MIME Encapsulation of Macintosh Files - MacMIME (RFC1740)

Network Working Group Patrik Faltstrom Request for Comments: 1740 Royal Institute of Technology Category: Standards Track Dave Crocker Brandenburg Consulting Erik E. Fair Apple Computer Inc. December 1994

MIME Encapsulation of Macintosh files - MacMIME

Status of this Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Abstract

This memo describes the format to use when sending Apple Macintosh files via MIME [BORE93]. The format is compatible with existing mechanisms for distributing Macintosh files, while allowing non- Macintosh systems access to data in standardized formats.

2. 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 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 1740 MIME-based Mac files December 1994

The two styles of use are [APPL90]:

AppleSingle: Apple’s standard format for encoding Macintosh files as one byte stream. AppleDouble: Similar to AppleSingle except that the Data fork is separated from the Macintosh-specific parts by the AppleDouble encoding.

AppleDouble 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) as it is separated from the AppleDouble encoding.

2. MIME format for Apple/Macintosh-specific file information

2a. APPLICATION/APPLEFILE

MIME type-name: APPLICATION MIME subtype name: APPLEFILE Required parameters: none Optional parameters: NAME, which must be a "value" as defined in RFC-1521 [BORE93]. Encoding considerations: The presence of binary data will typically require use of Content-Transfer-Encoding: BASE64 Security considerations: See separate section in the document Published specification: Apple-single & Apple-double [APPL90] Rationale: Permits MIME-based transmission of data w...