3 @setfilename ../info/emacs-mime
4 @settitle Emacs MIME Manual
10 This file documents the Emacs MIME interface functionality.
12 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
13 Free Software Foundation, Inc.
16 Permission is granted to copy, distribute and/or modify this document
17 under the terms of the GNU Free Documentation License, Version 1.2 or
18 any later version published by the Free Software Foundation; with no
19 Invariant Sections, with the Front-Cover texts being ``A GNU
20 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
21 license is included in the section entitled ``GNU Free Documentation
22 License'' in the Emacs manual.
24 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
25 this GNU Manual, like GNU software. Copies published by the Free
26 Software Foundation raise funds for GNU development.''
28 This document is part of a collection distributed under the GNU Free
29 Documentation License. If you want to distribute this document
30 separately from the collection, you can do so by adding a copy of the
31 license to the document, as described in section 6 of the license.
37 * Emacs MIME: (emacs-mime). Emacs MIME de/composition library.
42 @setchapternewpage odd
45 @title Emacs MIME Manual
47 @author by Lars Magne Ingebrigtsen
49 @vskip 0pt plus 1filll
56 This manual documents the libraries used to compose and display
57 @acronym{MIME} messages.
59 This manual is directed at users who want to modify the behavior of
60 the @acronym{MIME} encoding/decoding process or want a more detailed
61 picture of how the Emacs @acronym{MIME} library works, and people who want
62 to write functions and commands that manipulate @acronym{MIME} elements.
64 @acronym{MIME} is short for @dfn{Multipurpose Internet Mail Extensions}.
65 This standard is documented in a number of RFCs; mainly RFC2045 (Format
66 of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
67 Header Extensions for Non-@acronym{ASCII} Text), RFC2048 (Registration
68 Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
69 recommended that anyone who intends writing @acronym{MIME}-compliant software
70 read at least RFC2045 and RFC2047.
73 * Decoding and Viewing:: A framework for decoding and viewing.
74 * Composing:: @acronym{MML}; a language for describing @acronym{MIME} parts.
75 * Interface Functions:: An abstraction over the basic functions.
76 * Basic Functions:: Utility and basic parsing functions.
77 * Standards:: A summary of RFCs and working documents used.
78 * Index:: Function and variable index.
82 @node Decoding and Viewing
83 @chapter Decoding and Viewing
85 This chapter deals with decoding and viewing @acronym{MIME} messages on a
88 The main idea is to first analyze a @acronym{MIME} article, and then allow
89 other programs to do things based on the list of @dfn{handles} that are
90 returned as a result of this analysis.
93 * Dissection:: Analyzing a @acronym{MIME} message.
94 * Non-MIME:: Analyzing a non-@acronym{MIME} message.
95 * Handles:: Handle manipulations.
96 * Display:: Displaying handles.
97 * Display Customization:: Variables that affect display.
98 * Files and Directories:: Saving and naming attachments.
99 * New Viewers:: How to write your own viewers.
106 The @code{mm-dissect-buffer} is the function responsible for dissecting
107 a @acronym{MIME} article. If given a multipart message, it will recursively
108 descend the message, following the structure, and return a tree of
109 @acronym{MIME} handles that describes the structure of the message.
113 @vindex mm-uu-configure-list
115 Gnus also understands some non-@acronym{MIME} attachments, such as
116 postscript, uuencode, binhex, yenc, shar, forward, gnatsweb, pgp,
117 diff. Each of these features can be disabled by add an item into
118 @code{mm-uu-configure-list}. For example,
122 (add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
148 Non-@acronym{MIME} forwarded message.
156 @acronym{PGP} signed clear text.
159 @findex pgp-encrypted
160 @acronym{PGP} encrypted clear text.
164 @acronym{PGP} public keys.
167 @findex emacs-sources
168 @vindex mm-uu-emacs-sources-regexp
169 Emacs source code. This item works only in the groups matching
170 @code{mm-uu-emacs-sources-regexp}.
174 @vindex mm-uu-diff-groups-regexp
175 Patches. This is intended for groups where diffs of committed files
176 are automatically sent to. It only works in groups matching
177 @code{mm-uu-diff-groups-regexp}.
184 A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
187 The following macros can be used to access elements in a handle:
190 @item mm-handle-buffer
191 @findex mm-handle-buffer
192 Return the buffer that holds the contents of the undecoded @acronym{MIME}
196 @findex mm-handle-type
197 Return the parsed @code{Content-Type} of the part.
199 @item mm-handle-encoding
200 @findex mm-handle-encoding
201 Return the @code{Content-Transfer-Encoding} of the part.
203 @item mm-handle-undisplayer
204 @findex mm-handle-undisplayer
205 Return the object that can be used to remove the displayed part (if it
208 @item mm-handle-set-undisplayer
209 @findex mm-handle-set-undisplayer
210 Set the undisplayer object.
212 @item mm-handle-disposition
213 @findex mm-handle-disposition
214 Return the parsed @code{Content-Disposition} of the part.
216 @item mm-get-content-id
217 Returns the handle(s) referred to by @code{Content-ID}.
225 Functions for displaying, removing and saving.
228 @item mm-display-part
229 @findex mm-display-part
233 @findex mm-remove-part
234 Remove the part (if it has been displayed).
237 @findex mm-inlinable-p
238 Say whether a @acronym{MIME} type can be displayed inline.
240 @item mm-automatic-display-p
241 @findex mm-automatic-display-p
242 Say whether a @acronym{MIME} type should be displayed automatically.
244 @item mm-destroy-part
245 @findex mm-destroy-part
246 Free all resources occupied by a part.
250 Offer to save the part in a file.
254 Offer to pipe the part to some process.
256 @item mm-interactively-view-part
257 @findex mm-interactively-view-part
258 Prompt for a mailcap method to use to view the part.
263 @node Display Customization
264 @section Display Customization
268 @item mm-inline-media-tests
269 @vindex mm-inline-media-tests
270 This is an alist where the key is a @acronym{MIME} type, the second element
271 is a function to display the part @dfn{inline} (i.e., inside Emacs), and
272 the third element is a form to be @code{eval}ed to say whether the part
273 can be displayed inline.
