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    base64 byte-length formula



    I don't particularly care, but the formula given
    on page 71 of 12-98 is wrong (and I've mentioned
    it a few times already).
    
    A very simple counterexample:
    
    0 base64 digits should result in a 0-byte binary
    string. According to the given formula, 
    floor((0 + 3) * 3 / 4) - 0) = 2.
    
    Another, more realistic but just as simple one:
    
    4 base64 digits should result in a 3-byte binary
    string. According to the given formula,
    floor((4 + 3) * 3 / 4) - 0) = 5.
    
    The given formula also fails for n = 3 (mod 4).
    
    The correct formula, IMO is the following:
    floor(n * 3 / 4).
    
    In other words, there is no need to even count
    the equivalence signs at the end, nor to add
    any constants.
    
    Martins Krikis, Intel Corp.
    
    Disclaimer: these opinions are mine and may
                not be my employer's.
    
    
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Last updated: Sun Jun 30 02:19:01 2002
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