Fix save with adjustment.

superfluous checks to vlf-verify-size when saving.  Fix vlf-revert not
to ask unnecessary.

README.org

@@ -1,8 +1,8 @@
 * View Large Files
 
-An Emacs mode that allows viewing, editing and searching in large
-files in chunks.  Batch size can be adjusted on the fly and bounds the
-memory that is to be used for operations on the file.
+Emacs minor mode that allows viewing, editing and searching large
+files in batches.  Batch size can be adjusted on the fly and bounds
+the memory that is to be used for operations on the file.
 
 This is development version of the GNU ELPA [[http://elpa.gnu.org/packages/vlf][vlf.el]] package.  Here's
 what it does in a nutshell:
@@ -17,6 +17,8 @@ what it does in a nutshell:
 - newly added content is acknowledged if file has changed size
   meanwhile
 - automatic scrolling of batches
+- as VLF is minor mode, font locking and functionality of the
+  respective major mode is also present
 - VLF is added as an option when opening large files
 
 GNU Emacs 23 and 24 are supported.
@@ -41,64 +43,79 @@ integer value), VLF will probably not quite work.
 
 *vlf-batch-size* bounds the memory used for all operations.
 
-** Special mode
-
-VLF is derived from special-mode and keeps all its properties.  For
-example you can directly press digits to enter prefix arguments.
-
-** Change major mode
-
-You can change major mode to whatever you like (for example
-hexl-mode).  Saving will insert contents as intended.  You can return
-to *vlf-mode* too.
-
 * Detail usage
 
+** Applicability
+
+You can control when vlf-mode is invoked or offered as choice with the
+*vlf-application* customization option.  By default it will offer VLF
+when opening large files.  There are also options to never use it (you
+can still call *vlf* command explicitly); to use it without asking for
+large files or to invoke it on all files.  Here's example setup such
+that vlf-mode automatically launches for large files:
+
+#+BEGIN_EXAMPLE
+(custom-set-variables
+ '(vlf-application 'dont-ask))
+#+END_EXAMPLE
+
+** Keymap
+
+All VLF operations are grouped under the *C-c C-v* prefix by default.
+Here's example how to add another prefix (*C-x v*):
+
+#+BEGIN_EXAMPLE
+(eval-after-load "vlf"
+  '(define-key vlf-prefix-map "\C-xv" vlf-mode-map))
+#+END_EXAMPLE
+
 ** Control batch size
 
-*+* and *-* control current batch size by factors of 2.
+*C-c C-v +* and *C-c C-v -* control current batch size by factors
+of 2.
 
 You can also set by hand local variable *vlf-batch-size* and then
-refresh with *g*.
+refresh with *C-c C-v g*.
 
 ** Move around
 
-*M-PgUp* and *M-PgDn* move chunk by chunk.  With positive prefix
-argument they move prefix number of batches.  With negative - append
-prefix number of batches.
+*C-c C-v n* and *C-c C-v p* move batch by batch.  With positive
+prefix argument they move prefix number of batches.  With negative -
+append prefix number of batches.
 
-*[* and *]* take you to the beginning and end of file respectively.
+*C-c C-v SPC* displays batch starting from current point.
 
-*j* jumps to given chunk.  To see where you are in file and how many chunks
-there are (using the current batch size), look at the bracketed part
-of the buffer name, batch size is also there - at the end.
+*C-c C-v [* and *C-c C-v ]* take you to the beginning and end of file
+respectively.
+
+*C-c C-v j* jumps to given chunk.  To see where you are in file and
+how many chunks there are (using the current batch size), look at the
+parenthesized part of the buffer name, batch size is also indicated at
+the end.
 
 ** Search whole file
 
-*s* and *r* search forward and backward respectively over the whole
-file.  This is done chunk by chunk so if you have really huge file -
-you'd better set somewhat bigger batch size beforehand.
+*C-c C-v s* and *C-c C-v r* search forward and backward respectively
+over the whole file.  This is done batch by batch so if you have
+really huge file - you'd better set somewhat bigger batch size
+beforehand.
 
 ** Occur over whole file
 
-*o* builds index for given regular expression just like occur-mode.
-It does this chunk by chunk over the whole file.  Note that even if
-you prematurely stop it with *C-g*, it will still show index of what's
-found so far.
+*C-c C-v o* builds index for given regular expression just like
+*M-x occur*.  It does this batch by batch over the whole file.  Note
+that even if you prematurely stop it with *C-g*, it will still show
+index of what's found so far.
 
 ** Jump to line
 
-*l* jumps to given line in file.  This is done by searching from the
-beginning, so again the bigger current batch size, the quicker.  With
-negative argument, lines are counted from the end of file.
+*C-c C-v l* jumps to given line in file.  This is done by searching
+from the beginning, so again the bigger current batch size, the
+quicker.  With negative argument, lines are counted from the end of
+file.
 
-** Edit
+** Edit and save
 
-*e* enters VLF in edit mode.  If editing doesn't change size of
-the chunk, only this chunk is saved.  Otherwise the remaining part of
-the file is adjusted chunk by chunk, so again you'd better have bigger
-current batch size.  If chunk has been expanded the memory used is
-
-#+BEGIN_EXAMPLE
-(batch size + difference to the original chunk size) x 2
-#+END_EXAMPLE
+If editing doesn't change size of the chunk, only this chunk is saved.
+Otherwise the remaining part of the file is adjusted batch by batch,
+so again you'd better have bigger current batch size.

vlf.el

@@ -2,7 +2,7 @@
 
 ;; Copyright (C) 2006, 2012, 2013  Free Software Foundation, Inc.
 
