3 @setfilename 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
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}.
180 @cindex verbatim-marks
181 Slrn-style verbatim marks.
185 LaTeX documents. It only works in groups matching
186 @code{mm-uu-tex-groups-regexp}.
190 @cindex text/x-gnus-verbatim
191 @c Is @vindex suitable for a face?
192 @vindex mm-uu-extract
193 Some inlined non-@acronym{MIME} attachments are displayed using the face
194 @code{mm-uu-extract}. By default, no @acronym{MIME} button for these
195 parts is displayed. You can force displaying a button using @kbd{K b}
196 (@code{gnus-summary-display-buttonized}) or add @code{text/x-gnus-verbatim} to
197 @code{gnus-buttonized-mime-types}, @xref{MIME Commands, ,MIME
198 Commands, gnus, Gnus Manual}.
203 A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
206 The following macros can be used to access elements in a handle:
209 @item mm-handle-buffer
210 @findex mm-handle-buffer
211 Return the buffer that holds the contents of the undecoded @acronym{MIME}
215 @findex mm-handle-type
216 Return the parsed @code{Content-Type} of the part.
218 @item mm-handle-encoding
219 @findex mm-handle-encoding
220 Return the @code{Content-Transfer-Encoding} of the part.
222 @item mm-handle-undisplayer
223 @findex mm-handle-undisplayer
224 Return the object that can be used to remove the displayed part (if it
227 @item mm-handle-set-undisplayer
228 @findex mm-handle-set-undisplayer
229 Set the undisplayer object.
231 @item mm-handle-disposition
232 @findex mm-handle-disposition
233 Return the parsed @code{Content-Disposition} of the part.
235 @item mm-get-content-id
236 Returns the handle(s) referred to by @code{Content-ID}.
244 Functions for displaying, removing and saving.
247 @item mm-display-part
248 @findex mm-display-part
252 @findex mm-remove-part
253 Remove the part (if it has been displayed).
256 @findex mm-inlinable-p
257 Say whether a @acronym{MIME} type can be displayed inline.
259 @item mm-automatic-display-p
260 @findex mm-automatic-display-p
261 Say whether a @acronym{MIME} type should be displayed automatically.
263 @item mm-destroy-part
264 @findex mm-destroy-part
265 Free all resources occupied by a part.
269 Offer to save the part in a file.
273 Offer to pipe the part to some process.
275 @item mm-interactively-view-part
276 @findex mm-interactively-view-part
277 Prompt for a mailcap method to use to view the part.
282 @node Display Customization
283 @section Display Customization
287 @item mm-inline-media-tests
288 @vindex mm-inline-media-tests
289 This is an alist where the key is a @acronym{MIME} type, the second element
290 is a function to display the part @dfn{inline} (i.e., inside Emacs), and
291 the third element is a form to be @code{eval}ed to say whether the part
292 can be displayed inline.
294 This variable specifies whether a part @emph{can} be displayed inline,
295 and, if so, how to do it. It does not say whether parts are
296 @emph{actually} displayed inline.
298 @item mm-inlined-types
299 @vindex mm-inlined-types
300 This, on the other hand, says what types are to be displayed inline, if
301 they satisfy the conditions set by the variable above. It's a list of
302 @acronym{MIME} media types.
304 @item mm-automatic-display
305 @vindex mm-automatic-display
306 This is a list of types that are to be displayed ``automatically'', but
307 only if the above variable allows it. That is, only inlinable parts can
308 be displayed automatically.
310 @item mm-automatic-external-display
311 @vindex mm-automatic-external-display
312 This is a list of types that will be displayed automatically in an
315 @item mm-keep-viewer-alive-types
316 @vindex mm-keep-viewer-alive-types
317 This is a list of media types for which the external viewer will not
318 be killed when selecting a different article.
320 @item mm-attachment-override-types
321 @vindex mm-attachment-override-types
322 Some @acronym{MIME} agents create parts that have a content-disposition of
323 @samp{attachment}. This variable allows overriding that disposition and
324 displaying the part inline. (Note that the disposition is only
325 overridden if we are able to, and want to, display the part inline.)
327 @item mm-discouraged-alternatives
328 @vindex mm-discouraged-alternatives
329 List of @acronym{MIME} types that are discouraged when viewing
330 @samp{multipart/alternative}. Viewing agents are supposed to view the
331 last possible part of a message, as that is supposed to be the richest.
332 However, users may prefer other types instead, and this list says what
333 types are most unwanted. If, for instance, @samp{text/html} parts are
334 very unwanted, and @samp{text/richtext} parts are somewhat unwanted,
335 you could say something like:
338 (setq mm-discouraged-alternatives
339 '("text/html" "text/richtext")
341 (remove "text/html" mm-automatic-display))
344 @item mm-inline-large-images
345 @vindex mm-inline-large-images
346 When displaying inline images that are larger than the window, Emacs
347 does not enable scrolling, which means that you cannot see the whole
348 image. To prevent this, the library tries to determine the image size
349 before displaying it inline, and if it doesn't fit the window, the
350 library will display it externally (e.g. with @samp{ImageMagick} or
351 @samp{xv}). Setting this variable to @code{t} disables this check and
352 makes the library display all inline images as inline, regardless of
355 @item mm-inline-override-types
356 @vindex mm-inline-override-types
357 @code{mm-inlined-types} may include regular expressions, for example to
358 specify that all @samp{text/.*} parts be displayed inline. If a user
359 prefers to have a type that matches such a regular expression be treated
360 as an attachment, that can be accomplished by setting this variable to a
361 list containing that type. For example assuming @code{mm-inlined-types}
362 includes @samp{text/.*}, then including @samp{text/html} in this
363 variable will cause @samp{text/html} parts to be treated as attachments.
