Flesh out the api a bit, done in the same style as the 32-bit
version. Currently there are hand-rolled versions elsewhere
in the tree that can be consolidated.
Signed-off-by: Harvey Harrison <[email protected]>
---
Andrew, once this is in I'll feed the patches replacing hand-rolled
versions of this through appropriate maintainers.
include/linux/bitops.h | 40 ++++++++++++++++++++++++++++++++++++++++
1 files changed, 40 insertions(+), 0 deletions(-)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 69c1edb..40d5473 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -65,6 +65,46 @@ static inline __u32 ror32(__u32 word, unsigned int shift)
return (word >> shift) | (word << (32 - shift));
}
+/**
+ * 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));
+}
+
+/**
+ * ror16 - rotate a 16-bit value right
+ * @word: value to rotate
+ * @shift: bits to roll
+ */
+static inline __u16 ror16(__u16 word, unsigned int shift)
+{
+ return (word >> shift) | (word << (16 - shift));
+}
+
+/**
+ * rol8 - rotate an 8-bit value left
+ * @word: value to rotate
+ * @shift: bits to roll
+ */
+static inline __u8 rol8(__u8 word, unsigned int shift)
+{
+ return (word << shift) | (word >> (8 - shift));
+}
+
+/**
+ * ror8 - rotate an 8-bit value right
+ * @word: value to rotate
+ * @shift: bits to roll
+ */
+static inline __u8 ror8(__u8 word, unsigned int shift)
+{
+ return (word >> shift) | (word << (8 - shift));
+}
+
static inline unsigned fls_long(unsigned long l)
{
if (sizeof(l) == 4)
--
1.5.4.4.592.g32d4c
> +/**
> + * 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.
Segher
Segher Boessenkool <[email protected]> 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, [email protected]
SuSE Linux Products GmbH, Maxfeldstra?e 5, 90409 N?rnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
On Tue, 2008-03-11 at 21:59 +0100, Andreas Schwab wrote:
> Segher Boessenkool <[email protected]> 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.
>
It's the same way rol32/ror32 is done directly above this section, I saw
this as well, but figured that if checking for shift = 0 was wanted, it
would have been there.
So...don't do that ;-)
Harvey
>>> +/**
>>> + * 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,
Erm, yes of course. It is promoted to _signed_ int though, but
that works okay here.
> so this is not a problem in this case.
It still needs documentation for the valid values of "shift".
Segher