------------------------------------------------------------ revno: 233 committer: Sam Steingold <s...@gnu.org> 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 <mathias.d...@gmail.com> +;; 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