365 @item mm-text-html-renderer
366 @vindex mm-text-html-renderer
367 This selects the function used to render @acronym{HTML}. The predefined
368 renderers are selected by the symbols @code{w3},
369 @code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
370 information about emacs-w3m}, @code{links}, @code{lynx},
371 @code{w3m-standalone} or @code{html2text}. If @code{nil} use an
372 external viewer. You can also specify a function, which will be
373 called with a @acronym{MIME} handle as the argument.
375 @item mm-inline-text-html-with-images
376 @vindex mm-inline-text-html-with-images
377 Some @acronym{HTML} mails might have the trick of spammers using
378 @samp{<img>} tags. It is likely to be intended to verify whether you
379 have read the mail. You can prevent your personal informations from
380 leaking by setting this option to @code{nil} (which is the default).
381 It is currently ignored by Emacs/w3. For emacs-w3m, you may use the
382 command @kbd{t} on the image anchor to show an image even if it is
383 @code{nil}.@footnote{The command @kbd{T} will load all images. If you
384 have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
387 @item mm-w3m-safe-url-regexp
388 @vindex mm-w3m-safe-url-regexp
389 A regular expression that matches safe URL names, i.e. URLs that are
390 unlikely to leak personal information when rendering @acronym{HTML}
391 email (the default value is @samp{\\`cid:}). If @code{nil} consider
394 @item mm-inline-text-html-with-w3m-keymap
395 @vindex mm-inline-text-html-with-w3m-keymap
396 You can use emacs-w3m command keys in the inlined text/html part by
397 setting this option to non-@code{nil}. The default value is @code{t}.
399 @item mm-external-terminal-program
400 @vindex mm-external-terminal-program
401 The program used to start an external terminal.
403 @item mm-enable-external
404 @vindex mm-enable-external
405 Indicate whether external @acronym{MIME} handlers should be used.
407 If @code{t}, all defined external @acronym{MIME} handlers are used. If
408 @code{nil}, files are saved to disk (@code{mailcap-save-binary-file}).
409 If it is the symbol @code{ask}, you are prompted before the external
410 @acronym{MIME} handler is invoked.
412 When you launch an attachment through mailcap (@pxref{mailcap}) an
413 attempt is made to use a safe viewer with the safest options---this isn't
414 the case if you save it to disk and launch it in a different way
415 (command line or double-clicking). Anyhow, if you want to be sure not
416 to launch any external programs, set this variable to @code{nil} or
421 @node Files and Directories
422 @section Files and Directories
426 @item mm-default-directory
427 @vindex mm-default-directory
428 The default directory for saving attachments. If @code{nil} use
429 @code{default-directory}.
431 @item mm-tmp-directory
432 @vindex mm-tmp-directory
433 Directory for storing temporary files.
435 @item mm-file-name-rewrite-functions
436 @vindex mm-file-name-rewrite-functions
437 A list of functions used for rewriting file names of @acronym{MIME}
438 parts. Each function is applied successively to the file name.
439 Ready-made functions include
442 @item mm-file-name-delete-control
443 @findex mm-file-name-delete-control
444 Delete all control characters.
446 @item mm-file-name-delete-gotchas
447 @findex mm-file-name-delete-gotchas
448 Delete characters that could have unintended consequences when used
449 with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
450 @samp{-}, @samp{.} as the first character.
452 @item mm-file-name-delete-whitespace
453 @findex mm-file-name-delete-whitespace
454 Remove all whitespace.
456 @item mm-file-name-trim-whitespace
457 @findex mm-file-name-trim-whitespace
458 Remove leading and trailing whitespace.
460 @item mm-file-name-collapse-whitespace
461 @findex mm-file-name-collapse-whitespace
462 Collapse multiple whitespace characters.
464 @item mm-file-name-replace-whitespace
465 @findex mm-file-name-replace-whitespace
466 @vindex mm-file-name-replace-whitespace
467 Replace whitespace with underscores. Set the variable
468 @code{mm-file-name-replace-whitespace} to any other string if you do
469 not like underscores.
472 The standard Emacs functions @code{capitalize}, @code{downcase},
473 @code{upcase} and @code{upcase-initials} might also prove useful.
475 @item mm-path-name-rewrite-functions
476 @vindex mm-path-name-rewrite-functions
477 List of functions used for rewriting the full file names of @acronym{MIME}
478 parts. This is used when viewing parts externally, and is meant for
479 transforming the absolute name so that non-compliant programs can find
480 the file where it's saved.
487 Here's an example viewer for displaying @code{text/enriched} inline:
490 (defun mm-display-enriched-inline (handle)
493 (mm-insert-part handle)
494 (save-window-excursion
495 (enriched-decode (point-min) (point-max))
496 (setq text (buffer-string))))
497 (mm-insert-inline handle text)))
500 We see that the function takes a @acronym{MIME} handle as its parameter. It
501 then goes to a temporary buffer, inserts the text of the part, does some
502 work on the text, stores the result, goes back to the buffer it was
503 called from and inserts the result.
505 The two important helper functions here are @code{mm-insert-part} and
506 @code{mm-insert-inline}. The first function inserts the text of the
507 handle in the current buffer. It handles charset and/or content
508 transfer decoding. The second function just inserts whatever text you
509 tell it to insert, but it also sets things up so that the text can be
510 ``undisplayed'' in a convenient manner.