275 This variable specifies whether a part @emph{can} be displayed inline,
276 and, if so, how to do it. It does not say whether parts are
277 @emph{actually} displayed inline.
279 @item mm-inlined-types
280 @vindex mm-inlined-types
281 This, on the other hand, says what types are to be displayed inline, if
282 they satisfy the conditions set by the variable above. It's a list of
283 @acronym{MIME} media types.
285 @item mm-automatic-display
286 @vindex mm-automatic-display
287 This is a list of types that are to be displayed ``automatically'', but
288 only if the above variable allows it. That is, only inlinable parts can
289 be displayed automatically.
291 @item mm-automatic-external-display
292 @vindex mm-automatic-external-display
293 This is a list of types that will be displayed automatically in an
296 @item mm-keep-viewer-alive-types
297 @vindex mm-keep-viewer-alive-types
298 This is a list of media types for which the external viewer will not
299 be killed when selecting a different article.
301 @item mm-attachment-override-types
302 @vindex mm-attachment-override-types
303 Some @acronym{MIME} agents create parts that have a content-disposition of
304 @samp{attachment}. This variable allows overriding that disposition and
305 displaying the part inline. (Note that the disposition is only
306 overridden if we are able to, and want to, display the part inline.)
308 @item mm-discouraged-alternatives
309 @vindex mm-discouraged-alternatives
310 List of @acronym{MIME} types that are discouraged when viewing
311 @samp{multipart/alternative}. Viewing agents are supposed to view the
312 last possible part of a message, as that is supposed to be the richest.
313 However, users may prefer other types instead, and this list says what
314 types are most unwanted. If, for instance, @samp{text/html} parts are
315 very unwanted, and @samp{text/richtext} parts are somewhat unwanted,
316 you could say something like:
319 (setq mm-discouraged-alternatives
320 '("text/html" "text/richtext")
322 (remove "text/html" mm-automatic-display))
325 Adding @code{"image/.*"} might also be useful. Spammers use it as the
326 prefered part of @samp{multipart/alternative} messages, and you might
327 not notice there are other parts. See also
328 @code{gnus-buttonized-mime-types} (@pxref{MIME Commands, ,MIME Commands,
329 gnus, Gnus Manual}), to which adding @code{"multipart/alternative"}
330 enables you to choose manually one of two types those mails include.
331 For example, you can set those variables like:
334 (setq gnus-buttonized-mime-types
335 '("multipart/alternative" "multipart/signed")
336 mm-discouraged-alternatives
337 '("text/html" "image/.*"))
340 In this case, Gnus will display radio buttons for such a kind of spam
344 1. (*) multipart/alternative ( ) image/gif
346 2. (*) text/plain ( ) text/html
349 @item mm-inline-large-images
350 @vindex mm-inline-large-images
351 When displaying inline images that are larger than the window, Emacs
352 does not enable scrolling, which means that you cannot see the whole
353 image. To prevent this, the library tries to determine the image size
354 before displaying it inline, and if it doesn't fit the window, the
355 library will display it externally (e.g. with @samp{ImageMagick} or
356 @samp{xv}). Setting this variable to @code{t} disables this check and
357 makes the library display all inline images as inline, regardless of
360 @item mm-inline-override-types
361 @vindex mm-inline-override-types
362 @code{mm-inlined-types} may include regular expressions, for example to
363 specify that all @samp{text/.*} parts be displayed inline. If a user
364 prefers to have a type that matches such a regular expression be treated
365 as an attachment, that can be accomplished by setting this variable to a
366 list containing that type. For example assuming @code{mm-inlined-types}
367 includes @samp{text/.*}, then including @samp{text/html} in this
368 variable will cause @samp{text/html} parts to be treated as attachments.
370 @item mm-text-html-renderer
371 @vindex mm-text-html-renderer
372 This selects the function used to render @acronym{HTML}. The predefined
373 renderers are selected by the symbols @code{w3},
374 @code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
375 information about emacs-w3m}, @code{links}, @code{lynx},
376 @code{w3m-standalone} or @code{html2text}. If @code{nil} use an
377 external viewer. You can also specify a function, which will be
378 called with a @acronym{MIME} handle as the argument.
380 @item mm-inline-text-html-with-images
381 @vindex mm-inline-text-html-with-images
382 Some @acronym{HTML} mails might have the trick of spammers using
383 @samp{<img>} tags. It is likely to be intended to verify whether you
384 have read the mail. You can prevent your personal informations from
385 leaking by setting this option to @code{nil} (which is the default).
386 It is currently ignored by Emacs/w3. For emacs-w3m, you may use the
387 command @kbd{t} on the image anchor to show an image even if it is
388 @code{nil}.@footnote{The command @kbd{T} will load all images. If you
389 have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
392 @item mm-w3m-safe-url-regexp
393 @vindex mm-w3m-safe-url-regexp
394 A regular expression that matches safe URL names, i.e. URLs that are
395 unlikely to leak personal information when rendering @acronym{HTML}
396 email (the default value is @samp{\\`cid:}). If @code{nil} consider
399 @item mm-inline-text-html-with-w3m-keymap
400 @vindex mm-inline-text-html-with-w3m-keymap
401 You can use emacs-w3m command keys in the inlined text/html part by
402 setting this option to non-@code{nil}. The default value is @code{t}.
404 @item mm-external-terminal-program
405 @vindex mm-external-terminal-program
406 The program used to start an external terminal.
408 @item mm-enable-external
409 @vindex mm-enable-external
410 Indicate whether external @acronym{MIME} handlers should be used.
412 If @code{t}, all defined external @acronym{MIME} handlers are used. If
413 @code{nil}, files are saved to disk (@code{mailcap-save-binary-file}).
414 If it is the symbol @code{ask}, you are prompted before the external
415 @acronym{MIME} handler is invoked.
