[Emacs-diffs] Changes to emacs/man/emacs-mime.texi [gnus-5_10-branch]

[Reiner Steib]

Index: emacs/man/emacs-mime.texi
diff -c /dev/null emacs/man/emacs-mime.texi:1.20.2.1
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+ \input texinfo
+ 
+ @setfilename ../info/emacs-mime
+ @settitle Emacs MIME Manual
+ @synindex fn cp
+ @synindex vr cp
+ @synindex pg cp
+ @dircategory Emacs
+ @direntry
+ * Emacs MIME: (emacs-mime).   The MIME de/composition library.
+ @end direntry
+ @iftex
+ @finalout
+ @end iftex
+ @setchapternewpage odd
+ 
+ @ifnottex
+ 
+ This file documents the Emacs MIME interface functionality.
+ 
+ Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003
+           Free Software Foundation, Inc.
+ 
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.1 or
+ any later version published by the Free Software Foundation; with no
+ Invariant Sections, with the Front-Cover texts being ``A GNU
+ Manual'', and with the Back-Cover Texts as in (a) below.  A copy of the
+ license is included in the section entitled ``GNU Free Documentation
+ License'' in the Emacs manual.
+ 
+ (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
+ this GNU Manual, like GNU software.  Copies published by the Free
+ Software Foundation raise funds for GNU development.''
+ 
+ This document is part of a collection distributed under the GNU Free
+ Documentation License.  If you want to distribute this document
+ separately from the collection, you can do so by adding a copy of the
+ license to the document, as described in section 6 of the license.
+ @end ifnottex
+ 
+ @tex
+ 
+ @titlepage
+ @title Emacs MIME Manual
+ 
+ @author by Lars Magne Ingebrigtsen
+ @page
+ 
+ @vskip 0pt plus 1filll
+ Copyright @copyright{} 1998, 1999, 2000, 2001, 2002, 2003 Free Software
+ Foundation, Inc.
+ 
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.1 or
+ any later version published by the Free Software Foundation; with the
+ Invariant Sections being none, with the Front-Cover texts being ``A GNU
+ Manual'', and with the Back-Cover Texts as in (a) below.  A copy of the
+ license is included in the section entitled ``GNU Free Documentation
+ License'' in the Emacs manual.
+ 
+ (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
+ this GNU Manual, like GNU software.  Copies published by the Free
+ Software Foundation raise funds for GNU development.''
+ 
+ This document is part of a collection distributed under the GNU Free
+ Documentation License.  If you want to distribute this document
+ separately from the collection, you can do so by adding a copy of the
+ license to the document, as described in section 6 of the license.
+ @end titlepage
+ @page
+ 
+ @end tex
+ 
+ @node Top
+ @top Emacs MIME
+ 
+ This manual documents the libraries used to compose and display
+ @acronym{MIME} messages.
+ 
+ This manual is directed at users who want to modify the behaviour of
+ the @acronym{MIME} encoding/decoding process or want a more detailed
+ picture of how the Emacs @acronym{MIME} library works, and people who want
+ to write functions and commands that manipulate @acronym{MIME} elements.
+ 
+ @acronym{MIME} is short for @dfn{Multipurpose Internet Mail Extensions}.
+ This standard is documented in a number of RFCs; mainly RFC2045 (Format
+ of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
+ Header Extensions for address@hidden Text), RFC2048 (Registration
+ Procedures), RFC2049 (Conformance Criteria and Examples).  It is highly
+ recommended that anyone who intends writing @acronym{MIME}-compliant software
+ read at least RFC2045 and RFC2047.
+ 
+ @menu
+ * Decoding and Viewing::  A framework for decoding and viewing.
+ * Composing::             @acronym{MML}; a language for describing 
@acronym{MIME} parts.
+ * Interface Functions::   An abstraction over the basic functions.
+ * Basic Functions::       Utility and basic parsing functions.
+ * Standards::             A summary of RFCs and working documents used.
+ * Index::                 Function and variable index.
+ @end menu
+ 
+ 
+ @node Decoding and Viewing
+ @chapter Decoding and Viewing
+ 
+ This chapter deals with decoding and viewing @acronym{MIME} messages on a
+ higher level.
+ 
+ The main idea is to first analyze a @acronym{MIME} article, and then allow
+ other programs to do things based on the list of @dfn{handles} that are
+ returned as a result of this analysis.
+ 
+ @menu
+ * Dissection::             Analyzing a @acronym{MIME} message.
+ * Non-MIME::               Analyzing a address@hidden message.
+ * Handles::                Handle manipulations.
+ * Display::                Displaying handles.
+ * Display Customization::  Variables that affect display.
+ * Files and Directories::  Saving and naming attachments.
+ * New Viewers::            How to write your own viewers.
+ @end menu
+ 
+ 
+ @node Dissection
+ @section Dissection
+ 
+ The @code{mm-dissect-buffer} is the function responsible for dissecting
+ a @acronym{MIME} article.  If given a multipart message, it will recursively
+ descend the message, following the structure, and return a tree of
+ @acronym{MIME} handles that describes the structure of the message.
+ 
+ @node Non-MIME
+ @section Non-MIME
+ @vindex mm-uu-configure-list
+ 
+ Gnus also understands some address@hidden attachments, such as
+ postscript, uuencode, binhex, yenc, shar, forward, gnatsweb, pgp,
+ diff.  Each of these features can be disabled by add an item into
+ @code{mm-uu-configure-list}.  For example,
+ 
+ @lisp
+ (require 'mm-uu)
+ (add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
+ @end lisp
+ 
+ @table @code
+ @item postscript
+ @findex postscript
+ Postscript file.
+ 
+ @item uu
+ @findex uu
+ Uuencoded file.
+ 
+ @item binhex
+ @findex binhex
+ Binhex encoded file.
+ 
+ @item yenc
+ @findex yenc
+ Yenc encoded file.
+ 
+ @item shar
+ @findex shar
+ Shar archive file.
+ 
+ @item forward
+ @findex forward
+ address@hidden forwarded message.
+ 
+ @item gnatsweb
+ @findex gnatsweb
+ Gnatsweb attachment.
+ 
+ @item pgp-signed
+ @findex pgp-signed
+ @acronym{PGP} signed clear text.
+ 
+ @item pgp-encrypted
+ @findex pgp-encrypted
+ @acronym{PGP} encrypted clear text.
+ 
+ @item pgp-key
+ @findex pgp-key
+ @acronym{PGP} public keys.
+ 
+ @item emacs-sources
+ @findex emacs-sources
+ @vindex mm-uu-emacs-sources-regexp
+ Emacs source code.  This item works only in the groups matching
+ @code{mm-uu-emacs-sources-regexp}.
+ 
+ @item diff
+ @vindex diff
+ @vindex mm-uu-diff-groups-regexp
+ Patches.  This is intended for groups where diffs of committed files
+ are automatically sent to.  It only works in groups matching
+ @code{mm-uu-diff-groups-regexp}.
+ 
+ @end table
+ 
+ @node Handles
+ @section Handles
+ 
+ A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
+ component.
+ 
+ The following macros can be used to access elements in a handle:
+ 
+ @table @code
+ @item mm-handle-buffer
+ @findex mm-handle-buffer
+ Return the buffer that holds the contents of the undecoded @acronym{MIME}
+ part.
+ 
+ @item mm-handle-type
+ @findex mm-handle-type
+ Return the parsed @code{Content-Type} of the part.
