src/main/common/encoding.c

   1 /*
   2  * This file is part of Cleanflight and Betaflight.
   3  *
   4  * Cleanflight and Betaflight are free software. You can redistribute
   5  * this software and/or modify this software under the terms of the
   6  * GNU General Public License as published by the Free Software
   7  * Foundation, either version 3 of the License, or (at your option)
   8  * any later version.
   9  *
  10  * Cleanflight and Betaflight are distributed in the hope that they
  11  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  12  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  13  * See the GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this software.
  17  *
  18  * If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include "encoding.h"
  22
  23 /**
  24  * Cast the in-memory representation of the given float directly to an int.
  25  *
  26  * This is useful for printing the hex representation of a float number (which is considerably cheaper
  27  * than a full decimal float formatter, in both code size and output length).
  28  */
  29 uint32_t castFloatBytesToInt(float f)
  30 {
  31     union floatConvert_t {
  32         float f;
  33         uint32_t u;
  34     } floatConvert;
  35
  36     floatConvert.f = f;
  37
  38     return floatConvert.u;
  39 }
  40
  41 /**
  42  * ZigZag encoding maps all values of a signed integer into those of an unsigned integer in such
  43  * a way that numbers of small absolute value correspond to small integers in the result.
  44  *
  45  * (Compared to just casting a signed to an unsigned which creates huge resulting numbers for
  46  * small negative integers).
  47  */
  48 uint32_t zigzagEncode(int32_t value)
  49 {
  50     return (uint32_t)((value << 1) ^ (value >> 31));
  51 }