emacs/lisp/ediff-diff.el

;;; ediff-diff.el --- diff-related utilities

;; Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
;;   2002, 2003, 2004, 2005 Free Software Foundation, Inc.

;; Author: Michael Kifer <kifer@cs.stonybrook.edu>

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;;; Code:

(provide 'ediff-diff)

;; compiler pacifier
(defvar ediff-default-variant)
(defvar null-device)
(defvar longlines-mode)

(eval-when-compile
  (let ((load-path (cons (expand-file-name ".") load-path)))
    (or (featurep 'ediff-init)
	(load "ediff-init.el" nil nil 'nosuffix))
    (or (featurep 'ediff-util)
	(load "ediff-util.el" nil nil 'nosuffix))
    ))
;; end pacifier

(require 'ediff-init)

(defgroup ediff-diff nil
  "Diff related utilities."
  :prefix "ediff-"
  :group 'ediff)

;; these two must be here to prevent ediff-test-utility from barking
(defcustom ediff-diff-program "diff"
  "*Program to use for generating the differential of the two files."
  :type 'string
  :group 'ediff-diff)
(defcustom ediff-diff3-program "diff3"
  "*Program to be used for three-way comparison.
Must produce output compatible with Unix's diff3 program."
  :type 'string
  :group 'ediff-diff)


;; The following functions must precede all defcustom-defined variables.

;; The following functions needed for setting diff/diff3 options
;; test if diff supports the --binary option
(defsubst ediff-test-utility (diff-util option &optional files)
  (eq 0 (apply 'call-process
	       (append (list diff-util nil nil nil option) files))))

(defun ediff-diff-mandatory-option (diff-util)
  (let ((file (if (boundp 'null-device) null-device "/dev/null")))
    (cond  ((not (memq system-type '(ms-dos windows-nt windows-95)))
	    "")
	   ((and (string= diff-util ediff-diff-program)
		 (ediff-test-utility
		  ediff-diff-program "--binary" (list file file)))
	    "--binary")
	   ((and (string= diff-util ediff-diff3-program)
		 (ediff-test-utility
		  ediff-diff3-program "--binary" (list file file file)))
	    "--binary")
	   (t ""))))

;; make sure that mandatory options are added even if the user changes
;; ediff-diff-options or ediff-diff3-options in the customization widget
(defun ediff-reset-diff-options (symb val)
  (let* ((diff-program
	  (if (eq symb 'ediff-diff-options)
	      ediff-diff-program
	    ediff-diff3-program))
	 (mandatory-option (ediff-diff-mandatory-option diff-program))
	 (spacer (if (string-equal mandatory-option "") "" " ")))
    (set symb
	 (if (string-match mandatory-option val)
	     val
	   (concat mandatory-option spacer val)))
    ))


(defcustom ediff-shell
  (cond ((eq system-type 'emx) "cmd") ; OS/2
	((memq system-type '(ms-dos windows-nt windows-95))
	 shell-file-name) ; no standard name on MS-DOS
	((memq system-type '(vax-vms axp-vms)) "*dcl*") ; VMS
	(t  "sh")) ; UNIX
  "*The shell used to run diff and patch.
If user's .profile or .cshrc files are set up correctly, any shell
will do.  However, some people set $prompt or other things
incorrectly, which leads to undesirable output messages.  These may
cause Ediff to fail.  In such a case, set `ediff-shell' to a shell that
you are not using or, better, fix your shell's startup file."
  :type 'string
  :group 'ediff-diff)

(defcustom ediff-cmp-program "cmp"
  "*Utility to use to determine if two files are identical.
It must return code 0, if its arguments are identical files."
  :type 'string
  :group 'ediff-diff)

(defcustom ediff-cmp-options nil
  "*Options to pass to `ediff-cmp-program'.
If GNU diff is used as `ediff-cmp-program', then the most useful options
are `-I REGEXP', to ignore changes whose lines match the REGEXP."
  :type '(repeat string)
  :group 'ediff-diff)

(defcustom ediff-diff-options ""
  "*Options to pass to `ediff-diff-program'.
If Unix diff is used as `ediff-diff-program', then the most useful options are
`-w', to ignore space, and `-i', to ignore case of letters.
At present, the option `-c' is not allowed."
  :set 'ediff-reset-diff-options
  :type 'string
  :group 'ediff-diff)

(defcustom ediff-custom-diff-program ediff-diff-program
  "*Program to use for generating custom diff output for saving it in a file.
This output is not used by Ediff internally."
  :type 'string
  :group 'ediff-diff)
(defcustom ediff-custom-diff-options "-c"
  "*Options to pass to `ediff-custom-diff-program'."
  :type 'string
  :group 'ediff-diff)

;;; Support for diff3

(defvar ediff-match-diff3-line "^====\\(.?\\)\C-m?$"
  "Pattern to match lines produced by diff3 that describe differences.")
(defcustom ediff-diff3-options ""
  "*Options to pass to `ediff-diff3-program'."
  :set 'ediff-reset-diff-options
  :type 'string
  :group 'ediff-diff)
(defcustom ediff-diff3-ok-lines-regexp
  "^\\([1-3]:\\|====\\|  \\|.*Warning *:\\|.*No newline\\|.*missing newline\\|^\C-m$\\)"
  "*Regexp that matches normal output lines from `ediff-diff3-program'.
Lines that do not match are assumed to be error messages."
  :type 'regexp
  :group 'ediff-diff)

;; keeps the status of the current diff in 3-way jobs.
;; the status can be =diff(A), =diff(B), or =diff(A+B)
(ediff-defvar-local ediff-diff-status "" "")


;;; Fine differences

(ediff-defvar-local ediff-auto-refine (if (ediff-has-face-support-p) 'on 'nix)
  "If `on', Ediff auto-highlights fine diffs for the current diff region.
If `off', auto-highlighting is not used. If `nix', no fine diffs are shown
at all, unless the user force-refines the region by hitting `*'.

This variable can be set either in .emacs or toggled interactively.
Use `setq-default' if setting it in .emacs")

(ediff-defvar-local ediff-ignore-similar-regions nil
  "*If t, skip over difference regions that differ only in the white space and line breaks.
This variable can be set either in .emacs or toggled interactively.
Use `setq-default' if setting it in .emacs")

(ediff-defvar-local ediff-auto-refine-limit 1400
  "*Auto-refine only the regions of this size \(in bytes\) or less.")

;;; General

(defvar ediff-diff-ok-lines-regexp
  (concat
   "^\\("
   "[0-9,]+[acd][0-9,]+\C-m?$"
   "\\|[<>] "
   "\\|---"
   "\\|.*Warning *:"
   "\\|.*No +newline"
   "\\|.*missing +newline"
   "\\|^\C-m?$"
   "\\)")
  "Regexp that matches normal output lines from `ediff-diff-program'.
This is mostly lifted from Emerge, except that Ediff also considers
warnings and `Missing newline'-type messages to be normal output.
Lines that do not match are assumed to be error messages.")

(defvar ediff-match-diff-line
  (let ((x "\\([0-9]+\\)\\(\\|,\\([0-9]+\\)\\)"))
    (concat "^" x "\\([acd]\\)" x "\C-m?$"))
  "Pattern to match lines produced by diff that describe differences.")

(ediff-defvar-local ediff-setup-diff-regions-function nil
  "value is a function symbol depending on the kind of job is to be done.
For 2-way jobs and for ediff-merge, it should be `ediff-setup-diff-regions'.
For jobs requiring diff3, it should be `ediff-setup-diff-regions3'.

