3 @setfilename emacs-mime
4 @settitle Emacs MIME Manual
10 This file documents the Emacs MIME interface functionality.
12 Copyright @copyright{} 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
13 2006 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-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-verbatim}
197 to @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 Adding @code{"image/.*"} might also be useful. Spammers use images as
345 the prefered part of @samp{multipart/alternative} messages, so you might
346 not notice there are other parts. See also
347 @code{gnus-buttonized-mime-types}, @ref{MIME Commands, ,MIME Commands,
348 gnus, Gnus Manual}. After adding @code{"multipart/alternative"} to
349 @code{gnus-buttonized-mime-types} you can choose manually which
350 alternative you'd like to view. For example, you can set those
354 (setq gnus-buttonized-mime-types
355 '("multipart/alternative" "multipart/signed")
356 mm-discouraged-alternatives
357 '("text/html" "image/.*"))
360 In this case, Gnus will display radio buttons for such a kind of spam
364 1. (*) multipart/alternative ( ) image/gif
366 2. (*) text/plain ( ) text/html
369 @item mm-inline-large-images
370 @vindex mm-inline-large-images
371 When displaying inline images that are larger than the window, Emacs
372 does not enable scrolling, which means that you cannot see the whole
373 image. To prevent this, the library tries to determine the image size
374 before displaying it inline, and if it doesn't fit the window, the
375 library will display it externally (e.g. with @samp{ImageMagick} or
376 @samp{xv}). Setting this variable to @code{t} disables this check and
377 makes the library display all inline images as inline, regardless of
380 @item mm-inline-override-types
381 @vindex mm-inline-override-types
382 @code{mm-inlined-types} may include regular expressions, for example to
383 specify that all @samp{text/.*} parts be displayed inline. If a user
384 prefers to have a type that matches such a regular expression be treated
385 as an attachment, that can be accomplished by setting this variable to a
386 list containing that type. For example assuming @code{mm-inlined-types}
387 includes @samp{text/.*}, then including @samp{text/html} in this
388 variable will cause @samp{text/html} parts to be treated as attachments.
390 @item mm-text-html-renderer
391 @vindex mm-text-html-renderer
392 This selects the function used to render @acronym{HTML}. The predefined
393 renderers are selected by the symbols @code{w3},
394 @code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
395 information about emacs-w3m}, @code{links}, @code{lynx},
396 @code{w3m-standalone} or @code{html2text}. If @code{nil} use an
397 external viewer. You can also specify a function, which will be
398 called with a @acronym{MIME} handle as the argument.
400 @item mm-inline-text-html-with-images
401 @vindex mm-inline-text-html-with-images
402 Some @acronym{HTML} mails might have the trick of spammers using
403 @samp{<img>} tags. It is likely to be intended to verify whether you
404 have read the mail. You can prevent your personal informations from
405 leaking by setting this option to @code{nil} (which is the default).
406 It is currently ignored by Emacs/w3. For emacs-w3m, you may use the
407 command @kbd{t} on the image anchor to show an image even if it is
408 @code{nil}.@footnote{The command @kbd{T} will load all images. If you
409 have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
412 @item mm-w3m-safe-url-regexp
413 @vindex mm-w3m-safe-url-regexp
414 A regular expression that matches safe URL names, i.e. URLs that are
415 unlikely to leak personal information when rendering @acronym{HTML}
416 email (the default value is @samp{\\`cid:}). If @code{nil} consider
419 @item mm-inline-text-html-with-w3m-keymap
420 @vindex mm-inline-text-html-with-w3m-keymap
421 You can use emacs-w3m command keys in the inlined text/html part by
422 setting this option to non-@code{nil}. The default value is @code{t}.
424 @item mm-external-terminal-program
425 @vindex mm-external-terminal-program
426 The program used to start an external terminal.
428 @item mm-enable-external
429 @vindex mm-enable-external
430 Indicate whether external @acronym{MIME} handlers should be used.
432 If @code{t}, all defined external @acronym{MIME} handlers are used. If
433 @code{nil}, files are saved to disk (@code{mailcap-save-binary-file}).
434 If it is the symbol @code{ask}, you are prompted before the external
435 @acronym{MIME} handler is invoked.
437 When you launch an attachment through mailcap (@pxref{mailcap}) an
438 attempt is made to use a safe viewer with the safest options---this isn't
439 the case if you save it to disk and launch it in a different way
440 (command line or double-clicking). Anyhow, if you want to be sure not
441 to launch any external programs, set this variable to @code{nil} or
446 @node Files and Directories
447 @section Files and Directories
451 @item mm-default-directory
452 @vindex mm-default-directory
453 The default directory for saving attachments. If @code{nil} use
454 @code{default-directory}.
456 @item mm-tmp-directory
457 @vindex mm-tmp-directory
458 Directory for storing temporary files.
460 @item mm-file-name-rewrite-functions
461 @vindex mm-file-name-rewrite-functions
462 A list of functions used for rewriting file names of @acronym{MIME}
463 parts. Each function is applied successively to the file name.
