mirror of https://gitee.com/bigwinds/arangodb
116 lines
4.4 KiB
C++
116 lines
4.4 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
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/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Max Neunhoeffer
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////////////////////////////////////////////////////////////////////////////////
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#include "Basics/HybridLogicalClock.h"
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namespace {
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template <typename DurationT, typename ReprT = typename DurationT::rep>
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constexpr DurationT maxDuration() noexcept {
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return DurationT{(std::numeric_limits<ReprT>::max)()};
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}
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template <typename DurationT>
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constexpr DurationT absDuration(const DurationT d) noexcept {
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return DurationT{(d.count() < 0) ? -d.count() : d.count()};
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}
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template <typename SrcTimePointT, typename DstTimePointT, typename SrcDurationT = typename SrcTimePointT::duration,
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typename DstDurationT = typename DstTimePointT::duration,
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typename SrcClockT = typename SrcTimePointT::clock, typename DstClockT = typename DstTimePointT::clock>
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DstDurationT clockOffset(const SrcDurationT tolerance = std::chrono::duration_cast<SrcDurationT>(
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std::chrono::nanoseconds{300}),
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const int limit = 10000) {
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if (std::is_same<SrcClockT, DstClockT>::value) {
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return SrcClockT::from_time_t(0).time_since_epoch();
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}
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auto itercnt = 0;
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auto src_now = SrcTimePointT{};
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auto dst_now = DstTimePointT{};
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auto epsilon = maxDuration<SrcDurationT>();
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do {
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const auto src_before = SrcClockT::now();
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const auto dst_between = DstClockT::now();
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const auto src_after = SrcClockT::now();
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const auto src_diff = src_after - src_before;
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const auto delta = absDuration(src_diff);
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if (delta < epsilon) {
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src_now = src_before + src_diff / 2;
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dst_now = dst_between;
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epsilon = delta;
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}
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if (++itercnt >= limit) {
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break;
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}
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} while (epsilon > tolerance);
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auto diff1970 = SrcClockT::from_time_t(0) - src_now;
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return (dst_now + diff1970).time_since_epoch();
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}
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} // namespace
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char arangodb::basics::HybridLogicalClock::encodeTable[65] =
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"-_ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
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signed char arangodb::basics::HybridLogicalClock::decodeTable[256] = {
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 0 - 15
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 16 - 31
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, 0, -1, -1, // 32 - 47
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54, 55, 56, 57, 58, 59, 60, 61,
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62, 63, -1, -1, -1, -1, -1, -1, // 48 - 63
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-1, 2, 3, 4, 5, 6, 7, 8,
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9, 10, 11, 12, 13, 14, 15, 16, // 64 - 79
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17, 18, 19, 20, 21, 22, 23, 24,
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25, 26, 27, -1, -1, -1, -1, 1, // 80 - 95
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-1, 28, 29, 30, 31, 32, 33, 34,
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35, 36, 37, 38, 39, 40, 41, 42, // 96 - 111
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43, 44, 45, 46, 47, 48, 49, 50,
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51, 52, 53, -1, -1, -1, -1, -1, // 112 - 127
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 128 - 143
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 144 - 159
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 160 - 175
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 176 - 191
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 192 - 207
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 208 - 223
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, // 224 - 239
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1}; // 240 - 255
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uint64_t arangodb::basics::HybridLogicalClock::computeOffset1970() {
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auto diff =
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clockOffset<std::chrono::system_clock::time_point, HybridLogicalClock::ClockT::time_point>();
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return std::chrono::duration_cast<std::chrono::milliseconds>(diff).count();
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}
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