class Sinatra::Helpers::StaticFile

def parse_ranges(env, size)

Returns false if the ranges are unsatisfiable and the request should return 416.
Checks for byte-ranges in the request and sets self.range appropriately. 
def parse_ranges(env, size)
  #r = Rack::Utils::byte_ranges(env, size)  # TODO: not available yet in released Rack
  r = byte_ranges(env, size)
  return false if r == []  # Unsatisfiable; report error
  @range = r[0] if r && r.length == 1  # Ignore multiple-range requests for now
  return true
end