464 Ready-made functions include
467 @item mm-file-name-delete-control
468 @findex mm-file-name-delete-control
469 Delete all control characters.
471 @item mm-file-name-delete-gotchas
472 @findex mm-file-name-delete-gotchas
473 Delete characters that could have unintended consequences when used
474 with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
475 @samp{-}, @samp{.} as the first character.
477 @item mm-file-name-delete-whitespace
478 @findex mm-file-name-delete-whitespace
479 Remove all whitespace.
481 @item mm-file-name-trim-whitespace
482 @findex mm-file-name-trim-whitespace
483 Remove leading and trailing whitespace.
485 @item mm-file-name-collapse-whitespace
486 @findex mm-file-name-collapse-whitespace
487 Collapse multiple whitespace characters.
489 @item mm-file-name-replace-whitespace
490 @findex mm-file-name-replace-whitespace
491 @vindex mm-file-name-replace-whitespace
492 Replace whitespace with underscores. Set the variable
493 @code{mm-file-name-replace-whitespace} to any other string if you do
494 not like underscores.
497 The standard Emacs functions @code{capitalize}, @code{downcase},
498 @code{upcase} and @code{upcase-initials} might also prove useful.
500 @item mm-path-name-rewrite-functions
501 @vindex mm-path-name-rewrite-functions
502 List of functions used for rewriting the full file names of @acronym{MIME}
503 parts. This is used when viewing parts externally, and is meant for
504 transforming the absolute name so that non-compliant programs can find
505 the file where it's saved.
512 Here's an example viewer for displaying @code{text/enriched} inline:
515 (defun mm-display-enriched-inline (handle)
518 (mm-insert-part handle)
519 (save-window-excursion
520 (enriched-decode (point-min) (point-max))
521 (setq text (buffer-string))))
522 (mm-insert-inline handle text)))
525 We see that the function takes a @acronym{MIME} handle as its parameter. It
526 then goes to a temporary buffer, inserts the text of the part, does some
527 work on the text, stores the result, goes back to the buffer it was
528 called from and inserts the result.
530 The two important helper functions here are @code{mm-insert-part} and
531 @code{mm-insert-inline}. The first function inserts the text of the
532 handle in the current buffer. It handles charset and/or content
533 transfer decoding. The second function just inserts whatever text you
534 tell it to insert, but it also sets things up so that the text can be
535 ``undisplayed'' in a convenient manner.
541 @cindex MIME Composing
543 @cindex MIME Meta Language
545 Creating a @acronym{MIME} message is boring and non-trivial. Therefore,
546 a library called @code{mml} has been defined that parses a language
547 called @acronym{MML} (@acronym{MIME} Meta Language) and generates
548 @acronym{MIME} messages.
550 @findex mml-generate-mime
551 The main interface function is @code{mml-generate-mime}. It will
552 examine the contents of the current (narrowed-to) buffer and return a
553 string containing the @acronym{MIME} message.
556 * Simple MML Example:: An example @acronym{MML} document.
557 * MML Definition:: All valid @acronym{MML} elements.
558 * Advanced MML Example:: Another example @acronym{MML} document.
559 * Encoding Customization:: Variables that affect encoding.
560 * Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
561 * Conversion:: Going from @acronym{MIME} to @acronym{MML} and vice versa.
562 * Flowed text:: Soft and hard newlines.
566 @node Simple MML Example
567 @section Simple MML Example
569 Here's a simple @samp{multipart/alternative}:
572 <#multipart type=alternative>
573 This is a plain text part.
574 <#part type=text/enriched>
575 <center>This is a centered enriched part</center>
579 After running this through @code{mml-generate-mime}, we get this:
582 Content-Type: multipart/alternative; boundary="=-=-="
588 This is a plain text part.
591 Content-Type: text/enriched
594 <center>This is a centered enriched part</center>
601 @section MML Definition
603 The @acronym{MML} language is very simple. It looks a bit like an SGML
604 application, but it's not.
606 The main concept of @acronym{MML} is the @dfn{part}. Each part can be of a
607 different type or use a different charset. The way to delineate a part
608 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
609 with the @samp{<#multipart ...>} tag. Parts are ended by the
610 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
611 @samp{<#part ...>} tags are also closed by the next open tag.
613 There's also the @samp{<#external ...>} tag. These introduce
614 @samp{external/message-body} parts.
616 Each tag can contain zero or more parameters on the form
617 @samp{parameter=value}. The values may be enclosed in quotation marks,
618 but that's not necessary unless the value contains white space. So
619 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
621 The following parameters have meaning in @acronym{MML}; parameters that have no
622 meaning are ignored. The @acronym{MML} parameter names are the same as the
623 @acronym{MIME} parameter names; the things in the parentheses say which
624 header it will be used in.
628 The @acronym{MIME} type of the part (@code{Content-Type}).
631 Use the contents of the file in the body of the part
632 (@code{Content-Disposition}).
635 The contents of the body of the part are to be encoded in the character
636 set specified (@code{Content-Type}). @xref{Charset Translation}.
639 Might be used to suggest a file name if the part is to be saved
640 to a file (@code{Content-Type}).
