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 #ifndef __HAVE_ARCH_SW_HWEIGHT
  13 unsigned int __sw_hweight32(unsigned int w)
  14 {
  15 #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  16         w -= (w >> 1) & 0x55555555;
  17         w =  (w & 0x33333333) + ((w >> 2) & 0x33333333);
  18         w =  (w + (w >> 4)) & 0x0f0f0f0f;
  19         return (w * 0x01010101) >> 24;
  20 #else
  21         unsigned int res = w - ((w >> 1) & 0x55555555);
  22         res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
  23         res = (res + (res >> 4)) & 0x0F0F0F0F;
  24         res = res + (res >> 8);
  25         return (res + (res >> 16)) & 0x000000FF;
  26 #endif
  27 }
  28 EXPORT_SYMBOL(__sw_hweight32);
  29 #endif
  30
  31 unsigned int __sw_hweight16(unsigned int w)
  32 {
  33         unsigned int res = w - ((w >> 1) & 0x5555);
  34         res = (res & 0x3333) + ((res >> 2) & 0x3333);
  35         res = (res + (res >> 4)) & 0x0F0F;
  36         return (res + (res >> 8)) & 0x00FF;
  37 }
  38 EXPORT_SYMBOL(__sw_hweight16);
  39
  40 unsigned int __sw_hweight8(unsigned int w)
  41 {
  42         unsigned int res = w - ((w >> 1) & 0x55);
  43         res = (res & 0x33) + ((res >> 2) & 0x33);
  44         return (res + (res >> 4)) & 0x0F;
  45 }
  46 EXPORT_SYMBOL(__sw_hweight8);
  47
  48 #ifndef __HAVE_ARCH_SW_HWEIGHT
  49 unsigned long __sw_hweight64(__u64 w)
  50 {
  51 #if BITS_PER_LONG == 32
  52         return __sw_hweight32((unsigned int)(w >> 32)) +
  53                __sw_hweight32((unsigned int)w);
  54 #elif BITS_PER_LONG == 64
  55 #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  56         w -= (w >> 1) & 0x5555555555555555ul;
  57         w =  (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
  58         w =  (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
  59         return (w * 0x0101010101010101ul) >> 56;
  60 #else
  61         __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
  62         res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
  63         res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
  64         res = res + (res >> 8);
  65         res = res + (res >> 16);
  66         return (res + (res >> 32)) & 0x00000000000000FFul;
  67 #endif
  68 #endif
  69 }
  70 EXPORT_SYMBOL(__sw_hweight64);
  71 #endif