select_best_encoding (lib/rack/utils.rb)

# File lib/rack/utils.rb, line 246
    def select_best_encoding(available_encodings, accept_encoding)
      # http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html

      expanded_accept_encoding =
        accept_encoding.map { |m, q|
          if m == "*"
            (available_encodings - accept_encoding.map { |m2, _| m2 }).map { |m2| [m2, q] }
          else
            [[m, q]]
          end
        }.inject([]) { |mem, list|
          mem + list
        }

      encoding_candidates = expanded_accept_encoding.sort_by { |_, q| -q }.map { |m, _| m }

      unless encoding_candidates.include?("identity")
        encoding_candidates.push("identity")
      end

      expanded_accept_encoding.each { |m, q|
        encoding_candidates.delete(m) if q == 0.0
      }

      return (encoding_candidates & available_encodings)[0]
    end