tmk_core/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     uint8_t c;
  23     for (c = 0; bits; c++) bits &= bits - 1;
  24     return c;
  25     /*
  26         const uint8_t bit_count[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
  27         return bit_count[bits>>4] + bit_count[bits&0x0F]
  28     */
  29 }
  30
  31 uint8_t bitpop16(uint16_t bits) {
  32     uint8_t c;
  33     for (c = 0; bits; c++) bits &= bits - 1;
  34     return c;
  35 }
  36
  37 uint8_t bitpop32(uint32_t bits) {
  38     uint8_t c;
  39     for (c = 0; bits; c++) bits &= bits - 1;
  40     return c;
  41 }
  42
  43 // most significant on-bit - return highest location of on-bit
  44 // NOTE: return 0 when bit0 is on or all bits are off
  45 uint8_t biton(uint8_t bits) {
  46     uint8_t n = 0;
  47     if (bits >> 4) {
  48         bits >>= 4;
  49         n += 4;
  50     }
  51     if (bits >> 2) {
  52         bits >>= 2;
  53         n += 2;
  54     }
  55     if (bits >> 1) {
  56         bits >>= 1;
  57         n += 1;
  58     }
  59     return n;
  60 }
  61
  62 uint8_t biton16(uint16_t bits) {
  63     uint8_t n = 0;
  64     if (bits >> 8) {
  65         bits >>= 8;
  66         n += 8;
  67     }
  68     if (bits >> 4) {
  69         bits >>= 4;
  70         n += 4;
  71     }
  72     if (bits >> 2) {
  73         bits >>= 2;
  74         n += 2;
  75     }
  76     if (bits >> 1) {
  77         bits >>= 1;
  78         n += 1;
  79     }
  80     return n;
  81 }
  82
  83 uint8_t biton32(uint32_t bits) {
  84     uint8_t n = 0;
  85     if (bits >> 16) {
  86         bits >>= 16;
  87         n += 16;
  88     }
  89     if (bits >> 8) {
  90         bits >>= 8;
  91         n += 8;
  92     }
  93     if (bits >> 4) {
  94         bits >>= 4;
  95         n += 4;
  96     }
  97     if (bits >> 2) {
  98         bits >>= 2;
  99         n += 2;
 100     }
 101     if (bits >> 1) {
 102         bits >>= 1;
 103         n += 1;
 104     }
 105     return n;
 106 }
 107
 108 uint8_t bitrev(uint8_t bits) {
 109     bits = (bits & 0x0f) << 4 | (bits & 0xf0) >> 4;
 110     bits = (bits & 0b00110011) << 2 | (bits & 0b11001100) >> 2;
 111     bits = (bits & 0b01010101) << 1 | (bits & 0b10101010) >> 1;
 112     return bits;
 113 }
 114
 115 uint16_t bitrev16(uint16_t bits) {
 116     bits = bitrev(bits & 0x00ff) << 8 | bitrev((bits & 0xff00) >> 8);
 117     return bits;
 118 }
 119
 120 uint32_t bitrev32(uint32_t bits) {
 121     bits = (uint32_t)bitrev16(bits & 0x0000ffff) << 16 | bitrev16((bits & 0xffff0000) >> 16);
 122     return bits;
 123 }