Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Services / Monitoring / system / Diagnosticts / Stopwatch.cs / 1305376 / Stopwatch.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== /*============================================================ ** ** Class: Stopwatch ** ** Purpose: Implementation for Stopwatch class. ** ** Date: Nov 27, 2002 ** ===========================================================*/ namespace System.Diagnostics { using Microsoft.Win32; using System; // This class uses high-resolution performance counter if installed hardware // does not support it. Otherwise, the class will fall back to DateTime class // and uses ticks as a measurement. public class Stopwatch { private const long TicksPerMillisecond = 10000; private const long TicksPerSecond = TicksPerMillisecond * 1000; private long elapsed; private long startTimeStamp; private bool isRunning; // "Frequency" stores the frequency of the high-resolution performance counter, // if one exists. Otherwise it will store TicksPerSecond. // The frequency cannot change while the system is running, // so we only need to initialize it once. public static readonly long Frequency; public static readonly bool IsHighResolution; // performance-counter frequency, in counts per ticks. // This can speed up conversion from high frequency performance-counter // to ticks. private static readonly double tickFrequency; static Stopwatch() { bool succeeded = SafeNativeMethods.QueryPerformanceFrequency(out Frequency); if(!succeeded) { IsHighResolution = false; Frequency = TicksPerSecond; tickFrequency = 1; } else { IsHighResolution = true; tickFrequency = TicksPerSecond; tickFrequency /= Frequency; } } public Stopwatch() { Reset(); } public void Start() { // Calling start on a running Stopwatch is a no-op. if(!isRunning) { startTimeStamp = GetTimestamp(); isRunning = true; } } public static Stopwatch StartNew() { Stopwatch s = new Stopwatch(); s.Start(); return s; } public void Stop() { // Calling stop on a stopped Stopwatch is a no-op. if( isRunning) { long endTimeStamp = GetTimestamp(); long elapsedThisPeriod = endTimeStamp - startTimeStamp; elapsed += elapsedThisPeriod; isRunning = false; if (elapsed < 0) { // When measuring small time periods the StopWatch.Elapsed* // properties can return negative values. This is due to // bugs in the basic input/output system (BIOS) or the hardware // abstraction layer (HAL) on machines with variable-speed CPUs // (e.g. Intel SpeedStep). elapsed = 0; } } } public void Reset() { elapsed = 0; isRunning = false; startTimeStamp = 0; } // Convenience method for replacing {sw.Reset(); sw.Start();} with a single sw.Restart() public void Restart() { elapsed = 0; startTimeStamp = GetTimestamp(); isRunning = true; } public bool IsRunning { get { return isRunning; } } public TimeSpan Elapsed { get { return new TimeSpan( GetElapsedDateTimeTicks()); } } public long ElapsedMilliseconds { get { return GetElapsedDateTimeTicks()/TicksPerMillisecond; } } public long ElapsedTicks { get { return GetRawElapsedTicks(); } } public static long GetTimestamp() { if(IsHighResolution) { long timestamp = 0; SafeNativeMethods.QueryPerformanceCounter(out timestamp); return timestamp; } else { return DateTime.UtcNow.Ticks; } } // Get the elapsed ticks. private long GetRawElapsedTicks() { long timeElapsed = elapsed; if( isRunning) { // If the StopWatch is running, add elapsed time since // the Stopwatch is started last time. long currentTimeStamp = GetTimestamp(); long elapsedUntilNow = currentTimeStamp - startTimeStamp; timeElapsed += elapsedUntilNow; } return timeElapsed; } // Get the elapsed ticks. private long GetElapsedDateTimeTicks() { long rawTicks = GetRawElapsedTicks(); if( IsHighResolution) { // convert high resolution perf counter to DateTime ticks double dticks = rawTicks; dticks *= tickFrequency; return unchecked((long)dticks); } else { return rawTicks; } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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