lib/hweight.c

   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
  12 unsigned int __sw_hweight32(unsigned int w)
  13 {
  14 #ifdef CONFIG_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 }
  27 EXPORT_SYMBOL(__sw_hweight32);
  28
  29 unsigned 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 }
  36 EXPORT_SYMBOL(__sw_hweight16);
  37
  38 unsigned 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 }
  44 EXPORT_SYMBOL(__sw_hweight8);
  45
  46 unsigned 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 CONFIG_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 }
  67 EXPORT_SYMBOL(__sw_hweight64);