The function should take three mandatory arguments, file-A, file-B, and
file-C. It may ignore file C for diff2 jobs. It should also take
one optional arguments, diff-number to refine.")


;;; Functions

;; Generate the difference vector and overlays for the two files
;; With optional arg REG-TO-REFINE, refine this region.
;; File-C argument is not used here. It is there just because
;; ediff-setup-diff-regions is called via a funcall to
;; ediff-setup-diff-regions-function, which can also have the value
;; ediff-setup-diff-regions3, which takes 4 arguments.
(defun ediff-setup-diff-regions (file-A file-B file-C)
  ;; looking either for '-c' or a 'c' in a set of clustered non-long options
  (if (string-match "^-c\\| -c\\|-[^- ]+c" ediff-diff-options)
      (error "Option `-c' is not allowed in `ediff-diff-options'"))

  ;; create, if it doesn't exist
  (or (ediff-buffer-live-p ediff-diff-buffer)
      (setq ediff-diff-buffer
	    (get-buffer-create (ediff-unique-buffer-name "*ediff-diff" "*"))))
  (ediff-make-diff2-buffer ediff-diff-buffer file-A file-B)
  (ediff-prepare-error-list ediff-diff-ok-lines-regexp ediff-diff-buffer)
  (ediff-convert-diffs-to-overlays
   (ediff-extract-diffs
    ediff-diff-buffer ediff-word-mode ediff-narrow-bounds)))

;; Run the diff program on FILE1 and FILE2 and put the output in DIFF-BUFFER
;; Return the size of DIFF-BUFFER
;; The return code isn't used in the program at present.
(defun ediff-make-diff2-buffer (diff-buffer file1 file2)
  (let ((file1-size (ediff-file-size file1))
	(file2-size (ediff-file-size file2)))
    (cond ((not (numberp file1-size))
	   (message "Can't find file: %s"
		    (ediff-abbreviate-file-name file1))
	   (sit-for 2)
	   ;; 1 is an error exit code
	   1)
	  ((not (numberp file2-size))
	   (message "Can't find file: %s"
		    (ediff-abbreviate-file-name file2))
	   (sit-for 2)
	   ;; 1 is an error exit code
	   1)
	  (t (message "Computing differences between %s and %s ..."
		      (file-name-nondirectory file1)
		      (file-name-nondirectory file2))
	     ;; this erases the diff buffer automatically
	     (ediff-exec-process ediff-diff-program
				 diff-buffer
				 'synchronize
				 ediff-diff-options file1 file2)
	     (message "")
	     (ediff-with-current-buffer diff-buffer
	       (buffer-size))))))



;; If file-A/B/C is nil, do 2-way comparison with the non-nil buffers
;; This function works for diff3 and diff2 jobs
(defun ediff-setup-fine-diff-regions (file-A file-B file-C reg-num)
  (or (ediff-buffer-live-p ediff-fine-diff-buffer)
      (setq ediff-fine-diff-buffer
	    (get-buffer-create
	     (ediff-unique-buffer-name "*ediff-fine-diff" "*"))))

  (let (diff3-job diff-program diff-options ok-regexp diff-list)
    (setq diff3-job ediff-3way-job
	  diff-program (if diff3-job ediff-diff3-program ediff-diff-program)
	  diff-options (if diff3-job ediff-diff3-options ediff-diff-options)
	  ok-regexp (if diff3-job
			ediff-diff3-ok-lines-regexp
			ediff-diff-ok-lines-regexp))

    (ediff-message-if-verbose "Refining difference region %d ..." (1+ reg-num))
    (ediff-exec-process diff-program ediff-fine-diff-buffer 'synchronize
			diff-options
			;; The shuffle below is because we can compare 3-way
			;; or in several 2-way fashions, like fA fC, fA fB,
			;; or fB fC.
			(if file-A file-A file-B)
			(if file-B file-B file-A)
			(if diff3-job
			    (if file-C file-C file-B))
			) ; exec process

    (ediff-prepare-error-list ok-regexp ediff-fine-diff-buffer)
    (ediff-message-if-verbose
     "")
    ;; "Refining difference region %d ... done" (1+ reg-num))

    (setq diff-list
	  (if diff3-job
	      (ediff-extract-diffs3
	       ediff-fine-diff-buffer '3way-comparison 'word-mode)
	    (ediff-extract-diffs ediff-fine-diff-buffer 'word-mode)))
    ;; fixup diff-list
    (if diff3-job
	(cond ((not file-A)
	       (mapcar (lambda (elt)
			 (aset elt 0 nil)
			 (aset elt 1 nil))
		       (cdr diff-list)))
	      ((not file-B)
	       (mapcar (lambda (elt)
			 (aset elt 2 nil)
			 (aset elt 3 nil))
		       (cdr diff-list)))
	      ((not file-C)
	       (mapcar (lambda (elt)
			 (aset elt 4 nil)
			 (aset elt 5 nil))
		       (cdr diff-list)))
	  ))

    (ediff-convert-fine-diffs-to-overlays diff-list reg-num)
    ))


(defun ediff-prepare-error-list (ok-regexp diff-buff)
  (or (ediff-buffer-live-p ediff-error-buffer)
      (setq ediff-error-buffer
	    (get-buffer-create (ediff-unique-buffer-name
				"*ediff-errors" "*"))))
  (ediff-with-current-buffer ediff-error-buffer
    (erase-buffer)
    (insert (ediff-with-current-buffer diff-buff (buffer-string)))
    (goto-char (point-min))
    (delete-matching-lines ok-regexp)
    (if (memq system-type '(vax-vms axp-vms))
	(delete-matching-lines "^$")))
  ;; If diff reports errors, show them then quit.
  (if (/= 0 (ediff-with-current-buffer ediff-error-buffer (buffer-size)))
      (let ((ctl-buf ediff-control-buffer)
	    (error-buf ediff-error-buffer))
	(ediff-skip-unsuitable-frames)
	(switch-to-buffer error-buf)
	(ediff-kill-buffer-carefully ctl-buf)
	(error "Errors in diff output.  Diff output is in %S" diff-buff))))

;; BOUNDS specifies visibility bounds to use.
;; WORD-MODE tells whether we are in the word-mode or not.
;; If WORD-MODE, also construct vector of diffs using word numbers.
;; Else, use point values.
;; This function handles diff-2 jobs including the case of
;; merging buffers and files without ancestor.
(defun ediff-extract-diffs (diff-buffer word-mode &optional bounds)
  (let ((A-buffer ediff-buffer-A)
	(B-buffer ediff-buffer-B)
	(C-buffer ediff-buffer-C)
	(a-prev 1) ; this is needed to set the first diff line correctly
	(b-prev 1)
	(c-prev 1)
	diff-list shift-A shift-B
	)

    ;; diff list contains word numbers, unless changed later
    (setq diff-list (cons (if word-mode 'words 'points)
			  diff-list))
    ;; we don't use visibility bounds for buffer C when merging
    (if bounds
	(setq shift-A
	      (ediff-overlay-start
	       (ediff-get-value-according-to-buffer-type 'A bounds))
	      shift-B
	      (ediff-overlay-start
	       (ediff-get-value-according-to-buffer-type 'B bounds))))

    ;; reset point in buffers A/B/C
    (ediff-with-current-buffer A-buffer
      (goto-char (if shift-A shift-A (point-min))))
    (ediff-with-current-buffer B-buffer
      (goto-char (if shift-B shift-B (point-min))))
    (if (ediff-buffer-live-p C-buffer)
	(ediff-with-current-buffer C-buffer
	  (goto-char (point-min))))