-;; Version: 0.9.1
+;; Version: 1.2
 ;; Keywords: large files, utilities
 ;; Maintainer: Andrey Kotlarski <m00naticus@gmail.com>
 ;; Authors: 2006 Mathias Dahl <mathias.dahl@gmail.com>
@@ -45,10 +45,23 @@
 
 (defcustom vlf-batch-size 1024
   "Defines how large each batch of file data is (in bytes)."
-  :type 'integer
-  :group 'vlf)
+  :group 'vlf
+  :type 'integer)
 (put 'vlf-batch-size 'permanent-local t)
 
+;;;###autoload
+(defcustom vlf-application 'ask
+  "Determines when `vlf' will be offered on opening files.
+Possible values are: nil to never use it;
+`ask' offer `vlf' when file size is beyond `large-file-warning-threshold';
+`dont-ask' automatically use `vlf' for large files;
+`always' use `vlf' for all files."
+  :group 'vlf
+  :type '(radio (const :format "%v " nil)
+                (const :format "%v " ask)
+                (const :format "%v " dont-ask)
+                (const :format "%v" always)))
+
 ;;; Keep track of file position.
 (defvar vlf-start-pos 0
   "Absolute position of the visible chunk start.")
@@ -62,8 +75,9 @@
 
 (defvar vlf-mode-map
   (let ((map (make-sparse-keymap)))
-    (define-key map [M-next] 'vlf-next-batch)
-    (define-key map [M-prior] 'vlf-prev-batch)
+    (define-key map "n" 'vlf-next-batch)
+    (define-key map "p" 'vlf-prev-batch)
+    (define-key map " " 'vlf-next-batch-from-point)
     (define-key map "+" 'vlf-change-batch-size)
     (define-key map "-"
       (lambda () "Decrease vlf batch size by factor of 2."
@@ -74,37 +88,71 @@
     (define-key map "o" 'vlf-occur)
     (define-key map "[" 'vlf-beginning-of-file)
     (define-key map "]" 'vlf-end-of-file)
-    (define-key map "e" 'vlf-edit-mode)
     (define-key map "j" 'vlf-jump-to-chunk)
     (define-key map "l" 'vlf-goto-line)
+    (define-key map "g" 'vlf-revert)
     map)
   "Keymap for `vlf-mode'.")
 
-(define-derived-mode vlf-mode special-mode "VLF"
+(defvar vlf-prefix-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map "\C-c\C-v" vlf-mode-map)
+    map)
+  "Prefixed keymap for `vlf-mode'.")
+
+(defmacro vlf-with-undo-disabled (&rest body)
+  "Execute BODY with temporarily disabled undo."
+  `(let ((undo-enabled (not (eq buffer-undo-list t))))
+     (if undo-enabled
+         (buffer-disable-undo))
+     (unwind-protect (progn ,@body)
+       (if undo-enabled
+           (buffer-enable-undo)))))
+
+(define-minor-mode vlf-mode
   "Mode to browse large files in."
-  (setq buffer-read-only t)
-  (set-buffer-modified-p nil)
-  (buffer-disable-undo)
+  :lighter " VLF"
+  :group 'vlf
+  :keymap vlf-prefix-map
+  (if vlf-mode
+      (progn
+        (set (make-local-variable 'require-final-newline) nil)
         (add-hook 'write-file-functions 'vlf-write nil t)
-  (make-local-variable 'revert-buffer-function)
-  (setq revert-buffer-function 'vlf-revert)
+        (set (make-local-variable 'revert-buffer-function)
+             'vlf-revert)
         (make-local-variable 'vlf-batch-size)
-  (make-local-variable 'vlf-start-pos)
-  (make-local-variable 'vlf-end-pos)
-  (make-local-variable 'vlf-file-size))
+        (set (make-local-variable 'vlf-file-size)
+             (vlf-get-file-size buffer-file-truename))
+        (set (make-local-variable 'vlf-start-pos) 0)
+        (set (make-local-variable 'vlf-end-pos) 0)
+        (let* ((pos (position-bytes (point)))
+               (start (* (/ pos vlf-batch-size) vlf-batch-size)))
+          (goto-char (byte-to-position (- pos start)))
+          (vlf-move-to-batch start)))
+    (kill-local-variable 'revert-buffer-function)
+    (when (or (not large-file-warning-threshold)
+              (< vlf-file-size large-file-warning-threshold)
+              (y-or-n-p (format "Load whole file (%s)? "
+                                (file-size-human-readable
+                                 vlf-file-size))))
+      (kill-local-variable 'require-final-newline)
+      (remove-hook 'write-file-functions 'vlf-write t)
+      (let ((pos (+ vlf-start-pos (position-bytes (point)))))
+        (vlf-with-undo-disabled
+         (insert-file-contents buffer-file-name t nil nil t))
+        (goto-char (byte-to-position pos)))
+      (rename-buffer (file-name-nondirectory buffer-file-name) t))))
 
 ;;;###autoload
 (defun vlf (file)
-  "View Large FILE.
-Batches of the file data from FILE will be displayed in a read-only
-buffer.  You can customize number of bytes displayed by customizing
+  "View Large FILE in batches.
+You can customize number of bytes displayed by customizing
 `vlf-batch-size'."
   (interactive "fFile to open: ")
   (with-current-buffer (generate-new-buffer "*vlf*")
     (set-visited-file-name file)
-    (vlf-mode)
-    (setq vlf-file-size (vlf-get-file-size buffer-file-name))
-    (vlf-insert-file)
+    (set-buffer-modified-p nil)
+    (vlf-mode 1)
     (switch-to-buffer (current-buffer))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -120,16 +168,65 @@ buffer.  You can customize number of bytes displayed by customizing
 (eval-after-load "dired"
   '(define-key dired-mode-map "V" 'dired-vlf))
 
