Visual Basic Very Fast String Concatenation

[Kaway]

[HIDE-THANKS]AppendStrings uses the WINAPI copymemory function to block-copy pre-allocated string buffers. MIDAppendStrings functions similar, but uses the MID$ function, which is safe for IIS COM components.

Usage: strResult = AppendStrings(strLargeString,strSmallString,strMediumString,.....)

Api.

>Declare Function VarPtrArray Lib "msvbvm60.dll" Alias "VarPtr" (Ptr() As Any) As Long

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

>Public Function AppendStrings( _
  strOriginal As String, _
  ParamArray varConcatString() As Variant) As String
   
  Dim i As Long
  Dim X As Long
  Dim lngTotal As Long
  Dim strBuffer As String
  Dim lngBufferSize As Long
  Dim lngLength As Long
  Dim lngPosition As Long
  
  If IsArray(varConcatString) = False Then
      AppendStrings = strOriginal
      Exit Function
  End If
  lngTotal = UBound(varConcatString)
  For i = 0 To lngTotal
     lngBufferSize = lngBufferSize + Len(varConcatString(i))
  Next i
  
  AppendStrings = Space$(lngBufferSize + Len(strOriginal))
  Mid$(AppendStrings, 1, Len(strOriginal)) = strOriginal
  lngBufferSize = Len(strOriginal) + 1
  
  For i = 0 To lngTotal
     lngLength = Len(varConcatString(i))
     If lngLength Then
        CopyMemory ByVal StrPtr(AppendStrings) + lngPosition, _
           ByVal StrPtr(strOriginal), LenB(strOriginal)
        lngPosition = lngPosition + LenB(strOriginal)
        
        CopyMemory ByVal StrPtr(AppendStrings) + lngPosition, _
           ByVal StrPtr(varConcatString(i)), LenB(varConcatString(i))
        lngPosition = lngPosition + LenB(varConcatString(i))
     End If
  Next i
End Function

Public Function MIDAppendStrings( _
  strOriginal As String, _
  ParamArray varConcatString() As Variant) As String
   
  Dim i As Long
  Dim X As Long
  Dim lngTotal As Long
  Dim strBuffer As String
  Dim lngBufferSize As Long
  Dim lngLength As Long
  
  If IsArray(varConcatString) = False Then
      MIDAppendStrings = strOriginal
      Exit Function
  End If
  lngTotal = UBound(varConcatString)
  For i = 0 To lngTotal
     lngBufferSize = lngBufferSize + Len(varConcatString(i))
  Next i
  
  MIDAppendStrings = Space$(lngBufferSize + Len(strOriginal))
  Mid$(MIDAppendStrings, 1, Len(strOriginal)) = strOriginal
  lngBufferSize = Len(strOriginal) + 1
  
  For i = 0 To lngTotal
     lngLength = Len(varConcatString(i))
     If lngLength Then
       Mid$(MIDAppendStrings, lngBufferSize, lngLength) = _
           varConcatString(i)
       lngBufferSize = lngBufferSize + lngLength
     End If
  Next i
  
End Function

[/HIDE-THANKS]