417 When you launch an attachment through mailcap (@pxref{mailcap}) an
418 attempt is made to use a safe viewer with the safest options---this isn't
419 the case if you save it to disk and launch it in a different way
420 (command line or double-clicking). Anyhow, if you want to be sure not
421 to launch any external programs, set this variable to @code{nil} or
426 @node Files and Directories
427 @section Files and Directories
431 @item mm-default-directory
432 @vindex mm-default-directory
433 The default directory for saving attachments. If @code{nil} use
434 @code{default-directory}.
436 @item mm-tmp-directory
437 @vindex mm-tmp-directory
438 Directory for storing temporary files.
440 @item mm-file-name-rewrite-functions
441 @vindex mm-file-name-rewrite-functions
442 A list of functions used for rewriting file names of @acronym{MIME}
443 parts. Each function is applied successively to the file name.
444 Ready-made functions include
447 @item mm-file-name-delete-control
448 @findex mm-file-name-delete-control
449 Delete all control characters.
451 @item mm-file-name-delete-gotchas
452 @findex mm-file-name-delete-gotchas
453 Delete characters that could have unintended consequences when used
454 with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
455 @samp{-}, @samp{.} as the first character.
457 @item mm-file-name-delete-whitespace
458 @findex mm-file-name-delete-whitespace
459 Remove all whitespace.
461 @item mm-file-name-trim-whitespace
462 @findex mm-file-name-trim-whitespace
463 Remove leading and trailing whitespace.
465 @item mm-file-name-collapse-whitespace
466 @findex mm-file-name-collapse-whitespace
467 Collapse multiple whitespace characters.
469 @item mm-file-name-replace-whitespace
470 @findex mm-file-name-replace-whitespace
471 @vindex mm-file-name-replace-whitespace
472 Replace whitespace with underscores. Set the variable
473 @code{mm-file-name-replace-whitespace} to any other string if you do
474 not like underscores.
477 The standard Emacs functions @code{capitalize}, @code{downcase},
478 @code{upcase} and @code{upcase-initials} might also prove useful.
480 @item mm-path-name-rewrite-functions
481 @vindex mm-path-name-rewrite-functions
482 List of functions used for rewriting the full file names of @acronym{MIME}
483 parts. This is used when viewing parts externally, and is meant for
484 transforming the absolute name so that non-compliant programs can find
485 the file where it's saved.
492 Here's an example viewer for displaying @code{text/enriched} inline:
495 (defun mm-display-enriched-inline (handle)
498 (mm-insert-part handle)
499 (save-window-excursion
500 (enriched-decode (point-min) (point-max))
501 (setq text (buffer-string))))
502 (mm-insert-inline handle text)))
505 We see that the function takes a @acronym{MIME} handle as its parameter. It
506 then goes to a temporary buffer, inserts the text of the part, does some
507 work on the text, stores the result, goes back to the buffer it was
508 called from and inserts the result.
510 The two important helper functions here are @code{mm-insert-part} and
511 @code{mm-insert-inline}. The first function inserts the text of the
512 handle in the current buffer. It handles charset and/or content
513 transfer decoding. The second function just inserts whatever text you
514 tell it to insert, but it also sets things up so that the text can be
515 ``undisplayed'' in a convenient manner.
521 @cindex MIME Composing
523 @cindex MIME Meta Language
525 Creating a @acronym{MIME} message is boring and non-trivial. Therefore,
526 a library called @code{mml} has been defined that parses a language
527 called @acronym{MML} (@acronym{MIME} Meta Language) and generates
528 @acronym{MIME} messages.
530 @findex mml-generate-mime
531 The main interface function is @code{mml-generate-mime}. It will
532 examine the contents of the current (narrowed-to) buffer and return a
533 string containing the @acronym{MIME} message.
536 * Simple MML Example:: An example @acronym{MML} document.
537 * MML Definition:: All valid @acronym{MML} elements.
538 * Advanced MML Example:: Another example @acronym{MML} document.
539 * Encoding Customization:: Variables that affect encoding.
540 * Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
541 * Conversion:: Going from @acronym{MIME} to @acronym{MML} and vice versa.
542 * Flowed text:: Soft and hard newlines.
546 @node Simple MML Example
547 @section Simple MML Example
549 Here's a simple @samp{multipart/alternative}:
552 <#multipart type=alternative>
553 This is a plain text part.
554 <#part type=text/enriched>
555 <center>This is a centered enriched part</center>
559 After running this through @code{mml-generate-mime}, we get this:
562 Content-Type: multipart/alternative; boundary="=-=-="
568 This is a plain text part.
571 Content-Type: text/enriched
574 <center>This is a centered enriched part</center>
581 @section MML Definition
583 The @acronym{MML} language is very simple. It looks a bit like an SGML
584 application, but it's not.
586 The main concept of @acronym{MML} is the @dfn{part}. Each part can be of a
587 different type or use a different charset. The way to delineate a part
588 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
589 with the @samp{<#multipart ...>} tag. Parts are ended by the
590 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
591 @samp{<#part ...>} tags are also closed by the next open tag.
593 There's also the @samp{<#external ...>} tag. These introduce
594 @samp{external/message-body} parts.
596 Each tag can contain zero or more parameters on the form
597 @samp{parameter=value}. The values may be enclosed in quotation marks,
598 but that's not necessary unless the value contains white space. So
599 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
601 The following parameters have meaning in @acronym{MML}; parameters that have no
602 meaning are ignored. The @acronym{MML} parameter names are the same as the
603 @acronym{MIME} parameter names; the things in the parentheses say which
604 header it will be used in.
608 The @acronym{MIME} type of the part (@code{Content-Type}).
611 Use the contents of the file in the body of the part
612 (@code{Content-Disposition}).
615 The contents of the body of the part are to be encoded in the character
616 set specified (@code{Content-Type}). @xref{Charset Translation}.
619 Might be used to suggest a file name if the part is to be saved
620 to a file (@code{Content-Type}).
623 Valid values are @samp{inline} and @samp{attachment}
624 (@code{Content-Disposition}).
