--- /dev/null
+;;; vlf-write.el --- Saving functionality for VLF -*- lexical-binding: t -*-
+
+;; Copyright (C) 2014 Free Software Foundation, Inc.
+
+;; Keywords: large files, saving
+;; Author: Andrey Kotlarski <m00naticus@gmail.com>
+;; URL: https://github.com/m00natic/vlfi
+
+;; 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 3, 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:
+;; This package provides the `vlf-write' command which takes care of
+;; saving changes where only part of file is viewed and updated.
+
+;;; Code:
+
+(defun vlf-write ()
+ "Write current chunk to file. Always return true to disable save.
+If changing size of chunk, shift remaining file content."
+ (interactive)
+ (and (buffer-modified-p)
+ (or (verify-visited-file-modtime (current-buffer))
+ (y-or-n-p "File has changed since visited or saved. \
+Save anyway? "))
+ (if (zerop vlf-file-size) ;new file
+ (progn
+ (write-region nil nil buffer-file-name vlf-start-pos t)
+ (setq vlf-file-size (vlf-get-file-size
+ buffer-file-truename)
+ vlf-end-pos vlf-file-size)
+ (vlf-update-buffer-name))
+ (let* ((region-length (length (encode-coding-region
+ (point-min) (point-max)
+ buffer-file-coding-system t)))
+ (size-change (- vlf-end-pos vlf-start-pos
+ region-length)))
+ (if (zerop size-change)
+ (write-region nil nil buffer-file-name vlf-start-pos t)
+ (let ((pos (point)))
+ (if (< 0 size-change)
+ (vlf-file-shift-back size-change)
+ (vlf-file-shift-forward (- size-change))
+ (vlf-verify-size))
+ (vlf-move-to-chunk-2 vlf-start-pos
+ (if (< (- vlf-end-pos vlf-start-pos)
+ vlf-batch-size)
+ (+ vlf-start-pos vlf-batch-size)
+ vlf-end-pos))
+ (vlf-update-buffer-name)
+ (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)
+ (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)))
+ (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))
+ (write-region nil nil buffer-file-name (- vlf-file-size
+ size-change) t)
+ (progress-reporter-done reporter)))
+
+(defun vlf-shift-batch (read-pos write-pos)
+ "Read `vlf-batch-size' bytes from READ-POS and write them \
+back at WRITE-POS. Return nil if EOF is reached, t otherwise."
+ (erase-buffer)
+ (vlf-verify-size)
+ (let ((read-end (+ read-pos vlf-batch-size)))
+ (insert-file-contents-literally buffer-file-name nil
+ read-pos
+ (min vlf-file-size read-end))
+ (write-region nil nil buffer-file-name write-pos 0)
+ (< read-end vlf-file-size)))
+
+(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."
+ (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)))
+ (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 (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."
+ (vlf-verify-size)
+ (let ((read-more (< read-pos vlf-file-size))
+ (start-write-pos (point-min))
+ (end-write-pos (point-max)))
+ (when read-more
+ (goto-char end-write-pos)
+ (insert-file-contents-literally buffer-file-name nil read-pos
+ (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))
+ (write-region start-write-pos end-write-pos
+ buffer-file-name write-pos 0)
+ (delete-region start-write-pos end-write-pos)
+ (if hide-read (widen))
+ read-more))
+
+(provide 'vlf-write)
+
+;;; vlf-write.el ends here