516 @cindex MIME Composing
518 @cindex MIME Meta Language
520 Creating a @acronym{MIME} message is boring and non-trivial. Therefore,
521 a library called @code{mml} has been defined that parses a language
522 called @acronym{MML} (@acronym{MIME} Meta Language) and generates
523 @acronym{MIME} messages.
525 @findex mml-generate-mime
526 The main interface function is @code{mml-generate-mime}. It will
527 examine the contents of the current (narrowed-to) buffer and return a
528 string containing the @acronym{MIME} message.
531 * Simple MML Example:: An example @acronym{MML} document.
532 * MML Definition:: All valid @acronym{MML} elements.
533 * Advanced MML Example:: Another example @acronym{MML} document.
534 * Encoding Customization:: Variables that affect encoding.
535 * Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
536 * Conversion:: Going from @acronym{MIME} to @acronym{MML} and vice versa.
537 * Flowed text:: Soft and hard newlines.
541 @node Simple MML Example
542 @section Simple MML Example
544 Here's a simple @samp{multipart/alternative}:
547 <#multipart type=alternative>
548 This is a plain text part.
549 <#part type=text/enriched>
550 <center>This is a centered enriched part</center>
554 After running this through @code{mml-generate-mime}, we get this:
557 Content-Type: multipart/alternative; boundary="=-=-="
563 This is a plain text part.
566 Content-Type: text/enriched
569 <center>This is a centered enriched part</center>
576 @section MML Definition
578 The @acronym{MML} language is very simple. It looks a bit like an SGML
579 application, but it's not.
581 The main concept of @acronym{MML} is the @dfn{part}. Each part can be of a
582 different type or use a different charset. The way to delineate a part
583 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
584 with the @samp{<#multipart ...>} tag. Parts are ended by the
585 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
586 @samp{<#part ...>} tags are also closed by the next open tag.
588 There's also the @samp{<#external ...>} tag. These introduce
589 @samp{external/message-body} parts.
591 Each tag can contain zero or more parameters on the form
592 @samp{parameter=value}. The values may be enclosed in quotation marks,
593 but that's not necessary unless the value contains white space. So
594 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
596 The following parameters have meaning in @acronym{MML}; parameters that have no
597 meaning are ignored. The @acronym{MML} parameter names are the same as the
598 @acronym{MIME} parameter names; the things in the parentheses say which
599 header it will be used in.
603 The @acronym{MIME} type of the part (@code{Content-Type}).
606 Use the contents of the file in the body of the part
607 (@code{Content-Disposition}).
610 The contents of the body of the part are to be encoded in the character
611 set specified (@code{Content-Type}). @xref{Charset Translation}.
614 Might be used to suggest a file name if the part is to be saved
615 to a file (@code{Content-Type}).
618 Valid values are @samp{inline} and @samp{attachment}
619 (@code{Content-Disposition}).
622 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
623 @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
627 A description of the part (@code{Content-Description}).
630 RFC822 date when the part was created (@code{Content-Disposition}).
632 @item modification-date
633 RFC822 date when the part was modified (@code{Content-Disposition}).
636 RFC822 date when the part was read (@code{Content-Disposition}).
639 Who to encrypt/sign the part to. This field is used to override any
640 auto-detection based on the To/CC headers.
643 Identity used to sign the part. This field is used to override the
647 The size (in octets) of the part (@code{Content-Disposition}).
650 What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
654 What technology to encrypt this @acronym{MML} part with (@code{smime},
655 @code{pgp} or @code{pgpmime})
659 Parameters for @samp{text/plain}:
663 Formatting parameter for the text, valid values include @samp{fixed}
664 (the default) and @samp{flowed}. Normally you do not specify this
665 manually, since it requires the textual body to be formatted in a
666 special way described in RFC 2646. @xref{Flowed text}.
669 Parameters for @samp{application/octet-stream}:
673 Type of the part; informal---meant for human readers
674 (@code{Content-Type}).
677 Parameters for @samp{message/external-body}:
681 A word indicating the supported access mechanism by which the file may
682 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
683 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
686 The RFC822 date after which the file may no longer be fetched.
687 (@code{Content-Type}.)
690 The size (in octets) of the file. (@code{Content-Type}.)
693 Valid values are @samp{read} and @samp{read-write}
694 (@code{Content-Type}).
698 Parameters for @samp{sign=smime}:
703 File containing key and certificate for signer.
707 Parameters for @samp{encrypt=smime}:
712 File containing certificate for recipient.
717 @node Advanced MML Example
718 @section Advanced MML Example
720 Here's a complex multipart message. It's a @samp{multipart/mixed} that
721 contains many parts, one of which is a @samp{multipart/alternative}.
