Page 107 - Open Soource Technologies 304.indd

Unit 5: VB String and Operators

ResString = String$(NumberOfCharacters + 2, vbNullChar)
’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’
’ Shorten the text with PathCompactPathEx
’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’
Res = PathCompactPathEx(ResString, InputText, NumberOfCharacters, 0&)
If Res = 0 Then
ErrorNumber = Err.LastDllError
ErrorText = GetSystemErrorMessageText(ErrorNumber)
MsgBox “An error occurred with PathCompactPathEx” & vbCrLf & _
”Error Number: “ & CStr(ErrorNumber) & vbCrLf & _
”Descrition: “ & ErrorText
ShortenTextToChars = vbNullString
Exit Function
End If

’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’
’ trim to get the charcters to the left
’ of the vbNullChar character.
’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’
ResString = TrimToNull(Text:=ResString)
’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’
return the result string
’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’
ShortenTextToChars = ResString
End Function

5.1.7 TrimToNull
When you are calling Windows API functions, you are often required to pass in a string variable
that will be populated with the result of the function. An example is the GetWindowsDirectory
function. In these cases, you must first initialize the string to a given length (often the length
is defined by the constant MAX_PATH = 260, a Windows-mandated value of the maximum length
of a fully-qualified file name). You can use either the String$ or Space$ function to initialize
the string to a given length:

Public Const MAX_PATH = 260 ‘ Windows mandated value

StrValue = String$(MAX_PATH,vbNullChar) ‘ initialize StrValue to MAX_PATH vbNullChars.
’ or
StrValue = Space$(MAX_PATH) ‘ initialize StrValue to MAX_PATH spaces.
When the API call returns, the buffer remains at its original length (the API functions never resize
the result buffer). The API function will put a null character (Chr(0) or vbNullChar) at the end

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