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/* -*- c++ -*- */
/*
* Copyright 2003 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio 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, or (at your option)
* any later version.
*
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include <gr_count_bits.h>
/*
* these are slow and obvious. If you need something faster, fix these
*/
// return number of set bits in the low 8 bits of x
unsigned int
gr_count_bits8 (unsigned int x)
{
int count = 0;
for (int i = 0; i < 8; i++)
if (x & (1 << i))
count++;
return count;
}
// return number of set bits in the low 16 bits of x
unsigned int
gr_count_bits16 (unsigned int x)
{
int count = 0;
for (int i = 0; i < 16; i++)
if (x & (1 << i))
count++;
return count;
}
#if 0 // slow and obvious
// return number of set bits in the low 32 bits of x
unsigned int
gr_count_bits32 (unsigned int x)
{
int count = 0;
for (int i = 0; i < 32; i++)
if (x & (1 << i))
count++;
return count;
}
#else // fast and not so obvious
// return number of set bits in the low 32 bits of x
unsigned int
gr_count_bits32 (unsigned int x)
{
unsigned res = (x & 0x55555555) + ((x >> 1) & 0x55555555);
res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
}
#endif
// return number of set bits in the low 64 bits of x
unsigned int
gr_count_bits64 (unsigned long long x)
{
return gr_count_bits32((x >> 32) & 0xffffffff) + gr_count_bits32(x & 0xffffffff);
}
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