Am 19.04.2021 um 19:05 schrieb Ryan Joseph via fpc-pascal:
I have a question I was just curious about. From what I can tell TFPGMap uses
CompareByte to compare keys of arbitrary type, which is clever but how does
this work for ShortStrings? I have tried to use this method myself and I find
it always fails because short strings have garbage at the end and so even if
you zero out the memory (which is allocated) a short string passed as a
parameter to a function will have garbage and thus fail to compare. Any ideas
how this works for TFPGMap then?
function TFPSMap.BinaryCompareKey(Key1, Key2: Pointer): Integer;
begin
Result := CompareByte(Key1^, Key2^, FKeySize);
end;
If you look at TFPSMap' code you'll see that BinaryCompareKey and
BinaryCompareData are only used in the way of method pointers
OnKeyPtrCompare and OnDataPtrCompare. In TFPGMap<,> these are then set
to compare methods specific to the specialization, most importantly
TFPGMap<,>.KeyCompare if no custom compare function is set.
Regards,
Sven
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