This is ../info/emacs-mime, produced by makeinfo version 4.0 from
emacs-mime.texi.
INFO-DIR-SECTION Emacs
START-INFO-DIR-ENTRY
* Emacs MIME: (emacs-mime). The MIME de/composition library.
END-INFO-DIR-ENTRY
This file documents the Emacs MIME interface functionality.
Copyright (C) 1998,99,2000 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover texts being "A GNU Manual,"
and with the Back-Cover Texts as in (a) below. A copy of the license
is included in the section entitled "GNU Free Documentation License" in
the Emacs manual.
(a) The FSF's Back-Cover Text is: "You have freedom to copy and
modify this GNU Manual, like GNU software. Copies published by the Free
Software Foundation raise funds for GNU development."
This document is part of a collection distributed under the GNU Free
Documentation License. If you want to distribute this document
separately from the collection, you can do so by adding a copy of the
license to the document, as described in section 6 of the license.
File: emacs-mime, Node: Top, Next: Interface Functions, Up: (dir)
Emacs MIME
**********
This manual documents the libraries used to compose and display MIME
messages.
This is not a manual meant for users; it's a manual directed at
people who want to write functions and commands that manipulate MIME
elements.
MIME is short for "Multipurpose Internet Mail Extensions". This
standard is documented in a number of RFCs; mainly RFC2045 (Format of
Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
Header Extensions for Non-ASCII Text), RFC2048 (Registration
Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
recommended that anyone who intends writing MIME-compliant software
read at least RFC2045 and RFC2047.
* Menu:
* Interface Functions:: An abstraction over the basic functions.
* Basic Functions:: Utility and basic parsing functions.
* Decoding and Viewing:: A framework for decoding and viewing.
* Composing:: MML; a language for describing MIME parts.
* Standards:: A summary of RFCs and working documents used.
* Index:: Function and variable index.
File: emacs-mime, Node: Interface Functions, Next: Basic Functions, Prev: Top, Up: Top
Interface Functions
*******************
The `mail-parse' library is an abstraction over the actual low-level
libraries that are described in the next chapter.
Standards change, and so programs have to change to fit in the new
mold. For instance, RFC2045 describes a syntax for the `Content-Type'
header that only allows ASCII characters in the parameter list.
RFC2231 expands on RFC2045 syntax to provide a scheme for continuation
headers and non-ASCII characters.
The traditional way to deal with this is just to update the library
functions to parse the new syntax. However, this is sometimes the wrong
thing to do. In some instances it may be vital to be able to understand
both the old syntax as well as the new syntax, and if there is only one
library, one must choose between the old version of the library and the
new version of the library.
The Emacs MIME library takes a different tack. It defines a series
of low-level libraries (`rfc2047.el', `rfc2231.el' and so on) that
parses strictly according to the corresponding standard. However,
normal programs would not use the functions provided by these libraries
directly, but instead use the functions provided by the `mail-parse'
library. The functions in this library are just aliases to the
corresponding functions in the latest low-level libraries. Using this
scheme, programs get a consistent interface they can use, and library
developers are free to create write code that handles new standards.
The following functions are defined by this library:
- Function: mail-header-parse-content-type string
Parse STRING, a `Content-Type' header, and return a content-type
list in the following format:
("type/subtype"
(attribute1 . value1)
(attribute2 . value2)
...)
Here's an example:
(mail-header-parse-content-type
"image/gif; name=\"b980912.gif\"")
=> ("image/gif" (name . "b980912.gif"))
- Function: mail-header-parse-content-disposition string
Parse STRING, a `Content-Disposition' header, and return a
content-type list in the format above.
- Function: mail-content-type-get ct attribute
Returns the value of the given ATTRIBUTE from the content-type
list CT.
(mail-content-type-get
'("image/gif" (name . "b980912.gif")) 'name)
=> "b980912.gif"
- Function: mail-header-encode-parameter param value
Takes a parameter string `PARAM=VALUE' and returns an encoded
version of it. This is used for parameters in headers like
`Content-Type' and `Content-Disposition'.
- Function: mail-header-remove-comments string
Return a comment-free version of STRING.
(mail-header-remove-comments
"Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
=> "Gnus/5.070027 "
- Function: mail-header-remove-whitespace string
Remove linear white space from STRING. Space inside quoted
strings and comments is preserved.
(mail-header-remove-whitespace
"image/gif; name=\"Name with spaces\"")
=> "image/gif;name=\"Name with spaces\""
- Function: mail-header-get-comment string
Return the last comment in STRING.
(mail-header-get-comment
"Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
=> "Finnish Landrace"
- Function: mail-header-parse-address string
Parse an address string STRING and return a list containing the
mailbox and the plaintext name.
(mail-header-parse-address
"Hrvoje Niksic <hniksic@srce.hr>")
=> ("hniksic@srce.hr" . "Hrvoje Niksic")
- Function: mail-header-parse-addresses string
Parse STRING as a list of addresses and return a list of elements
like the one described above.
(mail-header-parse-addresses
"Hrvoje Niksic <hniksic@srce.hr>, Steinar Bang <sb@metis.no>")
=> (("hniksic@srce.hr" . "Hrvoje Niksic")
("sb@metis.no" . "Steinar Bang"))
- Function: mail-header-parse-date string
Parse a date STRING and return an Emacs time structure.
