kernel/generic/include/bitops.h

   1 /*
   2  * Copyright (c) 2006 Ondrej Palkovsky
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * - Redistributions of source code must retain the above copyright
  10  *   notice, this list of conditions and the following disclaimer.
  11  * - Redistributions in binary form must reproduce the above copyright
  12  *   notice, this list of conditions and the following disclaimer in the
  13  *   documentation and/or other materials provided with the distribution.
  14  * - The name of the author may not be used to endorse or promote products
  15  *   derived from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /** @addtogroup generic
  30  * @{
  31  */
  32 /** @file
  33  */
  34
  35 #ifndef KERN_BITOPS_H_
  36 #define KERN_BITOPS_H_
  37
  38 #include <typedefs.h>
  39
  40
  41 /** Return position of first non-zero bit from left (i.e. [log_2(arg)]).
  42  *
  43  * If number is zero, it returns 0
  44  */
  45 static inline int fnzb32(uint32_t arg)
  46 {
  47         int n = 0;
  48
  49         if (arg >> 16) {
  50                 arg >>= 16;
  51                 n += 16;
  52         }
  53
  54         if (arg >> 8) {
  55                 arg >>= 8;
  56                 n += 8;
  57         }
  58
  59         if (arg >> 4) {
  60                 arg >>= 4;
  61                 n += 4;
  62         }
  63
  64         if (arg >> 2) {
  65                 arg >>= 2;
  66                 n += 2;
  67         }
  68
  69         if (arg >> 1) {
  70                 arg >>= 1;
  71                 n += 1;
  72         }
  73
  74         return n;
  75 }
  76
  77 static inline int fnzb64(uint64_t arg)
  78 {
  79         int n = 0;
  80
  81         if (arg >> 32) {
  82                 arg >>= 32;
  83                 n += 32;
  84         }
  85
  86         return n + fnzb32((uint32_t) arg);
  87 }
  88
  89 #define fnzb(x) fnzb32(x)
  90
  91 #endif
  92
  93 /** @}
  94  */