Hex Rays - strange functions ROL4 and ROR4

Question

What's purpose of functions ROL and ROR? For both of them, first arg is int, and second is byte

I suppose that's bitwise shifts

two muppet[![rol and ror ]1s]2

A simple search for ROR and ROL gives the answer right away https://en.wikipedia.org/wiki/Circular_shift — phuclv, Jul 03 '16 at 05:53
I'd already known that it's some kind of shifts and just needed qualification - at least there're two versions - for 16-bit values (ROR2) and for 32-bit (ROR4). Thanx for @mikfig — Nikolay Matkheev, Jul 04 '16 at 16:41
See BYTE3, does it mean the third or fourth byte of an int? IDB file that's already supplied — Jason Geffner, Jul 04 '16 at 19:27
don't put code in images. Copy and paste here would be much faster and more convenient for others to use — phuclv, Apr 29 '17 at 05:07
Just in case someone find similar code: The series of Rol4 Ror4 are indeed bit rotation, and from the constant we can see it is some MD5 computation. — Chaotikmind, Dec 08 '18 at 11:27

score 5 · Accepted Answer · edited Apr 29 '17 at 19:35

5

Check out IDA directory\plugins\defs.h.

...
// Macros to represent some assembly instructions
// Feel free to modify them

#define __ROL__(x, y) __rotl__(x, y)       // Rotate left
#define __ROR__(x, y) __rotr__(x, y)       // Rotate right
...

The __rotl__ and __rotr__ are just for the rol and ror instructions

edited Apr 29 '17 at 19:35

phuclv

476
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answered Jul 02 '16 at 14:38

mikfig

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Hex Rays - strange functions __ROL4__ and __ROR4__

1 Answers1

Hex Rays - strange functions ROL4 and ROR4