src/system/libroot/posix/string/ffs.cpp

   1 /*
   2  * Copyright 2005, Ingo Weinhold, bonefish@users.sf.net.
   3  * Distributed under the terms of the MIT License.
   4  */
   5
   6 #include <strings.h>
   7
   8 // find first (least significant) set bit
   9 int
  10 ffs(int value)
  11 {
  12         if (!value)
  13                 return 0;
  14
  15         // ToDo: This can certainly be optimized (e.g. by binary search). Or not
  16         // unlikely there's a single assembler instruction...
  17         for (int i = 1; i <= (int)sizeof(value) * 8; i++, value >>= 1) {
  18                 if (value & 1)
  19                         return i;
  20         }
  21
  22         // never gets here
  23         return 0;
  24 }