724 <#multipart type=mixed>
725 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
726 <#multipart type=alternative>
727 This is a plain text part.
728 <#part type=text/enriched name=enriched.txt>
729 <center>This is a centered enriched part</center>
731 This is a new plain text part.
732 <#part disposition=attachment>
733 This plain text part is an attachment.
737 And this is the resulting @acronym{MIME} message:
740 Content-Type: multipart/mixed; boundary="=-=-="
748 Content-Type: image/jpeg;
750 Content-Disposition: inline;
752 Content-Transfer-Encoding: base64
754 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
755 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
756 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
757 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
758 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
759 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
760 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
761 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
762 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
763 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
764 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
765 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
766 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
767 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
768 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
769 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
770 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
773 Content-Type: multipart/alternative; boundary="==-=-="
779 This is a plain text part.
782 Content-Type: text/enriched;
786 <center>This is a centered enriched part</center>
792 This is a new plain text part.
795 Content-Disposition: attachment
798 This plain text part is an attachment.
803 @node Encoding Customization
804 @section Encoding Customization
808 @item mm-body-charset-encoding-alist
809 @vindex mm-body-charset-encoding-alist
810 Mapping from @acronym{MIME} charset to encoding to use. This variable is
811 usually used except, e.g., when other requirements force a specific
812 encoding (digitally signed messages require 7bit encodings). The
816 ((iso-2022-jp . 7bit)
817 (iso-2022-jp-2 . 7bit)
823 As an example, if you do not want to have ISO-8859-1 characters
824 quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
825 this variable. You can override this setting on a per-message basis
826 by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
828 @item mm-coding-system-priorities
829 @vindex mm-coding-system-priorities
830 Prioritize coding systems to use for outgoing messages. The default
831 is @code{nil}, which means to use the defaults in Emacs, but is
832 @code{(iso-8859-1 iso-2022-jp iso-2022-jp-2 shift_jis utf-8)} when
833 running Emacs in the Japanese language environment. It is a list of
834 coding system symbols (aliases of coding systems are also allowed, use
835 @kbd{M-x describe-coding-system} to make sure you are specifying correct
836 coding system names). For example, if you have configured Emacs
837 to prefer UTF-8, but wish that outgoing messages should be sent in
838 ISO-8859-1 if possible, you can set this variable to
839 @code{(iso-8859-1)}. You can override this setting on a per-message
840 basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
842 @item mm-content-transfer-encoding-defaults
843 @vindex mm-content-transfer-encoding-defaults
844 Mapping from @acronym{MIME} types to encoding to use. This variable is usually
845 used except, e.g., when other requirements force a safer encoding
846 (digitally signed messages require 7bit encoding). Besides the normal
847 @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
848 each case the most efficient of quoted-printable and base64 should be
851 @code{qp-or-base64} has another effect. It will fold long lines so that
852 MIME parts may not be broken by MTA. So do @code{quoted-printable} and
855 Note that it affects body encoding only when a part is a raw forwarded
856 message (which will be made by @code{gnus-summary-mail-forward} with the
857 arg 2 for example) or is neither the @samp{text/*} type nor the
858 @samp{message/*} type. Even though in those cases, you can override
859 this setting on a per-message basis by using the @code{encoding}
860 @acronym{MML} tag (@pxref{MML Definition}).
862 @item mm-use-ultra-safe-encoding
863 @vindex mm-use-ultra-safe-encoding
864 When this is non-@code{nil}, it means that textual parts are encoded as
865 quoted-printable if they contain lines longer than 76 characters or
866 starting with "From " in the body. Non-7bit encodings (8bit, binary)
867 are generally disallowed. This reduce the probability that a non-8bit
868 clean MTA or MDA changes the message. This should never be set
869 directly, but bound by other functions when necessary (e.g., when
870 encoding messages that are to be digitally signed).
874 @node Charset Translation
875 @section Charset Translation
878 During translation from @acronym{MML} to @acronym{MIME}, for each
879 @acronym{MIME} part which has been composed inside Emacs, an appropriate
880 charset has to be chosen.
882 @vindex mail-parse-charset
883 If you are running a non-@sc{mule} Emacs, this process is simple: If the
884 part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
885 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
886 variable directly, though. If you want to change the default charset,
887 please consult the documentation of the package which you use to process
888 @acronym{MIME} messages.
889 @xref{Various Message Variables, , Various Message Variables, message,
890 Message Manual}, for example.)
891 If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
897 @vindex mm-mime-mule-charset-alist
898 Things are slightly more complicated when running Emacs with @sc{mule}
899 support. In this case, a list of the @sc{mule} charsets used in the
900 part is obtained, and the @sc{mule} charsets are translated to
901 @acronym{MIME} charsets by consulting the table provided by Emacs itself
902 or the variable @code{mm-mime-mule-charset-alist} for XEmacs.
903 If this results in a single @acronym{MIME} charset, this is used to encode
904 the part. But if the resulting list of @acronym{MIME} charsets contains more
905 than one element, two things can happen: If it is possible to encode the
906 part via UTF-8, this charset is used. (For this, Emacs must support
907 the @code{utf-8} coding system, and the part must consist entirely of
908 characters which have Unicode counterparts.) If UTF-8 is not available
909 for some reason, the part is split into several ones, so that each one
910 can be encoded with a single @acronym{MIME} charset. The part can only be
911 split at line boundaries, though---if more than one @acronym{MIME} charset is
912 required to encode a single line, it is not possible to encode the part.
914 When running Emacs with @sc{mule} support, the preferences for which
915 coding system to use is inherited from Emacs itself. This means that
916 if Emacs is set up to prefer UTF-8, it will be used when encoding
917 messages. You can modify this by altering the
918 @code{mm-coding-system-priorities} variable though (@pxref{Encoding
921 The charset to be used can be overridden by setting the @code{charset}
922 @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
924 The encoding of characters (quoted-printable, 8bit etc) is orthogonal
925 to the discussion here, and is controlled by the variables
926 @code{mm-body-charset-encoding-alist} and
927 @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
934 A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
935 with the @code{mime-to-mml} function. It works on the message in the
936 current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
937 boundaries. Non-textual parts do not have their contents in the buffer,
938 but instead have the contents in separate buffers that are referred to
939 from the @acronym{MML} tags.
