Function validateHEXData

RFM69_OTA.cpp:437–469

=================================================================================================================== validateHEXData() - returns length of HEX data bytes if everything is valid returns 0 if any validation failed ===================================================================================================================

//returns 0 if any validation failed
//===================================================================================================================
uint8_t validateHEXData(void* data, uint8_t length)
{
  //assuming 1 byte record length, 2 bytes address, 1 byte record type, N data bytes, 1 CRC byte
  char* input = (char*)data;
  if (length <12 || length%2!=0) return 0; //shortest possible intel data HEX record is 12 bytes
  //Serial.print(F("VAL > ")); Serial.println((char*)input);

  uint8_t checksum=0;
  //check valid HEX data and CRC
  for (uint8_t i=0; i<length;i++)
  {
    if (!((input[i] >=48 && input[i]<=57) || (input[i] >=65 && input[i]<=70))) //0-9,A-F
      return 255;
    if (i%2 && i<length-2) checksum+=BYTEfromHEX(input[i-1], input[i]);
  }
  checksum=(checksum^0xFF)+1;
  
  //TODO : CHECK for address continuity (intel HEX addresses are big endian)

  //Serial.print(F("final CRC:"));Serial.println((uint8_t)checksum, HEX);
  //Serial.print(F("CRC byte:"));Serial.println(BYTEfromHEX(input[length-2], input[length-1]), HEX);

  //check CHECKSUM byte
  if (((uint8_t)checksum) != BYTEfromHEX(input[length-2], input[length-1]))
    return 254;

  uint8_t dataLength = BYTEfromHEX(input[0], input[1]); //length of actual HEX flash data (usually 16bytes)
  //calculate record length
  if (length != dataLength*2 + 10) //add headers and checksum bytes (a total of 10 combined)
    return 253;

  return dataLength; //all validation OK!
}


//===================================================================================================================