Mime_types
Database of file extensions to MIME types from RFC2045 onwards.
map_extension ~default e
converts the file extension e
into a MIME type, defaulting to default
(which is application/octet-stream
by default) if it is unknown.
map_file ~default f
converts the filename f
into a MIME type, defaulting to default
(which is application/octet-stream
by default) if it is unknown.