X-Git-Url: https://code.delx.au/gnu-emacs-elpa/blobdiff_plain/0cdc945e2cdc9e1f7a72ed03639cff7edecc12ea..f0c48b253ea7903357d73eba6cc6ba3051ff8962:/packages/vlf/vlf.el

diff --git a/packages/vlf/vlf.el b/packages/vlf/vlf.el
index 28b65f186..e6c34e641 100644
--- a/packages/vlf/vlf.el
+++ b/packages/vlf/vlf.el
@@ -2,7 +2,7 @@
 
 ;; Copyright (C) 2006, 2012, 2013  Free Software Foundation, Inc.
 
-;; Version: 0.9.1
+;; Version: 1.1
 ;; Keywords: large files, utilities
 ;; Maintainer: Andrey Kotlarski <m00naticus@gmail.com>
 ;; Authors: 2006 Mathias Dahl <mathias.dahl@gmail.com>
@@ -60,13 +60,12 @@
 (defvar vlf-file-size 0 "Total size of presented file.")
 (put 'vlf-file-size 'permanent-local t)
 
-(defvar vlf-encode-size 0 "Size in bytes of current batch decoded.")
-(put 'vlf-encode-size 'permanent-local t)
-
 (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)
+  (let ((map-prefix (make-sparse-keymap))
+        (map (make-sparse-keymap)))
+    (define-key map [next] 'vlf-next-batch)
+    (define-key map [prior] 'vlf-prev-batch)
+    (define-key map "n" 'vlf-next-batch-from-point)
     (define-key map "+" 'vlf-change-batch-size)
     (define-key map "-"
       (lambda () "Decrease vlf batch size by factor of 2."
@@ -77,38 +76,57 @@
     (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)
-    map)
+    (define-key map "g" 'vlf-refresh)
+    (define-key map-prefix "\C-c\C-v" map)
+    map-prefix)
   "Keymap for `vlf-mode'.")
 
-(define-derived-mode vlf-mode special-mode "VLF"
+(define-minor-mode vlf-mode
   "Mode to browse large files in."
-  (setq buffer-read-only t)
-  (set-buffer-modified-p nil)
-  (buffer-disable-undo)
-  (add-hook 'write-file-functions 'vlf-write nil t)
-  (make-local-variable 'revert-buffer-function)
-  (setq 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)
-  (make-local-variable 'vlf-encode-size))
+  :lighter " VLF"
+  :group 'vlf
+  :keymap vlf-mode-map
+  (if vlf-mode
+      (progn
+        (set (make-local-variable 'require-final-newline) nil)
+        (add-hook 'write-file-functions 'vlf-write nil t)
+        (set (make-local-variable 'revert-buffer-function)
+             'vlf-revert)
+        (make-local-variable 'vlf-batch-size)
+        (set (make-local-variable 'vlf-start-pos) -1)
+        (make-local-variable 'vlf-end-pos)
+        (set (make-local-variable 'vlf-file-size)
+             (vlf-get-file-size buffer-file-name))
+        (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))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -160,17 +178,15 @@ OP-TYPE specifies the file operation being performed over FILENAME."
 (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))
 
 (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))
+  "Slide to previous batch if at beginning of buffer in `vlf-mode'."
+  (if (and vlf-mode (pos-visible-in-window-p (point-min)))
       (progn (vlf-prev-batch 1)
              (goto-char (point-max)))
     ad-do-it))
@@ -191,22 +207,18 @@ Normally, the value is doubled;
 with the prefix argument DECREASE it is halved."
   (interactive "P")
   (setq vlf-batch-size (if decrease
-                            (/ vlf-batch-size 2)
-                          (* vlf-batch-size 2)))
+                           (/ vlf-batch-size 2)
+                         (* 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."
@@ -221,12 +233,13 @@ with the prefix argument DECREASE it is halved."
 (defun vlf-insert-file (&optional from-end)
   "Insert first chunk of current file contents in current buffer.
 With FROM-END prefix, start from the back."
-  (if from-end
-      (setq vlf-start-pos (max 0 (- vlf-file-size vlf-batch-size))
-            vlf-end-pos vlf-file-size)
-    (setq vlf-start-pos 0
-          vlf-end-pos (min vlf-batch-size vlf-file-size)))
-  (vlf-move-to-chunk vlf-start-pos vlf-end-pos))
+  (let ((start 0)
+        (end vlf-batch-size))
+    (if from-end
+        (setq start (- vlf-file-size vlf-batch-size)
+              end vlf-file-size)
+      (setq end (min vlf-batch-size vlf-file-size)))
+    (vlf-move-to-chunk start end)))
 