    (ediff-with-current-buffer diff-buffer
      (goto-char (point-min))
      (while (re-search-forward ediff-match-diff-line nil t)
       (let* ((a-begin (string-to-number (buffer-substring (match-beginning 1)
                                                           (match-end 1))))
	      (a-end  (let ((b (match-beginning 3))
			    (e (match-end 3)))
			(if b
			    (string-to-number (buffer-substring b e))
			  a-begin)))
	      (diff-type (buffer-substring (match-beginning 4) (match-end 4)))
	      (b-begin (string-to-number (buffer-substring (match-beginning 5)
                                                           (match-end 5))))
	      (b-end (let ((b (match-beginning 7))
			   (e (match-end 7)))
		       (if b
			   (string-to-number (buffer-substring b e))
			 b-begin)))
	      a-begin-pt a-end-pt b-begin-pt b-end-pt
	      c-begin c-end c-begin-pt c-end-pt)
	 ;; fix the beginning and end numbers, because diff is somewhat
	 ;; strange about how it numbers lines
	 (if (string-equal diff-type "a")
	     (setq b-end (1+ b-end)
		   a-begin (1+ a-begin)
		   a-end a-begin)
	   (if (string-equal diff-type "d")
	       (setq a-end (1+ a-end)
		     b-begin (1+ b-begin)
		     b-end b-begin)
	     ;; (string-equal diff-type "c")
	     (setq a-end (1+ a-end)
		   b-end (1+ b-end))))

	 (if (eq ediff-default-variant 'default-B)
	     (setq c-begin b-begin
		   c-end b-end)
	   (setq c-begin a-begin
		 c-end a-end))

	 ;; compute main diff vector
	 (if word-mode
	     ;; make diff-list contain word numbers
	     (setq diff-list
		   (nconc diff-list
			  (list
			   (if (ediff-buffer-live-p C-buffer)
			       (vector (- a-begin a-prev) (- a-end a-begin)
				       (- b-begin b-prev) (- b-end b-begin)
				       (- c-begin c-prev) (- c-end c-begin)
				       nil nil ; dummy ancestor
				       nil     ; state of diff
				       nil     ; state of merge
				       nil     ; state of ancestor
				       )
			     (vector (- a-begin a-prev) (- a-end a-begin)
				     (- b-begin b-prev) (- b-end b-begin)
				     nil nil ; dummy buf C
				     nil nil ; dummy ancestor
				     nil     ; state of diff
				     nil     ; state of merge
				     nil     ; state of ancestor
				     ))
			   ))
		   a-prev a-end
		   b-prev b-end
		   c-prev c-end)
	   ;; else convert lines to points
	   (ediff-with-current-buffer A-buffer
	     (let ((longlines-mode-val
		    (if (and (boundp 'longlines-mode) longlines-mode) 1 0)))
	       ;; we must disable and then restore longlines-mode
	       (if (eq longlines-mode-val 1)
		   (longlines-mode 0))
	       (forward-line (- a-begin a-prev))
	       (setq a-begin-pt (point))
	       (forward-line (- a-end a-begin))
	       (setq a-end-pt (point)
		     a-prev a-end)
	       (if (eq longlines-mode-val 1)
		   (longlines-mode longlines-mode-val))
	       ))
	   (ediff-with-current-buffer B-buffer
	     (let ((longlines-mode-val
		    (if (and (boundp 'longlines-mode) longlines-mode) 1 0)))
	       (if (eq longlines-mode-val 1)
		   (longlines-mode 0))
	       (forward-line (- b-begin b-prev))
	       (setq b-begin-pt (point))
	       (forward-line (- b-end b-begin))
	       (setq b-end-pt (point)
		     b-prev b-end)
	       (if (eq longlines-mode-val 1)
		   (longlines-mode longlines-mode-val))
	       ))
	   (if (ediff-buffer-live-p C-buffer)
	       (ediff-with-current-buffer C-buffer
		 (let ((longlines-mode-val
			(if (and (boundp 'longlines-mode) longlines-mode) 1 0)))
		   (if (eq longlines-mode-val 1)
		       (longlines-mode 0))
		   (forward-line (- c-begin c-prev))
		   (setq c-begin-pt (point))
		   (forward-line (- c-end c-begin))
		   (setq c-end-pt (point)
			 c-prev c-end)
		   (if (eq longlines-mode-val 1)
		       (longlines-mode longlines-mode-val))
		 )))
	   (setq diff-list
		 (nconc
		  diff-list
		  (list
		   (if (ediff-buffer-live-p C-buffer)
		       (vector
			a-begin-pt a-end-pt b-begin-pt b-end-pt
			c-begin-pt c-end-pt
			nil nil	; dummy ancestor
			;; state of diff
			;; shows which buff is different from the other two
			(if (eq ediff-default-variant 'default-B) 'A 'B)
			ediff-default-variant	; state of merge
			nil			; state of ancestor
			)
		     (vector a-begin-pt a-end-pt
			     b-begin-pt b-end-pt
			     nil nil	; dummy buf C
			     nil nil	; dummy ancestor
			     nil nil	; dummy state of diff & merge
			     nil	; dummy state of ancestor
			     )))
		  )))

	 ))) ; end ediff-with-current-buffer
    diff-list
    ))


(defun ediff-convert-diffs-to-overlays (diff-list)
  (ediff-set-diff-overlays-in-one-buffer 'A diff-list)
  (ediff-set-diff-overlays-in-one-buffer 'B diff-list)
  (if ediff-3way-job
      (ediff-set-diff-overlays-in-one-buffer 'C diff-list))
  (if ediff-merge-with-ancestor-job
      (ediff-set-diff-overlays-in-one-buffer 'Ancestor diff-list))
  ;; set up vector showing the status of merge regions
  (if ediff-merge-job
      (setq ediff-state-of-merge
	    (vconcat
	     (mapcar (lambda (elt)
		       (let ((state-of-merge (aref elt 9))
			     (state-of-ancestor (aref elt 10)))
			 (vector
			  ;; state of merge: prefers/default-A/B or combined
			  (if state-of-merge (format "%S" state-of-merge))
			  ;; whether the ancestor region is empty
			  state-of-ancestor)))
		     ;; the first elt designates type of list
		     (cdr diff-list))
	     )))
  (message "Processing difference regions ... done"))


(defun ediff-set-diff-overlays-in-one-buffer (buf-type diff-list)
  (let* ((current-diff -1)
	 (buff (ediff-get-buffer buf-type))
	 (ctl-buf ediff-control-buffer)
	 ;; ediff-extract-diffs puts the type of diff-list as the first elt
	 ;; of this list. The type is either 'points or 'words
	 (diff-list-type (car diff-list))
	 (shift (ediff-overlay-start
		 (ediff-get-value-according-to-buffer-type
		  buf-type ediff-narrow-bounds)))
	 (limit (ediff-overlay-end
		 (ediff-get-value-according-to-buffer-type
		  buf-type ediff-narrow-bounds)))
	 diff-overlay-list list-element total-diffs
	 begin end pt-saved overlay state-of-diff)

    (setq diff-list (cdr diff-list)) ; discard diff list type
    (setq total-diffs (length diff-list))

    ;; shift, if necessary
    (ediff-with-current-buffer buff (setq pt-saved shift))

