3 @setfilename emacs-mime
4 @settitle Emacs MIME Manual
10 * Emacs MIME: (emacs-mime). The MIME de/composition library.
12 @documentencoding ISO-8859-1
16 @setchapternewpage odd
20 This file documents the Emacs MIME interface functionality.
22 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004
23 Free Software Foundation, Inc.
25 Permission is granted to copy, distribute and/or modify this document
26 under the terms of the GNU Free Documentation License, Version 1.1 or
27 any later version published by the Free Software Foundation; with no
28 Invariant Sections, with the Front-Cover texts being ``A GNU
29 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
30 license is included in the section entitled ``GNU Free Documentation
31 License'' in the Emacs manual.
33 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
34 this GNU Manual, like GNU software. Copies published by the Free
35 Software Foundation raise funds for GNU development.''
37 This document is part of a collection distributed under the GNU Free
38 Documentation License. If you want to distribute this document
39 separately from the collection, you can do so by adding a copy of the
40 license to the document, as described in section 6 of the license.
46 @title Emacs MIME Manual
48 @author by Lars Magne Ingebrigtsen
51 @vskip 0pt plus 1filll
52 Copyright @copyright{} 1998, 1999, 2000, 2001, 2002, 2003 Free Software
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.1 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being none, with the Front-Cover texts being ``A GNU
59 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
60 license is included in the section entitled ``GNU Free Documentation
61 License'' in the Emacs manual.
63 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
64 this GNU Manual, like GNU software. Copies published by the Free
65 Software Foundation raise funds for GNU development.''
67 This document is part of a collection distributed under the GNU Free
68 Documentation License. If you want to distribute this document
69 separately from the collection, you can do so by adding a copy of the
70 license to the document, as described in section 6 of the license.
79 This manual documents the libraries used to compose and display
80 @acronym{MIME} messages.
82 This manual is directed at users who want to modify the behaviour of
83 the @acronym{MIME} encoding/decoding process or want a more detailed
84 picture of how the Emacs @acronym{MIME} library works, and people who want
85 to write functions and commands that manipulate @acronym{MIME} elements.
87 @acronym{MIME} is short for @dfn{Multipurpose Internet Mail Extensions}.
88 This standard is documented in a number of RFCs; mainly RFC2045 (Format
89 of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
90 Header Extensions for Non-@acronym{ASCII} Text), RFC2048 (Registration
91 Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
92 recommended that anyone who intends writing @acronym{MIME}-compliant software
93 read at least RFC2045 and RFC2047.
96 * Decoding and Viewing:: A framework for decoding and viewing.
97 * Composing:: @acronym{MML}; a language for describing @acronym{MIME} parts.
98 * Interface Functions:: An abstraction over the basic functions.
99 * Basic Functions:: Utility and basic parsing functions.
100 * Standards:: A summary of RFCs and working documents used.
101 * Index:: Function and variable index.
105 @node Decoding and Viewing
106 @chapter Decoding and Viewing
108 This chapter deals with decoding and viewing @acronym{MIME} messages on a
111 The main idea is to first analyze a @acronym{MIME} article, and then allow
112 other programs to do things based on the list of @dfn{handles} that are
113 returned as a result of this analysis.
116 * Dissection:: Analyzing a @acronym{MIME} message.
117 * Non-MIME:: Analyzing a non-@acronym{MIME} message.
118 * Handles:: Handle manipulations.
119 * Display:: Displaying handles.
120 * Display Customization:: Variables that affect display.
121 * Files and Directories:: Saving and naming attachments.
122 * New Viewers:: How to write your own viewers.
129 The @code{mm-dissect-buffer} is the function responsible for dissecting
130 a @acronym{MIME} article. If given a multipart message, it will recursively
131 descend the message, following the structure, and return a tree of
132 @acronym{MIME} handles that describes the structure of the message.
136 @vindex mm-uu-configure-list
138 Gnus also understands some non-@acronym{MIME} attachments, such as
139 postscript, uuencode, binhex, yenc, shar, forward, gnatsweb, pgp,
140 diff. Each of these features can be disabled by add an item into
141 @code{mm-uu-configure-list}. For example,
145 (add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
171 Non-@acronym{MIME} forwarded message.
179 @acronym{PGP} signed clear text.
182 @findex pgp-encrypted
183 @acronym{PGP} encrypted clear text.
187 @acronym{PGP} public keys.
190 @findex emacs-sources
191 @vindex mm-uu-emacs-sources-regexp
192 Emacs source code. This item works only in the groups matching
193 @code{mm-uu-emacs-sources-regexp}.
197 @vindex mm-uu-diff-groups-regexp
198 Patches. This is intended for groups where diffs of committed files
199 are automatically sent to. It only works in groups matching
200 @code{mm-uu-diff-groups-regexp}.
