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| 1 | +#pragma once |
| 2 | + |
| 3 | +#if defined(MAVLINK_USE_CXX_NAMESPACE) |
| 4 | +namespace mavlink { |
| 5 | +#elif defined(__cplusplus) |
| 6 | +extern "C" { |
| 7 | +#endif |
| 8 | + |
| 9 | +// Visual Studio versions before 2010 don't have stdint.h, so we just error out. |
| 10 | +#if (defined _MSC_VER) && (_MSC_VER < 1600) |
| 11 | +#error "The C-MAVLink implementation requires Visual Studio 2010 or greater" |
| 12 | +#endif |
| 13 | + |
| 14 | +#include <stdint.h> |
| 15 | + |
| 16 | +/** |
| 17 | + * |
| 18 | + * CALCULATE THE CHECKSUM |
| 19 | + * |
| 20 | + */ |
| 21 | + |
| 22 | +#define X25_INIT_CRC 0xffff |
| 23 | +#define X25_VALIDATE_CRC 0xf0b8 |
| 24 | + |
| 25 | +#ifndef HAVE_CRC_ACCUMULATE |
| 26 | +/** |
| 27 | + * @brief Accumulate the CRC16_MCRF4XX checksum by adding one char at a time. |
| 28 | + * |
| 29 | + * The checksum function adds the hash of one char at a time to the |
| 30 | + * 16 bit checksum (uint16_t). |
| 31 | + * |
| 32 | + * @param data new char to hash |
| 33 | + * @param crcAccum the already accumulated checksum |
| 34 | + **/ |
| 35 | +static inline void crc_accumulate(uint8_t data, uint16_t *crcAccum) |
| 36 | +{ |
| 37 | + /*Accumulate one byte of data into the CRC*/ |
| 38 | + uint8_t tmp; |
| 39 | + |
| 40 | + tmp = data ^ (uint8_t)(*crcAccum &0xff); |
| 41 | + tmp ^= (tmp<<4); |
| 42 | + *crcAccum = (*crcAccum>>8) ^ (tmp<<8) ^ (tmp <<3) ^ (tmp>>4); |
| 43 | +} |
| 44 | +#endif |
| 45 | + |
| 46 | + |
| 47 | +/** |
| 48 | + * @brief Initialize the buffer for the MCRF4XX CRC16 |
| 49 | + * |
| 50 | + * @param crcAccum the 16 bit MCRF4XX CRC16 |
| 51 | + */ |
| 52 | +static inline void crc_init(uint16_t* crcAccum) |
| 53 | +{ |
| 54 | + *crcAccum = X25_INIT_CRC; |
| 55 | +} |
| 56 | + |
| 57 | + |
| 58 | +/** |
| 59 | + * @brief Calculates the CRC16_MCRF4XX checksum on a byte buffer |
| 60 | + * |
| 61 | + * @param pBuffer buffer containing the byte array to hash |
| 62 | + * @param length length of the byte array |
| 63 | + * @return the checksum over the buffer bytes |
| 64 | + **/ |
| 65 | +static inline uint16_t crc_calculate(const uint8_t* pBuffer, uint16_t length) |
| 66 | +{ |
| 67 | + uint16_t crcTmp; |
| 68 | + crc_init(&crcTmp); |
| 69 | + while (length--) { |
| 70 | + crc_accumulate(*pBuffer++, &crcTmp); |
| 71 | + } |
| 72 | + return crcTmp; |
| 73 | +} |
| 74 | + |
| 75 | + |
| 76 | +/** |
| 77 | + * @brief Accumulate the MCRF4XX CRC16 by adding an array of bytes |
| 78 | + * |
| 79 | + * The checksum function adds the hash of one char at a time to the |
| 80 | + * 16 bit checksum (uint16_t). |
| 81 | + * |
| 82 | + * @param data new bytes to hash |
| 83 | + * @param crcAccum the already accumulated checksum |
| 84 | + **/ |
| 85 | +static inline void crc_accumulate_buffer(uint16_t *crcAccum, const char *pBuffer, uint16_t length) |
| 86 | +{ |
| 87 | + const uint8_t *p = (const uint8_t *)pBuffer; |
| 88 | + while (length--) { |
| 89 | + crc_accumulate(*p++, crcAccum); |
| 90 | + } |
| 91 | +} |
| 92 | + |
| 93 | +#if defined(MAVLINK_USE_CXX_NAMESPACE) || defined(__cplusplus) |
| 94 | +} |
| 95 | +#endif |
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