fcb8d040e8
Instead of lengthy blurbs, switch to single-line, machine-readable standardized (https://spdx.dev) license identifiers. The Linux kernel switched long ago, so there is strong precedent. Three cases are handled: AGPL-only, Apache-only, and dual licensed. For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0), reasoning that our changes are extensive enough to apply our license. The changes we applied mechanically with a script, except to licenses/README.md. Closes #9937
88 lines
2.1 KiB
C++
88 lines
2.1 KiB
C++
/*
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* Copyright (C) 2015-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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#pragma once
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#include <functional>
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#include <compare>
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#include "timestamp.hh"
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#include "gc_clock.hh"
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#include "hashing.hh"
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/**
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* Represents deletion operation. Can be commuted with other tombstones via apply() method.
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* Can be empty.
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*/
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struct tombstone final {
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api::timestamp_type timestamp;
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gc_clock::time_point deletion_time;
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tombstone(api::timestamp_type timestamp, gc_clock::time_point deletion_time)
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: timestamp(timestamp)
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, deletion_time(deletion_time)
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{ }
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tombstone()
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: tombstone(api::missing_timestamp, {})
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{ }
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std::strong_ordering operator<=>(const tombstone& t) const = default;
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bool operator==(const tombstone&) const = default;
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bool operator!=(const tombstone&) const = default;
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explicit operator bool() const {
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return timestamp != api::missing_timestamp;
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}
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void apply(const tombstone& t) noexcept {
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if (*this < t) {
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*this = t;
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}
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}
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// See reversibly_mergeable.hh
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void apply_reversibly(tombstone& t) noexcept {
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std::swap(*this, t);
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apply(t);
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}
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// See reversibly_mergeable.hh
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void revert(tombstone& t) noexcept {
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std::swap(*this, t);
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}
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tombstone operator+(const tombstone& t) {
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auto result = *this;
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result.apply(t);
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return result;
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}
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friend std::ostream& operator<<(std::ostream& out, const tombstone& t) {
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if (t) {
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return out << "{tombstone: timestamp=" << t.timestamp << ", deletion_time=" << t.deletion_time.time_since_epoch().count() << "}";
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} else {
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return out << "{tombstone: none}";
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}
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}
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};
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template<>
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struct appending_hash<tombstone> {
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template<typename Hasher>
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void operator()(Hasher& h, const tombstone& t) const {
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feed_hash(h, t.timestamp);
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feed_hash(h, t.deletion_time);
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}
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};
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// Determines whether tombstone may be GC-ed.
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using can_gc_fn = std::function<bool(tombstone)>;
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extern can_gc_fn always_gc;
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