include/bitops.h

   1 #ifndef __BITOPS_H__
   2 #define __BITOPS_H__
   3
   4 /*
   5  * fls: find last bit set.
   6  */
   7
   8 #ifndef HAVE_FLS
   9 static inline int fls(int x)
  10 {
  11         int r = 32;
  12
  13         if (!x)
  14                 return 0;
  15         if (!(x & 0xffff0000u)) {
  16                 x <<= 16;
  17                 r -= 16;
  18         }
  19         if (!(x & 0xff000000u)) {
  20                 x <<= 8;
  21                 r -= 8;
  22         }
  23         if (!(x & 0xf0000000u)) {
  24                 x <<= 4;
  25                 r -= 4;
  26         }
  27         if (!(x & 0xc0000000u)) {
  28                 x <<= 2;
  29                 r -= 2;
  30         }
  31         if (!(x & 0x80000000u)) {
  32                 r -= 1;
  33         }
  34         return r;
  35 }
  36 #endif /* HAVE_FLS */
  37
  38 static inline int fls64(__u64 x)
  39 {
  40         __u32 h = x >> 32;
  41         if (h)
  42                 return fls(h) + 32;
  43         return fls(x);
  44 }
  45
  46 static inline unsigned fls_long(unsigned long l)
  47 {
  48         if (sizeof(l) == 4)
  49                 return fls(l);
  50         return fls64(l);
  51 }
  52
  53 /*
  54  * ffz: find first zero bit.
  55  * Result is undefined if no zero bit exists.
  56  */
  57 #define ffz(x)  ffs(~(x))
  58
  59 #endif