LXR linux/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 hweight32(unsigned int w)
  13{
  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;
  19}
  20EXPORT_SYMBOL(hweight32);
  21
  22unsigned int hweight16(unsigned int w)
  23{
  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;
  28}
  29EXPORT_SYMBOL(hweight16);
  30
  31unsigned int hweight8(unsigned int w)
  32{
  33        unsigned int res = w - ((w >> 1) & 0x55);
  34        res = (res & 0x33) + ((res >> 2) & 0x33);
  35        return (res + (res >> 4)) & 0x0F;
  36}
  37EXPORT_SYMBOL(hweight8);
  38
  39unsigned long hweight64(__u64 w)
  40{
  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;
  49#else
  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;
  56#endif
  57#endif
  58}
  59EXPORT_SYMBOL(hweight64);
  60