Re: [boost] base64 filter works incorrect if sorce string length % 3 != 0

From: Robert Ramey (ramey_at_[hidden])
Date: 2008-07-14 12:54:18

I struggled with this issue regarding base64 when I made the serialization 
library.
I never felt I found the right way to address it.  I did manage
to address in the serialization library by reading only thie required 
characters.
Unfortunately, I think the current implemetation also breaks more iterator
rules than it should.

So I would like to see a clean fix for this to make it useful as
a more general purpose tool.

I hadn't thought of a padding filter - maybe that's a worthy idea.

So I havn't got a lot more to say about this for now.

Robert Ramey

????? ???????? wrote:
> Hello,
> I have the following code:
>
> #include <boost/archive/iterators/binary_from_base64.hpp>
> #include <boost/archive/iterators/base64_from_binary.hpp>
> #include <boost/archive/iterators/insert_linebreaks.hpp>
> #include <boost/archive/iterators/remove_whitespace.hpp>
> #include <boost/archive/iterators/transform_width.hpp>
>
> #include <string>
> #include <exception>
> #include <iostream>
>
> int main()
> {
> using namespace boost::archive::iterators;
>
> typedef
> insert_linebreaks<
> base64_from_binary<
> transform_width< std::string::const_iterator, 6, sizeof( char ) * 8 >
>> ,72
>> to_base64_type;
>
> typedef
> transform_width<
> binary_from_base64<
> remove_whitespace< std::string::const_iterator >
>> ,  sizeof( char ) * 8, 6
>> to_binary_type;
>
> std::string hello_ = "hello";
>
> std::string base64_hello_( to_base64_type( hello_.begin() )
> , to_base64_type( hello_.end() ) );
>
> std::cout << base64_hello_ << std::endl;
>
> try
> {
> std::string hello_recovered_( to_binary_type( base64_hello_.begin() )
> , to_binary_type( base64_hello_.end() ) );
>
> std::cout << hello_recovered_ << std::endl;
> }
> catch ( const std::exception& e_ )
> {
> std::cerr << e_.what() << std::endl;
> }
>
> return 0;
> }
>
> During base64 decode we have following exception: "attempt to decode
> a value not in base64 char set".
> We have the problem because source string hello_ = "hello", has
> length % 3 != 0, otherwise we don't have this exception.
> As I know in this case we should add appropriate number of special
> symbol like '='.
> I can add '=' manually, but boost base64 decode can't process them,
> and we also have exception
>
> If we have insert_linebreaks/remove_whitespace filter perhaps we also
> should have some symmetric filter for text padding? Do we have
> padding filter in boost? Or perhaps it will be in future?
>
> Thanks
>
>
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