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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 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.  */
  95.