL_ARRAY_TRAIT(T, reverse_iterator);

		FTL_ARRAY_TRAIT(T, const_pointer);
		FTL_ARRAY_TRAIT(T, const_reference);
		FTL_ARRAY_TRAIT(T, const_iterator);
		FTL_ARRAY_TRAIT(T, const_reverse_iterator);

		// Creates an empty vector.
		SmallVector() = default;

		// Constructs at most N elements. See StaticVector for underlying constructors.
		template <typename Arg, typename... Args,
		typename = std::enable_if_t<!IsSmallVector<remove_cvref_t<Arg>>{}>>
		SmallVector(Arg&& arg, Args&&... args)
		: mVector(std::in_place_type<Static>, std::forward<Arg>(arg),
		std::forward<Args>(args)...) {}

		// Copies at most N elements from a smaller convertible vector.
		template <typename U, size_t M, typename = std::enable_if_t<M <= N>>
		SmallVector(const SmallVector<U, M>& other)
		: SmallVector(IteratorRange, other.begin(), other.end()) {}

		void swap(SmallVector& other) { mVector.swap(other.mVector); }

		// Returns whether the vector is backed by static or dynamic storage.
		bool dynamic() const { return std::holds_alternative<Dynamic>(mVector); }

		#define VISITOR(T, F, ...) \
		T F() __VA_ARGS__ { \
		return std::visit([](auto&& v) -> T { return v.F(); }, mVector); \
		}

		VISITOR(size_type, max_size, const)
		VISITOR(size_type, size, const)
		VISITOR(bool, empty, const)

		// noexcept to suppress warning about zero variadic macro arguments.
		VISITOR(iterator, begin, noexcept)
		VISITOR(const_iterator, begin, const)
		VISITOR(const_iterator, cbegin, const)

		VISITOR(iterator, end, noexcept)
		VISITOR(const_iterator, end, const)
		VISITOR(const_iterator, cend, const)

		VISITOR(reverse_iterator, rbegin, noexcept)
		VISITOR(const_reverse_iterator, rbegin, const)
		VISITOR(const_reverse_iterator, crbegin, const)

		VISITOR(reverse_iterator, rend, noexcept)
		VISITOR(const_reverse_iterator, rend, const)
		VISITOR(const_reverse_iterator, crend, const)

		VISITOR(iterator, last, noexcept)
		VISITOR(const_iterator, last, const)

		VISITOR(reference, front, noexcept)
		VISITOR(const_reference, front, const)

		VISITOR(reference, back, noexcept)
		VISITOR(const_reference, back, const)

		#undef VISITOR

		reference operator[](size_type i) {
		return std::visit([i](auto& v) -> reference { return v[i]; }, mVector);
		}

		const_reference operator[](size_type i) const {
		return std::visit([i](const auto& v) -> const_reference { return v[i]; }, mVector);
		}

		// Replaces an element, and returns a reference to it. The iterator must be dereferenceable, so
		// replacing at end() is erroneous.
		//
		// The element is emplaced via move constructor, so type T does not need to define copy/move
		// assignment, e.g. its data members may be const.
		//
		// The arguments may directly or indirectly refer to the element being replaced.
		//
		// Iterators to the replaced element point to its replacement, and others remain valid.
		//
		template <typename... Args>
		reference replace(const_iterator it, Args&&... args) {
		return std::
		visit([it, &args...](auto& v)
		-> reference { return v.replace(it, std::forward<Args>(args)...); },
		mVector);
		}

		// Appends an element, and returns a reference to it.
		//
		// If the vector reaches its static or dynamic capacity, then all iterators are invalidated.
		// Otherwise, only the end() iterator is invalidated.
		//
		template <typename... Args>
		reference emplace_back(Args&&... args) {
		constexpr auto insertStatic = &Static::template emplace_back<Args...>;
		constexpr auto insertDynamic = &Dynamic::template emplace_back<Args...>;
		return *insert<insertStatic, insertDynamic>(std::forward<Args>(args)...);
		}

