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git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/blob - lib/hweight.c
1 #include <linux/module.h>
2 #include <linux/bitops.h>
6 * hweightN - returns the hamming weight of a N-bit word
7 * @x: the word to weigh
9 * The Hamming Weight of a number is the total number of bits set in it.
12 unsigned int hweight32(unsigned int w
)
14 unsigned int res
= w
- ((w
>> 1) & 0x55555555);
15 res
= (res
& 0x33333333) + ((res
>> 2) & 0x33333333);
16 res
= (res
+ (res
>> 4)) & 0x0F0F0F0F;
17 res
= res
+ (res
>> 8);
18 return (res
+ (res
>> 16)) & 0x000000FF;
20 EXPORT_SYMBOL(hweight32
);
22 unsigned int hweight16(unsigned int w
)
24 unsigned int res
= w
- ((w
>> 1) & 0x5555);
25 res
= (res
& 0x3333) + ((res
>> 2) & 0x3333);
26 res
= (res
+ (res
>> 4)) & 0x0F0F;
27 return (res
+ (res
>> 8)) & 0x00FF;
29 EXPORT_SYMBOL(hweight16
);
31 unsigned int hweight8(unsigned int w
)
33 unsigned int res
= w
- ((w
>> 1) & 0x55);
34 res
= (res
& 0x33) + ((res
>> 2) & 0x33);
35 return (res
+ (res
>> 4)) & 0x0F;
37 EXPORT_SYMBOL(hweight8
);
39 unsigned long hweight64(__u64 w
)
41 #if BITS_PER_LONG == 32
42 return hweight32((unsigned int)(w
>> 32)) + hweight32((unsigned int)w
);
43 #elif BITS_PER_LONG == 64
44 #ifdef ARCH_HAS_FAST_MULTIPLIER
45 w
-= (w
>> 1) & 0x5555555555555555ul
;
46 w
= (w
& 0x3333333333333333ul
) + ((w
>> 2) & 0x3333333333333333ul
);
47 w
= (w
+ (w
>> 4)) & 0x0f0f0f0f0f0f0f0ful
;
48 return (w
* 0x0101010101010101ul
) >> 56;
50 __u64 res
= w
- ((w
>> 1) & 0x5555555555555555ul
);
51 res
= (res
& 0x3333333333333333ul
) + ((res
>> 2) & 0x3333333333333333ul
);
52 res
= (res
+ (res
>> 4)) & 0x0F0F0F0F0F0F0F0Ful
;
53 res
= res
+ (res
>> 8);
54 res
= res
+ (res
>> 16);
55 return (res
+ (res
>> 32)) & 0x00000000000000FFul
;
59 EXPORT_SYMBOL(hweight64
);