188 lines
6.7 KiB
EmacsLisp
188 lines
6.7 KiB
EmacsLisp
;;; flow-fill.el --- interpret RFC2646 "flowed" text -*- lexical-binding:t -*-
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;; Copyright (C) 2000-2024 Free Software Foundation, Inc.
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;; Author: Simon Josefsson <jas@pdc.kth.se>
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;; Keywords: mail
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; This implement decoding of RFC2646 formatted text, including the
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;; quoted-depth wins rules.
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;; Theory of operation: search for lines ending with SPC, save quote
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;; length of line, remove SPC and concatenate line with the following
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;; line if quote length of following line matches current line.
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;; When no further concatenations are possible, we've found a
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;; paragraph and we let `fill-region' fill the long line into several
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;; lines with the quote prefix as `fill-prefix'.
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;; Todo: implement basic `fill-region'
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;;; History:
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;; 2000-02-17 posted on ding mailing list
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;; 2000-02-19 use `point-at-{b,e}ol' in XEmacs
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;; 2000-03-11 no compile warnings for point-at-bol stuff
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;; 2000-03-26 committed to gnus cvs
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;; 2000-10-23 don't flow "-- " lines, make "quote-depth wins" rule
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;; work when first line is at level 0.
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;; 2002-01-12 probably incomplete encoding support
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;; 2003-12-08 started working on test harness.
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;;; Code:
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(defcustom fill-flowed-display-column 'fill-column
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"Column beyond which format=flowed lines are wrapped, when displayed.
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This can be a Lisp expression or an integer."
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:version "22.1"
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:group 'mime-display
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:type '(choice (const :tag "Standard `fill-column'" fill-column)
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(const :tag "Fit Window" (- (window-width) 5))
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(sexp)
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(integer)))
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(defcustom fill-flowed-encode-column 66
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"Column beyond which format=flowed lines are wrapped, in outgoing messages.
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This can be a Lisp expression or an integer.
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RFC 2646 suggests 66 characters for readability."
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:version "22.1"
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:group 'mime-display
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:type '(choice (const :tag "Standard fill-column" fill-column)
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(const :tag "RFC 2646 default (66)" 66)
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(sexp)
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(integer)))
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;;;###autoload
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(defun fill-flowed-encode (&optional buffer)
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(with-current-buffer (or buffer (current-buffer))
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;; No point in doing this unless hard newlines is used.
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(when use-hard-newlines
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(let ((start (point-min)) end)
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;; Go through each paragraph, filling it and adding SPC
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;; as the last character on each line.
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(while (and (< start (point-max))
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(setq end (or (text-property-any start (point-max) 'hard 't)
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(point-max))))
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(save-restriction
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(narrow-to-region start end)
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(let ((fill-column (eval fill-flowed-encode-column t)))
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(fill-flowed-fill-buffer))
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(goto-char (point-min))
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(while (re-search-forward "\n" nil t)
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(replace-match " \n" t t))
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(goto-char (setq start (1+ (point-max)))))))
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t)))
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(defun fill-flowed-fill-buffer ()
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(let ((prefix nil)
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(prev-prefix nil)
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(start (point-min)))
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(goto-char (point-min))
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(while (not (eobp))
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(setq prefix (and (looking-at "[> ]+")
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(match-string 0)))
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(if (equal prefix prev-prefix)
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(forward-line 1)
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(save-restriction
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(narrow-to-region start (point))
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(let ((fill-prefix prev-prefix))
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(fill-region (point-min) (point-max) t 'nosqueeze 'to-eop))
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(goto-char (point-max)))
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(setq prev-prefix prefix
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start (point))))
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(save-restriction
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(narrow-to-region start (point))
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(let ((fill-prefix prev-prefix))
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(fill-region (point-min) (point-max) t 'nosqueeze 'to-eop)))))
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;;;###autoload
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(defun fill-flowed (&optional buffer delete-space)
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"Apply RFC2646 decoding to BUFFER.
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If BUFFER is nil, default to the current buffer.
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If DELETE-SPACE, delete RFC2646 spaces padding at the end of
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lines."
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(with-current-buffer (or buffer (current-buffer))
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(let ((fill-column (eval fill-flowed-display-column t)))
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(goto-char (point-min))
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(while (not (eobp))
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(cond
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((and (looking-at "^>+")
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(eq (char-before (line-end-position)) ?\s))
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(let ((prefix (match-string 0)))
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;; Insert a space character after the quote signs for more
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;; pleasant reading of quoted lines.
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(goto-char (match-end 0))
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(unless (looking-at " ")
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(insert " "))
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(while (and (eq (char-before (line-end-position)) ?\s)
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(not (eobp))
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(save-excursion
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(forward-line 1)
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(looking-at (format "\\(%s ?\\)[^>]" prefix))))
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(end-of-line)
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(when (and (not (eobp))
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(save-excursion
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(forward-line 1)
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(looking-at (format "\\(%s ?\\)[^>]" prefix))))
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;; Delete the newline and the quote at the start of the
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;; next line.
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(delete-region (point) (match-end 1))))
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(ignore-errors
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(let ((fill-prefix (concat prefix " "))
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adaptive-fill-mode)
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(fill-region (line-beginning-position)
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(line-end-position)
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'left 'nosqueeze)))))
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(t
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;; Delete the newline.
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(when (eq (following-char) ?\s)
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(delete-char 1))
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;; Hack: Don't do the flowing on the signature line.
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(when (and (not (looking-at "-- $"))
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(eq (char-before (line-end-position)) ?\s))
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(while (and (not (eobp))
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(eq (char-before (line-end-position)) ?\s))
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(end-of-line)
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(when delete-space
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(delete-char -1))
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(delete-char 1))
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(ignore-errors
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(let ((fill-prefix ""))
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(fill-region (line-beginning-position)
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(line-end-position)
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'left 'nosqueeze))))))
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(forward-line 1)))))
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(make-obsolete-variable 'fill-flowed-encode-tests nil "27.1")
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(defvar fill-flowed-encode-tests)
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(defun fill-flowed-test ()
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(declare (obsolete nil "27.1"))
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(interactive "")
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(user-error (concat "This function is obsolete. Please see "
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"test/lisp/mail/flow-fill-tests.el "
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"in the Emacs source tree")))
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(provide 'flow-fill)
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;;; flow-fill.el ends here
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