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Tip of the Day
Language: Visual Basic
Expertise: Beginner
Jun 1, 1999

Scrub Out Unused Constants

Low-level parsing in VB doesn't come up every day. This routine demonstrates how to search a VB module for dead module-level constants with only a few lines of code. Reading the entire contents of a file into a string variable is key to this approach:
 
Private Sub FindDeadConstants(ByVal _
	PathAndFile As String)
	Dim FileHandle As Integer
	Dim FileContents As String
	Dim PositionOfDeclaration As Long
	Dim StartOfConstantName As Long
	Dim EndOfConstantName As Long
	Dim ConstantName As String

	'open the file and read the contents 
	'into a string variable:
	FileHandle = FreeFile
	Open PathAndFile For Binary Access _
		Read As FileHandle
	FileContents = _
		Input$(LOF(FileHandle), _
		FileHandle)
	Close FileHandle

	'loop through all the module-level 
	'constants:
	Do
		PositionOfDeclaration = _
			InStr(PositionOfDeclaration _
			+ 1, FileContents, _
			"Private Const ")
		If PositionOfDeclaration > 0 Then
			'we've found a constant:
			StartOfConstantName = _
				PositionOfDeclaration _
				+ Len("Private Const ")
			EndOfConstantName = _
				InStr( _
				StartOfConstantName, _
				FileContents, " ")
			ConstantName = _
				Mid$(FileContents, _
				StartOfConstantName, _
					EndOfConstantName _
					- StartOfConstantName)
			'if the constant is not 
			'referenced beyond its 
			'declaration, then it's dead:
			If InStr(EndOfConstantName, _
				FileContents, _
				ConstantName) = 0 Then
				lstDeadConstants.AddItem _
					ConstantName
			End If
		End If
	Loop Until PositionOfDeclaration = 0
End Sub
Dave Doknjas
 
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