643 Valid values are @samp{inline} and @samp{attachment}
644 (@code{Content-Disposition}).
647 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
648 @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
652 A description of the part (@code{Content-Description}).
655 RFC822 date when the part was created (@code{Content-Disposition}).
657 @item modification-date
658 RFC822 date when the part was modified (@code{Content-Disposition}).
661 RFC822 date when the part was read (@code{Content-Disposition}).
664 Who to encrypt/sign the part to. This field is used to override any
665 auto-detection based on the To/CC headers.
668 Identity used to sign the part. This field is used to override the
672 The size (in octets) of the part (@code{Content-Disposition}).
675 What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
679 What technology to encrypt this @acronym{MML} part with (@code{smime},
680 @code{pgp} or @code{pgpmime})
684 Parameters for @samp{text/plain}:
688 Formatting parameter for the text, valid values include @samp{fixed}
689 (the default) and @samp{flowed}. Normally you do not specify this
690 manually, since it requires the textual body to be formatted in a
691 special way described in RFC 2646. @xref{Flowed text}.
694 Parameters for @samp{application/octet-stream}:
698 Type of the part; informal---meant for human readers
699 (@code{Content-Type}).
702 Parameters for @samp{message/external-body}:
706 A word indicating the supported access mechanism by which the file may
707 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
708 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
711 The RFC822 date after which the file may no longer be fetched.
712 (@code{Content-Type}.)
715 The size (in octets) of the file. (@code{Content-Type}.)
718 Valid values are @samp{read} and @samp{read-write}
719 (@code{Content-Type}).
723 Parameters for @samp{sign=smime}:
728 File containing key and certificate for signer.
732 Parameters for @samp{encrypt=smime}:
737 File containing certificate for recipient.
742 @node Advanced MML Example
743 @section Advanced MML Example
745 Here's a complex multipart message. It's a @samp{multipart/mixed} that
746 contains many parts, one of which is a @samp{multipart/alternative}.
749 <#multipart type=mixed>
750 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
751 <#multipart type=alternative>
752 This is a plain text part.
753 <#part type=text/enriched name=enriched.txt>
754 <center>This is a centered enriched part</center>
756 This is a new plain text part.
757 <#part disposition=attachment>
758 This plain text part is an attachment.
762 And this is the resulting @acronym{MIME} message:
765 Content-Type: multipart/mixed; boundary="=-=-="
773 Content-Type: image/jpeg;
775 Content-Disposition: inline;
777 Content-Transfer-Encoding: base64
779 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
780 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
781 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
782 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
783 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
784 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
785 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
786 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
787 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
788 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
789 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
790 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
791 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
792 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
793 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
794 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
795 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
798 Content-Type: multipart/alternative; boundary="==-=-="
804 This is a plain text part.
807 Content-Type: text/enriched;
811 <center>This is a centered enriched part</center>
817 This is a new plain text part.
820 Content-Disposition: attachment
823 This plain text part is an attachment.
828 @node Encoding Customization
829 @section Encoding Customization
833 @item mm-body-charset-encoding-alist
834 @vindex mm-body-charset-encoding-alist
835 Mapping from @acronym{MIME} charset to encoding to use. This variable is
836 usually used except, e.g., when other requirements force a specific
837 encoding (digitally signed messages require 7bit encodings). The
841 ((iso-2022-jp . 7bit)
842 (iso-2022-jp-2 . 7bit)
848 As an example, if you do not want to have ISO-8859-1 characters
849 quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
850 this variable. You can override this setting on a per-message basis
851 by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
853 @item mm-coding-system-priorities
854 @vindex mm-coding-system-priorities
855 Prioritize coding systems to use for outgoing messages. The default
856 is @code{nil}, which means to use the defaults in Emacs, but is
857 @code{(iso-8859-1 iso-2022-jp iso-2022-jp-2 shift_jis utf-8)} when
858 running Emacs in the Japanese language environment. It is a list of
859 coding system symbols (aliases of coding systems are also allowed, use
860 @kbd{M-x describe-coding-system} to make sure you are specifying correct
861 coding system names). For example, if you have configured Emacs
862 to prefer UTF-8, but wish that outgoing messages should be sent in
863 ISO-8859-1 if possible, you can set this variable to
864 @code{(iso-8859-1)}. You can override this setting on a per-message
865 basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
867 @item mm-content-transfer-encoding-defaults
868 @vindex mm-content-transfer-encoding-defaults
869 Mapping from @acronym{MIME} types to encoding to use. This variable is usually
870 used except, e.g., when other requirements force a safer encoding
871 (digitally signed messages require 7bit encoding). Besides the normal
872 @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
873 each case the most efficient of quoted-printable and base64 should be
876 @code{qp-or-base64} has another effect. It will fold long lines so that
877 MIME parts may not be broken by MTA. So do @code{quoted-printable} and
880 Note that it affects body encoding only when a part is a raw forwarded
881 message (which will be made by @code{gnus-summary-mail-forward} with the
882 arg 2 for example) or is neither the @samp{text/*} type nor the
883 @samp{message/*} type. Even though in those cases, you can override
884 this setting on a per-message basis by using the @code{encoding}
885 @acronym{MML} tag (@pxref{MML Definition}).
