void b2ContactManager::Collide()

in Box2D/Dynamics/b2ContactManager.cpp [105:170]
50 lines of code
11 McCabe index (conditional complexity)

void b2ContactManager::Collide()
{
	// Update awake contacts.
	b2Contact* c = m_contactList;
	while (c)
	{
		b2Fixture* fixtureA = c->GetFixtureA();
		b2Fixture* fixtureB = c->GetFixtureB();
		int32 indexA = c->GetChildIndexA();
		int32 indexB = c->GetChildIndexB();
		b2Body* bodyA = fixtureA->GetBody();
		b2Body* bodyB = fixtureB->GetBody();
		 
		// Is this contact flagged for filtering?
		if (c->m_flags & b2Contact::e_filterFlag)
		{
			// Should these bodies collide?
			if (bodyB->ShouldCollide(bodyA) == false)
			{
				b2Contact* cNuke = c;
				c = cNuke->GetNext();
				Destroy(cNuke);
				continue;
			}

			// Check user filtering.
			if (m_contactFilter && m_contactFilter->ShouldCollide(fixtureA, fixtureB) == false)
			{
				b2Contact* cNuke = c;
				c = cNuke->GetNext();
				Destroy(cNuke);
				continue;
			}

			// Clear the filtering flag.
			c->m_flags &= ~b2Contact::e_filterFlag;
		}

		bool activeA = bodyA->IsAwake() && bodyA->m_type != b2_staticBody;
		bool activeB = bodyB->IsAwake() && bodyB->m_type != b2_staticBody;

		// At least one body must be awake and it must be dynamic or kinematic.
		if (activeA == false && activeB == false)
		{
			c = c->GetNext();
			continue;
		}

		int32 proxyIdA = fixtureA->m_proxies[indexA].proxyId;
		int32 proxyIdB = fixtureB->m_proxies[indexB].proxyId;
		bool overlap = m_broadPhase.TestOverlap(proxyIdA, proxyIdB);

		// Here we destroy contacts that cease to overlap in the broad-phase.
		if (overlap == false)
		{
			b2Contact* cNuke = c;
			c = cNuke->GetNext();
			Destroy(cNuke);
			continue;
		}

		// The contact persists.
		c->Update(m_contactListener);
		c = c->GetNext();
	}
}