Print #2, "Function BASFILE$()"

Print #2, "    DIM A$, c$, o$, btemp$, a&, j&, p&, oc&, i as _Unsigned Long, v as _Unsigned Long"

'==========

'BASE91.BAS

'==========

'Base-91 Encoder/Decoder Functions.

'Coded by Dav for QB64-PE 3.8.0, SEP/2023

'(adpated from sources found on the web)



'NOTE: This uses a modified Base-91 character set so code output doesn't

'include symbols that conflict with the QB64-PE forum message posting.



'Unlike Base64 & Base85, Base91 space efficiency changes according to input.

'It is somewhere near 23% percent added to the input source, a wee bit better

'than Base85 which is 25% more, and much better than Base64 which is 33%. 



Screen 12



_ControlChr Off



Do

    Cls

    Color 15, 1: Print "Checking bytes loop -- Hit any key to stop checking ..."

    a$ = ""

    Print

    Color 7, 0: Print "Original:"

    bytes = 200 + Int(Rnd * 55)

    For i = 0 To bytes

        a$ = a$ + Chr$(Int(Rnd * 255))

    Next

    Print a$

    Print Len(a$); "bytes"



    Print

    Print "Encoded:"

    a2$ = Base91Encode$(a$): Print a2$

    Print Len(a2$); "bytes"

    Print

    Print "Decoded:"

    a3$ = Base91Decode$(a2$): Print a3$

    Print Len(a3$); "bytes"

    Print



    If Len(a$) <> Len(a3$) Then Color 12, 0: Print "Size don't match!"; t: End

    If a$ <> a3$ Then Color 12, 0: Print "Bytes don't match!"; t: End

    _Display



    _Limit 15



    If _KeyHit Then Exit Do



    loopcount = loopcount + 1

    bytecount = bytecount + bytes



Loop



Print "Checked"; loopcount; "loops of"; bytecount; "bytes."

Print "No errors detected."

End



Function Base91Encode$ (in$)



    'Build 91 characters to use

    For i = 33 To 126

        If i <> 34 And i <> 64 And i <> 96 Then Chars$ = Chars$ + Chr$(i)

    Next



    For i& = 1 To Len(in$)

        bits = (bits Or (Asc(Mid$(in$, i&, 1)) * (2 ^ nbits)))

        nbits = nbits + 8

        If nbits > 13 Then

            value = bits Mod 8192

            If value > 88 Then

                bits = (bits \ (2 ^ 13))

                nbits = nbits - 13

            Else

                value = bits Mod 16384

                bits = (bits \ (2 ^ 14))

                nbits = nbits - 14

            End If

            out$ = out$ + Mid$(Chars$, (value Mod 91) + 1, 1) + Mid$(Chars$, (value \ 91) + 1, 1)

        End If

    Next



    If nbits > 0 Then

        out$ = out$ + Mid$(Chars$, (bits Mod 91) + 1, 1)

        If nbits > 7 Or bits > 90 Then

            out$ = out$ + Mid$(Chars$, (bits \ 91) + 1, 1)

        End If

    End If



    Base91Encode$ = out$



End Function







Function Base91Decode$ (in$)

    'Build 91 characters to use

    For i = 33 To 126

        If i <> 34 And i <> 64 And i <> 96 Then Chars$ = Chars$ + Chr$(i)

    Next

    value = -1

    For i& = 1 To Len(in$)

        ascii = InStr(Chars$, Mid$(in$, i&, 1)) - 1

        If value < 0 Then

            value = ascii

        Else

            value = value + (ascii * 91)

            bits = bits Or _ShL(value, nbits)

            nbits = nbits + 13 + (((value And 8191) <= 88) * -1)

            Do Until (nbits > 7) = 0

                out$ = out$ + Chr$(bits And 255)

                bits = _ShR(bits, 8)

                nbits = nbits - 8

            Loop

            value = -1

        End If

    Next



    If (value + 1) Then

        out$ = out$ + Chr$((bits Or _ShL(value, nbits)) And 255)

    End If



    Base91Decode$ = out$



End Function