887 @item mm-use-ultra-safe-encoding
888 @vindex mm-use-ultra-safe-encoding
889 When this is non-@code{nil}, it means that textual parts are encoded as
890 quoted-printable if they contain lines longer than 76 characters or
891 starting with "From " in the body. Non-7bit encodings (8bit, binary)
892 are generally disallowed. This reduce the probability that a non-8bit
893 clean MTA or MDA changes the message. This should never be set
894 directly, but bound by other functions when necessary (e.g., when
895 encoding messages that are to be digitally signed).
899 @node Charset Translation
900 @section Charset Translation
903 During translation from @acronym{MML} to @acronym{MIME}, for each
904 @acronym{MIME} part which has been composed inside Emacs, an appropriate
905 charset has to be chosen.
907 @vindex mail-parse-charset
908 If you are running a non-@sc{mule} Emacs, this process is simple: If the
909 part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
910 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
911 variable directly, though. If you want to change the default charset,
912 please consult the documentation of the package which you use to process
913 @acronym{MIME} messages.
914 @xref{Various Message Variables, , Various Message Variables, message,
915 Message Manual}, for example.)
916 If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
922 @vindex mm-mime-mule-charset-alist
923 Things are slightly more complicated when running Emacs with @sc{mule}
924 support. In this case, a list of the @sc{mule} charsets used in the
925 part is obtained, and the @sc{mule} charsets are translated to
926 @acronym{MIME} charsets by consulting the table provided by Emacs itself
927 or the variable @code{mm-mime-mule-charset-alist} for XEmacs.
928 If this results in a single @acronym{MIME} charset, this is used to encode
929 the part. But if the resulting list of @acronym{MIME} charsets contains more
930 than one element, two things can happen: If it is possible to encode the
931 part via UTF-8, this charset is used. (For this, Emacs must support
932 the @code{utf-8} coding system, and the part must consist entirely of
933 characters which have Unicode counterparts.) If UTF-8 is not available
934 for some reason, the part is split into several ones, so that each one
935 can be encoded with a single @acronym{MIME} charset. The part can only be
936 split at line boundaries, though---if more than one @acronym{MIME} charset is
937 required to encode a single line, it is not possible to encode the part.
939 When running Emacs with @sc{mule} support, the preferences for which
940 coding system to use is inherited from Emacs itself. This means that
941 if Emacs is set up to prefer UTF-8, it will be used when encoding
942 messages. You can modify this by altering the
943 @code{mm-coding-system-priorities} variable though (@pxref{Encoding
946 The charset to be used can be overridden by setting the @code{charset}
947 @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
949 The encoding of characters (quoted-printable, 8bit etc) is orthogonal
950 to the discussion here, and is controlled by the variables
951 @code{mm-body-charset-encoding-alist} and
952 @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
959 A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
960 with the @code{mime-to-mml} function. It works on the message in the
961 current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
962 boundaries. Non-textual parts do not have their contents in the buffer,
963 but instead have the contents in separate buffers that are referred to
964 from the @acronym{MML} tags.
967 An @acronym{MML} message can be converted back to @acronym{MIME} by the
968 @code{mml-to-mime} function.
970 These functions are in certain senses ``lossy''---you will not get back
971 an identical message if you run @code{mime-to-mml} and then
972 @code{mml-to-mime}. Not only will trivial things like the order of the
973 headers differ, but the contents of the headers may also be different.
974 For instance, the original message may use base64 encoding on text,
975 while @code{mml-to-mime} may decide to use quoted-printable encoding, and
978 In essence, however, these two functions should be the inverse of each
979 other. The resulting contents of the message should remain equivalent,
985 @cindex format=flowed
987 The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
988 variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
989 emacs, Emacs Manual}) when encoding a message, and the
990 ``format=flowed'' Content-Type parameter when decoding a message.
992 On encoding text, regardless of @code{use-hard-newlines}, lines
993 terminated by soft newline characters are filled together and wrapped
994 after the column decided by @code{fill-flowed-encode-column}.
995 Quotation marks (matching @samp{^>* ?}) are respected. The variable
996 controls how the text will look in a client that does not support
997 flowed text, the default is to wrap after 66 characters. If hard
998 newline characters are not present in the buffer, no flow encoding
1001 On decoding flowed text, lines with soft newline characters are filled
1002 together and wrapped after the column decided by
1003 @code{fill-flowed-display-column}. The default is to wrap after
1007 @item mm-fill-flowed
1008 @vindex mm-fill-flowed
1009 If non-@code{nil} a format=flowed article will be displayed flowed.
1013 @node Interface Functions
1014 @chapter Interface Functions
1015 @cindex interface functions
1018 The @code{mail-parse} library is an abstraction over the actual
1019 low-level libraries that are described in the next chapter.
1021 Standards change, and so programs have to change to fit in the new
1022 mold. For instance, RFC2045 describes a syntax for the
1023 @code{Content-Type} header that only allows @acronym{ASCII} characters in the
1024 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
1025 for continuation headers and non-@acronym{ASCII} characters.
1027 The traditional way to deal with this is just to update the library
1028 functions to parse the new syntax. However, this is sometimes the wrong
1029 thing to do. In some instances it may be vital to be able to understand
1030 both the old syntax as well as the new syntax, and if there is only one
1031 library, one must choose between the old version of the library and the
1032 new version of the library.
1034 The Emacs @acronym{MIME} library takes a different tack. It defines a
1035 series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
1036 and so on) that parses strictly according to the corresponding
1037 standard. However, normal programs would not use the functions
1038 provided by these libraries directly, but instead use the functions
1039 provided by the @code{mail-parse} library. The functions in this
1040 library are just aliases to the corresponding functions in the latest
1041 low-level libraries. Using this scheme, programs get a consistent
1042 interface they can use, and library developers are free to create
1043 write code that handles new standards.
1045 The following functions are defined by this library:
1048 @item mail-header-parse-content-type
1049 @findex mail-header-parse-content-type
1050 Parse a @code{Content-Type} header and return a list on the following
1055 (attribute1 . value1)
1056 (attribute2 . value2)
1063 (mail-header-parse-content-type
1064 "image/gif; name=\"b980912.gif\"")
1065 @result{} ("image/gif" (name . "b980912.gif"))
1068 @item mail-header-parse-content-disposition
1069 @findex mail-header-parse-content-disposition
1070 Parse a @code{Content-Disposition} header and return a list on the same
1071 format as the function above.
1073 @item mail-content-type-get
1074 @findex mail-content-type-get
1075 Takes two parameters---a list on the format above, and an attribute.
1076 Returns the value of the attribute.
1079 (mail-content-type-get
1080 '("image/gif" (name . "b980912.gif")) 'name)
1081 @result{} "b980912.gif"
1084 @item mail-header-encode-parameter
1085 @findex mail-header-encode-parameter
1086 Takes a parameter string and returns an encoded version of the string.
1087 This is used for parameters in headers like @code{Content-Type} and
1088 @code{Content-Disposition}.
1090 @item mail-header-remove-comments
1091 @findex mail-header-remove-comments
1092 Return a comment-free version of a header.
1095 (mail-header-remove-comments
1096 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1097 @result{} "Gnus/5.070027 "
1100 @item mail-header-remove-whitespace
1101 @findex mail-header-remove-whitespace
1102 Remove linear white space from a header. Space inside quoted strings
1103 and comments is preserved.
1106 (mail-header-remove-whitespace
1107 "image/gif; name=\"Name with spaces\"")
1108 @result{} "image/gif;name=\"Name with spaces\""
1111 @item mail-header-get-comment
1112 @findex mail-header-get-comment
1113 Return the last comment in a header.
1116 (mail-header-get-comment
1117 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1118 @result{} "Finnish Landrace"
1121 @item mail-header-parse-address
1122 @findex mail-header-parse-address
1123 Parse an address and return a list containing the mailbox and the
1127 (mail-header-parse-address
1128 "Hrvoje Niksic <hniksic@@srce.hr>")
1129 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
1132 @item mail-header-parse-addresses
1133 @findex mail-header-parse-addresses
1134 Parse a string with list of addresses and return a list of elements like
1135 the one described above.
1138 (mail-header-parse-addresses
1139 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
1140 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
1141 ("sb@@metis.no" . "Steinar Bang"))
1144 @item mail-header-parse-date
1145 @findex mail-header-parse-date
1146 Parse a date string and return an Emacs time structure.
1148 @item mail-narrow-to-head
1149 @findex mail-narrow-to-head
1150 Narrow the buffer to the header section of the buffer. Point is placed
1151 at the beginning of the narrowed buffer.
1153 @item mail-header-narrow-to-field
1154 @findex mail-header-narrow-to-field
1155 Narrow the buffer to the header under point. Understands continuation
1158 @item mail-header-fold-field
1159 @findex mail-header-fold-field
1160 Fold the header under point.
1162 @item mail-header-unfold-field
1163 @findex mail-header-unfold-field
1164 Unfold the header under point.
1166 @item mail-header-field-value
1167 @findex mail-header-field-value
1168 Return the value of the field under point.
1170 @item mail-encode-encoded-word-region
1171 @findex mail-encode-encoded-word-region
1172 Encode the non-@acronym{ASCII} words in the region. For instance,
1173 @samp{Na@"{@dotless{i}}ve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
1175 @item mail-encode-encoded-word-buffer
1176 @findex mail-encode-encoded-word-buffer
1177 Encode the non-@acronym{ASCII} words in the current buffer. This function is
1178 meant to be called narrowed to the headers of a message.
1180 @item mail-encode-encoded-word-string
1181 @findex mail-encode-encoded-word-string
1182 Encode the words that need encoding in a string, and return the result.
1185 (mail-encode-encoded-word-string
1186 "This is na@"{@dotless{i}}ve, baby")
1187 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
1190 @item mail-decode-encoded-word-region
1191 @findex mail-decode-encoded-word-region
1192 Decode the encoded words in the region.
1194 @item mail-decode-encoded-word-string
1195 @findex mail-decode-encoded-word-string
1196 Decode the encoded words in the string and return the result.
1199 (mail-decode-encoded-word-string
1200 "This is =?iso-8859-1?q?na=EFve,?= baby")
1201 @result{} "This is na@"{@dotless{i}}ve, baby"
1206 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
1207 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
1208 in the subsequent sections.
