void b2World::Step()

in Box2D/Dynamics/b2World.cpp [897:963]
51 lines of code
9 McCabe index (conditional complexity)

void b2World::Step(float32 dt, int32 velocityIterations, int32 positionIterations)
{
	b2Timer stepTimer;

	// If new fixtures were added, we need to find the new contacts.
	if (m_flags & e_newFixture)
	{
		m_contactManager.FindNewContacts();
		m_flags &= ~e_newFixture;
	}

	m_flags |= e_locked;

	b2TimeStep step;
	step.dt = dt;
	step.velocityIterations	= velocityIterations;
	step.positionIterations = positionIterations;
	if (dt > 0.0f)
	{
		step.inv_dt = 1.0f / dt;
	}
	else
	{
		step.inv_dt = 0.0f;
	}

	step.dtRatio = m_inv_dt0 * dt;

	step.warmStarting = m_warmStarting;
	
	// Update contacts. This is where some contacts are destroyed.
	{
		b2Timer timer;
		m_contactManager.Collide();
		m_profile.collide = timer.GetMilliseconds();
	}

	// Integrate velocities, solve velocity constraints, and integrate positions.
	if (m_stepComplete && step.dt > 0.0f)
	{
		b2Timer timer;
		Solve(step);
		m_profile.solve = timer.GetMilliseconds();
	}

	// Handle TOI events.
	if (m_continuousPhysics && step.dt > 0.0f)
	{
		b2Timer timer;
		SolveTOI(step);
		m_profile.solveTOI = timer.GetMilliseconds();
	}

	if (step.dt > 0.0f)
	{
		m_inv_dt0 = step.inv_dt;
	}

	if (m_flags & e_clearForces)
	{
		ClearForces();
	}

	m_flags &= ~e_locked;

	m_profile.step = stepTimer.GetMilliseconds();
}