942 An @acronym{MML} message can be converted back to @acronym{MIME} by the
943 @code{mml-to-mime} function.
945 These functions are in certain senses ``lossy''---you will not get back
946 an identical message if you run @code{mime-to-mml} and then
947 @code{mml-to-mime}. Not only will trivial things like the order of the
948 headers differ, but the contents of the headers may also be different.
949 For instance, the original message may use base64 encoding on text,
950 while @code{mml-to-mime} may decide to use quoted-printable encoding, and
953 In essence, however, these two functions should be the inverse of each
954 other. The resulting contents of the message should remain equivalent,
960 @cindex format=flowed
962 The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
963 variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
964 emacs, Emacs Manual}) when encoding a message, and the
965 ``format=flowed'' Content-Type parameter when decoding a message.
967 On encoding text, regardless of @code{use-hard-newlines}, lines
968 terminated by soft newline characters are filled together and wrapped
969 after the column decided by @code{fill-flowed-encode-column}.
970 Quotation marks (matching @samp{^>* ?}) are respected. The variable
971 controls how the text will look in a client that does not support
972 flowed text, the default is to wrap after 66 characters. If hard
973 newline characters are not present in the buffer, no flow encoding
976 On decoding flowed text, lines with soft newline characters are filled
977 together and wrapped after the column decided by
978 @code{fill-flowed-display-column}. The default is to wrap after
983 @vindex mm-fill-flowed
984 If non-@code{nil} a format=flowed article will be displayed flowed.
988 @node Interface Functions
989 @chapter Interface Functions
990 @cindex interface functions
993 The @code{mail-parse} library is an abstraction over the actual
994 low-level libraries that are described in the next chapter.
996 Standards change, and so programs have to change to fit in the new
997 mold. For instance, RFC2045 describes a syntax for the
998 @code{Content-Type} header that only allows @acronym{ASCII} characters in the
999 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
1000 for continuation headers and non-@acronym{ASCII} characters.
1002 The traditional way to deal with this is just to update the library
1003 functions to parse the new syntax. However, this is sometimes the wrong
1004 thing to do. In some instances it may be vital to be able to understand
1005 both the old syntax as well as the new syntax, and if there is only one
1006 library, one must choose between the old version of the library and the
1007 new version of the library.
1009 The Emacs @acronym{MIME} library takes a different tack. It defines a
1010 series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
1011 and so on) that parses strictly according to the corresponding
1012 standard. However, normal programs would not use the functions
1013 provided by these libraries directly, but instead use the functions
1014 provided by the @code{mail-parse} library. The functions in this
1015 library are just aliases to the corresponding functions in the latest
1016 low-level libraries. Using this scheme, programs get a consistent
1017 interface they can use, and library developers are free to create
1018 write code that handles new standards.
1020 The following functions are defined by this library:
1023 @item mail-header-parse-content-type
1024 @findex mail-header-parse-content-type
1025 Parse a @code{Content-Type} header and return a list on the following
1030 (attribute1 . value1)
1031 (attribute2 . value2)
1038 (mail-header-parse-content-type
1039 "image/gif; name=\"b980912.gif\"")
1040 @result{} ("image/gif" (name . "b980912.gif"))
1043 @item mail-header-parse-content-disposition
1044 @findex mail-header-parse-content-disposition
1045 Parse a @code{Content-Disposition} header and return a list on the same
1046 format as the function above.
1048 @item mail-content-type-get
1049 @findex mail-content-type-get
1050 Takes two parameters---a list on the format above, and an attribute.
1051 Returns the value of the attribute.
1054 (mail-content-type-get
1055 '("image/gif" (name . "b980912.gif")) 'name)
1056 @result{} "b980912.gif"
1059 @item mail-header-encode-parameter
1060 @findex mail-header-encode-parameter
1061 Takes a parameter string and returns an encoded version of the string.
1062 This is used for parameters in headers like @code{Content-Type} and
1063 @code{Content-Disposition}.
1065 @item mail-header-remove-comments
1066 @findex mail-header-remove-comments
1067 Return a comment-free version of a header.
1070 (mail-header-remove-comments
1071 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1072 @result{} "Gnus/5.070027 "
1075 @item mail-header-remove-whitespace
1076 @findex mail-header-remove-whitespace
1077 Remove linear white space from a header. Space inside quoted strings
1078 and comments is preserved.
1081 (mail-header-remove-whitespace
1082 "image/gif; name=\"Name with spaces\"")
1083 @result{} "image/gif;name=\"Name with spaces\""
1086 @item mail-header-get-comment
1087 @findex mail-header-get-comment
1088 Return the last comment in a header.
1091 (mail-header-get-comment
1092 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1093 @result{} "Finnish Landrace"
1096 @item mail-header-parse-address
1097 @findex mail-header-parse-address
1098 Parse an address and return a list containing the mailbox and the
1102 (mail-header-parse-address
1103 "Hrvoje Niksic <hniksic@@srce.hr>")
1104 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
1107 @item mail-header-parse-addresses
1108 @findex mail-header-parse-addresses
1109 Parse a string with list of addresses and return a list of elements like
1110 the one described above.
1113 (mail-header-parse-addresses
1114 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
1115 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
1116 ("sb@@metis.no" . "Steinar Bang"))
1119 @item mail-header-parse-date
1120 @findex mail-header-parse-date
1121 Parse a date string and return an Emacs time structure.
1123 @item mail-narrow-to-head
1124 @findex mail-narrow-to-head
1125 Narrow the buffer to the header section of the buffer. Point is placed
1126 at the beginning of the narrowed buffer.
