Re: [Boost-users] Re: base64->wstring decoding

From: Stefan Strasser (sstrasser_at_[hidden])
Date: 2005-03-11 19:26:29

Robert Ramey schrieb:
> So your case might be altered to interate not on the input characters but
> rather on the output

Thanks!
iterating on output works. in case someone else on the list is 
interested, below's the code.

> a) i notices you're using a 32 bit wchar_t - note that this is non-portable.
> I would think about using std::vector<boost::int_least32>. or maybe instead
> of using the "magic" number 32 you might want to try something like
> (sizeof(wchar_t) * 8).

32: yes, I've sent example code.
int_least32: wstring/wchar_t is ok, it's a representation of a c++ wide 
string literal. (google for "metac++" for a reason)

> 
> b) I'm not sure I remember where I handled the padding.  you should double
> check that your if your original binary string isn't modulo 6 bits you might
> find it filled with 0 after a round trip through base64.

I'm not sure what you mean here, how can an unencoded string whose CharT 
is always > 6 bits be filled with 0 after round trip? base64 can, and 
that's fine.

thanks again!

typedef 
transform_width<binary_from_base64<std::string::const_iterator>,sizeof(wchar_t)*8,6> 
base64;
   std::size_t destsize=enc.size() * 6 / (8 * sizeof(wchar_t));
   tthis->resize(destsize);
   base64 it(enc.begin());
   for(unsigned int c=0;c<destsize;++c,++it) (*this)[c]=*it;

--
> 
> Robert Ramey
> 
> Stefan Strasser wrote:
> 
>>Hi,
>>
>>I need to write a std::wstring which can contain binary data like \0
>>to a xml attribute, so I'm converting it to base64 but I have problems
>>decoding it:
>>std::copy(decode(in.begin()),decode(in.end()),);
>>
>>is this a correct way to decode base64?
>>it works, but only if (bits % 6 == 0).
>>otherwise the program is abort()ed due to an exception.
>>
>>the string was encoded by
>>base64_from_binary<transform_width<std::wstring::const_iterator,6,32>
>>
>>Thanks,
> 
> 
> 
> 
> 
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> 
-- 
Stefan Strasser