hexl-mode: searching for multi byte sequence?

hexl-mode: searching for multi byte sequence?

[Alfred M. Szmidt]

Is there some way in hexl-mode to  search for a (hex, octal, ...) byte
sequence?  Currently, C-s behaves a  bit strange in at least two regards:

1) If  file contains  the byte sequence  #xDEADBEAF, depending  on how
   they are  aligned (odd  or even  word), one has  to look  for "DEAD
   BEAF" and "DE ADBE AF".

   00000000: dead beaf 0000 0000 0000 0000 0000 0000  ................
   00000000: 00de adbe af00 0000 0000 0000 0000 0000  ................

2) If the byte sequence continues on a new line, i.e.

   00000000: 0000 0000 0000 0000 0000 0000 0000 dead  ................
   00000010: beaf 0000 0000 0000 0000 0000 0000 0000  ................

   Then it is impossible to find the string at all.

Cheers, Alfred.

hexl-mode: searching for multi byte sequence?

[Stephen J. Turnbull]

Alfred M. Szmidt writes:
 > Is there some way in hexl-mode to  search for a (hex, octal, ...) byte
 > sequence?  Currently, C-s behaves a  bit strange in at least two regards:
 > 
 > 1) If  file contains  the byte sequence  #xDEADBEAF, depending  on how
 >    they are  aligned (odd  or even  word), one has  to look  for "DEAD
 >    BEAF" and "DE ADBE AF".

C-u C-s de\(.\n\)*ad\(.\|\n\)*be\(.\|\n\)*af

is what I'd use.  It has obvious defects, and it would be nice if
hexl-mode provided something a little less greedy (eg a transformation
to a 3-armed disjunction allowing at most one newline plus handling
the leading byte number after the newline).

Re: hexl-mode: searching for multi byte sequence?

[Eli Zaretskii]

> From: "Stephen J. Turnbull" <stephen@xemacs.org>
> Date: Tue, 14 Jul 2015 16:07:47 +0900
> Cc: emacs-devel@gnu.org
> 
> Alfred M. Szmidt writes:
>  > Is there some way in hexl-mode to  search for a (hex, octal, ...) byte
>  > sequence?  Currently, C-s behaves a  bit strange in at least two regards:
>  > 
>  > 1) If  file contains  the byte sequence  #xDEADBEAF, depending  on how
>  >    they are  aligned (odd  or even  word), one has  to look  for "DEAD
>  >    BEAF" and "DE ADBE AF".
> 
> C-u C-s de\(.\n\)*ad\(.\|\n\)*be\(.\|\n\)*af
> 
> is what I'd use.  It has obvious defects, and it would be nice if
> hexl-mode provided something a little less greedy (eg a transformation
> to a 3-armed disjunction allowing at most one newline plus handling
> the leading byte number after the newline).

Hexl already provides something similar, see
hexl-isearch-search-function.  It allows to search in the text column
strings that span multiple lines, for example.  It should be enhanced
to support Alfred's use case (and somebody please document it!).