MIME Content Type for BinHex Encoded Files
RFC 1741

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Network Working Group                                       P. Faltstrom
Request for Comments: 1741                 Royal Institute of Technology
Category: Informational                                       D. Crocker
                                                  Brandenburg Consulting
                                                                 E. Fair
                                                     Apple Computer Inc.
                                                           December 1994

               MIME Content Type for BinHex Encoded Files

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   This memo describes the format to use when sending BinHex4.0 files
   via MIME [BORE93].  The format is compatible with existing mechanisms
   for distributing Macintosh files.  Only when available software
   and/or user practice dictates, should this method be employed.  It is
   recommended to use application/applefile [FALT94] for maximum
   interoperability.

1.  Introduction

   Files on the Macintosh consists of two parts, called forks:

   DATA FORK:       The actual data included in the file.  The Data
                    fork is typically the only meaningful part of a
                    Macintosh file on a non-Macintosh computer system.
                    For example, if a Macintosh user wants to send a
                    file of data to a user on an IBM-PC, she would only
                    send the Data fork.

   RESOURCE FORK:   Contains a collection of arbitrary attribute/value
                    pairs, including program segments, icon bitmaps,
                    and parametric values.

   Additional information regarding Macintosh files is stored by the
   Finder has in a hidden file, called the "Desktop Database".

   Because of the complications in storing different parts of a
   Macintosh file in a non-Macintosh filesystem that only handles
   consecutive data in one part, it is common to convert the Macintosh
   file into some other format before transferring it over the network.

Faltstrom, Crocker & Fair                                       [Page 1]
RFC 1741             Content Type for BinHex Files         December 1994

   AppleDouble file format [APPL90], encoded in MIME as
   multipart/appledouble [FALT94] and application/applefile [FALT94] is
   the preferred format for a Macintosh file that is to be included in
   an Internet mail message, because it provides recipients with
   Macintosh computers the entire document, including Icons and other
   Macintosh specific information, while other users easily can extract
   the Data fork (the actual data).

   However, this specification provides for use of the currently popular
   BinHex4.0 encoding schemes, as a convinience to the installed base of
   users.

2.  MIME format for BinHex4.0

   MIME-base Apple information is specified by:

   MIME type-name:            APPLICATION
   MIME subtype name:         MAC-BINHEX40
   Required parameters:       none
   Optional parameters:       NAME, which must be a "value" as
                              defined in RFC-1521 [BORE93].
   Encoding considerations:   none
   Security considerations:   See separate section in the document
   Published specification:   Appendix A
   Rationale:                 Permits MIME-based transmission of data
                              with Apple Macintosh file system specific
                              information using a currently popular,
                              though platform specific, format.

   2a.  Detail specific to MIME-based usage

      Macintosh documents do not always need to be sent in a special
      format.  Those documents with well-known MIME types and non-
      existent or trivial resource forks can be sent as regular MIME
      body parts, without use of AppleSingle, AppleDouble or BinHex4.0.

      Documents which lack a data fork must be sent as AppleSingle
      according to RFC 1740 [FALT94].

      Unless there are strong reasons not to, all other documents should
      be sent as AppleDouble according to RFC 1740 [FALT94].  This
      includes documents with non-trivial resource forks, and documents
      without corresponding well-known MIME types.

      It may be valuable in some cases to allow the user to choose one
      format over another, either because he disagrees with the
      implementor's definition of "trivial" resource forks, or for
      reasons of his own.

Faltstrom, Crocker & Fair                                       [Page 2]
RFC 1741             Content Type for BinHex Files         December 1994

      Only when available software and/or user practice dictates, should
      BinHex 4.0 be employed.

3.  BinHex

   BinHex 4.0 is a propular means of encoding Macintosh files for
   archiving on non-Macintosh file systems and for transmission via