- Function: mail-narrow-to-head
Narrow the buffer to the header section of the buffer. Point is
placed at the beginning of the narrowed buffer.
- Function: mail-header-narrow-to-field
Narrow the buffer to the header under point.
- Function: mail-encode-encoded-word-region start end
Encode the non-ASCII words in the region STARTto END. For
instance, `Naïve' is encoded as `=?iso-8859-1?q?Na=EFve?='.
- Function: mail-encode-encoded-word-buffer
Encode the non-ASCII words in the current buffer. This function is
meant to be called with the buffer narrowed to the headers of a
message.
- Function: mail-encode-encoded-word-string string
Encode the words that need encoding in STRING, and return the
result.
(mail-encode-encoded-word-string
"This is naïve, baby")
=> "This is =?iso-8859-1?q?na=EFve,?= baby"
- Function: mail-decode-encoded-word-region start end
Decode the encoded words in the region STARTto END.
- Function: mail-decode-encoded-word-string string
Decode the encoded words in STRING and return the result.
(mail-decode-encoded-word-string
"This is =?iso-8859-1?q?na=EFve,?= baby")
=> "This is naïve, baby"
Currently, `mail-parse' is an abstraction over `ietf-drums',
`rfc2047', `rfc2045' and `rfc2231'. These are documented in the
subsequent sections.
File: emacs-mime, Node: Basic Functions, Next: Decoding and Viewing, Prev: Interface Functions, Up: Top
Basic Functions
***************
This chapter describes the basic, ground-level functions for parsing
and handling. Covered here is parsing `From' lines, removing comments
from header lines, decoding encoded words, parsing date headers and so
on. High-level functionality is dealt with in the next chapter (*note
Decoding and Viewing::).
* Menu:
* rfc2045:: Encoding `Content-Type' headers.
* rfc2231:: Parsing `Content-Type' headers.
* ietf-drums:: Handling mail headers defined by RFC822bis.
* rfc2047:: En/decoding encoded words in headers.
* time-date:: Functions for parsing dates and manipulating time.
* qp:: Quoted-Printable en/decoding.
* base64:: Base64 en/decoding.
* binhex:: Binhex decoding.
* uudecode:: Uuencode decoding.
* rfc1843:: Decoding HZ-encoded text.
* mailcap:: How parts are displayed is specified by mailcap files
File: emacs-mime, Node: rfc2045, Next: rfc2231, Up: Basic Functions
rfc2045
=======
RFC2045 is the "main" MIME document, and as such, one would imagine
that there would be a lot to implement. But there isn't, since most of
the implementation details are delegated to the subsequent RFCs.
So `rfc2045.el' has only a single function:
- Function: rfc2045-encode-string parameter value
Takes a PARAMETER and a VALUE and returns a `PARAM=VALUE' string.
VALUE will be quoted if there are non-safe characters in it.
File: emacs-mime, Node: rfc2231, Next: ietf-drums, Prev: rfc2045, Up: Basic Functions
rfc2231
=======
RFC2231 defines a syntax for the `Content-Type' and
`Content-Disposition' headers. Its snappy name is "MIME Parameter
Value and Encoded Word Extensions: Character Sets, Languages, and
Continuations".
In short, these headers look something like this:
Content-Type: application/x-stuff;
title*0*=us-ascii'en'This%20is%20even%20more%20;
title*1*=%2A%2A%2Afun%2A%2A%2A%20;
title*2="isn't it!"
They usually aren't this bad, though.
The following functions are defined by this library:
- Function: rfc2231-parse-string string
Parse a `Content-Type' header STRING and return a list describing
its elements.
(rfc2231-parse-string
"application/x-stuff;
title*0*=us-ascii'en'This%20is%20even%20more%20;
title*1*=%2A%2A%2Afun%2A%2A%2A%20;
title*2=\"isn't it!\"")
=> ("application/x-stuff"
(title . "This is even more ***fun*** isn't it!"))
- Function: rfc2231-get-value ct attribute
Takes a list CT of the format above and returns the value of the
specified ATTRIBUTE.
- Function: rfc2231-encode-string parameter value
Encode the string `PARAMETER=VALUE' for inclusion in headers likes
`Content-Type' and `Content-Disposition'.
File: emacs-mime, Node: ietf-drums, Next: rfc2047, Prev: rfc2231, Up: Basic Functions
ietf-drums
==========
"drums" is an IETF working group that is working on the replacement
for RFC822.
The functions provided by this library include:
- Function: ietf-drums-remove-comments string
Remove the comments from STRING and return the result.
- Function: ietf-drums-remove-whitespace string
Remove linear white space from STRING and return the result.
Spaces inside quoted strings and comments are left untouched.
- Function: ietf-drums-get-comment string
Return the last most comment from STRING.
- Function: ietf-drums-parse-address string
Parse an address STRING and return a list of the mailbox and the
plain text name.
- Function: ietf-drums-parse-addresses string
Parse STRING, containing any number of comma-separated addresses,
and return a list of mailbox/plain text pairs.
- Function: ietf-drums-parse-date string
Parse the date STRING and return an Emacs time structure.
- Function: ietf-drums-narrow-to-header
Narrow the buffer to the header section of the current buffer.