+;;;###autoload
+(defcustom vlf-forbidden-modes-list
+  '(archive-mode tar-mode jka-compr git-commit-mode image-mode
+                 doc-view-mode doc-view-mode-maybe)
+  "Major modes which VLF will not be automatically applied to."
+  :group 'vlf
+  :type '(list symbol))
+
+;;;###autoload
+(defun vlf-determine-major-mode (filename)
+  "Determine major mode from FILENAME."
+  (let ((name filename)
+        (remote-id (file-remote-p filename))
+        mode)
+    ;; Remove backup-suffixes from file name.
+    (setq name (file-name-sans-versions name))
+    ;; Remove remote file name identification.
+    (and (stringp remote-id)
+         (string-match (regexp-quote remote-id) name)
+         (setq name (substring name (match-end 0))))
+    (setq mode
+          (if (memq system-type '(windows-nt cygwin))
+              ;; System is case-insensitive.
+              (let ((case-fold-search t))
+                (assoc-default name auto-mode-alist 'string-match))
+            ;; System is case-sensitive.
+            (or ;; First match case-sensitively.
+             (let ((case-fold-search nil))
+               (assoc-default name auto-mode-alist 'string-match))
+             ;; Fallback to case-insensitive match.
+             (and auto-mode-case-fold
+                  (let ((case-fold-search t))
+                    (assoc-default name auto-mode-alist
+                                   'string-match))))))
+    (if (and mode (consp mode))
+        (cadr mode)
+      mode)))
+
 ;;;###autoload
 (defadvice abort-if-file-too-large (around vlf-if-file-too-large
-                                           (size op-type
-                                                 &optional filename)
                                            compile activate)
   "If file SIZE larger than `large-file-warning-threshold', \
 allow user to view file with `vlf', open it normally, or abort.
 OP-TYPE specifies the file operation being performed over FILENAME."
-  (and large-file-warning-threshold size
-       (> size large-file-warning-threshold)
+  (cond
+   ((or (not size) (zerop size)))
+   ((or (not vlf-application)
+        (not filename)
+        (memq (vlf-determine-major-mode filename)
+              vlf-forbidden-modes-list))
+    ad-do-it)
+   ((eq vlf-application 'always)
+    (vlf filename)
+    (error ""))
+   ((and large-file-warning-threshold
+         (< large-file-warning-threshold size))
+    (if (eq vlf-application 'dont-ask)
+        (progn (vlf filename)
+               (error ""))
       (let ((char nil))
         (while (not (memq (setq char
                                 (read-event
@@ -144,20 +241,17 @@ OP-TYPE specifies the file operation being performed over FILENAME."
                                    op-type op-type)
                                   'face 'minibuffer-prompt)))
                           '(?o ?O ?v ?V ?a ?A))))
-         (cond ((memq char '(?o ?O)))
-               ((memq char '(?v ?V))
+        (cond ((memq char '(?v ?V))
                (vlf filename)
                (error ""))
               ((memq char '(?a ?A))
-                (error "Aborted"))))))
-
+               (error "Aborted"))))))))
 
 ;; scroll auto batching
 (defadvice scroll-up (around vlf-scroll-up
                              activate compile)
   "Slide to next batch if at end of buffer in `vlf-mode'."
-  (if (and (derived-mode-p 'vlf-mode)
-           (eobp))
+  (if (and vlf-mode (pos-visible-in-window-p (point-max)))
       (progn (vlf-next-batch 1)
              (goto-char (point-min)))
     ad-do-it))
@@ -165,8 +259,7 @@ OP-TYPE specifies the file operation being performed over FILENAME."
 (defadvice scroll-down (around vlf-scroll-down
                                activate compile)
   "Slide to previous batch if at beginning of buffer in `vlf-mode'."
-  (if (and (derived-mode-p 'vlf-mode)
-           (bobp))
+  (if (and vlf-mode (pos-visible-in-window-p (point-min)))
       (progn (vlf-prev-batch 1)
              (goto-char (point-max)))
     ad-do-it))
@@ -176,7 +269,7 @@ OP-TYPE specifies the file operation being performed over FILENAME."
 (unless (fboundp 'file-size-human-readable)
   (defun file-size-human-readable (file-size)
     "Print FILE-SIZE in MB."
-    (format "%.1fMB" (/ file-size 1048576.0))))
+    (format "%.3fMB" (/ file-size 1048576.0))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; utilities
@@ -191,27 +284,23 @@ with the prefix argument DECREASE it is halved."
                          (* vlf-batch-size 2)))
   (vlf-move-to-batch vlf-start-pos))
 
-(defun vlf-format-buffer-name ()
-  "Return format for vlf buffer name."
-  (format "%s(%s)[%d/%d](%d)"
-          (file-name-nondirectory buffer-file-name)
-          (file-size-human-readable vlf-file-size)
-          (/ vlf-end-pos vlf-batch-size)
-          (/ vlf-file-size vlf-batch-size)
-          vlf-batch-size))
-
 (defun vlf-update-buffer-name ()
   "Update the current buffer name."
-  (rename-buffer (vlf-format-buffer-name) t))
+  (rename-buffer (format "%s(%d/%d)[%s]"
+                         (file-name-nondirectory buffer-file-name)
+                         (/ vlf-end-pos vlf-batch-size)
+                         (/ vlf-file-size vlf-batch-size)
+                         (file-size-human-readable vlf-batch-size))
+                 t))
 
