// aoosp_crc.cpp - computes CRC for OSP telegrams
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#include <aoosp_crc.h> // own API


/*!
    @brief  Computes the OSP CRC for a sequence of bytes.
    @param  buf
            A pointer to a sequence of bytes.
    @param  size
            Number of bytes of buf to compute the CRC for.
    @return The OSP CRC.
    @note   Implemented via table lookup.
*/
uint8_t aoosp_crc(const uint8_t * buf, int size) {
  static const uint8_t table[256] = { 
    0x00, 0x2F, 0x5E, 0x71, 0xBC, 0x93, 0xE2, 0xCD, 0x57, 0x78, 0x09, 0x26, 0xEB, 0xC4, 0xB5, 0x9A, 
    0xAE, 0x81, 0xF0, 0xDF, 0x12, 0x3D, 0x4C, 0x63, 0xF9, 0xD6, 0xA7, 0x88, 0x45, 0x6A, 0x1B, 0x34, 
    0x73, 0x5C, 0x2D, 0x02, 0xCF, 0xE0, 0x91, 0xBE, 0x24, 0x0B, 0x7A, 0x55, 0x98, 0xB7, 0xC6, 0xE9,
    0xDD, 0xF2, 0x83, 0xAC, 0x61, 0x4E, 0x3F, 0x10, 0x8A, 0xA5, 0xD4, 0xFB, 0x36, 0x19, 0x68, 0x47, 
    0xE6, 0xC9, 0xB8, 0x97, 0x5A, 0x75, 0x04, 0x2B, 0xB1, 0x9E, 0xEF, 0xC0, 0x0D, 0x22, 0x53, 0x7C, 
    0x48, 0x67, 0x16, 0x39, 0xF4, 0xDB, 0xAA, 0x85, 0x1F, 0x30, 0x41, 0x6E, 0xA3, 0x8C, 0xFD, 0xD2,
    0x95, 0xBA, 0xCB, 0xE4, 0x29, 0x06, 0x77, 0x58, 0xC2, 0xED, 0x9C, 0xB3, 0x7E, 0x51, 0x20, 0x0F, 
    0x3B, 0x14, 0x65, 0x4A, 0x87, 0xA8, 0xD9, 0xF6, 0x6C, 0x43, 0x32, 0x1D, 0xD0, 0xFF, 0x8E, 0xA1, 
    0xE3, 0xCC, 0xBD, 0x92, 0x5F, 0x70, 0x01, 0x2E, 0xB4, 0x9B, 0xEA, 0xC5, 0x08, 0x27, 0x56, 0x79,
    0x4D, 0x62, 0x13, 0x3C, 0xF1, 0xDE, 0xAF, 0x80, 0x1A, 0x35, 0x44, 0x6B, 0xA6, 0x89, 0xF8, 0xD7, 
    0x90, 0xBF, 0xCE, 0xE1, 0x2C, 0x03, 0x72, 0x5D, 0xC7, 0xE8, 0x99, 0xB6, 0x7B, 0x54, 0x25, 0x0A, 
    0x3E, 0x11, 0x60, 0x4F, 0x82, 0xAD, 0xDC, 0xF3, 0x69, 0x46, 0x37, 0x18, 0xD5, 0xFA, 0x8B, 0xA4,
    0x05, 0x2A, 0x5B, 0x74, 0xB9, 0x96, 0xE7, 0xC8, 0x52, 0x7D, 0x0C, 0x23, 0xEE, 0xC1, 0xB0, 0x9F, 
    0xAB, 0x84, 0xF5, 0xDA, 0x17, 0x38, 0x49, 0x66, 0xFC, 0xD3, 0xA2, 0x8D, 0x40, 0x6F, 0x1E, 0x31, 
    0x76, 0x59, 0x28, 0x07, 0xCA, 0xE5, 0x94, 0xBB, 0x21, 0x0E, 0x7F, 0x50, 0x9D, 0xB2, 0xC3, 0xEC,
    0xD8, 0xF7, 0x86, 0xA9, 0x64, 0x4B, 0x3A, 0x15, 0x8F, 0xA0, 0xD1, 0xFE, 0x33, 0x1C, 0x6D, 0x42, 
  };
  uint8_t crc = 0;
  for( int i=0; i<size; i++ ) {
    crc ^= *buf++;
    crc = table[crc];
  }
  return crc;
}