    (while diff-list
      (setq current-diff (1+ current-diff)
	    list-element (car diff-list)
	    begin 	 (aref list-element (cond ((eq buf-type 'A) 0)
						  ((eq buf-type 'B) 2)
						  ((eq buf-type 'C) 4)
						  (t 6)))  ; Ancestor
	    end 	 (aref list-element (cond ((eq buf-type 'A) 1)
						  ((eq buf-type 'B) 3)
						  ((eq buf-type 'C) 5)
						  (t 7)))  ; Ancestor
	    state-of-diff (aref list-element 8)
	    )

      (cond ((and (not (eq buf-type state-of-diff))
		  (not (eq buf-type 'Ancestor))
		  (memq state-of-diff '(A B C)))
	     (setq state-of-diff
		   (car (delq buf-type (delq state-of-diff (list 'A 'B 'C)))))
	     (setq state-of-diff (format "=diff(%S)" state-of-diff))
	     )
	    (t (setq state-of-diff nil)))

      ;; Put overlays at appropriate places in buffer
      ;; convert word numbers to points, if necessary
      (if (eq diff-list-type 'words)
	  (progn
	    (ediff-with-current-buffer buff (goto-char pt-saved))
	    (ediff-with-current-buffer ctl-buf
	      (setq begin (ediff-goto-word (1+ begin) buff)
		    end (ediff-goto-word end buff 'end)))
	    (if (> end limit) (setq end limit))
	    (if (> begin end) (setq begin end))
	    (setq pt-saved (ediff-with-current-buffer buff (point)))))
      (setq overlay (ediff-make-bullet-proof-overlay begin end buff))

      (ediff-overlay-put overlay 'priority ediff-shadow-overlay-priority)
      (ediff-overlay-put overlay 'ediff-diff-num current-diff)
      (if (and (ediff-has-face-support-p)
	       ediff-use-faces ediff-highlight-all-diffs)
	  (ediff-set-overlay-face
	   overlay (ediff-background-face buf-type current-diff)))

      (if (= 0 (mod current-diff 10))
	  (message "Buffer %S: Processing difference region %d of %d"
		   buf-type current-diff total-diffs))
      ;; Record all overlays for this difference.
      ;; The 2-d elt, nil, is a place holder for the fine diff vector.
      ;; The 3-d elt, nil, is a place holder for no-fine-diffs flag.
      ;; The 4-th elt says which diff region is different from the other two
      ;; (3-way jobs only).
      (setq diff-overlay-list
	    (nconc
	     diff-overlay-list
	     (list (vector overlay nil nil state-of-diff)))
	    diff-list
	    (cdr diff-list))
      ) ; while

    (set (ediff-get-symbol-from-alist buf-type ediff-difference-vector-alist)
	 (vconcat diff-overlay-list))
    ))

;; `n' is the diff region to work on.  Default is ediff-current-difference.
;; if `flag' is 'noforce then make fine-diffs only if this region's fine
;; diffs have not been computed before.
;; if `flag' is 'skip then don't compute fine diffs for this region.
(defun ediff-make-fine-diffs (&optional n flag)
  (or n  (setq n ediff-current-difference))

  (if (< ediff-number-of-differences 1)
      (error ediff-NO-DIFFERENCES))

  (if ediff-word-mode
      (setq flag 'skip
	    ediff-auto-refine 'nix))

  (or (< n 0)
      (>= n ediff-number-of-differences)
      ;; n is within the range
      (let ((tmp-buffer (get-buffer-create ediff-tmp-buffer))
	    (file-A ediff-temp-file-A)
	    (file-B ediff-temp-file-B)
	    (file-C ediff-temp-file-C)
	    (empty-A (ediff-empty-diff-region-p n 'A))
	    (empty-B (ediff-empty-diff-region-p n 'B))
	    (empty-C (ediff-empty-diff-region-p n 'C))
	    (whitespace-A (ediff-whitespace-diff-region-p n 'A))
	    (whitespace-B (ediff-whitespace-diff-region-p n 'B))
	    (whitespace-C (ediff-whitespace-diff-region-p n 'C))
	    cumulative-fine-diff-length)

	(cond ;; If one of the regions is empty (or 2 in 3way comparison)
	      ;; then don't refine.
	      ;; If the region happens to be entirely whitespace or empty then
	      ;; mark as such.
	      ((> (length (delq nil (list empty-A empty-B empty-C))) 1)
	       (if (and (ediff-looks-like-combined-merge n)
			ediff-merge-job)
		   (ediff-set-fine-overlays-in-one-buffer 'C nil n))
	       (if ediff-3way-comparison-job
		   (ediff-message-if-verbose
		    "Region %d is empty in all buffers but %S"
		    (1+ n)
		    (cond ((not empty-A) 'A)
			  ((not empty-B) 'B)
			  ((not empty-C) 'C)))
		 (ediff-message-if-verbose
		  "Region %d in buffer %S is empty"
		  (1+ n)
		  (cond (empty-A 'A)
			(empty-B 'B)
			(empty-C 'C)))
		 )
	       ;; if all regions happen to be whitespace
	       (if (and whitespace-A whitespace-B whitespace-C)
		   ;; mark as space only
		   (ediff-mark-diff-as-space-only n t)
		 ;; if some regions are white and others don't, then mark as
		 ;; non-white-space-only
		 (ediff-mark-diff-as-space-only n nil)))

	      ;; don't compute fine diffs if diff vector exists
	      ((and (eq flag 'noforce) (ediff-get-fine-diff-vector n 'A))
	       (if (ediff-no-fine-diffs-p n)
		   (message
		    "Only white-space differences in region %d %s"
		    (1+ n)
		    (cond ((eq (ediff-no-fine-diffs-p n) 'A)
			   "in buffers B & C")
			  ((eq (ediff-no-fine-diffs-p n) 'B)
			   "in buffers A & C")
			  ((eq (ediff-no-fine-diffs-p n) 'C)
			   "in buffers A & B")
			  (t "")))))
	      ;; don't compute fine diffs for this region
	      ((eq flag 'skip)
	       (or (ediff-get-fine-diff-vector n 'A)
		   (memq ediff-auto-refine '(off nix))
		   (ediff-message-if-verbose
		    "Region %d exceeds the auto-refinement limit. Type `%s' to refine"
		    (1+ n)
		    (substitute-command-keys
		     "\\[ediff-make-or-kill-fine-diffs]")
		    )))
	      (t
	       ;; recompute fine diffs
	       (ediff-wordify
		(ediff-get-diff-posn 'A 'beg n)
		(ediff-get-diff-posn 'A 'end n)
		ediff-buffer-A
		tmp-buffer
		ediff-control-buffer)
	       (setq file-A
		     (ediff-make-temp-file tmp-buffer "fineDiffA" file-A))

	       (ediff-wordify
		(ediff-get-diff-posn 'B 'beg n)
		(ediff-get-diff-posn 'B 'end n)
		ediff-buffer-B
		tmp-buffer
		ediff-control-buffer)
	       (setq file-B
		     (ediff-make-temp-file tmp-buffer "fineDiffB" file-B))

	       (if ediff-3way-job
		   (progn
		     (ediff-wordify
		      (ediff-get-diff-posn 'C 'beg n)
		      (ediff-get-diff-posn 'C 'end n)
		      ediff-buffer-C
		      tmp-buffer
		      ediff-control-buffer)
		     (setq file-C
			   (ediff-make-temp-file
			    tmp-buffer "fineDiffC" file-C))))

	       ;; save temp file names.
	       (setq ediff-temp-file-A file-A
		     ediff-temp-file-B file-B
		     ediff-temp-file-C file-C)