1128 @item mail-header-narrow-to-field
1129 @findex mail-header-narrow-to-field
1130 Narrow the buffer to the header under point. Understands continuation
1133 @item mail-header-fold-field
1134 @findex mail-header-fold-field
1135 Fold the header under point.
1137 @item mail-header-unfold-field
1138 @findex mail-header-unfold-field
1139 Unfold the header under point.
1141 @item mail-header-field-value
1142 @findex mail-header-field-value
1143 Return the value of the field under point.
1145 @item mail-encode-encoded-word-region
1146 @findex mail-encode-encoded-word-region
1147 Encode the non-@acronym{ASCII} words in the region. For instance,
1148 @samp{Na@"{@dotless{i}}ve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
1150 @item mail-encode-encoded-word-buffer
1151 @findex mail-encode-encoded-word-buffer
1152 Encode the non-@acronym{ASCII} words in the current buffer. This function is
1153 meant to be called narrowed to the headers of a message.
1155 @item mail-encode-encoded-word-string
1156 @findex mail-encode-encoded-word-string
1157 Encode the words that need encoding in a string, and return the result.
1160 (mail-encode-encoded-word-string
1161 "This is na@"{@dotless{i}}ve, baby")
1162 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
1165 @item mail-decode-encoded-word-region
1166 @findex mail-decode-encoded-word-region
1167 Decode the encoded words in the region.
1169 @item mail-decode-encoded-word-string
1170 @findex mail-decode-encoded-word-string
1171 Decode the encoded words in the string and return the result.
1174 (mail-decode-encoded-word-string
1175 "This is =?iso-8859-1?q?na=EFve,?= baby")
1176 @result{} "This is na@"{@dotless{i}}ve, baby"
1181 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
1182 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
1183 in the subsequent sections.
1187 @node Basic Functions
1188 @chapter Basic Functions
1190 This chapter describes the basic, ground-level functions for parsing and
1191 handling. Covered here is parsing @code{From} lines, removing comments
1192 from header lines, decoding encoded words, parsing date headers and so
1193 on. High-level functionality is dealt with in the first chapter
1194 (@pxref{Decoding and Viewing}).
1197 * rfc2045:: Encoding @code{Content-Type} headers.
1198 * rfc2231:: Parsing @code{Content-Type} headers.
1199 * ietf-drums:: Handling mail headers defined by RFC822bis.
1200 * rfc2047:: En/decoding encoded words in headers.
1201 * time-date:: Functions for parsing dates and manipulating time.
1202 * qp:: Quoted-Printable en/decoding.
1203 * base64:: Base64 en/decoding.
1204 * binhex:: Binhex decoding.
1205 * uudecode:: Uuencode decoding.
1206 * yenc:: Yenc decoding.
1207 * rfc1843:: Decoding HZ-encoded text.
1208 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
1215 RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
1216 imagine that there would be a lot to implement. But there isn't, since
1217 most of the implementation details are delegated to the subsequent
1220 So @file{rfc2045.el} has only a single function:
1223 @item rfc2045-encode-string
1224 @findex rfc2045-encode-string
1225 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
1226 @var{value} will be quoted if there are non-safe characters in it.
1233 RFC2231 defines a syntax for the @code{Content-Type} and
1234 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
1235 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
1238 In short, these headers look something like this:
1241 Content-Type: application/x-stuff;
1242 title*0*=us-ascii'en'This%20is%20even%20more%20;
1243 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1247 They usually aren't this bad, though.
1249 The following functions are defined by this library:
1252 @item rfc2231-parse-string
1253 @findex rfc2231-parse-string
1254 Parse a @code{Content-Type} header and return a list describing its
1258 (rfc2231-parse-string
1259 "application/x-stuff;
1260 title*0*=us-ascii'en'This%20is%20even%20more%20;
1261 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1262 title*2=\"isn't it!\"")
1263 @result{} ("application/x-stuff"
1264 (title . "This is even more ***fun*** isn't it!"))
1267 @item rfc2231-get-value
1268 @findex rfc2231-get-value
1269 Takes one of the lists on the format above and returns
1270 the value of the specified attribute.
1272 @item rfc2231-encode-string
1273 @findex rfc2231-encode-string
1274 Encode a parameter in headers likes @code{Content-Type} and
1275 @code{Content-Disposition}.
1283 @dfn{drums} is an IETF working group that is working on the replacement
1286 The functions provided by this library include:
1289 @item ietf-drums-remove-comments
1290 @findex ietf-drums-remove-comments
1291 Remove the comments from the argument and return the results.
1293 @item ietf-drums-remove-whitespace
1294 @findex ietf-drums-remove-whitespace
1295 Remove linear white space from the string and return the results.
1296 Spaces inside quoted strings and comments are left untouched.
1298 @item ietf-drums-get-comment
1299 @findex ietf-drums-get-comment
1300 Return the last most comment from the string.
1302 @item ietf-drums-parse-address
1303 @findex ietf-drums-parse-address
1304 Parse an address string and return a list that contains the mailbox and
1305 the plain text name.
1307 @item ietf-drums-parse-addresses
1308 @findex ietf-drums-parse-addresses
1309 Parse a string that contains any number of comma-separated addresses and
1310 return a list that contains mailbox/plain text pairs.
