QueryPerformanceCounter

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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.
(中文譯文:
函式QueryPerformanceCounter用於得到高精度計時器的值(如果存在這樣的計時器)
BOOL QueryPerformanceCounter(LARGE_INTEGER *ipPerformanceCount);//參數指向計數器的值
參數LARGE_INTEGER *ipProformanceCount
為一個指針變數用於函式傳值,即指向現時計數器的值.如果安裝的硬體不支持高精度計時器,該參數將返回0,
關於返回值:
如果安裝的硬體支持高精度計時器,函式將返回非0值.
如果安裝的硬體不支持高精度計時器,函式將返回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.
計時代碼以查明性能瓶頸, 時要使用系統有以提供高解析度計時器。 下例介紹如何使用 QueryPerformanceCounter 函式以應用程式代碼。
輸入下列代碼插入模組。 如果類、, 窗體或報表模組, 中輸入它使聲明 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"
&#039;
&#039; Time timeGetTime
&#039;
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