+ 
+ @item mm-handle-encoding
+ @findex mm-handle-encoding
+ Return the @code{Content-Transfer-Encoding} of the part.
+ 
+ @item mm-handle-undisplayer
+ @findex mm-handle-undisplayer
+ Return the object that can be used to remove the displayed part (if it
+ has been displayed).
+ 
+ @item mm-handle-set-undisplayer
+ @findex mm-handle-set-undisplayer
+ Set the undisplayer object.
+ 
+ @item mm-handle-disposition
+ @findex mm-handle-disposition
+ Return the parsed @code{Content-Disposition} of the part.
+ 
+ @item mm-handle-disposition
+ @findex mm-handle-disposition
+ Return the description of the part.
+ 
+ @item mm-get-content-id
+ Returns the handle(s) referred to by @code{Content-ID}.
+ 
+ @end table
+ 
+ 
+ @node Display
+ @section Display
+ 
+ Functions for displaying, removing and saving.
+ 
+ @table @code
+ @item mm-display-part
+ @findex mm-display-part
+ Display the part.
+ 
+ @item mm-remove-part
+ @findex mm-remove-part
+ Remove the part (if it has been displayed).
+ 
+ @item mm-inlinable-p
+ @findex mm-inlinable-p
+ Say whether a @acronym{MIME} type can be displayed inline.
+ 
+ @item mm-automatic-display-p
+ @findex mm-automatic-display-p
+ Say whether a @acronym{MIME} type should be displayed automatically.
+ 
+ @item mm-destroy-part
+ @findex mm-destroy-part
+ Free all resources occupied by a part.
+ 
+ @item mm-save-part
+ @findex mm-save-part
+ Offer to save the part in a file.
+ 
+ @item mm-pipe-part
+ @findex mm-pipe-part
+ Offer to pipe the part to some process.
+ 
+ @item mm-interactively-view-part
+ @findex mm-interactively-view-part
+ Prompt for a mailcap method to use to view the part.
+ 
+ @end table
+ 
+ 
+ @node Display Customization
+ @section Display Customization
+ 
+ @table @code
+ 
+ @item mm-inline-media-tests
+ @vindex mm-inline-media-tests
+ This is an alist where the key is a @acronym{MIME} type, the second element
+ is a function to display the part @dfn{inline} (i.e., inside Emacs), and
+ the third element is a form to be @code{eval}ed to say whether the part
+ can be displayed inline.
+ 
+ This variable specifies whether a part @emph{can} be displayed inline,
+ and, if so, how to do it.  It does not say whether parts are
+ @emph{actually} displayed inline.
+ 
+ @item mm-inlined-types
+ @vindex mm-inlined-types
+ This, on the other hand, says what types are to be displayed inline, if
+ they satisfy the conditions set by the variable above.  It's a list of
+ @acronym{MIME} media types.
+ 
+ @item mm-automatic-display
+ @vindex mm-automatic-display
+ This is a list of types that are to be displayed ``automatically'', but
+ only if the above variable allows it.  That is, only inlinable parts can
+ be displayed automatically.
+ 
+ @item mm-automatic-external-display
+ @vindex mm-automatic-external-display
+ This is a list of types that will be displayed automatically in an
+ external viewer.
+ 
+ @item mm-keep-viewer-alive-types
+ @vindex mm-keep-viewer-alive-types
+ This is a list of media types for which the external viewer will not
+ be killed when selecting a different article.
+ 
+ @item mm-attachment-override-types
+ @vindex mm-attachment-override-types
+ Some @acronym{MIME} agents create parts that have a content-disposition of
+ @samp{attachment}.  This variable allows overriding that disposition and
+ displaying the part inline.  (Note that the disposition is only
+ overridden if we are able to, and want to, display the part inline.)
+ 
+ @item mm-discouraged-alternatives
+ @vindex mm-discouraged-alternatives
+ List of @acronym{MIME} types that are discouraged when viewing
+ @samp{multipart/alternative}.  Viewing agents are supposed to view the
+ last possible part of a message, as that is supposed to be the richest.
+ However, users may prefer other types instead, and this list says what
+ types are most unwanted.  If, for instance, @samp{text/html} parts are
+ very unwanted, and @samp{text/richtext} parts are somewhat unwanted,
+ you could say something like:
+ 
+ @lisp
+ (setq mm-discouraged-alternatives
+       '("text/html" "text/richtext")
+       mm-automatic-display
+       (remove "text/html" mm-automatic-display))
+ @end lisp
+ 
+ @item mm-inline-large-images
+ @vindex mm-inline-large-images
+ When displaying inline images that are larger than the window, XEmacs
+ does not enable scrolling, which means that you cannot see the whole
+ image.  To prevent this, the library tries to determine the image size
+ before displaying it inline, and if it doesn't fit the window, the
+ library will display it externally (e.g. with @samp{ImageMagick} or
+ @samp{xv}).  Setting this variable to @code{t} disables this check and
+ makes the library display all inline images as inline, regardless of
+ their size.
+ 
+ @item mm-inline-override-types
+ @vindex mm-inline-override-types
+ @code{mm-inlined-types} may include regular expressions, for example to
+ specify that all @samp{text/.*} parts be displayed inline.  If a user
+ prefers to have a type that matches such a regular expression be treated
+ as an attachment, that can be accomplished by setting this variable to a
+ list containing that type.  For example assuming @code{mm-inlined-types}
+ includes @samp{text/.*}, then including @samp{text/html} in this
+ variable will cause @samp{text/html} parts to be treated as attachments.
+ 
+ @item mm-text-html-renderer
+ @vindex mm-text-html-renderer
+ This selects the function used to render @acronym{HTML}.  The predefined
+ renderers are selected by the symbols @code{w3},
+ @address@hidden @uref{http://emacs-w3m.namazu.org/} for more
+ information about emacs-w3m}, @code{links}, @code{lynx},
+ @code{w3m-standalone} or @code{html2text}.  If @code{nil} use an
+ external viewer.  You can also specify a function, which will be
+ called with a @acronym{MIME} handle as the argument.
+ 
+ @item mm-inline-text-html-with-images
+ @vindex mm-inline-text-html-with-images
+ Some @acronym{HTML} mails might have the trick of spammers using
+ @samp{<img>} tags.  It is likely to be intended to verify whether you
+ have read the mail.  You can prevent your personal informations from
+ leaking by setting this option to @code{nil} (which is the default).
+ It is currently ignored by Emacs/w3.  For emacs-w3m, you may use the
+ command @kbd{t} on the image anchor to show an image even if it is
+ @address@hidden command @kbd{T} will load all images.  If you
+ have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
+ or @kbd{I} instead.}
+ 
+ @item mm-w3m-safe-url-regexp
+ @vindex mm-w3m-safe-url-regexp
+ A regular expression that matches safe URL names, i.e. URLs that are
+ unlikely to leak personal information when rendering @acronym{HTML}
+ email (the default value is @samp{\\`cid:}).  If @code{nil} consider
+ all URLs safe.
+ 
+ @item mm-inline-text-html-with-w3m-keymap
+ @vindex mm-inline-text-html-with-w3m-keymap
+ You can use emacs-w3m command keys in the inlined text/html part by
+ setting this option to address@hidden  The default value is @code{t}.
+ 
+ @item mm-external-terminal-program
+ @vindex mm-external-terminal-program
+ The program used to start an external terminal.
+ 
+ @item mm-enable-external
+ @vindex mm-enable-external
+ Indicate whether external MIME handlers should be used.