1212 @node Basic Functions
1213 @chapter Basic Functions
1215 This chapter describes the basic, ground-level functions for parsing and
1216 handling. Covered here is parsing @code{From} lines, removing comments
1217 from header lines, decoding encoded words, parsing date headers and so
1218 on. High-level functionality is dealt with in the first chapter
1219 (@pxref{Decoding and Viewing}).
1222 * rfc2045:: Encoding @code{Content-Type} headers.
1223 * rfc2231:: Parsing @code{Content-Type} headers.
1224 * ietf-drums:: Handling mail headers defined by RFC822bis.
1225 * rfc2047:: En/decoding encoded words in headers.
1226 * time-date:: Functions for parsing dates and manipulating time.
1227 * qp:: Quoted-Printable en/decoding.
1228 * base64:: Base64 en/decoding.
1229 * binhex:: Binhex decoding.
1230 * uudecode:: Uuencode decoding.
1231 * yenc:: Yenc decoding.
1232 * rfc1843:: Decoding HZ-encoded text.
1233 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
1240 RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
1241 imagine that there would be a lot to implement. But there isn't, since
1242 most of the implementation details are delegated to the subsequent
1245 So @file{rfc2045.el} has only a single function:
1248 @item rfc2045-encode-string
1249 @findex rfc2045-encode-string
1250 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
1251 @var{value} will be quoted if there are non-safe characters in it.
1258 RFC2231 defines a syntax for the @code{Content-Type} and
1259 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
1260 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
1263 In short, these headers look something like this:
1266 Content-Type: application/x-stuff;
1267 title*0*=us-ascii'en'This%20is%20even%20more%20;
1268 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1272 They usually aren't this bad, though.
1274 The following functions are defined by this library:
1277 @item rfc2231-parse-string
1278 @findex rfc2231-parse-string
1279 Parse a @code{Content-Type} header and return a list describing its
1283 (rfc2231-parse-string
1284 "application/x-stuff;
1285 title*0*=us-ascii'en'This%20is%20even%20more%20;
1286 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1287 title*2=\"isn't it!\"")
1288 @result{} ("application/x-stuff"
1289 (title . "This is even more ***fun*** isn't it!"))
1292 @item rfc2231-get-value
1293 @findex rfc2231-get-value
1294 Takes one of the lists on the format above and returns
1295 the value of the specified attribute.
1297 @item rfc2231-encode-string
1298 @findex rfc2231-encode-string
1299 Encode a parameter in headers likes @code{Content-Type} and
1300 @code{Content-Disposition}.
1308 @dfn{drums} is an IETF working group that is working on the replacement
1311 The functions provided by this library include:
1314 @item ietf-drums-remove-comments
1315 @findex ietf-drums-remove-comments
1316 Remove the comments from the argument and return the results.
1318 @item ietf-drums-remove-whitespace
1319 @findex ietf-drums-remove-whitespace
1320 Remove linear white space from the string and return the results.
1321 Spaces inside quoted strings and comments are left untouched.
1323 @item ietf-drums-get-comment
1324 @findex ietf-drums-get-comment
1325 Return the last most comment from the string.
1327 @item ietf-drums-parse-address
1328 @findex ietf-drums-parse-address
1329 Parse an address string and return a list that contains the mailbox and
1330 the plain text name.
1332 @item ietf-drums-parse-addresses
1333 @findex ietf-drums-parse-addresses
1334 Parse a string that contains any number of comma-separated addresses and
1335 return a list that contains mailbox/plain text pairs.
1337 @item ietf-drums-parse-date
1338 @findex ietf-drums-parse-date
1339 Parse a date string and return an Emacs time structure.
1341 @item ietf-drums-narrow-to-header
1342 @findex ietf-drums-narrow-to-header
1343 Narrow the buffer to the header section of the current buffer.
1351 RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
1352 non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
1353 complicated, so a number of variables are necessary to tweak what this
1356 The following variables are tweakable:
1359 @item rfc2047-header-encoding-alist
1360 @vindex rfc2047-header-encoding-alist
1361 This is an alist of header / encoding-type pairs. Its main purpose is
1362 to prevent encoding of certain headers.
1364 The keys can either be header regexps, or @code{t}.
1366 The values can be @code{nil}, in which case the header(s) in question
1367 won't be encoded, @code{mime}, which means that they will be encoded, or
1368 @code{address-mime}, which means the header(s) will be encoded carefully
1369 assuming they contain addresses.
1371 @item rfc2047-charset-encoding-alist
1372 @vindex rfc2047-charset-encoding-alist
1373 RFC2047 specifies two forms of encoding---@code{Q} (a
1374 Quoted-Printable-like encoding) and @code{B} (base64). This alist
1375 specifies which charset should use which encoding.
