[ELPA-diffs] /srv/bzr/emacs/elpa r233: View Large Files from Mathias Dahl

[Sam Steingold]

------------------------------------------------------------
revno: 233
committer: Sam Steingold <address@hidden>
branch nick: elpa
timestamp: Thu 2012-06-14 16:32:31 -0400
message:
  View Large Files from Mathias Dahl
added:
  packages/vlf/
  packages/vlf/vlf.el

=== added directory 'packages/vlf'
=== added file 'packages/vlf/vlf.el'
--- a/packages/vlf/vlf.el       1970-01-01 00:00:00 +0000
+++ b/packages/vlf/vlf.el       2012-06-14 20:32:31 +0000
@@ -0,0 +1,218 @@
+;;; vlf.el --- View Large Files
+
+;; Copyright (C) 2006  Mathias Dahl
+
+;; Version: 0.1.2
+;; Keywords: files, helpers, utilities
+;; Author: Mathias Dahl <address@hidden>
+;; Maintainer: Mathias Dahl
+;; URL: http://www.emacswiki.org/cgi-bin/wiki/VLF
+
+;; 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:
+;;
+;; After reading the Nth post on Gnu Emacs Help about Viewing Large
+;; Files in Emacs, it itched so much that I decided to make a try.  It
+;; helped quite a lot when Kevin Rodgers posted a snippet on how to
+;; use `insert-file-contents' to extract part of a file.  At first I
+;; made a try using head and tail and that worked too, but using
+;; internal Emacs commands is nicer.  Here is the code to extract data
+;; using head and tail in case someone wanna try that out in the
+;; future:
+
+;; (defun vlf-extract-part-of-file (file from to)
+;;   "Returns bytes in FILE from FROM to TO."
+;;   (let ((size (vlf-file-size file)))
+;;     (if (or (> from size)
+;;             (> to size))
+;;         (error "From or to is larger that the file size"))
+;;     (with-temp-buffer
+;;       (shell-command
+;;        (format "head --bytes %d %s | tail --bytes %d"
+;;            to file (+ (- to from) 1)) t)
+;;       (buffer-substring (point-min) (point-max)))))
+
+;;; History:
+;;
+;; - Wed Jan 10 00:13:45 2007
+;;
+;;    First version created and released into the wild.
+;;
+;; - Wed Jan 10 18:58:47 2007
+;;
+;;    0.1.2
+;;
+;;    Added option to use external tools (head and tail) for
+;;    extracting the data from the file.
+;;
+;;    Refactored buffer name format code into a new function.
+;;
+;;    Started to fiddle with float/integer conversions.
+;;
+
+;;; Bugs
+;;
+;; Probably some. Feel free to fix them :)
+
+;;; Code:
+
+(defgroup vlf nil
+  "Browse large files in Emacs"
+  :prefix "vlf-"
+  :group 'files)
+
+(defcustom vlf-batch-size 1000
+  "Defines how large each batch of file data is."
+  :type 'integer
+  :group 'vlf)
+
+(defcustom vlf-external-extraction nil
+  "How to extract the data from a file.
+`nil' means to use internal extraction, using
+`insert-file-contents'. `t' means to use external `head' and
+`tail' tools."
+  :type 'boolean
+  :group 'vlf)
+
+(defvar vlf-current-start-pos 1
+  "Keeps track of file position.")
+
+(defvar vlf-current-batch-size nil
+  "Keeps track of current batch size.")
+
+(defvar vlf-current-file nil
+  "File that is currently viewed.")
+
+(defvar vlf-current-file-size 0
+  "Size of current file.")
+
+(defvar vlf-mode-map (make-sparse-keymap)
+  "Keymap for `vlf-mode'.")
+
+(defun vlf-define-keymap ()
+  "Define keymap for `vlf-mode'."
+  (define-key vlf-mode-map [next] 'vlf-next)
+  (define-key vlf-mode-map [prior] 'vlf-prev)
+  (define-key vlf-mode-map "q" 'vlf-quit))
+
+(define-derived-mode vlf-mode