627 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
628 @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
632 A description of the part (@code{Content-Description}).
635 RFC822 date when the part was created (@code{Content-Disposition}).
637 @item modification-date
638 RFC822 date when the part was modified (@code{Content-Disposition}).
641 RFC822 date when the part was read (@code{Content-Disposition}).
644 Who to encrypt/sign the part to. This field is used to override any
645 auto-detection based on the To/CC headers.
648 Identity used to sign the part. This field is used to override the
652 The size (in octets) of the part (@code{Content-Disposition}).
655 What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
659 What technology to encrypt this @acronym{MML} part with (@code{smime},
660 @code{pgp} or @code{pgpmime})
664 Parameters for @samp{text/plain}:
668 Formatting parameter for the text, valid values include @samp{fixed}
669 (the default) and @samp{flowed}. Normally you do not specify this
670 manually, since it requires the textual body to be formatted in a
671 special way described in RFC 2646. @xref{Flowed text}.
674 Parameters for @samp{application/octet-stream}:
678 Type of the part; informal---meant for human readers
679 (@code{Content-Type}).
682 Parameters for @samp{message/external-body}:
686 A word indicating the supported access mechanism by which the file may
687 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
688 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
691 The RFC822 date after which the file may no longer be fetched.
692 (@code{Content-Type}.)
695 The size (in octets) of the file. (@code{Content-Type}.)
698 Valid values are @samp{read} and @samp{read-write}
699 (@code{Content-Type}).
703 Parameters for @samp{sign=smime}:
708 File containing key and certificate for signer.
712 Parameters for @samp{encrypt=smime}:
717 File containing certificate for recipient.
722 @node Advanced MML Example
723 @section Advanced MML Example
725 Here's a complex multipart message. It's a @samp{multipart/mixed} that
726 contains many parts, one of which is a @samp{multipart/alternative}.
729 <#multipart type=mixed>
730 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
731 <#multipart type=alternative>
732 This is a plain text part.
733 <#part type=text/enriched name=enriched.txt>
734 <center>This is a centered enriched part</center>
736 This is a new plain text part.
737 <#part disposition=attachment>
738 This plain text part is an attachment.
742 And this is the resulting @acronym{MIME} message:
745 Content-Type: multipart/mixed; boundary="=-=-="
753 Content-Type: image/jpeg;
755 Content-Disposition: inline;
757 Content-Transfer-Encoding: base64
759 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
760 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
761 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
762 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
763 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
764 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
765 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
766 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
767 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
768 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
769 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
770 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
771 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
772 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
773 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
774 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
775 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
778 Content-Type: multipart/alternative; boundary="==-=-="
784 This is a plain text part.
787 Content-Type: text/enriched;
791 <center>This is a centered enriched part</center>
797 This is a new plain text part.
800 Content-Disposition: attachment
803 This plain text part is an attachment.
808 @node Encoding Customization
809 @section Encoding Customization
813 @item mm-body-charset-encoding-alist
814 @vindex mm-body-charset-encoding-alist
815 Mapping from @acronym{MIME} charset to encoding to use. This variable is
816 usually used except, e.g., when other requirements force a specific
817 encoding (digitally signed messages require 7bit encodings). The
821 ((iso-2022-jp . 7bit)
822 (iso-2022-jp-2 . 7bit)
828 As an example, if you do not want to have ISO-8859-1 characters
829 quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
830 this variable. You can override this setting on a per-message basis
831 by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
833 @item mm-coding-system-priorities
834 @vindex mm-coding-system-priorities
835 Prioritize coding systems to use for outgoing messages. The default
836 is @code{nil}, which means to use the defaults in Emacs, but is
837 @code{(iso-8859-1 iso-2022-jp iso-2022-jp-2 shift_jis utf-8)} when
838 running Emacs in the Japanese language environment. It is a list of
839 coding system symbols (aliases of coding systems are also allowed, use
840 @kbd{M-x describe-coding-system} to make sure you are specifying correct
841 coding system names). For example, if you have configured Emacs
842 to prefer UTF-8, but wish that outgoing messages should be sent in
843 ISO-8859-1 if possible, you can set this variable to
844 @code{(iso-8859-1)}. You can override this setting on a per-message
845 basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
847 @item mm-content-transfer-encoding-defaults
848 @vindex mm-content-transfer-encoding-defaults
849 Mapping from @acronym{MIME} types to encoding to use. This variable is usually
850 used except, e.g., when other requirements force a safer encoding
851 (digitally signed messages require 7bit encoding). Besides the normal
852 @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
853 each case the most efficient of quoted-printable and base64 should be
856 @code{qp-or-base64} has another effect. It will fold long lines so that
857 MIME parts may not be broken by MTA. So do @code{quoted-printable} and
860 Note that it affects body encoding only when a part is a raw forwarded
861 message (which will be made by @code{gnus-summary-mail-forward} with the
862 arg 2 for example) or is neither the @samp{text/*} type nor the
863 @samp{message/*} type. Even though in those cases, you can override
864 this setting on a per-message basis by using the @code{encoding}
865 @acronym{MML} tag (@pxref{MML Definition}).
867 @item mm-use-ultra-safe-encoding
868 @vindex mm-use-ultra-safe-encoding
869 When this is non-@code{nil}, it means that textual parts are encoded as
870 quoted-printable if they contain lines longer than 76 characters or
871 starting with "From " in the body. Non-7bit encodings (8bit, binary)
872 are generally disallowed. This reduce the probability that a non-8bit
873 clean MTA or MDA changes the message. This should never be set
874 directly, but bound by other functions when necessary (e.g., when
875 encoding messages that are to be digitally signed).
879 @node Charset Translation
880 @section Charset Translation
883 During translation from @acronym{MML} to @acronym{MIME}, for each
884 @acronym{MIME} part which has been composed inside Emacs, an appropriate
885 charset has to be chosen.
887 @vindex mail-parse-charset
888 If you are running a non-@sc{mule} Emacs, this process is simple: If the
889 part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
890 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
891 variable directly, though. If you want to change the default charset,
892 please consult the documentation of the package which you use to process
893 @acronym{MIME} messages.
