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diff --git a/man/emacs-mime.texi b/man/emacs-mime.texi index bdeea1f4703..f30eec7e0fb 100644 --- a/man/emacs-mime.texi +++ b/man/emacs-mime.texi @@ -1,4 +1,4 @@ -\input texinfo @c -*-mode: texinfo; coding: latin-1 -*- +\input texinfo @setfilename ../info/emacs-mime @settitle Emacs MIME Manual @@ -9,14 +9,15 @@ @copying This file documents the Emacs MIME interface functionality. -Copyright (C) 1998, 1999, 2000, 2002 Free Software Foundation, Inc. +Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 + Free Software Foundation, Inc. @quotation 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 +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. @@ -33,7 +34,7 @@ license to the document, as described in section 6 of the license. @dircategory Emacs @direntry -* MIME: (emacs-mime). Emacs MIME de/composition library. +* Emacs MIME: (emacs-mime). Emacs MIME de/composition library. @end direntry @iftex @finalout @@ -49,857 +50,228 @@ license to the document, as described in section 6 of the license. @insertcopying @end titlepage - @node Top @top Emacs MIME This manual documents the libraries used to compose and display -@sc{mime} messages. +@acronym{MIME} messages. -This is not a manual meant for users; it's a manual directed at people -who want to write functions and commands that manipulate @sc{mime} -elements. +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. -@sc{mime} is short for @dfn{Multipurpose Internet Mail Extensions}. +@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 Non-ASCII Text), RFC2048 (Registration +Header Extensions for Non-@acronym{ASCII} Text), RFC2048 (Registration Procedures), RFC2049 (Conformance Criteria and Examples). It is highly -recommended that anyone who intends writing @sc{mime}-compliant software +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. -* Decoding and Viewing:: A framework for decoding and viewing. -* Composing:: MML; a language for describing MIME parts. * Standards:: A summary of RFCs and working documents used. * Index:: Function and variable index. @end menu -@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 @sc{ascii} characters in the -parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme -for continuation headers and non-@sc{ascii} 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 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: - -@defun mail-header-parse-content-type string -Parse @var{string}, a @code{Content-Type} header, and return a -content-type list in the following format: - -@lisp -("type/subtype" - (attribute1 . value1) - (attribute2 . value2) - @dots{}) -@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 -@end defun - -@defun mail-header-parse-content-disposition string -Parse @var{string}, a @code{Content-Disposition} header, and return a -content-type list in the format above. -@end defun - -@defun mail-content-type-get ct attribute -@findex mail-content-type-get -Returns the value of the given @var{attribute} from the content-type -list @var{ct}. - -@example -(mail-content-type-get - '("image/gif" (name . "b980912.gif")) 'name) -@result{} "b980912.gif" -@end example -@end defun - -@defun mail-header-encode-parameter param value -Takes a parameter string @samp{@var{param}=@var{value}} and returns an -encoded version of it. This is used for parameters in headers like -@samp{Content-Type} and @samp{Content-Disposition}. -@end defun - -@defun mail-header-remove-comments string -Return a comment-free version of @var{string}. - -@example -(mail-header-remove-comments - "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)") -@result{} "Gnus/5.070027 " -@end example -@end defun - -@defun mail-header-remove-whitespace string -Remove linear white space from @var{string}. 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 -@end defun - -@defun mail-header-get-comment string -Return the last comment in @var{string}. - -@example -(mail-header-get-comment - "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)") -@result{} "Finnish Landrace" -@end example -@end defun - - -@defun mail-header-parse-address string -Parse an address string @var{string} 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 -@end defun - -@defun mail-header-parse-addresses string -Parse @var{string} as a 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 -@end defun - -@defun mail-header-parse-date string -Parse a date @var{string} and return an Emacs time structure. -@end defun - -@defun mail-narrow-to-head -Narrow the buffer to the header section of the buffer. Point is placed -at the beginning of the narrowed buffer. -@end defun - -@defun mail-header-narrow-to-field -Narrow