+ 
+ If @code{t}, all defined external MIME handlers are used.  If
+ @code{nil}, files are saved to disk (@code{mailcap-save-binary-file}).
+ If it is the symbol @code{ask}, you are prompted before the external
+ @acronym{MIME} handler is invoked.
+ 
+ When you launch an attachment through mailcap (@pxref{mailcap}) an
+ attempt is made to use a safe viewer with the safest options--this isn't
+ the case if you save it to disk and launch it in a different way
+ (command line or double-clicking).  Anyhow, if you want to be sure not
+ to launch any external programs, set this variable to @code{nil} or
+ @code{ask}.
+ 
+ @end table
+ 
+ @node Files and Directories
+ @section Files and Directories
+ 
+ @table @code
+ 
+ @item mm-default-directory
+ @vindex mm-default-directory
+ The default directory for saving attachments.  If @code{nil} use
+ @code{default-directory}.
+ 
+ @item mm-tmp-directory
+ @vindex mm-tmp-directory
+ Directory for storing temporary files.
+ 
+ @item mm-file-name-rewrite-functions
+ @vindex mm-file-name-rewrite-functions
+ A list of functions used for rewriting file names of @acronym{MIME}
+ parts.  Each function is applied successively to the file name.
+ Ready-made functions include
+ 
+ @table @code
+ @item mm-file-name-delete-control
+ @findex mm-file-name-delete-control
+ Delete all control characters.
+ 
+ @item mm-file-name-delete-gotchas
+ @findex mm-file-name-delete-gotchas
+ Delete characters that could have unintended consequences when used
+ with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
+ @samp{-}, @samp{.} as the first character.
+ 
+ @item mm-file-name-delete-whitespace
+ @findex mm-file-name-delete-whitespace
+ Remove all whitespace.
+ 
+ @item mm-file-name-trim-whitespace
+ @findex mm-file-name-trim-whitespace
+ Remove leading and trailing whitespace.
+ 
+ @item mm-file-name-collapse-whitespace
+ @findex mm-file-name-collapse-whitespace
+ Collapse multiple whitespace characters.
+ 
+ @item mm-file-name-replace-whitespace
+ @findex mm-file-name-replace-whitespace
+ @vindex mm-file-name-replace-whitespace
+ Replace whitespace with underscores.  Set the variable
+ @code{mm-file-name-replace-whitespace} to any other string if you do
+ not like underscores.
+ @end table
+ 
+ The standard Emacs functions @code{capitalize}, @code{downcase},
+ @code{upcase} and @code{upcase-initials} might also prove useful.
+ 
+ @item mm-path-name-rewrite-functions
+ @vindex mm-path-name-rewrite-functions
+ List of functions used for rewriting the full file names of @acronym{MIME}
+ parts.  This is used when viewing parts externally, and is meant for
+ transforming the absolute name so that non-compliant programs can find
+ the file where it's saved.
+ 
+ @end table
+ 
+ @node New Viewers
+ @section New Viewers
+ 
+ Here's an example viewer for displaying @code{text/enriched} inline:
+ 
+ @lisp
+ (defun mm-display-enriched-inline (handle)
+   (let (text)
+     (with-temp-buffer
+       (mm-insert-part handle)
+       (save-window-excursion
+         (enriched-decode (point-min) (point-max))
+         (setq text (buffer-string))))
+     (mm-insert-inline handle text)))
+ @end lisp
+ 
+ We see that the function takes a @acronym{MIME} handle as its parameter.  It
+ then goes to a temporary buffer, inserts the text of the part, does some
+ work on the text, stores the result, goes back to the buffer it was
+ called from and inserts the result.
+ 
+ The two important helper functions here are @code{mm-insert-part} and
+ @code{mm-insert-inline}.  The first function inserts the text of the
+ handle in the current buffer.  It handles charset and/or content
+ transfer decoding.  The second function just inserts whatever text you
+ tell it to insert, but it also sets things up so that the text can be
+ ``undisplayed'' in a convenient manner.
+ 
+ 
+ @node Composing
+ @chapter Composing
+ @cindex Composing
+ @cindex MIME Composing
+ @cindex MML
+ @cindex MIME Meta Language
+ 
+ Creating a @acronym{MIME} message is boring and non-trivial.  Therefore,
+ a library called @code{mml} has been defined that parses a language
+ called @acronym{MML} (@acronym{MIME} Meta Language) and generates
+ @acronym{MIME} messages.
+ 
+ @findex mml-generate-mime
+ The main interface function is @code{mml-generate-mime}.  It will
+ examine the contents of the current (narrowed-to) buffer and return a
+ string containing the @acronym{MIME} message.
+ 
+ @menu
+ * Simple MML Example::             An example @acronym{MML} document.
+ * MML Definition::                 All valid @acronym{MML} elements.
+ * Advanced MML Example::           Another example @acronym{MML} document.
+ * Encoding Customization::         Variables that affect encoding.
+ * Charset Translation::            How charsets are mapped from @sc{mule} to 
@acronym{MIME}.
+ * Conversion::                     Going from @acronym{MIME} to @acronym{MML} 
and vice versa.
+ * Flowed text::                    Soft and hard newlines.
+ @end menu
+ 
+ 
+ @node Simple MML Example
+ @section Simple MML Example
+ 
+ Here's a simple @samp{multipart/alternative}:
+ 
+ @example
+ <#multipart type=alternative>
+ This is a plain text part.
+ <#part type=text/enriched>
+ <center>This is a centered enriched part</center>
+ <#/multipart>
+ @end example
+ 
+ After running this through @code{mml-generate-mime}, we get this:
+ 
+ @example
+ Content-Type: multipart/alternative; boundary="=-=-="
+ 
+ 
+ --=-=-=
+ 
+ 
+ This is a plain text part.
+ 
+ --=-=-=
+ Content-Type: text/enriched
+ 
+ 
+ <center>This is a centered enriched part</center>
+ 
+ --=-=-=--
+ @end example
+ 
+ 
+ @node MML Definition
+ @section MML Definition
+ 
+ The @acronym{MML} language is very simple.  It looks a bit like an SGML
+ application, but it's not.
+ 
+ The main concept of @acronym{MML} is the @dfn{part}.  Each part can be of a
+ different type or use a different charset.  The way to delineate a part
+ is with a @samp{<#part ...>} tag.  Multipart parts can be introduced
+ with the @samp{<#multipart ...>} tag.  Parts are ended by the
+ @samp{<#/part>} or @samp{<#/multipart>} tags.  Parts started with the
+ @samp{<#part ...>} tags are also closed by the next open tag.
+ 
+ There's also the @samp{<#external ...>} tag.  These introduce
+ @samp{external/message-body} parts.
+ 
+ Each tag can contain zero or more parameters on the form
+ @samp{parameter=value}.  The values may be enclosed in quotation marks,
+ but that's not necessary unless the value contains white space.  So
+ @samp{filename=/home/user/#hello$^yes} is perfectly valid.
+ 
+ The following parameters have meaning in @acronym{MML}; parameters that have 
no
+ meaning are ignored.  The @acronym{MML} parameter names are the same as the
+ @acronym{MIME} parameter names; the things in the parentheses say which
+ header it will be used in.
+ 
+ @table @samp
+ @item type
+ The @acronym{MIME} type of the part (@code{Content-Type}).
+ 
+ @item filename
+ Use the contents of the file in the body of the part
+ (@code{Content-Disposition}).
