strip-utf8-bom.vbs

' Usage: strip-utf8-bom.vbs file.csv
' Notes:
'   this isn't suitable for large files unless you have a lot of memory - ADODB.Stream reads the entire file into
'   memory, then builds the output buffer in memory as well. #stupid

If WScript.Arguments.Count <> 1 Then
    WScript.Echo "Usage: strip-utf8-bom.vbs file.csv"
    WScript.Quit
End If

Dim fIn, fOut, sFilename, sBOM
sFilename = WScript.Arguments(0)

Set fIn = CreateObject("adodb.stream")
fIn.Type = 1 'adTypeBinary
fIn.Mode = adModeRead
fIn.Open
fIn.LoadFromFile sFilename

sBOM = fIn.Read(5)
' UTF8 BOM is 0xEF,0xBB,0xBF (decimal 239, 187, 191)
If AscB(MidB(sBOM, 1, 1)) = 239 _
        And AscB(MidB(sBOM, 2, 1)) = 187 _
        And AscB(MidB(sBOM, 3, 1)) = 191 Then

    WScript.Echo(sFilename & ": UTF-8 BOM found... removing")
    
    fIn.Position = 3 ' Skip BOM

    Set fOut = CreateObject("adodb.stream")
    fOut.Type = 1 'adTypeBinary
    fOut.Mode = adModeReadWrite
    fOut.Open

    fIn.CopyTo fOut

    fOut.SaveToFile sFilename, 2 'adSaveCreateOverwrite
    fOut.Flush
    fOut.Close
Else
    WScript.Echo(sFilename & ": No UTF-8 BOM found")
End If