Turn vlf into minor mode.

vlf.el

@@ -61,9 +61,10 @@
 (put 'vlf-file-size 'permanent-local t)
 
 (defvar vlf-mode-map
-  (let ((map (make-sparse-keymap)))
+  (let ((map (make-sparse-keymap))
-    (define-key map [M-next] 'vlf-next-batch)
+        (map-prefix (make-sparse-keymap)))
-    (define-key map [M-prior] 'vlf-prev-batch)
+    (define-key map [next] 'vlf-next-batch)
+    (define-key map [prior] 'vlf-prev-batch)
     (define-key map "+" 'vlf-change-batch-size)
     (define-key map "-"
       (lambda () "Decrease vlf batch size by factor of 2."
@@ -74,37 +75,56 @@
     (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 "q" 'vlf-discard-edit)
+    (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)
+  :lighter " VLF"
-  (set-buffer-modified-p nil)
+  :group 'vlf-mode
-  (buffer-disable-undo)
+  :keymap vlf-mode-map
+  (if vlf-mode
+      (progn
         (add-hook 'write-file-functions 'vlf-write nil t)
-  (make-local-variable 'revert-buffer-function)
+        (set (make-local-variable 'revert-buffer-function)
-  (setq revert-buffer-function 'vlf-revert)
+             'vlf-revert)
         (make-local-variable 'vlf-batch-size)
-  (make-local-variable 'vlf-start-pos)
+        (set (make-local-variable 'vlf-start-pos) -1)
         (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-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)))
+    (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))))
+      (remove-hook 'write-file-functions 'vlf-write t)
+      (kill-local-variable 'revert-buffer-function)
+      (let ((pos (+ vlf-start-pos (position-bytes (point)))))
+        (erase-buffer)
+        (insert-file-contents buffer-file-name)
+        (set-buffer-modified-p nil)
+        (goto-char (byte-to-position pos)))
+      (rename-buffer (file-name-nondirectory buffer-file-name) t))))
 
 ;;;###autoload
 (defun vlf (file)
-  "View Large FILE.
+  "View Large FILE in batches.
-Batches of the file data from FILE will be displayed in a read-only
+You can customize number of bytes displayed by customizing
-buffer.  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)
+    (set-buffer-modified-p nil)
-    (setq vlf-file-size (vlf-get-file-size buffer-file-name))
+    (vlf-mode 1)
-    (vlf-insert-file)
     (switch-to-buffer (current-buffer))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -156,8 +176,7 @@ 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)
+  (if (and vlf-mode (eobp))
-           (eobp))
       (progn (vlf-next-batch 1)
              (goto-char (point-min)))
     ad-do-it))
@@ -165,8 +184,7 @@ 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)
+  (if (and vlf-mode (bobp))
-           (bobp))
       (progn (vlf-prev-batch 1)
              (goto-char (point-max)))
     ad-do-it))
@@ -193,16 +211,20 @@ with the prefix argument DECREASE it is halved."
 
 (defun vlf-format-buffer-name ()
   "Return format for vlf buffer name."
-  (format "%s(%s)[%d/%d](%d)"
+  (format "%s[%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-file-size vlf-batch-size)))
-          vlf-batch-size))
 
 (defun vlf-update-buffer-name ()
-  "Update the current buffer name."
+  "Update the current buffer name and modeline."
-  (rename-buffer (vlf-format-buffer-name) t))
+  (rename-buffer (vlf-format-buffer-name) t)
+  (setq minor-mode-alist
+        (mapcar (lambda (x)
+                  (if (eq 'vlf-mode (car x))
+                      `(vlf-mode ,(format " VLF[%d]" vlf-batch-size))
+                    x))
+                minor-mode-alist)))
 
 (defun vlf-get-file-size (file)
   "Get size in bytes of FILE."
@@ -248,6 +270,13 @@ Ask for confirmation if NOCONFIRM is nil."
   (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."
+  (declare (indent defun))
+  `(progn (buffer-disable-undo)
+          (unwind-protect (progn ,@body)
+            (buffer-enable-undo))))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; batch movement
 
