Root/lib/hweight.c

1#include <linux/module.h>
2#include <linux/bitops.h>
3#include <asm/types.h>
4
5/**
6 * hweightN - returns the hamming weight of a N-bit word
7 * @x: the word to weigh
8 *
9 * The Hamming Weight of a number is the total number of bits set in it.
10 */
11
12unsigned int __sw_hweight32(unsigned int w)
13{
14#ifdef ARCH_HAS_FAST_MULTIPLIER
15    w -= (w >> 1) & 0x55555555;
16    w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
17    w = (w + (w >> 4)) & 0x0f0f0f0f;
18    return (w * 0x01010101) >> 24;
19#else
20    unsigned int res = w - ((w >> 1) & 0x55555555);
21    res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
22    res = (res + (res >> 4)) & 0x0F0F0F0F;
23    res = res + (res >> 8);
24    return (res + (res >> 16)) & 0x000000FF;
25#endif
26}
27EXPORT_SYMBOL(__sw_hweight32);
28
29unsigned int __sw_hweight16(unsigned int w)
30{
31    unsigned int res = w - ((w >> 1) & 0x5555);
32    res = (res & 0x3333) + ((res >> 2) & 0x3333);
33    res = (res + (res >> 4)) & 0x0F0F;
34    return (res + (res >> 8)) & 0x00FF;
35}
36EXPORT_SYMBOL(__sw_hweight16);
37
38unsigned int __sw_hweight8(unsigned int w)
39{
40    unsigned int res = w - ((w >> 1) & 0x55);
41    res = (res & 0x33) + ((res >> 2) & 0x33);
42    return (res + (res >> 4)) & 0x0F;
43}
44EXPORT_SYMBOL(__sw_hweight8);
45
46unsigned long __sw_hweight64(__u64 w)
47{
48#if BITS_PER_LONG == 32
49    return __sw_hweight32((unsigned int)(w >> 32)) +
50           __sw_hweight32((unsigned int)w);
51#elif BITS_PER_LONG == 64
52#ifdef ARCH_HAS_FAST_MULTIPLIER
53    w -= (w >> 1) & 0x5555555555555555ul;
54    w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
55    w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
56    return (w * 0x0101010101010101ul) >> 56;
57#else
58    __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
59    res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
60    res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
61    res = res + (res >> 8);
62    res = res + (res >> 16);
63    return (res + (res >> 32)) & 0x00000000000000FFul;
64#endif
65#endif
66}
67EXPORT_SYMBOL(__sw_hweight64);
68

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