Some fixes to follow coding conventions.

[emacs.git] / lisp / ediff-diff.el

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

;; Copyright (C) 1994, 1995, 1996, 1997 Free Software Foundation, Inc.

;; Author: Michael Kifer <kifer@cs.sunysb.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., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;;; Code:

(provide 'ediff-diff)

;; compiler pacifier
(defvar ediff-default-variant)

(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)

(defcustom ediff-coding-system-for-read 'raw-text
  "*The coding system for read to use when running the diff program as a subprocess. 
In most cases, the default will do. However, under certain circumstances in
Windows NT/98/95 you might need to use something like 'raw-text-dos here.
So, if the output that your diff program sends to Emacs contains extra ^M's,
you might need to experiment here, if the default or 'raw-text-dos doesn't
work."
  :type 'symbol
  :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)
  (zerop (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 GNUS diff is used as
`ediff-cmp-program', then the most useful options are `-I' RE, to
ignore changes whose lines all match RE."
  :type '(repeat string)
  :group 'ediff-diff)

(defcustom ediff-diff-options ""
  "*Options to pass to `ediff-diff-program'. 
If diff\(1\) 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 "^====\\(.?\\)$"
  "Pattern to match lines produced by diff3 that describe differences.")
(defcustom ediff-diff3-options ""  
  "*Options to pass to `ediff-diff3-program'."
  :set 'ediff-reset-diff-options
  :type 'string
  :group 'ediff-diff)
(defcustom ediff-diff3-ok-lines-regexp
  "^\\([1-3]:\\|====\\|  \\|.*Warning *:\\|.*No newline\\|.*missing newline\\|^\C-m$\\)"
  "*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)
  (if (string-match "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-int (buffer-substring (match-beginning 1)
                                                        (match-end 1))))
              (a-end  (let ((b (match-beginning 3))
                            (e (match-end 3)))
                        (if b
                            (string-to-int (buffer-substring b e))
                          a-begin)))
              (diff-type (buffer-substring (match-beginning 4) (match-end 4)))
              (b-begin (string-to-int (buffer-substring (match-beginning 5)
                                                        (match-end 5))))
              (b-end (let ((b (match-beginning 7))
                           (e (match-end 7)))
                       (if b
                           (string-to-int (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
             (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))
           (ediff-with-current-buffer B-buffer
             (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 (ediff-buffer-live-p C-buffer)
               (ediff-with-current-buffer C-buffer
                 (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)))
           (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))
         ;; 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))
            (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 ((eq ediff-auto-refine 'on)
         (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))
         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
          (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))
      )))


;; 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]\\)$"))
    (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-int
                   (buffer-substring (match-beginning 1) (match-end 1)))
                  (1+ (string-to-int
                       (buffer-substring (match-beginning 3) (match-end 3)))))
          ;; it has one number
          (let ((x (string-to-int
                    (buffer-substring (match-beginning 1) (match-end 1)))))
            (list x (1+ x))))
      ;; it is an "a" group
      (let ((x (1+ (string-to-int
                    (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
                   (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))
                 (ediff-with-current-buffer B-buffer
                   (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))
                 (ediff-with-current-buffer C-buffer
                   (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 (ediff-buffer-live-p anc-buffer)
                     (ediff-with-current-buffer anc-buffer
                       (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)))
                 (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.")

(defvar ediff-whitespace " \n\t\f"
  "*Characters constituting white space.
These characters are ignored when differing regions are split into words.")

(defvar ediff-word-1 "a-zA-Z---_"
  "*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.")  

(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.")

(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.")

(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.")  

;; 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 (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 a 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))
       ;; eval in control buf to let user create local versions for
       ;; different invocations
       (if control-buf
           (funcall 
            (ediff-with-current-buffer control-buf
              ediff-forward-word-function))
         (funcall ediff-forward-word-function))
       (setq sv-point (point))
       (skip-chars-forward ediff-whitespace)
       (delete-region sv-point (point))
       (insert "\n")))))
       
;; copy string from BEG END from IN-BUF to OUT-BUF
(defun ediff-copy-to-buffer (beg end in-buffer out-buffer)
  (let (string)
    (save-excursion
      (set-buffer in-buffer)
     (setq string (buffer-substring beg end))

     (set-buffer out-buffer)
     (erase-buffer)
     (insert string)
     (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)
      (while (> n 1)
        (ediff-with-syntax-table syntax-tbl
            (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)
  "T if F1 and F2 have identical contents."
  (let ((res 
         (apply 'call-process ediff-cmp-program nil nil nil
                (append ediff-cmp-options (list f1 f2)))))
    (and (numberp res) (eq res 0))))


;;; 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:


;;; ediff-diff.el ends here