Add BitfieldPack implementation.
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153
include/duckhandy/bitfield_pack.hpp
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153
include/duckhandy/bitfield_pack.hpp
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/* Copyright 2016-2018 Michele Santullo
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* This file is part of "duckhandy".
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*
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* "duckhandy" is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* "duckhandy" is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with "duckhandy". If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef id895441FC389F481EB824A809A0BF5004
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#define id895441FC389F481EB824A809A0BF5004
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#include <cstddef>
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#include <stdexcept>
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#include <climits>
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namespace dhandy {
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namespace implem {
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template <typename T, std::size_t Index>
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class BitfieldData;
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template <typename T, std::size_t Index>
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class BitfieldData : public BitfieldData<T, Index - 1> {
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protected:
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BitfieldData (T init) : BitfieldData<T, Index - 1>(init), m_value(init) {}
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public:
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T& value() { return m_value; }
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T value() const { return m_value; }
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private:
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T m_value;
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};
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template <typename T>
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class BitfieldData<T, 1> {
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protected:
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BitfieldData (T init) : m_value(init) {}
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public:
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T& value() { return m_value; }
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T value() const { return m_value; }
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private:
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T m_value;
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};
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template <typename T>
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class BitfieldData<T, 0>;
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struct SizeAndOffs {
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std::size_t size, offset;
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};
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template <std::size_t Sum>
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[[gnu::pure]]
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constexpr inline SizeAndOffs size_and_offset_impl (std::size_t) {
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throw std::out_of_range("Requested pack index out of range");
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}
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template <std::size_t Sum, std::size_t Sz, std::size_t... Sizes>
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[[gnu::pure]]
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constexpr inline SizeAndOffs size_and_offset_impl (std::size_t index) {
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return (index ? size_and_offset_impl<Sum + Sz, Sizes...>(index - 1) : SizeAndOffs{Sz, Sum});
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}
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template <std::size_t... Sizes>
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[[gnu::pure]]
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constexpr inline SizeAndOffs size_and_offset (std::size_t index) {
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return size_and_offset_impl<0, Sizes...>(index);
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}
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template <typename T, std::size_t... Sizes>
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struct BitfieldFacts {
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static const constexpr std::size_t Sum = size_and_offset<Sizes...>(sizeof...(Sizes) - 1).size + size_and_offset<Sizes...>(sizeof...(Sizes) - 1).offset;
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static const constexpr std::size_t ElementCount = (Sum + CHAR_BIT * sizeof(T) - 1) / (CHAR_BIT *sizeof(T));
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};
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template <typename T>
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constexpr inline T make_mask (std::size_t len) {
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return (1 << len) - 1;
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}
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} //namespace implem
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template <typename T, std::size_t... Sizes>
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class BitfieldPack;
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template <std::size_t Idx, typename T, std::size_t... Sizes>
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T get (const BitfieldPack<T, Sizes...>&);
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template <std::size_t Idx, typename T, typename V, std::size_t... Sizes>
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void set (BitfieldPack<T, Sizes...>&, V);
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template <typename T, std::size_t... Sizes>
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class BitfieldPack : private implem::BitfieldData<T, implem::BitfieldFacts<T, Sizes...>::ElementCount> {
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template <std::size_t Idx, typename U, std::size_t... S> friend U get (const BitfieldPack<U, S...>&);
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template <std::size_t Idx, typename U, typename V, std::size_t... S> friend void set (BitfieldPack<U, S...>&, V);
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typedef implem::BitfieldData<T, implem::BitfieldFacts<T, Sizes...>::ElementCount> base_type;