 (defun vlf-beginning-of-file ()
   "Jump to beginning of file content."
@@ -244,13 +257,28 @@ Ask for confirmation if NOCONFIRM is nil."
   (if (or noconfirm
           (yes-or-no-p (format "Revert buffer from file %s? "
                                buffer-file-name)))
-      (vlf-move-to-chunk vlf-start-pos vlf-end-pos)))
+      (vlf-move-to-chunk-2 vlf-start-pos vlf-end-pos)))
 
 (defun vlf-jump-to-chunk (n)
   "Go to to chunk N."
   (interactive "nGoto to chunk: ")
   (vlf-move-to-batch (* (1- n) vlf-batch-size)))
 
+(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)))))
+
+(defun vlf-no-modifications ()
+  "Ensure there are no buffer modifications."
+  (if (buffer-modified-p)
+      (error "Save or discard your changes first")
+    t))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; batch movement
 
@@ -262,26 +290,13 @@ 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
+  (let* ((end (min (+ vlf-end-pos (* vlf-batch-size
                                      (abs append)))
-                  vlf-file-size)))
-    (let ((inhibit-read-only t)
-          (do-append (< append 0))
-          (pos (position-bytes (point))))
-      (if do-append
-          (goto-char (point-max))
-        (setq vlf-start-pos (- end vlf-batch-size))
-        (erase-buffer))
-      (insert-file-contents buffer-file-name nil (if do-append
-                                                     vlf-end-pos
-                                                   vlf-start-pos)
-                            end)
-      (setq vlf-end-pos end)
-      (goto-char (or (byte-to-position (+ pos (vlf-adjust-chunk)))
-                     (point-max)))))
-  (set-visited-file-modtime)
-  (set-buffer-modified-p nil)
-  (vlf-update-buffer-name))
+                   vlf-file-size))
+         (start (if (< append 0)
+                    vlf-start-pos
+                  (- end vlf-batch-size))))
+    (vlf-move-to-chunk start end)))
 
 (defun vlf-prev-batch (prepend)
   "Display the previous batch of file data.
@@ -292,92 +307,190 @@ When prefix argument is negative
   (interactive "p")
   (if (zerop vlf-start-pos)
       (error "Already at BOF"))
-  (vlf-verify-size)
-  (let ((inhibit-read-only t)
-        (start (max 0 (- vlf-start-pos (* vlf-batch-size
+  (let* ((start (max 0 (- vlf-start-pos (* vlf-batch-size
                                            (abs prepend)))))
-        (do-prepend (< prepend 0))
-        (pos (- (position-bytes (point-max))
-                (position-bytes (point)))))
-    (if do-prepend
-        (goto-char (point-min))
-      (setq vlf-end-pos (min (+ start vlf-batch-size)
-                              vlf-file-size))
-      (erase-buffer))
-    (insert-file-contents buffer-file-name nil start
-                          (if do-prepend
-                              vlf-start-pos
-                            vlf-end-pos))
-    (setq vlf-start-pos start
-          pos (+ pos (vlf-adjust-chunk)))
-    (goto-char (or (byte-to-position (- (position-bytes (point-max))
-                                        pos))
-                   (point-max))))
-  (set-visited-file-modtime)
-  (set-buffer-modified-p nil)
-  (vlf-update-buffer-name))
+         (end (if (< prepend 0)
+                  vlf-end-pos
+                (+ start vlf-batch-size))))
+    (vlf-move-to-chunk start end)))
 
