void b2CollideEdgeAndCircle()

in Box2D/Collision/b2CollideEdge.cpp [27:152]
101 lines of code
11 McCabe index (conditional complexity)

void b2CollideEdgeAndCircle(b2Manifold* manifold,
							const b2EdgeShape* edgeA, const b2Transform& xfA,
							const b2CircleShape* circleB, const b2Transform& xfB)
{
	manifold->pointCount = 0;
	
	// Compute circle in frame of edge
	b2Vec2 Q = b2MulT(xfA, b2Mul(xfB, circleB->m_p));
	
	b2Vec2 A = edgeA->m_vertex1, B = edgeA->m_vertex2;
	b2Vec2 e = B - A;
	
	// Barycentric coordinates
	float32 u = b2Dot(e, B - Q);
	float32 v = b2Dot(e, Q - A);
	
	float32 radius = edgeA->m_radius + circleB->m_radius;
	
	b2ContactFeature cf;
	cf.indexB = 0;
	cf.typeB = b2ContactFeature::e_vertex;
	
	// Region A
	if (v <= 0.0f)
	{
		b2Vec2 P = A;
		b2Vec2 d = Q - P;
		float32 dd = b2Dot(d, d);
		if (dd > radius * radius)
		{
			return;
		}
		
		// Is there an edge connected to A?
		if (edgeA->m_hasVertex0)
		{
			b2Vec2 A1 = edgeA->m_vertex0;
			b2Vec2 B1 = A;
			b2Vec2 e1 = B1 - A1;
			float32 u1 = b2Dot(e1, B1 - Q);
			
			// Is the circle in Region AB of the previous edge?
			if (u1 > 0.0f)
			{
				return;
			}
		}
		
		cf.indexA = 0;
		cf.typeA = b2ContactFeature::e_vertex;
		manifold->pointCount = 1;
		manifold->type = b2Manifold::e_circles;
		manifold->localNormal.SetZero();
		manifold->localPoint = P;
		manifold->points[0].id.key = 0;
		manifold->points[0].id.cf = cf;
		manifold->points[0].localPoint = circleB->m_p;
		return;
	}
	
	// Region B
	if (u <= 0.0f)
	{
		b2Vec2 P = B;
		b2Vec2 d = Q - P;
		float32 dd = b2Dot(d, d);
		if (dd > radius * radius)
		{
			return;
		}
		
		// Is there an edge connected to B?
		if (edgeA->m_hasVertex3)
		{
			b2Vec2 B2 = edgeA->m_vertex3;
			b2Vec2 A2 = B;
			b2Vec2 e2 = B2 - A2;
			float32 v2 = b2Dot(e2, Q - A2);
			
			// Is the circle in Region AB of the next edge?
			if (v2 > 0.0f)
			{
				return;
			}
		}
		
		cf.indexA = 1;
		cf.typeA = b2ContactFeature::e_vertex;
		manifold->pointCount = 1;
		manifold->type = b2Manifold::e_circles;
		manifold->localNormal.SetZero();
		manifold->localPoint = P;
		manifold->points[0].id.key = 0;
		manifold->points[0].id.cf = cf;
		manifold->points[0].localPoint = circleB->m_p;
		return;
	}
	
	// Region AB
	float32 den = b2Dot(e, e);
	b2Assert(den > 0.0f);
	b2Vec2 P = (1.0f / den) * (u * A + v * B);
	b2Vec2 d = Q - P;
	float32 dd = b2Dot(d, d);
	if (dd > radius * radius)
	{
		return;
	}
	
	b2Vec2 n(-e.y, e.x);
	if (b2Dot(n, Q - A) < 0.0f)
	{
		n.Set(-n.x, -n.y);
	}
	n.Normalize();
	
	cf.indexA = 0;
	cf.typeA = b2ContactFeature::e_face;
	manifold->pointCount = 1;
	manifold->type = b2Manifold::e_faceA;
	manifold->localNormal = n;
	manifold->localPoint = A;
	manifold->points[0].id.key = 0;
	manifold->points[0].id.cf = cf;
	manifold->points[0].localPoint = circleB->m_p;
}