comparing a GUID so I can sort by GUID

Question

what's a nice, fast way to sort a list of GUIDs (as TGuid). i thought i'd just use SysUtils.CompareMem(P1, P2: Pointer; Length: Integer): Boolean; until i realized it returns boolean.

i'd wish for something comparable to CompareText( ) or CompareValue( ) that return integer so it can be used in a sort comparison.

i suppose not many people wish to sort GUIDs...any ideas?

i suppose i could call make some cascading calls to CompareValue( ) on the contents of the TGuid record. my instincts tell me there must be a better way!

thank you!

Answer 1

I do not know Delphi but generally a GUID is a 128-bit hexadecimal string, you can just cast/parse the sub-elements to unsigned (4 * 4-byte or 2*8-byte) integers and then compare them. Once you have that function just apply a standard sort algorithm.

If my answer does not satisfy the RFC of the GUID specification Microsoft uses is presented here, you can probably come up with better ways of sorting extracting the bit-level data in the GUID.

Answer 2

If you're using Delphi 2009 or better, you can use TComparer<TGUID>.Compare(), or the BinaryCompare function it calls, from the Generics.Defaults unit.

Answer 3

Use GUIDToString and do CompareStr on that -- not the fastest option but it works.