 (defun vlf-move-to-batch (start &optional minimal)
   "Move to batch determined by START.
 Adjust according to file start/end and show `vlf-batch-size' bytes.
 When given MINIMAL flag, skip non important operations."
   (vlf-verify-size)
-  (setq vlf-start-pos (max 0 start)
-        vlf-end-pos (min (+ vlf-start-pos vlf-batch-size)
-                          vlf-file-size))
-  (if (= vlf-file-size vlf-end-pos)   ; re-check file size
-      (setq vlf-start-pos (max 0 (- vlf-end-pos vlf-batch-size))))
-  (let ((inhibit-read-only t)
-        (pos (position-bytes (point))))
-    (erase-buffer)
-    (insert-file-contents buffer-file-name nil
-                          vlf-start-pos vlf-end-pos)
-    (goto-char (or (byte-to-position (+ pos (vlf-adjust-chunk)))
-                   (point-max))))
-  (set-buffer-modified-p nil)
-  (set-visited-file-modtime)
-  (or minimal(vlf-update-buffer-name)))
+  (let* ((start (max 0 start))
+         (end (min (+ start vlf-batch-size) vlf-file-size)))
+    (if (= vlf-file-size end)          ; re-adjust start
+        (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)
+  (vlf-move-to-batch (+ vlf-start-pos (position-bytes (point)) -1))
+  (goto-char (point-min)))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;; primitive chunk operations
 
