convert_json_to_yaml

# File activesupport/lib/active_support/json/backends/yaml.rb, line 29
          def convert_json_to_yaml(json) #:nodoc:
            require 'strscan' unless defined? ::StringScanner
            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 valid_date?(json[pos..scanner.pos-2])
                    # found a date, track the exact positions of the quotes so we can
                    # overwrite them with spaces later.
                    times << pos
                  end
                  quoting = false
                end
              when ":",","
                marks << scanner.pos - 1 unless quoting
              when "\\"
                scanner.skip(/\\/)
              end
            end

            if marks.empty?
              json.gsub(/\\([\\\/]|u[[:xdigit:]]{4})/) do
                ustr = $1
                if ustr.start_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
                chunk = scanner.peek(right_pos[i] - scanner.pos + 1)
                # overwrite the quotes found around the dates with spaces
                while times.size > 0 && times[0] <= right_pos[i]
                  chunk.insert(times.shift - scanner.pos - 1, '! ')
                end
                chunk.gsub!(/\\([\\\/]|u[[:xdigit:]]{4})/) do
                  ustr = $1
                  if ustr.start_with?('u')
                    [ustr[1..-1].to_i(16)].pack("U")
                  elsif ustr == '\'
                    '\\'
                  else
                    ustr
                  end
                end
                output << chunk
              end
              output = output * " "

              output.gsub!(/\\\//, '/')
              output
            end
          end