 (defun vlf-get-file-size (file)
   "Get size in bytes of FILE."
-  (nth 7 (file-attributes file)))
+  (or (nth 7 (file-attributes file)) 0))
 
 (defun vlf-verify-size ()
   "Update file size information if necessary and visited file time."
   (unless (verify-visited-file-modtime (current-buffer))
-    (setq vlf-file-size (vlf-get-file-size buffer-file-name))
+    (setq vlf-file-size (vlf-get-file-size buffer-file-truename))
     (set-visited-file-modtime)))
 
 (defun vlf-insert-file (&optional from-end)
@@ -238,9 +327,12 @@ With FROM-END prefix, start from the back."
 (defun vlf-revert (&optional _ignore-auto noconfirm)
   "Revert current chunk.  Ignore _IGNORE-AUTO.
 Ask for confirmation if NOCONFIRM is nil."
-  (if (or noconfirm
+  (interactive)
+  (when (or noconfirm
             (yes-or-no-p (format "Revert buffer from file %s? "
                                  buffer-file-name)))
+    (set-buffer-modified-p nil)
+    (set-visited-file-modtime)
     (vlf-move-to-chunk-2 vlf-start-pos vlf-end-pos)))
 
 (defun vlf-jump-to-chunk (n)
@@ -248,6 +340,12 @@ Ask for confirmation if NOCONFIRM is nil."
   (interactive "nGoto to chunk: ")
   (vlf-move-to-batch (* (1- n) vlf-batch-size)))
 
+(defun vlf-no-modifications ()
+  "Ensure there are no buffer modifications."
+  (if (buffer-modified-p)
+      (error "Save or discard your changes first")
+    t))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; batch movement
 
@@ -259,8 +357,7 @@ When prefix argument is negative
  append next APPEND number of batches to the existing buffer."
   (interactive "p")
   (vlf-verify-size)
-  (let* ((end (min (+ vlf-end-pos (* vlf-batch-size
-                                      (abs append)))
+  (let* ((end (min (+ vlf-end-pos (* vlf-batch-size (abs append)))
                    vlf-file-size))
          (start (if (< append 0)
                     vlf-start-pos
@@ -276,8 +373,7 @@ When prefix argument is negative
   (interactive "p")
   (if (zerop vlf-start-pos)
       (error "Already at BOF"))
-  (let* ((start (max 0 (- vlf-start-pos (* vlf-batch-size
-                                            (abs prepend)))))
+  (let* ((start (max 0 (- vlf-start-pos (* vlf-batch-size (abs prepend)))))
          (end (if (< prepend 0)
                   vlf-end-pos
                 (+ start vlf-batch-size))))
@@ -294,6 +390,13 @@ When given MINIMAL flag, skip non important operations."
         (setq start (max 0 (- end vlf-batch-size))))
     (vlf-move-to-chunk start end minimal)))
 
+(defun vlf-next-batch-from-point ()
+  "Display batch of file data starting from current point."
+  (interactive)
+  (let ((start (+ vlf-start-pos (position-bytes (point)) -1)))
+    (vlf-move-to-chunk start (+ start vlf-batch-size)))
+  (goto-char (point-min)))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; primitive chunk operations
 
@@ -304,10 +407,7 @@ If same as current chunk is requested, do nothing."
   (unless (and (= start vlf-start-pos)
                (= end vlf-end-pos))
     (vlf-verify-size)
-    (if (buffer-modified-p)
     (if (vlf-move-to-chunk-1 start end)
-            (or minimal (vlf-update-buffer-name)))
-      (vlf-move-to-chunk-2 start end)
         (or minimal (vlf-update-buffer-name)))))
 