File: emacs-mime, Node: rfc2047, Next: time-date, Prev: ietf-drums, Up: Basic Functions
rfc2047
=======
RFC2047 (Message Header Extensions for Non-ASCII Text) specifies how
non-ASCII text in headers are to be encoded. This is actually rather
complicated, so a number of variables are necessary to tweak what this
library does.
The following variables are tweakable:
- Variable: rfc2047-default-charset
Characters in this charset should not be decoded by this library.
This defaults to `iso-8859-1'.
- Variable: rfc2047-header-encoding-list
This is an alist of header / encoding-type pairs. Its main
purpose is to prevent encoding of certain headers.
The keys can either be header regexps, or `t'.
The values can be either `nil', in which case the header(s) in
question won't be encoded, or `mime', which means that they will be
encoded.
- Variable: rfc2047-charset-encoding-alist
RFC2047 specifies two forms of encoding--`Q' (a
Quoted-Printable-like encoding) and `B' (base64). This alist
specifies which charset should use which encoding.
- Variable: rfc2047-encoding-function-alist
This is an alist of encoding / function pairs. The encodings are
`Q', `B' and `nil'.
- Variable: rfc2047-q-encoding-alist
The `Q' encoding isn't quite the same for all headers. Some
headers allow a narrower range of characters, and that is what this
variable is for. It's an alist of header regexps and allowable
character ranges.
- Variable: rfc2047-encoded-word-regexp
When decoding words, this library looks for matches to this regexp.
Those were the variables, and these are the functions:
- Function: rfc2047-narrow-to-field
Narrow the buffer to the header on the current line.
- Function: rfc2047-encode-message-header
Should be called narrowed to the header of a message. Encodes
according to `rfc2047-header-encoding-alist'.
- Function: rfc2047-encode-region start end
Encodes all encodable words in the region START to END.
- Function: rfc2047-encode-string string
Encode STRING and return the result.
- Function: rfc2047-decode-region start end
Decode the encoded words in the region START to END.
- Function: rfc2047-decode-string string
Decode STRING and return the result.
File: emacs-mime, Node: time-date, Next: qp, Prev: rfc2047, Up: Basic Functions
time-date
=========
While not really a part of the MIME library, it is convenient to
document this library here. It deals with parsing `Date' headers and
manipulating time. (Not by using tesseracts, though, I'm sorry to say.)
These functions convert between five formats: a date string, an Emacs
time structure, a decoded time list, a number of seconds, and a day
number.
The functions have quite self-explanatory names, so the following
just gives an overview of which functions are available.
(parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
=> (54 21 12 12 9 1998 6 nil 7200)
(date-to-time "Sat Sep 12 12:21:54 1998 +0200")
=> (13818 19266)
(time-to-seconds '(13818 19266))
=> 905595714.0
(seconds-to-time 905595714.0)
=> (13818 19266 0)
(time-to-day '(13818 19266))
=> 729644
(days-to-time 729644)
=> (961933 65536)
(time-since '(13818 19266))
=> (0 430)
(time-less-p '(13818 19266) '(13818 19145))
=> nil
(subtract-time '(13818 19266) '(13818 19145))
=> (0 121)
(days-between "Sat Sep 12 12:21:54 1998 +0200"
"Sat Sep 07 12:21:54 1998 +0200")
=> 5
(date-leap-year-p 2000)
=> t
(time-to-day-in-year '(13818 19266))
=> 255
And finally, we have `safe-date-to-time', which does the same as
`date-to-time', but returns a zero time if the date is syntactically
malformed.
File: emacs-mime, Node: qp, Next: base64, Prev: time-date, Up: Basic Functions
qp
==
This library deals with decoding and encoding Quoted-Printable text.
Very briefly explained, QP encoding means translating all 8-bit
characters (and lots of control characters) into things that look like
`=EF'; that is, an equal sign followed by the byte encoded as a hex
string. It is defined in RFC 2045.
The following functions are defined by the library:
- Command: quoted-printable-decode-region FROM TO &optional
CODING-SYSTEM
QP-decode all the encoded text in the region. If CODING-SYSTEM is
non-nil, decode bytes into characters with that coding-system. It
is probably better not to use CODING-SYSTEM; instead decode into a
unibyte buffer, decode that appropriately and then interpret it as
multibyte.
- Function: quoted-printable-decode-string STRING &optional
CODING-SYSTEM
Return a QP-encoded copy of STRING. If CODING-SYSTEM is non-nil,
decode bytes into characters with that coding-system.
- Command: quoted-printable-encode-region FROM TO &optional FOLD CLASS
QP-encode all the region. If FOLD is non-NIL, fold lines at 76
characters, as required by the RFC. If CLASS is non-`nil',
translate the characters not matched by that regexp class, which
should be in the form expected by SKIP-CHARS-FORWARD and should
probably not contain literal eight-bit characters. Specifying
CLASS makes sense to do extra encoding in header fields.
If variable MM-USE-ULTRA-SAFE-ENCODING is defined and non-`nil',
fold lines unconditionally and encode `From ' and `-' at the start
of lines..
- Function: quoted-printable-encode-string string
Return a QP-encoded copy of STRING.
