LXR linux/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 */
  12static 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_ */
  42