Re: modifying hex codes with a regex replace

I don't believe I expressed the problem very well.  My regular expressions works perfectly except for string 2.  String 2 reads in a single character.  I then need to write out a different character, which is related to string 2 by having a hex value 4 more than what was read.  For instance, if string two was an "a", (hex code 61), I would need to print out an "e" (hex code 65), because 61 + 4 = 65.  I would like to do this in gvim because I don't have access to a Perl compiler on the windows machine that will be performing this task. 

 

Thanks again

On Wed, May 25, 2011 at 8:27 PM, Ben Schmidt <mail_ben_schmidt@yahoo.com.au> wrote:

On 26/05/11 1:34 AM, Floobit wrote:

I'm trying to modify a series of binary files made with a legacy
program, and need to change a certain character in my search string to
the character with hex code +4.  For context, here is my sed regex:

:s!^@Heading level 1^@\+.\{-}^@\+\(\d\+\)^@\+Body text^@vel 1^@\+\(\_.
\{1}\)[^D^A^@]\+!^@Body text^@vel 2^@^@\2^@^@^Y#\1^Z

with HEX(^@) =00, etc.  String 2 is only 1 character long, but is
occasionally rendered as a carriage return, thus the need for the \_.
\{1} pattern.  Instead of writing the exact character of string 2, I
need to write the character +4 to its hex code.  For instance, if
HEX(string2)=97, I would need to print ASCII(9b).

To match it, either put it in directly (type Ctrl-V then Ctrl-D to get
^D, for example) or match with \%x outside a collection ( :help /\%x )
or just \x inside a collection ( :help /\] ).

To include it in the substitution, either put it in directly (except
there are a few oddities, e.g. with \n or ^J representing null--:help
sub-replace-special) or use an expression (:help sub-replace-expression)
which can use nr2char() (:help nr2char()) or \x in a string (:help
expr-string).

Here's one option, avoiding using control characters, which means it's
robust in something like .vimrc as encoding changes won't come into
play, it turns out something like this:

:s!\%x00Heading level 1\%x00\+.\{-}\%x00\+\(\d\+\)\%x00\+
\Body text\%x00vel 1\%x00\+\(\_. \)[\x04\x01\x00]\+!
\\="\x00Body text\x00vel 2\x00\x00".submatch(2).
\"\x00\x00\x19#".submatch(1)."\x1a"

(The backslashes at the beginnings of lines are just for line
continuation if including in a .vimrc or script; omit them if you're
joining the lines together, e.g. on the commandline.)

I have no idea why you would use \{1}, so I omitted it, too. I may have
made a bunch more booboos if I didn't understand the original regex
(e.g. because sed has differences to Vim, which I know it does, but am
not sure on any specifics).

There are many, many other possible ways of achieving the same, too, so
the above is just one opinion....

Ben.

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