From 3b9ed1a5d2d121f32d2cb4f2b05f1fc57c99c946 Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Sun, 26 Mar 2006 01:39:13 -0800 Subject: [PATCH] [PATCH] bitops: generic hweight{64,32,16,8}() This patch introduces the C-language equivalents of the functions below: unsigned int hweight32(unsigned int w); unsigned int hweight16(unsigned int w); unsigned int hweight8(unsigned int w); unsigned long hweight64(__u64 w); In include/asm-generic/bitops/hweight.h This code largely copied from: include/linux/bitops.h Signed-off-by: Akinobu Mita Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/bitops/hweight.h | 9 +++++ lib/Makefile | 1 + lib/hweight.c | 54 ++++++++++++++++++++++++++++ 3 files changed, 64 insertions(+) create mode 100644 include/asm-generic/bitops/hweight.h create mode 100644 lib/hweight.c diff --git a/include/asm-generic/bitops/hweight.h b/include/asm-generic/bitops/hweight.h new file mode 100644 index 0000000000..8be6f17d6a --- /dev/null +++ b/include/asm-generic/bitops/hweight.h @@ -0,0 +1,9 @@ +#ifndef _ASM_GENERIC_BITOPS_HWEIGHT_H_ +#define _ASM_GENERIC_BITOPS_HWEIGHT_H_ + +extern unsigned int hweight32(unsigned int w); +extern unsigned int hweight16(unsigned int w); +extern unsigned int hweight8(unsigned int w); +extern unsigned long hweight64(__u64 w); + +#endif /* _ASM_GENERIC_BITOPS_HWEIGHT_H_ */ diff --git a/lib/Makefile b/lib/Makefile index f827e3c24e..b830c9a155 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -23,6 +23,7 @@ lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o lib-$(CONFIG_SEMAPHORE_SLEEPERS) += semaphore-sleepers.o lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o +lib-$(CONFIG_GENERIC_HWEIGHT) += hweight.o obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o diff --git a/lib/hweight.c b/lib/hweight.c new file mode 100644 index 0000000000..721a4b8b4f --- /dev/null +++ b/lib/hweight.c @@ -0,0 +1,54 @@ +#include +#include + +/** + * hweightN - returns the hamming weight of a N-bit word + * @x: the word to weigh + * + * The Hamming Weight of a number is the total number of bits set in it. + */ + +unsigned int hweight32(unsigned int w) +{ + unsigned int res = (w & 0x55555555) + ((w >> 1) & 0x55555555); + res = (res & 0x33333333) + ((res >> 2) & 0x33333333); + res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F); + res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF); + return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF); +} +EXPORT_SYMBOL(hweight32); + +unsigned int hweight16(unsigned int w) +{ + unsigned int res = (w & 0x5555) + ((w >> 1) & 0x5555); + res = (res & 0x3333) + ((res >> 2) & 0x3333); + res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F); + return (res & 0x00FF) + ((res >> 8) & 0x00FF); +} +EXPORT_SYMBOL(hweight16); + +unsigned int hweight8(unsigned int w) +{ + unsigned int res = (w & 0x55) + ((w >> 1) & 0x55); + res = (res & 0x33) + ((res >> 2) & 0x33); + return (res & 0x0F) + ((res >> 4) & 0x0F); +} +EXPORT_SYMBOL(hweight8); + +unsigned long hweight64(__u64 w) +{ +#if BITS_PER_LONG == 32 + return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w); +#elif BITS_PER_LONG == 64 + u64 res; + res = (w & 0x5555555555555555ul) + ((w >> 1) & 0x5555555555555555ul); + res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul); + res = (res & 0x0F0F0F0F0F0F0F0Ful) + ((res >> 4) & 0x0F0F0F0F0F0F0F0Ful); + res = (res & 0x00FF00FF00FF00FFul) + ((res >> 8) & 0x00FF00FF00FF00FFul); + res = (res & 0x0000FFFF0000FFFFul) + ((res >> 16) & 0x0000FFFF0000FFFFul); + return (res & 0x00000000FFFFFFFFul) + ((res >> 32) & 0x00000000FFFFFFFFul); +#else +#error BITS_PER_LONG not defined +#endif +} +EXPORT_SYMBOL(hweight64); -- 2.39.5