207 A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
210 The following macros can be used to access elements in a handle:
213 @item mm-handle-buffer
214 @findex mm-handle-buffer
215 Return the buffer that holds the contents of the undecoded @acronym{MIME}
219 @findex mm-handle-type
220 Return the parsed @code{Content-Type} of the part.
222 @item mm-handle-encoding
223 @findex mm-handle-encoding
224 Return the @code{Content-Transfer-Encoding} of the part.
226 @item mm-handle-undisplayer
227 @findex mm-handle-undisplayer
228 Return the object that can be used to remove the displayed part (if it
231 @item mm-handle-set-undisplayer
232 @findex mm-handle-set-undisplayer
233 Set the undisplayer object.
235 @item mm-handle-disposition
236 @findex mm-handle-disposition
237 Return the parsed @code{Content-Disposition} of the part.
239 @item mm-handle-disposition
240 @findex mm-handle-disposition
241 Return the description of the part.
243 @item mm-get-content-id
244 Returns the handle(s) referred to by @code{Content-ID}.
252 Functions for displaying, removing and saving.
255 @item mm-display-part
256 @findex mm-display-part
260 @findex mm-remove-part
261 Remove the part (if it has been displayed).
264 @findex mm-inlinable-p
265 Say whether a @acronym{MIME} type can be displayed inline.
267 @item mm-automatic-display-p
268 @findex mm-automatic-display-p
269 Say whether a @acronym{MIME} type should be displayed automatically.
271 @item mm-destroy-part
272 @findex mm-destroy-part
273 Free all resources occupied by a part.
277 Offer to save the part in a file.
281 Offer to pipe the part to some process.
283 @item mm-interactively-view-part
284 @findex mm-interactively-view-part
285 Prompt for a mailcap method to use to view the part.
290 @node Display Customization
291 @section Display Customization
295 @item mm-inline-media-tests
296 @vindex mm-inline-media-tests
297 This is an alist where the key is a @acronym{MIME} type, the second element
298 is a function to display the part @dfn{inline} (i.e., inside Emacs), and
299 the third element is a form to be @code{eval}ed to say whether the part
300 can be displayed inline.
302 This variable specifies whether a part @emph{can} be displayed inline,
303 and, if so, how to do it. It does not say whether parts are
304 @emph{actually} displayed inline.
306 @item mm-inlined-types
307 @vindex mm-inlined-types
308 This, on the other hand, says what types are to be displayed inline, if
309 they satisfy the conditions set by the variable above. It's a list of
310 @acronym{MIME} media types.
312 @item mm-automatic-display
313 @vindex mm-automatic-display
314 This is a list of types that are to be displayed ``automatically'', but
315 only if the above variable allows it. That is, only inlinable parts can
316 be displayed automatically.
318 @item mm-automatic-external-display
319 @vindex mm-automatic-external-display
320 This is a list of types that will be displayed automatically in an
323 @item mm-keep-viewer-alive-types
324 @vindex mm-keep-viewer-alive-types
325 This is a list of media types for which the external viewer will not
326 be killed when selecting a different article.
328 @item mm-attachment-override-types
329 @vindex mm-attachment-override-types
330 Some @acronym{MIME} agents create parts that have a content-disposition of
331 @samp{attachment}. This variable allows overriding that disposition and
332 displaying the part inline. (Note that the disposition is only
333 overridden if we are able to, and want to, display the part inline.)
335 @item mm-discouraged-alternatives
336 @vindex mm-discouraged-alternatives
337 List of @acronym{MIME} types that are discouraged when viewing
338 @samp{multipart/alternative}. Viewing agents are supposed to view the
339 last possible part of a message, as that is supposed to be the richest.
340 However, users may prefer other types instead, and this list says what
341 types are most unwanted. If, for instance, @samp{text/html} parts are
342 very unwanted, and @samp{text/richtext} parts are somewhat unwanted,
343 you could say something like:
346 (setq mm-discouraged-alternatives
347 '("text/html" "text/richtext")
349 (remove "text/html" mm-automatic-display))
352 @item mm-inline-large-images
353 @vindex mm-inline-large-images
354 When displaying inline images that are larger than the window, XEmacs
355 does not enable scrolling, which means that you cannot see the whole
356 image. To prevent this, the library tries to determine the image size
357 before displaying it inline, and if it doesn't fit the window, the
358 library will display it externally (e.g. with @samp{ImageMagick} or
359 @samp{xv}). Setting this variable to @code{t} disables this check and
360 makes the library display all inline images as inline, regardless of
363 @item mm-inline-override-types
364 @vindex mm-inline-override-types
365 @code{mm-inlined-types} may include regular expressions, for example to
366 specify that all @samp{text/.*} parts be displayed inline. If a user
367 prefers to have a type that matches such a regular expression be treated
368 as an attachment, that can be accomplished by setting this variable to a
369 list containing that type. For example assuming @code{mm-inlined-types}
370 includes @samp{text/.*}, then including @samp{text/html} in this
371 variable will cause @samp{text/html} parts to be treated as attachments.
373 @item mm-text-html-renderer
374 @vindex mm-text-html-renderer
375 This selects the function used to render @acronym{HTML}. The predefined
376 renderers are selected by the symbols @code{w3},
377 @code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
378 information about emacs-w3m}, @code{links}, @code{lynx},
379 @code{w3m-standalone} or @code{html2text}. If @code{nil} use an
380 external viewer. You can also specify a function, which will be
381 called with a @acronym{MIME} handle as the argument.
383 @item mm-inline-text-html-with-images
384 @vindex mm-inline-text-html-with-images
385 Some @acronym{HTML} mails might have the trick of spammers using
386 @samp{<img>} tags. It is likely to be intended to verify whether you
387 have read the mail. You can prevent your personal informations from
388 leaking by setting this option to @code{nil} (which is the default).
389 It is currently ignored by Emacs/w3. For emacs-w3m, you may use the
390 command @kbd{t} on the image anchor to show an image even if it is
391 @code{nil}.@footnote{The command @kbd{T} will load all images. If you
392 have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
395 @item mm-w3m-safe-url-regexp
396 @vindex mm-w3m-safe-url-regexp
397 A regular expression that matches safe URL names, i.e. URLs that are
398 unlikely to leak personal information when rendering @acronym{HTML}
399 email (the default value is @samp{\\`cid:}). If @code{nil} consider
402 @item mm-inline-text-html-with-w3m-keymap
403 @vindex mm-inline-text-html-with-w3m-keymap
404 You can use emacs-w3m command keys in the inlined text/html part by
405 setting this option to non-@code{nil}. The default value is @code{t}.
407 @item mm-external-terminal-program
408 @vindex mm-external-terminal-program
409 The program used to start an external terminal.
411 @item mm-enable-external
412 @vindex mm-enable-external
413 Indicate whether external MIME handlers should be used.
415 If @code{t}, all defined external MIME handlers are used. If
416 @code{nil}, files are saved to disk (@code{mailcap-save-binary-file}).
