Example:

rol() { num="$@" ; pre=$((num<<13)) ; suf=$((num>>19)) ;
num=$((pre^suf)) ; num=$((num&0xffffffff)) ; echo "$num" ; }

What tricks will make this more efficient in Bash?

--
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SugarBug <3883@sugar.bug> writes:

Example:

rol() { num="$@" ; pre=$((num<<13)) ; suf=$((num>>19)) ;
num=$((pre^suf)) ; num=$((num&0xffffffff)) ; echo "$num" ; }

What tricks will make this more efficient in Bash?

If you can be sure the input will never be 0xffffffff, then this should
work:

rol () { echo "$(($1*8192%0xffffffff))" ; }

Phil
--
We are no longer hunters and nomads. No longer awed and frightened, as we have gained some understanding of the world in which we live. As such, we can cast aside childish remnants from the dawn of our civilization.
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On 2024-05-11 17:37, Phil Carmody wrote:

SugarBug <3883@sugar.bug> writes:

Example:

rol() { num="$@" ; pre=$((num<<13)) ; suf=$((num>>19)) ;
num=$((pre^suf)) ; num=$((num&0xffffffff)) ; echo "$num" ; }

What tricks will make this more efficient in Bash?

If you can be sure the input will never be 0xffffffff, then this should
work:

rol () { echo "$(($1*8192%0xffffffff))" ; }

Phil

rol13() { printf '0x%X' $(((($1<<13)+($1>>19))&0xffffffff))
}

Avoids that limitation, but may be slightly slower depending on bash inefficiencies.


Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S. https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10
This public discussion message is non-binding and may contain errors.
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