include/asm-generic/bitops/ffs.h

   1 #ifndef _ASM_GENERIC_BITOPS_FFS_H_
   2 #define _ASM_GENERIC_BITOPS_FFS_H_
   3
   4 /**
   5  * ffs - find first bit set
   6  * @x: the word to search
   7  *
   8  * This is defined the same way as
   9  * the libc and compiler builtin ffs routines, therefore
  10  * differs in spirit from the above ffz (man ffs).
  11  */
  12 static inline int ffs(int x)
  13 {
  14         int r = 1;
  15
  16         if (!x)
  17                 return 0;
  18         if (!(x & 0xffff)) {
  19                 x >>= 16;
  20                 r += 16;
  21         }
  22         if (!(x & 0xff)) {
  23                 x >>= 8;
  24                 r += 8;
  25         }
  26         if (!(x & 0xf)) {
  27                 x >>= 4;
  28                 r += 4;
  29         }
  30         if (!(x & 3)) {
  31                 x >>= 2;
  32                 r += 2;
  33         }
  34         if (!(x & 1)) {
  35                 x >>= 1;
  36                 r += 1;
  37         }
  38         return r;
  39 }
  40
  41 #endif /* _ASM_GENERIC_BITOPS_FFS_H_ */