 (defun vlf-move-to-chunk-1 (start end)
@@ -324,35 +424,53 @@ Return t if move hasn't been canceled."
         t))
      ((or (<= edit-end start) (<= end vlf-start-pos))
       (when (or (not modified)
-                (y-or-n-p "Buffer modified, are you sure? ")) ; full chunk renewal
+                (y-or-n-p "Chunk modified, are you sure? ")) ;full chunk renewal
+        (set-buffer-modified-p nil)
         (vlf-move-to-chunk-2 start end)
         t))
      ((or (and (<= start vlf-start-pos) (<= edit-end end))
           (not modified)
-          (y-or-n-p "Buffer modified, are you sure? "))
+          (y-or-n-p "Chunk modified, are you sure? "))
       (let ((pos (+ (position-bytes (point)) vlf-start-pos))
             (shift-start 0)
             (shift-end 0)
             (inhibit-read-only t))
         (cond ((< end edit-end)
-               (delete-region (byte-to-position (1+
-                                                 (- end
-                                                    vlf-start-pos)))
-                              (point-max)))
+               (let* ((del-pos (1+ (byte-to-position
+                                    (- end vlf-start-pos))))
+                      (del-len (length (encode-coding-region
+                                        del-pos (point-max)
+                                        buffer-file-coding-system
+                                        t))))
+                 (setq end (- (if (zerop vlf-end-pos)
+                                  vlf-file-size
+                                vlf-end-pos)
+                              del-len))
+                 (vlf-with-undo-disabled
+                  (delete-region del-pos (point-max)))))
               ((< edit-end end)
                (let ((edit-end-pos (point-max)))
                  (goto-char edit-end-pos)
+                 (vlf-with-undo-disabled
                   (insert-file-contents buffer-file-name nil
                                         vlf-end-pos end)
                   (setq shift-end (cdr (vlf-adjust-chunk
                                         vlf-end-pos end nil t
-                                       edit-end-pos))))))
+                                        edit-end-pos)))))))
         (cond ((< vlf-start-pos start)
-               (delete-region (point-min) (byte-to-position
+               (let* ((del-pos (1+ (byte-to-position
                                     (- start vlf-start-pos))))
+                      (del-len (length (encode-coding-region
+                                        (point-min) del-pos
+                                        buffer-file-coding-system
+                                        t))))
+                 (setq start (+ vlf-start-pos del-len))
+                 (vlf-with-undo-disabled
+                  (delete-region (point-min) del-pos))))
               ((< start vlf-start-pos)
                (let ((edit-end-pos (point-max)))
                  (goto-char edit-end-pos)
+                 (vlf-with-undo-disabled
                   (insert-file-contents buffer-file-name nil
                                         start vlf-start-pos)
                   (setq shift-start (car
@@ -362,11 +480,13 @@ Return t if move hasn't been canceled."
                                                        edit-end-pos)))
                   (goto-char (point-min))
                   (insert (delete-and-extract-region edit-end-pos
-                                                    (point-max))))))
-        (setq vlf-start-pos (- start shift-start)
-              vlf-end-pos (+ end shift-end))
-        (goto-char (or (byte-to-position (- pos vlf-start-pos))
-                       (point-max))))
+                                                     (point-max)))))))
+        (setq start (- start shift-start))
+        (goto-char (or (byte-to-position (- pos start))
+                       (byte-to-position (- pos vlf-start-pos))
+                       (point-max)))
+        (setq vlf-start-pos start
+              vlf-end-pos (+ end shift-end)))
       (set-buffer-modified-p modified)
       t))))
 
@@ -376,6 +496,7 @@ Return t if move hasn't been canceled."
         vlf-end-pos (min end vlf-file-size))
   (let ((inhibit-read-only t)
         (pos (position-bytes (point))))
+    (vlf-with-undo-disabled
      (erase-buffer)
      (insert-file-contents buffer-file-name nil
                            vlf-start-pos vlf-end-pos)
@@ -384,24 +505,23 @@ Return t if move hasn't been canceled."
        (setq vlf-start-pos (- vlf-start-pos (car shifts))
              vlf-end-pos (+ vlf-end-pos (cdr shifts)))
        (goto-char (or (byte-to-position (+ pos (car shifts)))
-                     (point-max)))))
+                      (point-max))))))
   (set-buffer-modified-p nil)
   (set-visited-file-modtime))
 
 (defun vlf-adjust-chunk (start end &optional adjust-start adjust-end
                                position)
-  "Adjust chunk at absolute START to END till content can be \
+  "Adjust chunk at absolute START to END till content can be\
 properly decoded.  ADJUST-START determines if trying to prepend bytes\
- to the beginning, ADJUST-END - add to the end.
+ to the beginning, ADJUST-END - append to the end.
 Use buffer POSITION as start if given.
 Return number of bytes moved back for proper decoding and number of
 bytes added to the end."
-  (let ((position (or position (point-min)))
-        (shift-start 0)
-        (shift-end 0)
-        (chunk-size (- end start)))
-    ;; adjust beginning
+  (let ((shift-start 0)
+        (shift-end 0))
     (if adjust-start
+        (let ((position (or position (point-min)))
+              (chunk-size (- end start)))
           (while (and (not (zerop start))
                       (< shift-start 4)
                       (< 4 (abs (- chunk-size
@@ -414,25 +534,35 @@ bytes added to the end."
                   chunk-size (1+ chunk-size))
             (delete-region position (point-max))
             (goto-char position)
-          (insert-file-contents buffer-file-name nil start end)))
-    ;; adjust end
-    (when (and adjust-end (< end vlf-file-size))
-      (let ((expected-size (buffer-size)))
-        (while (and (= expected-size (buffer-size))
-                    (< end vlf-file-size))
+            (insert-file-contents buffer-file-name nil start end))))
+    (if adjust-end
+        (cond ((vlf-partial-decode-shown-p) ;remove raw bytes from end
+               (goto-char (point-max))
+               (while (eq (char-charset (preceding-char)) 'eight-bit)
+                 (setq shift-end (1- shift-end))
+                 (delete-char -1)))
+              ((< end vlf-file-size) ;add bytes until new character is displayed
+               (let ((position (or position (point-min)))
+                     (expected-size (buffer-size)))
+                 (while (and (progn
                                (setq shift-end (1+ shift-end)
                                      end (1+ end))
                                (delete-region position (point-max))
                                (goto-char position)
-          (insert-file-contents buffer-file-name nil start end)))
-      (when (< end vlf-file-size)
-        (setq shift-end (1- shift-end)
-              end (1- end))
-        (delete-region position (point-max))
-        (goto-char position)
-        (insert-file-contents buffer-file-name nil start end)))
+                               (insert-file-contents buffer-file-name
+                                                     nil start end)
+                               (< end vlf-file-size))
+                             (= expected-size (buffer-size))))))))
     (cons shift-start shift-end)))
 
+(defun vlf-partial-decode-shown-p ()
+  "Determine if partial decode codes are displayed.
+This seems to be the case with GNU/Emacs before 24.4."
+  (cond ((< emacs-major-version 24) t)
+        ((< 24 emacs-major-version) nil)
+        (t ;; TODO: use (< emacs-minor-version 4) after 24.4 release
+         (string-lessp emacs-version "24.3.5"))))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; search
 
