initial commit

libs/Catch2/include/internal/catch_timer.cpp

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+/*
+ *  Created by Phil on 05/08/2013.
+ *  Copyright 2013 Two Blue Cubes Ltd. All rights reserved.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include "catch_timer.h"
+
+#include <chrono>
+
+static const uint64_t nanosecondsInSecond = 1000000000;
+
+namespace Catch {
+
+    auto getCurrentNanosecondsSinceEpoch() -> uint64_t {
+        return std::chrono::duration_cast<std::chrono::nanoseconds>( std::chrono::high_resolution_clock::now().time_since_epoch() ).count();
+    }
+
+    namespace {
+        auto estimateClockResolution() -> uint64_t {
+            uint64_t sum = 0;
+            static const uint64_t iterations = 1000000;
+
+            auto startTime = getCurrentNanosecondsSinceEpoch();
+
+            for( std::size_t i = 0; i < iterations; ++i ) {
+
+                uint64_t ticks;
+                uint64_t baseTicks = getCurrentNanosecondsSinceEpoch();
+                do {
+                    ticks = getCurrentNanosecondsSinceEpoch();
+                } while( ticks == baseTicks );
+
+                auto delta = ticks - baseTicks;
+                sum += delta;
+
+                // If we have been calibrating for over 3 seconds -- the clock
+                // is terrible and we should move on.
+                // TBD: How to signal that the measured resolution is probably wrong?
+                if (ticks > startTime + 3 * nanosecondsInSecond) {
+                    return sum / ( i + 1u );
+                }
+            }
+
+            // We're just taking the mean, here. To do better we could take the std. dev and exclude outliers
+            // - and potentially do more iterations if there's a high variance.
+            return sum/iterations;
+        }
+    }
+    auto getEstimatedClockResolution() -> uint64_t {
+        static auto s_resolution = estimateClockResolution();
+        return s_resolution;
+    }
+
+    void Timer::start() {
+       m_nanoseconds = getCurrentNanosecondsSinceEpoch();
+    }
+    auto Timer::getElapsedNanoseconds() const -> uint64_t {
+        return getCurrentNanosecondsSinceEpoch() - m_nanoseconds;
+    }
+    auto Timer::getElapsedMicroseconds() const -> uint64_t {
+        return getElapsedNanoseconds()/1000;
+    }
+    auto Timer::getElapsedMilliseconds() const -> unsigned int {
+        return static_cast<unsigned int>(getElapsedMicroseconds()/1000);
+    }
+    auto Timer::getElapsedSeconds() const -> double {
+        return getElapsedMicroseconds()/1000000.0;
+    }
+
+
+} // namespace Catch