	       ;; set the new vector of fine diffs, if none exists
	       (cond ((and ediff-3way-job whitespace-A)
		      (ediff-setup-fine-diff-regions nil file-B file-C n))
		     ((and ediff-3way-job whitespace-B)
		      (ediff-setup-fine-diff-regions file-A nil file-C n))
		     ((and ediff-3way-job
			   ;; In merge-jobs, whitespace-C is t, since
			   ;; ediff-empty-diff-region-p returns t in this case
			   whitespace-C)
		      (ediff-setup-fine-diff-regions file-A file-B nil n))
		     (t
		      (ediff-setup-fine-diff-regions file-A file-B file-C n)))

	       (setq cumulative-fine-diff-length
		     (+ (length (ediff-get-fine-diff-vector n 'A))
			(length (ediff-get-fine-diff-vector n 'B))
			;; in merge jobs, the merge buffer is never refined
			(if (and file-C (not ediff-merge-job))
			    (length (ediff-get-fine-diff-vector n 'C))
			  0)))

	       (cond ((or
		       ;; all regions are white space
		       (and whitespace-A whitespace-B whitespace-C)
		       ;; none is white space and no fine diffs detected
		       (and (not whitespace-A)
			    (not whitespace-B)
			    (not (and ediff-3way-job whitespace-C))
			    (eq cumulative-fine-diff-length 0)))
		      (ediff-mark-diff-as-space-only n t)
		      (ediff-message-if-verbose
		       "Only white-space differences in region %d" (1+ n)))
		     ((eq cumulative-fine-diff-length 0)
		      (ediff-message-if-verbose
		       "Only white-space differences in region %d %s"
		       (1+ n)
		       (cond (whitespace-A (ediff-mark-diff-as-space-only n 'A)
					   "in buffers B & C")
			     (whitespace-B (ediff-mark-diff-as-space-only n 'B)
					   "in buffers A & C")
			     (whitespace-C (ediff-mark-diff-as-space-only n 'C)
					   "in buffers A & B"))))
		     (t
		      (ediff-mark-diff-as-space-only n nil)))
	       )
	      ) ; end cond
	(ediff-set-fine-diff-properties n)
	)))

;; Interface to ediff-make-fine-diffs. Checks for auto-refine limit, etc.
(defun ediff-install-fine-diff-if-necessary (n)
  (cond ((and (eq ediff-auto-refine 'on)
	      ediff-use-faces
	      (not (eq ediff-highlighting-style 'off))
	      (not (eq ediff-highlighting-style 'ascii)))
	 (if (and
	      (> ediff-auto-refine-limit
		 (- (ediff-get-diff-posn 'A 'end n)
		    (ediff-get-diff-posn 'A 'beg n)))
	      (> ediff-auto-refine-limit
		 (- (ediff-get-diff-posn 'B 'end n)
		    (ediff-get-diff-posn 'B 'beg n))))
	     (ediff-make-fine-diffs n 'noforce)
	   (ediff-make-fine-diffs n 'skip)))

	;; highlight iff fine diffs already exist
	((eq ediff-auto-refine 'off)
	 (ediff-make-fine-diffs n 'skip))))


;; if fine diff vector is not set for diff N, then do nothing
(defun ediff-set-fine-diff-properties (n &optional default)
  (or (not (ediff-has-face-support-p))
      (< n 0)
      (>= n ediff-number-of-differences)
      ;; when faces are supported, set faces and priorities of fine overlays
      (progn
	(ediff-set-fine-diff-properties-in-one-buffer 'A n default)
	(ediff-set-fine-diff-properties-in-one-buffer 'B n default)
	(if ediff-3way-job
	    (ediff-set-fine-diff-properties-in-one-buffer 'C n default)))))

(defun ediff-set-fine-diff-properties-in-one-buffer (buf-type
						     n &optional default)
  (let ((fine-diff-vector  (ediff-get-fine-diff-vector n buf-type))
	(face (if default
		  'default
		(face-name
		 (ediff-get-symbol-from-alist
		  buf-type ediff-fine-diff-face-alist))))
	(priority (if default
		      0
		    (1+ (or (ediff-overlay-get
			     (symbol-value
			      (ediff-get-symbol-from-alist
			       buf-type
			       ediff-current-diff-overlay-alist))
			     'priority)
			    0)))))
    (mapcar (lambda (overl)
	      (ediff-set-overlay-face overl face)
	      (ediff-overlay-put overl 'priority priority))
	    fine-diff-vector)))

;; Set overlays over the regions that denote delimiters
(defun ediff-set-fine-overlays-for-combined-merge (diff-list reg-num)
  (let (overlay overlay-list)
    (while diff-list
      (condition-case nil
	  (setq overlay
		(ediff-make-bullet-proof-overlay
		 (nth 0 diff-list) (nth 1 diff-list) ediff-buffer-C))
	(error ""))
      (setq overlay-list (cons overlay overlay-list))
      (if (> (length diff-list) 1)
	  (setq diff-list (cdr (cdr diff-list)))
	(error "ediff-set-fine-overlays-for-combined-merge: corrupt list of
delimiter regions"))
      )
    (setq overlay-list (reverse overlay-list))
    (ediff-set-fine-diff-vector
     reg-num 'C (apply 'vector overlay-list))
    ))


;; Convert diff list to overlays for a given DIFF-REGION
;; in buffer of type BUF-TYPE
(defun ediff-set-fine-overlays-in-one-buffer (buf-type diff-list region-num)
  (let* ((current-diff -1)
	 (reg-start (ediff-get-diff-posn buf-type 'beg region-num))
	 (buff (ediff-get-buffer buf-type))
	 (ctl-buf ediff-control-buffer)
	 combined-merge-diff-list
	 diff-overlay-list list-element
	 begin end overlay)

    (ediff-clear-fine-differences-in-one-buffer region-num buf-type)
    (setq diff-list (cdr diff-list)) ; discard list type (words or points)
    (ediff-with-current-buffer buff (goto-char reg-start))

    ;; if it is a combined merge then set overlays in buff C specially
    (if (and ediff-merge-job (eq buf-type 'C)
	     (setq combined-merge-diff-list
		   (ediff-looks-like-combined-merge region-num)))
	(ediff-set-fine-overlays-for-combined-merge
	 combined-merge-diff-list region-num)
      ;; regular fine diff
      (while diff-list
	(setq current-diff (1+ current-diff)
	      list-element (car diff-list)
	      begin 	 (aref list-element (cond ((eq buf-type 'A) 0)
						  ((eq buf-type 'B) 2)
						  (t 4)))  ; buf C
	      end 	 (aref list-element (cond ((eq buf-type 'A) 1)
						  ((eq buf-type 'B) 3)
						  (t 5)))) ; buf C
	(if (not (or begin end))
	    () ; skip this diff
	  ;; Put overlays at appropriate places in buffers
	  ;; convert lines to points, if necessary
	  (ediff-with-current-buffer ctl-buf
	    (setq begin (ediff-goto-word (1+ begin) buff)
		  end (ediff-goto-word end buff 'end)))
	  (setq overlay (ediff-make-bullet-proof-overlay begin end buff))
	  ;; record all overlays for this difference region
	  (setq diff-overlay-list (nconc diff-overlay-list (list overlay))))

	(setq diff-list (cdr diff-list))
	) ; while
      ;; convert the list of difference information into a vector
      ;; for fast access
      (ediff-set-fine-diff-vector
       region-num buf-type (vconcat diff-overlay-list))
      )))