File: emacs-mime, Node: base64, Next: binhex, Prev: qp, Up: Basic Functions
base64
======
Base64 is an encoding that encodes three bytes into four characters,
thereby increasing the size by about 33%. The alphabet used for
encoding is very resistant to mangling during transit. *Note Base 64
Encoding: (elisp)Base 64.
File: emacs-mime, Node: binhex, Next: uudecode, Prev: base64, Up: Basic Functions
binhex
======
Binhex is an encoding that originated in Macintosh environments.
The following function is supplied to deal with these:
- Function: binhex-decode-region start end &optional header-only
Decode the encoded text in the region START to END. If
HEADER-ONLY is non-`nil', only decode the `binhex' header and
return the file name.
File: emacs-mime, Node: uudecode, Next: rfc1843, Prev: binhex, Up: Basic Functions
uudecode
========
Uuencoding is probably still the most popular encoding of binaries
used on Usenet, although Base64 rules the mail world.
The following function is supplied by this package:
- Function: uudecode-decode-region start end &optional file-name
Decode the text in the region START to END. If FILE-NAME is
non-`nil', save the result to FILE-NAME.
File: emacs-mime, Node: rfc1843, Next: mailcap, Prev: uudecode, Up: Basic Functions
rfc1843
=======
RFC1843 deals with mixing Chinese and ASCII characters in messages.
In essence, RFC1843 switches between ASCII and Chinese by doing this:
This sentence is in ASCII.
The next sentence is in GB.~{<:Ky2;S{#,NpJ)l6HK!#~}Bye.
Simple enough, and widely used in China.
The following functions are available to handle this encoding:
- Function: rfc1843-decode-region start end
Decode HZ-encoded text in the region START to END.
- Function: rfc1843-decode-string string
Decode the HZ-encoded STRING and return the result.
File: emacs-mime, Node: mailcap, Prev: rfc1843, Up: Basic Functions
mailcap
=======
As specified by RFC 1524, MIME-aware message handlers parse
"mailcap" files from a default list, which can be overridden by the
`MAILCAP' environment variable. These describe how elements are
supposed to be displayed. Here's an example file:
image/*; gimp -8 %s
audio/wav; wavplayer %s
This says that all image files should be displayed with `gimp', and
that WAVE audio files should be played by `wavplayer'.
The `mailcap' library parses such files, and provides functions for
matching types.
- Variable: mailcap-mime-data
This variable is an alist of alists containing backup viewing
rules for MIME types. These are overridden by rules for a type
found in mailcap files. The outer alist is keyed on the major
content-type and the inner alists are keyed on the minor
content-type (which can be a regular expression).
For example:
(("application"
("octet-stream"
(viewer . mailcap-save-binary-file)
(non-viewer . t)
(type . "application/octet-stream"))
("plain"
(viewer . view-mode)
(test fboundp 'view-mode)
(type . "text/plain")))
- User Option: mailcap-default-mime-data
This variable is the default value of `mailcap-mime-data'. It
exists to allow setting the value using Custom. It is merged with
values from mailcap files by `mailcap-parse-mailcaps'.
Although it is not specified by the RFC, MIME tools normally use a
common means of associating file extensions with defualt MIME types in
the absence of other information about the type of a file. The
information is found in per-user files `~/.mime.types' and system
`mime.types' files found in quasi-standard places. Here is an example:
application/x-dvi dvi
audio/mpeg mpga mpega mp2 mp3
image/jpeg jpeg jpg jpe
- Variable: mailcap-mime-extensions
This variable is an alist MIME types keyed by file extensions.
This is overridden by entries found in `mime.types' files.
- User Option: mailcap-default-mime-extensions
This variable is the default value of `mailcap-mime-extensions'.
It exists to allow setting the value using Custom. It is merged
with values from mailcap files by `mailcap-parse-mimetypes'.
Interface functions:
- Function: mailcap-parse-mailcaps &optional path force
Parse all the mailcap files specified in a path string PATH and
merge them with the values from `mailcap-mime-data'. Components of
PATH are separated by the `path-separator' character appropriate
for the system. If FORCE is non-`nil', the files are re-parsed
even if they have been parsed already. If PATH is omitted, use
the value of environment variable `MAILCAPS' if it is set;
otherwise (on GNU and Unix) use the path defined in RFC 1524, plus
`/usr/local/etc/mailcap'.
- Function: mailcap-parse-mimetypes &optional path force
Parse all the mimetypes specified in a path string PATH and merge
them with the values from `mailcap-mime-extensions'. Components
of PATH are separated by the `path-separator' character
appropriate for the system. If PATH is omitted, use the value of
environment variable `MIMETYPES' if set; otherwise use a default
path consistent with that used by `mailcap-parse-mailcaps'. If
FORCE is non-`nil', the files are re-parsed even if they have been
parsed already.
- Function: mailcap-mime-info string &optional request
Gets the viewer command for content-type STRING. `nil' is
returned if none is found. Expects STRING to be a complete
content-type header line.
If REQUEST is non-`nil' it specifies what information to return.
If it is nil or the empty string, the viewer (second field of the
mailcap entry) will be returned. If it is a string, then the
mailcap field corresponding to that string will be returned
(`print', `description', whatever). If it is a number, all the
information for this viewer is returned. If it is `all', then all
possible viewers for this type is returned.
- Function: mailcap-mime-types
This function returns a list of all the defined media types.
