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  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 _BITOPS_H_
  36. #define _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(__u32 arg)
  46. {
  47.     int n = 0;
  48.  
  49.     if (arg >> 16) { arg >>= 16;n += 16;}
  50.     if (arg >> 8) { arg >>= 8; n += 8;}
  51.     if (arg >> 4) { arg >>= 4; n += 4;}
  52.     if (arg >> 2) { arg >>= 2; n+=2;}
  53.     if (arg >> 1) { arg >>= 1; n+=1;}
  54.     return n;
  55. }
  56.  
  57. static inline int fnzb64(__u64 arg)
  58. {
  59.     int n = 0;
  60.  
  61.     if (arg >> 32) { arg >>= 32;n += 32;}
  62.     return n + fnzb32((__u32) arg);
  63. }
  64.  
  65. #define fnzb(x) fnzb32(x)
  66.  
  67. #endif
  68.  
  69.  /** @}
  70.  */
  71.  
  72.