Re: Fix the destroyed disk image partition table in a raw image file using Emacs.

[Gregor Zattler <telegraph@gmx.net>]

Hi Hongyi Zhao,
* Hongyi Zhao <hongyi.zhao@gmail.com> [2021-04-11; 21:34]:
> $ dd if=disk.img bs=1 count=4 skip=440 2>/dev/null | od -t x4 -An
> 761b36b0
>
> It's well known that Emacs is an 8-bit clean editor which makes it
> safe to edit binary files. So, I want to whether I can fix the above
> destroyed disk image file with Emacs for my scenario.

If your emacs is able to handle the disk image in memory
(which probably means you need a 64bit emacs and enough RAM
installed) you could open the file of the disk image with

find-file-literally

   Visit file FILENAME with no conversion of any kind.

   Format conversion and character code conversion are both
   disabled, and multibyte characters are disabled in the
   resulting buffer.  The major mode used is Fundamental
   mode regardless of the file name, and local variable
   specifications in the file are ignored.  Automatic
   uncompression and adding a newline at the end of the file
   due to require-final-newline is also disabled.

And then the first thing to do would be

binary-overwrite-mode

   When Binary Overwrite mode is enabled, printing
   characters typed in replace existing text.  Newlines are
   not treated specially, so typing at the end of a line
   joins the line to the next, with the typed character
   between them.  Typing before a tab character simply
   replaces the tab with the character typed.  C-q replaces
   the text at the cursor, just as ordinary typing
   characters do.


You then can move point in the disk image to the desired
place and type in whatever you want and later save the
buffer to its file.


Ciao; Gregor
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