the buffer to the header under point. -@end defun - -@defun mail-encode-encoded-word-region start end -Encode the non-@sc{ascii} words in the region @var{start}to @var{end}. For -instance, @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}. -@end defun - -@defun mail-encode-encoded-word-buffer -Encode the non-@sc{ascii} words in the current buffer. This function is -meant to be called with the buffer narrowed to the headers of a message. -@end defun - -@defun mail-encode-encoded-word-string string -Encode the words that need encoding in @var{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 -@end defun - -@defun mail-decode-encoded-word-region start end -Decode the encoded words in the region @var{start}to @var{end}. -@end defun - -@defun mail-decode-encoded-word-string string -Decode the encoded words in @var{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 defun - -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 Decoding and Viewing +@chapter Decoding and Viewing -@node Basic Functions -@chapter Basic Functions +This chapter deals with decoding and viewing @acronym{MIME} messages on a +higher level. -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}). +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 -* 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. -* rfc1843:: Decoding HZ-encoded text. -* mailcap:: How parts are displayed is specified by mailcap files +* Dissection:: Analyzing a @acronym{MIME} message. +* Non-MIME:: Analyzing a non-@acronym{MIME} 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 rfc2045 -@section rfc2045 - -RFC2045 is the ``main'' @sc{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: - -@defun rfc2045-encode-string parameter value -@findex rfc2045-encode-string -Takes a @var{parameter} and a @var{value} and returns a -@samp{@var{param}=@var{value}} string. @var{value} will be quoted if -there are non-safe characters in it. -@end defun - - -@node rfc2231 -@section rfc2231 - -RFC2231 defines a syntax for the @samp{Content-Type} and -@samp{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: - -@defun rfc2231-parse-string string -Parse a @samp{Content-Type} header @var{string} 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 -@end defun - -@defun rfc2231-get-value ct attribute -Takes a list @var{ct} of the format above and returns the value of the -specified @var{attribute}. -@end defun - -@defun rfc2231-encode-string parameter value -Encode the string @samp{@var{parameter}=@var{value}} for inclusion in -headers likes @samp{Content-Type} and @samp{Content-Disposition}. -@end defun - -@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: - -@defun ietf-drums-remove-comments string -Remove the comments from @var{string} and return the result. -@end defun - -@defun ietf-drums-remove-whitespace string -Remove linear white space from @var{string} and return the result. -Spaces inside quoted strings and comments are left untouched. -@end defun - -@defun ietf-drums-get-comment string -Return the last most comment from @var{string}. -@end defun - -@defun ietf-drums-parse-address string -Parse an address @var{string} and return a list of the mailbox and the -plain text name. -@end defun - -@defun ietf-drums-parse-addresses string -Parse @var{string}, containing any number of comma-separated addresses, -and return a list of mailbox/plain text pairs. -@end defun - -@defun ietf-drums-parse-date string -Parse the date @var{string} and return an Emacs time structure. -@end defun - -@defun ietf-drums-narrow-to-header -Narrow the buffer to the header section of the current buffer. -@end defun - - -@node rfc2047 -@section rfc2047 - -RFC2047 (Message Header Extensions for Non-ASCII Text) specifies how -non-@sc{ascii} 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: - -@defvar rfc2047-default-charset -Characters in this charset should not be decoded by this library. -This defaults to @samp{iso-8859-1}. -@end defvar - -@defvar rfc2047-header-encoding-list -This is an alist of header / encoding-type pairs. Its main purpose is -to prevent encoding of certain headers. -@end defvar - -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. - -@defvar rfc2047-charset-encoding-alist -RFC2047 specifies two forms of encoding---@code{Q} (a -Quoted-Printable-like encoding) and @code{B} (base64). This alist -specifies which charset should use which encoding. -@end defvar - -@defvar rfc2047-encoding-function-alist -This is an alist of encoding / function pairs. The encodings are -@code{Q}, @code{B} and @code{nil}. -@end defvar - -@defvar 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 and allowable character -ranges. -@end defvar - -@defvar rfc2047-encoded-word-regexp -When decoding words, this library looks for matches to this regexp. -@end defvar - -Those were the variables, and these are the functions: - -@defun rfc2047-narrow-to-field -Narrow the buffer to the header on the current line. -@end defun - -@defun rfc2047-encode-message-header -Should be called narrowed to the header of a message. Encodes according -to @code{rfc2047-header-encoding-alist}. -@end defun - -@defun rfc2047-encode-region start end -Encodes all encodable words in the region @var{start} to @var{end}. -@end defun - -@defun rfc2047-encode-string string -Encode @var{string} and return the result. -@end defun - -@defun rfc2047-decode-region start end -Decode the encoded words in the region @var{start} to @var{end}. -@end defun - -@defun rfc2047-decode-string string -Decode @var{string} and return the result. -@end defun - - - -@node time-date -@section time-date - -While not really a part of the @sc{mime} library, it is convenient to -document this library here. It deals with parsing @samp{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 number of seconds, and a day number. - -The functions have quite self-explanatory names, so the following just -gives an overview of which functions are available. - -@findex parse-time-string -@findex date-to-time -@findex time-to-seconds -@findex seconds-to-time -@findex time-to-day -@findex days-to-time -@findex time-since -@findex time-less-p -@findex subtract-time -@findex days-between -@findex date-leap-year-p -@findex time-to-day-in-year -@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-day '(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 -@end example - -@findex safe-date-to-time -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. - - - -@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. It is defined in RFC 2045. - -The following functions are defined by the library: - -@deffn Command quoted-printable-decode-region @var{from} @var{to} &optional @var{coding-system} -QP-decode all the encoded text in the region. If @var{coding-system} -is non-nil, decode bytes into characters with that coding-system. It -is probably better not to use @var{coding-system}; instead decode into -a unibyte buffer, decode that appropriately and then interpret it as -multibyte. -@end deffn - -@defun quoted-printable-decode-string @var{string} &optional @var{coding-system} -Return a QP-encoded copy of @var{string}. If @var{coding-system} is -non-nil, decode bytes into characters with that coding-system. -@end defun - -@deffn Command quoted-printable-encode-region @var{from} @var{to} &optional @var{fold} @var{class} -QP-encode all the region. If @var{fold} is non-@var{nil}, fold lines -at 76 characters, as required by the RFC. If @var{class} is -non-@code{nil}, translate the characters not matched by that regexp -class, which should be in the form expected by -@var{skip-chars-forward} and should probably not contain literal -eight-bit characters. Specifying @var{class} makes sense to do extra -encoding in header fields. - -If variable @var{mm-use-ultra-safe-encoding} is defined and -non-@code{nil}, fold lines unconditionally and encode @samp{From } and -@samp{-} at the start of lines.. -@end deffn - -@defun quoted-printable-encode-string string -Return a QP-encoded copy of @var{string}. -@end defun - -@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. @xref{Base -64,,Base 64 Encoding, elisp, The Emacs Lisp Reference Manual}. - -@node binhex -@section binhex -@cindex binhex -@cindex Apple -@cindex Macintosh - -Binhex is an encoding that originated in Macintosh environments. -The following function is supplied to deal with these: - -@defun binhex-decode-region start end &optional header-only -Decode the encoded text in the region @var{start} to @var{end}. If -@var{header-only} is non-@code{nil}, only decode the @samp{binhex} -header and return the file name. -@end defun - - -@node uudecode -@section uudecode -@cindex uuencode -@cindex uudecode - -Uuencoding is probably still the most popular encoding of binaries -used on Usenet, although Base64 rules the mail world. - -The following function is supplied by this package: - -@defun uudecode-decode-region start end &optional file-name -Decode the text in the region @var{start} to @var{end}. If -@var{file-name} is non-@code{nil}, save the result to @var{file-name}. -@end defun - - -@node rfc1843 -@section rfc1843 -@cindex rfc1843 -@cindex HZ -@cindex Chinese - -RFC1843 deals with mixing Chinese and @sc{ascii} characters in messages. In -essence, RFC1843 switches between @sc{ascii} and Chinese by doing this: - -@example -This sentence is in ASCII. -The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye. -@end