CODEWITHSUNDEEP
cembeddedcrc
NickB
NickB

Reputation: 409

What is the use of a defined magic number followed by a CRC

I've been dropped on an existing project where the initial developer is no longer around and I don't have the experience of this guy.

So while revising the code, I've stumbled on a part where I see a defined magic number followed by a CRC.

...
// Fill the structure.
oFactoryParams.u16MagicNumber = PARAMMGR_EEPROM_MAGIC_NUMBER_FACTORY_PARAMS;
...

// Calculate CRC.
oFactoryParams.u16CRC = CRCUtilCompute(sizeof(oFactoryParams) - 2, u16Dummy, (UINT8*)&oFactoryParams);

// Write.
u32NbByte = NEEPROMWrite32Bit(...Some params...)
...

What is the use of this magic number? Is it related to the CRC?

Thank you

Upvotes: 0

Views: 728

Answers (1)

grapes
grapes

Reputation: 8636

Magic numbers are commonly used to assert the type of a passed pointer in languages without RTTI to detect errors, connected with invalid typecasting, especially if parameters are passed as void*.

CRC16 is usually used in legacy communication protocols for validating the data integrity after being sent through serial lines.

So I can image situation your structure is sent directly to socket/tty with send(s, &val, sizeof(val)); and in this case CRC16 could be useful.

So to conclude, these fields could be used for asserts/checks on different levels

Upvotes: 2

Related Questions