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 - return number of on-bit
  21 uint8_t bitpop(uint8_t bits)
  22 {
  23     uint8_t c;
  24     for (c = 0; bits; c++)
  25         bits &= bits - 1;
  26     return c;
  27 /*
  28     const uint8_t bit_count[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
  29     return bit_count[bits>>4] + bit_count[bits&0x0F]
  30 */
  31 }
  32
  33 uint8_t bitpop16(uint16_t bits)
  34 {
  35     uint8_t c;
  36     for (c = 0; bits; c++)
  37         bits &= bits - 1;
  38     return c;
  39 }
  40
  41 uint8_t bitpop32(uint32_t bits)
  42 {
  43     uint8_t c;
  44     for (c = 0; bits; c++)
  45         bits &= bits - 1;
  46     return c;
  47 }
  48
  49 // most significant on-bit - return highest location of on-bit
  50 // NOTE: return 0 when bit0 is on or all bits are off
  51 uint8_t biton(uint8_t bits)
  52 {
  53     uint8_t n = 0;
  54     if (bits >> 4) { bits >>= 4; n += 4;}
  55     if (bits >> 2) { bits >>= 2; n += 2;}
  56     if (bits >> 1) { bits >>= 1; n += 1;}
  57     return n;
  58 }
  59
  60 uint8_t biton16(uint16_t bits)
  61 {
  62     uint8_t n = 0;
  63     if (bits >> 8) { bits >>= 8; n += 8;}
  64     if (bits >> 4) { bits >>= 4; n += 4;}
  65     if (bits >> 2) { bits >>= 2; n += 2;}
  66     if (bits >> 1) { bits >>= 1; n += 1;}
  67     return n;
  68 }
  69
  70 uint8_t biton32(uint32_t bits)
  71 {
  72     uint8_t n = 0;
  73     if (bits >>16) { bits >>=16; n +=16;}
  74     if (bits >> 8) { bits >>= 8; n += 8;}
  75     if (bits >> 4) { bits >>= 4; n += 4;}
  76     if (bits >> 2) { bits >>= 2; n += 2;}
  77     if (bits >> 1) { bits >>= 1; n += 1;}
  78     return n;
  79 }
  80
  81
  82
  83 uint8_t bitrev(uint8_t bits)
  84 {
  85     bits = (bits & 0x0f)<<4 | (bits & 0xf0)>>4;
  86     bits = (bits & 0b00110011)<<2 | (bits & 0b11001100)>>2;
  87     bits = (bits & 0b01010101)<<1 | (bits & 0b10101010)>>1;
  88     return bits;
  89 }
  90
  91 uint16_t bitrev16(uint16_t bits)
  92 {
  93     bits = bitrev(bits & 0x00ff)<<8 | bitrev((bits & 0xff00)>>8);
  94     return bits;
  95 }
  96
  97 uint32_t bitrev32(uint32_t bits)
  98 {
  99     bits = (uint32_t)bitrev16(bits & 0x0000ffff)<<16 | bitrev16((bits & 0xffff0000)>>16);
 100     return bits;
 101 }