Re: [Boost-bugs] [Boost C++ Libraries] #5629: base64 encode/decode for std::istreambuf_iterator/std::ostreambuf_iterator

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #5629: base64 encode/decode for std::istreambuf_iterator/std::ostreambuf_iterator
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-09-07 11:28:05

#5629: base64 encode/decode for std::istreambuf_iterator/std::ostreambuf_iterator
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  Reporter:  nen777w@…         |      Owner:  ramey
      Type:  Bugs              |     Status:  assigned
 Milestone:  To Be Determined  |  Component:  serialization
   Version:  Boost 1.45.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+---------------------------

Comment (by prantlf@…):

 The problem of padding could be solved by making the transform_width
 stateful.  If you want to encode/decode to/from BASE64 and you input comes
 in chunks or as a stream, you need to save your previous state to be able
 to continue with the next chunk correctly.

 The transform_width currently goes "blindly" for the next item pointed to
 by the iterator, although there may not be enough items to finish the
 minimum quantum.  It even ends up with buffer overflow, if your input
 sequence is not zero-padded.  Also, this eager reading of the zero padding
 makes it useful only to convert once a complete buffer.

 Having the transform_width "know" that there is a minimum quantum of units
 to read which has to be available to produce an output unit, it would
 prevent the buffer overflow and allow transforming chunked input.

 I added the end-iterator and state to the transform_width (either directly
 or to the transformed iterator by an iterator adaptor).  Reading ahead and
 storing the next value makes the code a little longer and note so compact.
 Also, tt runs significantly slower than a hand-coded BASE64 encoder; I\m
 nor sure why. Maybe copying of the iterators around?

 Would it make sense to include a stateful transform_width in boost?

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5629#comment:10>
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