convert_json_to_yaml

# File activesupport/lib/active_support/json/decoding.rb, line 22
        def convert_json_to_yaml(json) #:nodoc:
          scanner, quoting, marks, pos, times = StringScanner.new(json), false, [], nil, []
          while scanner.scan_until(/(\\['"]|['":,\\]|\\.)/)
            case char = scanner[1]
            when '"', "'"
              if !quoting
                quoting = char
                pos = scanner.pos
              elsif quoting == char
                if json[pos..scanner.pos-2] =~ DATE_REGEX
                  # found a date, track the exact positions of the quotes so we can remove them later.
                  # oh, and increment them for each current mark, each one is an extra padded space that bumps
                  # the position in the final YAML output
                  total_marks = marks.size
                  times << pos+total_marks << scanner.pos+total_marks
                end
                quoting = false
              end
            when ":",","
              marks << scanner.pos - 1 unless quoting
            end
          end

          if marks.empty?
            json.gsub(/\\([\\\/]|u[[:xdigit:]]{4})/) do
              ustr = $1
              if ustr.starts_with?('u')
                [ustr[1..-1].to_i(16)].pack("U")
              elsif ustr == '\\'
                '\\\\'
              else
                ustr
              end
            end
          else
            left_pos  = [-1].push(*marks)
            right_pos = marks << scanner.pos + scanner.rest_size
            output    = []
            left_pos.each_with_index do |left, i|
              scanner.pos = left.succ
              output << scanner.peek(right_pos[i] - scanner.pos + 1).gsub(/\\([\\\/]|u[[:xdigit:]]{4})/) do
                ustr = $1
                if ustr.starts_with?('u')
                  [ustr[1..-1].to_i(16)].pack("U")
                elsif ustr == '\\'
                '\\\\'
                else
                  ustr
                end
              end
            end
            output = output * " "
            
            times.each { |i| output[i-1] = ' ' }
            output.gsub!(/\\\//, '/')
            output
          end
        end