417 If it is the symbol @code{ask}, you are prompted before the external
418 @acronym{MIME} handler is invoked.
420 When you launch an attachment through mailcap (@pxref{mailcap}) an
421 attempt is made to use a safe viewer with the safest options--this isn't
422 the case if you save it to disk and launch it in a different way
423 (command line or double-clicking). Anyhow, if you want to be sure not
424 to launch any external programs, set this variable to @code{nil} or
429 @node Files and Directories
430 @section Files and Directories
434 @item mm-default-directory
435 @vindex mm-default-directory
436 The default directory for saving attachments. If @code{nil} use
437 @code{default-directory}.
439 @item mm-tmp-directory
440 @vindex mm-tmp-directory
441 Directory for storing temporary files.
443 @item mm-file-name-rewrite-functions
444 @vindex mm-file-name-rewrite-functions
445 A list of functions used for rewriting file names of @acronym{MIME}
446 parts. Each function is applied successively to the file name.
447 Ready-made functions include
450 @item mm-file-name-delete-control
451 @findex mm-file-name-delete-control
452 Delete all control characters.
454 @item mm-file-name-delete-gotchas
455 @findex mm-file-name-delete-gotchas
456 Delete characters that could have unintended consequences when used
457 with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
458 @samp{-}, @samp{.} as the first character.
460 @item mm-file-name-delete-whitespace
461 @findex mm-file-name-delete-whitespace
462 Remove all whitespace.
464 @item mm-file-name-trim-whitespace
465 @findex mm-file-name-trim-whitespace
466 Remove leading and trailing whitespace.
468 @item mm-file-name-collapse-whitespace
469 @findex mm-file-name-collapse-whitespace
470 Collapse multiple whitespace characters.
472 @item mm-file-name-replace-whitespace
473 @findex mm-file-name-replace-whitespace
474 @vindex mm-file-name-replace-whitespace
475 Replace whitespace with underscores. Set the variable
476 @code{mm-file-name-replace-whitespace} to any other string if you do
477 not like underscores.
480 The standard Emacs functions @code{capitalize}, @code{downcase},
481 @code{upcase} and @code{upcase-initials} might also prove useful.
483 @item mm-path-name-rewrite-functions
484 @vindex mm-path-name-rewrite-functions
485 List of functions used for rewriting the full file names of @acronym{MIME}
486 parts. This is used when viewing parts externally, and is meant for
487 transforming the absolute name so that non-compliant programs can find
488 the file where it's saved.
495 Here's an example viewer for displaying @code{text/enriched} inline:
498 (defun mm-display-enriched-inline (handle)
501 (mm-insert-part handle)
502 (save-window-excursion
503 (enriched-decode (point-min) (point-max))
504 (setq text (buffer-string))))
505 (mm-insert-inline handle text)))
508 We see that the function takes a @acronym{MIME} handle as its parameter. It
509 then goes to a temporary buffer, inserts the text of the part, does some
510 work on the text, stores the result, goes back to the buffer it was
511 called from and inserts the result.
513 The two important helper functions here are @code{mm-insert-part} and
514 @code{mm-insert-inline}. The first function inserts the text of the
515 handle in the current buffer. It handles charset and/or content
516 transfer decoding. The second function just inserts whatever text you
517 tell it to insert, but it also sets things up so that the text can be
518 ``undisplayed'' in a convenient manner.
524 @cindex MIME Composing
526 @cindex MIME Meta Language
528 Creating a @acronym{MIME} message is boring and non-trivial. Therefore,
529 a library called @code{mml} has been defined that parses a language
530 called @acronym{MML} (@acronym{MIME} Meta Language) and generates
531 @acronym{MIME} messages.
533 @findex mml-generate-mime
534 The main interface function is @code{mml-generate-mime}. It will
535 examine the contents of the current (narrowed-to) buffer and return a
536 string containing the @acronym{MIME} message.
539 * Simple MML Example:: An example @acronym{MML} document.
540 * MML Definition:: All valid @acronym{MML} elements.
541 * Advanced MML Example:: Another example @acronym{MML} document.
542 * Encoding Customization:: Variables that affect encoding.
543 * Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
544 * Conversion:: Going from @acronym{MIME} to @acronym{MML} and vice versa.
545 * Flowed text:: Soft and hard newlines.
549 @node Simple MML Example
550 @section Simple MML Example
552 Here's a simple @samp{multipart/alternative}:
555 <#multipart type=alternative>
556 This is a plain text part.
557 <#part type=text/enriched>
558 <center>This is a centered enriched part</center>
562 After running this through @code{mml-generate-mime}, we get this:
565 Content-Type: multipart/alternative; boundary="=-=-="
571 This is a plain text part.
574 Content-Type: text/enriched
577 <center>This is a centered enriched part</center>
584 @section MML Definition
586 The @acronym{MML} language is very simple. It looks a bit like an SGML
587 application, but it's not.
589 The main concept of @acronym{MML} is the @dfn{part}. Each part can be of a
590 different type or use a different charset. The way to delineate a part
591 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
592 with the @samp{<#multipart ...>} tag. Parts are ended by the
593 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
594 @samp{<#part ...>} tags are also closed by the next open tag.
596 There's also the @samp{<#external ...>} tag. These introduce
597 @samp{external/message-body} parts.
599 Each tag can contain zero or more parameters on the form
600 @samp{parameter=value}. The values may be enclosed in quotation marks,
601 but that's not necessary unless the value contains white space. So
602 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
604 The following parameters have meaning in @acronym{MML}; parameters that have no
605 meaning are ignored. The @acronym{MML} parameter names are the same as the
606 @acronym{MIME} parameter names; the things in the parentheses say which
607 header it will be used in.