894 @xref{Various Message Variables, , Various Message Variables, message,
895 Message Manual}, for example.)
896 If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
902 @vindex mm-mime-mule-charset-alist
903 Things are slightly more complicated when running Emacs with @sc{mule}
904 support. In this case, a list of the @sc{mule} charsets used in the
905 part is obtained, and the @sc{mule} charsets are translated to
906 @acronym{MIME} charsets by consulting the table provided by Emacs itself
907 or the variable @code{mm-mime-mule-charset-alist} for XEmacs.
908 If this results in a single @acronym{MIME} charset, this is used to encode
909 the part. But if the resulting list of @acronym{MIME} charsets contains more
910 than one element, two things can happen: If it is possible to encode the
911 part via UTF-8, this charset is used. (For this, Emacs must support
912 the @code{utf-8} coding system, and the part must consist entirely of
913 characters which have Unicode counterparts.) If UTF-8 is not available
914 for some reason, the part is split into several ones, so that each one
915 can be encoded with a single @acronym{MIME} charset. The part can only be
916 split at line boundaries, though---if more than one @acronym{MIME} charset is
917 required to encode a single line, it is not possible to encode the part.
919 When running Emacs with @sc{mule} support, the preferences for which
920 coding system to use is inherited from Emacs itself. This means that
921 if Emacs is set up to prefer UTF-8, it will be used when encoding
922 messages. You can modify this by altering the
923 @code{mm-coding-system-priorities} variable though (@pxref{Encoding
926 The charset to be used can be overridden by setting the @code{charset}
927 @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
929 The encoding of characters (quoted-printable, 8bit etc) is orthogonal
930 to the discussion here, and is controlled by the variables
931 @code{mm-body-charset-encoding-alist} and
932 @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
939 A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
940 with the @code{mime-to-mml} function. It works on the message in the
941 current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
942 boundaries. Non-textual parts do not have their contents in the buffer,
943 but instead have the contents in separate buffers that are referred to
944 from the @acronym{MML} tags.
947 An @acronym{MML} message can be converted back to @acronym{MIME} by the
948 @code{mml-to-mime} function.
950 These functions are in certain senses ``lossy''---you will not get back
951 an identical message if you run @code{mime-to-mml} and then
952 @code{mml-to-mime}. Not only will trivial things like the order of the
953 headers differ, but the contents of the headers may also be different.
954 For instance, the original message may use base64 encoding on text,
955 while @code{mml-to-mime} may decide to use quoted-printable encoding, and
958 In essence, however, these two functions should be the inverse of each
959 other. The resulting contents of the message should remain equivalent,
965 @cindex format=flowed
967 The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
968 variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
969 emacs, Emacs Manual}) when encoding a message, and the
970 ``format=flowed'' Content-Type parameter when decoding a message.
972 On encoding text, regardless of @code{use-hard-newlines}, lines
973 terminated by soft newline characters are filled together and wrapped
974 after the column decided by @code{fill-flowed-encode-column}.
975 Quotation marks (matching @samp{^>* ?}) are respected. The variable
976 controls how the text will look in a client that does not support
977 flowed text, the default is to wrap after 66 characters. If hard
978 newline characters are not present in the buffer, no flow encoding
981 On decoding flowed text, lines with soft newline characters are filled
982 together and wrapped after the column decided by
983 @code{fill-flowed-display-column}. The default is to wrap after
988 @vindex mm-fill-flowed
989 If non-@code{nil} a format=flowed article will be displayed flowed.
993 @node Interface Functions
994 @chapter Interface Functions
995 @cindex interface functions
998 The @code{mail-parse} library is an abstraction over the actual
999 low-level libraries that are described in the next chapter.
1001 Standards change, and so programs have to change to fit in the new
1002 mold. For instance, RFC2045 describes a syntax for the
1003 @code{Content-Type} header that only allows @acronym{ASCII} characters in the
1004 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
1005 for continuation headers and non-@acronym{ASCII} characters.
1007 The traditional way to deal with this is just to update the library
1008 functions to parse the new syntax. However, this is sometimes the wrong
1009 thing to do. In some instances it may be vital to be able to understand
1010 both the old syntax as well as the new syntax, and if there is only one
1011 library, one must choose between the old version of the library and the
1012 new version of the library.
1014 The Emacs @acronym{MIME} library takes a different tack. It defines a
1015 series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
1016 and so on) that parses strictly according to the corresponding
1017 standard. However, normal programs would not use the functions
1018 provided by these libraries directly, but instead use the functions
1019 provided by the @code{mail-parse} library. The functions in this
1020 library are just aliases to the corresponding functions in the latest
1021 low-level libraries. Using this scheme, programs get a consistent
1022 interface they can use, and library developers are free to create
1023 write code that handles new standards.
1025 The following functions are defined by this library:
1028 @item mail-header-parse-content-type
1029 @findex mail-header-parse-content-type
1030 Parse a @code{Content-Type} header and return a list on the following
1035 (attribute1 . value1)
1036 (attribute2 . value2)
1043 (mail-header-parse-content-type
1044 "image/gif; name=\"b980912.gif\"")
1045 @result{} ("image/gif" (name . "b980912.gif"))
1048 @item mail-header-parse-content-disposition
1049 @findex mail-header-parse-content-disposition
1050 Parse a @code{Content-Disposition} header and return a list on the same
1051 format as the function above.
1053 @item mail-content-type-get
1054 @findex mail-content-type-get
1055 Takes two parameters---a list on the format above, and an attribute.
1056 Returns the value of the attribute.
1059 (mail-content-type-get
1060 '("image/gif" (name . "b980912.gif")) 'name)
1061 @result{} "b980912.gif"
1064 @item mail-header-encode-parameter
1065 @findex mail-header-encode-parameter
1066 Takes a parameter string and returns an encoded version of the string.
1067 This is used for parameters in headers like @code{Content-Type} and
1068 @code{Content-Disposition}.