example - -Simple enough, and widely used in China. - -The following functions are available to handle this encoding: - -@defun rfc1843-decode-region start end -Decode HZ-encoded text in the region @var{start} to @var{end}. -@end defun - -@defun rfc1843-decode-string string -Decode the HZ-encoded @var{string} and return the result. -@end defun - - -@node mailcap -@section mailcap - -As specified by RFC 1524, @sc{mime}-aware message handlers parse -@dfn{mailcap} files from a default list, which can be overridden by the -@code{MAILCAP} environment variable. These describe how elements are -supposed to be displayed. Here's an example file: - -@example -image/*; gimp -8 %s -audio/wav; wavplayer %s -@end example - -This says that all image files should be displayed with @command{gimp}, -and that WAVE audio files should be played by @code{wavplayer}. - -The @code{mailcap} library parses such files, and provides functions for -matching types. - -@defvar mailcap-mime-data -This variable is an alist of alists containing backup viewing rules for -@sc{mime} types. These are overridden by rules for a type found in -mailcap files. The outer alist is keyed on the major content-type and -the inner alists are keyed on the minor content-type (which can be a -regular expression). - -@c Fixme: document this properly! -For example: -@example -(("application" - ("octet-stream" - (viewer . mailcap-save-binary-file) - (non-viewer . t) - (type . "application/octet-stream")) - ("plain" - (viewer . view-mode) - (test fboundp 'view-mode) - (type . "text/plain"))) -@end example -@end defvar +@node Dissection +@section Dissection -@defopt mailcap-default-mime-data -This variable is the default value of @code{mailcap-mime-data}. It -exists to allow setting the value using Custom. It is merged with -values from mailcap files by @code{mailcap-parse-mailcaps}. -@end defopt +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. -Although it is not specified by the RFC, @sc{mime} tools normally use a -common means of associating file extensions with defualt @sc{mime} types -in the absence of other information about the type of a file. The -information is found in per-user files @file{~/.mime.types} and system -@file{mime.types} files found in quasi-standard places. Here is an -example: +@node Non-MIME +@section Non-MIME +@vindex mm-uu-configure-list -@example -application/x-dvi dvi -audio/mpeg mpga mpega mp2 mp3 -image/jpeg jpeg jpg jpe -@end example +Gnus also understands some non-@acronym{MIME} 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 -@defvar mailcap-mime-extensions -This variable is an alist @sc{mime} types keyed by file extensions. -This is overridden by entries found in @file{mime.types} files. -@end defvar +@table @code +@item postscript +@findex postscript +Postscript file. -@defopt mailcap-default-mime-extensions -This variable is the default value of @code{mailcap-mime-extensions}. -It exists to allow setting the value using Custom. It is merged with -values from mailcap files by @code{mailcap-parse-mimetypes}. -@end defopt +@item uu +@findex uu +Uuencoded file. -Interface functions: +@item binhex +@findex binhex +Binhex encoded file. -@defun mailcap-parse-mailcaps &optional path force -Parse all the mailcap files specified in a path string @var{path} and -merge them with the values from @code{mailcap-mime-data}. Components of -@var{path} are separated by the @code{path-separator} character -appropriate for the system. If @var{force} is non-@code{nil}, the files -are re-parsed even if they have been parsed already. If @var{path} is -omitted, use the value of environment variable @code{MAILCAPS} if it is -set; otherwise (on GNU and Unix) use the path defined in RFC 1524, plus -@file{/usr/local/etc/mailcap}. -@end defun - -@defun mailcap-parse-mimetypes &optional path force -Parse all the mimetypes specified in a path string @var{path} -and merge them with the values from @code{mailcap-mime-extensions}. -Components of @var{path} are separated by the @code{path-separator} -character appropriate for the system. If @var{path} is omitted, use the -value of environment variable @code{MIMETYPES} if set; otherwise use a -default path consistent with that used by @code{mailcap-parse-mailcaps}. -If @var{force} is non-@code{nil}, the files are re-parsed even if they -have been parsed already. -@end defun - -@defun mailcap-mime-info string &optional request -Gets the viewer command for content-type @var{string}. @code{nil} is -returned if none is found. Expects @var{string} to be a complete -content-type header line. - -If @var{request} is non-@code{nil} it specifies what information to -return. If it is nil or the empty