1312 @item ietf-drums-parse-date
1313 @findex ietf-drums-parse-date
1314 Parse a date string and return an Emacs time structure.
1316 @item ietf-drums-narrow-to-header
1317 @findex ietf-drums-narrow-to-header
1318 Narrow the buffer to the header section of the current buffer.
1326 RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
1327 non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
1328 complicated, so a number of variables are necessary to tweak what this
1331 The following variables are tweakable:
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 @code{nil}, in which case the header(s) in question
1342 won't be encoded, @code{mime}, which means that they will be encoded, or
1343 @code{address-mime}, which means the header(s) will be encoded carefully
1344 assuming they contain addresses.
1346 @item rfc2047-charset-encoding-alist
1347 @vindex rfc2047-charset-encoding-alist
1348 RFC2047 specifies two forms of encoding---@code{Q} (a
1349 Quoted-Printable-like encoding) and @code{B} (base64). This alist
1350 specifies which charset should use which encoding.
1352 @item rfc2047-encode-function-alist
1353 @vindex rfc2047-encode-function-alist
1354 This is an alist of encoding / function pairs. The encodings are
1355 @code{Q}, @code{B} and @code{nil}.
1357 @item rfc2047-encoded-word-regexp
1358 @vindex rfc2047-encoded-word-regexp
1359 When decoding words, this library looks for matches to this regexp.
1361 @item rfc2047-encode-encoded-words
1362 @vindex rfc2047-encode-encoded-words
1363 The boolean variable specifies whether encoded words
1364 (e.g. @samp{=?hello?=}) should be encoded again.
1368 Those were the variables, and these are this functions:
1371 @item rfc2047-narrow-to-field
1372 @findex rfc2047-narrow-to-field
1373 Narrow the buffer to the header on the current line.
1375 @item rfc2047-encode-message-header
1376 @findex rfc2047-encode-message-header
1377 Should be called narrowed to the header of a message. Encodes according
1378 to @code{rfc2047-header-encoding-alist}.
1380 @item rfc2047-encode-region
1381 @findex rfc2047-encode-region
1382 Encodes all encodable words in the region specified.
1384 @item rfc2047-encode-string
1385 @findex rfc2047-encode-string
1386 Encode a string and return the results.
1388 @item rfc2047-decode-region
1389 @findex rfc2047-decode-region
1390 Decode the encoded words in the region.
1392 @item rfc2047-decode-string
1393 @findex rfc2047-decode-string
1394 Decode a string and return the results.
1396 @item rfc2047-encode-parameter
1397 @findex rfc2047-encode-parameter
1398 Encode a parameter in the RFC2047-like style. This is a replacement for
1399 the @code{rfc2231-encode-string} function. @xref{rfc2231}.
1401 When attaching files as @acronym{MIME} parts, we should use the RFC2231
1402 encoding to specify the file names containing non-@acronym{ASCII}
1403 characters. However, many mail softwares don't support it in practice
1404 and recipients won't be able to extract files with correct names.
1405 Instead, the RFC2047-like encoding is acceptable generally. This
1406 function provides the very RFC2047-like encoding, resigning to such a
1407 regrettable trend. To use it, put the following line in your
1408 @file{~/.gnus.el} file:
1411 (defalias 'mail-header-encode-parameter 'rfc2047-encode-parameter)
1420 While not really a part of the @acronym{MIME} library, it is convenient to
1421 document this library here. It deals with parsing @code{Date} headers
1422 and manipulating time. (Not by using tesseracts, though, I'm sorry to
1425 These functions convert between five formats: A date string, an Emacs
1426 time structure, a decoded time list, a second number, and a day number.
1428 Here's a bunch of time/date/second/day examples:
1431 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
1432 @result{} (54 21 12 12 9 1998 6 nil 7200)
1434 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
1435 @result{} (13818 19266)
1437 (time-to-seconds '(13818 19266))
1438 @result{} 905595714.0
1440 (seconds-to-time 905595714.0)
1441 @result{} (13818 19266 0)
1443 (time-to-days '(13818 19266))
1446 (days-to-time 729644)
1447 @result{} (961933 65536)
1449 (time-since '(13818 19266))
1452 (time-less-p '(13818 19266) '(13818 19145))
1455 (subtract-time '(13818 19266) '(13818 19145))
1458 (days-between "Sat Sep 12 12:21:54 1998 +0200"
1459 "Sat Sep 07 12:21:54 1998 +0200")
1462 (date-leap-year-p 2000)
1465 (time-to-day-in-year '(13818 19266))
1468 (time-to-number-of-days
1470 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
1471 @result{} 4.146122685185185
1474 And finally, we have @code{safe-date-to-time}, which does the same as
1475 @code{date-to-time}, but returns a zero time if the date is
1476 syntactically malformed.
1478 The five data representations used are the following:
1482 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
1483 12:21:54 1998 +0200"}.
1486 An internal Emacs time. For instance: @code{(13818 26466)}.
1489 A floating point representation of the internal Emacs time. For
1490 instance: @code{905595714.0}.
1493 An integer number representing the number of days since 00000101. For
1494 instance: @code{729644}.
1497 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
1501 All the examples above represent the same moment.
1503 These are the functions available:
1507 Take a date and return a time.
1509 @item time-to-seconds
1510 Take a time and return seconds.
1512 @item seconds-to-time
1513 Take seconds and return a time.
1516 Take a time and return days.
1519 Take days and return a time.
1522 Take a date and return days.
1524 @item time-to-number-of-days
1525 Take a time and return the number of days that represents.
1527 @item safe-date-to-time
1528 Take a date and return a time. If the date is not syntactically valid,
1529 return a ``zero'' time.
