毫秒级和纳秒级计时的API--timeGetTime、GetTickCount、QueryPerformanceCounter

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实现毫秒级和纳秒级计数的几个API--timeGetTime、GetTickCount、QueryPerformanceCoun

http://club.excelhome.NET/thread-907289-1-1.html

【你不是一个人在学习VB6】在此基础上做了少量改动，以更好地演示几个API的计时效果。

窗体上放一个命令按钮。窗体代码如下：

Option Explicit

Private Declare Function timeGetTime Lib "winmm.dll" () As Long
Private Declare Function GetTickCount Lib "kernel32" () As Long

Private Declare Function QueryPerformanceCounter Lib "kernel32 " (lpPerformanceCount As Any) As Long
Private Declare Function QueryPerformanceFrequency Lib "kernel32 " (lpFrequency As Any) As Long

Private Declare Sub Sleep Lib "KERNEL32.dll" (ByVal dwMilliseconds As Long)

Private Sub Command1_Click()
  timeCount
End Sub

Sub timeCount()
    Dim curFrequency As Currency
    Dim curStart As Currency
    Dim curEnd As Currency
    Dim delayms%
    
'    delayms = 66
'    delayms = 1
    Randomize
    delayms = Int((1000 - 1 + 1) * Rnd + 1)
    Me.Caption = "要求 sleep " & delayms & "毫秒，实际结果是："

    QueryPerformanceFrequency curFrequency
    QueryPerformanceCounter curStart            '精度100ns
    Sleep delayms
    QueryPerformanceCounter curEnd
    MsgBox "QueryPerformanceCounter计时： " & (curEnd - curStart) / curFrequency * 1000 & "毫秒"
    
    curStart = Timer               '精度55ms
    Sleep delayms
    MsgBox "Timer计时： " & (Timer - curStart) * 1000 & "毫秒"
    
    curStart = GetTickCount        '精度55ms
    Sleep delayms
    MsgBox "GetTickCount计时： " & (GetTickCount - curStart) & "毫秒"
    
    curStart = timeGetTime         '精度10ms
    Sleep delayms
    MsgBox "timeGetTime计时： " & (timeGetTime - curStart) & "毫秒"

    Me.Caption = "请继续。。。"
End Sub