611 The @acronym{MIME} type of the part (@code{Content-Type}).
614 Use the contents of the file in the body of the part
615 (@code{Content-Disposition}).
618 The contents of the body of the part are to be encoded in the character
619 set specified (@code{Content-Type}). @xref{Charset Translation}.
622 Might be used to suggest a file name if the part is to be saved
623 to a file (@code{Content-Type}).
626 Valid values are @samp{inline} and @samp{attachment}
627 (@code{Content-Disposition}).
630 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
631 @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
635 A description of the part (@code{Content-Description}).
638 RFC822 date when the part was created (@code{Content-Disposition}).
640 @item modification-date
641 RFC822 date when the part was modified (@code{Content-Disposition}).
644 RFC822 date when the part was read (@code{Content-Disposition}).
647 Who to encrypt/sign the part to. This field is used to override any
648 auto-detection based on the To/CC headers.
651 Identity used to sign the part. This field is used to override the
655 The size (in octets) of the part (@code{Content-Disposition}).
658 What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
662 What technology to encrypt this @acronym{MML} part with (@code{smime},
663 @code{pgp} or @code{pgpmime})
667 Parameters for @samp{text/plain}:
671 Formatting parameter for the text, valid values include @samp{fixed}
672 (the default) and @samp{flowed}. Normally you do not specify this
673 manually, since it requires the textual body to be formatted in a
674 special way described in RFC 2646. @xref{Flowed text}.
677 Parameters for @samp{application/octet-stream}:
681 Type of the part; informal---meant for human readers
682 (@code{Content-Type}).
685 Parameters for @samp{message/external-body}:
689 A word indicating the supported access mechanism by which the file may
690 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
691 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
694 The RFC822 date after which the file may no longer be fetched.
695 (@code{Content-Type}.)
698 The size (in octets) of the file. (@code{Content-Type}.)
701 Valid values are @samp{read} and @samp{read-write}
702 (@code{Content-Type}).
706 Parameters for @samp{sign=smime}:
711 File containing key and certificate for signer.
715 Parameters for @samp{encrypt=smime}:
720 File containing certificate for recipient.
725 @node Advanced MML Example
726 @section Advanced MML Example
728 Here's a complex multipart message. It's a @samp{multipart/mixed} that
729 contains many parts, one of which is a @samp{multipart/alternative}.
732 <#multipart type=mixed>
733 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
734 <#multipart type=alternative>
735 This is a plain text part.
736 <#part type=text/enriched name=enriched.txt>
737 <center>This is a centered enriched part</center>
739 This is a new plain text part.
740 <#part disposition=attachment>
741 This plain text part is an attachment.
745 And this is the resulting @acronym{MIME} message:
748 Content-Type: multipart/mixed; boundary="=-=-="
756 Content-Type: image/jpeg;
758 Content-Disposition: inline;
760 Content-Transfer-Encoding: base64
762 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
763 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
764 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
765 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
766 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
767 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
768 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
769 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
770 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
771 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
772 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
773 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
774 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
775 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
776 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
777 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
778 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
781 Content-Type: multipart/alternative; boundary="==-=-="
787 This is a plain text part.
790 Content-Type: text/enriched;
794 <center>This is a centered enriched part</center>
800 This is a new plain text part.
803 Content-Disposition: attachment
806 This plain text part is an attachment.
811 @node Encoding Customization
812 @section Encoding Customization
816 @item mm-body-charset-encoding-alist
817 @vindex mm-body-charset-encoding-alist
818 Mapping from @acronym{MIME} charset to encoding to use. This variable is
819 usually used except, e.g., when other requirements force a specific
820 encoding (digitally signed messages require 7bit encodings). The
824 ((iso-2022-jp . 7bit)
825 (iso-2022-jp-2 . 7bit)
831 As an example, if you do not want to have ISO-8859-1 characters
832 quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
833 this variable. You can override this setting on a per-message basis
834 by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
836 @item mm-coding-system-priorities
837 @vindex mm-coding-system-priorities
838 Prioritize coding systems to use for outgoing messages. The default
839 is @code{nil}, which means to use the defaults in Emacs. It is a list of
840 coding system symbols (aliases of coding systems does not work, use
841 @kbd{M-x describe-coding-system} to make sure you are not specifying
842 an alias in this variable). For example, if you have configured Emacs
843 to prefer UTF-8, but wish that outgoing messages should be sent in
844 ISO-8859-1 if possible, you can set this variable to
845 @code{(iso-latin-1)}. You can override this setting on a per-message
846 basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
848 @item mm-content-transfer-encoding-defaults
849 @vindex mm-content-transfer-encoding-defaults
850 Mapping from @acronym{MIME} types to encoding to use. This variable is usually
851 used except, e.g., when other requirements force a safer encoding
852 (digitally signed messages require 7bit encoding). Besides the normal
853 @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
854 each case the most efficient of quoted-printable and base64 should be
855 used. You can override this setting on a per-message basis by using
856 the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
858 @item mm-use-ultra-safe-encoding
859 @vindex mm-use-ultra-safe-encoding
860 When this is non-@code{nil}, it means that textual parts are encoded as
861 quoted-printable if they contain lines longer than 76 characters or
862 starting with "From " in the body. Non-7bit encodings (8bit, binary)
863 are generally disallowed. This reduce the probability that a non-8bit
864 clean MTA or MDA changes the message. This should never be set
865 directly, but bound by other functions when necessary (e.g., when
866 encoding messages that are to be digitally signed).
870 @node Charset Translation
871 @section Charset Translation
874 During translation from @acronym{MML} to @acronym{MIME}, for each
875 @acronym{MIME} part which has been composed inside Emacs, an appropriate
876 charset has to be chosen.
878 @vindex mail-parse-charset
879 If you are running a non-@sc{mule} Emacs, this process is simple: If the
880 part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
881 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
882 variable directly, though. If you want to change the default charset,
883 please consult the documentation of the package which you use to process
884 @acronym{MIME} messages.
