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Home » Community » Coffee corner » Map implementation
Re: Map implementation [message #51523 is a reply to message #51522] Tue, 09 April 2019 17:16 Go to previous messageGo to previous message
mirek is currently offline  mirek
Messages: 12020
Registered: November 2005
Ultimate Member
You have accidentally succeeded in attack on used hash mechanism - what you see is result of hash collisions. This is sad and something to deal with, however this would be much harder to achieve with String and quite unlikely to happen with real (aka random) data.

Still it is something I am worried about and will fix properly in the next version. For now, try to replace


inline dword FoldHash(dword h)
{
	return h - 362437 * SwapEndian32(h);
}

inline int& HashBase::Maph(unsigned _hash) const
{
	unsigned h = _hash & ~UNSIGNED_HIBIT;
	return map[mask & FoldHash(h)];
}



(In future, I will make '362437' number random prime, which will likely make this kind of attack impossible).

Mirek

EDIT: Forgot the change in Map.h

[Updated on: Wed, 10 April 2019 00:21]

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