e6f4996e44
This is more strict than it needs to be, but it avoids any bugs like the one fixed by the previous patch. Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com> Message-Id: <20200422182304.120906-2-espindola@scylladb.com>
66 lines
2.1 KiB
C++
66 lines
2.1 KiB
C++
/*
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* Copyright (C) 2020 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 <seastar/core/rwlock.hh>
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#include <seastar/util/defer.hh>
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#include <seastar/util/noncopyable_function.hh>
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#include <vector>
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// This class supports atomic removes (by using a lock and returning a
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// future) and non atomic insert and iteration (by using indexes).
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template <typename T>
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class atomic_vector {
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std::vector<T> _vec;
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seastar::rwlock _vec_lock;
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public:
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void add(const T& value) {
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_vec.push_back(value);
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}
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seastar::future<> remove(const T& value) {
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return with_lock(_vec_lock.for_write(), [this, value] {
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_vec.erase(std::remove(_vec.begin(), _vec.end(), value), _vec.end());
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});
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}
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// This must be called on a thread. The callback function must not
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// call remove.
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//
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// We would take callbacks that take a T&, but we had bugs in the
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// past with some of those callbacks holding that reference past a
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// preemption.
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void for_each(seastar::noncopyable_function<void(T)> func) {
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_vec_lock.for_read().lock().get();
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auto unlock = seastar::defer([this] {
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_vec_lock.for_read().unlock();
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});
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// We grab a lock in remove(), but not in add(), so we
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// iterate using indexes to guard against the vector being
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// reallocated.
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for (size_t i = 0, n = _vec.size(); i < n; ++i) {
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func(_vec[i]);
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}
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}
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};
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