 (defun vlf-move-to-chunk (start end &optional minimal)
   "Move to chunk determined by START END.
-When given MINIMAL flag, skip non important operations."
-  (vlf-verify-size)
+When given MINIMAL flag, skip non important operations.
+If same as current chunk is requested, do nothing."
+  (unless (and (= start vlf-start-pos)
+               (= end vlf-end-pos))
+    (vlf-verify-size)
+    (if (vlf-move-to-chunk-1 start end)
+        (or minimal (vlf-update-buffer-name)))))
+
+(defun vlf-move-to-chunk-1 (start end)
+  "Move to chunk determined by START END keeping as much edits if any.
+Return t if move hasn't been canceled."
+  (let ((modified (buffer-modified-p))
+        (start (max 0 start))
+        (end (min end vlf-file-size))
+        (edit-end (+ (position-bytes (point-max)) vlf-start-pos)))
+    (cond
+     ((and (= start vlf-start-pos) (= end edit-end))
+      (unless modified
+        (vlf-move-to-chunk-2 start end)
+        t))
+     ((or (<= edit-end start) (<= end vlf-start-pos))
+      (when (or (not modified)
+                (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 "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)
+               (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 (- 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)))))))
+        (cond ((< vlf-start-pos start)
+               (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
+                                     (vlf-adjust-chunk start
+                                                       vlf-start-pos
+                                                       t nil
+                                                       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))))
+      (set-buffer-modified-p modified)
+      t))))
+
+(defun vlf-move-to-chunk-2 (start end)
+  "Unconditionally move to chunk determined by START END."
   (setq vlf-start-pos (max 0 start)
         vlf-end-pos (min end vlf-file-size))
   (let ((inhibit-read-only t)
         (pos (position-bytes (point))))
-    (erase-buffer)
-    (insert-file-contents buffer-file-name nil
-                          vlf-start-pos vlf-end-pos)
-    (goto-char (or (byte-to-position (+ pos (vlf-adjust-chunk)))
-                   (point-max))))
+    (vlf-with-undo-disabled
+     (erase-buffer)
+     (insert-file-contents buffer-file-name nil
+                           vlf-start-pos vlf-end-pos)
+     (let ((shifts (vlf-adjust-chunk vlf-start-pos vlf-end-pos t
+                                     t)))
+       (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))))))
   (set-buffer-modified-p nil)
-  (set-visited-file-modtime)
-  (or minimal (vlf-update-buffer-name)))
-
-(defun vlf-adjust-chunk ()
-  "Adjust chunk beginning until content can be properly decoded.
-Set `vlf-encode-size' to size of buffer when encoded.
-Return number of bytes moved back for this to happen."
-  (let ((shift 0)
-        (chunk-size (- vlf-end-pos vlf-start-pos)))
-    (while (and (< shift 4)
-                (< 4 (abs (- chunk-size
-                             (setq vlf-encode-size
+  (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\
+properly decoded.  ADJUST-START determines if trying to prepend bytes\
+ 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 ((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
                                    (length (encode-coding-region
-                                            (point-min) (point-max)
+                                            position (point-max)
                                             buffer-file-coding-system
                                             t))))))
-                (not (zerop vlf-start-pos)))
-      (setq shift (1+ shift)
-            vlf-start-pos (1- vlf-start-pos)
-            chunk-size (1+ chunk-size))
-      (let ((inhibit-read-only t))
-        (erase-buffer)
-        (insert-file-contents buffer-file-name nil
-                              vlf-start-pos vlf-end-pos)))
-    (set-buffer-modified-p nil)
-    shift))
+            (setq shift-start (1+ shift-start)
+                  start (1- start)
+                  chunk-size (1+ chunk-size))
+            (delete-region position (point-max))
+            (goto-char position)
+            (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)
+                               (< 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
@@ -385,8 +498,10 @@ Return number of bytes moved back for this to happen."
 (defun vlf-re-search (regexp count backward batch-step)
   "Search for REGEXP COUNT number of times forward or BACKWARD.
 BATCH-STEP is amount of overlap between successive chunks."
-  (assert (< 0 count))
-  (let* ((match-chunk-start vlf-start-pos)
+  (if (<= count 0)
+      (error "Count must be positive"))
+  (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)
@@ -397,78 +512,80 @@ BATCH-STEP is amount of overlap between successive chunks."
                         (- vlf-file-size vlf-end-pos)
                       vlf-start-pos)
                     vlf-file-size)))
-    (unwind-protect
-        (catch 'end-of-file
-          (if backward
-              (while (not (zerop to-find))
-                (cond ((re-search-backward regexp nil t)
-                       (setq to-find (1- to-find)
-                             match-chunk-start vlf-start-pos
-                             match-chunk-end vlf-end-pos
-                             match-start-pos (+ vlf-start-pos
-                                                (position-bytes
-                                                 (match-beginning 0)))
-                             match-end-pos (+ vlf-start-pos
-                                              (position-bytes
-                                               (match-end 0)))))
-                      ((zerop vlf-start-pos)
-                       (throw 'end-of-file nil))
-                      (t (let ((batch-move (- vlf-start-pos
-                                              (- vlf-batch-size
-                                                 batch-step))))
-                           (vlf-move-to-batch
-                            (if (< match-start-pos batch-move)
-                                (- match-start-pos vlf-batch-size)
-                              batch-move) t))
-                         (goto-char (if (< match-start-pos
-                                           vlf-end-pos)
-                                        (or (byte-to-position
-                                             (- match-start-pos
-                                                vlf-start-pos))
-                                            (point-max))
-                                      (point-max)))
-                         (progress-reporter-update
-                          reporter (- vlf-file-size
-                                      vlf-start-pos)))))
-            (while (not (zerop to-find))
-              (cond ((re-search-forward regexp nil t)
-                     (setq to-find (1- to-find)
-                           match-chunk-start vlf-start-pos
-                           match-chunk-end vlf-end-pos
-                           match-start-pos (+ vlf-start-pos
-                                              (position-bytes
-                                               (match-beginning 0)))
-                           match-end-pos (+ vlf-start-pos
-                                            (position-bytes
-                                             (match-end 0)))))
-                    ((= vlf-end-pos vlf-file-size)
-                     (throw 'end-of-file nil))
-                    (t (let ((batch-move (- vlf-end-pos batch-step)))
-                         (vlf-move-to-batch
