CODEWITHSUNDEEP
debuggingrandomguidundefined-behavior
sharptooth
sharptooth

Reputation: 170489

Is there a way to distinguish a GUID from just a random number?

Being able to distinguish a GUID from random data can be useful when debugging obscure code defects.

On Windows each GUID generated is of version 4 therefore it has '4' as the first half-byte of the third part. So if the 16-byte sequence violtates that rule it is not a version 4 GUID. For example,

567E1ECB-EA1C-42D3-A3ED-87A5D824D167

could be either a version 4 GUID or anything else, but

567E1ECB-EA1C-02D3-A3ED-87A5D824D167 //third section starts with 0, not with 4

is not a version 4 GUID.

What are other signs of a 16-byte memory block being or not being a valid GUID?

Upvotes: 6

Views: 1492

Answers (2)

MSalters
MSalters

Reputation: 179779

Besides GUID version (0100), there's also something called the GUID variant. This will be 2 bits (10) in octet 8. The remaining bits a of v4 GUID are by definition random.

Upvotes: 0

Stuart
Stuart

Reputation: 176

GUID's are hexadecimal, so you could check what characters are included (i.e. 'X', 'Y', etc. are not valid)

Check wikipedia for the definition and you could probably find out more ideas there.

http://en.wikipedia.org/wiki/Globally_Unique_Identifier

Upvotes: 1

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