Re: [boost] [serialization] Base64 padding in basic_text_oprimitive

From: Robert Ramey (ramey_at_[hidden])
Date: 2008-06-09 12:40:44

Hmmm - I wasn't aware that base64 had a "principle" that output
length is a multiple of 4 bytes.

You could be on ot something here, I'll take another look at it.
Vyacheslav E. Andrejev wrote:
> Hello,
>
> Code that pads base64 output with '=' looks in
> basic_text_oprimitive.ipp like following:
>
>    std::size_t padding = 2 - count % 3;
>    if(padding > 1)
>        *oi = '=';
>        if(padding > 2)
>            *oi = '=';
>
> It will give the following transformations of a few simple strings:
>
> "012" -> "MDEy="
> "0123" -> "MDEyMw"
> "01234" -> "MDEyMzQ"
> "012345" -> "MDEyMzQ1="
>
> Which violates the principle of the base 64 that the encoded output
> length is multiple of 4 bytes. Right output for the samples above
> should be:

>
> "012" -> "MDEy"
> "0123" -> "MDEyMw=="
> "01234" -> "MDEyMzQ="
> "012345" -> "MDEyMzQ1"
>
>
> The problem with the code above is that the condition (padding > 2)
> is never satisfied. I think that the proper code should look like
>
>        std::size_t padding = 2 - count % 3;
>        if (padding < 2) {
>          *oi = '=';
>          if (padding > 0)
>            *oi = '=';
>        }