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AP_Math: Add fletcher16 CRC

This commit is contained in:
Michael du Breuil 2021-03-02 11:48:34 -07:00 committed by WickedShell
parent 584a1f8c49
commit 32fd21592a
2 changed files with 16 additions and 2 deletions
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14
libraries/AP_Math/crc.cpp
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@ -387,7 +387,7 @@ uint16_t crc16_ccitt_GDL90(const uint8_t *buf, uint32_t len, uint16_t crc)
* @param [in] len size of buffer
* @return CRC value
*/
uint16_t calc_crc_modbus(uint8_t *buf, uint16_t len)
uint16_t calc_crc_modbus(const uint8_t *buf, uint16_t len)
{
uint16_t crc = 0xFFFF;
for (uint16_t pos = 0; pos < len; pos++) {
@ -405,6 +405,18 @@ uint16_t calc_crc_modbus(uint8_t *buf, uint16_t len)
return crc;
}
// fletcher 16 implementation
uint16_t crc_fletcher16(const uint8_t *buffer, uint32_t len) {
uint16_t c0 = 0;
uint16_t c1 = 0;
for (uint32_t i = 0; i < len; i++) {
c0 = (c0 + buffer[i]) % 255;
c1 = (c1 + c0) % 255;
}
return (c1 << 8) | c0;
}
// FNV-1a implementation
#define FNV_1_PRIME_64 1099511628211UL
void hash_fnv_1a(uint32_t len, const uint8_t* buf, uint64_t* hash)

4
libraries/AP_Math/crc.h
View File

@ -45,7 +45,9 @@ uint16_t crc16_ccitt(const uint8_t *buf, uint32_t len, uint16_t crc);
// https://www.faa.gov/nextgen/programs/adsb/archival/media/gdl90_public_icd_reva.pdf
uint16_t crc16_ccitt_GDL90(const uint8_t *buf, uint32_t len, uint16_t crc);
uint16_t calc_crc_modbus(uint8_t *buf, uint16_t len);
uint16_t calc_crc_modbus(const uint8_t *buf, uint16_t len);
uint16_t crc_fletcher16(const uint8_t * buffer, uint32_t len);
// generate 64bit FNV1a hash from buffer
#define FNV_1_OFFSET_BASIS_64 14695981039346656037UL