String comparison (64 bit linux)

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orbital_fox

Joined: 08 Sep 2006
Posts: 14

orbital_fox 31 Oct 2006, 09:34

Greetings..

I have finally started to try making something.

I am now trying to make a program, that does a string comparison, but i am having a bit of problem with the data sizes (i think :/)

Here are the parts of tha program related to that:

Code:

        mov     edx,input_buffer_size
        lea     rsi,[input_buffer]
        mov     edi,0
        mov     eax,0   ; see /usr/share/man/man2/read.2.gz
        syscall

 mov rax, input_buffer
 cmp qword[rax], '49' ; I want the input buffer to be compared with the string 49
 je lmsg2

;The messages etc..
;    .
;    .
;    .

segment readable writeable

input_buffer_size       =       0xFFFF
input_buffer            rb      input_buffer_size

The code assembles, but just doesnt work right..

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31 Oct 2006, 09:34

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 31 Oct 2006, 09:43

you must know what is encoding of string. if it's ascii then you just do cmp word [rax], '49', which is equivalent to memcmp((char*)rax, "49", 2)

31 Oct 2006, 09:43

orbital_fox

Joined: 08 Sep 2006
Posts: 14

orbital_fox 31 Oct 2006, 16:50

whats the usuall encoding from a command line input? Is that the one defined in the settings of the command line terminal?

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31 Oct 2006, 16:50

orbital_fox

Joined: 08 Sep 2006
Posts: 14

orbital_fox 31 Oct 2006, 16:54

Thanks! it worked Smile

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31 Oct 2006, 16:54

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