+ 
+ @item charset
+ The contents of the body of the part are to be encoded in the character
+ set specified (@code{Content-Type}). @xref{Charset Translation}.
+ 
+ @item name
+ Might be used to suggest a file name if the part is to be saved
+ to a file (@code{Content-Type}).
+ 
+ @item disposition
+ Valid values are @samp{inline} and @samp{attachment}
+ (@code{Content-Disposition}).
+ 
+ @item encoding
+ Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
+ @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
+ Translation}.
+ 
+ @item description
+ A description of the part (@code{Content-Description}).
+ 
+ @item creation-date
+ RFC822 date when the part was created (@code{Content-Disposition}).
+ 
+ @item modification-date
+ RFC822 date when the part was modified (@code{Content-Disposition}).
+ 
+ @item read-date
+ RFC822 date when the part was read (@code{Content-Disposition}).
+ 
+ @item recipients
+ Who to encrypt/sign the part to.  This field is used to override any
+ auto-detection based on the To/CC headers.
+ 
+ @item sender
+ Identity used to sign the part.  This field is used to override the
+ default key used.
+ 
+ @item size
+ The size (in octets) of the part (@code{Content-Disposition}).
+ 
+ @item sign
+ What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
+ or @code{pgpmime})
+ 
+ @item encrypt
+ What technology to encrypt this @acronym{MML} part with (@code{smime},
+ @code{pgp} or @code{pgpmime})
+ 
+ @end table
+ 
+ Parameters for @samp{text/plain}:
+ 
+ @table @samp
+ @item format
+ Formatting parameter for the text, valid values include @samp{fixed}
+ (the default) and @samp{flowed}.  Normally you do not specify this
+ manually, since it requires the textual body to be formatted in a
+ special way described in RFC 2646.  @xref{Flowed text}.
+ @end table
+ 
+ Parameters for @samp{application/octet-stream}:
+ 
+ @table @samp
+ @item type
+ Type of the part; informal---meant for human readers
+ (@code{Content-Type}).
+ @end table
+ 
+ Parameters for @samp{message/external-body}:
+ 
+ @table @samp
+ @item access-type
+ A word indicating the supported access mechanism by which the file may
+ be obtained.  Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
+ @samp{localfile}, and @samp{mailserver}.  (@code{Content-Type}.)
+ 
+ @item expiration
+ The RFC822 date after which the file may no longer be fetched.
+ (@code{Content-Type}.)
+ 
+ @item size
+ The size (in octets) of the file.  (@code{Content-Type}.)
+ 
+ @item permission
+ Valid values are @samp{read} and @samp{read-write}
+ (@code{Content-Type}).
+ 
+ @end table
+ 
+ Parameters for @samp{sign=smime}:
+ 
+ @table @samp
+ 
+ @item keyfile
+ File containing key and certificate for signer.
+ 
+ @end table
+ 
+ Parameters for @samp{encrypt=smime}:
+ 
+ @table @samp
+ 
+ @item certfile
+ File containing certificate for recipient.
+ 
+ @end table
+ 
+ 
+ @node Advanced MML Example
+ @section Advanced MML Example
+ 
+ Here's a complex multipart message.  It's a @samp{multipart/mixed} that
+ contains many parts, one of which is a @samp{multipart/alternative}.
+ 
+ @example
+ <#multipart type=mixed>
+ <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
+ <#multipart type=alternative>
+ This is a plain text part.
+ <#part type=text/enriched name=enriched.txt>
+ <center>This is a centered enriched part</center>
+ <#/multipart>
+ This is a new plain text part.
+ <#part disposition=attachment>
+ This plain text part is an attachment.
+ <#/multipart>
+ @end example
+ 
+ And this is the resulting @acronym{MIME} message:
+ 
+ @example
+ Content-Type: multipart/mixed; boundary="=-=-="
+ 
+ 
+ --=-=-=
+ 
+ 
+ 
+ --=-=-=
+ Content-Type: image/jpeg;
+  filename="~/rms.jpg"
+ Content-Disposition: inline;
+  filename="~/rms.jpg"
+ Content-Transfer-Encoding: base64
+ 
+ /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
+ Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
+ AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
+ BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
+ RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
+ qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
+ AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
+ AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
+ sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
+ 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
+ 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
+ L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
+ 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
+ tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
+ 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
+ pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
+ jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
+ 
+ --=-=-=
+ Content-Type: multipart/alternative; boundary="==-=-="
+ 
+ 
+ --==-=-=
+ 
+ 
+ This is a plain text part.
+ 
+ --==-=-=
+ Content-Type: text/enriched;
+  name="enriched.txt"
+ 
+ 
+ <center>This is a centered enriched part</center>
+ 
+ --==-=-=--
+ 
+ --=-=-=
+ 
+ This is a new plain text part.
+ 
+ --=-=-=
+ Content-Disposition: attachment
+ 
+ 
+ This plain text part is an attachment.
+ 
+ --=-=-=--
+ @end example
+ 
+ @node Encoding Customization
+ @section Encoding Customization
+ 
+ @table @code
+ 
+ @item mm-body-charset-encoding-alist
+ @vindex mm-body-charset-encoding-alist
+ Mapping from @acronym{MIME} charset to encoding to use.  This variable is
+ usually used except, e.g., when other requirements force a specific
+ encoding (digitally signed messages require 7bit encodings).  The
+ default is 
+ 
+ @lisp
+ ((iso-2022-jp . 7bit)
+  (iso-2022-jp-2 . 7bit)
+  (utf-16 . base64)
+  (utf-16be . base64)
+  (utf-16le . base64))
+ @end lisp
+ 
+ As an example, if you do not want to have ISO-8859-1 characters
+ quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
+ this variable.  You can override this setting on a per-message basis
+ by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
+ 
+ @item mm-coding-system-priorities
+ @vindex mm-coding-system-priorities
+ Prioritize coding systems to use for outgoing messages.  The default
+ is @code{nil}, which means to use the defaults in Emacs.  It is a list of
+ coding system symbols (aliases of coding systems does not work, use
+ @kbd{M-x describe-coding-system} to make sure you are not specifying
+ an alias in this variable).  For example, if you have configured Emacs
+ to prefer UTF-8, but wish that outgoing messages should be sent in
+ ISO-8859-1 if possible, you can set this variable to
+ @code{(iso-latin-1)}.  You can override this setting on a per-message
+ basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
+ 
+ @item mm-content-transfer-encoding-defaults
+ @vindex mm-content-transfer-encoding-defaults
+ Mapping from @acronym{MIME} types to encoding to use.  This variable is 
usually
+ used except, e.g., when other requirements force a safer encoding
+ (digitally signed messages require 7bit encoding).  Besides the normal
+ @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
+ each case the most efficient of quoted-printable and base64 should be
+ used.  You can override this setting on a per-message basis by using
+ the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
+ 
+ @item mm-use-ultra-safe-encoding
+ @vindex mm-use-ultra-safe-encoding
+ When this is address@hidden, it means that textual parts are encoded as
+ quoted-printable if they contain lines longer than 76 characters or
+ starting with "From " in the body.  Non-7bit encodings (8bit, binary)
+ are generally disallowed.  This reduce the probability that a non-8bit
+ clean MTA or MDA changes the message.  This should never be set
+ directly, but bound by other functions when necessary (e.g., when
+ encoding messages that are to be digitally signed).
