int correlation(const String& a, const String& b, int* aHistogram, int* bHistogram)
{
	int res=0;
	const char* A = a.Begin();
	const char* B = b.Begin();

	const int Al = a.GetLength();
	const int Bl = b.GetLength();
	const int deltaL = Al - Bl;

	int As, Bs, intersectLength;
	int subRes;

	int matchPatternMinLength = max(2, min(b.GetLength(), a.GetLength())/3);

	// init de l'histogramme
	for (int c = 0; c<Al; c++)
	{
		aHistogram[c] = 0;
	}

	for (int c = 0; c<Bl; c++)
	{
		bHistogram[c] = 0;
	}

	for (int offset = (matchPatternMinLength-Bl); offset <= (Al-matchPatternMinLength); offset++ )
	{
		// determination des bornes
		if (offset < 0)
		{
			As = 0;
			Bs = -offset;
			if (offset < deltaL) intersectLength = offset + Bl;
			else                 intersectLength = Al;
		}
		else
		{
			As = offset;
			Bs = 0;
			intersectLength = Al - offset;
			if (offset <= deltaL) intersectLength = Bl;
			else                  intersectLength = Al-offset;
		}

		subRes = 0;
		for (int c = 0; c<intersectLength; c++)
		{
			if( A[As+c] == B[Bs+c]) ++subRes;
		}
		if (subRes >= matchPatternMinLength)
		{
			res += subRes;

			// creation de l'histogramme
			for (int c = 0; c<intersectLength; c++)
			{
				if( A[As+c] == B[Bs+c])
				{
					aHistogram[As+c] += subRes;
					bHistogram[Bs+c] += subRes;
				}
			}
		}
	}

	// prise en compte du nbr de caracteres
	if ( deltaL > 0 )
	{
		res -= deltaL;
	}
	else
	{
		res += deltaL;
	}
	return res;
}