1532 Take two times and say whether the first time is less (i. e., earlier)
1533 than the second time.
1536 Take a time and return a time saying how long it was since that time.
1539 Take two times and subtract the second from the first. I. e., return
1540 the time between the two times.
1543 Take two days and return the number of days between those two days.
1545 @item date-leap-year-p
1546 Take a year number and say whether it's a leap year.
1548 @item time-to-day-in-year
1549 Take a time and return the day number within the year that the time is
1558 This library deals with decoding and encoding Quoted-Printable text.
1560 Very briefly explained, qp encoding means translating all 8-bit
1561 characters (and lots of control characters) into things that look like
1562 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
1565 The following functions are defined by the library:
1568 @item quoted-printable-decode-region
1569 @findex quoted-printable-decode-region
1570 QP-decode all the encoded text in the specified region.
1572 @item quoted-printable-decode-string
1573 @findex quoted-printable-decode-string
1574 Decode the QP-encoded text in a string and return the results.
1576 @item quoted-printable-encode-region
1577 @findex quoted-printable-encode-region
1578 QP-encode all the encodable characters in the specified region. The third
1579 optional parameter @var{fold} specifies whether to fold long lines.
1580 (Long here means 72.)
1582 @item quoted-printable-encode-string
1583 @findex quoted-printable-encode-string
1584 QP-encode all the encodable characters in a string and return the
1594 Base64 is an encoding that encodes three bytes into four characters,
1595 thereby increasing the size by about 33%. The alphabet used for
1596 encoding is very resistant to mangling during transit.
1598 The following functions are defined by this library:
1601 @item base64-encode-region
1602 @findex base64-encode-region
1603 base64 encode the selected region. Return the length of the encoded
1604 text. Optional third argument @var{no-line-break} means do not break
1605 long lines into shorter lines.
1607 @item base64-encode-string
1608 @findex base64-encode-string
1609 base64 encode a string and return the result.
1611 @item base64-decode-region
1612 @findex base64-decode-region
1613 base64 decode the selected region. Return the length of the decoded
1614 text. If the region can't be decoded, return @code{nil} and don't
1617 @item base64-decode-string
1618 @findex base64-decode-string
1619 base64 decode a string and return the result. If the string can't be
1620 decoded, @code{nil} is returned.
1631 @code{binhex} is an encoding that originated in Macintosh environments.
1632 The following function is supplied to deal with these:
1635 @item binhex-decode-region
1636 @findex binhex-decode-region
1637 Decode the encoded text in the region. If given a third parameter, only
1638 decode the @code{binhex} header and return the filename.
1647 @code{uuencode} is probably still the most popular encoding of binaries
1648 used on Usenet, although @code{base64} rules the mail world.
1650 The following function is supplied by this package:
1653 @item uudecode-decode-region
1654 @findex uudecode-decode-region
1655 Decode the text in the region.
1663 @code{yenc} is used for encoding binaries on Usenet. The following
1664 function is supplied by this package:
1667 @item yenc-decode-region
1668 @findex yenc-decode-region
1669 Decode the encoded text in the region.
1680 RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
1681 essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
1684 This sentence is in @acronym{ASCII}.
1685 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
1688 Simple enough, and widely used in China.
1690 The following functions are available to handle this encoding:
1693 @item rfc1843-decode-region
1694 Decode HZ-encoded text in the region.
1696 @item rfc1843-decode-string
1697 Decode a HZ-encoded string and return the result.
1705 The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
1706 handlers and describes how elements are supposed to be displayed.
1707 Here's an example file:
1711 audio/wav; wavplayer %s
1712 application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
1715 This says that all image files should be displayed with @code{gimp},
1716 that WAVE audio files should be played by @code{wavplayer}, and that
1717 MS-WORD files should be inlined by @code{catdoc}.
1719 The @code{mailcap} library parses this file, and provides functions for
1723 @item mailcap-mime-data
1724 @vindex mailcap-mime-data
1725 This variable is an alist of alists containing backup viewing rules.
1729 Interface functions:
1732 @item mailcap-parse-mailcaps
1733 @findex mailcap-parse-mailcaps
1734 Parse the @file{~/.mailcap} file.
1736 @item mailcap-mime-info
1737 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
1747 The Emacs @acronym{MIME} library implements handling of various elements
1748 according to a (somewhat) large number of RFCs, drafts and standards
1749 documents. This chapter lists the relevant ones. They can all be
1750 fetched from @uref{http://quimby.gnus.org/notes/}.
1755 Standard for the Format of ARPA Internet Text Messages.
1758 Standard for Interchange of USENET Messages
1761 Format of Internet Message Bodies
1767 Message Header Extensions for Non-@acronym{ASCII} Text
1770 Registration Procedures
1773 Conformance Criteria and Examples
1776 @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
1777 Languages, and Continuations
1780 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1781 @acronym{ASCII} characters
1783 @item draft-ietf-drums-msg-fmt-05.txt
1784 Draft for the successor of RFC822
1787 The @acronym{MIME} Multipart/Related Content-type
1790 The Multipart/Report Content Type for the Reporting of Mail System
1791 Administrative Messages
1794 Communicating Presentation Information in Internet Messages: The
1795 Content-Disposition Header Field
1798 Documentation of the text/plain format parameter for flowed text.
1814 @c coding: iso-8859-1
1818 arch-tag: c7ef2fd0-a91c-4e10-aa52-c1a2b11b1a8d