@@ -441,7 +571,8 @@ bytes added to the end."
 BATCH-STEP is amount of overlap between successive chunks."
   (if (<= count 0)
       (error "Count must be positive"))
-  (let* ((match-chunk-start vlf-start-pos)
+  (let* ((case-fold-search t)
+         (match-chunk-start vlf-start-pos)
          (match-chunk-end vlf-end-pos)
          (match-start-pos (+ vlf-start-pos (position-bytes (point))))
          (match-end-pos match-start-pos)
@@ -452,8 +583,7 @@ BATCH-STEP is amount of overlap between successive chunks."
                         (- vlf-file-size vlf-end-pos)
                       vlf-start-pos)
                     vlf-file-size)))
-    (set-buffer-modified-p nil)
-    (buffer-disable-undo)
+    (vlf-with-undo-disabled
      (unwind-protect
          (catch 'end-of-file
            (if backward
@@ -521,7 +651,7 @@ BATCH-STEP is amount of overlap between successive chunks."
                            count to-find)
          (vlf-goto-match match-chunk-start match-chunk-end
                          match-start-pos match-end-pos
-                         count to-find)))))
+                         count to-find))))))
 
 (defun vlf-goto-match (match-chunk-start match-chunk-end
                                          match-pos-start
@@ -554,31 +684,34 @@ successful.  Return nil if nothing found."
           (goto-char match-end)
           (message "Moved to the %d match which is last"
                    (- count to-find)))
-        (unwind-protect (sit-for 5)
+        (unwind-protect (sit-for 3)
           (delete-overlay overlay))
         t))))
 
 (defun vlf-re-search-forward (regexp count)
   "Search forward for REGEXP prefix COUNT number of times.
 Search is performed chunk by chunk in `vlf-batch-size' memory."
-  (interactive (list (read-regexp "Search whole file"
+  (interactive (if (vlf-no-modifications)
+                   (list (read-regexp "Search whole file"
                                       (if regexp-history
                                           (car regexp-history)))
-                     (or current-prefix-arg 1)))
+                         (or current-prefix-arg 1))))
   (vlf-re-search regexp count nil (/ vlf-batch-size 8)))
 
 (defun vlf-re-search-backward (regexp count)
   "Search backward for REGEXP prefix COUNT number of times.
 Search is performed chunk by chunk in `vlf-batch-size' memory."
-  (interactive (list (read-regexp "Search whole file backward"
+  (interactive (if (vlf-no-modifications)
+                   (list (read-regexp "Search whole file backward"
                                       (if regexp-history
                                           (car regexp-history)))
-                     (or current-prefix-arg 1)))
+                         (or current-prefix-arg 1))))
   (vlf-re-search regexp count t (/ vlf-batch-size 8)))
 
 (defun vlf-goto-line (n)
   "Go to line N.  If N is negative, count from the end of file."
-  (interactive "nGo to line: ")
+  (interactive (if (vlf-no-modifications)
+                   (list (read-number "Go to line: "))))
   (let ((start-pos vlf-start-pos)
         (end-pos vlf-end-pos)
         (pos (point))
@@ -605,6 +738,7 @@ Search is performed chunk by chunk in `vlf-batch-size' memory."
     (define-key map "n" 'vlf-occur-next-match)
     (define-key map "p" 'vlf-occur-prev-match)
     (define-key map "\C-m" 'vlf-occur-visit)
+    (define-key map "\M-\r" 'vlf-occur-visit-new-buffer)
     (define-key map [mouse-1] 'vlf-occur-visit)
     (define-key map "o" 'vlf-occur-show)
     map)
@@ -644,10 +778,16 @@ EVENT may hold details of the invocation."
     (vlf-occur-visit event)
     (pop-to-buffer occur-buffer)))
 
+(defun vlf-occur-visit-new-buffer ()
+  "Visit `vlf-occur' link in new vlf buffer."
+  (interactive)
+  (let ((current-prefix-arg t))
+    (vlf-occur-visit)))
+
 (defun vlf-occur-visit (&optional event)
   "Visit current `vlf-occur' link in a vlf buffer.
-If original VLF buffer has been killed,
-open new VLF session each time.
+With prefix argument or if original VLF buffer has been killed,
+open new VLF session.
 EVENT may hold details of the invocation."
   (interactive (list last-nonmenu-event))
   (when event
@@ -659,14 +799,23 @@ EVENT may hold details of the invocation."
     (if file
         (let ((chunk-start (get-char-property pos 'chunk-start))
               (chunk-end (get-char-property pos 'chunk-end))
-              (buffer (get-char-property pos 'buffer))
+              (vlf-buffer (get-char-property pos 'buffer))
+              (occur-buffer (current-buffer))
               (match-pos (+ (get-char-property pos 'line-pos)
                             pos-relative)))
-          (or (buffer-live-p buffer)
-              (let ((occur-buffer (current-buffer)))
-                (setq buffer (vlf file))
+          (cond (current-prefix-arg
+                 (setq vlf-buffer (vlf file))
+                 (switch-to-buffer occur-buffer))
+                ((not (buffer-live-p vlf-buffer))
+                 (or (catch 'found
+                       (dolist (buf (buffer-list))
+                         (set-buffer buf)
+                         (and vlf-mode (equal file buffer-file-name)
+                              (setq vlf-buffer buf)
+                              (throw 'found t))))
+                     (setq vlf-buffer (vlf file)))
                  (switch-to-buffer occur-buffer)))
-          (pop-to-buffer buffer)
+          (pop-to-buffer vlf-buffer)
           (vlf-move-to-chunk chunk-start chunk-end)
           (goto-char match-pos)))))
 
