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Index > Macroinstructions > Calculate string len and split cmp parts.

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Roman



Joined: 21 Apr 2012
Posts: 1718
Roman 10 Jun 2023, 15:04
I want write macro calculate string len and split camp parts.
Code:
Cmpstring txt,"a","bc","word","sounds01","invisible"
;do

Cmp byte [txt],"a"
Cmp word [txt],"bc"
Cmp dword [txt],"word"
;but how generated chain cmps for "sounds01" or "invisible" ?
Cmp dword [txt],"soun"
Cmp dword [txt+4],"ds01"
;Somehow divided len/4 and get two dwords and one byte for cmp
Cmp dword [txt],"invi"
Cmp dword [txt+4],"sibl"
Cmp byte [txt+8],"e"
    

I do not want write in macro if len = 8 do two cmp.
And write If len = 9 do three cmp.

Because I must write in macro different if for different words.
I don't want do this, because macro Cmpstring will become too big.


Last edited by Roman on 10 Jun 2023, 15:18; edited 4 times in total
Post 10 Jun 2023, 15:04
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 20212
Location: In your JS exploiting you and your system
revolution 10 Jun 2023, 15:08
Use a hash of the string as an identifier.

Or:
Code:
rep cmpsb    
Post 10 Jun 2023, 15:08
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Roman



Joined: 21 Apr 2012
Posts: 1718
Roman 10 Jun 2023, 15:11
Quote:
rep cmpsb

Then I must using edi,esi,ecx.
Sometimes its not handful.

If I have three words I must do three times rep cmpsb

I found memcmp str1,str2,len
Post 10 Jun 2023, 15:11
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bitRAKE



Joined: 21 Jul 2003
Posts: 3977
Location: vpcmipstrm
bitRAKE 11 Jun 2023, 13:02
There is this pattern I like to use: It consists of building a string on the stack (in reverse part order), and then I gather all the parts together:
Code:
macro MULTICATA ; 21 bytes
        local more_strings, more_characters, no_more_strings
more_strings:
        pop rcx
        jrcxz no_more_strings
more_characters:
        mov al, [rcx]
        inc rcx
        test al, al
        jz more_strings
        mov [rdx], al
        inc rdx
        jmp more_characters
no_more_strings:
        mov [rdx], cl
end macro    
... I was wondering if such a pattern might help your work here?

Would it help to programmatically construct your comparison target values on the stack, and then perform the comparison? I am perhaps completely wrong and have wasted your time.
Post 11 Jun 2023, 13:02
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