common/util.c

   1 /*
   2 Copyright 2011 Jun Wako <wakojun@gmail.com>
   3
   4 This program is free software: you can redistribute it and/or modify
   5 it under the terms of the GNU General Public License as published by
   6 the Free Software Foundation, either version 2 of the License, or
   7 (at your option) any later version.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16 */
  17
  18 #include "util.h"
  19
  20 // bit population
  21 int bitpop(uint8_t bits)
  22 {
  23     int c;
  24     for (c = 0; bits; c++)
  25         bits &= bits -1;
  26     return c;
  27 }
  28
  29 // most significant on-bit
  30 int biton(uint8_t bits)
  31 {
  32     int n = 0;
  33     if (bits >> 4) { bits >>= 4; n += 4;}
  34     if (bits >> 2) { bits >>= 2; n += 2;}
  35     if (bits >> 1) { bits >>= 1; n += 1;}
  36     return n;
  37 }