class Rack::Multipart::Parser

def consume_boundary

boundary, clear the buffer and return nil.
end of the boundary. If we don't find the start or end of the
If we find it, return the appropriate symbol for the start or
Scan until the we find the start or end of the boundary. 
def consume_boundary
  if read_buffer = @sbuf.scan_until(@body_regex)
    read_buffer.end_with?(EOL) ? :BOUNDARY : :END_BOUNDARY
  else
    @sbuf.terminate
    nil
  end
end