Sergey escreveu:
Thanks for suggestion. My crypt_something class meant to be streamed but i failed to describe it. crypt_something is buffered 'processor' and user can call process() several time example: crypt_something cs; cs.init(encryption_key); ... while (!input_stream.eof()) { in_buffer = input_stream.read(); //reading to buffer from input stream size_t outsize = cs.process_outsize(in_buffer.begin(), in_buffer.end()); //determining //amount of memory we will need to write output if (out_buffer.size() < outsize) out_buffer.resize(outsize); stream_buffer::iterator it = cs.process(in_buffer.begin(), in_buffer.end(), out_buffer.begin()); out_stream.write(out_buffer.begin(), it); } //flushing buffer size_t outsize = cs.flush_outsize<stream_buffer::item_type>(); if (out_buffer.size() < outsize) out_buffer.resize(outsize); stream_buffer::iterator it = cs.flush(out_buffer.begin()); out_stream.write(out_buffer.begin(), it);
It is written in some kind of pseudo-code but i hope it is clear enough now :)
I think it is inproper to begin with "streams". "Streams" imply a source of data and that is irrelevant from a cipher's point of view. I'd recommend thinking in terms of algorithm as in <algorithm> -- operations on pairs of iterators or ranges. Something basic along the lines of: /** * pre-condition: distance(begin, end) == cipher's block size. */ template <typename InputIterator, typename OutputIterator> OutputIterator cipher_update (InputIterator begin, InputIterator end, OutputIterator out); /** * no precondition as above: padding as necessary. */ template <typename InputIterator, typename OutputIterator> OutputIterator cipher_finalize (InputIterator begin, InputIterator end, OutputIterator out); These generic algorithms could be specialized through "tag dispatching" as always to increase performance for special cases. -- Pedro Lamarão