+ 
+ @end table
+ 
+ @node Charset Translation
+ @section Charset Translation
+ @cindex charsets
+ 
+ During translation from @acronym{MML} to @acronym{MIME}, for each
+ @acronym{MIME} part which has been composed inside Emacs, an appropriate
+ charset has to be chosen.
+ 
+ @vindex mail-parse-charset
+ If you are running a address@hidden Emacs, this process is simple: If the
+ part contains any address@hidden (8-bit) characters, the @acronym{MIME} 
charset
+ given by @code{mail-parse-charset} (a symbol) is used.  (Never set this
+ variable directly, though.  If you want to change the default charset,
+ please consult the documentation of the package which you use to process
+ @acronym{MIME} messages.
+ @xref{Various Message Variables, , Various Message Variables, message,
+       Message Manual}, for example.)
+ If there are only @acronym{ASCII} characters, the @acronym{MIME} charset 
US-ASCII is
+ used, of course.
+ 
+ @cindex MULE
+ @cindex UTF-8
+ @cindex Unicode
+ @vindex mm-mime-mule-charset-alist
+ Things are slightly more complicated when running Emacs with @sc{mule}
+ support.  In this case, a list of the @sc{mule} charsets used in the
+ part is obtained, and the @sc{mule} charsets are translated to @acronym{MIME}
+ charsets by consulting the variable @code{mm-mime-mule-charset-alist}.
+ If this results in a single @acronym{MIME} charset, this is used to encode
+ the part.  But if the resulting list of @acronym{MIME} charsets contains more
+ than one element, two things can happen: If it is possible to encode the
+ part via UTF-8, this charset is used.  (For this, Emacs must support
+ the @code{utf-8} coding system, and the part must consist entirely of
+ characters which have Unicode counterparts.)  If UTF-8 is not available
+ for some reason, the part is split into several ones, so that each one
+ can be encoded with a single @acronym{MIME} charset.  The part can only be
+ split at line boundaries, though---if more than one @acronym{MIME} charset is
+ required to encode a single line, it is not possible to encode the part.
+ 
+ When running Emacs with @sc{mule} support, the preferences for which
+ coding system to use is inherited from Emacs itself.  This means that
+ if Emacs is set up to prefer UTF-8, it will be used when encoding
+ messages.  You can modify this by altering the
+ @code{mm-coding-system-priorities} variable though (@pxref{Encoding
+ Customization}).
+ 
+ The charset to be used can be overridden by setting the @code{charset}
+ @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
+ 
+ The encoding of characters (quoted-printable, 8bit etc) is orthogonal
+ to the discussion here, and is controlled by the variables
+ @code{mm-body-charset-encoding-alist} and
+ @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
+ Customization}).
+ 
+ @node Conversion
+ @section Conversion
+ 
+ @findex mime-to-mml
+ A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
+ with the @code{mime-to-mml} function.  It works on the message in the
+ current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
+ boundaries.  Non-textual parts do not have their contents in the buffer,
+ but instead have the contents in separate buffers that are referred to
+ from the @acronym{MML} tags.
+ 
+ @findex mml-to-mime
+ An @acronym{MML} message can be converted back to @acronym{MIME} by the
+ @code{mml-to-mime} function.
+ 
+ These functions are in certain senses ``lossy''---you will not get back
+ an identical message if you run @code{mime-to-mml} and then
+ @code{mml-to-mime}.  Not only will trivial things like the order of the
+ headers differ, but the contents of the headers may also be different.
+ For instance, the original message may use base64 encoding on text,
+ while @code{mml-to-mime} may decide to use quoted-printable encoding, and
+ so on.
+ 
+ In essence, however, these two functions should be the inverse of each
+ other.  The resulting contents of the message should remain equivalent,
+ if not identical.
+ 
+ 
+ @node Flowed text
+ @section Flowed text
+ @cindex format=flowed
+ 
+ The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
+ variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
+ emacs, Emacs Manual}) when encoding a message, and the
+ ``format=flowed'' Content-Type parameter when decoding a message.
+ 
+ On encoding text, regardless of @code{use-hard-newlines}, lines
+ terminated by soft newline characters are filled together and wrapped
+ after the column decided by @code{fill-flowed-encode-column}.
+ Quotation marks (matching @samp{^>* ?}) are respected.  The variable
+ controls how the text will look in a client that does not support
+ flowed text, the default is to wrap after 66 characters.  If hard
+ newline characters are not present in the buffer, no flow encoding
+ occurs.
+ 
+ On decoding flowed text, lines with soft newline characters are filled
+ together and wrapped after the column decided by
+ @code{fill-flowed-display-column}.  The default is to wrap after
+ @code{fill-column}.
+ 
+ 
+ 
+ 
+ @node Interface Functions
+ @chapter Interface Functions
+ @cindex interface functions
+ @cindex mail-parse
+ 
+ The @code{mail-parse} library is an abstraction over the actual
+ low-level libraries that are described in the next chapter.
+ 
+ Standards change, and so programs have to change to fit in the new
+ mold.  For instance, RFC2045 describes a syntax for the
+ @code{Content-Type} header that only allows @acronym{ASCII} characters in the
+ parameter list.  RFC2231 expands on RFC2045 syntax to provide a scheme
+ for continuation headers and address@hidden characters.
+ 
+ The traditional way to deal with this is just to update the library
+ functions to parse the new syntax.  However, this is sometimes the wrong
+ thing to do.  In some instances it may be vital to be able to understand
+ both the old syntax as well as the new syntax, and if there is only one
+ library, one must choose between the old version of the library and the
+ new version of the library.
+ 
+ The Emacs @acronym{MIME} library takes a different tack.  It defines a
+ series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
+ and so on) that parses strictly according to the corresponding
+ standard.  However, normal programs would not use the functions
+ provided by these libraries directly, but instead use the functions
+ provided by the @code{mail-parse} library.  The functions in this
+ library are just aliases to the corresponding functions in the latest
+ low-level libraries.  Using this scheme, programs get a consistent
+ interface they can use, and library developers are free to create
+ write code that handles new standards.
+ 
+ The following functions are defined by this library:
+ 
+ @table @code
+ @item mail-header-parse-content-type
+ @findex mail-header-parse-content-type
+ Parse a @code{Content-Type} header and return a list on the following
+ format:
+ 
+ @lisp
+ ("type/subtype"
+  (attribute1 . value1)
+  (attribute2 . value2)
+  ...)
+ @end lisp
+ 
+ Here's an example:
+ 
+ @example
+ (mail-header-parse-content-type
+  "image/gif; name=\"b980912.gif\"")
+ @result{} ("image/gif" (name . "b980912.gif"))
+ @end example
+ 
+ @item mail-header-parse-content-disposition
+ @findex mail-header-parse-content-disposition
+ Parse a @code{Content-Disposition} header and return a list on the same
+ format as the function above.
+ 
+ @item mail-content-type-get
+ @findex mail-content-type-get
+ Takes two parameters---a list on the format above, and an attribute.
+ Returns the value of the attribute.
+ 
+ @example
+ (mail-content-type-get
+  '("image/gif" (name . "b980912.gif")) 'name)
+ @result{} "b980912.gif"
+ @end example
+ 
+ @item mail-header-encode-parameter
+ @findex mail-header-encode-parameter
+ Takes a parameter string and returns an encoded version of the string.
+ This is used for parameters in headers like @code{Content-Type} and
+ @code{Content-Disposition}.
+ 
+ @item mail-header-remove-comments
+ @findex mail-header-remove-comments
+ Return a comment-free version of a header.