		// Appends an element.
		//
		// If the vector reaches its static or dynamic capacity, then all iterators are invalidated.
		// Otherwise, only the end() iterator is invalidated.
		//
		void push_back(const value_type& v) {
		constexpr auto insertStatic =
		static_cast<bool (Static::*)(const value_type&)>(&Static::push_back);
		constexpr auto insertDynamic =
		static_cast<bool (Dynamic::*)(const value_type&)>(&Dynamic::push_back);
		insert<insertStatic, insertDynamic>(v);
		}

		void push_back(value_type&& v) {
		constexpr auto insertStatic =
		static_cast<bool (Static::*)(value_type&&)>(&Static::push_back);
		constexpr auto insertDynamic =
		static_cast<bool (Dynamic::*)(value_type&&)>(&Dynamic::push_back);
		insert<insertStatic, insertDynamic>(std::move(v));
		}

		// Removes the last element. The vector must not be empty, or the call is erroneous.
		//
		// The last() and end() iterators are invalidated.
		//
		void pop_back() {
		std::visit([](auto& v) { v.pop_back(); }, mVector);
		}

		// Erases an element, but does not preserve order. Rather than shifting subsequent elements,
		// this moves the last element to the slot of the erased element.
		//
		// The last() and end() iterators, as well as those to the erased element, are invalidated.
		//
		void unstable_erase(iterator it) {
		std::visit([it](auto& v) { v.unstable_erase(it); }, mVector);
		}

		private:
		template <typename... Vs>
		struct Visitor : Vs... {};

		// TODO: Remove this deduction guide in C++20.
		template <typename... Vs>
		Visitor(Vs...) -> Visitor<Vs...>;

		template <auto insertStatic, auto insertDynamic, typename... Args>
		auto insert(Args&&... args) {
		return std::visit(Visitor{[this, &args...](Static& vector) {
		if (vector.full()) {
		return (promote(vector).*
		insertDynamic)(std::forward<Args>(args)...);
		}

		return (vector.*insertStatic)(std::forward<Args>(args)...);
		},
		[&args...](Dynamic& vector) {
		return (vector.*insertDynamic)(std::forward<Args>(args)...);
		}},
		mVector);
		}

		Dynamic& promote(Static& staticVector) {
		assert(staticVector.full());

		// Allocate double capacity to reduce probability of reallocation.
		Dynamic vector;
		vector.reserve(Static::max_size() * 2);
		std::move(staticVector.begin(), staticVector.end(), std::back_inserter(vector));

		return mVector.template emplace<Dynamic>(std::move(vector));
		}

		std::variant<Static, Dynamic> mVector;
		};

		// Partial specialization without static storage.
		template <typename T>
		class SmallVector<T, 0> final : ArrayTraits<T>,
		ArrayIterators<SmallVector<T, 0>, T>,
		std::vector<T> {
		using ArrayTraits<T>::construct_at;

		using Iter = ArrayIterators<SmallVector, T>;
		using Impl = std::vector<T>;

		friend Iter;

		public:
		FTL_ARRAY_TRAIT(T, value_type);
		FTL_ARRAY_TRAIT(T, size_type);
		FTL_ARRAY_TRAIT(T, difference_type);

		FTL_ARRAY_TRAIT(T, pointer);
		FTL_ARRAY_TRAIT(T, reference);
		FTL_ARRAY_TRAIT(T, iterator);
		FTL_ARRAY_TRAIT(T, reverse_iterator);

		FTL_ARRAY_TRAIT(T, const_pointer);
		FTL_ARRAY_TRAIT(T, const_reference);
		FTL_ARRAY_TRAIT(T, const_iterator);
		FTL_ARRAY_TRAIT(T, const_reverse_iterator);

		using Impl::Impl;

		using Impl::empty;
		using Impl::max_size;
		using Impl::size;

		using Impl::reserve;

		// std::vector iterators are not necessarily raw pointers.
		iterator begin() { return Impl::data(); }
		iterator end() { return Impl::data() + size(); }

		using Iter::begin;
		using Iter::end;

		using Iter::cbegin;
		using Iter::cend;

		using Iter::rbegin;
		using Iter::rend;

		using Iter::crbegin;
		using Iter::crend;

		using Iter::last;

		using Iter::back;
		using Iter::front;

		using Iter::operator[];

		template <typename... Args>
		reference replace(const_iterator it, Args&&... args) {
		value_type element{std::forward<Args>(args)...};
		std::destroy_at(it);
		// This is only safe because exceptions are disabled.
		return *construct_at(it, std::move(element));
		}

		template <typename... Args>
		iterator emplace_back(Args&&... args) {
		return &Impl::emplace_back(std::forward<Args>(args)...);
		}

		bool push_back(const value_type& v) {
		Impl::push_back(v);
		return true;
		}

		bool push_back(value_type&& v) {
		Impl::push_back(std::move(v));
		return true;
		}

		using Impl::pop_back;

		void unstable_erase(iterator it) {
		if (it != last()) std::iter_swap(it, last());
		pop_back();
		}

		void swap(SmallVector& other) { Impl::swap(other); }
		};

		template <typename>
		struct IsSmallVector : std::false_type {};

		template <typename T, size_t N>
		struct IsSmallVector<SmallVector<T, N>> : std::true_type {};

