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Tip of the Day
Language: Visual Basic
Expertise: Intermediate
Jan 19, 2000

Generate GUIDs With One API Call

I read a great advanced tip on how to create a GUID in "Generate Unique String IDs" ["101 Tech Tips for VB Developers," Supplement to VBPJ, August 1999]. However, you can use only one API call instead of four. The OLE32.dll contains a function called WinCoCreateGUID that does all the math for you. I have included a second function called PadZeros to format the GUID:
 
Option Explicit
Private Type GUIDType
	D1       As Long
	D2       As Integer
	D3       As Integer
	D4(8)    As Byte
End Type
Private Declare Function WinCoCreateGuid 
		Lib "OLE32.DLL" 
	Alias "CoCreateGuid" (g As GUIDType) As Long
Public Function CreateGUIDString() As String
	Dim g As GUIDType
	Dim sBuf As String
	Call WinCoCreateGuid(g)
	sBuf = PadZeros(Hex$(g.D1), 8, True) & _
		PadZeros(Hex$(g.D2), 4, True) & _
		PadZeros(Hex$(g.D3), 4, True) & _
		PadZeros(Hex$(g.D4(0)), 2) & _
		PadZeros(Hex$(g.D4(1)), 2, True) & _
		PadZeros(Hex$(g.D4(2)), 2) & _
		PadZeros(Hex$(g.D4(3)), 2) & _
		PadZeros(Hex$(g.D4(4)), 2) & _
		PadZeros(Hex$(g.D4(5)), 2) & _
		PadZeros(Hex$(g.D4(6)), 2) & _
		PadZeros(Hex$(g.D4(7)), 2)
	CreateGUIDString = sBuf
End Function

Private Function PadZeros(ByVal sBit As String, _
	ByVal iStrLen As Integer, Optional bHyphen _
	As Boolean) As String
	If iStrLen > Len(sBit) Then
		sBit = Right$(String$((iStrLen - Len(sBit)), _
			"0") & sBit, iStrLen)
	End If
	If bHyphen Then sBit = sBit & "-"
	PadZeros = sBit
End Function
Dj Hackney
 
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