1070 @item mail-header-remove-comments
1071 @findex mail-header-remove-comments
1072 Return a comment-free version of a header.
1075 (mail-header-remove-comments
1076 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1077 @result{} "Gnus/5.070027 "
1080 @item mail-header-remove-whitespace
1081 @findex mail-header-remove-whitespace
1082 Remove linear white space from a header. Space inside quoted strings
1083 and comments is preserved.
1086 (mail-header-remove-whitespace
1087 "image/gif; name=\"Name with spaces\"")
1088 @result{} "image/gif;name=\"Name with spaces\""
1091 @item mail-header-get-comment
1092 @findex mail-header-get-comment
1093 Return the last comment in a header.
1096 (mail-header-get-comment
1097 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1098 @result{} "Finnish Landrace"
1101 @item mail-header-parse-address
1102 @findex mail-header-parse-address
1103 Parse an address and return a list containing the mailbox and the
1107 (mail-header-parse-address
1108 "Hrvoje Niksic <hniksic@@srce.hr>")
1109 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
1112 @item mail-header-parse-addresses
1113 @findex mail-header-parse-addresses
1114 Parse a string with list of addresses and return a list of elements like
1115 the one described above.
1118 (mail-header-parse-addresses
1119 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
1120 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
1121 ("sb@@metis.no" . "Steinar Bang"))
1124 @item mail-header-parse-date
1125 @findex mail-header-parse-date
1126 Parse a date string and return an Emacs time structure.
1128 @item mail-narrow-to-head
1129 @findex mail-narrow-to-head
1130 Narrow the buffer to the header section of the buffer. Point is placed
1131 at the beginning of the narrowed buffer.
1133 @item mail-header-narrow-to-field
1134 @findex mail-header-narrow-to-field
1135 Narrow the buffer to the header under point. Understands continuation
1138 @item mail-header-fold-field
1139 @findex mail-header-fold-field
1140 Fold the header under point.
1142 @item mail-header-unfold-field
1143 @findex mail-header-unfold-field
1144 Unfold the header under point.
1146 @item mail-header-field-value
1147 @findex mail-header-field-value
1148 Return the value of the field under point.
1150 @item mail-encode-encoded-word-region
1151 @findex mail-encode-encoded-word-region
1152 Encode the non-@acronym{ASCII} words in the region. For instance,
1153 @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
1155 @item mail-encode-encoded-word-buffer
1156 @findex mail-encode-encoded-word-buffer
1157 Encode the non-@acronym{ASCII} words in the current buffer. This function is
1158 meant to be called narrowed to the headers of a message.
1160 @item mail-encode-encoded-word-string
1161 @findex mail-encode-encoded-word-string
1162 Encode the words that need encoding in a string, and return the result.
1165 (mail-encode-encoded-word-string
1166 "This is naïve, baby")
1167 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
1170 @item mail-decode-encoded-word-region
1171 @findex mail-decode-encoded-word-region
1172 Decode the encoded words in the region.
1174 @item mail-decode-encoded-word-string
1175 @findex mail-decode-encoded-word-string
1176 Decode the encoded words in the string and return the result.
1179 (mail-decode-encoded-word-string
1180 "This is =?iso-8859-1?q?na=EFve,?= baby")
1181 @result{} "This is naïve, baby"
1186 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
1187 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
1188 in the subsequent sections.
1192 @node Basic Functions
1193 @chapter Basic Functions
1195 This chapter describes the basic, ground-level functions for parsing and
1196 handling. Covered here is parsing @code{From} lines, removing comments
1197 from header lines, decoding encoded words, parsing date headers and so
1198 on. High-level functionality is dealt with in the first chapter
1199 (@pxref{Decoding and Viewing}).
1202 * rfc2045:: Encoding @code{Content-Type} headers.
1203 * rfc2231:: Parsing @code{Content-Type} headers.
1204 * ietf-drums:: Handling mail headers defined by RFC822bis.
1205 * rfc2047:: En/decoding encoded words in headers.
1206 * time-date:: Functions for parsing dates and manipulating time.
1207 * qp:: Quoted-Printable en/decoding.
1208 * base64:: Base64 en/decoding.
1209 * binhex:: Binhex decoding.
1210 * uudecode:: Uuencode decoding.
1211 * yenc:: Yenc decoding.
1212 * rfc1843:: Decoding HZ-encoded text.
1213 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
1220 RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
1221 imagine that there would be a lot to implement. But there isn't, since
1222 most of the implementation details are delegated to the subsequent
1225 So @file{rfc2045.el} has only a single function:
1228 @item rfc2045-encode-string
1229 @findex rfc2045-encode-string
1230 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
1231 @var{value} will be quoted if there are non-safe characters in it.
1238 RFC2231 defines a syntax for the @code{Content-Type} and
1239 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
1240 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
1243 In short, these headers look something like this:
1246 Content-Type: application/x-stuff;
1247 title*0*=us-ascii'en'This%20is%20even%20more%20;
1248 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1252 They usually aren't this bad, though.
1254 The following functions are defined by this library:
1257 @item rfc2231-parse-string
1258 @findex rfc2231-parse-string
1259 Parse a @code{Content-Type} header and return a list describing its
1263 (rfc2231-parse-string
1264 "application/x-stuff;
1265 title*0*=us-ascii'en'This%20is%20even%20more%20;
1266 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1267 title*2=\"isn't it!\"")
1268 @result{} ("application/x-stuff"
1269 (title . "This is even more ***fun*** isn't it!"))
1272 @item rfc2231-get-value
1273 @findex rfc2231-get-value
1274 Takes one of the lists on the format above and returns
1275 the value of the specified attribute.
1277 @item rfc2231-encode-string
1278 @findex rfc2231-encode-string
1279 Encode a parameter in headers likes @code{Content-Type} and
1280 @code{Content-Disposition}.
