Connecting input iterator to output iterator

Ok, so I have this code:

Code:

template <typename Iter, typename Ins>
bit8_to_ASCII (Iter begin, Iter end, Ins output) {
   // Need this vector to hold intermediate values.
   std::vector<unsigned char> bit6;

   // Stretch the 8-bit values out to 6-bit values, store the result in vector bit6.
   bit8_to_bit6 (begin, end, std::back_inserter(bit6));

   // Translate the 6-bit values into ASCII values.  Store the output in the
   //   output stream.
   std::transform (bit6.begin(), bit6.end(), output, bit6_to_ASCII);

   return;
}

Conceptually... vector bit6 is really not needed. It's just an artifact of the problem that I can't start std::transform until after the bit8_to_bit6 function is done. Is there some kind of inserter-wrapper I can use to take it out of the picture? Something like this maybe:

Code:

template <typename Iter, typename Ins>
bit8_to_ASCII (Iter begin, Iter end, Ins output) {
   // No need to allocate an intermediate vector

   // Whenever something is output to transforming_inserter, it calls bit6_to_ASCII
   //   on the input, and stores the result in output.
   SOME_TYPE transforming_inserter = SOME_FUNCTION(output, bit6_to_ASCII);

   // Stretch the 8-bit values out to 6-bit values, store the result in 
   //   the custom inserter which will perform bit6_to_ASCII on the fly.
   bit8_to_bit6 (begin, end, transforming_inserter);

   return;
}

have a look at the boost.iterators library. I haven't used it much myself, but I think transform_iterator might be able to help you.

transform_iterator does 1:1 transformations. I don't think there's a proper pre-made iterator for your purposes. It's not that hard to write one, though. Using the Boost.Iterators facade, you can cook up an iterator pretty quickly. You should have some experience in writing easier iterators first, though.