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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.  
  39. /** Return position of first non-zero bit from left (i.e. [log_2(arg)]).
  40.  *
  41.  * If number is zero, it returns 0
  42.  */
  43. static inline int fnzb32(uint32_t arg)
  44. {
  45.     int n = 0;
  46.  
  47.     if (arg >> 16) {
  48.         arg >>= 16;
  49.         n += 16;
  50.     }
  51.    
  52.     if (arg >> 8) {
  53.         arg >>= 8;
  54.         n += 8;
  55.     }
  56.    
  57.     if (arg >> 4) {
  58.         arg >>= 4;
  59.         n += 4;
  60.     }
  61.    
  62.     if (arg >> 2) {
  63.         arg >>= 2;
  64.         n += 2;
  65.     }
  66.    
  67.     if (arg >> 1) {
  68.         arg >>= 1;
  69.         n += 1;
  70.     }
  71.    
  72.     return n;
  73. }
  74.  
  75. static inline int fnzb64(uint64_t arg)
  76. {
  77.     int n = 0;
  78.  
  79.     if (arg >> 32) {
  80.         arg >>= 32;
  81.         n += 32;
  82.     }
  83.    
  84.     return n + fnzb32((uint32_t) arg);
  85. }
  86.  
  87. #define fnzb(x) fnzb32(x)
  88.  
  89. #endif
  90.  
  91. /** @}
  92.  */
  93.