src/main/common/crc.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 <stdint.h>
  19
  20 #include "streambuf.h"
  21
  22
  23 uint16_t crc16_ccitt(uint16_t crc, unsigned char a)
  24 {
  25     crc ^= (uint16_t)a << 8;
  26     for (int ii = 0; ii < 8; ++ii) {
  27         if (crc & 0x8000) {
  28             crc = (crc << 1) ^ 0x1021;
  29         } else {
  30             crc = crc << 1;
  31         }
  32     }
  33     return crc;
  34 }
  35
  36 uint16_t crc16_ccitt_update(uint16_t crc, const void *data, uint32_t length)
  37 {
  38     const uint8_t *p = (const uint8_t *)data;
  39     const uint8_t *pend = p + length;
  40
  41     for (; p != pend; p++) {
  42         crc = crc16_ccitt(crc, *p);
  43     }
  44     return crc;
  45 }
  46
  47 void crc16_ccitt_sbuf_append(sbuf_t *dst, uint8_t *start)
  48 {
  49     uint16_t crc = 0;
  50     const uint8_t * const end = sbufPtr(dst);
  51     for (const uint8_t *ptr = start; ptr < end; ++ptr) {
  52         crc = crc16_ccitt(crc, *ptr);
  53     }
  54     sbufWriteU16(dst, crc);
  55 }
  56
  57 uint8_t crc8_dvb_s2(uint8_t crc, unsigned char a)
  58 {
  59     crc ^= a;
  60     for (int ii = 0; ii < 8; ++ii) {
  61         if (crc & 0x80) {
  62             crc = (crc << 1) ^ 0xD5;
  63         } else {
  64             crc = crc << 1;
  65         }
  66     }
  67     return crc;
  68 }
  69
  70 uint8_t crc8_dvb_s2_update(uint8_t crc, const void *data, uint32_t length)
  71 {
  72     const uint8_t *p = (const uint8_t *)data;
  73     const uint8_t *pend = p + length;
  74
  75     for (; p != pend; p++) {
  76         crc = crc8_dvb_s2(crc, *p);
  77     }
  78     return crc;
  79 }
  80
  81 void crc8_dvb_s2_sbuf_append(sbuf_t *dst, uint8_t *start)
  82 {
  83     uint8_t crc = 0;
  84     const uint8_t * const end = dst->ptr;
  85     for (const uint8_t *ptr = start; ptr < end; ++ptr) {
  86         crc = crc8_dvb_s2(crc, *ptr);
  87     }
  88     sbufWriteU8(dst, crc);
  89 }
  90
  91 uint8_t crc8_xor_update(uint8_t crc, const void *data, uint32_t length)
  92 {
  93     const uint8_t *p = (const uint8_t *)data;
  94     const uint8_t *pend = p + length;
  95
  96     for (; p != pend; p++) {
  97         crc ^= *p;
  98     }
  99     return crc;
 100 }
 101
 102 void crc8_xor_sbuf_append(sbuf_t *dst, uint8_t *start)
 103 {
 104     uint8_t crc = 0;
 105     const uint8_t *end = dst->ptr;
 106     for (uint8_t *ptr = start; ptr < end; ++ptr) {
 107         crc ^= *ptr;
 108     }
 109     sbufWriteU8(dst, crc);
 110 }
 111