Re: [PATCH] bitops: add 8-bit and 16-bit rotation functions

[Andreas Schwab]

Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> writes:

>> +/**
>> + * rol16 - rotate a 16-bit value left
>> + * @word: value to rotate
>> + * @shift: bits to roll
>> + */
>> +static inline __u16 rol16(__u16 word, unsigned int shift)
>> +{
>> +	return (word << shift) | (word >> (16 - shift));
>> +}
>
> This doesn't work for shift values of 0: you get word >> 16, and
> shifts greater than or equal to the word size aren't valid C.  GCC
> will warn about this, too.

On the other hand, a value narrower than int will always be promoted
first, so this is not a problem in this case.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@xxxxxxx
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/