Re: auto-enca.el - automatically detect coding system with Enca

[Dmitriyi Paduchikh]

This version fixes problem which arises when file being opened does
not exist.

;;; auto-enca.el --- automatically detect coding system with Enca

;; This code is public domain. Use it as is, at your own risk.
;; I tried it with Emacs 22, and it seems that it gives quite
;; satisfying results, but YMMV.
;; 
;; The following function, enca-detect-coding, is meant to be placed at
;; file-coding-system-alist in order to detect coding system of files
;; when they are opened. This happens by running Enca on the file.
;; 
;; Enca (Extremely Naive Charset Analyser) can be found at the address
;; http://trific.ath.cx/Ftp/enca/
;; 
;; To get this function working, put the file at some place in your
;; load-path, compile, and add something like this into .emacs:
;; 
;; (when (load "auto-enca" 'noerror)
;;   (modify-coding-system-alist 'file "" 'enca-detect-coding))
;; 
;; With thanks to Kenichi Handa for nice suggestions.
;; 
;; -- 
;; Dmitriyi Paduchikh

;;; Code:

(defun enca-detect-coding (arg)
  (if (not (and (eq (car arg) 'insert-file-contents) (nth 1 arg)))
      'undecided
    (let* ((target (nth 1 arg))
          (enca-buffer (generate-new-buffer " *enca*")) 
          (charset nil)
          (run-enca (if (atom target)
                        (lambda ()
                          (if (file-exists-p target)
                              (call-process "enca" target
                                            enca-buffer nil "-m")
                            1))
                      (lambda ()
                        (with-current-buffer (cdr target)
                          (let ((coding-system-for-write 'no-conversion)
                                (size (min 20480 (- (point-max)
                                                    (point-min)))))
                            (call-process-region
                             (point-min) (+ (point-min) size)
                             "enca" nil enca-buffer nil "-m")))))))
      (unwind-protect
          (when (= 0 (funcall run-enca))
            (with-current-buffer enca-buffer
              (goto-char 1)
              (downcase-region 1 (point-max))
              (skip-chars-forward "\t\n\f\r ")
              (delete-region 1 (point))
              (when (looking-at "\\(ibm\\)[0-9]")
                (replace-match "cp" t t nil 1))
              (skip-chars-forward "^\t\n\f\r ")
              (setq charset (intern-soft (buffer-substring 1 (point))))))
        (kill-buffer enca-buffer))
      (or (and (not (memq charset '(nil unknown us-ascii)))
               (coding-system-p charset)
               charset)
          'undecided))))