include/linux/bitops.h

   1 #ifndef _LINUX_BITOPS_H
   2 #define _LINUX_BITOPS_H
   3
   4
   5 /*
   6  * ffs: find first bit set. This is defined the same way as
   7  * the libc and compiler builtin ffs routines, therefore
   8  * differs in spirit from the above ffz (man ffs).
   9  */
  10
  11 static inline int generic_ffs(int x)
  12 {
  13         int r = 1;
  14
  15         if (!x)
  16                 return 0;
  17         if (!(x & 0xffff)) {
  18                 x >>= 16;
  19                 r += 16;
  20         }
  21         if (!(x & 0xff)) {
  22                 x >>= 8;
  23                 r += 8;
  24         }
  25         if (!(x & 0xf)) {
  26                 x >>= 4;
  27                 r += 4;
  28         }
  29         if (!(x & 3)) {
  30                 x >>= 2;
  31                 r += 2;
  32         }
  33         if (!(x & 1)) {
  34                 x >>= 1;
  35                 r += 1;
  36         }
  37         return r;
  38 }
  39
  40 /*
  41  * hweightN: returns the hamming weight (i.e. the number
  42  * of bits set) of a N-bit word
  43  */
  44
  45 static inline unsigned int generic_hweight32(unsigned int w)
  46 {
  47         unsigned int res = (w & 0x55555555) + ((w >> 1) & 0x55555555);
  48         res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
  49         res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
  50         res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
  51         return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
  52 }
  53
  54 static inline unsigned int generic_hweight16(unsigned int w)
  55 {
  56         unsigned int res = (w & 0x5555) + ((w >> 1) & 0x5555);
  57         res = (res & 0x3333) + ((res >> 2) & 0x3333);
  58         res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F);
  59         return (res & 0x00FF) + ((res >> 8) & 0x00FF);
  60 }
  61
  62 static inline unsigned int generic_hweight8(unsigned int w)
  63 {
  64         unsigned int res = (w & 0x55) + ((w >> 1) & 0x55);
  65         res = (res & 0x33) + ((res >> 2) & 0x33);
  66         return (res & 0x0F) + ((res >> 4) & 0x0F);
  67 }
  68
  69 #include <asm/bitops.h>
  70
  71
  72 #endif