1288 @dfn{drums} is an IETF working group that is working on the replacement
1291 The functions provided by this library include:
1294 @item ietf-drums-remove-comments
1295 @findex ietf-drums-remove-comments
1296 Remove the comments from the argument and return the results.
1298 @item ietf-drums-remove-whitespace
1299 @findex ietf-drums-remove-whitespace
1300 Remove linear white space from the string and return the results.
1301 Spaces inside quoted strings and comments are left untouched.
1303 @item ietf-drums-get-comment
1304 @findex ietf-drums-get-comment
1305 Return the last most comment from the string.
1307 @item ietf-drums-parse-address
1308 @findex ietf-drums-parse-address
1309 Parse an address string and return a list that contains the mailbox and
1310 the plain text name.
1312 @item ietf-drums-parse-addresses
1313 @findex ietf-drums-parse-addresses
1314 Parse a string that contains any number of comma-separated addresses and
1315 return a list that contains mailbox/plain text pairs.
1317 @item ietf-drums-parse-date
1318 @findex ietf-drums-parse-date
1319 Parse a date string and return an Emacs time structure.
1321 @item ietf-drums-narrow-to-header
1322 @findex ietf-drums-narrow-to-header
1323 Narrow the buffer to the header section of the current buffer.
1331 RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
1332 non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
1333 complicated, so a number of variables are necessary to tweak what this
1336 The following variables are tweakable:
1339 @item rfc2047-header-encoding-alist
1340 @vindex rfc2047-header-encoding-alist
1341 This is an alist of header / encoding-type pairs. Its main purpose is
1342 to prevent encoding of certain headers.
1344 The keys can either be header regexps, or @code{t}.
1346 The values can be @code{nil}, in which case the header(s) in question
1347 won't be encoded, @code{mime}, which means that they will be encoded, or
1348 @code{address-mime}, which means the header(s) will be encoded carefully
1349 assuming they contain addresses.
1351 @item rfc2047-charset-encoding-alist
1352 @vindex rfc2047-charset-encoding-alist
1353 RFC2047 specifies two forms of encoding---@code{Q} (a
1354 Quoted-Printable-like encoding) and @code{B} (base64). This alist
1355 specifies which charset should use which encoding.
1357 @item rfc2047-encode-function-alist
1358 @vindex rfc2047-encode-function-alist
1359 This is an alist of encoding / function pairs. The encodings are
1360 @code{Q}, @code{B} and @code{nil}.
1362 @item rfc2047-encoded-word-regexp
1363 @vindex rfc2047-encoded-word-regexp
1364 When decoding words, this library looks for matches to this regexp.
1366 @item rfc2047-encode-encoded-words
1367 @vindex rfc2047-encode-encoded-words
1368 The boolean variable specifies whether encoded words
1369 (e.g. @samp{=?hello?=}) should be encoded again.
1373 Those were the variables, and these are this functions:
1376 @item rfc2047-narrow-to-field
1377 @findex rfc2047-narrow-to-field
1378 Narrow the buffer to the header on the current line.
1380 @item rfc2047-encode-message-header
1381 @findex rfc2047-encode-message-header
1382 Should be called narrowed to the header of a message. Encodes according
1383 to @code{rfc2047-header-encoding-alist}.
1385 @item rfc2047-encode-region
1386 @findex rfc2047-encode-region
1387 Encodes all encodable words in the region specified.
1389 @item rfc2047-encode-string
1390 @findex rfc2047-encode-string
1391 Encode a string and return the results.
1393 @item rfc2047-decode-region
1394 @findex rfc2047-decode-region
1395 Decode the encoded words in the region.
1397 @item rfc2047-decode-string
1398 @findex rfc2047-decode-string
1399 Decode a string and return the results.
1401 @item rfc2047-encode-parameter
1402 @findex rfc2047-encode-parameter
1403 Encode a parameter in the RFC2047-like style. This is a replacement for
1404 the @code{rfc2231-encode-string} function. @xref{rfc2231}.
1406 When attaching files as @acronym{MIME} parts, we should use the RFC2231
1407 encoding to specify the file names containing non-@acronym{ASCII}
1408 characters. However, many mail softwares don't support it in practice
1409 and recipients won't be able to extract files with correct names.
1410 Instead, the RFC2047-like encoding is acceptable generally. This
1411 function provides the very RFC2047-like encoding, resigning to such a
1412 regrettable trend. To use it, put the following line in your
1413 @file{~/.gnus.el} file:
1416 (defalias 'mail-header-encode-parameter 'rfc2047-encode-parameter)
1425 While not really a part of the @acronym{MIME} library, it is convenient to
1426 document this library here. It deals with parsing @code{Date} headers
1427 and manipulating time. (Not by using tesseracts, though, I'm sorry to
1430 These functions convert between five formats: A date string, an Emacs
1431 time structure, a decoded time list, a second number, and a day number.
1433 Here's a bunch of time/date/second/day examples:
1436 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
1437 @result{} (54 21 12 12 9 1998 6 nil 7200)
1439 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
1440 @result{} (13818 19266)
1442 (time-to-seconds '(13818 19266))
1443 @result{} 905595714.0
1445 (seconds-to-time 905595714.0)
1446 @result{} (13818 19266 0)
1448 (time-to-days '(13818 19266))
1451 (days-to-time 729644)
1452 @result{} (961933 65536)
1454 (time-since '(13818 19266))
1457 (time-less-p '(13818 19266) '(13818 19145))
1460 (subtract-time '(13818 19266) '(13818 19145))
1463 (days-between "Sat Sep 12 12:21:54 1998 +0200"
1464 "Sat Sep 07 12:21:54 1998 +0200")
1467 (date-leap-year-p 2000)
1470 (time-to-day-in-year '(13818 19266))
1473 (time-to-number-of-days
1475 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
1476 @result{} 4.146122685185185
1479 And finally, we have @code{safe-date-to-time}, which does the same as
1480 @code{date-to-time}, but returns a zero time if the date is
1481 syntactically malformed.
1483 The five data representations used are the following:
1487 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
1488 12:21:54 1998 +0200"}.
1491 An internal Emacs time. For instance: @code{(13818 26466)}.
1494 A floating point representation of the internal Emacs time. For
1495 instance: @code{905595714.0}.