-                          (if (< batch-move match-end-pos)
-                              match-end-pos
-                            batch-move) t))
-                       (goto-char (if (< vlf-start-pos match-end-pos)
-                                      (or (byte-to-position
-                                           (- match-end-pos
-                                              vlf-start-pos))
-                                          (point-min))
-                                    (point-min)))
-                       (progress-reporter-update reporter
-                                                 vlf-end-pos)))))
-          (progress-reporter-done reporter))
-      (if backward
-          (vlf-goto-match match-chunk-start match-chunk-end
+    (vlf-with-undo-disabled
+     (unwind-protect
+         (catch 'end-of-file
+           (if backward
+               (while (not (zerop to-find))
+                 (cond ((re-search-backward regexp nil t)
+                        (setq to-find (1- to-find)
+                              match-chunk-start vlf-start-pos
+                              match-chunk-end vlf-end-pos
+                              match-start-pos (+ vlf-start-pos
+                                                 (position-bytes
+                                                  (match-beginning 0)))
+                              match-end-pos (+ vlf-start-pos
+                                               (position-bytes
+                                                (match-end 0)))))
+                       ((zerop vlf-start-pos)
+                        (throw 'end-of-file nil))
+                       (t (let ((batch-move (- vlf-start-pos
+                                               (- vlf-batch-size
+                                                  batch-step))))
+                            (vlf-move-to-batch
+                             (if (< match-start-pos batch-move)
+                                 (- match-start-pos vlf-batch-size)
+                               batch-move) t))
+                          (goto-char (if (< match-start-pos
+                                            vlf-end-pos)
+                                         (or (byte-to-position
+                                              (- match-start-pos
+                                                 vlf-start-pos))
+                                             (point-max))
+                                       (point-max)))
+                          (progress-reporter-update
+                           reporter (- vlf-file-size
+                                       vlf-start-pos)))))
+             (while (not (zerop to-find))
+               (cond ((re-search-forward regexp nil t)
+                      (setq to-find (1- to-find)
+                            match-chunk-start vlf-start-pos
+                            match-chunk-end vlf-end-pos
+                            match-start-pos (+ vlf-start-pos
+                                               (position-bytes
+                                                (match-beginning 0)))
+                            match-end-pos (+ vlf-start-pos
+                                             (position-bytes
+                                              (match-end 0)))))
+                     ((= vlf-end-pos vlf-file-size)
+                      (throw 'end-of-file nil))
+                     (t (let ((batch-move (- vlf-end-pos batch-step)))
+                          (vlf-move-to-batch
+                           (if (< batch-move match-end-pos)
+                               match-end-pos
+                             batch-move) t))
+                        (goto-char (if (< vlf-start-pos match-end-pos)
+                                       (or (byte-to-position
+                                            (- match-end-pos
+                                               vlf-start-pos))
+                                           (point-min))
+                                     (point-min)))
+                        (progress-reporter-update reporter
+                                                  vlf-end-pos)))))
+           (progress-reporter-done reporter))
+       (set-buffer-modified-p nil)
+       (if backward
+           (vlf-goto-match match-chunk-start match-chunk-end
                            match-end-pos match-start-pos
                            count to-find)
-        (vlf-goto-match match-chunk-start match-chunk-end
+         (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
-                                          match-pos-end
-                                          count to-find)
+                                         match-pos-start
+                                         match-pos-end
+                                         count to-find)
   "Move to MATCH-CHUNK-START MATCH-CHUNK-END surrounding \
 MATCH-POS-START and MATCH-POS-END.
 According to COUNT and left TO-FIND, show if search has been
@@ -496,31 +613,34 @@ successful.  Return nil if nothing found."
           (goto-char match-end)
           (message "Moved to the %d match which is last"
                    (- count to-find)))
-        (sit-for 0.1)
-        (delete-overlay overlay)
+        (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"
-                                  (if regexp-history
-                                      (car regexp-history)))
-                     (or current-prefix-arg 1)))
+  (interactive (if (vlf-no-modifications)
+                   (list (read-regexp "Search whole file"
+                                      (if regexp-history
+                                          (car regexp-history)))
+                         (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"
-                                  (if regexp-history
-                                      (car regexp-history)))
-                     (or current-prefix-arg 1)))
+  (interactive (if (vlf-no-modifications)
+                   (list (read-regexp "Search whole file backward"
+                                      (if regexp-history
+                                          (car regexp-history)))
+                         (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))
@@ -530,7 +650,7 @@ Search is performed chunk by chunk in `vlf-batch-size' memory."
             (progn (vlf-beginning-of-file)
                    (goto-char (point-min))
                    (setq success (vlf-re-search "[\n\C-m]" (1- n)
-                                                 nil 0)))
+                                                nil 0)))
           (vlf-end-of-file)
           (goto-char (point-max))
           (setq success (vlf-re-search "[\n\C-m]" (- n) t 0)))
@@ -547,6 +667,7 @@ 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)
@@ -586,10 +707,16 @@ 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
@@ -601,24 +728,25 @@ 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))
-                (switch-to-buffer occur-buffer)))
-          (pop-to-buffer buffer)
-          (if (buffer-modified-p)
-              (cond ((and (= vlf-start-pos chunk-start)
-                          (= vlf-end-pos chunk-end))
-                     (goto-char match-pos))
-                    ((y-or-n-p "VLF buffer has been modified.  \
-Really jump to new chunk? ")
-                     (vlf-move-to-chunk chunk-start chunk-end)
-                     (goto-char match-pos)))
-            (vlf-move-to-chunk chunk-start chunk-end)
-            (goto-char match-pos))))))
+          (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 vlf-buffer)
+          (vlf-move-to-chunk chunk-start chunk-end)
+          (goto-char match-pos)))))
 