885 @xref{Various Message Variables, , Various Message Variables, message,
886 Message Manual}, for example.)
887 If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
893 @vindex mm-mime-mule-charset-alist
894 Things are slightly more complicated when running Emacs with @sc{mule}
895 support. In this case, a list of the @sc{mule} charsets used in the
896 part is obtained, and the @sc{mule} charsets are translated to @acronym{MIME}
897 charsets by consulting the variable @code{mm-mime-mule-charset-alist}.
898 If this results in a single @acronym{MIME} charset, this is used to encode
899 the part. But if the resulting list of @acronym{MIME} charsets contains more
900 than one element, two things can happen: If it is possible to encode the
901 part via UTF-8, this charset is used. (For this, Emacs must support
902 the @code{utf-8} coding system, and the part must consist entirely of
903 characters which have Unicode counterparts.) If UTF-8 is not available
904 for some reason, the part is split into several ones, so that each one
905 can be encoded with a single @acronym{MIME} charset. The part can only be
906 split at line boundaries, though---if more than one @acronym{MIME} charset is
907 required to encode a single line, it is not possible to encode the part.
909 When running Emacs with @sc{mule} support, the preferences for which
910 coding system to use is inherited from Emacs itself. This means that
911 if Emacs is set up to prefer UTF-8, it will be used when encoding
912 messages. You can modify this by altering the
913 @code{mm-coding-system-priorities} variable though (@pxref{Encoding
916 The charset to be used can be overridden by setting the @code{charset}
917 @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
919 The encoding of characters (quoted-printable, 8bit etc) is orthogonal
920 to the discussion here, and is controlled by the variables
921 @code{mm-body-charset-encoding-alist} and
922 @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
929 A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
930 with the @code{mime-to-mml} function. It works on the message in the
931 current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
932 boundaries. Non-textual parts do not have their contents in the buffer,
933 but instead have the contents in separate buffers that are referred to
934 from the @acronym{MML} tags.
937 An @acronym{MML} message can be converted back to @acronym{MIME} by the
938 @code{mml-to-mime} function.
940 These functions are in certain senses ``lossy''---you will not get back
941 an identical message if you run @code{mime-to-mml} and then
942 @code{mml-to-mime}. Not only will trivial things like the order of the
943 headers differ, but the contents of the headers may also be different.
944 For instance, the original message may use base64 encoding on text,
945 while @code{mml-to-mime} may decide to use quoted-printable encoding, and
948 In essence, however, these two functions should be the inverse of each
949 other. The resulting contents of the message should remain equivalent,
955 @cindex format=flowed
957 The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
958 variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
959 emacs, Emacs Manual}) when encoding a message, and the
960 ``format=flowed'' Content-Type parameter when decoding a message.
962 On encoding text, regardless of @code{use-hard-newlines}, lines
963 terminated by soft newline characters are filled together and wrapped
964 after the column decided by @code{fill-flowed-encode-column}.
965 Quotation marks (matching @samp{^>* ?}) are respected. The variable
966 controls how the text will look in a client that does not support
967 flowed text, the default is to wrap after 66 characters. If hard
968 newline characters are not present in the buffer, no flow encoding
971 On decoding flowed text, lines with soft newline characters are filled
972 together and wrapped after the column decided by
973 @code{fill-flowed-display-column}. The default is to wrap after
978 @findex mm-fill-flowed
979 If non-nil a format=flowed article will be displayed flowed.
983 @node Interface Functions
984 @chapter Interface Functions
985 @cindex interface functions
988 The @code{mail-parse} library is an abstraction over the actual
989 low-level libraries that are described in the next chapter.
991 Standards change, and so programs have to change to fit in the new
992 mold. For instance, RFC2045 describes a syntax for the
993 @code{Content-Type} header that only allows @acronym{ASCII} characters in the
994 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
995 for continuation headers and non-@acronym{ASCII} characters.
997 The traditional way to deal with this is just to update the library
998 functions to parse the new syntax. However, this is sometimes the wrong
999 thing to do. In some instances it may be vital to be able to understand
1000 both the old syntax as well as the new syntax, and if there is only one
1001 library, one must choose between the old version of the library and the
1002 new version of the library.
1004 The Emacs @acronym{MIME} library takes a different tack. It defines a
1005 series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
1006 and so on) that parses strictly according to the corresponding
1007 standard. However, normal programs would not use the functions
1008 provided by these libraries directly, but instead use the functions
1009 provided by the @code{mail-parse} library. The functions in this
1010 library are just aliases to the corresponding functions in the latest
1011 low-level libraries. Using this scheme, programs get a consistent
1012 interface they can use, and library developers are free to create
1013 write code that handles new standards.
1015 The following functions are defined by this library:
1018 @item mail-header-parse-content-type
1019 @findex mail-header-parse-content-type
1020 Parse a @code{Content-Type} header and return a list on the following
1025 (attribute1 . value1)
1026 (attribute2 . value2)
1033 (mail-header-parse-content-type
1034 "image/gif; name=\"b980912.gif\"")
1035 @result{} ("image/gif" (name . "b980912.gif"))
1038 @item mail-header-parse-content-disposition
1039 @findex mail-header-parse-content-disposition
1040 Parse a @code{Content-Disposition} header and return a list on the same
1041 format as the function above.
1043 @item mail-content-type-get
1044 @findex mail-content-type-get
1045 Takes two parameters---a list on the format above, and an attribute.
1046 Returns the value of the attribute.
1049 (mail-content-type-get
1050 '("image/gif" (name . "b980912.gif")) 'name)
1051 @result{} "b980912.gif"
1054 @item mail-header-encode-parameter
1055 @findex mail-header-encode-parameter
1056 Takes a parameter string and returns an encoded version of the string.
1057 This is used for parameters in headers like @code{Content-Type} and
1058 @code{Content-Disposition}.
