QueryPerformanceCounter是为一个指针变量用于函数传值，提供高分辨率计时器。
QueryPerformanceCounter是为一个指针变量用于函数传值，提供高分辨率计时器。
The QueryPerformanceCounter function retrieves the current value of the high-resolution performance counter, if one exists.
BOOL QueryPerformanceCounter(
LARGE_INTEGER *lpPerformanceCount // pointer to counter value
);
Parameters
lpPerformanceCount
Pointer to a variable that the function sets, in counts, to the current performance-counter value. If the installed hardware does not support a high-resolution performance counter, this parameter can be to zero.
Return Values
If the installed hardware supports a high-resolution performance counter, the return value is nonzero.
If the installed hardware does not support a high-resolution performance counter, the return value is zero.
函数QueryPerformanceCounter用于得到高精度计时器的值(如果存在这样的计时器)
BOOL QueryPerformanceCounter(LARGE_INTEGER *ipPerformanceCount);//参数指向计数器的值
参数LARGE_INTEGER *ipProformanceCount
为一个指针变量用于函数传值,即指向现时计数器的值.如果安装的硬件不支持高精度计时器,该参数将返回0,
关于返回值:
如果安装的硬件支持高精度计时器,函数将返回非0值.
如果安装的硬件不支持高精度计时器,函数将返回0.
)
QuickInfo
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winbase.h.
import Library: Use kernel32.lib.
计时代码以查明性能瓶颈, 时要使用系统有以提供高分辨率计时器。 下例介绍如何使用 QueryPerformanceCounter 函数以应用程序代码。
输入下列代码插入模块。 如果类、, 窗体或报表模块, 中输入它使声明 Private。
Option Explicit
Declare Function QueryPerformanceCounter Lib "Kernel32" _
(X As Currency) As Boolean
Declare Function QueryPerformanceFrequency Lib "Kernel32" _
(X As Currency) As Boolean
Declare Function GetTickCount Lib "Kernel32" () As Long
Declare Function timeGetTime Lib "winmm.dll" () As Long
Sub Test_Timers()
Dim Ctr1 As Currency, Ctr2 As Currency, Freq As Currency
Dim Count1 As Long, Count2 As Long, Loops As Long
'
' Time QueryPerformanceCounter
'
If QueryPerformanceCounter(Ctr1) Then
QueryPerformanceCounter Ctr2
Debug.Print "Start Value: "; Format$(Ctr1, "0.0000")
Debug.Print "End Value: "; Format$(Ctr2, "0.0000")
QueryPerformanceFrequency Freq
Debug.Print "QueryPerformanceCounter minimum resolution: 1/" & _
Freq * 10000; " sec"
Debug.Print "API Overhead: "; (Ctr2 - Ctr1) / Freq; "seconds"
Else
Debug.Print "High-resolution counter not supported."
End If
'
' Time GetTickCount
'
Debug.Print
Loops = 0
Count1 = GetTickCount()
Do
Count2 = GetTickCount()
Loops = Loops + 1
Loop Until Count1 <> Count2
Debug.Print "GetTickCount minimum resolution: "; _
(Count2 - Count1); "ms"
Debug.Print "Took"; Loops; "loops"
'
' Time timeGetTime
'
Debug.Print
Loops = 0
Count1 = timeGetTime()
Do
Count2 = timeGetTime()
Loops = Loops + 1
Loop Until Count1 <> Count2
Debug.Print "timeGetTime minimum resolution: "; _
(Count2 - Count1); "ms"
Debug.Print "Took"; Loops; "loops"
End Sub
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