| 1 | #ifdef __cplusplus
|
|---|
| 2 | extern "C" {
|
|---|
| 3 | #endif
|
|---|
| 4 |
|
|---|
| 5 | #ifndef _CHECKSUM_H_
|
|---|
| 6 | #define _CHECKSUM_H_
|
|---|
| 7 |
|
|---|
| 8 | // Visual Studio versions before 2010 don't have stdint.h, so we just error out.
|
|---|
| 9 | #if (defined _MSC_VER) && (_MSC_VER < 1600)
|
|---|
| 10 | #error "The C-MAVLink implementation requires Visual Studio 2010 or greater"
|
|---|
| 11 | #endif
|
|---|
| 12 |
|
|---|
| 13 | #include <stdint.h>
|
|---|
| 14 |
|
|---|
| 15 | /**
|
|---|
| 16 | *
|
|---|
| 17 | * CALCULATE THE CHECKSUM
|
|---|
| 18 | *
|
|---|
| 19 | */
|
|---|
| 20 |
|
|---|
| 21 | #define X25_INIT_CRC 0xffff
|
|---|
| 22 | #define X25_VALIDATE_CRC 0xf0b8
|
|---|
| 23 |
|
|---|
| 24 | #ifndef HAVE_CRC_ACCUMULATE
|
|---|
| 25 | /**
|
|---|
| 26 | * @brief Accumulate the X.25 CRC by adding one char at a time.
|
|---|
| 27 | *
|
|---|
| 28 | * The checksum function adds the hash of one char at a time to the
|
|---|
| 29 | * 16 bit checksum (uint16_t).
|
|---|
| 30 | *
|
|---|
| 31 | * @param data new char to hash
|
|---|
| 32 | * @param crcAccum the already accumulated checksum
|
|---|
| 33 | **/
|
|---|
| 34 | static inline void crc_accumulate(uint8_t data, uint16_t *crcAccum)
|
|---|
| 35 | {
|
|---|
| 36 | /*Accumulate one byte of data into the CRC*/
|
|---|
| 37 | uint8_t tmp;
|
|---|
| 38 |
|
|---|
| 39 | tmp = data ^ (uint8_t)(*crcAccum &0xff);
|
|---|
| 40 | tmp ^= (tmp<<4);
|
|---|
| 41 | *crcAccum = (*crcAccum>>8) ^ (tmp<<8) ^ (tmp <<3) ^ (tmp>>4);
|
|---|
| 42 | }
|
|---|
| 43 | #endif
|
|---|
| 44 |
|
|---|
| 45 |
|
|---|
| 46 | /**
|
|---|
| 47 | * @brief Initiliaze the buffer for the X.25 CRC
|
|---|
| 48 | *
|
|---|
| 49 | * @param crcAccum the 16 bit X.25 CRC
|
|---|
| 50 | */
|
|---|
| 51 | static inline void crc_init(uint16_t* crcAccum)
|
|---|
| 52 | {
|
|---|
| 53 | *crcAccum = X25_INIT_CRC;
|
|---|
| 54 | }
|
|---|
| 55 |
|
|---|
| 56 |
|
|---|
| 57 | /**
|
|---|
| 58 | * @brief Calculates the X.25 checksum on a byte buffer
|
|---|
| 59 | *
|
|---|
| 60 | * @param pBuffer buffer containing the byte array to hash
|
|---|
| 61 | * @param length length of the byte array
|
|---|
| 62 | * @return the checksum over the buffer bytes
|
|---|
| 63 | **/
|
|---|
| 64 | static inline uint16_t crc_calculate(const uint8_t* pBuffer, uint16_t length)
|
|---|
| 65 | {
|
|---|
| 66 | uint16_t crcTmp;
|
|---|
| 67 | crc_init(&crcTmp);
|
|---|
| 68 | while (length--) {
|
|---|
| 69 | crc_accumulate(*pBuffer++, &crcTmp);
|
|---|
| 70 | }
|
|---|
| 71 | return crcTmp;
|
|---|
| 72 | }
|
|---|
| 73 |
|
|---|
| 74 |
|
|---|
| 75 | /**
|
|---|
| 76 | * @brief Accumulate the X.25 CRC by adding an array of bytes
|
|---|
| 77 | *
|
|---|
| 78 | * The checksum function adds the hash of one char at a time to the
|
|---|
| 79 | * 16 bit checksum (uint16_t).
|
|---|
| 80 | *
|
|---|
| 81 | * @param data new bytes to hash
|
|---|
| 82 | * @param crcAccum the already accumulated checksum
|
|---|
| 83 | **/
|
|---|
| 84 | static inline void crc_accumulate_buffer(uint16_t *crcAccum, const char *pBuffer, uint16_t length)
|
|---|
| 85 | {
|
|---|
| 86 | const uint8_t *p = (const uint8_t *)pBuffer;
|
|---|
| 87 | while (length--) {
|
|---|
| 88 | crc_accumulate(*p++, crcAccum);
|
|---|
| 89 | }
|
|---|
| 90 | }
|
|---|
| 91 |
|
|---|
| 92 | #endif /* _CHECKSUM_H_ */
|
|---|
| 93 |
|
|---|
| 94 | #ifdef __cplusplus
|
|---|
| 95 | }
|
|---|
| 96 | #endif
|
|---|