1060 @item mail-header-remove-comments
1061 @findex mail-header-remove-comments
1062 Return a comment-free version of a header.
1065 (mail-header-remove-comments
1066 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1067 @result{} "Gnus/5.070027 "
1070 @item mail-header-remove-whitespace
1071 @findex mail-header-remove-whitespace
1072 Remove linear white space from a header. Space inside quoted strings
1073 and comments is preserved.
1076 (mail-header-remove-whitespace
1077 "image/gif; name=\"Name with spaces\"")
1078 @result{} "image/gif;name=\"Name with spaces\""
1081 @item mail-header-get-comment
1082 @findex mail-header-get-comment
1083 Return the last comment in a header.
1086 (mail-header-get-comment
1087 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1088 @result{} "Finnish Landrace"
1091 @item mail-header-parse-address
1092 @findex mail-header-parse-address
1093 Parse an address and return a list containing the mailbox and the
1097 (mail-header-parse-address
1098 "Hrvoje Niksic <hniksic@@srce.hr>")
1099 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
1102 @item mail-header-parse-addresses
1103 @findex mail-header-parse-addresses
1104 Parse a string with list of addresses and return a list of elements like
1105 the one described above.
1108 (mail-header-parse-addresses
1109 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
1110 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
1111 ("sb@@metis.no" . "Steinar Bang"))
1114 @item mail-header-parse-date
1115 @findex mail-header-parse-date
1116 Parse a date string and return an Emacs time structure.
1118 @item mail-narrow-to-head
1119 @findex mail-narrow-to-head
1120 Narrow the buffer to the header section of the buffer. Point is placed
1121 at the beginning of the narrowed buffer.
1123 @item mail-header-narrow-to-field
1124 @findex mail-header-narrow-to-field
1125 Narrow the buffer to the header under point. Understands continuation
1128 @item mail-header-fold-field
1129 @findex mail-header-fold-field
1130 Fold the header under point.
1132 @item mail-header-unfold-field
1133 @findex mail-header-unfold-field
1134 Unfold the header under point.
1136 @item mail-header-field-value
1137 @findex mail-header-field-value
1138 Return the value of the field under point.
1140 @item mail-encode-encoded-word-region
1141 @findex mail-encode-encoded-word-region
1142 Encode the non-@acronym{ASCII} words in the region. For instance,
1143 @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
1145 @item mail-encode-encoded-word-buffer
1146 @findex mail-encode-encoded-word-buffer
1147 Encode the non-@acronym{ASCII} words in the current buffer. This function is
1148 meant to be called narrowed to the headers of a message.
1150 @item mail-encode-encoded-word-string
1151 @findex mail-encode-encoded-word-string
1152 Encode the words that need encoding in a string, and return the result.
1155 (mail-encode-encoded-word-string
1156 "This is naïve, baby")
1157 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
1160 @item mail-decode-encoded-word-region
1161 @findex mail-decode-encoded-word-region
1162 Decode the encoded words in the region.
1164 @item mail-decode-encoded-word-string
1165 @findex mail-decode-encoded-word-string
1166 Decode the encoded words in the string and return the result.
1169 (mail-decode-encoded-word-string
1170 "This is =?iso-8859-1?q?na=EFve,?= baby")
1171 @result{} "This is naïve, baby"
1176 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
1177 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
1178 in the subsequent sections.
1182 @node Basic Functions
1183 @chapter Basic Functions
1185 This chapter describes the basic, ground-level functions for parsing and
1186 handling. Covered here is parsing @code{From} lines, removing comments
1187 from header lines, decoding encoded words, parsing date headers and so
1188 on. High-level functionality is dealt with in the next chapter
1189 (@pxref{Decoding and Viewing}).
1192 * rfc2045:: Encoding @code{Content-Type} headers.
1193 * rfc2231:: Parsing @code{Content-Type} headers.
1194 * ietf-drums:: Handling mail headers defined by RFC822bis.
1195 * rfc2047:: En/decoding encoded words in headers.
1196 * time-date:: Functions for parsing dates and manipulating time.
1197 * qp:: Quoted-Printable en/decoding.
1198 * base64:: Base64 en/decoding.
1199 * binhex:: Binhex decoding.
1200 * uudecode:: Uuencode decoding.
1201 * yenc:: Yenc decoding.
1202 * rfc1843:: Decoding HZ-encoded text.
1203 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
1210 RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
1211 imagine that there would be a lot to implement. But there isn't, since
1212 most of the implementation details are delegated to the subsequent
1215 So @file{rfc2045.el} has only a single function:
1218 @item rfc2045-encode-string
1219 @findex rfc2045-encode-string
1220 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
1221 @var{value} will be quoted if there are non-safe characters in it.
1228 RFC2231 defines a syntax for the @code{Content-Type} and
1229 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
1230 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
1233 In short, these headers look something like this:
1236 Content-Type: application/x-stuff;
1237 title*0*=us-ascii'en'This%20is%20even%20more%20;
1238 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1242 They usually aren't this bad, though.
1244 The following functions are defined by this library:
1247 @item rfc2231-parse-string
1248 @findex rfc2231-parse-string
1249 Parse a @code{Content-Type} header and return a list describing its
1253 (rfc2231-parse-string
1254 "application/x-stuff;
1255 title*0*=us-ascii'en'This%20is%20even%20more%20;
1256 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1257 title*2=\"isn't it!\"")
1258 @result{} ("application/x-stuff"
1259 (title . "This is even more ***fun*** isn't it!"))
1262 @item rfc2231-get-value
1263 @findex rfc2231-get-value
1264 Takes one of the lists on the format above and returns
1265 the value of the specified attribute.