- Function: mailcap-extension-to-mime extension
This function returns the content type defined for a file with the
given EXTENSION.
File: emacs-mime, Node: Decoding and Viewing, Next: Composing, Prev: Basic Functions, Up: Top
Decoding and Viewing
********************
This chapter deals with decoding and viewing MIME messages on a
higher level.
The main idea is to first analyze a MIME article, and then allow
other programs to do things based on the list of "handles" that are
returned as a result of this analysis.
* Menu:
* Dissection:: Analyzing a MIME message.
* Handles:: Handle manipulations.
* Display:: Displaying handles.
* Customization:: Variables that affect display.
* New Viewers:: How to write your own viewers.
File: emacs-mime, Node: Dissection, Next: Handles, Up: Decoding and Viewing
Dissection
==========
The `mm-dissect-buffer' is the function responsible for dissecting a
MIME article. If given a multipart message, it will recursively
descend the message, following the structure, and return a tree of MIME
handles that describes the structure of the message.
File: emacs-mime, Node: Handles, Next: Display, Prev: Dissection, Up: Decoding and Viewing
Handles
=======
A MIME handle is a list that fully describes a MIME component.
The following macros can be used to access elements from the HANDLE
argument:
- Macro: mm-handle-buffer handle
Return the buffer that holds the contents of the undecoded MIME
part.
- Macro: mm-handle-type handle
Return the parsed `Content-Type' of the part.
- Macro: mm-handle-encoding handle
Return the `Content-Transfer-Encoding' of the part.
- Macro: mm-handle-undisplayer handle
Return the function that can be used to remove the displayed part
(if it has been displayed).
- Macro: mm-handle-set-undisplayer handle function
Set the undisplayer function for the part to function.
- Macro: mm-handle-disposition
Return the parsed `Content-Disposition' of the part.
- Macro: mm-handle-disposition
Return the description of the part.
- Macro: mm-get-content-id id
Returns the handle(s) referred to by ID, the `Content-ID' of the
part.
File: emacs-mime, Node: Display, Next: Customization, Prev: Handles, Up: Decoding and Viewing
Display
=======
Functions for displaying, removing and saving. In the descriptions
below, `the part' means the MIME part represented by the HANDLE
argument.
- Function: mm-display-part handle &optional no-default
Display the part. Return `nil' if the part is removed, `inline'
if it is displayed inline or `external' if it is displayed
externally. If NO-DEFAULT is non-`nil', the part is not displayed
unless the MIME type of HANDLE is defined to be displayed inline
or there is an display method defined for it; i.e. no default
external method will be used.
- Function: mm-remove-part handle
Remove the part if it has been displayed.
- Function: mm-inlinable-p handle
Return non-`nil' if the part can be displayed inline.
- Function: mm-automatic-display-p handle
Return non-`nil' if the user has requested automatic display of the
MIME type of the part.
- Function: mm-destroy-part handle
Free all the resources used by the part.
- Function: mm-save-part handle
Save the part to a file. The user is prompted for a file name to
use.
- Function: mm-pipe-part handle
Pipe the part through a shell command. The user is prompted for
the command to use.
- Function: mm-interactively-view-part handle
Prompt for a mailcap method to use to view the part and display it
externally using that method.
File: emacs-mime, Node: Customization, Next: New Viewers, Prev: Display, Up: Decoding and Viewing
Customization
=============
The display of MIME types may be customized with the following
options.
- User Option: mm-inline-media-tests
This is an alist where the key is a MIME type, the second element
is a function to display the part "inline" (i.e., inside Emacs),
and the third element is a form to be `eval'ed to say whether the
part can be displayed inline.
This variable specifies whether a part _can_ be displayed inline,
and, if so, how to do it. It does not say whether parts are
_actually_ displayed inline.
- User Option: mm-inlined-types
This, on the other hand, says what types are to be displayed
inline, if they satisfy the conditions set by the variable above.
It's a list of MIME media types.
- User Option: mm-automatic-display
This is a list of types that are to be displayed "automatically",
but only if the above variable allows it. That is, only inlinable
parts can be displayed automatically.
- User Option: mm-attachment-override-types
Some MIME agents create parts that have a content-disposition of
`attachment'. This variable allows overriding that disposition and
displaying the part inline. (Note that the disposition is only
overridden if we are able to, and want to, display the part
inline.)
- User Option: mm-discouraged-alternatives
List of MIME types that are discouraged when viewing
`multipart/alternative'. Viewing agents are supposed to view the
last possible part of a message, as that is supposed to be the
richest. However, users may prefer other types instead, and this
list says what types are most unwanted. If, for instance,
`text/html' parts are very unwanted, and `text/richtech' parts are
somewhat unwanted, then the value of this variable should be set
to:
("text/html" "text/richtext")
- User Option: mm-inline-large-images-p
When displaying inline images that are larger than the window,
XEmacs does not enable scrolling, which means that you cannot see
the whole image. To prevent this, the library tries to determine
the image size before displaying it inline, and if it doesn't fit
the window, the library will display it externally (e.g. with
`ImageMagick' or `xv'). Setting this variable to `t' disables
this check and makes the library display all inline images as
inline, regardless of their size.
