kc3-lang/gnulib/lib/ffsl.h

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• Hash : 1602f0af
  Author :
  Date : 2012-01-01T10:04:58
  

  maint: update all copyright year number ranges
  
  Run "make update-copyright".
  

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• lib/ffsl.h

• /* ffsl.h -- find the first set bit in a word.
     Copyright (C) 2011-2012 Free Software Foundation, Inc.
  
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 3 of the License, or
     (at your option) any later version.
  
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  
  /* Written by Eric Blake.  */
  
  /* This file is meant to be included by ffsl.c and ffsll.c, after
     they have defined FUNC and TYPE.  */
  
  #include <config.h>
  
  /* Specification.  */
  #include <string.h>
  
  #include <limits.h>
  #include <strings.h>
  
  #if !defined FUNC || !defined TYPE
  # error
  #endif
  
  int
  FUNC (TYPE i)
  {
  #if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)) && defined GCC_BUILTIN
    return GCC_BUILTIN (i);
  #else
    unsigned TYPE j = i;
    /* Split j into chunks, and look at one chunk after the other.  */
    enum { chunk_bits = CHAR_BIT * sizeof (unsigned int) };
    /* The number of chunks is ceil (sizeof (TYPE) / sizeof (unsigned int))
       = (sizeof (TYPE) - 1) / sizeof (unsigned int) + 1. */
    enum { chunk_count = (sizeof (TYPE) - 1) / sizeof (unsigned int) + 1 };
  
    if (chunk_count > 1)
      {
        size_t k;
  
        /* It is tempting to write  if (!j)  here, but if we do this,
           Solaris 10/x86 "cc -O" miscompiles the code.  */
        if (!i)
          return 0;
        /* Unroll the first loop round.  k = 0.  */
        if ((unsigned int) j)
          return ffs ((unsigned int) j);
        /* Generic loop.  */
        for (k = 1; k < chunk_count - 1; k++)
          if ((unsigned int) (j >> (k * chunk_bits)) != 0)
            return k * chunk_bits + ffs ((unsigned int) (j >> (k * chunk_bits)));
      }
    /* Last loop round.  k = chunk_count - 1.  */
    return (chunk_count - 1) * chunk_bits
           + ffs ((unsigned int) (j >> ((chunk_count - 1) * chunk_bits)));
  #endif
  }
  

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