88 lines
2.7 KiB
C++
88 lines
2.7 KiB
C++
/*
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* Copyright (C) 2015-present ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero 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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* Scylla 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 Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <map>
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#include <set>
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template<typename Key>
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struct map_difference {
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// Entries in left map whose keys don't exist in the right map.
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std::set<Key> entries_only_on_left;
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// Entries in right map whose keys don't exist in the left map.
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std::set<Key> entries_only_on_right;
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// Entries that appear in both maps with the same value.
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std::set<Key> entries_in_common;
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// Entries that appear in both maps but have different values.
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std::set<Key> entries_differing;
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map_difference()
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: entries_only_on_left{}
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, entries_only_on_right{}
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, entries_in_common{}
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, entries_differing{}
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{ }
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};
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/**
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* Produces a map_difference between the two specified maps, with Key keys and
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* Tp values, using the provided equality function. In order to work with any
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* map type, such as std::map and std::unordered_map, Args holds the remaining
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* type parameters of the particular map type.
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*/
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template<template<typename...> class Map,
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typename Key,
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typename Tp,
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typename Eq = std::equal_to<Tp>,
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typename... Args>
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inline
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map_difference<Key>
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difference(const Map<Key, Tp, Args...>& left,
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const Map<Key, Tp, Args...>& right,
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Eq equals = Eq())
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{
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map_difference<Key> diff{};
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for (auto&& kv : right) {
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diff.entries_only_on_right.emplace(kv.first);
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}
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for (auto&& kv : left) {
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auto&& left_key = kv.first;
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auto&& it = right.find(left_key);
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if (it != right.end()) {
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diff.entries_only_on_right.erase(left_key);
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const Tp& left_value = kv.second;
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const Tp& right_value = it->second;
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if (equals(left_value, right_value)) {
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diff.entries_in_common.emplace(left_key);
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} else {
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diff.entries_differing.emplace(left_key);
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}
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} else {
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diff.entries_only_on_left.emplace(left_key);
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}
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}
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return diff;
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}
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