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db_clock.hh
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db_clock.hh
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/*
* Copyright (C) 2014 Cloudius Systems, Ltd.
*/
/*
* This file is part of Scylla.
*
* Scylla is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Scylla is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef DB_CLOCK_HH_
#define DB_CLOCK_HH_
#include <chrono>
#include <cstdint>
#include "gc_clock.hh"
// the database clock follows Java - 1ms granularity, 64-bit counter, 1970 epoch
class db_clock {
public:
using base = std::chrono::system_clock;
using rep = int64_t;
using period = std::ratio<1, 1000>; // milliseconds
using duration = std::chrono::duration<rep, period>;
using time_point = std::chrono::time_point<db_clock, duration>;
static constexpr bool is_steady = base::is_steady;
static std::time_t to_time_t(time_point t) {
return std::chrono::duration_cast<std::chrono::seconds>(t.time_since_epoch()).count();
}
static time_point from_time_t(std::time_t t) {
return time_point(std::chrono::duration_cast<duration>(std::chrono::seconds(t)));
}
static time_point now() {
auto now_since_epoch = base::now() - base::from_time_t(0);
return time_point(std::chrono::duration_cast<duration>(now_since_epoch)) + get_clocks_offset();
}
static uint64_t now_in_usecs() {
return now().time_since_epoch().count() * 1000;
}
};
static inline
gc_clock::time_point to_gc_clock(db_clock::time_point tp) {
static_assert(std::is_same<db_clock::base, gc_clock::base>::value, "Below we assume that base is the same");
return gc_clock::time_point(std::chrono::duration_cast<gc_clock::duration>(tp.time_since_epoch()));
}
#endif /* DB_CLOCK_HH_ */