convert_input (Erubis::PI::Converter)

    # File lib/erubis/converter.rb, line 231
        def convert_input(codebuf, input)
          unless @regexp
            @pi ||= 'e'
            ch = Regexp.escape(@embchar)
            if @pattern
              left, right = @pattern.split(' ')
              @regexp = /<\?#{@pi}(?:-(\w+))?(\s.*?)\?>([ \t]*\r?\n)?|#{ch}(!*)?\{(.*?)\}#{ch}|#{left}(=+)(.*?)#{right}/m
            else
              @regexp = /<\?#{@pi}(?:-(\w+))?(\s.*?)\?>([ \t]*\r?\n)?|#{ch}(!*)?\{(.*?)\}#{ch}/m
            end
          end
          #
          is_bol = true
          pos = 0
          input.scan(@regexp) do |pi_arg, stmt, rspace,
                                  indicator1, expr1, indicator2, expr2|
            match = Regexp.last_match
            len = match.begin(0) - pos
            text = input[pos, len]
            pos = match.end(0)
            lspace = stmt ? detect_spaces_at_bol(text, is_bol) : nil
            is_bol = stmt && rspace ? true : false
            add_text(codebuf, text) # unless text.empty?
            #
            if stmt
              if @trim && lspace && rspace
                add_pi_stmt(codebuf, "#{lspace}#{stmt}#{rspace}", pi_arg)
              else
                add_text(codebuf, lspace) if lspace
                add_pi_stmt(codebuf, stmt, pi_arg)
                add_text(codebuf, rspace) if rspace
              end
            else
              add_pi_expr(codebuf, expr1 || expr2, indicator1 || indicator2)
            end
          end
          #rest = $' || input                        # ruby1.8
          rest = pos == 0 ? input : input[pos..-1]   # ruby1.9
          add_text(codebuf, rest)
        end