1267 @item rfc2231-encode-string
1268 @findex rfc2231-encode-string
1269 Encode a parameter in headers likes @code{Content-Type} and
1270 @code{Content-Disposition}.
1278 @dfn{drums} is an IETF working group that is working on the replacement
1281 The functions provided by this library include:
1284 @item ietf-drums-remove-comments
1285 @findex ietf-drums-remove-comments
1286 Remove the comments from the argument and return the results.
1288 @item ietf-drums-remove-whitespace
1289 @findex ietf-drums-remove-whitespace
1290 Remove linear white space from the string and return the results.
1291 Spaces inside quoted strings and comments are left untouched.
1293 @item ietf-drums-get-comment
1294 @findex ietf-drums-get-comment
1295 Return the last most comment from the string.
1297 @item ietf-drums-parse-address
1298 @findex ietf-drums-parse-address
1299 Parse an address string and return a list that contains the mailbox and
1300 the plain text name.
1302 @item ietf-drums-parse-addresses
1303 @findex ietf-drums-parse-addresses
1304 Parse a string that contains any number of comma-separated addresses and
1305 return a list that contains mailbox/plain text pairs.
1307 @item ietf-drums-parse-date
1308 @findex ietf-drums-parse-date
1309 Parse a date string and return an Emacs time structure.
1311 @item ietf-drums-narrow-to-header
1312 @findex ietf-drums-narrow-to-header
1313 Narrow the buffer to the header section of the current buffer.
1321 RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
1322 non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
1323 complicated, so a number of variables are necessary to tweak what this
1326 The following variables are tweakable:
1329 @item rfc2047-default-charset
1330 @vindex rfc2047-default-charset
1331 Characters in this charset should not be decoded by this library.
1332 This defaults to @code{iso-8859-1}.
1334 @item rfc2047-header-encoding-alist
1335 @vindex rfc2047-header-encoding-alist
1336 This is an alist of header / encoding-type pairs. Its main purpose is
1337 to prevent encoding of certain headers.
1339 The keys can either be header regexps, or @code{t}.
1341 The values can be either @code{nil}, in which case the header(s) in
1342 question won't be encoded, or @code{mime}, which means that they will be
1345 @item rfc2047-charset-encoding-alist
1346 @vindex rfc2047-charset-encoding-alist
1347 RFC2047 specifies two forms of encoding---@code{Q} (a
1348 Quoted-Printable-like encoding) and @code{B} (base64). This alist
1349 specifies which charset should use which encoding.
1351 @item rfc2047-encoding-function-alist
1352 @vindex rfc2047-encoding-function-alist
1353 This is an alist of encoding / function pairs. The encodings are
1354 @code{Q}, @code{B} and @code{nil}.
1356 @item rfc2047-q-encoding-alist
1357 @vindex rfc2047-q-encoding-alist
1358 The @code{Q} encoding isn't quite the same for all headers. Some
1359 headers allow a narrower range of characters, and that is what this
1360 variable is for. It's an alist of header regexps / allowable character
1363 @item rfc2047-encoded-word-regexp
1364 @vindex rfc2047-encoded-word-regexp
1365 When decoding words, this library looks for matches to this regexp.
1369 Those were the variables, and these are this functions:
1372 @item rfc2047-narrow-to-field
1373 @findex rfc2047-narrow-to-field
1374 Narrow the buffer to the header on the current line.
1376 @item rfc2047-encode-message-header
1377 @findex rfc2047-encode-message-header
1378 Should be called narrowed to the header of a message. Encodes according
1379 to @code{rfc2047-header-encoding-alist}.
1381 @item rfc2047-encode-region
1382 @findex rfc2047-encode-region
1383 Encodes all encodable words in the region specified.
1385 @item rfc2047-encode-string
1386 @findex rfc2047-encode-string
1387 Encode a string and return the results.
1389 @item rfc2047-decode-region
1390 @findex rfc2047-decode-region
1391 Decode the encoded words in the region.
1393 @item rfc2047-decode-string
1394 @findex rfc2047-decode-string
1395 Decode a string and return the results.
1403 While not really a part of the @acronym{MIME} library, it is convenient to
1404 document this library here. It deals with parsing @code{Date} headers
1405 and manipulating time. (Not by using tesseracts, though, I'm sorry to
1408 These functions convert between five formats: A date string, an Emacs
1409 time structure, a decoded time list, a second number, and a day number.
1411 Here's a bunch of time/date/second/day examples:
1414 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
1415 @result{} (54 21 12 12 9 1998 6 nil 7200)
1417 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
1418 @result{} (13818 19266)
1420 (time-to-seconds '(13818 19266))
1421 @result{} 905595714.0
1423 (seconds-to-time 905595714.0)
1424 @result{} (13818 19266 0)
1426 (time-to-days '(13818 19266))
1429 (days-to-time 729644)
1430 @result{} (961933 65536)
1432 (time-since '(13818 19266))
1435 (time-less-p '(13818 19266) '(13818 19145))
1438 (subtract-time '(13818 19266) '(13818 19145))
1441 (days-between "Sat Sep 12 12:21:54 1998 +0200"
1442 "Sat Sep 07 12:21:54 1998 +0200")
1445 (date-leap-year-p 2000)
1448 (time-to-day-in-year '(13818 19266))
1451 (time-to-number-of-days
1453 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
1454 @result{} 4.146122685185185
1457 And finally, we have @code{safe-date-to-time}, which does the same as
1458 @code{date-to-time}, but returns a zero time if the date is
1459 syntactically malformed.
1461 The five data representations used are the following:
1465 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
1466 12:21:54 1998 +0200"}.
1469 An internal Emacs time. For instance: @code{(13818 26466)}.
1472 A floating point representation of the internal Emacs time. For
1473 instance: @code{905595714.0}.
1476 An integer number representing the number of days since 00000101. For
1477 instance: @code{729644}.