+  fundamental-mode "vlf-mode"
+  "Mode to browse large files in.
+See `vlf' for details."
+  (vlf-define-keymap)
+  (toggle-read-only 1)
+  (message "vlf-mode enabled"))
+
+(defun vlf-file-size (file)
+  "Get size of FILE."
+  (nth 7 (file-attributes file)))
+
+(defun vlf-quit ()
+  "Quit vlf."
+  (interactive)
+  (kill-buffer (current-buffer)))
+
+(defun vlf-extract-with-head-and-tail (file from to)
+  "Returns bytes in FILE from FROM to TO."
+  (let ((size (vlf-file-size file)))
+    (if (or (> from size)
+            (> to size))
+        (error "From or to is larger that the file size"))
+    (with-temp-buffer
+      (shell-command
+       (format "head --bytes %.0f \"%s\" | tail --bytes %.0f"
+              (float to) (expand-file-name file)
+               (float (+ (- to from) 1))) t)
+      (buffer-substring (point-min) (point-max)))))
+
+(defun vlf-insert-batch ()
+  "Insert current batch of data."
+  (let* ((beg (1- vlf-current-start-pos))
+        (end (+ beg vlf-current-batch-size)))
+    (if vlf-external-extraction
+        (insert
+         (vlf-extract-with-head-and-tail
+          vlf-current-file (1+ beg) end))
+      (insert-file-contents
+       vlf-current-file nil
+       (floor beg) (floor end)))))
+
+(defun vlf-format-buffer-name ()
+  "Return format for vlf buffer name."
+  (format "%s[%.0f,%.0f(%.0f)]"
+          (file-name-nondirectory vlf-current-file)
+          vlf-current-start-pos
+          (1- (+ vlf-current-start-pos
+                 vlf-current-batch-size))
+          vlf-current-file-size))
+
+(defun vlf-next ()
+  "Display the next batch of file data."
+  (interactive)
+  (let ((inhibit-read-only t)
+        left next-start-pos
+        (size (vlf-file-size vlf-current-file)))
+    (setq next-start-pos (float (+ vlf-current-start-pos
+                                   vlf-batch-size)))
+    (if (> next-start-pos size)
+        (message "End of file")
+      (setq vlf-current-batch-size
+            vlf-batch-size
+            vlf-current-start-pos next-start-pos
+            left (1+ (- size vlf-current-start-pos)))
+      (if (< left vlf-current-batch-size)
+          (setq vlf-current-batch-size left))
+      (erase-buffer)
+      (vlf-insert-batch)
+      (rename-buffer
+       (vlf-format-buffer-name)))))
+
+(defun vlf-prev ()
+  "Display the previous batch of file data."
+  (interactive)
+  (if (= 1 vlf-current-start-pos)
+      (message "At beginning of file")
+    (let ((inhibit-read-only t))
+      (erase-buffer)
+      (setq vlf-current-start-pos (- vlf-current-start-pos
+                                     vlf-batch-size)
+            vlf-current-batch-size vlf-batch-size)
+      (vlf-insert-batch)
+      (rename-buffer
+       (vlf-format-buffer-name)))))
+
+(defun vlf (file)
+  "View a large file in Emacs 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 amount of bytes to
+display by customizing `vlf-batch-size'."
+  (interactive "fFile to open: ")
+  (setq vlf-current-file file
+        vlf-current-start-pos 1
+        vlf-current-file-size (vlf-file-size file)
+        vlf-current-batch-size
+        (1- (+ vlf-current-start-pos
+               vlf-batch-size)))
+  (switch-to-buffer
+   (generate-new-buffer (vlf-format-buffer-name)))
+  (erase-buffer)
+  (vlf-insert-batch)
+  (vlf-mode))
+
+(provide 'vlf)
+
+;;; vlf.el ends here