diff options
Diffstat (limited to 'mavlink/share/pyshared/pymavlink/generator/C/include_v0.9/checksum.h')
-rw-r--r-- | mavlink/share/pyshared/pymavlink/generator/C/include_v0.9/checksum.h | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/mavlink/share/pyshared/pymavlink/generator/C/include_v0.9/checksum.h b/mavlink/share/pyshared/pymavlink/generator/C/include_v0.9/checksum.h new file mode 100644 index 000000000..b70991f5a --- /dev/null +++ b/mavlink/share/pyshared/pymavlink/generator/C/include_v0.9/checksum.h @@ -0,0 +1,89 @@ +#ifdef __cplusplus +extern "C" { +#endif + +#ifndef _CHECKSUM_H_ +#define _CHECKSUM_H_ + + +/** + * + * CALCULATE THE CHECKSUM + * + */ + +#define X25_INIT_CRC 0xffff +#define X25_VALIDATE_CRC 0xf0b8 + +/** + * @brief Accumulate the X.25 CRC by adding one char at a time. + * + * The checksum function adds the hash of one char at a time to the + * 16 bit checksum (uint16_t). + * + * @param data new char to hash + * @param crcAccum the already accumulated checksum + **/ +static inline void crc_accumulate(uint8_t data, uint16_t *crcAccum) +{ + /*Accumulate one byte of data into the CRC*/ + uint8_t tmp; + + tmp = data ^ (uint8_t)(*crcAccum &0xff); + tmp ^= (tmp<<4); + *crcAccum = (*crcAccum>>8) ^ (tmp<<8) ^ (tmp <<3) ^ (tmp>>4); +} + +/** + * @brief Initiliaze the buffer for the X.25 CRC + * + * @param crcAccum the 16 bit X.25 CRC + */ +static inline void crc_init(uint16_t* crcAccum) +{ + *crcAccum = X25_INIT_CRC; +} + + +/** + * @brief Calculates the X.25 checksum on a byte buffer + * + * @param pBuffer buffer containing the byte array to hash + * @param length length of the byte array + * @return the checksum over the buffer bytes + **/ +static inline uint16_t crc_calculate(uint8_t* pBuffer, uint16_t length) +{ + uint16_t crcTmp; + crc_init(&crcTmp); + while (length--) { + crc_accumulate(*pBuffer++, &crcTmp); + } + return crcTmp; +} + +/** + * @brief Accumulate the X.25 CRC by adding an array of bytes + * + * The checksum function adds the hash of one char at a time to the + * 16 bit checksum (uint16_t). + * + * @param data new bytes to hash + * @param crcAccum the already accumulated checksum + **/ +static inline void crc_accumulate_buffer(uint16_t *crcAccum, const char *pBuffer, uint8_t length) +{ + const uint8_t *p = (const uint8_t *)pBuffer; + while (length--) { + crc_accumulate(*p++, crcAccum); + } +} + + + + +#endif /* _CHECKSUM_H_ */ + +#ifdef __cplusplus +} +#endif |