string, the viewer (second field of -the mailcap entry) will be returned. If it is a string, then the -mailcap field corresponding to that string will be returned -(@samp{print}, @samp{description}, whatever). If it is a number, all -the information for this viewer is returned. If it is @code{all}, then -all possible viewers for this type is returned. -@end defun - -@defun mailcap-mime-types -This function returns a list of all the defined media types. -@end defun - -@defun mailcap-extension-to-mime extension -This function returns the content type defined for a file with the given -@var{extension}. -@end defun +@item yenc +@findex yenc +Yenc encoded file. +@item shar +@findex shar +Shar archive file. -@node Decoding and Viewing -@chapter Decoding and Viewing +@item forward +@findex forward +Non-@acronym{MIME} forwarded message. -This chapter deals with decoding and viewing @sc{mime} messages on a -higher level. +@item gnatsweb +@findex gnatsweb +Gnatsweb attachment. -The main idea is to first analyze a @sc{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. +@item pgp-signed +@findex pgp-signed +@acronym{PGP} signed clear text. -@menu -* Dissection:: Analyzing a @sc{mime} message. -* Handles:: Handle manipulations. -* Display:: Displaying handles. -* Customization:: Variables that affect display. -* New Viewers:: How to write your own viewers. -@end menu +@item pgp-encrypted +@findex pgp-encrypted +@acronym{PGP} encrypted clear text. +@item pgp-key +@findex pgp-key +@acronym{PGP} public keys. -@node Dissection -@section Dissection +@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}. -The @code{mm-dissect-buffer} is the function responsible for dissecting -a @sc{mime} article. If given a multipart message, it will recursively -descend the message, following the structure, and return a tree of -@sc{mime} handles that describes the structure of the message. +@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 @sc{mime} handle is a list that fully describes a @sc{mime} component. +A @acronym{MIME} handle is a list that fully describes a @acronym{MIME} +component. -The following macros can be used to access elements from the -@var{handle} argument: +The following macros can be used to access elements in a handle: -@defmac mm-handle-buffer handle -Return the buffer that holds the contents of the undecoded @sc{mime} +@table @code +@item mm-handle-buffer +@findex mm-handle-buffer +Return the buffer that holds the contents of the undecoded @acronym{MIME} part. -@end defmac -@defmac mm-handle-type handle -Return the parsed @samp{Content-Type} of the part. -@end defmac +@item mm-handle-type +@findex mm-handle-type +Return the parsed @code{Content-Type} of the part. -@defmac mm-handle-encoding handle -Return the @samp{Content-Transfer-Encoding} of the part. -@end defmac +@item mm-handle-encoding +@findex mm-handle-encoding +Return the @code{Content-Transfer-Encoding} of the part. -@defmac mm-handle-undisplayer handle -Return the function that can be used to remove the displayed part (if it +@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). -@end defmac -@defmac mm-handle-set-undisplayer handle function -Set the undisplayer function for the part to function. -@end defmac +@item mm-handle-set-undisplayer +@findex mm-handle-set-undisplayer +Set the undisplayer object. -@defmac mm-handle-disposition -Return the parsed @samp{Content-Disposition} of the part. -@end defmac +@item mm-handle-disposition +@findex mm-handle-disposition +Return the parsed @code{Content-Disposition} of the part. -@defmac mm-handle-disposition +@item mm-handle-disposition +@findex mm-handle-disposition Return the description of the part. -@end defmac -@defmac mm-get-content-id id -Returns the handle(s) referred to by @var{id}, the @samp{Content-ID} of -the part. -@end defmac +@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. In the descriptions -below, `the part' means the @sc{mime} part represented by the -@var{handle} argument. +Functions for displaying, removing and saving. -@defun mm-display-part handle &optional no-default -Display the part. Return @code{nil} if the part is removed, -@code{inline} if it is displayed inline or @code{external} if it is -displayed externally. If @var{no-default} is non-@code{nil}, the part -is not displayed unless the @sc{mime} type of @var{handle} is defined to -be displayed inline or there is an display method defined for it; i.e.