1377 @item rfc2047-encode-function-alist
1378 @vindex rfc2047-encode-function-alist
1379 This is an alist of encoding / function pairs. The encodings are
1380 @code{Q}, @code{B} and @code{nil}.
1382 @item rfc2047-encoded-word-regexp
1383 @vindex rfc2047-encoded-word-regexp
1384 When decoding words, this library looks for matches to this regexp.
1386 @item rfc2047-encode-encoded-words
1387 @vindex rfc2047-encode-encoded-words
1388 The boolean variable specifies whether encoded words
1389 (e.g. @samp{=?hello?=}) should be encoded again.
1393 Those were the variables, and these are this functions:
1396 @item rfc2047-narrow-to-field
1397 @findex rfc2047-narrow-to-field
1398 Narrow the buffer to the header on the current line.
1400 @item rfc2047-encode-message-header
1401 @findex rfc2047-encode-message-header
1402 Should be called narrowed to the header of a message. Encodes according
1403 to @code{rfc2047-header-encoding-alist}.
1405 @item rfc2047-encode-region
1406 @findex rfc2047-encode-region
1407 Encodes all encodable words in the region specified.
1409 @item rfc2047-encode-string
1410 @findex rfc2047-encode-string
1411 Encode a string and return the results.
1413 @item rfc2047-decode-region
1414 @findex rfc2047-decode-region
1415 Decode the encoded words in the region.
1417 @item rfc2047-decode-string
1418 @findex rfc2047-decode-string
1419 Decode a string and return the results.
1421 @item rfc2047-encode-parameter
1422 @findex rfc2047-encode-parameter
1423 Encode a parameter in the RFC2047-like style. This is a replacement for
1424 the @code{rfc2231-encode-string} function. @xref{rfc2231}.
1426 When attaching files as @acronym{MIME} parts, we should use the RFC2231
1427 encoding to specify the file names containing non-@acronym{ASCII}
1428 characters. However, many mail softwares don't support it in practice
1429 and recipients won't be able to extract files with correct names.
1430 Instead, the RFC2047-like encoding is acceptable generally. This
1431 function provides the very RFC2047-like encoding, resigning to such a
1432 regrettable trend. To use it, put the following line in your
1433 @file{~/.gnus.el} file:
1436 (defalias 'mail-header-encode-parameter 'rfc2047-encode-parameter)
1445 While not really a part of the @acronym{MIME} library, it is convenient to
1446 document this library here. It deals with parsing @code{Date} headers
1447 and manipulating time. (Not by using tesseracts, though, I'm sorry to
1450 These functions convert between five formats: A date string, an Emacs
1451 time structure, a decoded time list, a second number, and a day number.
1453 Here's a bunch of time/date/second/day examples:
1456 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
1457 @result{} (54 21 12 12 9 1998 6 nil 7200)
1459 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
1460 @result{} (13818 19266)
1462 (time-to-seconds '(13818 19266))
1463 @result{} 905595714.0
1465 (seconds-to-time 905595714.0)
1466 @result{} (13818 19266 0)
1468 (time-to-days '(13818 19266))
1471 (days-to-time 729644)
1472 @result{} (961933 65536)
1474 (time-since '(13818 19266))
1477 (time-less-p '(13818 19266) '(13818 19145))
1480 (subtract-time '(13818 19266) '(13818 19145))
1483 (days-between "Sat Sep 12 12:21:54 1998 +0200"
1484 "Sat Sep 07 12:21:54 1998 +0200")
1487 (date-leap-year-p 2000)
1490 (time-to-day-in-year '(13818 19266))
1493 (time-to-number-of-days
1495 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
1496 @result{} 4.146122685185185
1499 And finally, we have @code{safe-date-to-time}, which does the same as
1500 @code{date-to-time}, but returns a zero time if the date is
1501 syntactically malformed.
1503 The five data representations used are the following:
1507 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
1508 12:21:54 1998 +0200"}.
1511 An internal Emacs time. For instance: @code{(13818 26466)}.
1514 A floating point representation of the internal Emacs time. For
1515 instance: @code{905595714.0}.
1518 An integer number representing the number of days since 00000101. For
1519 instance: @code{729644}.
1522 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
1526 All the examples above represent the same moment.
1528 These are the functions available:
1532 Take a date and return a time.
1534 @item time-to-seconds
1535 Take a time and return seconds.
1537 @item seconds-to-time
1538 Take seconds and return a time.
1541 Take a time and return days.
1544 Take days and return a time.
1547 Take a date and return days.
1549 @item time-to-number-of-days
1550 Take a time and return the number of days that represents.
1552 @item safe-date-to-time
1553 Take a date and return a time. If the date is not syntactically valid,
1554 return a ``zero'' time.
1557 Take two times and say whether the first time is less (i. e., earlier)
1558 than the second time.
1561 Take a time and return a time saying how long it was since that time.
1564 Take two times and subtract the second from the first. I. e., return
1565 the time between the two times.
