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QueryPerformanceCounter Demystified


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GUICreate('System Uptime')
Global $label = GUICtrlCreateLabel(' hrs  min  sec  cts' & @CRLF & '(freq:  Hz)',0,0,400)
Global $kern32 = DllOpen('Kernel32.dll')
Global Const $freq = DllCall($kern32, 'bool', 'QueryPerformanceFrequency', 'Int64*', Null)[1]
GUICtrlSetFont($label, 9, 0, 0, "Consolas")
Local $tick,$sec
While Sleep(10)
      $tick = DllCall($kern32, 'bool', 'QueryPerformanceCounter', 'Int64*', Null)[1]
      $sec = $tick/$freq
      GUICtrlSetData($label, Int($sec/3600) & ' hrs ' & Int(Mod($sec,3600)/60) & ' min ' & Int(Mod($sec,60)) & ' sec ' & Mod($tick,$freq) & ' cts' & @CRLF & '(freq: ' & $freq & ' Hz)')

Func Quit()

1. QueryPerformanceFrequency stays the same from system launch, so treat it as a constant

2. QueryPerformanceCounter is in cycles counts since system launch, so it is a reliable timestamp since the frequency reference doesn't change

Edited by AutoXenon
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