 (defun vlf-occur (regexp)
   "Make whole file occur style index for REGEXP.
@@ -626,18 +754,32 @@ 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)))))
-  (let ((start-pos vlf-start-pos)
-        (end-pos vlf-end-pos)
-        (pos (point)))
-    (vlf-beginning-of-file)
-    (goto-char (point-min))
-    (unwind-protect (vlf-build-occur regexp)
-      (vlf-move-to-chunk start-pos end-pos)
-      (goto-char pos))))
-
-(defun vlf-build-occur (regexp)
-  "Build occur style index for REGEXP."
-  (let ((line 1)
+  (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))
+      (vlf-with-undo-disabled
+       (unwind-protect (vlf-build-occur regexp (current-buffer))
+         (vlf-move-to-chunk start-pos end-pos)
+         (goto-char pos))))))
+
+(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)
@@ -645,7 +787,7 @@ Prematurely ending indexing will still show what's found so far."
         (match-end-pos (+ vlf-start-pos (position-bytes (point))))
         (occur-buffer (generate-new-buffer
                        (concat "*VLF-occur " (file-name-nondirectory
-                                               buffer-file-name)
+                                              buffer-file-name)
                                "*")))
         (line-regexp (concat "\\(?5:[\n\C-m]\\)\\|\\(?10:"
                              regexp "\\)"))
@@ -667,7 +809,6 @@ 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))))
@@ -709,8 +850,8 @@ Prematurely ending indexing will still show what's found so far."
               (unless end-of-file
                 (let ((batch-move (- vlf-end-pos batch-step)))
                   (vlf-move-to-batch (if (< batch-move match-end-pos)
-                                          match-end-pos
-                                        batch-move) t))
+                                         match-end-pos
+                                       batch-move) t))
                 (goto-char (if (< vlf-start-pos match-end-pos)
                                (or (byte-to-position (- match-end-pos
                                                         vlf-start-pos))
@@ -720,6 +861,7 @@ 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))
@@ -728,7 +870,7 @@ 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)
@@ -739,30 +881,11 @@ in file: %s" total-matches line regexp file)
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; 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 ()
+(defun vlf-refresh ()
   "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."))
+  (vlf-move-to-chunk-2 vlf-start-pos vlf-end-pos))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; saving
@@ -776,39 +899,36 @@ If changing size of chunk, shift remaining file content."
                  (y-or-n-p "File has changed since visited or saved.  \
 Save anyway? ")))
     (let ((pos (point))
-          (size-change (- vlf-encode-size
-                          (setq vlf-encode-size
-                                (length (encode-coding-region
-                                         (point-min) (point-max)
-                                         buffer-file-coding-system
-                                         t))))))
+          (size-change (- vlf-end-pos vlf-start-pos
+                          (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 vlf-start-pos vlf-end-pos)
-      (goto-char pos))
-    (vlf-mode))
+      (vlf-move-to-chunk-2 vlf-start-pos vlf-end-pos)
+      (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)))
-    (while (vlf-shift-batch read-start-pos (- read-start-pos
+    (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))
-      (progress-reporter-update reporter read-start-pos))
-    ;; pad end with space
-    (erase-buffer)
-    (vlf-verify-size)
-    (insert-char 32 size-change)
+       (setq read-start-pos (+ read-start-pos vlf-batch-size))
+       (progress-reporter-update reporter read-start-pos))
+     ;; pad end with space
+     (erase-buffer)
+     (vlf-verify-size)
+     (insert-char 32 size-change))
     (write-region nil nil buffer-file-name (- vlf-file-size
                                               size-change) t)
     (progress-reporter-done reporter)))
@@ -828,26 +948,26 @@ 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)
-      (setq write-pos (+ read-pos size-change)
-            read-pos (+ read-pos size))
-      (progress-reporter-update reporter write-pos)
-      (let ((coding-system-for-write 'no-conversion))
-        (while (vlf-shift-batches size read-pos write-pos nil)
-          (setq write-pos (+ read-pos size-change)
-                read-pos (+ read-pos size))
-          (progress-reporter-update reporter write-pos))))
+    (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 read-size))
+       (progress-reporter-update reporter write-pos)
+       (let ((coding-system-for-write 'no-conversion))
+         (while (vlf-shift-batches read-size read-pos write-pos nil)
+           (setq write-pos (+ read-pos size-change)
+                 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."
@@ -858,8 +978,8 @@ 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))