@@ -676,21 +825,32 @@ Prematurely ending indexing will still show what's found so far."
   (interactive (list (read-regexp "List lines matching regexp"
                                   (if regexp-history
                                       (car regexp-history)))))
+  (if (buffer-modified-p) ;use temporary buffer not to interfere with modifications
+      (let ((vlf-buffer (current-buffer))
+            (file buffer-file-name)
+            (batch-size vlf-batch-size))
+        (with-temp-buffer
+          (setq buffer-file-name file)
+          (set-buffer-modified-p nil)
+          (set (make-local-variable 'vlf-batch-size) batch-size)
+          (vlf-mode 1)
+          (goto-char (point-min))
+          (vlf-with-undo-disabled
+           (vlf-build-occur regexp vlf-buffer))))
     (let ((start-pos vlf-start-pos)
           (end-pos vlf-end-pos)
           (pos (point)))
       (vlf-beginning-of-file)
       (goto-char (point-min))
-    (set-buffer-modified-p nil)
-    (buffer-disable-undo)
-    (unwind-protect (vlf-build-occur regexp)
-      (set-buffer-modified-p nil)
+      (vlf-with-undo-disabled
+       (unwind-protect (vlf-build-occur regexp (current-buffer))
          (vlf-move-to-chunk start-pos end-pos)
-      (goto-char pos))))
+         (goto-char pos))))))
 
-(defun vlf-build-occur (regexp)
-  "Build occur style index for REGEXP."
-  (let ((line 1)
+(defun vlf-build-occur (regexp vlf-buffer)
+  "Build occur style index for REGEXP over VLF-BUFFER."
+  (let ((case-fold-search t)
+        (line 1)
         (last-match-line 0)
         (last-line-pos (point-min))
         (file buffer-file-name)
@@ -720,7 +880,6 @@ Prematurely ending indexing will still show what's found so far."
                             last-line-pos (point))
                     (let* ((chunk-start vlf-start-pos)
                            (chunk-end vlf-end-pos)
-                           (vlf-buffer (current-buffer))
                            (line-pos (line-beginning-position))
                            (line-text (buffer-substring
                                        line-pos (line-end-position))))
@@ -773,6 +932,7 @@ Prematurely ending indexing will still show what's found so far."
                       last-line-pos (line-beginning-position))
                 (progress-reporter-update reporter vlf-end-pos))))
           (progress-reporter-done reporter))
+      (set-buffer-modified-p nil)
       (if (zerop total-matches)
           (progn (with-current-buffer occur-buffer
                    (set-buffer-modified-p nil))
@@ -781,7 +941,7 @@ Prematurely ending indexing will still show what's found so far."
         (with-current-buffer occur-buffer
           (goto-char (point-min))
           (insert (propertize
-                   (format "%d matches from %d lines for \"%s\" \
+                   (format "%d matches in %d lines for \"%s\" \
 in file: %s" total-matches line regexp file)
                    'face 'underline))
           (set-buffer-modified-p nil)
@@ -789,34 +949,6 @@ in file: %s" total-matches line regexp file)
           (vlf-occur-mode))
         (display-buffer occur-buffer)))))
 
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;; editing
-
-(defvar vlf-edit-mode-map
-  (let ((map (make-sparse-keymap)))
-    (set-keymap-parent map text-mode-map)
-    (define-key map "\C-c\C-c" 'vlf-write)
-    (define-key map "\C-c\C-q" 'vlf-discard-edit)
-    (define-key map "\C-v" vlf-mode-map)
-    map)
-  "Keymap for command `vlf-edit-mode'.")
-
-(define-derived-mode vlf-edit-mode vlf-mode "VLF[edit]"
-  "Major mode for editing large file chunks."
-  (setq buffer-read-only nil)
-  (buffer-enable-undo)
-  (message (substitute-command-keys
-            "Editing: Type \\[vlf-write] to write chunk \
-or \\[vlf-discard-edit] to discard changes.")))
-
-(defun vlf-discard-edit ()
-  "Discard edit and refresh chunk from file."
-  (interactive)
-  (set-buffer-modified-p nil)
-  (vlf-move-to-chunk vlf-start-pos vlf-end-pos)
-  (vlf-mode)
-  (message "Switched to VLF mode."))
-
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; saving
 
@@ -824,34 +956,47 @@ or \\[vlf-discard-edit] to discard changes.")))
   "Write current chunk to file.  Always return true to disable save.
 If changing size of chunk, shift remaining file content."
   (interactive)
-  (when (and (buffer-modified-p)
+  (and (buffer-modified-p)
        (or (verify-visited-file-modtime (current-buffer))
            (y-or-n-p "File has changed since visited or saved.  \
-Save anyway? ")))
-    (let ((pos (point))
-          (size-change (- vlf-end-pos vlf-start-pos
-                          (length (encode-coding-region
+Save anyway? "))
+       (if (zerop vlf-file-size)           ;new file
+           (progn
+             (write-region nil nil buffer-file-name vlf-start-pos t)
+             (setq vlf-file-size (vlf-get-file-size
+                                  buffer-file-truename)
+                   vlf-end-pos vlf-file-size)
+             (vlf-update-buffer-name))
+         (let* ((region-length (length (encode-coding-region
                                         (point-min) (point-max)
-                                   buffer-file-coding-system t)))))
-      (cond ((zerop size-change)
-             (write-region nil nil buffer-file-name vlf-start-pos t))
-            ((< 0 size-change)
-             (vlf-file-shift-back size-change))
-            (t (vlf-file-shift-forward (- size-change))))
-      (vlf-move-to-chunk-2 vlf-start-pos vlf-end-pos)
-      (goto-char pos))
-    (vlf-mode))
+                                        buffer-file-coding-system t)))
+                (size-change (- vlf-end-pos vlf-start-pos
+                                region-length)))
+           (if (zerop size-change)
+               (write-region nil nil buffer-file-name vlf-start-pos t)
+             (let ((pos (point)))
+               (if (< 0 size-change)
+                   (vlf-file-shift-back size-change)
+                 (vlf-file-shift-forward (- size-change))
+                 (vlf-verify-size))
+               (vlf-move-to-chunk-2 vlf-start-pos
+                                    (if (< (- vlf-end-pos vlf-start-pos)
+                                           vlf-batch-size)
+                                        (+ vlf-start-pos vlf-batch-size)
+                                      vlf-end-pos))
+               (vlf-update-buffer-name)
+               (goto-char pos))))))
   t)
 