1568 Take two days and return the number of days between those two days.
1570 @item date-leap-year-p
1571 Take a year number and say whether it's a leap year.
1573 @item time-to-day-in-year
1574 Take a time and return the day number within the year that the time is
1583 This library deals with decoding and encoding Quoted-Printable text.
1585 Very briefly explained, qp encoding means translating all 8-bit
1586 characters (and lots of control characters) into things that look like
1587 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
1590 The following functions are defined by the library:
1593 @item quoted-printable-decode-region
1594 @findex quoted-printable-decode-region
1595 QP-decode all the encoded text in the specified region.
1597 @item quoted-printable-decode-string
1598 @findex quoted-printable-decode-string
1599 Decode the QP-encoded text in a string and return the results.
1601 @item quoted-printable-encode-region
1602 @findex quoted-printable-encode-region
1603 QP-encode all the encodable characters in the specified region. The third
1604 optional parameter @var{fold} specifies whether to fold long lines.
1605 (Long here means 72.)
1607 @item quoted-printable-encode-string
1608 @findex quoted-printable-encode-string
1609 QP-encode all the encodable characters in a string and return the
1619 Base64 is an encoding that encodes three bytes into four characters,
1620 thereby increasing the size by about 33%. The alphabet used for
1621 encoding is very resistant to mangling during transit.
1623 The following functions are defined by this library:
1626 @item base64-encode-region
1627 @findex base64-encode-region
1628 base64 encode the selected region. Return the length of the encoded
1629 text. Optional third argument @var{no-line-break} means do not break
1630 long lines into shorter lines.
1632 @item base64-encode-string
1633 @findex base64-encode-string
1634 base64 encode a string and return the result.
1636 @item base64-decode-region
1637 @findex base64-decode-region
1638 base64 decode the selected region. Return the length of the decoded
1639 text. If the region can't be decoded, return @code{nil} and don't
1642 @item base64-decode-string
1643 @findex base64-decode-string
1644 base64 decode a string and return the result. If the string can't be
1645 decoded, @code{nil} is returned.
1656 @code{binhex} is an encoding that originated in Macintosh environments.
1657 The following function is supplied to deal with these:
1660 @item binhex-decode-region
1661 @findex binhex-decode-region
1662 Decode the encoded text in the region. If given a third parameter, only
1663 decode the @code{binhex} header and return the filename.
1672 @code{uuencode} is probably still the most popular encoding of binaries
1673 used on Usenet, although @code{base64} rules the mail world.
1675 The following function is supplied by this package:
1678 @item uudecode-decode-region
1679 @findex uudecode-decode-region
1680 Decode the text in the region.
1688 @code{yenc} is used for encoding binaries on Usenet. The following
1689 function is supplied by this package:
1692 @item yenc-decode-region
1693 @findex yenc-decode-region
1694 Decode the encoded text in the region.
1705 RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
1706 essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
1709 This sentence is in @acronym{ASCII}.
1710 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
1713 Simple enough, and widely used in China.
1715 The following functions are available to handle this encoding:
1718 @item rfc1843-decode-region
1719 Decode HZ-encoded text in the region.
1721 @item rfc1843-decode-string
1722 Decode a HZ-encoded string and return the result.
1730 The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
1731 handlers and describes how elements are supposed to be displayed.
1732 Here's an example file:
1736 audio/wav; wavplayer %s
1737 application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
1740 This says that all image files should be displayed with @code{gimp},
1741 that WAVE audio files should be played by @code{wavplayer}, and that
1742 MS-WORD files should be inlined by @code{catdoc}.
1744 The @code{mailcap} library parses this file, and provides functions for
1748 @item mailcap-mime-data
1749 @vindex mailcap-mime-data
1750 This variable is an alist of alists containing backup viewing rules.
1754 Interface functions:
1757 @item mailcap-parse-mailcaps
1758 @findex mailcap-parse-mailcaps
1759 Parse the @file{~/.mailcap} file.
1761 @item mailcap-mime-info
1762 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
1772 The Emacs @acronym{MIME} library implements handling of various elements
1773 according to a (somewhat) large number of RFCs, drafts and standards
1774 documents. This chapter lists the relevant ones. They can all be
1775 fetched from @uref{http://quimby.gnus.org/notes/}.
1780 Standard for the Format of ARPA Internet Text Messages.
1783 Standard for Interchange of USENET Messages
1786 Format of Internet Message Bodies
1792 Message Header Extensions for Non-@acronym{ASCII} Text
1795 Registration Procedures
1798 Conformance Criteria and Examples
1801 @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
1802 Languages, and Continuations
1805 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1806 @acronym{ASCII} characters
1808 @item draft-ietf-drums-msg-fmt-05.txt
1809 Draft for the successor of RFC822
1812 The @acronym{MIME} Multipart/Related Content-type
1815 The Multipart/Report Content Type for the Reporting of Mail System
1816 Administrative Messages
1819 Communicating Presentation Information in Internet Messages: The
1820 Content-Disposition Header Field
1823 Documentation of the text/plain format parameter for flowed text.
1839 @c coding: iso-8859-1
1843 arch-tag: c7ef2fd0-a91c-4e10-aa52-c1a2b11b1a8d