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Re: feature request: view part of file
From: |
Andrey Kotlarski |
Subject: |
Re: feature request: view part of file |
Date: |
Sat, 04 Aug 2012 14:58:22 +0300 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) |
Sam Steingold <address@hidden> writes:
> I put vlf.el by Mathias into elpa.
Hello,
thanks for putting this in gnu elpa, it's quite useful.
> I rewrote it almost completely (bzr still has the original version at
> revno 233).
>
> it works for me.
> I wish I knew how to hook it into files.el, but I don't...
>
> vlf.el has 2 issues:
>
> 1. insert-file-contents hangs emacs (see `vlf-next-batch'):
>
> ;; replacing `erase-buffer' with replace arg to `insert-file-contents'
> ;; hangs emacs
> (unless append (erase-buffer))
> (insert-file-contents buffer-file-name nil vlf-end-pos end)
I guess you've been using rather large file. My attempts showed that
non nil REPLACE argument of insert-file-contents doesn't honour BEG END
and always inserts the whole file.
Anyway, I've made a few additions that I think are worth sharing.
* Option to start viewing from the end of file
* Ability to jump/insert given number of batches at once
* Ability to view newly added content if the file has grown meanwhile
Here is a changelog entry if necessary and a diff:
2012-08-04 Andrey Kotlarski <address@hidden>
* vlf.el (vlf-mode-map): Add decrease batch key binding.
(vlf-change-batch-size): Fix doc string.
(vlf-format-buffer-name): Fix indentation.
(vlf-next-batch): Optionally jump/insert several batches based on
prefix argument. If requested batch is past the end of file, get
current file length and view as much as possible.
(vlf-prev-batch): Optionally jump/insert several batches based on
prefix argument.
(vlf): Start viewing from end of file if prefix argument is
given. Add autoload cookie.
diff -u vlf.el\~ vlf.el
--- vlf.el~ 2012-07-23 17:34:54.000000000 +0300
+++ vlf.el 2012-07-27 23:44:43.696003339 +0300
@@ -2,7 +2,7 @@
;; Copyright (C) 2006, 2012 Free Software Foundation, Inc.
-;; Version: 0.2
+;; Version: 0.3
;; Keywords: large files, utilities
;; Authors: 2006 Mathias Dahl <address@hidden>
;; 2012 Sam Steingold <address@hidden>
@@ -57,6 +57,10 @@
(define-key map [M-next] 'vlf-next-batch)
(define-key map [M-prior] 'vlf-prev-batch)
(define-key map (kbd "C-+") 'vlf-change-batch-size)
+ (define-key map (kbd "C--")
+ (lambda () "Decrease vlf batch size by factor of 2."
+ (interactive)
+ (vlf-change-batch-size t)))
map)
"Keymap for `vlf-mode'.")
@@ -71,22 +75,22 @@
(defun vlf-change-batch-size (decrease)
"Change the buffer-local value of `vlf-batch-size'.
Normally, the value is doubled;
-with the prefix argument it is halved."
+with the prefix argument DECREASE it is halved."
(interactive "P")
(or (assq 'vlf-batch-size (buffer-local-variables))
(error "%s is not local in this buffer" 'vlf-batch-size))
(setq vlf-batch-size
- (if decrease
- (/ vlf-batch-size 2)
- (* vlf-batch-size 2)))
+ (if decrease
+ (/ vlf-batch-size 2)
+ (* vlf-batch-size 2)))
(vlf-update-buffer-name))
(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-start-pos vlf-end-pos vlf-batch-size))
+ (file-name-nondirectory buffer-file-name)
+ (file-size-human-readable vlf-file-size)
+ vlf-start-pos vlf-end-pos vlf-batch-size))
(defun vlf-update-buffer-name ()
"Update the current buffer name."
@@ -94,56 +98,80 @@
(defun vlf-next-batch (append)
"Display the next batch of file data.
-Append to the existing buffer when the prefix argument is supplied."
- (interactive "P")
- (when (= vlf-end-pos vlf-file-size)
- (error "Already at EOF"))
- (let ((inhibit-read-only t)
- (end (min vlf-file-size (+ vlf-end-pos vlf-batch-size))))
- (goto-char (point-max))
- ;; replacing `erase-buffer' with replace arg to `insert-file-contents'
- ;; hangs emacs
- (unless append (erase-buffer))
- (insert-file-contents buffer-file-name nil vlf-end-pos end)
- (unless append
- (setq vlf-start-pos vlf-end-pos))
- (setq vlf-end-pos end)
- (set-buffer-modified-p nil)
- (vlf-update-buffer-name)))
+When prefix argument is supplied and positive
+ jump over APPEND number of batches.
+When prefix argument is negative
+ append next APPEND number of batches to the existing buffer."
+ (interactive "p")
+ (let ((end (+ vlf-end-pos (* vlf-batch-size
+ (abs append)))))
+ (when (< vlf-file-size end) ; re-check file size
+ (setq vlf-file-size (nth 7 (file-attributes buffer-file-name)))
+ (cond ((= vlf-end-pos vlf-file-size)
+ (error "Already at EOF"))
+ ((< vlf-file-size end)
+ (setq end vlf-file-size))))
+ (let ((inhibit-read-only t)
+ (do-append (< append 0)))
+ (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))
+ (set-buffer-modified-p nil)
+ (vlf-update-buffer-name))
(defun vlf-prev-batch (prepend)
"Display the previous batch of file data.
-Prepend to the existing buffer when the prefix argument is supplied."
- (interactive "P")
- (when (= vlf-start-pos 0)
- (error "Already at BOF"))
+When prefix argument is supplied and positive
+ jump over PREPEND number of batches.
+When prefix argument is negative
+ append previous PREPEND number of batches to the existing buffer."
+ (interactive "p")
+ (if (zerop vlf-start-pos)
+ (error "Already at BOF"))
(let ((inhibit-read-only t)
- (start (max 0 (- vlf-start-pos vlf-batch-size))))
- (goto-char (point-min))
- (unless prepend (erase-buffer))
- (insert-file-contents buffer-file-name nil start vlf-start-pos)
- (unless prepend
- (setq vlf-end-pos vlf-start-pos))
- (setq vlf-start-pos start)
- (set-buffer-modified-p nil)
- (vlf-update-buffer-name)))
+ (start (max 0 (- vlf-start-pos (* vlf-batch-size
+ (abs prepend)))))
+ (do-prepend (< prepend 0)))
+ (if do-prepend
+ (goto-char (point-min))
+ (setq vlf-end-pos (+ start vlf-batch-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))
+ (set-buffer-modified-p nil)
+ (vlf-update-buffer-name))
-(defun vlf (file)
+;;;###autoload
+(defun vlf (from-end file)
"View a Large File in Emacs.
+With FROM-END prefix, view from the back.
FILE is the file to open.
Batches of the file data from FILE will be displayed in a
read-only buffer.
You can customize the number of bytes to
display by customizing `vlf-batch-size'."
- (interactive "fFile to open: ")
+ (interactive "P\nfFile to open: ")
(with-current-buffer (generate-new-buffer "*vlf*")
(setq buffer-file-name file
- vlf-start-pos 0
- vlf-end-pos vlf-batch-size
- vlf-file-size (nth 7 (file-attributes file)))
+ vlf-file-size (nth 7 (file-attributes file)))
+ (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-update-buffer-name)
(insert-file-contents buffer-file-name nil
- vlf-start-pos vlf-end-pos nil)
+ vlf-start-pos vlf-end-pos)
(vlf-mode)
(display-buffer (current-buffer))))
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