@: -no default external method will be used. -@end defun +@table @code +@item mm-display-part +@findex mm-display-part +Display the part. -@defun mm-remove-part handle -Remove the part if it has been displayed. -@end defun +@item mm-remove-part +@findex mm-remove-part +Remove the part (if it has been displayed). -@defun mm-inlinable-p handle -Return non-@code{nil} if the part can be displayed inline. -@end defun +@item mm-inlinable-p +@findex mm-inlinable-p +Say whether a @acronym{MIME} type can be displayed inline. -@defun mm-automatic-display-p handle -Return non-@code{nil} if the user has requested automatic display of the -@sc{mime} type of the part. -@end defun +@item mm-automatic-display-p +@findex mm-automatic-display-p +Say whether a @acronym{MIME} type should be displayed automatically. -@defun mm-destroy-part handle -Free all the resources used by the part. -@end defun +@item mm-destroy-part +@findex mm-destroy-part +Free all resources occupied by a part. -@defun mm-save-part handle -Save the part to a file. The user is prompted for a file name to use. -@end defun +@item mm-save-part +@findex mm-save-part +Offer to save the part in a file. -@defun mm-pipe-part handle -Pipe the part through a shell command. The user is prompted for the -command to use. -@end defun +@item mm-pipe-part +@findex mm-pipe-part +Offer to pipe the part to some process. -@defun mm-interactively-view-part handle -Prompt for a mailcap method to use to view the part and display it -externally using that method. -@end defun +@item mm-interactively-view-part +@findex mm-interactively-view-part +Prompt for a mailcap method to use to view the part. +@end table -@node Customization -@section Customization -The display of @sc{mime} types may be customized with the following -options. +@node Display Customization +@section Display Customization -@defopt mm-inline-media-tests -This is an alist where the key is a @sc{mime} type, the second element +@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. @@ -907,42 +279,55 @@ 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. -@end defopt -@defopt mm-inlined-types +@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 -@sc{mime} media types. -@end defopt +@acronym{MIME} media types. -@defopt mm-automatic-display +@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. -@end defopt -@defopt mm-attachment-override-types -Some @sc{mime} agents create parts that have a content-disposition of +@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.) -@end defopt -@defopt mm-discouraged-alternatives -List of @sc{mime} types that are discouraged when viewing +@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/richtech} parts are somewhat unwanted, -then the value of this variable should be set to: +very unwanted, and @samp{text/richtext} parts are somewhat unwanted, +you could say something like: @lisp -("text/html" "text/richtext") +(setq mm-discouraged-alternatives + '("text/html" "text/richtext") + mm-automatic-display + (remove "text/html" mm-automatic-display)) @end lisp -@end defopt -@defopt mm-inline-large-images-p +@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 @@ -951,9 +336,9 @@ 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. -@end defopt -@defopt mm-inline-override-p +@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 @@ -961,13 +346,130 @@ 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. -@end defopt +@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}, +@code{w3m}@footnote{See @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 +@code{nil}.@footnote{The 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 non-@code{nil}. 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 @samp{text/enriched} inline: +Here's an example viewer for displaying @code{text/enriched} inline: @lisp (defun mm-display-enriched-inline (handle) @@ -980,7 +482,7 @@ Here's an example viewer for displaying @samp{text/enriched} inline: (mm-insert-inline handle text))) @end lisp -We see that the function takes a @sc{mime} handle as its parameter. It +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. @@ -990,7 +492,7 @@ The two important helper functions here are @code{mm-insert-part} and 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. +``undisplayed'' in a convenient manner. @node Composing @@ -1000,21 +502,24 @@ tell it to insert, but it also sets things up so that the text can be @cindex MML @cindex MIME Meta Language -Creating a @sc{mime} message is boring and non-trivial. Therefore, a -library called @code{mml} has been defined that parses a language called -MML (@sc{mime} Meta Language) and generates @sc{mime} messages. +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 @sc{mime} message. +string containing the @acronym{MIME} message. @menu -* Simple MML Example:: An example MML document. -* MML Definition:: All valid MML elements. -* Advanced MML Example:: Another example MML document. -* Charset Translation:: How charsets are mapped from Mule to MIME. -* Conversion:: Going from @sc{mime} to MML and vice versa. +* 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 @@ -1055,10 +560,10 @@ Content-Type: text/enriched @node MML Definition @section MML Definition -The MML language is very simple. It looks a bit like an SGML +The @acronym{MML} language is very simple. It looks a bit like an SGML application, but it's not. -The main concept of MML is the @dfn{part}. Each part can be of a +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 @@ -1073,58 +578,85 @@ Each tag can contain zero or more parameters on the form 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 MML; parameters that have no -meaning are ignored. The MML parameter names are the same as the -@sc{mime} parameter names; the things in the parentheses say which +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 @sc{mime} type of the part (@samp{Content-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 -(@samp{Content-Disposition}). +(@code{Content-Disposition}). @item charset The contents of the body of the part are to be encoded in the character -set specified (@samp{Content-Type}). +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 (@samp{Content-Type}). +to a file (@code{Content-Type}). @item disposition Valid values are @samp{inline} and @samp{attachment} -(@samp{Content-Disposition}). +(@code{Content-Disposition}). @item encoding Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and -@samp{base64} (@samp{Content-Transfer-Encoding}). +@samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset +Translation}. @item description -A description of the part (@samp{Content-Description}). +A description of the part (@code{Content-Description}). @item creation-date -RFC822 date when the part was created (@samp{Content-Disposition}). +RFC822 date when the part was created (@code{Content-Disposition}). @item modification-date -RFC822 date when the part was modified (@samp{Content-Disposition}). +RFC822 date when the part was modified (@code{Content-Disposition}). @item read-date -RFC822 date when the part was read (@samp{Content-Disposition}). +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 (@samp{Content-Disposition}). +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 -(@samp{Content-Type}). +(@code{Content-Type}). @end table Parameters for @samp{message/external-body}: @@ -1133,18 +665,36 @@ Parameters for @samp{message/external-body}: @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}. (@samp{Content-Type}.) +@samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.) @item expiration The RFC822 date after which the file may no longer be fetched. -(@samp{Content-Type}.) +(@code{Content-Type}.) @item size -The size (in octets) of the file. (@samp{Content-Type}.) +The size (in octets) of the file. (@code{Content-Type}.) @item permission Valid values are @samp{read} and @samp{read-write} -(@samp{Content-Type}). +(@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 @@ -1169,7 +719,7 @@ This plain text part is an attachment. <#/multipart> @end example -And this is the resulting @sc{mime} message: +And this is the resulting @acronym{MIME} message: @example Content-Type: multipart/mixed; boundary="=-=-=" @@ -1235,74 +785,151 @@ 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. + +@code{qp-or-base64} has another effect. It will fold long lines so that +MIME parts may not be broken by MTA. So do @code{quoted-printable} and +@code{base64}. + +Note that it affects body encoding only when a part is a raw forwarded +message (which will be made by @code{gnus-summary-mail-forward} with the +arg 2 for example) or is neither the @samp{text/*} type nor the +@samp{message/*} type. Even though in those cases, 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 non-@code{nil}, 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 MML to @sc{mime}, for each @sc{mime} part which -has been composed inside Emacs, an appropriate @sc{mime} charset has to -be chosen. +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 -@cindex unibyte Emacs -If you are running a non-Mule XEmacs, or Emacs in unibyte -mode@footnote{Deprecated!