- User Option: mm-inline-override-p
`mm-inlined-types' may include regular expressions, for example to
specify that all `text/.*' parts be displayed inline. If a user
prefers to have a type that matches such a regular expression be
treated as an attachment, that can be accomplished by setting this
variable to a list containing that type. For example assuming
`mm-inlined-types' includes `text/.*', then including `text/html'
in this variable will cause `text/html' parts to be treated as
attachments.
File: emacs-mime, Node: New Viewers, Prev: Customization, Up: Decoding and Viewing
New Viewers
===========
Here's an example viewer for displaying `text/enriched' inline:
(defun mm-display-enriched-inline (handle)
(let (text)
(with-temp-buffer
(mm-insert-part handle)
(save-window-excursion
(enriched-decode (point-min) (point-max))
(setq text (buffer-string))))
(mm-insert-inline handle text)))
We see that the function takes a MIME handle as its parameter. It
then goes to a temporary buffer, inserts the text of the part, does some
work on the text, stores the result, goes back to the buffer it was
called from and inserts the result.
The two important helper functions here are `mm-insert-part' and
`mm-insert-inline'. The first function inserts the text of the handle
in the current buffer. It handles charset and/or content transfer
decoding. The second function just inserts whatever text you tell it
to insert, but it also sets things up so that the text can be
"undisplayed' in a convenient manner.
File: emacs-mime, Node: Composing, Next: Standards, Prev: Decoding and Viewing, Up: Top
Composing
*********
Creating a MIME message is boring and non-trivial. Therefore, a
library called `mml' has been defined that parses a language called MML
(MIME Meta Language) and generates MIME messages.
The main interface function is `mml-generate-mime'. It will examine
the contents of the current (narrowed-to) buffer and return a string
containing the MIME message.
* Menu:
* Simple MML Example:: An example MML document.
* MML Definition:: All valid MML elements.
* Advanced MML Example:: Another example MML document.
* Charset Translation:: How charsets are mapped from Mule to MIME.
* Conversion:: Going from MIME to MML and vice versa.
File: emacs-mime, Node: Simple MML Example, Next: MML Definition, Up: Composing
Simple MML Example
==================
Here's a simple `multipart/alternative':
<#multipart type=alternative>
This is a plain text part.
<#part type=text/enriched>
<center>This is a centered enriched part</center>
<#/multipart>
After running this through `mml-generate-mime', we get this:
Content-Type: multipart/alternative; boundary="=-=-="
--=-=-=
This is a plain text part.
--=-=-=
Content-Type: text/enriched
<center>This is a centered enriched part</center>
--=-=-=--
File: emacs-mime, Node: MML Definition, Next: Advanced MML Example, Prev: Simple MML Example, Up: Composing
MML Definition
==============
The MML language is very simple. It looks a bit like an SGML
application, but it's not.
The main concept of MML is the "part". Each part can be of a
different type or use a different charset. The way to delineate a part
is with a `<#part ...>' tag. Multipart parts can be introduced with
the `<#multipart ...>' tag. Parts are ended by the `<#/part>' or
`<#/multipart>' tags. Parts started with the `<#part ...>' tags are
also closed by the next open tag.
There's also the `<#external ...>' tag. These introduce
`external/message-body' parts.
Each tag can contain zero or more parameters on the form
`parameter=value'. The values may be enclosed in quotation marks, but
that's not necessary unless the value contains white space. So
`filename=/home/user/#hello$^yes' is perfectly valid.
The following parameters have meaning in MML; parameters that have no
meaning are ignored. The MML parameter names are the same as the MIME
parameter names; the things in the parentheses say which header it will
be used in.
`type'
The MIME type of the part (`Content-Type').
`filename'
Use the contents of the file in the body of the part
(`Content-Disposition').
`charset'
The contents of the body of the part are to be encoded in the
character set speficied (`Content-Type').
`name'
Might be used to suggest a file name if the part is to be saved to
a file (`Content-Type').
`disposition'
Valid values are `inline' and `attachment' (`Content-Disposition').
`encoding'
Valid values are `7bit', `8bit', `quoted-printable' and `base64'
(`Content-Transfer-Encoding').
`description'
A description of the part (`Content-Description').
`creation-date'
RFC822 date when the part was created (`Content-Disposition').
`modification-date'
RFC822 date when the part was modified (`Content-Disposition').
`read-date'
RFC822 date when the part was read (`Content-Disposition').
`size'
The size (in octets) of the part (`Content-Disposition').
Parameters for `application/octet-stream':
`type'
Type of the part; informal--meant for human readers
(`Content-Type').
Parameters for `message/external-body':
`access-type'
A word indicating the supported access mechanism by which the file
may be obtained. Values include `ftp', `anon-ftp', `tftp',
`localfile', and `mailserver'. (`Content-Type'.)
`expiration'
The RFC822 date after which the file may no longer be fetched.
(`Content-Type'.)
`size'
The size (in octets) of the file. (`Content-Type'.)
`permission'
Valid values are `read' and `read-write' (`Content-Type').
File: emacs-mime, Node: Advanced MML Example, Next: Charset Translation, Prev: MML Definition, Up: Composing
Advanced MML Example
====================
Here's a complex multipart message. It's a `multipart/mixed' that
contains many parts, one of which is a `multipart/alternative'.
<#multipart type=mixed>
<#part type=image/jpeg filename=~/rms.jpg disposition=inline>
<#multipart type=alternative>
This is a plain text part.