		// Deduction guide for array constructor.
		template <typename T, size_t N>
		SmallVector(T (&)[N]) -> SmallVector<std::remove_cv_t<T>, N>;

		// Deduction guide for variadic constructor.
		template <typename T, typename... Us, typename V = std::decay_t<T>,
		typename = std::enable_if_t<(std::is_constructible_v<V, Us> && ...)>>
		SmallVector(T&&, Us&&...) -> SmallVector<V, 1 + sizeof...(Us)>;

		// Deduction guide for in-place constructor.
		template <typename T, typename... Us>
		SmallVector(std::in_place_type_t<T>, Us&&...) -> SmallVector<T, sizeof...(Us)>;

		// Deduction guide for StaticVector conversion.
		template <typename T, size_t N>
		SmallVector(StaticVector<T, N>&&) -> SmallVector<T, N>;

		template <typename T, size_t N>
		inline void swap(SmallVector<T, N>& lhs, SmallVector<T, N>& rhs) {
		lhs.swap(rhs);
		}

		} // namespace android::ftl

include/ftl/StaticVector.h

+41 −73

Original line number	Diff line number	Diff line
		@@ -16,11 +16,12 @@

		#pragma once

		#include <ftl/ArrayTraits.h>

		#include <algorithm>
		#include <cassert>
		#include <iterator>
		#include <memory>
		#include <new>
		#include <type_traits>
		#include <utility>

		@@ -63,9 +64,16 @@ constexpr struct IteratorRangeTag {} IteratorRange;
		// assert(vector == (ftl::StaticVector{'h', 'i', '\0'}));
		//
		template <typename T, size_t N>
		class StaticVector final {
		class StaticVector final : ArrayTraits<T>,
		ArrayIterators<StaticVector<T, N>, T>,
		ArrayComparators<StaticVector> {
		static_assert(N > 0);

		using ArrayTraits<T>::construct_at;

		using Iter = ArrayIterators<StaticVector, T>;
		friend Iter;

		// There is ambiguity when constructing from two iterator-like elements like pointers:
		// they could be an iterator range, or arguments for in-place construction. Assume the
		// latter unless they are input iterators and cannot be used to construct elements. If
		@@ -76,19 +84,19 @@ class StaticVector final {
		std::negation<std::is_constructible<T, I>>>;

		public:
		using value_type = T;
		using size_type = size_t;
		using difference_type = ptrdiff_t;
		FTL_ARRAY_TRAIT(T, value_type);
		FTL_ARRAY_TRAIT(T, size_type);
		FTL_ARRAY_TRAIT(T, difference_type);

		using pointer = value_type*;
		using reference = value_type&;
		using iterator = pointer;
		using reverse_iterator = std::reverse_iterator<iterator>;
		FTL_ARRAY_TRAIT(T, pointer);
		FTL_ARRAY_TRAIT(T, reference);
		FTL_ARRAY_TRAIT(T, iterator);
		FTL_ARRAY_TRAIT(T, reverse_iterator);

		using const_pointer = const value_type*;
		using const_reference = const value_type&;
		using const_iterator = const_pointer;
		using const_reverse_iterator = std::reverse_iterator<const_iterator>;
		FTL_ARRAY_TRAIT(T, const_pointer);
		FTL_ARRAY_TRAIT(T, const_reference);
		FTL_ARRAY_TRAIT(T, const_iterator);
		FTL_ARRAY_TRAIT(T, const_reverse_iterator);

