void b2Body::ResetMassData()

in Box2D/Dynamics/b2Body.cpp [281:351]
54 lines of code
8 McCabe index (conditional complexity)

void b2Body::ResetMassData()
{
	// Compute mass data from shapes. Each shape has its own density.
	m_mass = 0.0f;
	m_invMass = 0.0f;
	m_I = 0.0f;
	m_invI = 0.0f;
	m_sweep.localCenter.SetZero();

	// Static and kinematic bodies have zero mass.
	if (m_type == b2_staticBody || m_type == b2_kinematicBody)
	{
		m_sweep.c0 = m_xf.p;
		m_sweep.c = m_xf.p;
		m_sweep.a0 = m_sweep.a;
		return;
	}

	b2Assert(m_type == b2_dynamicBody);

	// Accumulate mass over all fixtures.
	b2Vec2 localCenter = b2Vec2_zero;
	for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
	{
		if (f->m_density == 0.0f)
		{
			continue;
		}

		b2MassData massData;
		f->GetMassData(&massData);
		m_mass += massData.mass;
		localCenter += massData.mass * massData.center;
		m_I += massData.I;
	}

	// Compute center of mass.
	if (m_mass > 0.0f)
	{
		m_invMass = 1.0f / m_mass;
		localCenter *= m_invMass;
	}
	else
	{
		// Force all dynamic bodies to have a positive mass.
		m_mass = 1.0f;
		m_invMass = 1.0f;
	}

	if (m_I > 0.0f && (m_flags & e_fixedRotationFlag) == 0)
	{
		// Center the inertia about the center of mass.
		m_I -= m_mass * b2Dot(localCenter, localCenter);
		b2Assert(m_I > 0.0f);
		m_invI = 1.0f / m_I;

	}
	else
	{
		m_I = 0.0f;
		m_invI = 0.0f;
	}

	// Move center of mass.
	b2Vec2 oldCenter = m_sweep.c;
	m_sweep.localCenter = localCenter;
	m_sweep.c0 = m_sweep.c = b2Mul(m_xf, m_sweep.localCenter);

	// Update center of mass velocity.
	m_linearVelocity += b2Cross(m_angularVelocity, m_sweep.c - oldCenter);
}