(defsubst ediff-convert-fine-diffs-to-overlays (diff-list region-num)
  (ediff-set-fine-overlays-in-one-buffer 'A diff-list region-num)
  (ediff-set-fine-overlays-in-one-buffer 'B diff-list region-num)
  (if ediff-3way-job
      (ediff-set-fine-overlays-in-one-buffer 'C diff-list region-num)
    ))


;; Stolen from emerge.el
(defun ediff-get-diff3-group (file)
  ;; This save-excursion allows ediff-get-diff3-group to be called for the
  ;; various groups of lines (1, 2, 3) in any order, and for the lines to
  ;; appear in any order.  The reason this is necessary is that Gnu diff3
  ;; can produce the groups in the order 1, 2, 3 or 1, 3, 2.
  (save-excursion
    (re-search-forward
     (concat "^" file ":\\([0-9]+\\)\\(,\\([0-9]+\\)\\)?\\([ac]\\)\C-m?$"))
    (beginning-of-line 2)
    ;; treatment depends on whether it is an "a" group or a "c" group
    (if (string-equal (buffer-substring (match-beginning 4) (match-end 4)) "c")
	;; it is a "c" group
	(if (match-beginning 2)
	    ;; it has two numbers
	    (list (string-to-number
		   (buffer-substring (match-beginning 1) (match-end 1)))
		  (1+ (string-to-number
		       (buffer-substring (match-beginning 3) (match-end 3)))))
	  ;; it has one number
	  (let ((x (string-to-number
		    (buffer-substring (match-beginning 1) (match-end 1)))))
	    (list x (1+ x))))
      ;; it is an "a" group
      (let ((x (1+ (string-to-number
		    (buffer-substring (match-beginning 1) (match-end 1))))))
	(list x x)))))


;; If WORD-MODE, construct vector of diffs using word numbers.
;; Else, use point values.
;; WORD-MODE also tells if we are in the word-mode or not.
;; If THREE-WAY-COMP, then it is a 3-way comparison. Else, it is merging
;; with ancestor, in which case buffer-C contents is identical to buffer-A/B,
;; contents (unless buffer-A is narrowed) depending on ediff-default-variant's
;; value.
;; BOUNDS specifies visibility bounds to use.
(defun ediff-extract-diffs3 (diff-buffer word-mode three-way-comp
					  &optional bounds)
  (let ((A-buffer ediff-buffer-A)
	(B-buffer ediff-buffer-B)
	(C-buffer ediff-buffer-C)
	(anc-buffer ediff-ancestor-buffer)
	(a-prev 1) ; needed to set the first diff line correctly
	(b-prev 1)
	(c-prev 1)
	(anc-prev 1)
	diff-list shift-A shift-B shift-C
	)

    ;; diff list contains word numbers or points, depending on word-mode
    (setq diff-list (cons (if word-mode 'words 'points)
			  diff-list))
    (if bounds
	(setq shift-A
	      (ediff-overlay-start
	       (ediff-get-value-according-to-buffer-type 'A bounds))
	      shift-B
	      (ediff-overlay-start
	       (ediff-get-value-according-to-buffer-type 'B bounds))
	      shift-C
	      (if three-way-comp
		  (ediff-overlay-start
		   (ediff-get-value-according-to-buffer-type 'C bounds)))))

    ;; reset point in buffers A, B, C
    (ediff-with-current-buffer A-buffer
      (goto-char (if shift-A shift-A (point-min))))
    (ediff-with-current-buffer B-buffer
      (goto-char (if shift-B shift-B (point-min))))
    (if three-way-comp
	(ediff-with-current-buffer C-buffer
	  (goto-char (if shift-C shift-C (point-min)))))
    (if (ediff-buffer-live-p anc-buffer)
	(ediff-with-current-buffer anc-buffer
	  (goto-char (point-min))))

    (ediff-with-current-buffer diff-buffer
      (goto-char (point-min))
      (while (re-search-forward ediff-match-diff3-line nil t)
	;; leave point after matched line
       (beginning-of-line 2)
       (let ((agreement (buffer-substring (match-beginning 1) (match-end 1))))
	 ;; if the files A and B are the same and not 3way-comparison,
	 ;; ignore the difference
	 (if (or three-way-comp (not (string-equal agreement "3")))
	     (let* ((a-begin (car (ediff-get-diff3-group "1")))
		    (a-end  (nth 1 (ediff-get-diff3-group "1")))
		    (b-begin (car (ediff-get-diff3-group "2")))
		    (b-end (nth 1 (ediff-get-diff3-group "2")))
		    (c-or-anc-begin (car (ediff-get-diff3-group "3")))
		    (c-or-anc-end (nth 1 (ediff-get-diff3-group "3")))
		    (state-of-merge
		     (cond ((string-equal agreement "1") 'prefer-A)
			   ((string-equal agreement "2") 'prefer-B)
			   (t ediff-default-variant)))
		    (state-of-diff-merge
		     (if (memq state-of-merge '(default-A prefer-A)) 'B 'A))
		    (state-of-diff-comparison
		     (cond ((string-equal agreement "1") 'A)
			   ((string-equal agreement "2") 'B)
			   ((string-equal agreement "3") 'C)))
		    state-of-ancestor
		    c-begin c-end
		    a-begin-pt a-end-pt
		    b-begin-pt b-end-pt
		    c-begin-pt c-end-pt
		    anc-begin-pt anc-end-pt)

	       (setq state-of-ancestor
		     (= c-or-anc-begin c-or-anc-end))

	       (cond (three-way-comp
		      (setq c-begin c-or-anc-begin
			    c-end c-or-anc-end))
		     ((eq ediff-default-variant 'default-B)
		      (setq c-begin b-begin
			    c-end b-end))
		     (t
		      (setq c-begin a-begin
			    c-end a-end)))

