Binaryworld - ReplaceChar - A faster version of VB6's Replace function, for single-c ... [ VB -> String ]

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDst As _
  Any, pSrc As Any, ByVal ByteLen As Long)

' This is a replacement for the "Replace" function provided by VB6,
' though for single character replacements only. The speed difference varies,
' depending on how many characters it needs to replace / the length of the
' string, but the ReplaceChar function has been found to go from approximately
' 1.3 times to 10 times (possibly even more depending) faster. Another point
' worth mentioning is if you check the "Assume No Aliasing" and/or the "Remove
' Array Bounds Checks" compiler options, the routine will go faster.
'
' Example:
'  Dim sInput As String
'  sInput = "This is a test string"
'  MsgBox (ReplaceChar(sInput, "s", "*"))

Function ReplaceChar(ByVal strExpression As String, ByVal findChar As String, _
  ByVal replChar As String) As String
  Dim arrByte() As Byte, lngUB As Long, lngLoop As Long
  Dim bytFind As Byte, bytReplace As Byte

  ' convert the two characters to byte
  bytFind = Asc(findChar)
  bytReplace = Asc(replChar)

  ' get length of string in bytes, and convert to byte array
  lngUB = LenB(strExpression)
  ReDim arrByte(lngUB - 1) As Byte
  CopyMemory arrByte(0), ByVal StrPtr(strExpression), lngUB

  ' swap characters
  For lngLoop = 0 To lngUB - 1 Step 2
    If arrByte(lngLoop) = bytFind Then arrByte(lngLoop) = bytReplace
  Next

  ' convert back to string
  ReplaceChar = Space$(lngUB \ 2)
  CopyMemory ByVal StrPtr(ReplaceChar), arrByte(0), lngUB
End Function