class Fluent::Plugin::Buffer::FileChunk

def self.assume_chunk_state(path)
  if /\.(b|q)([0-9a-f]+)\.[^\/]*\Z/n =~ path # //n switch means explicit 'ASCII-8BIT' pattern
    $1 == 'b' ? :staged : :queued
  else
    # files which matches to glob of buffer file pattern
    # it includes files which are created by out_file
    :unknown
  end
end