<#part type=text/enriched name=enriched.txt>
<center>This is a centered enriched part</center>
<#/multipart>
This is a new plain text part.
<#part disposition=attachment>
This plain text part is an attachment.
<#/multipart>
And this is the resulting MIME message:
Content-Type: multipart/mixed; boundary="=-=-="
--=-=-=
--=-=-=
Content-Type: image/jpeg;
filename="~/rms.jpg"
Content-Disposition: inline;
filename="~/rms.jpg"
Content-Transfer-Encoding: base64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--=-=-=
Content-Type: multipart/alternative; boundary="==-=-="
--==-=-=
This is a plain text part.
--==-=-=
Content-Type: text/enriched;
name="enriched.txt"
<center>This is a centered enriched part</center>
--==-=-=--
--=-=-=
This is a new plain text part.
--=-=-=
Content-Disposition: attachment
This plain text part is an attachment.
--=-=-=--
File: emacs-mime, Node: Charset Translation, Next: Conversion, Prev: Advanced MML Example, Up: Composing
Charset Translation
===================
During translation from MML to MIME, for each MIME part which has
been composed inside Emacs, an appropriate MIME charset has to be
chosen.
If you are running a non-Mule Emacs, this process is simple: if the
part contains any non-ASCII (8-bit) characters, the MIME charset given
by `mail-parse-charset' (a symbol) is used. (Never set this variable
directly, though. If you want to change the default charset, please
consult the documentation of the package which you use to process MIME
messages. *Note Various Message Variables: (message)Various Message
Variables, for example.) If there are only ASCII characters, the MIME
charset `US-ASCII' is used, of course.
Things are slightly more complicated when running Emacs with Mule
support. In this case, a list of the Mule charsets used in the part is
obtained, and the corresponding MIME charsets are determined. If this
results in a single MIME charset, this is used to encode the part. But
if the resulting list of MIME charsets contains more than one element,
two things can happen: if it is possible to encode the part via UTF-8,
this charset is used. (For this, Emacs must support the `utf-8' coding
system, and the part must consist entirely of characters which have
Unicode counterparts.) If UTF-8 is not available, the part is split
into several, so that each one can be encoded with a single MIME
charset. The part can only be split at line boundaries, though--if
more than one MIME charset is required to encode a single line, it is
not possible to encode the part.
File: emacs-mime, Node: Conversion, Prev: Charset Translation, Up: Composing
Conversion
==========
A (multipart) MIME message can be converted to MML with the
`mime-to-mml' function. It works on the message in the current buffer,
and substitutes MML markup for MIME boundaries. Non-textual parts do
not have their contents in the buffer, but instead have the contents in
separate buffers that are referred to from the MML tags.
An MML message can be converted back to MIME by the `mml-to-mime'
function.
These functions are in certain senses "lossy"--you will not get back
an identical message if you run MIME-TO-MML and then MML-TO-MIME. Not
only will trivial things like the order of the headers differ, but the
contents of the headers may also be different. For instance, the
original message may use base64 encoding on text, while MML-TO-MIME may
decide to use quoted-printable encoding, and so on.
In essence, however, these two functions should be the inverse of
each other. The resulting contents of the message should remain
equivalent, if not identical.
File: emacs-mime, Node: Standards, Next: Index, Prev: Composing, Up: Top
Standards
*********
The Emacs MIME library implements handling of various elements
according to a (somewhat) large number of RFCs, drafts and standards
documents. This chapter lists the relevant ones. They can all be
fetched from `http://quimby.gnus.org/notes/'.
"RFC822"
"STD11"
Standard for the Format of ARPA Internet Text Messages.
"RFC1036"
Standard for Interchange of USENET Messages
"RFC1524"
A User Agent Configuration Mechanism For Multimedia Mail Format
Information
"RFC2045"
Format of Internet Message Bodies
"RFC2046"
Media Types
"RFC2047"
Message Header Extensions for Non-ASCII Text
"RFC2048"
Registration Procedures
"RFC2049"
Conformance Criteria and Examples
"RFC2231"
MIME Parameter Value and Encoded Word Extensions: Character Sets,
Languages, and Continuations
"RFC1843"
HZ - A Data Format for Exchanging Files of Arbitrarily Mixed
Chinese and ASCII characters
"draft-ietf-drums-msg-fmt-05.txt"
Draft for the successor of RFC822
"RFC2112"
The MIME Multipart/Related Content-type
"RFC1892"
The Multipart/Report Content Type for the Reporting of Mail System
Administrative Messages
"RFC2183"
Communicating Presentation Information in Internet Messages: The
Content-Disposition Header Field
File: emacs-mime, Node: Index, Prev: Standards, Up: Top
Index
*****
* Menu:
* Apple: binhex.
* base64: base64.
* binhex: binhex.
* binhex-decode-region: binhex.
* charsets: Charset Translation.
* Chinese: rfc1843.
* Composing: Composing.
* date-leap-year-p: time-date.
* date-to-time: time-date.
* days-between: time-date.
* days-to-time: time-date.
* HZ: rfc1843.
* ietf-drums-get-comment: ietf-drums.
* ietf-drums-narrow-to-header: ietf-drums.
