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#ifdef __cplusplus
extern "C" {
#endif
#ifndef _CHECKSUM_H_
#define _CHECKSUM_H_
/**
*
* CALCULATE THE CHECKSUM
*
*/
#define X25_INIT_CRC 0xffff
#define X25_VALIDATE_CRC 0xf0b8
#ifndef HAVE_CRC_ACCUMULATE
/**
* @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);
}
#endif
/**
* @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(const 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, uint16_t length)
{
const uint8_t *p = (const uint8_t *)pBuffer;
while (length--) {
crc_accumulate(*p++, crcAccum);
}
}
#endif /* _CHECKSUM_H_ */
#ifdef __cplusplus
}
#endif
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