void b2ContactManager::AddPair()

in Box2D/Dynamics/b2ContactManager.cpp [177:296]
85 lines of code
21 McCabe index (conditional complexity)

void b2ContactManager::AddPair(void* proxyUserDataA, void* proxyUserDataB)
{
	b2FixtureProxy* proxyA = (b2FixtureProxy*)proxyUserDataA;
	b2FixtureProxy* proxyB = (b2FixtureProxy*)proxyUserDataB;

	b2Fixture* fixtureA = proxyA->fixture;
	b2Fixture* fixtureB = proxyB->fixture;

	int32 indexA = proxyA->childIndex;
	int32 indexB = proxyB->childIndex;

	b2Body* bodyA = fixtureA->GetBody();
	b2Body* bodyB = fixtureB->GetBody();

	// Are the fixtures on the same body?
	if (bodyA == bodyB)
	{
		return;
	}

	// TODO_ERIN use a hash table to remove a potential bottleneck when both
	// bodies have a lot of contacts.
	// Does a contact already exist?
	b2ContactEdge* edge = bodyB->GetContactList();
	while (edge)
	{
		if (edge->other == bodyA)
		{
			b2Fixture* fA = edge->contact->GetFixtureA();
			b2Fixture* fB = edge->contact->GetFixtureB();
			int32 iA = edge->contact->GetChildIndexA();
			int32 iB = edge->contact->GetChildIndexB();

			if (fA == fixtureA && fB == fixtureB && iA == indexA && iB == indexB)
			{
				// A contact already exists.
				return;
			}

			if (fA == fixtureB && fB == fixtureA && iA == indexB && iB == indexA)
			{
				// A contact already exists.
				return;
			}
		}

		edge = edge->next;
	}

	// Does a joint override collision? Is at least one body dynamic?
	if (bodyB->ShouldCollide(bodyA) == false)
	{
		return;
	}

	// Check user filtering.
	if (m_contactFilter && m_contactFilter->ShouldCollide(fixtureA, fixtureB) == false)
	{
		return;
	}

	// Call the factory.
	b2Contact* c = b2Contact::Create(fixtureA, indexA, fixtureB, indexB, m_allocator);
	if (c == NULL)
	{
		return;
	}

	// Contact creation may swap fixtures.
	fixtureA = c->GetFixtureA();
	fixtureB = c->GetFixtureB();
	indexA = c->GetChildIndexA();
	indexB = c->GetChildIndexB();
	bodyA = fixtureA->GetBody();
	bodyB = fixtureB->GetBody();

	// Insert into the world.
	c->m_prev = NULL;
	c->m_next = m_contactList;
	if (m_contactList != NULL)
	{
		m_contactList->m_prev = c;
	}
	m_contactList = c;

	// Connect to island graph.

	// Connect to body A
	c->m_nodeA.contact = c;
	c->m_nodeA.other = bodyB;

	c->m_nodeA.prev = NULL;
	c->m_nodeA.next = bodyA->m_contactList;
	if (bodyA->m_contactList != NULL)
	{
		bodyA->m_contactList->prev = &c->m_nodeA;
	}
	bodyA->m_contactList = &c->m_nodeA;

	// Connect to body B
	c->m_nodeB.contact = c;
	c->m_nodeB.other = bodyA;

	c->m_nodeB.prev = NULL;
	c->m_nodeB.next = bodyB->m_contactList;
	if (bodyB->m_contactList != NULL)
	{
		bodyB->m_contactList->prev = &c->m_nodeB;
	}
	bodyB->m_contactList = &c->m_nodeB;

	// Wake up the bodies
	if (fixtureA->IsSensor() == false && fixtureB->IsSensor() == false)
	{
		bodyA->SetAwake(true);
		bodyB->SetAwake(true);
	}

	++m_contactCount;
}