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<== Date ==> <== Thread ==>
Subject: Re: Select MS Bit from an integer
From: Till Straumann <[email protected]>
To: "Dudley, David" <[email protected]>, "[email protected] >> EPICS Techtalk" <[email protected]>
Date: Fri, 4 Sep 2015 09:12:19 -0700
You could do it with a bunch of calc (C1..C5, V) records

 C1 computes  (IN & 0xffff0000)
 C2 computes  (c1 ? c1 : IN ) & 0xff00ff00
 C3 computes  (c2 ? c2 : c1 ? c1 : IN) & 0xf0f0f0f0
 C4 computes  (c3 ? c3 : c2 ? c2 : c1 ? c1 : IN) & 0xcccccccc
 C5 computes  (c4 ? c4 : c3 ? c3 : c2 ? c2 : c1 ? c1 : IN) & 0xaaaaaaaa

V computes  (C1 ? 16 : 0) + (C2 ? 8 : 0) + (C3 ? 4 : 0) + (C4 ? 2 : 0) + (C5 ? 1 : 0)

HTH
- Till
On 09/04/2015 07:59 AM, Dudley, David wrote:

Quick question that I didn’t see an immediate way to perform

 

How do I select the most-significant set bit in an integer?  I was thinking about using a SEL, but that seems like a lot of work just to do a simple thing.  Other possibility would be a SUB, but I’d like to do it with base record types if I can.

 

Something simple please…

 

L

Replies:
Re: Select MS Bit from an integer Andrew Johnson
References:
Select MS Bit from an integer Dudley, David
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