1 ;;; mailheader.el --- mail header parsing, merging, formatting
3 ;; Copyright (C) 1996, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
4 ;; 2009, 2010 Free Software Foundation, Inc.
6 ;; Author: Erik Naggum <erik@naggum.no>
7 ;; Keywords: tools, mail, news
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software: you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation, either version 3 of the License, or
15 ;; (at your option) any later version.
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
27 ;; This package provides an abstraction to RFC822-style messages, used in
28 ;; mail, news, and some other systems. The simple syntactic rules for such
29 ;; headers, such as quoting and line folding, are routinely reimplemented
30 ;; in many individual packages. This package removes the need for this
31 ;; redundancy by representing message headers as association lists,
32 ;; offering functions to extract the set of headers from a message, to
33 ;; parse individual headers, to merge sets of headers, and to format a set
36 ;; The car of each element in the message-header alist is a symbol whose
37 ;; print name is the name of the header, in all lower-case. The cdr of an
38 ;; element depends on the operation. After extracting headers from a
39 ;; message, it is a string, the value of the header. An extracted set of
40 ;; headers may be parsed further, which may turn it into a list, whose car
41 ;; is the original value and whose subsequent elements depend on the
42 ;; header. For formatting, it is evaluated to obtain the strings to be
43 ;; inserted. For merging, one set of headers consists of strings, while
44 ;; the other set will be evaluated with the symbols in the first set of
45 ;; headers bound to their respective values.
52 (defun mail-header-extract ()
53 "Extract headers from current buffer after point.
54 Returns a header alist, where each element is a cons cell (name . value),
55 where NAME is a symbol, and VALUE is the string value of the header having
57 (let ((message-headers ()) (top (point))
59 (while (and (setq start
(point))
60 (> (skip-chars-forward "^\0- :") 0)
61 (= (following-char) ?
:)
64 (> (skip-chars-forward " \t") 0)))
65 (let ((header (intern (downcase (buffer-substring start end
))))
66 (value (list (buffer-substring
67 (point) (progn (end-of-line) (point))))))
68 (while (progn (forward-char) (> (skip-chars-forward " \t") 0))
69 (push (buffer-substring (point) (progn (end-of-line) (point)))
72 (cons header
(mapconcat #'identity
(nreverse value
) " "))
73 (cons header
(car value
)))
76 (nreverse message-headers
)))
78 (defun mail-header-extract-no-properties ()
79 "Extract headers from current buffer after point, without properties.
80 Returns a header alist, where each element is a cons cell (name . value),
81 where NAME is a symbol, and VALUE is the string value of the header having
85 (set-text-properties 0 (length (cdr elt
)) nil
(cdr elt
))
87 (mail-header-extract)))
89 (defun mail-header-parse (parsing-rules headers
)
90 "Apply PARSING-RULES to HEADERS.
91 PARSING-RULES is an alist whose keys are header names (symbols) and whose
92 value is a parsing function. The function takes one argument, a string,
93 and return a list of values, which will destructively replace the value
94 associated with the key in HEADERS, after being prepended with the original
96 (dolist (rule parsing-rules
)
97 (let ((header (assq (car rule
) headers
)))
99 (if (consp (cdr header
))
100 (setf (cddr header
) (funcall (cdr rule
) (cadr header
)))
102 (cons (cdr header
) (funcall (cdr rule
) (cdr header
))))))))
105 ;; Advertized part of the interface; see mail-header, mail-header-set.
108 (defsubst mail-header
(header &optional header-alist
)
109 "Return the value associated with header HEADER in HEADER-ALIST.
110 If the value is a string, it is the original value of the header. If the
111 value is a list, its first element is the original value of the header,
112 with any subsequent elements being the result of parsing the value.
113 If HEADER-ALIST is nil, the dynamically bound variable `headers' is used."
114 (cdr (assq header
(or header-alist headers
))))
116 (defun mail-header-set (header value
&optional header-alist
)
117 "Set the value associated with header HEADER to VALUE in HEADER-ALIST.
118 HEADER-ALIST defaults to the dynamically bound variable `headers' if nil.
119 See `mail-header' for the semantics of VALUE."
120 (let* ((alist (or header-alist headers
))
121 (entry (assq header alist
)))
123 (setf (cdr entry
) value
)
124 (nconc alist
(list (cons header value
)))))
127 (defsetf mail-header
(header &optional header-alist
) (value)
128 `(mail-header-set ,header
,value
,header-alist
))
130 (defun mail-header-merge (merge-rules headers
)
131 "Return a new header alist with MERGE-RULES applied to HEADERS.
132 MERGE-RULES is an alist whose keys are header names (symbols) and whose
133 values are forms to evaluate, the results of which are the new headers. It
134 should be a string or a list of string. The first element may be nil to
135 denote that the formatting functions must use the remaining elements, or
136 skip the header altogether if there are no other elements.
137 The macro `mail-header' can be used to access headers in HEADERS."
140 (cons (car rule
) (eval (cdr rule
))))
143 (defvar mail-header-format-function
144 (lambda (header value
)
145 "Function to format headers without a specified formatting function."
146 (insert (capitalize (symbol-name header
))
148 (if (consp value
) (car value
) value
)
151 (defun mail-header-format (format-rules headers
)
152 "Use FORMAT-RULES to format HEADERS and insert into current buffer.
153 HEADERS should be an alist of the form (HEADER . VALUE),
154 where HEADER is a header field name (a symbol or a string),
155 and VALUE is the contents for that header field.
157 FORMAT-RULES is an alist of elements (HEADER . FUNCTION) Here HEADER
158 is a header field name (a symbol), and FUNCTION is how to format that
159 header field, if it appears in HEADERS. Each FUNCTION should take two
160 arguments: the header symbol, and the value of that header. The value
161 returned by FUNCTION is inserted in the buffer unless it is nil.
163 If the function for a header field is nil, or if no function is
164 specified for a particular header field, the default action is to
165 insert the value of the header, unless it is nil.
167 The headers are inserted in the order of the FORMAT-RULES.
168 A key of t in FORMAT-RULES represents any otherwise unmentioned headers.
169 A key of nil has as its value a list of defaulted headers to ignore."
170 (let ((ignore (append (cdr (assq nil format-rules
))
171 (mapcar #'car format-rules
))))
172 (dolist (rule format-rules
)
173 (let* ((header (car rule
))
174 (value (mail-header header
)))
176 (setq header
(intern header
)))
177 (cond ((null header
) 'ignore
)
179 (dolist (defaulted headers
)
180 (unless (memq (car defaulted
) ignore
)
181 (let* ((header (car defaulted
))
182 (value (cdr defaulted
)))
184 (funcall (cdr rule
) header value
)
185 (funcall mail-header-format-function header value
))))))
188 (funcall (cdr rule
) header value
)
189 (funcall mail-header-format-function header value
))))))
192 (provide 'mailheader
)
194 ;;; mailheader.el ends here