+ 
+ @example
+ (mail-header-remove-comments
+  "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
+ @result{} "Gnus/5.070027  "
+ @end example
+ 
+ @item mail-header-remove-whitespace
+ @findex mail-header-remove-whitespace
+ Remove linear white space from a header.  Space inside quoted strings
+ and comments is preserved.
+ 
+ @example
+ (mail-header-remove-whitespace
+  "image/gif; name=\"Name with spaces\"")
+ @result{} "image/gif;name=\"Name with spaces\""
+ @end example
+ 
+ @item mail-header-get-comment
+ @findex mail-header-get-comment
+ Return the last comment in a header.
+ 
+ @example
+ (mail-header-get-comment
+  "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
+ @result{} "Finnish Landrace"
+ @end example
+ 
+ @item mail-header-parse-address
+ @findex mail-header-parse-address
+ Parse an address and return a list containing the mailbox and the
+ plaintext name.
+ 
+ @example
+ (mail-header-parse-address
+  "Hrvoje Niksic <hniksic@@srce.hr>")
+ @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
+ @end example
+ 
+ @item mail-header-parse-addresses
+ @findex mail-header-parse-addresses
+ Parse a string with list of addresses and return a list of elements like
+ the one described above.
+ 
+ @example
+ (mail-header-parse-addresses
+  "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
+ @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
+      ("sb@@metis.no" . "Steinar Bang"))
+ @end example
+ 
+ @item mail-header-parse-date
+ @findex mail-header-parse-date
+ Parse a date string and return an Emacs time structure.
+ 
+ @item mail-narrow-to-head
+ @findex mail-narrow-to-head
+ Narrow the buffer to the header section of the buffer.  Point is placed
+ at the beginning of the narrowed buffer.
+ 
+ @item mail-header-narrow-to-field
+ @findex mail-header-narrow-to-field
+ Narrow the buffer to the header under point.  Understands continuation
+ headers.
+ 
+ @item mail-header-fold-field
+ @findex mail-header-fold-field
+ Fold the header under point.
+ 
+ @item mail-header-unfold-field
+ @findex mail-header-unfold-field
+ Unfold the header under point.
+ 
+ @item mail-header-field-value
+ @findex mail-header-field-value
+ Return the value of the field under point.
+ 
+ @item mail-encode-encoded-word-region
+ @findex mail-encode-encoded-word-region
+ Encode the address@hidden words in the region.  For instance,
+ @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
+ 
+ @item mail-encode-encoded-word-buffer
+ @findex mail-encode-encoded-word-buffer
+ Encode the address@hidden words in the current buffer.  This function is
+ meant to be called narrowed to the headers of a message.
+ 
+ @item mail-encode-encoded-word-string
+ @findex mail-encode-encoded-word-string
+ Encode the words that need encoding in a string, and return the result.
+ 
+ @example
+ (mail-encode-encoded-word-string
+  "This is naïve, baby")
+ @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
+ @end example
+ 
+ @item mail-decode-encoded-word-region
+ @findex mail-decode-encoded-word-region
+ Decode the encoded words in the region.
+ 
+ @item mail-decode-encoded-word-string
+ @findex mail-decode-encoded-word-string
+ Decode the encoded words in the string and return the result.
+ 
+ @example
+ (mail-decode-encoded-word-string
+  "This is =?iso-8859-1?q?na=EFve,?= baby")
+ @result{} "This is naïve, baby"
+ @end example
+ 
+ @end table
+ 
+ Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
+ @code{rfc2047}, @code{rfc2045} and @code{rfc2231}.  These are documented
+ in the subsequent sections.
+ 
+ 
+ 
+ @node Basic Functions
+ @chapter Basic Functions
+ 
+ This chapter describes the basic, ground-level functions for parsing and
+ handling.  Covered here is parsing @code{From} lines, removing comments
+ from header lines, decoding encoded words, parsing date headers and so
+ on.  High-level functionality is dealt with in the next chapter
+ (@pxref{Decoding and Viewing}).
+ 
+ @menu
+ * rfc2045::      Encoding @code{Content-Type} headers.
+ * rfc2231::      Parsing @code{Content-Type} headers.
+ * ietf-drums::   Handling mail headers defined by RFC822bis.
+ * rfc2047::      En/decoding encoded words in headers.
+ * time-date::    Functions for parsing dates and manipulating time.
+ * qp::           Quoted-Printable en/decoding.
+ * base64::       Base64 en/decoding.
+ * binhex::       Binhex decoding.
+ * uudecode::     Uuencode decoding.
+ * yenc::         Yenc decoding.
+ * rfc1843::      Decoding HZ-encoded text.
+ * mailcap::      How parts are displayed is specified by the @file{.mailcap} 
file
+ @end menu
+ 
+ 
+ @node rfc2045
+ @section rfc2045
+ 
+ RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
+ imagine that there would be a lot to implement.  But there isn't, since
+ most of the implementation details are delegated to the subsequent
+ RFCs.
+ 
+ So @file{rfc2045.el} has only a single function:
+ 
+ @table @code
+ @item rfc2045-encode-string
+ @findex rfc2045-encode-string
+ Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
+ @var{value} will be quoted if there are non-safe characters in it.
+ @end table
+ 
+ 
+ @node rfc2231
+ @section rfc2231
+ 
+ RFC2231 defines a syntax for the @code{Content-Type} and
+ @code{Content-Disposition} headers.  Its snappy name is @dfn{MIME
+ Parameter Value and Encoded Word Extensions: Character Sets, Languages,
+ and Continuations}.
+ 
+ In short, these headers look something like this:
+ 
+ @example
+ Content-Type: application/x-stuff;
+  title*0*=us-ascii'en'This%20is%20even%20more%20;
+  title*1*=%2A%2A%2Afun%2A%2A%2A%20;
+  title*2="isn't it!"
+ @end example
+ 
+ They usually aren't this bad, though.
+ 
+ The following functions are defined by this library:
+ 
+ @table @code
+ @item rfc2231-parse-string
+ @findex rfc2231-parse-string
+ Parse a @code{Content-Type} header and return a list describing its
+ elements.
+ 
+ @example
+ (rfc2231-parse-string
+  "application/x-stuff;
+  title*0*=us-ascii'en'This%20is%20even%20more%20;
+  title*1*=%2A%2A%2Afun%2A%2A%2A%20;
+  title*2=\"isn't it!\"")
+ @result{} ("application/x-stuff"
+     (title . "This is even more ***fun*** isn't it!"))
+ @end example
+ 
+ @item rfc2231-get-value
+ @findex rfc2231-get-value
+ Takes one of the lists on the format above and returns
+ the value of the specified attribute.
+ 
+ @item rfc2231-encode-string
+ @findex rfc2231-encode-string
+ Encode a parameter in headers likes @code{Content-Type} and
+ @code{Content-Disposition}.
+ 
+ @end table
+ 
+ 
+ @node ietf-drums
+ @section ietf-drums
+ 
+ @dfn{drums} is an IETF working group that is working on the replacement
+ for RFC822.
+ 
+ The functions provided by this library include:
+ 
+ @table @code
+ @item ietf-drums-remove-comments
+ @findex ietf-drums-remove-comments
+ Remove the comments from the argument and return the results.
+ 
+ @item ietf-drums-remove-whitespace
+ @findex ietf-drums-remove-whitespace
+ Remove linear white space from the string and return the results.
+ Spaces inside quoted strings and comments are left untouched.