	       ;; compute main diff vector
	       (if word-mode
		   ;; make diff-list contain word numbers
		   (setq diff-list
			 (nconc diff-list
				(list (vector
				       (- a-begin a-prev) (- a-end a-begin)
				       (- b-begin b-prev) (- b-end b-begin)
				       (- c-begin c-prev) (- c-end c-begin)
				       nil nil ; dummy ancestor
				       nil     ; state of diff
				       nil     ; state of merge
				       nil     ; state of ancestor
				       )))
			 a-prev a-end
			 b-prev b-end
			 c-prev c-end)
		 ;; else convert lines to points
		 (ediff-with-current-buffer A-buffer
		   (let ((longlines-mode-val
			  (if (and (boundp 'longlines-mode) longlines-mode) 1 0)))
		     ;; we must disable and then restore longlines-mode
		     (if (eq longlines-mode-val 1)
			 (longlines-mode 0))
		     (forward-line (- a-begin a-prev))
		     (setq a-begin-pt (point))
		     (forward-line (- a-end a-begin))
		     (setq a-end-pt (point)
			   a-prev a-end)
		     (if (eq longlines-mode-val 1)
			 (longlines-mode longlines-mode-val))
		     ))
		 (ediff-with-current-buffer B-buffer
		   (let ((longlines-mode-val
			  (if (and (boundp 'longlines-mode) longlines-mode) 1 0)))
		     (if (eq longlines-mode-val 1)
			 (longlines-mode 0))
		     (forward-line (- b-begin b-prev))
		     (setq b-begin-pt (point))
		     (forward-line (- b-end b-begin))
		     (setq b-end-pt (point)
			   b-prev b-end)
		     (if (eq longlines-mode-val 1)
			 (longlines-mode longlines-mode-val))
		     ))
		 (ediff-with-current-buffer C-buffer
		   (let ((longlines-mode-val
			  (if (and (boundp 'longlines-mode) longlines-mode) 1 0)))
		     (if (eq longlines-mode-val 1)
			 (longlines-mode 0))
		     (forward-line (- c-begin c-prev))
		     (setq c-begin-pt (point))
		     (forward-line (- c-end c-begin))
		     (setq c-end-pt (point)
			   c-prev c-end)
		     (if (eq longlines-mode-val 1)
			 (longlines-mode longlines-mode-val))
		     ))
		 (if (ediff-buffer-live-p anc-buffer)
		     (ediff-with-current-buffer anc-buffer
		       (let ((longlines-mode-val
			      (if (and (boundp 'longlines-mode) longlines-mode) 1 0)))
			 (if (eq longlines-mode-val 1)
			     (longlines-mode 0))
			 (forward-line (- c-or-anc-begin anc-prev))
			 (setq anc-begin-pt (point))
			 (forward-line (- c-or-anc-end c-or-anc-begin))
			 (setq anc-end-pt (point)
			       anc-prev c-or-anc-end)
			 (if (eq longlines-mode-val 1)
			     (longlines-mode longlines-mode-val))
			 )))
		 (setq diff-list
		       (nconc
			diff-list
			;; if comparing with ancestor, then there also is a
			;; state-of-difference marker
			(if three-way-comp
			    (list (vector
				   a-begin-pt a-end-pt
				   b-begin-pt b-end-pt
				   c-begin-pt c-end-pt
				   nil nil ; ancestor begin/end
				   state-of-diff-comparison
				   nil	; state of merge
				   nil  ; state of ancestor
				   ))
			  (list (vector a-begin-pt a-end-pt
					b-begin-pt b-end-pt
					c-begin-pt c-end-pt
					anc-begin-pt anc-end-pt
					state-of-diff-merge
					state-of-merge
					state-of-ancestor
					)))
			)))
	       ))

	 ))) ; end ediff-with-current-buffer
    diff-list
    ))

;; Generate the difference vector and overlays for three files
;; File-C is either the third file to compare (in case of 3-way comparison)
;; or it is the ancestor file.
(defun ediff-setup-diff-regions3 (file-A file-B file-C)
  (or (ediff-buffer-live-p ediff-diff-buffer)
      (setq ediff-diff-buffer
	    (get-buffer-create (ediff-unique-buffer-name "*ediff-diff" "*"))))

  (message "Computing differences ...")
  (ediff-exec-process ediff-diff3-program ediff-diff-buffer 'synchronize
		      ediff-diff3-options file-A file-B file-C)

  (ediff-prepare-error-list ediff-diff3-ok-lines-regexp ediff-diff-buffer)
  ;;(message "Computing differences ... done")
  (ediff-convert-diffs-to-overlays
   (ediff-extract-diffs3
    ediff-diff-buffer
    ediff-word-mode ediff-3way-comparison-job ediff-narrow-bounds)
   ))


;; Execute PROGRAM asynchronously, unless OS/2, Windows-*, or DOS, or unless
;; SYNCH is non-nil.  BUFFER must be a buffer object, and must be alive.  The
;; OPTIONS arg is a list of options to pass to PROGRAM. It may be a blank
;; string.  All elements in FILES must be strings.  We also delete nil from
;; args.
(defun ediff-exec-process (program buffer synch options &rest files)
  (let ((data (match-data))
	(coding-system-for-read ediff-coding-system-for-read)
	args)
    (setq args (append (split-string options) files))
    (setq args (delete "" (delq nil args))) ; delete nil and "" from arguments
    ;; the --binary option, if present, should be used only for buffer jobs
    ;; or for refining the differences
    (or (string-match "buffer" (symbol-name ediff-job-name))
	(eq buffer ediff-fine-diff-buffer)
	(setq args (delete "--binary" args)))
    (unwind-protect
	(let ((directory default-directory)
	      proc)
	  (save-excursion
	    (set-buffer buffer)
	    (erase-buffer)
	    (setq default-directory directory)
	    (if (or (memq system-type '(emx ms-dos windows-nt windows-95))
		    synch)
		;; In OS/2 (emx) do it synchronously, since OS/2 doesn't let us
		;; delete files used by other processes. Thus, in ediff-buffers
		;; and similar functions, we can't delete temp files because
		;; they might be used by the asynch process that computes
		;; custom diffs. So, we have to wait till custom diff
		;; subprocess is done.
		;; Similarly for Windows-*
		;; In DOS, must synchronize because DOS doesn't have
		;; asynchronous processes.
		(apply 'call-process program nil buffer nil args)
	      ;; On other systems, do it asynchronously.
	      (setq proc (get-buffer-process buffer))
	      (if proc (kill-process proc))
	      (setq proc
		    (apply 'start-process "Custom Diff" buffer program args))
	      (setq mode-line-process '(":%s"))
	      (set-process-sentinel proc 'ediff-process-sentinel)
	      (set-process-filter proc 'ediff-process-filter)
	      )))
      (store-match-data data))))

;; This is shell-command-filter from simple.el in Emacs.
;; Copied here because XEmacs doesn't have it.
(defun ediff-process-filter (proc string)
  ;; Do save-excursion by hand so that we can leave point numerically unchanged
  ;; despite an insertion immediately after it.
  (let* ((obuf (current-buffer))
         (buffer (process-buffer proc))
         opoint
         (window (get-buffer-window buffer))
         (pos (window-start window)))
    (unwind-protect
        (progn
          (set-buffer buffer)
          (or (= (point) (point-max))
              (setq opoint (point)))
          (goto-char (point-max))
          (insert-before-markers string))
      ;; insert-before-markers moved this marker: set it back.
      (set-window-start window pos)
      ;; Finish our save-excursion.
      (if opoint
          (goto-char opoint))
      (set-buffer obuf))))

;; like shell-command-sentinel but doesn't print an exit status message
;; we do this because diff always exits with status 1, if diffs are found
;; so shell-command-sentinel displays a confusing message to the user
(defun ediff-process-sentinel (process signal)
  (if (and (memq (process-status process) '(exit signal))
           (buffer-name (process-buffer process)))
      (progn
        (save-excursion
          (set-buffer (process-buffer process))
          (setq mode-line-process nil))
        (delete-process process))))


;;; Word functions used to refine the current diff

(defvar ediff-forward-word-function 'ediff-forward-word
  "*Function to call to move to the next word.
Used for splitting difference regions into individual words.")
(make-variable-buffer-local 'ediff-forward-word-function)

(defvar ediff-whitespace " \n\t\f"
  "*Characters constituting white space.
These characters are ignored when differing regions are split into words.")
(make-variable-buffer-local 'ediff-whitespace)

(defvar ediff-word-1
  (ediff-cond-compile-for-xemacs-or-emacs "a-zA-Z---_" "-[:word:]_")
  "*Characters that constitute words of type 1.
More precisely, [ediff-word-1] is a regexp that matches type 1 words.
See `ediff-forward-word' for more details.")
(make-variable-buffer-local 'ediff-word-1)

(defvar ediff-word-2 "0-9.,"
  "*Characters that constitute words of type 2.
More precisely, [ediff-word-2] is a regexp that matches type 2 words.
See `ediff-forward-word' for more details.")
(make-variable-buffer-local 'ediff-word-2)

