Pathname identifying location of buffer .
An external format spec.
A buffer whose contents are examined.
Length (an integer) up to which buffer should be examined.
A new external format spec created by merging ef-spec with the Japanese encoding that was found.
Assume the encoding is one of :jis
, :sjis
, :euc
, :unicode
and :ascii
, and try to determine which of these it is, by looking for distinctive byte sequences in buffer up to length . If found, merge ef-spec with that encoding.