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如果你觉得用 DotNet 自带的 DateTime 获取的时间精度不够，解决的方法是通过调用 QueryPerformanceFrequency 和 QueryPerformanceCounter这两个API来实现。 QueryPerformanceCounter 最小分辨率： 1/1193182 秒 多个语句执行之前 GetTickCount 或 timeGetTime 记录的更改。实际的循环数因操作系统正在执行的后台任务而异。
//引用的命名空间
using System.Runtime.InteropServices;
using System.Security;
////////////////////////////
/// <summary>
/// 定义一个高精度的时间类
/// </summary>
public class Timer
{
#region private members
private long ticksPerSecond = 0;
private long elapsedTime = 0;
private long baseTime = 0;
#endregion
#region windows API
/// <summary>
/// 获取时间的精度
/// </summary>
/// <param name="PerformanceFrequency"></param>
/// <returns></returns>
[SuppressUnmanagedCodeSecurity]
[DllImport("kernel32")]
static private extern bool QueryPerformanceFrequency(ref long PerformanceFrequency);
/// <summary>
/// 获取时间计数
/// </summary>
/// <param name="PerformanceCount"></param>
/// <returns></returns>
[SuppressUnmanagedCodeSecurity]
[DllImport("kernel32")]
static private extern bool QueryPerformanceCounter(ref long PerformanceCount);
#endregion
#region constructors
/// <summary>
/// new
/// </summary>
public Timer()
{
// Use QueryPerformanceFrequency to get frequency of the timer
if (!QueryPerformanceFrequency(ref ticksPerSecond))
throw new ApplicationException("Timer: Performance Frequency Unavailable");
Reset();
}
#endregion
#region public methods
/// <summary>
/// 重置时间相关计数器
/// </summary>
public void Reset()
{
long time = 0;
QueryPerformanceCounter(ref time);
baseTime = time;
elapsedTime = 0;
}
/// <summary>
/// 获取当前与最近一次 reset 时间差
/// </summary>
/// <returns>The time since last reset.</returns>
public double GetTime()
{
long time = 0;
QueryPerformanceCounter(ref time);
return (double)(time - baseTime) / (double)ticksPerSecond;
}
/// <summary>
/// 获取当前系统的时间 ticks 数
/// </summary>
/// <returns>The current time in seconds.</returns>
public double GetAbsoluteTime()
{
long time = 0;
QueryPerformanceCounter(ref time);
return (double)time / (double)ticksPerSecond;
}
/// <summary>
/// 获取此次与上次调用此方法的两次时间差
/// </summary>
/// <returns>The number of seconds since last call of this function.</returns>
public double GetElapsedTime()
{
long time = 0;
QueryPerformanceCounter(ref time);
double absoluteTime = (double)(time - elapsedTime) / (double)ticksPerSecond;
elapsedTime = time;
return absoluteTime;
}
#endregion
}
调用代码举例：
//////////////////////////////////////////////////// 在某些计算机上，由 QueryPerformanceFrequency 返回的结果将作为 CPU 的时钟速度。在处理器运行速度超过 2.1 GHz 的计算机上，该频率值需要至少 32 位的精度。某些程序将 QueryPerformanceFrequency 的结果用作经过签署的整数值，该值只有 31 位精度并带有符号标志。这些程序在这些较快的 CPU 上无法正确运行。要避免出现此问题，程序必须使用由 QueryPerformanceFrequency 和 QueryPerformanceCounter 返回的所有64 位。
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