Working on Base-85 Encoder/Decoder Functions

[SMcNeill]

Try this version @Dav :

Code: (Select All)

_CONTROLCHR OFF







test$ = "abc"

a$ = B256to128$(test$)

b$ = B128to256$(a$)

PRINT test$, a$, b$

PRINT LEN(test$), LEN(a$), LEN(b$)



SLEEP



FOR i = 0 TO 255

    t$ = CHR$(i)

    PRINT i, t$,

    a$ = B256to128(t$)

    PRINT a$,

    b$ = B128to256(a$)

    PRINT b$

    IF t$ <> b$ THEN

        PRINT "DON'T MATCH!!"

        END

    END IF

NEXT



PRINT

PRINT "All characters match before and after encoding and decoding."







FUNCTION B256to128$ (text$)

    FOR i = 1 TO LEN(text$)

        a = ASC(text$, i) '                      get the ASCII value of our character

        b$ = RIGHT$("00000000" + _BIN$(a), 8) '  convert it to binary

        temp$ = temp$ + b$ '                      add the binary to a single long string

    NEXT

    padding$ = STRING$(7 - LEN(temp$) MOD 7, "0")

    temp$ = temp$ + padding$ '                    add necessay padding to make it suitable for base-128 encoding

    FOR i = 1 TO LEN(temp$) STEP 7

        c$ = MID$(temp$, i, 7) '                  get 7 characters from our 8 byte represention

        c = VAL("&B" + c$) '                      that's the character value of our base 128-character

        temp1$ = temp1$ + CHR$(c + 65) '              add that to our new string

    NEXT

    B256to128$ = temp1$

END FUNCTION



FUNCTION B128to256$ (text$)

    FOR i = 1 TO LEN(text$)

        a = ASC(text$, i) - 65

        b$ = RIGHT$("0000000" + _BIN$(a), 7)

        temp$ = temp$ + b$

    NEXT

    temp$ = LEFT$(temp$, 8 * INT(LEN(temp$) / 8)) 'remove padding

    FOR i = 1 TO LEN(temp$) STEP 8

        b$ = "&B" + MID$(temp$, i, 8)

        temp1$ = temp1$ + CHR$(VAL(b$))

    NEXT

    B128to256$ = temp1$

END FUNCTION

I tried to change and simplify the process as much as possible here.  From the initial testing, all seems to be working now as it should, without that stray "0" popping up from time to time and biting you in the hiney.  

Try it out and let me know if it works as advertised, or not, for you.