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[PATCH] bitops: generic hweight{64,32,16,8}()

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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 <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Akinobu Mita 2006-03-26 01:39:13 -08:00 committed by Linus Torvalds
parent 09020adb61
commit 3b9ed1a5d2
3 changed files with 64 additions and 0 deletions
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9
include/asm-generic/bitops/hweight.h Normal file
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@ -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_ */

1
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

54
lib/hweight.c Normal file
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@ -0,0 +1,54 @@
#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);