1480 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
1484 All the examples above represent the same moment.
1486 These are the functions available:
1490 Take a date and return a time.
1492 @item time-to-seconds
1493 Take a time and return seconds.
1495 @item seconds-to-time
1496 Take seconds and return a time.
1499 Take a time and return days.
1502 Take days and return a time.
1505 Take a date and return days.
1507 @item time-to-number-of-days
1508 Take a time and return the number of days that represents.
1510 @item safe-date-to-time
1511 Take a date and return a time. If the date is not syntactically valid,
1512 return a ``zero'' date.
1515 Take two times and say whether the first time is less (i. e., earlier)
1516 than the second time.
1519 Take a time and return a time saying how long it was since that time.
1522 Take two times and subtract the second from the first. I. e., return
1523 the time between the two times.
1526 Take two days and return the number of days between those two days.
1528 @item date-leap-year-p
1529 Take a year number and say whether it's a leap year.
1531 @item time-to-day-in-year
1532 Take a time and return the day number within the year that the time is
1541 This library deals with decoding and encoding Quoted-Printable text.
1543 Very briefly explained, qp encoding means translating all 8-bit
1544 characters (and lots of control characters) into things that look like
1545 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
1548 The following functions are defined by the library:
1551 @item quoted-printable-decode-region
1552 @findex quoted-printable-decode-region
1553 QP-decode all the encoded text in the specified region.
1555 @item quoted-printable-decode-string
1556 @findex quoted-printable-decode-string
1557 Decode the QP-encoded text in a string and return the results.
1559 @item quoted-printable-encode-region
1560 @findex quoted-printable-encode-region
1561 QP-encode all the encodable characters in the specified region. The third
1562 optional parameter @var{fold} specifies whether to fold long lines.
1563 (Long here means 72.)
1565 @item quoted-printable-encode-string
1566 @findex quoted-printable-encode-string
1567 QP-encode all the encodable characters in a string and return the
1577 Base64 is an encoding that encodes three bytes into four characters,
1578 thereby increasing the size by about 33%. The alphabet used for
1579 encoding is very resistant to mangling during transit.
1581 The following functions are defined by this library:
1584 @item base64-encode-region
1585 @findex base64-encode-region
1586 base64 encode the selected region. Return the length of the encoded
1587 text. Optional third argument @var{no-line-break} means do not break
1588 long lines into shorter lines.
1590 @item base64-encode-string
1591 @findex base64-encode-string
1592 base64 encode a string and return the result.
1594 @item base64-decode-region
1595 @findex base64-decode-region
1596 base64 decode the selected region. Return the length of the decoded
1597 text. If the region can't be decoded, return @code{nil} and don't
1600 @item base64-decode-string
1601 @findex base64-decode-string
1602 base64 decode a string and return the result. If the string can't be
1603 decoded, @code{nil} is returned.
1614 @code{binhex} is an encoding that originated in Macintosh environments.
1615 The following function is supplied to deal with these:
1618 @item binhex-decode-region
1619 @findex binhex-decode-region
1620 Decode the encoded text in the region. If given a third parameter, only
1621 decode the @code{binhex} header and return the filename.
1630 @code{uuencode} is probably still the most popular encoding of binaries
1631 used on Usenet, although @code{base64} rules the mail world.
1633 The following function is supplied by this package:
1636 @item uudecode-decode-region
1637 @findex uudecode-decode-region
1638 Decode the text in the region.
1646 @code{yenc} is used for encoding binaries on Usenet. The following
1647 function is supplied by this package:
1650 @item yenc-decode-region
1651 @findex yenc-decode-region
1652 Decode the encoded text in the region.
1663 RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
1664 essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
1667 This sentence is in @acronym{ASCII}.
1668 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
1671 Simple enough, and widely used in China.
1673 The following functions are available to handle this encoding:
1676 @item rfc1843-decode-region
1677 Decode HZ-encoded text in the region.
1679 @item rfc1843-decode-string
1680 Decode a HZ-encoded string and return the result.
1688 The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
1689 handlers and describes how elements are supposed to be displayed.
1690 Here's an example file:
1694 audio/wav; wavplayer %s
1695 application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
1698 This says that all image files should be displayed with @code{gimp},
1699 that WAVE audio files should be played by @code{wavplayer}, and that
1700 MS-WORD files should be inlined by @code{catdoc}.
1702 The @code{mailcap} library parses this file, and provides functions for
1706 @item mailcap-mime-data
1707 @vindex mailcap-mime-data
1708 This variable is an alist of alists containing backup viewing rules.
1712 Interface functions:
1715 @item mailcap-parse-mailcaps
1716 @findex mailcap-parse-mailcaps
1717 Parse the @file{~/.mailcap} file.
1719 @item mailcap-mime-info
1720 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
1730 The Emacs @acronym{MIME} library implements handling of various elements
1731 according to a (somewhat) large number of RFCs, drafts and standards
1732 documents. This chapter lists the relevant ones. They can all be
1733 fetched from @uref{http://quimby.gnus.org/notes/}.
1738 Standard for the Format of ARPA Internet Text Messages.
1741 Standard for Interchange of USENET Messages
1744 Format of Internet Message Bodies
1750 Message Header Extensions for Non-@acronym{ASCII} Text
1753 Registration Procedures
1756 Conformance Criteria and Examples
1759 @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
1760 Languages, and Continuations
1763 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1764 @acronym{ASCII} characters
1766 @item draft-ietf-drums-msg-fmt-05.txt
1767 Draft for the successor of RFC822
1770 The @acronym{MIME} Multipart/Related Content-type
1773 The Multipart/Report Content Type for the Reporting of Mail System
1774 Administrative Messages
1777 Communicating Presentation Information in Internet Messages: The
1778 Content-Disposition Header Field
1781 Documentation of the text/plain format parameter for flowed text.
1797 @c coding: iso-8859-1