 (defun vlf-file-shift-back (size-change)
   "Shift file contents SIZE-CHANGE bytes back."
   (write-region nil nil buffer-file-name vlf-start-pos t)
-  (buffer-disable-undo)
   (let ((read-start-pos vlf-end-pos)
         (coding-system-for-write 'no-conversion)
         (reporter (make-progress-reporter "Adjusting file content..."
                                           vlf-end-pos
                                           vlf-file-size)))
+    (vlf-with-undo-disabled
      (while (vlf-shift-batch read-start-pos (- read-start-pos
                                                size-change))
        (setq read-start-pos (+ read-start-pos vlf-batch-size))
@@ -859,7 +1004,7 @@ Save anyway? ")))
      ;; pad end with space
      (erase-buffer)
      (vlf-verify-size)
-    (insert-char 32 size-change)
+     (insert-char 32 size-change))
     (write-region nil nil buffer-file-name (- vlf-file-size
                                               size-change) t)
     (progress-reporter-done reporter)))
@@ -879,26 +1024,26 @@ back at WRITE-POS.  Return nil if EOF is reached, t otherwise."
 (defun vlf-file-shift-forward (size-change)
   "Shift file contents SIZE-CHANGE bytes forward.
 Done by saving content up front and then writing previous batch."
-  (buffer-disable-undo)
-  (let ((size (+ vlf-batch-size size-change))
+  (let ((read-size (max (/ vlf-batch-size 2) size-change))
         (read-pos vlf-end-pos)
         (write-pos vlf-start-pos)
         (reporter (make-progress-reporter "Adjusting file content..."
                                           vlf-start-pos
                                           vlf-file-size)))
-    (when (vlf-shift-batches size read-pos write-pos t)
+    (vlf-with-undo-disabled
+     (when (vlf-shift-batches read-size read-pos write-pos t)
        (setq write-pos (+ read-pos size-change)
-            read-pos (+ read-pos size))
+             read-pos (+ read-pos read-size))
        (progress-reporter-update reporter write-pos)
        (let ((coding-system-for-write 'no-conversion))
-        (while (vlf-shift-batches size read-pos write-pos nil)
+         (while (vlf-shift-batches read-size read-pos write-pos nil)
            (setq write-pos (+ read-pos size-change)
-                read-pos (+ read-pos size))
-          (progress-reporter-update reporter write-pos))))
+                 read-pos (+ read-pos read-size))
+           (progress-reporter-update reporter write-pos)))))
     (progress-reporter-done reporter)))
 
-(defun vlf-shift-batches (size read-pos write-pos hide-read)
-  "Append SIZE bytes of file starting at READ-POS.
+(defun vlf-shift-batches (read-size read-pos write-pos hide-read)
+  "Append READ-SIZE bytes of file starting at READ-POS.
 Then write initial buffer content to file at WRITE-POS.
 If HIDE-READ is non nil, temporarily hide literal read content.
 Return nil if EOF is reached, t otherwise."
@@ -909,8 +1054,8 @@ Return nil if EOF is reached, t otherwise."
     (when read-more
       (goto-char end-write-pos)
       (insert-file-contents-literally buffer-file-name nil read-pos
-                                      (min vlf-file-size (+ read-pos
-                                                             size))))
+                                      (min vlf-file-size
+                                           (+ read-pos read-size))))
     ;; write
     (if hide-read ; hide literal region if user has to choose encoding
         (narrow-to-region start-write-pos end-write-pos))

vlfi.el

@@ -1,41 +0,0 @@
-;;; vlfi.el --- Obsolete - install vlf instead!
-
-;; Copyright (C) 2006, 2012, 2013  Free Software Foundation, Inc.
-
-;; Version: 0.9.1.1
-;; Keywords: large files, utilities
-;; Maintainer: Andrey Kotlarski <m00naticus@gmail.com>
-;; Authors: 2006 Mathias Dahl <mathias.dahl@gmail.com>
-;;          2012 Sam Steingold <sds@gnu.org>
-;;          2013 Andrey Kotlarski <m00naticus@gmail.com>
-;; URL: https://github.com/m00natic/vlfi
-
-;; This file 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.
-
-;; This file 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:
-
-;; This package used to provide the M-x vlfi command, which visited
-;; part of a large file without loading the entire file.
-;; However, it has been merged back to the vlf package,
-;; so use that instead.
-
-;;; Code:
-
-;;;###autoload
-(error
- "vlfi package has been merged with vlf: please install that instead")
-
-;;; vlfi.el ends here