linux/lib/hweight.c
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   1#include <linux/export.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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