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public:
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BitfieldPack (T init=T{}) : base_type(init) {}
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};
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template <std::size_t Idx, typename T, std::size_t... Sizes>
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T get (const BitfieldPack<T, Sizes...>& pack) {
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using implem::size_and_offset;
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using implem::BitfieldData;
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using implem::make_mask;
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const constexpr auto so = size_and_offset<Sizes...>(Idx);
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const constexpr std::size_t index = so.offset / (sizeof(T) * CHAR_BIT);
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const constexpr std::size_t reloffs = so.offset % (sizeof(T) * CHAR_BIT);
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const constexpr bool bleeds_into_next = reloffs + so.size > sizeof(T) * CHAR_BIT;
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const T bottom = static_cast<const BitfieldData<T, index + 1>&>(pack).value() >> reloffs;
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if (bleeds_into_next) {
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const std::size_t safe_index = index + 2 - not bleeds_into_next;
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const T val = static_cast<const BitfieldData<T, safe_index>&>(pack).value();
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const T top = val << (sizeof(T) * CHAR_BIT - reloffs);
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return static_cast<T>(top | bottom) & make_mask<T>(so.size);
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}
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return bottom & make_mask<T>(so.size);
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}
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template <std::size_t Idx, typename T, typename V, std::size_t... Sizes>
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void set (BitfieldPack<T, Sizes...>& pack, V val) {
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using implem::size_and_offset;
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using implem::BitfieldData;
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using implem::make_mask;
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const constexpr auto so = size_and_offset<Sizes...>(Idx);
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const constexpr std::size_t index = so.offset / (sizeof(T) * CHAR_BIT);
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const constexpr std::size_t reloffs = so.offset % (sizeof(T) * CHAR_BIT);
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const constexpr bool bleeds_into_next = reloffs + so.size > sizeof(T) * CHAR_BIT;
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T& bottom = static_cast<BitfieldData<T, index + 1>&>(pack).value();
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bottom &= ~(make_mask<T>(so.size) << reloffs);
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bottom |= static_cast<T>((val << reloffs) & make_mask<T>(so.size));
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if (bleeds_into_next) {
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const std::size_t safe_index = index + 2 - not bleeds_into_next;
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T& top = static_cast<BitfieldData<T, safe_index>&>(pack).value();
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const constexpr std::size_t shift = sizeof(T) * CHAR_BIT - reloffs;
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top &= ~(make_mask<T>(so.size) >> shift);
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top |= val >> shift;
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}
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}
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} //namespace dhandy
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#endif
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@ -6,6 +6,7 @@ add_executable(${PROJECT_NAME}
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endianness_test.cpp
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int_conv_test.cpp
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reversed_sized_array_test.cpp
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bitfield_pack_test.cpp
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)
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set_property(TARGET ${PROJECT_NAME} PROPERTY CXX_STANDARD 17)
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set_property(TARGET ${PROJECT_NAME} PROPERTY CXX_STANDARD_REQUIRED ON)
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35
test/unit/bitfield_pack_test.cpp
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35
test/unit/bitfield_pack_test.cpp
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@ -0,0 +1,35 @@
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/* Copyright 2016-2018 Michele Santullo
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* This file is part of "duckhandy".
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*
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* "duckhandy" is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* "duckhandy" is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with "duckhandy". If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "catch2/catch.hpp"
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#include "duckhandy/bitfield_pack.hpp"
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#include <cstdint>
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TEST_CASE ("Check correctness in BitfieldPack", "[BitfieldPack][containers]") {
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dhandy::BitfieldPack<uint8_t, 4, 7, 1> pack(0xAA);
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CHECK(sizeof(pack) == sizeof(uint8_t) * 2);
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CHECK(dhandy::get<0>(pack) == 0b1010U);
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CHECK(dhandy::get<1>(pack) == 0b0101010U);
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CHECK(dhandy::get<2>(pack) == 0b1U);
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dhandy::set<0>(pack, 2);
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CHECK(dhandy::get<0>(pack) == 2);
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dhandy::set<1>(pack, 50);
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CHECK(dhandy::get<1>(pack) == 50);
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CHECK(dhandy::get<2>(pack) == 0b1U);
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}
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