}, this process is simple: if the part -contains any non-@sc{ascii} (8-bit) characters, the @sc{mime} charset +If you are running a non-@sc{mule} Emacs, this process is simple: If the +part contains any non-@acronym{ASCII} (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 -@sc{mime} messages. @xref{Various Message Variables, , Various Message -Variables, message, Message Manual}, for example.) If there are only -@sc{ascii} characters, the @sc{mime} charset @samp{US-ASCII} is used, of -course. - -@cindex multibyte Emacs -@cindex @code{mime-charset} property -In a normal (multibyte) Emacs session, a list of coding systems is -derived that can encode the message part's content and correspond to -MIME charsets (according to their @code{mime-charset} property). This -list is according to the normal priority rules and the highest priority -one is chosen to encode the part. If no such coding system can encode -the part's contents, they are split into several parts such that each -can be encoded with an appropriate coding system/@sc{mime} -charset.@footnote{The part can only be split at line boundaries, -though---if more than one @sc{mime} charset is required to encode a -single line, it is not possible to encode the part.} Note that this -procedure works with any correctly-defined coding systems, not just -built-in ones. Given a suitably-defined UTF-8 coding system---one -capable of encoding the Emacs charsets you use---it is not normally -necessary to split a part by charset. - +@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 -@cindex XEmacs/Mule -It isn't possible to do this properly in XEmacs/Mule. Instead, a list -of the Mule charsets used in the part is obtained, and the -corresponding @sc{mime} charsets are determined by lookup in -@code{mm-mime-mule-charset-alist}. If the list elements all -correspond to a single @sc{mime} charset, that is used to encode the -part. Otherwise, the part is split as above. +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) @sc{mime} message can be converted to MML with the -@code{mime-to-mml} function. It works on the message in the current -buffer, and substitutes MML markup for @sc{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 MML -tags. +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 MML message can be converted back to @sc{mime} by the +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 @sc{mime-to-mml} and then -@sc{mml-to-mime}. Not only will trivial things like the order of the +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 @sc{mml-to-mime} may decide to use quoted-printable encoding, and +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 @@ -1310,13 +937,772 @@ 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 non-@acronym{ASCII} 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 non-@acronym{ASCII} 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 non-@acronym{ASCII} 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 Non-@acronym{ASCII} Text) specifies how +non-@acronym{ASCII} 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-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 @code{nil}, in which case the header(s) in question +won't be encoded, @code{mime}, which means that they will be encoded, or +@code{address-mime}, which means the header(s) will be encoded carefully +assuming they contain addresses. + +@item rfc2047-charset-encoding-alist +@vindex rfc2047-charset-encoding-alist +RFC2047 specifies two forms of encoding---@code{Q} (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-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 GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye. +@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 @sc{mime} library implements handling of various elements +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 @samp{http://quimby.gnus.org/notes/}. +fetched from @uref{http://quimby.gnus.org/notes/}. @table @dfn @item RFC822 @@ -1326,10 +1712,6 @@ Standard for the Format of ARPA Internet Text Messages. @item RFC1036 Standard for Interchange of USENET Messages -@item RFC1524 -A User Agent Configuration Mechanism For Multimedia Mail Format -Information - @item RFC2045 Format of Internet Message Bodies @@ -1337,7 +1719,7 @@ Format of Internet Message Bodies Media Types @item RFC2047 -Message Header Extensions for Non-ASCII Text +Message Header Extensions for Non-@acronym{ASCII} Text @item RFC2048 Registration Procedures @@ -1346,18 +1728,18 @@ Registration Procedures Conformance Criteria and Examples @item RFC2231 -MIME Parameter Value and Encoded Word Extensions: Character Sets, +@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 -ASCII characters +@acronym{ASCII} characters @item draft-ietf-drums-msg-fmt-05.txt Draft for the successor of RFC822 @item RFC2112 -The MIME Multipart/Related Content-type +The @acronym{MIME} Multipart/Related Content-type @item RFC1892 The Multipart/Report Content Type for the Reporting of Mail System @@ -1367,18 +1749,24 @@ Administrative Messages 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 -@printindex fn @summarycontents @contents @bye + +@c Local Variables: +@c mode: texinfo +@c coding: iso-8859-1 @c End: @ignore |