Messages in this thread | | | Subject | Re: [PATCH v2 2/3] lib: Introduce 2 bit ops api: all_is_bit_{one,zero} | From | xinhui <> | Date | Thu, 19 Nov 2015 16:40:52 +0800 |
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hi, jia Nice patch. But I have one minor question. see inline comments.
On 2015/11/19 14:48, Jia He wrote: > This patch introduces 2 lightweight bit api. > all_bit_is_zero return 1 if the bit string is all zero. > The addr is the start address, the size is the bit size of the bit string. > all_bit_is_one is the opposite. > > Signed-off-by: Jia He <hejianet@gmail.com> > --- > lib/find_bit.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 50 insertions(+) > > diff --git a/lib/find_bit.c b/lib/find_bit.c > index 18072ea..1d56d8d 100644 > --- a/lib/find_bit.c > +++ b/lib/find_bit.c > @@ -131,6 +131,56 @@ unsigned long find_last_bit(const unsigned long *addr, unsigned long size) > EXPORT_SYMBOL(find_last_bit); > #endif > > +#ifndef all_bit_is_zero > +/* > + * return val: 1 means all bit is zero > + */ > +unsigned int all_bit_is_zero(const unsigned long *addr, unsigned size) > +{ Seems better that size should be type of "unsigned long". Otherwise I'm afraid when we compare idx * BITS_PER_LONG with size, there might be overflow issue.
> + unsigned long idx; > + unsigned long mask = size; > + > + if (unlikely(size == 0)) > + return 1; > + > + if (size > BITS_PER_LONG) { > + for (idx = 0; idx * BITS_PER_LONG < size; idx++) > + if (addr[idx]) > + return 0; > + > + mask = size - (idx - 1) * BITS_PER_LONG; > + } > + > + return !(*addr & BITMAP_LAST_WORD_MASK(mask)); > +} > +EXPORT_SYMBOL(all_bit_is_zero); > +#endif > + > +#ifndef all_bit_is_one > +/* > + * return val: 1 means all bit is one > + */ > +unsigned int all_bit_is_one(const unsigned long *addr, unsigned size) > +{ this argc of size should be type of "unsigned long", too.
thanks xinhui
> + unsigned long idx; > + unsigned long mask = size; > + > + if (unlikely(size == 0)) > + return 1; > + > + if (size > BITS_PER_LONG) { > + for (idx = 0; idx * BITS_PER_LONG < size; idx++) > + if (~addr[idx]) > + return 0; > + > + mask = size - (idx - 1) * BITS_PER_LONG; > + } > + > + return !(~(*addr) & BITMAP_LAST_WORD_MASK(mask)); > +} > +EXPORT_SYMBOL(all_bit_is_one); > +#endif > + > #ifdef __BIG_ENDIAN > > /* include/linux/byteorder does not support "unsigned long" type */ >
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