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Working on Base-85 Encoder/Decoder Functions
#4
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SCREEN _NEWIMAGE(800, 600, 32)

FOR i = 0 TO 25 'Print A to Z, from the alphabet
    text$ = text$ + CHR$(65 + i)
    a$ = B256to128(text$)
    PRINT "B128: "; a$;
    LOCATE , 40
    b$ = B128to256(a$)
    PRINT "B256: "; b$
    SLEEP
NEXT
_DELAY 2
END

FUNCTION B256to128$ (text$)
    l = 8 * LEN(text$)
    DIM A(1 TO l) AS _UNSIGNED _BIT, b AS _UNSIGNED _BYTE
    'convert the text to the 8 bit array
    FOR i = 1 TO LEN(text$)
        b = ASC(text$, i)
        p = (i - 1) * 8 + 1
        FOR j = 0 TO 7
            IF b AND (2 ^ j) THEN A(p + j) = 1 ELSE A(p + j) = 0
        NEXT
    NEXT
    'convert the array to 7bit strings
    FOR i = 1 TO l STEP 7
        b = 0
        FOR j = 6 TO 0 STEP -1
            IF i + j < l THEN
                IF A(i + j) THEN b = b + (2 ^ j)
            END IF
        NEXT
        b = b + 45
        t$ = t$ + CHR$(b)
    NEXT
    IF LEN(t$) MOD 8 <> 0 AND RIGHT$(t$, 1) = "-" THEN t$ = LEFT$(t$, LEN(t$) - 1)
    B256to128 = t$
END FUNCTION

FUNCTION B128to256$ (text$)
    l = 7 * LEN(text$)
    DIM A(1 TO l) AS _UNSIGNED _BIT, b AS _UNSIGNED _BYTE
    'convert the text to the 8 bit array
    FOR i = 1 TO LEN(text$)
        b = ASC(text$, i) - 45
        FOR j = 0 TO 6
            p = p + 1: IF p > l THEN EXIT FOR
            IF b AND (2 ^ j) THEN A(p) = 1 ELSE A(p) = 0
        NEXT
    NEXT
    'convert the array to 8bit strings
    p = 0
    FOR i = 1 TO l STEP 8
        b = 0
        FOR j = 0 TO 7
            p = p + 1
            IF p > l THEN EXIT FOR
            IF A(p) THEN b = b + (2 ^ j)
        NEXT
        t$ = t$ + CHR$(b)
    NEXT
    B128to256 = t$
END FUNCTION
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Messages In This Thread
RE: Working on Base-85 Encoder/Decoder Functions - by SMcNeill - 09-23-2023, 04:00 AM



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