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pool



Joined: 08 Jan 2007
Posts: 97
Location: Philippines
pool
..


Last edited by pool on 17 Mar 2013, 12:01; edited 1 time in total
Post 13 Jan 2009, 05:02
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17476
Location: In your JS exploiting you and your system
revolution
JP
JNP
JPO
JPE

Check the Intel/AMD manual to see what flag value each tests for.
Post 13 Jan 2009, 05:08
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DJ Mauretto



Joined: 14 Mar 2007
Posts: 464
Location: Rome,Italy
DJ Mauretto
Hello,
The parity mean the number of bit that are set
Example:
Code:
mov al,1011b
test al,11b                     ; 1011 AND 11 = 11 ( 2 bit set = Parity even)
jp  @Parity


;Example 2:
mov al,101b
test al,1b                     ; 101 AND 1 = 1 ( 1 bit set = Parity odd )
jnp @No_Parity

    

Both jmp are execute Wink

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Nil Volentibus Arduum Razz
Post 13 Jan 2009, 10:19
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pool



Joined: 08 Jan 2007
Posts: 97
Location: Philippines
pool
..


Last edited by pool on 17 Mar 2013, 12:02; edited 1 time in total
Post 14 Jan 2009, 11:13
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Grom PE



Joined: 13 Mar 2008
Posts: 114
Location: i@grompe.org.ru
Grom PE
I don't see jp/jnp in programs often.
Could anyone explain to me when it's useful?
It would be nice to see some uses in real projects, or as list of possibilities.
Post 16 Jan 2009, 03:33
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
Grom PE, you may look here for a sample application. Wink
Post 16 Jan 2009, 04:29
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Grom PE



Joined: 13 Mar 2008
Posts: 114
Location: i@grompe.org.ru
Grom PE
baldr, that's interesting, but not useful enough - very specific case =)
Post 16 Jan 2009, 06:09
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sinsi



Joined: 10 Aug 2007
Posts: 701
Location: Adelaide
sinsi
http://coding.derkeiler.com/Archive/Assembler/comp.lang.asm.x86/2004-10/0310.html
Look at "next in thread" too. Interesting what you find out...
Post 16 Jan 2009, 06:16
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DJ Mauretto



Joined: 14 Mar 2007
Posts: 464
Location: Rome,Italy
DJ Mauretto
Quote:
I don't see jp/jnp in programs often.
Could anyone explain to me when it's useful?
It would be nice to see some uses in real projects, or as list of possibilities.

Read my signature Wink

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Nil Volentibus Arduum Razz
Post 16 Jan 2009, 10:42
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Goplat



Joined: 15 Sep 2006
Posts: 181
Goplat
Suppose you're writing a NES emulator, and you need to classify a memory address into one of the four ranges (0000-1FFF = RAM, 2000-5FFF = memory mapped registers, 6000-7FFF = Save RAM, 8000-FFFF = ROM). Most people would use three comparisons to do this, but the flag-savvy programmer can do it with just one!
Code:
mov bx,[address]
test bh,0E0h
js rom_address             ; 8000-FFFF
jz ram_address           ; 0000-1FFF
jpe sram_address ; 6000-7FFF
jmp register_address     ; 2000-5FFF    
Post 17 Jan 2009, 15:41
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