How to get time elapsed in milliseconds

Question

Since performance of string concatenation is quite weak in VB6 I'm testing several StringBuilder implementations. To see how long they're running, I currently use the built-in

Timer

function which only gives me the number of seconds that have passed after midnight.

Is there a way (I guess by importing a system function) to get something with milliseconds precision?

Answer 1

Yes, you can use the Win32 API:

DWORD WINAPI GetTickCount(void);

To import it in VB6 declare it like this:

Private Declare Function GetTickCount Lib "kernel32" () As Long

Call it before the operation and after and then calculate the difference in time passed.

Answer 2

Put the following code in a Stopwatch class:

Option Explicit

Private Declare Function QueryPerformanceCounter Lib "Kernel32" (X As Currency) As Boolean
Private Declare Function QueryPerformanceFrequency Lib "Kernel32" (X As Currency) As Boolean

Private m_startTime As Currency
Private m_freq As Currency
Private m_overhead As Currency

Public Sub start()
    QueryPerformanceCounter m_startTime
End Sub

Public Function ElapsedSeconds() As Double
    Dim currentTime As Currency
    QueryPerformanceCounter currentTime
    ElapsedSeconds = (currentTime - m_startTime - m_overhead) / m_freq
End Function

Public Function ElapsedMilliseconds() As Double
    ElapsedMilliseconds = ElapsedSeconds * 1000
End Function

Private Sub Class_Initialize()
    QueryPerformanceFrequency m_freq
    Dim ctr1 As Currency
    Dim ctr2 As Currency
    QueryPerformanceCounter ctr1
    QueryPerformanceCounter ctr2
    m_overhead = ctr2 - ctr1
End Sub

You can use it as follows:

Dim sw as StopWatch
Set sw = New StopWatch
sw.Start

' Code you want to time

Debug.Print "Code took " & sw.ElapsedMilliseconds " ms"