* ietf-drums-parse-address: ietf-drums.
* ietf-drums-parse-addresses: ietf-drums.
* ietf-drums-parse-date: ietf-drums.
* ietf-drums-remove-comments: ietf-drums.
* ietf-drums-remove-whitespace: ietf-drums.
* interface functions: Interface Functions.
* Macintosh: binhex.
* mail-content-type-get: Interface Functions.
* mail-decode-encoded-word-region: Interface Functions.
* mail-decode-encoded-word-string: Interface Functions.
* mail-encode-encoded-word-buffer: Interface Functions.
* mail-encode-encoded-word-region: Interface Functions.
* mail-encode-encoded-word-string: Interface Functions.
* mail-header-encode-parameter: Interface Functions.
* mail-header-get-comment: Interface Functions.
* mail-header-narrow-to-field: Interface Functions.
* mail-header-parse-address: Interface Functions.
* mail-header-parse-addresses: Interface Functions.
* mail-header-parse-content-disposition: Interface Functions.
* mail-header-parse-content-type: Interface Functions.
* mail-header-parse-date: Interface Functions.
* mail-header-remove-comments: Interface Functions.
* mail-header-remove-whitespace: Interface Functions.
* mail-narrow-to-head: Interface Functions.
* mail-parse: Interface Functions.
* mail-parse-charset: Charset Translation.
* mailcap-default-mime-data: mailcap.
* mailcap-default-mime-extensions: mailcap.
* mailcap-extension-to-mime: mailcap.
* mailcap-mime-data: mailcap.
* mailcap-mime-extensions: mailcap.
* mailcap-mime-info: mailcap.
* mailcap-mime-types: mailcap.
* mailcap-parse-mailcaps: mailcap.
* mailcap-parse-mimetypes: mailcap.
* MIME Composing: Composing.
* MIME Meta Language: Composing.
* mime-to-mml: Conversion.
* mm-attachment-override-types: Customization.
* mm-automatic-display: Customization.
* mm-automatic-display-p: Display.
* mm-destroy-part: Display.
* mm-discouraged-alternatives: Customization.
* mm-display-part: Display.
* mm-get-content-id: Handles.
* mm-handle-buffer: Handles.
* mm-handle-disposition: Handles.
* mm-handle-encoding: Handles.
* mm-handle-set-undisplayer: Handles.
* mm-handle-type: Handles.
* mm-handle-undisplayer: Handles.
* mm-inlinable-p: Display.
* mm-inline-large-images-p: Customization.
* mm-inline-media-tests: Customization.
* mm-inline-override-p: Customization.
* mm-inlined-types: Customization.
* mm-interactively-view-part: Display.
* mm-mime-mule-charset-alist: Charset Translation.
* mm-pipe-part: Display.
* mm-remove-part: Display.
* mm-save-part: Display.
* MML: Composing.
* mml-generate-mime: Composing.
* mml-to-mime: Conversion.
* Mule: Charset Translation.
* parse-time-string: time-date.
* quoted-printable-decode-region: qp.
* quoted-printable-decode-string: qp.
* quoted-printable-encode-region: qp.
* quoted-printable-encode-string: qp.
* rfc1843: rfc1843.
* rfc1843-decode-region: rfc1843.
* rfc1843-decode-string: rfc1843.
* rfc2045-encode-string: rfc2045.
* rfc2047-charset-encoding-alist: rfc2047.
* rfc2047-decode-region: rfc2047.
* rfc2047-decode-string: rfc2047.
* rfc2047-default-charset: rfc2047.
* rfc2047-encode-message-header: rfc2047.
* rfc2047-encode-region: rfc2047.
* rfc2047-encode-string: rfc2047.
* rfc2047-encoded-word-regexp: rfc2047.
* rfc2047-encoding-function-alist: rfc2047.
* rfc2047-header-encoding-list: rfc2047.
* rfc2047-narrow-to-field: rfc2047.
* rfc2047-q-encoding-alist: rfc2047.
* rfc2231-encode-string: rfc2231.
* rfc2231-get-value: rfc2231.
* rfc2231-parse-string: rfc2231.
* safe-date-to-time: time-date.
* seconds-to-time: time-date.
* subtract-time: time-date.
* time-less-p: time-date.
* time-since: time-date.
* time-to-day: time-date.
* time-to-day-in-year: time-date.
* time-to-seconds: time-date.
* Unicode: Charset Translation.
* UTF-8: Charset Translation.
* uudecode: uudecode.
* uudecode-decode-region: uudecode.
* uuencode: uudecode.
* Menu:
Tag Table:
Node: Top1248
Node: Interface Functions2414
Node: Basic Functions8069
Node: rfc20459085
Node: rfc22319622
Node: ietf-drums11005
Node: rfc204712164
Node: time-date14498
Node: qp16085
Node: base6417884
Node: binhex18216
Node: uudecode18666
Node: rfc184319135
Node: mailcap19793
Node: Decoding and Viewing24282
Node: Dissection24919
Node: Handles25287
Node: Display26379
Node: Customization27885
Node: New Viewers31003
Node: Composing32114
Node: Simple MML Example32938
Node: MML Definition33616
Node: Advanced MML Example36430
Node: Charset Translation39267
Node: Conversion40968
Node: Standards42059
Node: Index43462
End Tag Table