base64编码（vb6邮件附件）

'Author: Eva 'Date: 2009/09/09 'Function: Encode email attachment with base64 ''''''''' '对一个文件进行base64 编码，并返回一个字符串 'base64 即把3个8位的字节转换成4个6位的字节 Option Explicit Const B64Dic = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" '编程词典 Public Function EncodeFileToBase64(strFileName As String) As String Dim strEncoded As String Dim Buffer As Byte Dim FileLength As Long Dim intWS As Integer Dim intStart As Long Dim lngTmp As Long Dim strOut As String Dim intEnd As Long Buffer = 0 strEncoded = "" FileLength = FileLen(strFileName) intWS = FileLength Mod 3 intEnd = FileLength - intWS Open strFileName For Binary Access Read As #1 '读取24位3字节的信息 For intStart = 1 To intEnd Step 3 Get #1, , Buffer lngTmp = CLng(Buffer) * 65536 '左移16位 Get #1, intStart + 1, Buffer lngTmp = lngTmp + CLng(Buffer) * 256 '左移8位 Get #1, intStart + 2, Buffer lngTmp = lngTmp + CLng(Buffer) '转换为64编码 strOut = strOut & Mid$(B64Dic, ((lngTmp And &HFC0000) / 262144) + 1, 1)'右移18位 If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & Mid$(B64Dic, ((lngTmp And &H3F000) / 4096) + 1, 1)'右移12位 If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & Mid$(B64Dic, ((lngTmp And &HFC0) / 64) + 1, 1)'右移6位 If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & Mid$(B64Dic, ((lngTmp And &H3F) + 1), 1) If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If Next '处理结尾信息 If intWS = 1 Then Get #1, FileLength, Buffer lngTmp = CLng(Buffer) * 65536 strOut = strOut & Mid$(B64Dic, ((lngTmp And &HFC0000) / 262144) + 1, 1) If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & Mid$(B64Dic, ((lngTmp And &H3F000) / 4096) + 1, 1) If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & "==" strEncoded = strEncoded & strOut ElseIf intWS = 2 Then Get #1, FileLength - 1, Buffer lngTmp = CLng(Buffer) * 65536 Get #1, FileLength, Buffer lngTmp = lngTmp + CLng(Buffer) * 256 strOut = strOut & Mid$(B64Dic, ((lngTmp And &HFC0000) / 262144) + 1, 1) If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & Mid$(B64Dic, ((lngTmp And &H3F000) / 4096) + 1, 1) If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & Mid$(B64Dic, ((lngTmp And &HFC0) / 64) + 1, 1) If Len(strOut) = 76 Then strEncoded = strEncoded & strOut strOut = "" End If strOut = strOut & "=" strEncoded = strEncoded & strOut End If strEncoded = strEncoded & strOut Close #1 '返回编码结果 EncodeFileToBase64 = strEncoded End Function