3 * Copyright 2003 Free Software Foundation, Inc.
5 * This file is part of GNU Radio
7 * GNU Radio is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 3, or (at your option)
12 * GNU Radio is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with GNU Radio; see the file COPYING. If not, write to
19 * the Free Software Foundation, Inc., 51 Franklin Street,
20 * Boston, MA 02110-1301, USA.
23 #include <gr_count_bits.h>
26 * these are slow and obvious. If you need something faster, fix these
29 // return number of set bits in the low 8 bits of x
31 gr_count_bits8 (unsigned int x)
35 for (int i = 0; i < 8; i++)
42 // return number of set bits in the low 16 bits of x
44 gr_count_bits16 (unsigned int x)
48 for (int i = 0; i < 16; i++)
57 #if 0 // slow and obvious
59 // return number of set bits in the low 32 bits of x
61 gr_count_bits32 (unsigned int x)
65 for (int i = 0; i < 32; i++)
72 #else // fast and not so obvious
74 // return number of set bits in the low 32 bits of x
76 gr_count_bits32 (unsigned int x)
78 unsigned res = (x & 0x55555555) + ((x >> 1) & 0x55555555);
79 res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
80 res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
81 res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
82 return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
88 // return number of set bits in the low 64 bits of x
90 gr_count_bits64 (unsigned long long x)
92 return gr_count_bits32((x >> 32) & 0xffffffff) + gr_count_bits32(x & 0xffffffff);