		// Creates an empty vector.
		StaticVector() = default;
		@@ -180,32 +188,26 @@ public:
		bool full() const { return size() == max_size(); }

		iterator begin() { return std::launder(reinterpret_cast<pointer>(mData)); }
		const_iterator begin() const { return cbegin(); }
		const_iterator cbegin() const { return mut().begin(); }

		iterator end() { return begin() + size(); }
		const_iterator end() const { return cend(); }
		const_iterator cend() const { return mut().end(); }

		reverse_iterator rbegin() { return std::make_reverse_iterator(end()); }
		const_reverse_iterator rbegin() const { return crbegin(); }
		const_reverse_iterator crbegin() const { return mut().rbegin(); }
		using Iter::begin;
		using Iter::end;

		reverse_iterator rend() { return std::make_reverse_iterator(begin()); }
		const_reverse_iterator rend() const { return crend(); }
		const_reverse_iterator crend() const { return mut().rend(); }
		using Iter::cbegin;
		using Iter::cend;

		iterator last() { return end() - 1; }
		const_iterator last() const { return mut().last(); }
		using Iter::rbegin;
		using Iter::rend;

		reference front() { return *begin(); }
		const_reference front() const { return mut().front(); }
		using Iter::crbegin;
		using Iter::crend;

		reference back() { return *last(); }
		const_reference back() const { return mut().back(); }
		using Iter::last;

		reference operator[](size_type i) { return *(begin() + i); }
		const_reference operator[](size_type i) const { return mut()[i]; }
		using Iter::back;
		using Iter::front;

		using Iter::operator[];

		// Replaces an element, and returns a reference to it. The iterator must be dereferenceable, so
		// replacing at end() is erroneous.
		@@ -242,7 +244,13 @@ public:
		//
		// On success, the end() iterator is invalidated.
		//
		bool push_back(value_type v) {
		bool push_back(const value_type& v) {
		// Two statements for sequence point.
		const iterator it = emplace_back(v);
		return it != end();
		}

		bool push_back(value_type&& v) {
		// Two statements for sequence point.
		const iterator it = emplace_back(std::move(v));
		return it != end();
		@@ -273,8 +281,6 @@ public:
		private:
		struct Empty {};

		StaticVector& mut() const { return const_cast<StaticVector>(this); }

		// Recursion for variadic constructor.
		template <size_t I, typename E, typename... Es>
		StaticVector(std::index_sequence<I>, E&& element, Es&&... elements)
		@@ -286,13 +292,6 @@ private:
		template <size_t I>
		explicit StaticVector(std::index_sequence<I>) : mSize(I) {}

		// TODO: Replace with std::construct_at in C++20.
		template <typename... Args>
		static pointer construct_at(const_iterator it, Args&&... args) {
		void* const ptr = const_cast<void>(static_cast<const void>(it));
		return new (ptr) value_type{std::forward<Args>(args)...};
		}

		size_type mSize = 0;
		std::aligned_storage_t<sizeof(value_type), alignof(value_type)> mData[N];
		};
		@@ -348,35 +347,4 @@ inline void swap(StaticVector<T, N>& lhs, StaticVector<T, N>& rhs) {
		lhs.swap(rhs);
		}

		// TODO: Replace with operator<=> in C++20.
		template <typename T, size_t N, size_t M>
		inline bool operator==(const StaticVector<T, N>& lhs, const StaticVector<T, M>& rhs) {
		return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
		}

		template <typename T, size_t N, size_t M>
		inline bool operator<(const StaticVector<T, N>& lhs, const StaticVector<T, M>& rhs) {
		return std::lexicographical_compare(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
		}

		template <typename T, size_t N, size_t M>
		inline bool operator>(const StaticVector<T, N>& lhs, const StaticVector<T, M>& rhs) {
		return rhs < lhs;
		}

		template <typename T, size_t N, size_t M>
		inline bool operator!=(const StaticVector<T, N>& lhs, const StaticVector<T, M>& rhs) {
		return !(lhs == rhs);
		}

		template <typename T, size_t N, size_t M>
		inline bool operator>=(const StaticVector<T, N>& lhs, const StaticVector<T, M>& rhs) {
		return !(lhs < rhs);
		}

		template <typename T, size_t N, size_t M>
		inline bool operator<=(const StaticVector<T, N>& lhs, const StaticVector<T, M>& rhs) {
		return !(rhs < lhs);
		}

		} // namespace android::ftl

libs/ftl/Android.bp

+1 −0

Original line number	Diff line number	Diff line
		@@ -5,6 +5,7 @@ cc_test {
		address: true,
		},
		srcs: [
		"SmallVector_test.cpp",
		"StaticVector_test.cpp",
		],
		cflags: [

libs/ftl/SmallVector_test.cpp

0 → 100644

+455 −0

File added.

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