82 lines
2.5 KiB
C++
82 lines
2.5 KiB
C++
/*
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* Licensed to Green Energy Corp (www.greenenergycorp.com) under one or
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* more contributor license agreements. See the NOTICE file distributed
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* with this work for additional information regarding copyright ownership.
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* Green Energy Corp licenses this file to you under the Apache License,
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* Version 2.0 (the "License"); you may not use this file except in
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* compliance with the License. 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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* This project was forked on 01/01/2013 by Automatak, LLC and modifications
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* may have been made to this file. Automatak, LLC licenses these modifications
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* to you under the terms of the License.
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*/
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#ifndef ASIOPAL_STEADYCLOCK_H
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#define ASIOPAL_STEADYCLOCK_H
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#include <chrono>
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namespace asiopal
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{
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#if (defined WIN32 && (_MSC_VER < 1900)) // Windows with VS eariler than 2015, e.g. 2013
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#include <Windows.h>
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/*
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Custom steady clock implementation to handle the situation where the Windows steady clock
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implementation is not monotonic. Normal steady clock implementation is used on other platforms.
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*/
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struct SteadyClockWindows
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{
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// Type defininitions for this clock - ticks are in nanoseconds for this clock
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typedef LONGLONG representation;
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typedef std::ratio_multiply<std::ratio<1, 1>, std::nano> period;
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typedef std::chrono::duration<representation, period> duration;
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typedef std::chrono::time_point<SteadyClockWindows, duration> time_point;
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static time_point now()
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{
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// Special case for WIN32 because std::chrono::steady_clock is broken
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LARGE_INTEGER freq;
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LONGLONG nanoSecondsPerTick = 0;
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if (QueryPerformanceFrequency(&freq))
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{
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nanoSecondsPerTick = LONGLONG(1000000000.0L / freq.QuadPart);
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}
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LARGE_INTEGER performanceCount;
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if (nanoSecondsPerTick <= 0 || !QueryPerformanceCounter(&performanceCount))
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{
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// Error condition, return 0 time
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return time_point();
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}
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// Return time in nanoseconds
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LONGLONG timeNanos = performanceCount.QuadPart * nanoSecondsPerTick;
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return time_point(duration(timeNanos));
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}
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};
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// use this custom steady clock
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typedef SteadyClockWindows steady_clock_t;
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#else
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// In all other situations use the normal steady clock
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typedef std::chrono::steady_clock steady_clock_t;
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#endif
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}
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#endif |