lzw_encoder.tpp

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#include <map>

/*----------------------------------------------------------------------------*/
template<typename InputBuffer, typename OutputBuffer>
void claw::lzw_encoder<InputBuffer, OutputBuffer>::encode
( input_buffer_type& input, output_buffer_type& output ) const
{
  typedef std::pair<unsigned int, unsigned int> word;

  if ( !input.end_of_data() )
    {
      std::map<word, unsigned int> table;
      
      unsigned int symbol = input.get_next();
      unsigned int prefix_code = symbol;
      unsigned int next_code = input.symbols_count();

      while ( !input.end_of_data() && (next_code != output.max_code()) )
        {
          symbol = input.get_next();

          word new_word(prefix_code, symbol);

          if ( table.find(new_word) != table.end() )
            prefix_code = table[new_word];
          else
            {
              output.write(prefix_code);
              output.new_code(next_code);
              table[new_word] = next_code;
              prefix_code = symbol;

              ++next_code;
            }
        }

      output.write(prefix_code);
    }
} // lzw_encoder::encode()