90 lines
2.8 KiB
C++
90 lines
2.8 KiB
C++
/*
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* Copyright (C) 2021-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 <type_traits>
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#include <seastar/util/concepts.hh>
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namespace utils {
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/*
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* Wraps a collection into immutable form.
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*
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* Immutability here means that the collection itself cannot be modified,
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* i.e. adding or removing elements is not possible. Read-only methods such
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* as find(), begin()/end(), lower_bound(), etc. are available and are
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* transparently forwarded to the underlying collection. Return values from
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* those methods are also returned as-is so it's pretty much like a const
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* reference on the collection.
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*
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* The important difference from the const reference is that obtained
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* elements or iterators are not necessarily const too, so it's possible
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* to modify the found or iterated over elements.
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*/
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template <typename Collection>
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class immutable_collection {
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Collection& _col;
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public:
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immutable_collection(Collection& col) noexcept : _col(col) {}
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#define DO_WRAP_METHOD(method, is_const) \
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template <typename... Args> \
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auto method(Args&&... args) is_const noexcept(noexcept(std::declval<is_const Collection>().method(args...))) { \
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return _col.method(std::forward<Args>(args)...); \
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}
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#define WRAP_CONST_METHOD(method) \
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DO_WRAP_METHOD(method, const)
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#define WRAP_METHOD(method) \
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WRAP_CONST_METHOD(method) \
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DO_WRAP_METHOD(method, )
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WRAP_METHOD(find)
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WRAP_METHOD(lower_bound)
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WRAP_METHOD(upper_bound)
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WRAP_METHOD(slice)
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WRAP_METHOD(lower_slice)
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WRAP_METHOD(upper_slice)
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WRAP_CONST_METHOD(empty)
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WRAP_CONST_METHOD(size)
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WRAP_CONST_METHOD(calculate_size)
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WRAP_CONST_METHOD(external_memory_usage)
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WRAP_METHOD(begin)
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WRAP_METHOD(end)
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WRAP_METHOD(rbegin)
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WRAP_METHOD(rend)
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WRAP_CONST_METHOD(cbegin)
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WRAP_CONST_METHOD(cend)
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WRAP_CONST_METHOD(crbegin)
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WRAP_CONST_METHOD(crend)
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#undef WRAP_METHOD
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#undef WRAP_CONST_METHOD
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#undef DO_WRAP_METHOD
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};
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} // namespace utils
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