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This code sample shows how to convert UTF-8 byte sequences (aka code page 65001) into unicode strings and back again in Visual Basic 6 instead of .Net like most of the examples I could find. What's more, this sample does not use APIs, but instead, relies on the Stream object provided by the ADODB library. This may not be the most efficient way of doing it, but these functions can be easily ported to Classic ASP by dropping all the variable types. For this code to work, you will need to add a reference to the Microsoft ActiveX Data Objects 2.5 Library later versions of this library will also work. The first function converts a unicode string to a byte array: |
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' accept a byte array containing utf-8 data ' and convert it to a string Public Function ConvertStringToUtf8Bytes(ByRef strText As String) As Byte() Dim objStream As ADODB.Stream Dim data() As Byte ' init stream Set objStream = New ADODB.Stream objStream.Charset = "utf-8" objStream.Mode = adModeReadWrite objStream.Type = adTypeText objStream.Open ' write bytes into stream objStream.WriteText strText objStream.Flush ' rewind stream and read text objStream.Position = 0 objStream.Type = adTypeBinary objStream.Read 3 ' skip first 3 bytes as this is the utf-8 marker data = objStream.Read() ' close up and return objStream.Close ConvertStringToUtf8Bytes = data End FunctionThis second function does the opposite, converting a byte array into a unicode string:
' accept a byte array containing utf-8 data ' and convert it to a string Public Function ConvertUtf8BytesToString(ByRef data() As Byte) As String Dim objStream As ADODB.Stream Dim strTmp As String ' init stream Set objStream = New ADODB.Stream objStream.Charset = "utf-8" objStream.Mode = adModeReadWrite objStream.Type = adTypeBinary objStream.Open ' write bytes into stream objStream.Write data objStream.Flush ' rewind stream and read text objStream.Position = 0 objStream.Type = adTypeText strTmp = objStream.ReadText ' close up and return objStream.Close ConvertUtf8BytesToString = strTmp End FunctionThis test method uses a function called DecodeBase64 which is defined in this article: Free, Easy and Quick Base64 Encoding and Decoding in Visual Basic.
Public Sub Main() Dim strB64 As String Dim data() As Byte Dim strTmp As String ' define test data as base64 and decode to array of bytes strB64 = "R3JlZXRpbmdzIGFuZCBTYWx1dGF0aW9uISAo4oKsKSBhbmQgc29" strB64 = strB64 & "tZSBVcmR1OiDaqdix2KfahtuMINm+2Kfaqdiz2KrYp9mG24w=" data = DecodeBase64(strB64) ' convert from utf-8 to string strTmp = ConvertUtf8BytesToString(data) ' convert back to bytes data = ConvertStringToUtf8Bytes(strTmp) End SubPlease note that the VB6 IDE and the standard VB6 form controls have difficulty showing Unicode characters and will show exotic characters as '?????'
The code from this article can be download as a VB6 project here: NonHostile_VB6_Convert_UTF8.zip
Hope this helps :-)
1033 comments,
Visual Basic 6, Thursday, January 26, 2006 21:51