@@ -313,6 +342,7 @@ If same as current chunk is requested, do nothing."
 (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."
+  (vlf-with-undo-disabled
    (let ((modified (buffer-modified-p))
          (start (max 0 start))
          (end (min end vlf-file-size))
@@ -324,7 +354,7 @@ 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 "Buffer modified, are you sure? ")) ;full chunk renewal
          (vlf-move-to-chunk-2 start end)
          t))
       ((or (and (<= start vlf-start-pos) (<= edit-end end))
@@ -368,10 +398,11 @@ Return t if move hasn't been canceled."
          (goto-char (or (byte-to-position (- pos vlf-start-pos))
                         (point-max))))
        (set-buffer-modified-p modified)
-      t))))
+       t)))))
 
 (defun vlf-move-to-chunk-2 (start end)
   "Unconditionally move to chunk determined by START END."
+  (vlf-with-undo-disabled
     (setq vlf-start-pos (max 0 start)
           vlf-end-pos (min end vlf-file-size))
     (let ((inhibit-read-only t)
@@ -386,7 +417,7 @@ Return t if move hasn't been canceled."
         (goto-char (or (byte-to-position (+ pos (car shifts)))
                        (point-max)))))
     (set-buffer-modified-p nil)
-  (set-visited-file-modtime))
+    (set-visited-file-modtime)))
 
 (defun vlf-adjust-chunk (start end &optional adjust-start adjust-end
                                position)
@@ -453,7 +484,7 @@ BATCH-STEP is amount of overlap between successive chunks."
                       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 +552,7 @@ 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
@@ -682,11 +713,11 @@ Prematurely ending indexing will still show what's found so far."
     (vlf-beginning-of-file)
     (goto-char (point-min))
     (set-buffer-modified-p nil)
-    (buffer-disable-undo)
+    (vlf-with-undo-disabled
      (unwind-protect (vlf-build-occur regexp)
        (set-buffer-modified-p nil)
        (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."
@@ -792,30 +823,11 @@ 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 ()
   "Discard edit and refresh chunk from file."
   (interactive)
   (set-buffer-modified-p nil)
-  (vlf-move-to-chunk vlf-start-pos vlf-end-pos)
+  (vlf-move-to-chunk vlf-start-pos vlf-end-pos))
-  (vlf-mode)
-  (message "Switched to VLF mode."))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; saving
@@ -839,14 +851,13 @@ Save anyway? ")))
              (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))
+      (goto-char pos)))
-    (vlf-mode))
   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)
+  (vlf-with-undo-disabled
    (let ((read-start-pos vlf-end-pos)
          (coding-system-for-write 'no-conversion)
          (reporter (make-progress-reporter "Adjusting file content..."
@@ -862,7 +873,7 @@ Save anyway? ")))
      (insert-char 32 size-change)
      (write-region nil nil buffer-file-name (- vlf-file-size
                                                size-change) t)
-    (progress-reporter-done reporter)))
+     (progress-reporter-done reporter))))
 
 (defun vlf-shift-batch (read-pos write-pos)
   "Read `vlf-batch-size' bytes from READ-POS and write them \
@@ -879,26 +890,26 @@ 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)
+  (vlf-with-undo-disabled
-  (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)
+     (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))
+                 read-pos (+ read-pos read-size))
            (progress-reporter-update reporter write-pos))))
-    (progress-reporter-done reporter)))
+     (progress-reporter-done reporter))))
 
-(defun vlf-shift-batches (size read-pos write-pos hide-read)
+(defun vlf-shift-batches (read-size read-pos write-pos hide-read)
-  "Append SIZE bytes of file starting at READ-POS.
+  "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 +920,8 @@ 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
+                                      (min vlf-file-size
-                                                             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))