1498 An integer number representing the number of days since 00000101. For
1499 instance: @code{729644}.
1502 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
1506 All the examples above represent the same moment.
1508 These are the functions available:
1512 Take a date and return a time.
1514 @item time-to-seconds
1515 Take a time and return seconds.
1517 @item seconds-to-time
1518 Take seconds and return a time.
1521 Take a time and return days.
1524 Take days and return a time.
1527 Take a date and return days.
1529 @item time-to-number-of-days
1530 Take a time and return the number of days that represents.
1532 @item safe-date-to-time
1533 Take a date and return a time. If the date is not syntactically valid,
1534 return a ``zero'' time.
1537 Take two times and say whether the first time is less (i. e., earlier)
1538 than the second time.
1541 Take a time and return a time saying how long it was since that time.
1544 Take two times and subtract the second from the first. I. e., return
1545 the time between the two times.
1548 Take two days and return the number of days between those two days.
1550 @item date-leap-year-p
1551 Take a year number and say whether it's a leap year.
1553 @item time-to-day-in-year
1554 Take a time and return the day number within the year that the time is
1563 This library deals with decoding and encoding Quoted-Printable text.
1565 Very briefly explained, qp encoding means translating all 8-bit
1566 characters (and lots of control characters) into things that look like
1567 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
1570 The following functions are defined by the library:
1573 @item quoted-printable-decode-region
1574 @findex quoted-printable-decode-region
1575 QP-decode all the encoded text in the specified region.
1577 @item quoted-printable-decode-string
1578 @findex quoted-printable-decode-string
1579 Decode the QP-encoded text in a string and return the results.
1581 @item quoted-printable-encode-region
1582 @findex quoted-printable-encode-region
1583 QP-encode all the encodable characters in the specified region. The third
1584 optional parameter @var{fold} specifies whether to fold long lines.
1585 (Long here means 72.)
1587 @item quoted-printable-encode-string
1588 @findex quoted-printable-encode-string
1589 QP-encode all the encodable characters in a string and return the
1599 Base64 is an encoding that encodes three bytes into four characters,
1600 thereby increasing the size by about 33%. The alphabet used for
1601 encoding is very resistant to mangling during transit.
1603 The following functions are defined by this library:
1606 @item base64-encode-region
1607 @findex base64-encode-region
1608 base64 encode the selected region. Return the length of the encoded
1609 text. Optional third argument @var{no-line-break} means do not break
1610 long lines into shorter lines.
1612 @item base64-encode-string
1613 @findex base64-encode-string
1614 base64 encode a string and return the result.
1616 @item base64-decode-region
1617 @findex base64-decode-region
1618 base64 decode the selected region. Return the length of the decoded
1619 text. If the region can't be decoded, return @code{nil} and don't
1622 @item base64-decode-string
1623 @findex base64-decode-string
1624 base64 decode a string and return the result. If the string can't be
1625 decoded, @code{nil} is returned.
1636 @code{binhex} is an encoding that originated in Macintosh environments.
1637 The following function is supplied to deal with these:
1640 @item binhex-decode-region
1641 @findex binhex-decode-region
1642 Decode the encoded text in the region. If given a third parameter, only
1643 decode the @code{binhex} header and return the filename.
1652 @code{uuencode} is probably still the most popular encoding of binaries
1653 used on Usenet, although @code{base64} rules the mail world.
1655 The following function is supplied by this package:
1658 @item uudecode-decode-region
1659 @findex uudecode-decode-region
1660 Decode the text in the region.
1668 @code{yenc} is used for encoding binaries on Usenet. The following
1669 function is supplied by this package:
1672 @item yenc-decode-region
1673 @findex yenc-decode-region
1674 Decode the encoded text in the region.
1685 RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
1686 essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
1689 This sentence is in @acronym{ASCII}.
1690 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
1693 Simple enough, and widely used in China.
1695 The following functions are available to handle this encoding:
1698 @item rfc1843-decode-region
1699 Decode HZ-encoded text in the region.
1701 @item rfc1843-decode-string
1702 Decode a HZ-encoded string and return the result.
1710 The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
1711 handlers and describes how elements are supposed to be displayed.
1712 Here's an example file:
1716 audio/wav; wavplayer %s
1717 application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
1720 This says that all image files should be displayed with @code{gimp},
1721 that WAVE audio files should be played by @code{wavplayer}, and that
1722 MS-WORD files should be inlined by @code{catdoc}.
1724 The @code{mailcap} library parses this file, and provides functions for
1728 @item mailcap-mime-data
1729 @vindex mailcap-mime-data
1730 This variable is an alist of alists containing backup viewing rules.
1734 Interface functions:
1737 @item mailcap-parse-mailcaps
1738 @findex mailcap-parse-mailcaps
1739 Parse the @file{~/.mailcap} file.
1741 @item mailcap-mime-info
1742 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
1752 The Emacs @acronym{MIME} library implements handling of various elements
1753 according to a (somewhat) large number of RFCs, drafts and standards
1754 documents. This chapter lists the relevant ones. They can all be
1755 fetched from @uref{http://quimby.gnus.org/notes/}.
1760 Standard for the Format of ARPA Internet Text Messages.
1763 Standard for Interchange of USENET Messages
1766 Format of Internet Message Bodies
1772 Message Header Extensions for Non-@acronym{ASCII} Text
1775 Registration Procedures
1778 Conformance Criteria and Examples
1781 @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
1782 Languages, and Continuations
1785 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1786 @acronym{ASCII} characters
1788 @item draft-ietf-drums-msg-fmt-05.txt
1789 Draft for the successor of RFC822
1792 The @acronym{MIME} Multipart/Related Content-type
1795 The Multipart/Report Content Type for the Reporting of Mail System
1796 Administrative Messages
1799 Communicating Presentation Information in Internet Messages: The
1800 Content-Disposition Header Field
1803 Documentation of the text/plain format parameter for flowed text.
1819 @c coding: iso-8859-1
1823 arch-tag: c7ef2fd0-a91c-4e10-aa52-c1a2b11b1a8d