LB code for converting to/from Base85.

base85.bas

str$ = Base85Encode$("testing")
print str$
print Base85Decode$(str$)
print
str$ = Z85Encode$("testing")
print str$
print Z85Decode$(str$)

Function Base85Encode$(dat$)
    ascii85$ = "!" + chr$(34) + "#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstu"

    Base85Encode$ = B85EncodeWithCode$(dat$, ascii85$)
End Function

Function Base85Decode$(dat$)
    ascii85$ = "!" + chr$(34) + "#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstu"

    Base85Decode$ = B85DecodeWithCode$(dat$, ascii85$)
End Function

Function Z85Encode$(dat$)
    Z85$ = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#"

    Z85Encode$ = B85EncodeWithCode$(dat$, Z85$)
End Function

Function Z85Decode$(dat$)
    Z85$ = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#"

    Z85Decode$ = B85DecodeWithCode$(dat$, Z85$)
End Function

Function B85EncodeWithCode$(dat$, encoding$)
    datLenMod = len(dat$) mod 4
    if datLenMod then padding = 4 - datLenMod

    for x = 1 to padding
        dat$ = dat$ + chr$(0)
    next x

    For x = 1 to len(dat$) step 4
        temp$ = mid$(dat$, x, 4)

        For y = 1 to 4
            conv = (conv * 256) + asc(mid$(temp$, y, 1))
        Next y

        while conv > 0
            char = (conv mod 85) + 1
            chunk$ = mid$(encoding$, char, 1) + chunk$
            conv = int(conv / 85)
        wend

        B85EncodeWithCode$ = B85EncodeWithCode$ + chunk$
        chunk$ = ""
    Next x

    B85EncodeWithCode$ = left$(B85EncodeWithCode$, len(B85EncodeWithCode$) - padding)
End Function

Function B85DecodeWithCode$(dat$, encoding$)
    padChr$ = right$(encoding$, 1)

    datLenMod = len(dat$) mod 5
    if datLenMod then padding = 5 - datLenMod

    For x = 1 to padding
        dat$ = dat$ + padChr$
    next x

    For x = 1 to len(dat$) step 5
        temp$ = mid$(dat$, x, 5)

        For y = 1 to 5
            t$ = mid$(temp$, y, 1)
            conv = (conv * 85) + (instr(encoding$, t$) - 1)
        Next y

        while conv > 0
            char = conv mod 256
            chunk$ = chr$(char) + chunk$
            conv = int(conv / 256)
        wend

        B85DecodeWithCode$ = B85DecodeWithCode$ + chunk$
        chunk$ = ""
    Next x

    B85DecodeWithCode$ = left$(B85DecodeWithCode$, len(B85DecodeWithCode$) - padding)
End Function