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Commit 3b9ed1a5 authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
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[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: default avatarAkinobu Mita <mita@miraclelinux.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 09020adb

include/asm-generic/bitops/hweight.h

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#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_ */

lib/Makefile

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@@ -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

lib/hweight.c

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#include <linux/module.h>

#include <asm/types.h>



/**

 * 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);