src/main/common/encoding.c

   1 /*
   2  * This file is part of Cleanflight.
   3  *
   4  * Cleanflight 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 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * Cleanflight 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 Cleanflight.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include "platform.h"
  19
  20 #include "encoding.h"
  21
  22 /**
  23  * Cast the in-memory representation of the given float directly to an int.
  24  *
  25  * This is useful for printing the hex representation of a float number (which is considerably cheaper
  26  * than a full decimal float formatter, in both code size and output length).
  27  */
  28 uint32_t castFloatBytesToInt(float f)
  29 {
  30     union floatConvert_t {
  31         float f;
  32         uint32_t u;
  33     } floatConvert;
  34
  35     floatConvert.f = f;
  36
  37     return floatConvert.u;
  38 }
  39
  40 /**
  41  * ZigZag encoding maps all values of a signed integer into those of an unsigned integer in such
  42  * a way that numbers of small absolute value correspond to small integers in the result.
  43  *
  44  * (Compared to just casting a signed to an unsigned which creates huge resulting numbers for
  45  * small negative integers).
  46  */
  47 uint32_t zigzagEncode(int32_t value)
  48 {
  49     return (uint32_t)((value << 1) ^ (value >> 31));
  50 }