Function: sgml-parse-tag-backward

sgml-parse-tag-backward is a byte-compiled function defined in sgml-mode.el.gz.

Signature

(sgml-parse-tag-backward &optional LIMIT)

Documentation

Parse an SGML tag backward, and return information about the tag.

Assume that parsing starts from within a textual context. Leave point at the beginning of the tag.

Source Code

;; Defined in /usr/src/emacs/lisp/textmodes/sgml-mode.el.gz
(defun sgml-parse-tag-backward (&optional limit)
  "Parse an SGML tag backward, and return information about the tag.
Assume that parsing starts from within a textual context.
Leave point at the beginning of the tag."
  (catch 'found
    (let (tag-type tag-start tag-end name)
      (or (sgml--find-<>-backward limit)
	  (error "No tag found"))
      (when (eq (char-after) ?<)
	;; Oops!! Looks like we were not in a textual context after all!.
	;; Let's try to recover.
        ;; Remember the tag-start so we don't need to look for it later.
	;; This is not just an optimization but also makes sure we don't get
	;; stuck in infloops in cases where "looking back for <" would not go
	;; back far enough.
        (setq tag-start (point))
	(with-syntax-table sgml-tag-syntax-table
	  (let ((pos (point)))
	    (condition-case nil
                ;; FIXME: This does not correctly skip over PI and CDATA tags.
		(sgml-forward-sexp 1)
	      (scan-error
	       ;; This < seems to be just a spurious one, let's ignore it.
	       (goto-char pos)
	       (throw 'found (sgml-parse-tag-backward limit))))
	    ;; Check it is really a tag, without any extra < or > inside.
	    (unless (sgml-tag-text-p pos (point))
	      (goto-char pos)
	      (throw 'found (sgml-parse-tag-backward limit)))
	    (forward-char -1))))
      (setq tag-end (1+ (point)))
      (cond
       ((sgml-looking-back-at "--")	; comment
	(setq tag-type 'comment
	      tag-start (or tag-start (search-backward "<!--" nil t))))
       ((sgml-looking-back-at "]]")	; cdata
	(setq tag-type 'cdata
	      tag-start (or tag-start
                            (re-search-backward "<!\\[[A-Z]+\\[" nil t))))
       ((sgml-looking-back-at "?")      ; XML processing-instruction
        (setq tag-type 'pi
              ;; IIUC: SGML processing instructions take the form <?foo ...>
              ;; i.e. a "normal" tag, handled below.  In XML this is changed
              ;; to <?foo ... ?> where "..." can contain < and > and even <?
              ;; but not ?>.  This means that when parsing backward, there's
              ;; no easy way to make sure that we find the real beginning of
              ;; the PI.
	      tag-start (or tag-start (search-backward "<?" nil t))))
       (t
        (unless tag-start
          (setq tag-start
                (with-syntax-table sgml-tag-syntax-table
                  (goto-char tag-end)
                  (condition-case nil
                      (sgml-forward-sexp -1)
                    (scan-error
                     ;; This > isn't really the end of a tag. Skip it.
                     (goto-char (1- tag-end))
                     (throw 'found (sgml-parse-tag-backward limit))))
                  (point))))
	(goto-char (1+ tag-start))
	(pcase (char-after)
	  (?! (setq tag-type 'decl))    ; declaration
	  (?? (setq tag-type 'pi))      ; processing-instruction
	  (?% (setq tag-type 'jsp))	; JSP tags
	  (?/				; close-tag
	   (forward-char 1)
	   (setq tag-type 'close
		 name (sgml-parse-tag-name)))
	  (_				; open or empty tag
	   (setq tag-type 'open
		 name (sgml-parse-tag-name))
	   (if (or (eq ?/ (char-before (- tag-end 1)))
		   (sgml-empty-tag-p name))
	       (setq tag-type 'empty))))))
      (goto-char tag-start)
      (sgml-make-tag tag-type tag-start tag-end name))))