(defvar ediff-word-3 "`'?!:;\"{}[]()"
  "*Characters that constitute words of type 3.
More precisely, [ediff-word-3] is a regexp that matches type 3 words.
See `ediff-forward-word' for more details.")
(make-variable-buffer-local 'ediff-word-3)

(defvar ediff-word-4
  (concat "^" ediff-word-1 ediff-word-2 ediff-word-3 ediff-whitespace)
  "*Characters that constitute words of type 4.
More precisely, [ediff-word-4] is a regexp that matches type 4 words.
See `ediff-forward-word' for more details.")
(make-variable-buffer-local 'ediff-word-4)

;; Split region along word boundaries. Each word will be on its own line.
;; Output to buffer out-buffer.
(defun ediff-forward-word ()
  "Move point one word forward.
There are four types of words, each of which consists entirely of
characters in `ediff-word-1', `ediff-word-2', `ediff-word-3', or
`ediff-word-4'.  Words are recognized by passing these one after another as
arguments to `skip-chars-forward'."
  (or (> (+ (skip-chars-forward ediff-word-1)
	    (skip-syntax-forward "w"))
	 0)
      (> (skip-chars-forward ediff-word-2) 0)
      (> (skip-chars-forward ediff-word-3) 0)
      (> (skip-chars-forward ediff-word-4) 0)
      ))


(defun ediff-wordify (beg end in-buffer out-buffer &optional control-buf)
  (let ((forward-word-function
	 ;; eval in control buf to let user create local versions for
	 ;; different invocations
	 (if control-buf
	     (ediff-with-current-buffer control-buf
	       ediff-forward-word-function)
	   ediff-forward-word-function))
	inbuf-syntax-tbl sv-point diff-string)
    (save-excursion
     (set-buffer in-buffer)
     (setq inbuf-syntax-tbl
	   (if control-buf
	       (ediff-with-current-buffer control-buf
		 ediff-syntax-table)
	     (syntax-table)))
     (setq diff-string (buffer-substring-no-properties beg end))

     (set-buffer out-buffer)
     ;; Make sure that temp buff syntax table is the same as the original buf
     ;; syntax tbl, because we use ediff-forward-word in both and
     ;; ediff-forward-word depends on the syntax classes of characters.
     (set-syntax-table inbuf-syntax-tbl)
     (erase-buffer)
     (insert diff-string)
     (goto-char (point-min))
     (skip-chars-forward ediff-whitespace)
     (delete-region (point-min) (point))

     (while (not (eobp))
       (funcall forward-word-function)
       (setq sv-point (point))
       (skip-chars-forward ediff-whitespace)
       (delete-region sv-point (point))
       (insert "\n")))))

;; copy string specified as BEG END from IN-BUF to OUT-BUF
(defun ediff-copy-to-buffer (beg end in-buffer out-buffer)
  (with-current-buffer out-buffer
    (erase-buffer)
    (insert-buffer-substring in-buffer beg end)
    (goto-char (point-min))))


;; goto word #n starting at current position in buffer `buf'
;; For ediff, a word is determined by ediff-forward-word-function
;; If `flag' is non-nil, goto the end of the n-th word.
(defun ediff-goto-word (n buf &optional flag)
  ;; remember val ediff-forward-word-function has in ctl buf
  (let ((fwd-word-fun ediff-forward-word-function)
	(syntax-tbl ediff-syntax-table))
    (ediff-with-current-buffer buf
      (skip-chars-forward ediff-whitespace)
      (ediff-with-syntax-table syntax-tbl
	(while (> n 1)
	  (funcall fwd-word-fun)
	  (skip-chars-forward ediff-whitespace)
	  (setq n (1- n)))
	(if (and flag (> n 0))
	    (funcall fwd-word-fun)))
      (point))))

(defun ediff-same-file-contents (f1 f2)
  "Return t if files F1 and F2 have identical contents."
  (if (and (not (file-directory-p f1))
           (not (file-directory-p f2)))
      (let ((res
	     (apply 'call-process ediff-cmp-program nil nil nil
		    (append ediff-cmp-options (list f1 f2)))))
	(and (numberp res) (eq res 0))))
  )


(defun ediff-same-contents (d1 d2 &optional filter-re)
  "Returns t iff D1 and D2 have the same content.
D1 and D2 can either be both directories or both regular files.
Symlinks and the likes are not handled.
If FILTER-RE is non-nil, recursive checking in directories
affects only files whose names match the expression."
  ;; Normalize empty filter RE to nil.
  (unless (> (length filter-re) 0) (setq filter-re nil))
  ;; Indicate progress
  (message "Comparing '%s' and '%s' modulo '%s'" d1 d2 filter-re)
  (cond
   ;; D1 & D2 directories => recurse
   ((and (file-directory-p d1)
         (file-directory-p d2))
    (if (null ediff-recurse-to-subdirectories)
	(if (y-or-n-p "Compare subdirectories recursively? ")
	    (setq ediff-recurse-to-subdirectories 'yes)
	  (setq ediff-recurse-to-subdirectories 'no)))
    (if (eq ediff-recurse-to-subdirectories 'yes)
	(let* ((all-entries-1 (directory-files d1 t filter-re))
	       (all-entries-2 (directory-files d2 t filter-re))
	       (entries-1 (ediff-delete-all-matches "^\\.\\.?$" all-entries-1))
	       (entries-2 (ediff-delete-all-matches "^\\.\\.?$" all-entries-2))
	       )

	  (ediff-same-file-contents-lists entries-1 entries-2 filter-re)
	  ))
    ) ; end of the directories case
   ;; D1 & D2 are both files => compare directly
   ((and (file-regular-p d1)
         (file-regular-p d2))
    (ediff-same-file-contents d1 d2))
   ;; Otherwise => false: unequal contents
   )
  )

;; If lists have the same length and names of files are pairwise equal
;; (removing the directories) then compare contents pairwise.
;; True if all contents are the same; false otherwise
(defun ediff-same-file-contents-lists (entries-1 entries-2 filter-re)
  ;; First, check only the names (works quickly and ensures a
  ;; precondition for subsequent code)
  (if (and (= (length entries-1) (length entries-2))
	   (equal (mapcar 'file-name-nondirectory entries-1)
		  (mapcar 'file-name-nondirectory entries-2)))
      ;; With name equality established, compare the entries
      ;; through recursion.
      (let ((continue t))
	(while (and entries-1 continue)
	  (if (ediff-same-contents
	       (car entries-1) (car entries-2) filter-re)
	      (setq entries-1 (cdr entries-1)
		    entries-2 (cdr entries-2))
	    (setq continue nil))
	  )
	;; if reached the end then lists are equal
	(null entries-1))
    )
  )


;; ARG1 is a regexp, ARG2 is a list of full-filenames
;; Delete all entries that match the regexp
(defun ediff-delete-all-matches (regex file-list-list)
  (let (result elt)
    (while file-list-list
      (setq elt (car file-list-list))
      (or (string-match regex (file-name-nondirectory elt))
	  (setq result (cons elt result)))
      (setq file-list-list (cdr file-list-list)))
    (reverse result)))


;;; Local Variables:
;;; eval: (put 'ediff-defvar-local 'lisp-indent-hook 'defun)
;;; eval: (put 'ediff-with-current-buffer 'lisp-indent-hook 1)
;;; eval: (put 'ediff-with-current-buffer 'edebug-form-spec '(form body))
;;; End:

;;; arch-tag: a86d448e-58d7-4572-a1d9-fdedfa22f648
;;; ediff-diff.el ends here