+ 
+ @item ietf-drums-get-comment
+ @findex ietf-drums-get-comment
+ Return the last most comment from the string.
+ 
+ @item ietf-drums-parse-address
+ @findex ietf-drums-parse-address
+ Parse an address string and return a list that contains the mailbox and
+ the plain text name.
+ 
+ @item ietf-drums-parse-addresses
+ @findex ietf-drums-parse-addresses
+ Parse a string that contains any number of comma-separated addresses and
+ return a list that contains mailbox/plain text pairs.
+ 
+ @item ietf-drums-parse-date
+ @findex ietf-drums-parse-date
+ Parse a date string and return an Emacs time structure.
+ 
+ @item ietf-drums-narrow-to-header
+ @findex ietf-drums-narrow-to-header
+ Narrow the buffer to the header section of the current buffer.
+ 
+ @end table
+ 
+ 
+ @node rfc2047
+ @section rfc2047
+ 
+ RFC2047 (Message Header Extensions for address@hidden Text) specifies how
+ address@hidden text in headers are to be encoded.  This is actually rather
+ complicated, so a number of variables are necessary to tweak what this
+ library does.
+ 
+ The following variables are tweakable:
+ 
+ @table @code
+ @item rfc2047-default-charset
+ @vindex rfc2047-default-charset
+ Characters in this charset should not be decoded by this library.
+ This defaults to @code{iso-8859-1}.
+ 
+ @item rfc2047-header-encoding-alist
+ @vindex rfc2047-header-encoding-alist
+ This is an alist of header / encoding-type pairs.  Its main purpose is
+ to prevent encoding of certain headers.
+ 
+ The keys can either be header regexps, or @code{t}.
+ 
+ The values can be either @code{nil}, in which case the header(s) in
+ question won't be encoded, or @code{mime}, which means that they will be
+ encoded.
+ 
+ @item rfc2047-charset-encoding-alist
+ @vindex rfc2047-charset-encoding-alist
+ RFC2047 specifies two forms of address@hidden (a
+ Quoted-Printable-like encoding) and @code{B} (base64).  This alist
+ specifies which charset should use which encoding.
+ 
+ @item rfc2047-encoding-function-alist
+ @vindex rfc2047-encoding-function-alist
+ This is an alist of encoding / function pairs.  The encodings are
+ @code{Q}, @code{B} and @code{nil}.
+ 
+ @item rfc2047-q-encoding-alist
+ @vindex rfc2047-q-encoding-alist
+ The @code{Q} encoding isn't quite the same for all headers.  Some
+ headers allow a narrower range of characters, and that is what this
+ variable is for.  It's an alist of header regexps / allowable character
+ ranges.
+ 
+ @item rfc2047-encoded-word-regexp
+ @vindex rfc2047-encoded-word-regexp
+ When decoding words, this library looks for matches to this regexp.
+ 
+ @end table
+ 
+ Those were the variables, and these are this functions:
+ 
+ @table @code
+ @item rfc2047-narrow-to-field
+ @findex rfc2047-narrow-to-field
+ Narrow the buffer to the header on the current line.
+ 
+ @item rfc2047-encode-message-header
+ @findex rfc2047-encode-message-header
+ Should be called narrowed to the header of a message.  Encodes according
+ to @code{rfc2047-header-encoding-alist}.
+ 
+ @item rfc2047-encode-region
+ @findex rfc2047-encode-region
+ Encodes all encodable words in the region specified.
+ 
+ @item rfc2047-encode-string
+ @findex rfc2047-encode-string
+ Encode a string and return the results.
+ 
+ @item rfc2047-decode-region
+ @findex rfc2047-decode-region
+ Decode the encoded words in the region.
+ 
+ @item rfc2047-decode-string
+ @findex rfc2047-decode-string
+ Decode a string and return the results.
+ 
+ @end table
+ 
+ 
+ @node time-date
+ @section time-date
+ 
+ While not really a part of the @acronym{MIME} library, it is convenient to
+ document this library here.  It deals with parsing @code{Date} headers
+ and manipulating time.  (Not by using tesseracts, though, I'm sorry to
+ say.)
+ 
+ These functions convert between five formats: A date string, an Emacs
+ time structure, a decoded time list, a second number, and a day number.
+ 
+ Here's a bunch of time/date/second/day examples:
+ 
+ @example
+ (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
+ @result{} (54 21 12 12 9 1998 6 nil 7200)
+ 
+ (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
+ @result{} (13818 19266)
+ 
+ (time-to-seconds '(13818 19266))
+ @result{} 905595714.0
+ 
+ (seconds-to-time 905595714.0)
+ @result{} (13818 19266 0)
+ 
+ (time-to-days '(13818 19266))
+ @result{} 729644
+ 
+ (days-to-time 729644)
+ @result{} (961933 65536)
+ 
+ (time-since '(13818 19266))
+ @result{} (0 430)
+ 
+ (time-less-p '(13818 19266) '(13818 19145))
+ @result{} nil
+ 
+ (subtract-time '(13818 19266) '(13818 19145))
+ @result{} (0 121)
+ 
+ (days-between "Sat Sep 12 12:21:54 1998 +0200"
+               "Sat Sep 07 12:21:54 1998 +0200")
+ @result{} 5
+ 
+ (date-leap-year-p 2000)
+ @result{} t
+ 
+ (time-to-day-in-year '(13818 19266))
+ @result{} 255
+ 
+ (time-to-number-of-days
+  (time-since
+   (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
+ @result{} 4.146122685185185
+ @end example
+ 
+ And finally, we have @code{safe-date-to-time}, which does the same as
+ @code{date-to-time}, but returns a zero time if the date is
+ syntactically malformed.
+ 
+ The five data representations used are the following:
+ 
+ @table @var
+ @item date
+ An RFC822 (or similar) date string.  For instance: @code{"Sat Sep 12
+ 12:21:54 1998 +0200"}.
+ 
+ @item time
+ An internal Emacs time.  For instance: @code{(13818 26466)}.
+ 
+ @item seconds
+ A floating point representation of the internal Emacs time.  For
+ instance: @code{905595714.0}.
+ 
+ @item days
+ An integer number representing the number of days since 00000101.  For
+ instance: @code{729644}.
+ 
+ @item decoded time
+ A list of decoded time.  For instance: @code{(54 21 12 12 9 1998 6 t
+ 7200)}.
+ @end table
+ 
+ All the examples above represent the same moment.
+ 
+ These are the functions available:
+ 
+ @table @code
+ @item date-to-time
+ Take a date and return a time.
+ 
+ @item time-to-seconds
+ Take a time and return seconds.
+ 
+ @item seconds-to-time
+ Take seconds and return a time.
+ 
+ @item time-to-days
+ Take a time and return days.
+ 
+ @item days-to-time
+ Take days and return a time.
+ 
+ @item date-to-day
+ Take a date and return days.
+ 
+ @item time-to-number-of-days
+ Take a time and return the number of days that represents.
+ 
+ @item safe-date-to-time
+ Take a date and return a time.  If the date is not syntactically valid,
+ return a ``zero'' date.
+ 
+ @item time-less-p
+ Take two times and say whether the first time is less (i. e., earlier)
+ than the second time.
+ 
+ @item time-since
+ Take a time and return a time saying how long it was since that time.
+ 
+ @item subtract-time
+ Take two times and subtract the second from the first.  I. e., return
+ the time between the two times.
+ 
+ @item days-between
+ Take two days and return the number of days between those two days.
+ 
+ @item date-leap-year-p
+ Take a year number and say whether it's a leap year.
