Function: mm-find-mime-charset-region

mm-find-mime-charset-region is a byte-compiled function defined in mm-util.el.gz.

Signature

(mm-find-mime-charset-region B E &optional HACK-CHARSETS)

Documentation

Return the MIME charsets needed to encode the region between B and E.

nil means ASCII, a single-element list represents an appropriate MIME charset, and a longer list means no appropriate charset.

Source Code

;; Defined in /usr/src/emacs/lisp/gnus/mm-util.el.gz
(defun mm-find-mime-charset-region (b e &optional hack-charsets)
  "Return the MIME charsets needed to encode the region between B and E.
nil means ASCII, a single-element list represents an appropriate MIME
charset, and a longer list means no appropriate charset."
  (let (charsets)
    ;; The return possibilities of this function are a mess...
    (or (and enable-multibyte-characters
	     mm-use-find-coding-systems-region
	     ;; Find the mime-charset of the most preferred coding
	     ;; system that has one.
	     (let ((systems (find-coding-systems-region b e)))
	       (when mm-coding-system-priorities
		 (setq systems
		       (sort systems #'mm-sort-coding-systems-predicate)))
	       (setq systems (delq 'compound-text systems))
	       (unless (equal systems '(undecided))
		 (while systems
		   (let* ((head (pop systems))
			  (cs (or (coding-system-get head :mime-charset)
				  (coding-system-get head 'mime-charset))))
		     ;; The mime-charset (`x-ctext') of
		     ;; `compound-text' is not in the IANA list.  We
		     ;; shouldn't normally use anything here with a
		     ;; mime-charset having an `x-' prefix.
		     ;; Fixme:  Allow this to be overridden, since
		     ;; there is existing use of x-ctext.
		     ;; Also people apparently need the coding system
		     ;; `iso-2022-jp-3' (which Mule-UCS defines with
		     ;; mime-charset, though it's not valid).
		     (if (and cs
			      (not (string-match "^[Xx]-" (symbol-name cs)))
			      ;; UTF-16 of any variety is invalid for
			      ;; text parts and, unfortunately, has
			      ;; mime-charset defined both in Mule-UCS
			      ;; and versions of Emacs.  (The name
			      ;; might be `mule-utf-16...'  or
			      ;; `utf-16...'.)
			      (not (string-match "utf-16" (symbol-name cs))))
			 (setq systems nil
			       charsets (list cs))))))
	       charsets))
	;; We're not multibyte, or a single coding system won't cover it.
	(setq charsets
	      (delete-dups
	       (mapcar #'mm-mime-charset
		       (delq 'ascii
			     (mm-find-charset-region b e))))))
    (if (and (> (length charsets) 1)
	     (memq 'iso-8859-15 charsets)
	     (memq 'iso-8859-15 hack-charsets)
	     (save-excursion (mm-iso-8859-x-to-15-region b e)))
	(dolist (x mm-iso-8859-15-compatible)
	  (setq charsets (delq (car x) charsets))))
    (if (and (memq 'iso-2022-jp-2 charsets)
	     (memq 'iso-2022-jp-2 hack-charsets))
	(setq charsets (delq 'iso-2022-jp charsets)))
    charsets))