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Date: Thu, 19 Nov 2015 10:31:53 +0800 From: Jia He <hejianet@...il.com> To: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org Cc: Andrew Morton <akpm@...ux-foundation.org>, Rasmus Villemoes <linux@...musvillemoes.dk>, Denys Vlasenko <dvlasenk@...hat.com>, Kyungmin Park <kyungmin.park@...sung.com>, Michal Nazarewicz <mina86@...a86.com>, Yury Norov <yury.norov@...il.com>, Tejun Heo <tj@...nel.org>, Martin Kepplinger <martink@...teo.de>, George Spelvin <linux@...izon.com>, Ingo Molnar <mingo@...nel.org>, Arnd Bergmann <arnd@...db.de>, Jia He <hejianet@...il.com> Subject: [PATCH 2/3] lib: Introduce 2 find bit api: all_is_bit_{one,zero} 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@...il.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) +{ + 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) +{ + 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 */ -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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