Cheat Engine

Dr.Disrespect · Posted: Mon Nov 14, 2016 11:43 am Post subject: (ASM) ROL and ROR?

I have two questions.

First, the concept of ROL/ROR. For example, if "al = 01010101",
1) After "rol al,1", does al equal "10101010"?

2) After "rol al,2", does al equal "01010101"?

Second, what's the purpose of ROL/ROR? Can someone translate it into C++? Is it some kind of arithmetic operation?

Thanks a lot.

ParkourPenguin · Posted: Mon Nov 14, 2016 12:10 pm Post subject:

https://en.wikipedia.org/wiki/Circular_shift

Dr.Disrespect · Posted: Mon Nov 14, 2016 12:49 pm Post subject:

Dark Byte · Posted: Mon Nov 14, 2016 12:56 pm Post subject:

multiply is slower than a simple rotate (of course smart cpu's usually detect multiplications by factors of two and turn it into a shift internally anyhow)

Also, for multiplication I recommend shl as it just adds a 0 instead of using a bit that could roll over.

ROL is usually used for encryption or obfuscation uses (e.g some games rotate by 12 just to make things harder to find)

ParkourPenguin · Posted: Mon Nov 14, 2016 12:59 pm Post subject:

In that specific example, bitwise operations are generally simpler, easier, and faster than arithmetic operations. When multiplying by powers of 2, I'd use shl: using mul just seems stupid to me when there's a bitwise operator that can do it faster, and rol makes less sense semantically since bits that overflow would roll over.

For other examples, use Google. e.g.:
http://stackoverflow.com/a/19912005

Dr.Disrespect · Posted: Mon Nov 14, 2016 1:01 pm Post subject: