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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1702 | - | 1 | #ifdef __cplusplus |
| 2 | extern "C" { |
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| 3 | #endif |
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| 4 | |||
| 5 | #ifndef _CHECKSUM_H_ |
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| 6 | #define _CHECKSUM_H_ |
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| 7 | |||
| 8 | |||
| 9 | /** |
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| 10 | * |
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| 11 | * CALCULATE THE CHECKSUM |
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| 12 | * |
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| 13 | */ |
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| 14 | |||
| 15 | #define X25_INIT_CRC 0xffff |
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| 16 | #define X25_VALIDATE_CRC 0xf0b8 |
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| 17 | |||
| 18 | /** |
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| 19 | * @brief Accumulate the X.25 CRC by adding one char at a time. |
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| 20 | * |
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| 21 | * The checksum function adds the hash of one char at a time to the |
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| 22 | * 16 bit checksum (uint16_t). |
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| 23 | * |
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| 24 | * @param data new char to hash |
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| 25 | * @param crcAccum the already accumulated checksum |
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| 26 | **/ |
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| 27 | static inline void crc_accumulate(uint8_t data, uint16_t *crcAccum) |
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| 28 | { |
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| 29 | /*Accumulate one byte of data into the CRC*/ |
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| 30 | uint8_t tmp; |
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| 31 | |||
| 32 | tmp = data ^ (uint8_t)(*crcAccum &0xff); |
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| 33 | tmp ^= (tmp<<4); |
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| 34 | *crcAccum = (*crcAccum>>8) ^ (tmp<<8) ^ (tmp <<3) ^ (tmp>>4); |
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| 35 | } |
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| 36 | |||
| 37 | /** |
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| 38 | * @brief Initiliaze the buffer for the X.25 CRC |
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| 39 | * |
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| 40 | * @param crcAccum the 16 bit X.25 CRC |
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| 41 | */ |
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| 42 | static inline void crc_init(uint16_t* crcAccum) |
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| 43 | { |
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| 44 | *crcAccum = X25_INIT_CRC; |
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| 45 | } |
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| 46 | |||
| 47 | |||
| 48 | /** |
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| 49 | * @brief Calculates the X.25 checksum on a byte buffer |
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| 50 | * |
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| 51 | * @param pBuffer buffer containing the byte array to hash |
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| 52 | * @param length length of the byte array |
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| 53 | * @return the checksum over the buffer bytes |
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| 54 | **/ |
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| 55 | static inline uint16_t crc_calculate(const uint8_t* pBuffer, uint16_t length) |
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| 56 | { |
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| 57 | uint16_t crcTmp; |
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| 58 | crc_init(&crcTmp); |
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| 59 | while (length--) { |
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| 60 | crc_accumulate(*pBuffer++, &crcTmp); |
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| 61 | } |
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| 62 | return crcTmp; |
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| 63 | } |
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| 64 | |||
| 65 | /** |
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| 66 | * @brief Accumulate the X.25 CRC by adding an array of bytes |
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| 67 | * |
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| 68 | * The checksum function adds the hash of one char at a time to the |
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| 69 | * 16 bit checksum (uint16_t). |
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| 70 | * |
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| 71 | * @param data new bytes to hash |
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| 72 | * @param crcAccum the already accumulated checksum |
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| 73 | **/ |
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| 74 | static inline void crc_accumulate_buffer(uint16_t *crcAccum, const char *pBuffer, uint8_t length) |
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| 75 | { |
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| 76 | const uint8_t *p = (const uint8_t *)pBuffer; |
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| 77 | while (length--) { |
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| 78 | crc_accumulate(*p++, crcAccum); |
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| 79 | } |
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| 80 | } |
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| 81 | |||
| 82 | |||
| 83 | |||
| 84 | |||
| 85 | #endif /* _CHECKSUM_H_ */ |
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| 86 | |||
| 87 | #ifdef __cplusplus |
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| 88 | } |
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| 89 | #endif |