+ 
+ @item time-to-day-in-year
+ Take a time and return the day number within the year that the time is
+ in.
+ 
+ @end table
+ 
+ 
+ @node qp
+ @section qp
+ 
+ This library deals with decoding and encoding Quoted-Printable text.
+ 
+ Very briefly explained, qp encoding means translating all 8-bit
+ characters (and lots of control characters) into things that look like
+ @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
+ string.
+ 
+ The following functions are defined by the library:
+ 
+ @table @code
+ @item quoted-printable-decode-region
+ @findex quoted-printable-decode-region
+ QP-decode all the encoded text in the specified region.
+ 
+ @item quoted-printable-decode-string
+ @findex quoted-printable-decode-string
+ Decode the QP-encoded text in a string and return the results.
+ 
+ @item quoted-printable-encode-region
+ @findex quoted-printable-encode-region
+ QP-encode all the encodable characters in the specified region.  The third
+ optional parameter @var{fold} specifies whether to fold long lines.
+ (Long here means 72.)
+ 
+ @item quoted-printable-encode-string
+ @findex quoted-printable-encode-string
+ QP-encode all the encodable characters in a string and return the
+ results.
+ 
+ @end table
+ 
+ 
+ @node base64
+ @section base64
+ @cindex base64
+ 
+ Base64 is an encoding that encodes three bytes into four characters,
+ thereby increasing the size by about 33%.  The alphabet used for
+ encoding is very resistant to mangling during transit.
+ 
+ The following functions are defined by this library:
+ 
+ @table @code
+ @item base64-encode-region
+ @findex base64-encode-region
+ base64 encode the selected region.  Return the length of the encoded
+ text.  Optional third argument @var{no-line-break} means do not break
+ long lines into shorter lines.
+ 
+ @item base64-encode-string
+ @findex base64-encode-string
+ base64 encode a string and return the result.
+ 
+ @item base64-decode-region
+ @findex base64-decode-region
+ base64 decode the selected region.  Return the length of the decoded
+ text.  If the region can't be decoded, return @code{nil} and don't
+ modify the buffer.
+ 
+ @item base64-decode-string
+ @findex base64-decode-string
+ base64 decode a string and return the result.  If the string can't be
+ decoded, @code{nil} is returned.
+ 
+ @end table
+ 
+ 
+ @node binhex
+ @section binhex
+ @cindex binhex
+ @cindex Apple
+ @cindex Macintosh
+ 
+ @code{binhex} is an encoding that originated in Macintosh environments.
+ The following function is supplied to deal with these:
+ 
+ @table @code
+ @item binhex-decode-region
+ @findex binhex-decode-region
+ Decode the encoded text in the region.  If given a third parameter, only
+ decode the @code{binhex} header and return the filename.
+ 
+ @end table
+ 
+ @node uudecode
+ @section uudecode
+ @cindex uuencode
+ @cindex uudecode
+ 
+ @code{uuencode} is probably still the most popular encoding of binaries
+ used on Usenet, although @code{base64} rules the mail world.
+ 
+ The following function is supplied by this package:
+ 
+ @table @code
+ @item uudecode-decode-region
+ @findex uudecode-decode-region
+ Decode the text in the region.
+ @end table
+ 
+ 
+ @node yenc
+ @section yenc
+ @cindex yenc
+ 
+ @code{yenc} is used for encoding binaries on Usenet.  The following
+ function is supplied by this package:
+ 
+ @table @code
+ @item yenc-decode-region
+ @findex yenc-decode-region
+ Decode the encoded text in the region.
+ 
+ @end table
+ 
+ 
+ @node rfc1843
+ @section rfc1843
+ @cindex rfc1843
+ @cindex HZ
+ @cindex Chinese
+ 
+ RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. 
 In
+ essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
+ 
+ @example
+ This sentence is in @acronym{ASCII}.
+ The next sentence is in address@hidden<:Ky2;address@hidden,NpJ)address@hidden
+ @end example
+ 
+ Simple enough, and widely used in China.
+ 
+ The following functions are available to handle this encoding:
+ 
+ @table @code
+ @item rfc1843-decode-region
+ Decode HZ-encoded text in the region.
+ 
+ @item rfc1843-decode-string
+ Decode a HZ-encoded string and return the result.
+ 
+ @end table
+ 
+ 
+ @node mailcap
+ @section mailcap
+ 
+ The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
+ handlers and describes how elements are supposed to be displayed.
+ Here's an example file:
+ 
+ @example
+ image/*; gimp -8 %s
+ audio/wav; wavplayer %s
+ application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
+ @end example
+ 
+ This says that all image files should be displayed with @code{gimp},
+ that WAVE audio files should be played by @code{wavplayer}, and that
+ MS-WORD files should be inlined by @code{catdoc}.
+ 
+ The @code{mailcap} library parses this file, and provides functions for
+ matching types.
+ 
+ @table @code
+ @item mailcap-mime-data
+ @vindex mailcap-mime-data
+ This variable is an alist of alists containing backup viewing rules.
+ 
+ @end table
+ 
+ Interface functions:
+ 
+ @table @code
+ @item mailcap-parse-mailcaps
+ @findex mailcap-parse-mailcaps
+ Parse the @file{~/.mailcap} file.
+ 
+ @item mailcap-mime-info
+ Takes a @acronym{MIME} type as its argument and returns the matching viewer.
+ 
+ @end table
+ 
+ 
+ 
+ 
+ @node Standards
+ @chapter Standards
+ 
+ The Emacs @acronym{MIME} library implements handling of various elements
+ according to a (somewhat) large number of RFCs, drafts and standards
+ documents.  This chapter lists the relevant ones.  They can all be
+ fetched from @uref{http://quimby.gnus.org/notes/}.
+ 
+ @table @dfn
+ @item RFC822
+ @itemx STD11
+ Standard for the Format of ARPA Internet Text Messages.
+ 
+ @item RFC1036
+ Standard for Interchange of USENET Messages
+ 
+ @item RFC2045
+ Format of Internet Message Bodies
+ 
+ @item RFC2046
+ Media Types
+ 
+ @item RFC2047
+ Message Header Extensions for address@hidden Text
+ 
+ @item RFC2048
+ Registration Procedures
+ 
+ @item RFC2049
+ Conformance Criteria and Examples
+ 
+ @item RFC2231
+ @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
+ Languages, and Continuations
+ 
+ @item RFC1843
+ HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
+ @acronym{ASCII} characters
+ 
+ @item draft-ietf-drums-msg-fmt-05.txt
+ Draft for the successor of RFC822
+ 
+ @item RFC2112
+ The @acronym{MIME} Multipart/Related Content-type
+ 
+ @item RFC1892
+ The Multipart/Report Content Type for the Reporting of Mail System
+ Administrative Messages
+ 
+ @item RFC2183
+ Communicating Presentation Information in Internet Messages: The
+ Content-Disposition Header Field
+ 
+ @item RFC2646
+ Documentation of the text/plain format parameter for flowed text.
+ 
+ @end table
+ 
+ 
+ @node Index
+ @chapter Index
+ @printindex cp
+ 
+ @summarycontents
+ @contents
+ @bye
+ 
+ 
+ @c Local Variables:
+ @c mode: texinfo
+ @c coding: iso-8859-1
+ @c End:
+ 
+ @ignore
+    arch-tag: c7ef2fd0-a91c-4e10-aa52-c1a2b11b1a8d
+ @end ignore