help me :-) [newbie]

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ansik

Joined: 09 Dec 2005
Posts: 6

ansik 21 Dec 2005, 13:16

help me plz. I need algorythm to find and replace hex-codes in binary file.
e.g: 'ff 00 ff 6b' replace to 'f1 02 cc 6a'
help me plz. Smile

21 Dec 2005, 13:16

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8466
Location: Kraków, Poland

Tomasz Grysztar 21 Dec 2005, 17:31

Do you mean replacing some bytes pattern with the same amount of bytes, without shifting the rest of the file?

21 Dec 2005, 17:31

ansik

Joined: 09 Dec 2005
Posts: 6

ansik 21 Dec 2005, 21:11

yes. and which "read block size" use? 1byte is slow (file~3Mb), and in order to use bigger "read block size" i need an algorythm Smile

)

21 Dec 2005, 21:11

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8466
Location: Kraków, Poland

Tomasz Grysztar 21 Dec 2005, 21:50

In which operating system? In Windows you could use the file mapping and thus "read block" wouldn't be necessary at all.

21 Dec 2005, 21:50

Reverend

Joined: 24 Aug 2004
Posts: 408
Location: Poland

Reverend 22 Dec 2005, 20:45

Map whole file. If it's PE .exe/.dll then get to section's data (to prevent searching in headers unless you wish to). Than if it's always dword value you seek, the best solution imho would be using scasd instruction like this:

Code:

        mov     ecx, size / 4
        mov     eax, pattern_you_seek
        mov     edi, start_of_block_to_search_within ; 
        repnz   scasd
        jnz     .not_found

22 Dec 2005, 20:45

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7103
Location: Slovakia

vid 23 Dec 2005, 02:16

look at FASMLIB, file 'fasmlib\str.inc', procedure 'str.pos'

23 Dec 2005, 02:16

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