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
  12 unsigned 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 }
  20 EXPORT_SYMBOL(hweight32);
  21
  22 unsigned 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 }
  29 EXPORT_SYMBOL(hweight16);
  30
  31 unsigned 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 }
  37 EXPORT_SYMBOL(hweight8);
  38
  39 unsigned 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 }
  59 EXPORT_SYMBOL(hweight64);