MIME-Kodierung (base64)

Auch die Erzeugung von MIME-Strings ist ganz einfach:
     mime$ = base64_encode$("Visual Basic")

Const base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" Function base64_encode$(a$) c$ = "" For n% = 1 To Len(a$) Step 3 c1% = Asc(Mid$(a$, n%, 1)) c2% = Asc(Mid$(a$, n% + 1, 1) + Chr$(0)) c3% = Asc(Mid$(a$, n% + 2, 1) + Chr$(0)) w1% = Int(c1% / 4) w2% = (c1% And 3) * 16 + Int(c2% / 16) If Len(a$) >= n% + 1 Then w3% = (c2% And 15) * 4 + Int(c3% / 64) Else w3% = -1 If Len(a$) >= n% + 2 Then w4% = c3% And 63 Else w4% = -1 c$ = c$ + mimeencode$(w1%) + mimeencode$(w2%) + mimeencode$(w3%) + mimeencode$(w4%) Next base64_encode$ = c$ End Function Function base64_decode$(a$) c$ = "" For n% = 1 To Len(a$) Step 4 w1% = mimedecode%(Mid$(a$, n%, 1)) w2% = mimedecode%(Mid$(a$, n% + 1, 1)) w3% = mimedecode%(Mid$(a$, n% + 2, 1)) w4% = mimedecode%(Mid$(a$, n% + 3, 1)) If w2% >= 0 Then c$ = c$ + Chr$(((w1% * 4 + Int(w2% / 16)) And 255)) If w3% >= 0 Then c$ = c$ + Chr$(((w2% * 16 + Int(w3% / 4)) And 255)) If w4% >= 0 Then c$ = c$ + Chr$(((w3% * 64 + w4%) And 255)) Next base64_decode$ = c$ End Function Private Function mimeencode$(w%) If w% >= 0 Then mimeencode$ = Mid$(base64, w% + 1, 1) Else mimeencode$ = "" End Function Private Function mimedecode%(a$) If Len(a$) = 0 Then mimedecode% = -1: Exit Function mimedecode% = InStr(base64, a$) - 1 End Function

Vollständigkeitshalber auch die Algorithmen für "quoted printable":

Function quotedprintable_encode$(a$) b$ = "" For n% = 1 To Len(a$) If Asc(Mid$(a$, n%, 1)) < 16 Then b$ = b$ + "=0" + Hex$(Asc(Mid$(a$, n%, 1))) ElseIf Asc(Mid$(a$, n%, 1)) < 32 Or Asc(Mid$(a$, n%, 1)) > 126 Or Mid$(a$, n%, 1) = "=" Then b$ = b$ + "=" + Hex$(Asc(Mid$(a$, n%, 1))) Else b$ = b$ + Mid$(a$, n%, 1) End If Next quotedprintable_encode$ = b$ End Function Function quotedprintable_decode$(ByVal a$) f% = 0 Do f% = InStr(f% + 1, a$, "=") If f% = 0 Or f% > Len(a$) - 2 Then Exit Do a$ = Left$(a$, f% - 1) + Chr$(Val("&H" + Mid$(a$, f% + 1, 2))) + Mid$(a$, f% + 3) Loop quotedprintable_decode$ = a$ End Function